[HN Gopher] Goldman Sachs invests $250M in compressed air energy...
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       Goldman Sachs invests $250M in compressed air energy storage
        
       Author : rwmj
       Score  : 232 points
       Date   : 2022-01-12 14:55 UTC (8 hours ago)
        
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 (TXT) w3m dump (www.canarymedia.com)
        
       | treyfitty wrote:
       | I remember reading this article a few years ago that Goldman
       | Sachs. It's paywalled but the basics was that GS stores energy
       | during the night, and uses the energy during the day. I thought
       | it was neat, but they're obviously not new to this concept.
       | 
       | https://www.bloomberg.com/news/articles/2014-08-01/goldman-s...
        
       | reacharavindh wrote:
       | I'm not an electrical engineer. But, thinking about the power
       | storage/retrieval problem with a computer engineer's lens, I can
       | draw a parallel to data storage/retrieval.
       | 
       | L1/L2/L3 caches - expensive, small, but fast.
       | 
       | RAM - mid tier, still fast, bigger than cache, less expensive
       | than cache, but limited in capacity compared to disk/flash based
       | storage.
       | 
       | SSDs...
       | 
       | Disks....
       | 
       | You get the point.
       | 
       | Would it be the same with the grid?
       | 
       | Several power sources - nuclear, solar, wind, hydro, hopefully
       | not coal and gas.
       | 
       | Banks of Lithium batteries acting as first level(efficient and
       | immediate but limited capacity storage).
       | 
       | Whatever excess is directed to longer term, non immediate storage
       | - pump up water to generate power later, molten salt, air
       | compression etc.
       | 
       | Even more left? - spin up production of time insensitive
       | materials that would be used anyway later - sea water
       | desalination plants, green hydrogen generation, sewage treatment
       | etc.
       | 
       | At large scale such tiered ecosystems would be very cool and
       | super useful.
        
         | trompetenaccoun wrote:
         | Sounds trivial enough, now someone just has to built it all.
         | 
         | Jokes aside though everything has pros and cons. For storing
         | large amounts of energy from the grid, are you sure lithium
         | batteries make sense? Take a look at this, it's not a
         | scientific article but it gives you a basic overview of the
         | problems we'd face when storing energy in lithium batteries at
         | scale: https://www.renewableenergyworld.com/storage/lithium-or-
         | vana...
         | 
         | And that isn't to say that flow batteries are the ultimate
         | solution either, we will have to do better because it's still
         | very expensive.
        
           | epistasis wrote:
           | That article is from 2014. Since then we have deployed dozens
           | of GWh of grid storage. There have been a few small fires,
           | but otherwise it's worked out really well. Lithium ion on the
           | grid is nearly doubling every year, and in places like Texas.
           | I'm having trouble finding a recent article, but this one
           | from 2020 has 3x as many battery GW thank gas GW in the
           | interconnection queue:
           | 
           | https://pv-magazine-usa.com/2020/09/08/interconnection-
           | queue...
           | 
           | And if you check out RV and boat forums, you'll find that
           | small scale lithium ion batteries plus solar are enabling a
           | huge change in power for these mobile applications, because
           | it's just damn cheap these days.
        
         | loceng wrote:
         | I've wondered if putting an compressed air energy storage
         | system under certain types of buildings would work. Any
         | thoughts on that? E.g. Apple's Ring HQ is already on a floating
         | system to counter earthquakes, so why not add a layer of air?
         | Unnecessary? Much more expensive than other options? Else?
        
         | beders wrote:
         | Stanford researcher Mark Z. Jacobson makes a similar case but
         | with renewables and storage only:
         | https://web.stanford.edu/group/efmh/jacobson/WWSBook/WWSBook...
        
         | stcredzero wrote:
         | Look into natural gas trading and scheduling. There's already
         | an entire body of knowledge around storing energy, and
         | sophisticated automated contracts, financial instruments, laws,
         | and regulations. "Pools" are just energy storage, and the same
         | geologic features used for those facilities could be used for
         | compressed air storage.
         | 
         | (EDIT: I used to do this software!)
        
       | ccvannorman wrote:
       | I knew Danielle Fong from Lightsail Energy, folded in 2016, and
       | at that time compressed air seemed like a great solution
       | especially for LatAm that needed robust low cost batteries for
       | critical infrastructure (like hospitals) on an unreliable power
       | grid. https://en.wikipedia.org/wiki/Danielle_Fong
       | 
       | Would be great to see this technology reach maturity!
        
         | KennyBlanken wrote:
         | That wikipedia page answers everything you need to know about
         | compressed air energy storage.
         | 
         | In 2018, the tech couldn't compete against lithium ion, and the
         | price of lithium ion continues to fall 10-20% per year.
         | 
         | Compressed air and that concrete-block-stacking nonsense that
         | keeps getting press are just magnets for uneducated investors.
        
           | PaulDavisThe1st wrote:
           | That wikipedia page says:
           | 
           | > Compared to traditional batteries, CAES systems can store
           | energy for longer periods of time and have less upkeep.
           | 
           | Sometimes the cost per MW/hr or equivalent is not the only
           | metric worth thinking about.
        
             | tradesurplus wrote:
             | Plus, always a good idea to hedge: against lithium
             | shortages / gouging and battery supply chain disruptions.
        
         | mikeyouse wrote:
         | She's on HN, curious what her thoughts are:
         | https://news.ycombinator.com/user?id=DaniFong
        
           | DaniFong wrote:
           | https://twitter.com/DanielleFong/status/1481339424730497025?.
           | ..
        
       | [deleted]
        
         | jrockway wrote:
         | Would energy storage not be a good use of that money? Society
         | is facing a large problem: climate change. One way to reduce
         | the impact of climate change is to use renewable energy like
         | solar and wind. Solar and wind have a big problem; they can't
         | be turned on and off. That means to displace fossil fuels, we
         | need to store energy when it's sunny and windy, and release
         | that energy when it's not. Hence, things like compressed air
         | energy storage. This is the kind of technology that can prevent
         | entire cities from disappearing over the next 100 years. Seems
         | pretty valuable to me.
        
           | thomaslangston wrote:
           | Small nitpick. Wind can be turned off. The turbines can be
           | equipped with brakes to stop power generation in case of
           | oversupply, in addition to other uses.
        
             | jrockway wrote:
             | I guess turning it on is where the problem comes from.
        
       | Melatonic wrote:
       | I think this is a great idea if you have systems that also use
       | compressed air to function. If you need to convert compressed air
       | to electricity the inherent losses in that conversion seem like
       | they just would not be worth it as battery tech increases.
       | 
       | Would love to see DC to DC grids become a thing again and it
       | looks like they may - crazy to think that SF still has a fully
       | operating DC grid powering all kinds of stuff.
        
       | eMGm4D0zgUAVXc7 wrote:
       | What is the expected efficiency of this?
        
         | rikkipitt wrote:
         | I too was wondering that as the ideal gas law states that PV =
         | nRT. When you compress a gas it gets hotter, conversely,
         | allowing it to decompress cools it. I assume they store the
         | heat energy...
         | 
         | https://en.wikipedia.org/wiki/Compressed-air_energy_storage
        
           | Mvandenbergh wrote:
           | Yes, their website says they have a thermal store.
        
             | mirekrusin wrote:
             | They should do free ice maker on the other end.
        
         | dragontamer wrote:
         | CAES has lower efficiency, probably closer to 70% and only if
         | you use something to reheat the air. (Compressed air loses
         | temperature and needs an external source of heat to restore it
         | to full volume)
         | 
         | Even if you use natural gas as a reheating element, the
         | compressed air stores a significant amount of energy and is
         | doing the majority of the work.
        
         | konschubert wrote:
         | What matters is efficiency per dollar:
         | 
         | Efficiency / cost
         | 
         | I am worried that the cost is the driving factor here...
        
           | EricE wrote:
           | If you ignore efficiency then you stop making a profit pretty
           | quickly. You can solely focus all you want on cost; sooner or
           | later efficiency will make you pay.
           | 
           | Goldman wouldn't be making that kind of an investment if they
           | didn't have a handle on both parts of the equation. Indeed
           | efficiency (dealing with losses from seepage) have been the
           | nut that hasn't been cracked with compressed air storage;
           | these guys seem to have an economical (efficient) way to deal
           | with that problem. If true, then they really are worthy of
           | Goldman's investment.
        
       | terpimost wrote:
       | Interesting, I guess the water freeze isn't a problem in those
       | places
        
         | RyEgswuCsn wrote:
         | I was wondering the same. Although they can somewhat mitigate
         | that by adding some antifreeze additives to the water perhaps?
        
       | nemacol wrote:
       | I would like more detail on the "Thermal management system" and
       | how long it could store the heat it captures.
       | 
       | One of the benefits they touting is "Long duration energy
       | storage" I would think the limiting factor would be the ability
       | of the thermal management system to retain the energy it captured
       | to reheat the compressed air. Am I thinking about this correctly?
        
         | danans wrote:
         | > One of the benefits they touting is "Long duration energy
         | storage"
         | 
         | According to their marketing video [1] "Long duration" is
         | relative to current lithium ion battery-based storage. So their
         | system can store energy up to 24 hours vs a few hours for
         | batteries.
         | 
         | For even longer term storage (weeks, months, seasons), some
         | time of chemical storage will be needed. Currently, both
         | hydrogen electrolysis and ammonia synthesis [2] are being
         | explored for that.
         | 
         | 1. https://youtu.be/cOWjwwKSR78?t=136
         | 
         | 2. https://www.youtube.com/watch?v=5Y_2Z_VwFNc
        
         | themanmaran wrote:
         | On that note do you have a good explanation for why the air
         | needs to be reheated? I didn't quite understand that from the
         | video.
        
           | tristor wrote:
           | Air pressure is strongly correlated to temperature. Cooling
           | the air after compression reduces pumping effort during
           | storage, reheating it increases turbine head pressure during
           | generation.
        
             | usrusr wrote:
             | In other words: gas compression storage suffers from
             | temperature losses. The compressed gas is hot, the heat
             | dissipates from storage and that energy won't be coming
             | back.
             | 
             | But if you extract that heat during compression you can put
             | in a separate storage, one that is much easier to insulate
             | than the compression tanks, and "mix it back in" during
             | recompression, avoiding a large part of those losses.
        
               | tristor wrote:
               | > In other words: gas compression storage suffers from
               | temperature losses.
               | 
               | Yes, and you can also compress air further when it's
               | cooled (this is why there is an intercooler on
               | turbocharged cars, as an example), this means your
               | density per volume of storage is higher at a given
               | pressure.
               | 
               | The reality though is that this is likely less efficient
               | than many other storage mechanisms. Additionally, this
               | may require some sort of additional energy input for
               | reheating if the heat storage is not capable of holding
               | long enough to fully reheat the air on release to get the
               | highest turbine efficiency.
        
           | nemacol wrote:
           | Warm air takes up more space. If you cool it before pumping
           | it into the ground you will not waste time/energy. If you
           | pump warm air down it will lose heat into the ground and
           | shrink and you would lose capacity - pumping that last x% the
           | tanks will be fuller until they cool down.
           | 
           | You warm up the air on the way out to expand it and you get
           | more air to spin the turbine. More bang for your buck.
           | 
           | I believe is the thinking.
        
             | danans wrote:
             | > Warm air takes up more space. If you cool it before
             | pumping it into the ground you will not waste time/energy.
             | 
             | The real masterstroke here might then be to put this system
             | in an area with large diurnal temp changes like the desert,
             | then charge this system with cool night air, and then
             | reheat it and generate electricity during the day with warm
             | daytime air. Heat pumps could be used to nudge the temp on
             | either end into it's optimal range.
             | 
             | It then becomes a solar thermal hybrid compressed air
             | energy storage.
             | 
             | This could pair well with renewables that are more
             | available at night like onshore wind.
        
               | samstave wrote:
               | Many years ago I was doing shrooms in the Nevada desert
               | -- and the epiphany I had was that the desert, and the
               | caves all around and throughout the deserts served as
               | "the lungs of the earth" -- they would heat and cool and
               | would suck air in and out based on this...
               | 
               | I was 17 at the time, and I have been into some of the
               | most incredible caves - the best in Ganung Mulu National
               | Park in Borneo Malaysia...
               | 
               | As the rains flowed out and carried the guano from 5
               | million bats into the forest to fertilize it...
               | 
               | And then I realized it wasnt just the desert - it was the
               | caves...
               | 
               | Caves (giant ones) are really important for planet
               | health.
        
         | usrusr wrote:
         | To the best of my knowledge that thinking is spot on.
         | 
         | A possible component that might be missing (in the thinking
         | and/or in the proposed implementation): the stored heat could
         | also be utilised separately if needed, so if you have an
         | intermittent heat consumer and an intermittent electricity
         | consumer you could consume the heat first, then leave the
         | remaining compression energy (what you could recover without
         | reheating) "forever". Bonus points if you also happen to have a
         | coolant consumer to benefit from the temperature delta caused
         | heat loss or premature heat consumption.
        
           | samstave wrote:
           | After seeing videos of lava pouring into the ocean I have
           | fantasized about a power generation system:
           | 
           | Artificial geo-thermal power gen:
           | 
           | Dig a deep enough hole but near the ocean, and let ocean
           | water pour into the hole that gets close enough to magma such
           | that the magma creates a steam blast back out a tube with a
           | bunch of turbines to spin.
        
             | usrusr wrote:
             | Heh, and you'd get a molten salt heat storage unit for
             | free. Because if you condense that steam you have solved
             | desalination as well.
             | 
             | CEO Nwabudike Morgan likes this (reference to Sid Meier's
             | Alpha Centauri in case you were wondering)
        
       | jl6 wrote:
       | I think the video said the system runs a cycle within a period of
       | around 24 hours. What would it take to store energy in compressed
       | air for ~6 months? This is what high-latitude dark-winter
       | countries need: the ability to over-generate in the summer and
       | draw down on stored energy in the winter.
        
         | marvin wrote:
         | Pumped hydroelectric storage is an obvious choice for the
         | countries that have the geography, in effect meaning that most
         | of the infrastructure for doing it is already in place.
         | Hydroelectric reservoirs allow storing energy more or less
         | indefinitely.
         | 
         | Of course, the capacity will rarely have been dimensioned for
         | keeping 6 months of usage on hand, but combining pumped storage
         | with over-provisioned wind energy would allow for living
         | through months of unfavorable sun, rain or wind conditions.
        
       | axg11 wrote:
       | Does this technology only work in select places or are
       | underground caverns fairly commonplace?
        
         | nkurz wrote:
         | Appropriate natural caverns do exist, but are not common. One
         | of the main differentiating factor between this approach and
         | others is that they drill a man-made borehole rather than
         | depending on finding a pre-existing cavern.
        
           | throwawayboise wrote:
           | Near where I live there is a large underground natural gas
           | storage field using natural caverns.
        
       | nabla9 wrote:
       | Just cheeked some levelized utility scale costs for the US:
       | 
       | Advanced Nuclear is of $72/MWh.
       | 
       | Wind onshore $30/Mwh
       | 
       | Solar photovoltaic (PV) $30/Mwh
       | 
       | Lithium-ion battery storage is roughly $180/Mwh.
       | 
       | At the moment, if you want to provide baseload better than
       | nuclear using renewables, the cost must of storage must not
       | exceed $30-$40/Mwh.
       | 
       | (grid baseload is the minimum level of demand on an electrical
       | grid over a span of time, something unvarying power plants are
       | best suited for. Renewables require storage and advanced grid to
       | provide baseload.)
        
       | robomartin wrote:
       | Based on my reading, these systems are, at best, in the order of
       | 60% efficient. To state the obvious, this means that fully 40% of
       | the energy they pull from the grid will be wasted. Burned. Never
       | to be recovered. How is that a good idea?
       | 
       | Solar? Well, solar isn't free energy. What's the comparison to
       | grid scale batteries for storage? That process is far more
       | favorable, with efficiency exceeding 80%.
       | 
       | I have to admit not understanding how this kind of an investment
       | happens. I don't see this as viable technology at scale. We are
       | far better off building nuclear power plants (talk about dense
       | energy storage!).
       | 
       | Here's a good article on pumped thermal energy storage systems
       | and how they compare to alternatives. The authors cover thermal
       | storage in some detail.
       | 
       | https://www.frontiersin.org/articles/10.3389/fenrg.2020.0016...
        
         | EricE wrote:
         | You are spot on - the real answer is readily available:
         | nuclear. We have reactor designs that if the active systems
         | fail the reactors shut down naturally instead of running away.
         | We have designs that can be burning all that "spent" fuel we
         | are currently trying to bury for 10,000 years (!). Modular
         | reactor designs in particular have incredible promise to
         | provide for infinite scaling (just add more modules as needs
         | increase), deal with the inefficient building, maintenance and
         | decommissioning costs of todays light water reactor designs,
         | and being modular provide far more granularity in power
         | delivery further negating the need for energy storage to smooth
         | out spikes and troughs in demands; allowing energy producers to
         | far better match generation to power requirements.
         | 
         | Sadly I think it will be far more feasible to develop energy
         | storage technologies than hope we can ever get enough people to
         | be rational about nuclear. I mean how asinine is it for Germany
         | to have turned off perfectly working and economically viable
         | nuclear plants to then be dependent on RUSSIA for natural gas?
         | How dumb do you have to be to be to think that's a REMOTELY
         | good idea? Yet here we are (thankfully France seems to be far
         | more rational - you don't hear them even suggesting they plan
         | to be equally idiotic).
         | 
         | Many battery storage studies don't account for
         | replacement/maintenance, or the infrastructure that would be
         | required to sustain replacement/maintenance at grid scale, let
         | alone the resources required to scale up to handle initial
         | deployment of batteries in sufficient quantities to support the
         | entire grid. Where are we going to get the manufacturing
         | capacity, let alone materials? The scale here is pretty mind
         | boggling if you start to do the math.
         | 
         | Our current battery tech is nothing more than a transitory
         | technology - they are far from sustainable long term.
         | Personally I think super capacitors will be our ultimate
         | solution, but in the meantime if these guys really have dealt
         | with the seepage issues of compressed air, this is are next
         | best bet for MASS energy storage at scale. You only have the
         | privilege of worrying about efficiency if you have a working
         | system. Wood driven steam sucked, but it drove the industrial
         | revolution because there was literally no other viable
         | alternative at the time that could have remotely scaled in the
         | same way.
         | 
         | Remember grid scale solutions require MASSIVE energy
         | capabilities. The scale here is ridiculous compared to home or
         | vehicle energy requirements. If you don't think Goldman Sachs
         | took all of this into account before they made their investment
         | - well, you are grossly mistaken. You don't get to be their
         | size by continually placing bad bets.
        
       | mk81 wrote:
        
       | jesperlang wrote:
       | There is a great post on compressed air energy storage (CAES)
       | over at Low-Tech Magazine:
       | 
       | https://www.lowtechmagazine.com/2018/05/history-and-future-o...
        
         | tomcooks wrote:
         | Finally someone mentioning this, it's a gem of an article in a
         | gem of a website
        
       | tonke90 wrote:
       | There is already something like this in Germany, it even also
       | talks about saving the heat:
       | https://www2.ipp.mpg.de/ippcms/ep/ausgaben/ep200801/0108_spe...
       | (German)
        
       | ck2 wrote:
       | Why not use spare energy to lift -really- heavy object(s) and let
       | gravity power the generators when there is a shortage?
       | 
       | Million tons of concrete isn't going to suffer any maintenance
       | expenses over decades.
        
         | nkurz wrote:
         | That's a really popular idea on the internet because it's very
         | easy to grasp, but the numbers don't work out well. The weights
         | you can actually lift aren't much compared to the volume of a
         | reservoir of water, and the heights you can lift them are but a
         | fraction of the thousands of meters being discussed here. Yes,
         | the concrete isn't going to require much maintenance, but the
         | gearboxes needed are a significant engineering challenge.
         | Pumping water or compressing air are a lot easier, and
         | batteries are going to be hard to beat.
        
           | toss1 wrote:
           | Except it is already being done by multiple companies [0],
           | Energy Vault in Switzerland [1], Gravitricity in Scotland
           | [2], New Energy Lets go [3], and Gravity Power [4]. All have
           | raised substantial funds and are building.
           | 
           | Sure, pumped hydro has advantages, but has serious geographic
           | limitations - you need a fairly ideal site. The key is that
           | these can be built almost anywhere.
           | 
           | [0] https://spectrum.ieee.org/gravity-energy-storage-will-
           | show-i... [1] https://www.energyvault.com/ [2]
           | https://www.gravitricity.com/#about [3] https://n-e-l-g.de/
           | [4] https://www.gravitypower.net/
        
             | ted_dunning wrote:
             | See also the rail-based gravity storage:
             | https://aresnorthamerica.com/gravityline/
             | 
             | But the point about little progress by these companies
             | still holds. ARES has been around for 11 years now and has
             | one 50MWh project to talk about that covers 20 acres.
        
             | nkurz wrote:
             | Good point, and good examples. Excited online discussion
             | about companies like those are what I mean when I say it's
             | popular on the internet. It's not impossible, it's just not
             | the technology I would be betting on. To get a sense of
             | what one is up against, you can work through the math
             | comparing gravitational potential energy to electrical
             | potential in typical batteries. I can't find a good link
             | right now, but what I remember finding is that (in the
             | ideal) a typical lead acid car battery has enough stored
             | energy to lift itself into space! Conversely, if you wanted
             | to store the same amount of energy as in a typical car
             | battery, you'd need to be dropping that amount of weight
             | from the top of the atmosphere all the way to the ground.
        
       | aaron695 wrote:
        
       | PBnFlash wrote:
       | Air is kind of a shitty working fluid. I always kind of dismiss
       | compressed air storage because of that.
       | 
       | I saw a video recently that pumped water into tanks and used used
       | the air as a spring. Just dip a pipe down and use the air to move
       | the water. Extracting energy from a hyrdo generator.
       | 
       | https://youtu.be/sBF5EnK9MPs
        
         | u320 wrote:
         | Isn't that just pumped hydro? You would need similar masses of
         | water.
        
           | ted_dunning wrote:
           | It is pumped hydro, but you don't have the same mass of water
           | because of the dramatically different pressures involved.
           | Smaller water mass is the advantage to this, but the problem
           | of managing heat is the downside that pumped storage doesn't
           | face.
           | 
           | This general technique is known as "liquid piston".
        
             | PBnFlash wrote:
             | Thanks for the search term. I am not a huge fan of the
             | "advanced polymer" wank of that video but liquid piston
             | seems very practical compared most of the "air powered car"
             | nonsense compressed air systems that show up.
        
           | PBnFlash wrote:
           | I imagine it will get better performance from high pressure
           | water instead of the few psi of a small elevation change.
        
       | technicalbard wrote:
        
       | smoyer wrote:
       | Curiously there's a second article discussing compressed air
       | energy on the front-page of Hacker News at the moment - it's
       | about the Amish and their hacker mentality [0]. There's a
       | beautiful discontinuity between one of the more tech-savvy old-
       | guard banks and the technology-careful Amish adopting the same
       | technology.
       | 
       | 0. https://news.ycombinator.com/item?id=29905288
        
       | mwattsun wrote:
       | From another link on the front page the Amish use the term "Amish
       | Electricity" so this would be an Amish Battery
       | 
       | Amish Hackers
       | 
       | https://news.ycombinator.com/item?id=29905288
        
       | gjvc wrote:
       | "Workers descend to hollow out a cavity, which the company then
       | floods."
       | 
       | reminiscent of _The Day Today_
       | https://www.youtube.com/watch?v=eTGE9153VFE
        
       | ds wrote:
       | Can someone explain their revenue to me?
       | 
       | They claim 1m in revenue from their existing product which is:
       | "1.75 megawatts (MW) of peak power output; a 2.2 MW charge
       | rating; and 10+ megawatt-hours (MWh) of storage capacity"
       | 
       | How does that equal 1m in revenue? You have to pay to charge your
       | air-battery during low-cost hours and then discharge it during
       | high cost hours to make the difference in revenue.
       | 
       | The issue is, you can buy 2 megawatts of power 24/7 at average
       | datacenter energy pricing (~5c/kwh) for $2400/day or 876k/year.
       | Who is paying more than that for less energy and only at certain
       | hours?
       | 
       | Is there some energy company somewhere that sells power during
       | the day at like 50c/kwh and 1c/kwh at night???
        
         | 323 wrote:
         | While I don't know about their numbers, having a "grid level
         | battery" is definitely something people (or gov subsidies) will
         | pay for.
        
         | _delirium wrote:
         | These kinds of utility-run storage facilities usually buy and
         | sell on the wholesale spot market, which swings much more than
         | retail prices do. Somewhat similar economics to gas "peaker"
         | plants, which only fire up when supply is tight and prices
         | spike, making it economical to run a higher-cost generator.
         | 
         | The Hydrostor plant is in Ontario. Here's an archive of hourly
         | spot-market electricity prices there (in dollars per MWh):
         | http://reports.ieso.ca/public/PriceHOEPPredispOR/. So far in
         | 2022, prices have been as low as $0.00/MWh (during a few hours
         | overnight on Jan 5) and as high as $230.87/MWh (during the
         | morning of Jan 11). In 2021, hourly average prices even
         | exceeded $1000/MWh ($1/kWh) twice, on March 28 and October 10.
        
           | s1artibartfast wrote:
           | Still seems extreme. IF my math is right, they would need to
           | buy and sell 10MWh every day at a 27c/KWh markup. Given they
           | they deliver at ~2.2 MW, This means that they would have to
           | hit this markup for a 4 hour duration, every day.
        
           | ds wrote:
           | I would need to see the math, because nothing adds up to even
           | 1/10th of their claimed revenue. Best case, they bought 10mwh
           | on jan 5th and sold it at the perfect time on jan 11th. This
           | would give them 2k in revenue in 6 days.
           | 
           | Wheres the rest? And what about if you cant nostradamus
           | predict the best times to buy and sell?
        
             | fenixnuke wrote:
             | The other thing that they can be doing is selling standby
             | frequency response services to utilities:
             | 
             | https://smartgrid.ieee.org/bulletins/january-2016/energy-
             | sto....
             | 
             | Sometimes utilities only need a few minutes of power to
             | cover small gaps while ramping up/down powerplants, or if a
             | cloud passes over a solar generation facility. Since these
             | volumes are very small but critical, the effective price
             | per MWH is extremely high.
             | 
             | When Tesla did their grid scale battery installation in
             | Australia, this is how they made their money. Not via
             | energy arbitrage, but with selling frequency response
             | services. I have no idea if this is the same thing, but
             | there are other ways to make money with energy storage as
             | well.
        
         | s1artibartfast wrote:
         | I agree it does seem like a stretch.
         | 
         | IF 10MWh is their daily cycle, they are selling 3,650,000
         | kWh/year. To hit $1M per year, they would need to be selling
         | ~27c/KWh above their buying price.
         | 
         | I get that you can have a big spread if you are being paid to
         | take power, and paid again to sell it.
        
           | thehappypm wrote:
           | I think that's it basically. New England consumers pay
           | ~$.22/kWh. We're going to have offshore wind energy in the
           | next decade that might conceivably have surplus power quite a
           | lot. It's not beyond the realm of possibility that these
           | plants could have a deal with the power plants to take extra
           | power for free so long as they have guarantees on filling the
           | expected gaps or meeting expected spikes in usage. Everyone
           | wins.
        
         | fenixnuke wrote:
         | They are likely operating on the wholesale markets, which are
         | market priced. For the western grid there is a significantly
         | wider price range of prices. On peak days in the summer, prices
         | can go up above $1,000/mwh in the late afternoon for several
         | days. During the late fall/early spring, there are negative
         | prices in the late morning (like $20-$50/mwh) due to extremely
         | high solar production and low demand, so utilities are
         | literally paying you to use electricity. It's not inconceivable
         | to get to $1 million a year on 1 mwh of storage.
         | 
         | Take a look at the price maps and historical pricing data if
         | you are curious
         | https://www.caiso.com/todaysoutlook/Pages/prices.html
        
           | ds wrote:
           | Im familiar with energy markets. Im also familiar with the
           | fact that any serious seller or buyer of energy locks in
           | yearly pricing contracts and is unaffected by these swings.
           | Any serious datacenter or industrial buyer is not relying on
           | spot pricing. These energy markets also dont exist in every
           | state.
        
             | thinkcontext wrote:
             | If you are familiar with energy markets then by all means
             | tell us the percentage breakdown of electricity consumed
             | that is covered by long term contracts vs the spot market.
        
           | samstave wrote:
           | How can you make a storage system that only slurps power off
           | of another grid that "literally pays you to use electricity"?
           | during those times?
        
             | fenixnuke wrote:
             | There are times where the rooftop solar and base load
             | generation for a utility is greater than the total
             | electricity demand. Demand and supply for the grid have to
             | be balanced, or else you will end up tripping plants and/or
             | damaging equipment. Since they can't "turn off" rooftop and
             | most grid scale solar generation, and they can't really
             | turn off and on their base load plants throughout the day,
             | their best option is to try to sell the excess electricity
             | on the wholesale market. The problem is that the other
             | utilities are in the same situation, and they need to
             | offload electricity. Since no one wants the electricity,
             | wholesale prices will actually go negative. Basically a
             | utility will pay another utility to turn off a base load
             | plant and take the excess electricity from them.
             | 
             | This is why grid scale energy storage is such a hyped
             | technology - if you can store that energy when supply is
             | way too high and dispatch it when renewable generation is
             | low (no wind/solar), you can maintain high renewable
             | percentage in the generation mix. Without it, you can only
             | really go up to a certain percentage of renewables.
        
             | EricE wrote:
             | Buy low and sell high. They can find surplus power and buy
             | it cheap, then wait until there are unmet demands and sell
             | high.
             | 
             | These crazy things called computers make creating and
             | automating markets like that pretty easy :)
             | 
             | It's win win - the people with surplus power can at least
             | get some money for energy that would otherwise likely go to
             | waste (large base load power plants can't ramp up and down
             | on a dime) and on the flip side if you have an energy
             | provider that only occasionally needs capacity in excess of
             | their inherent generation even though the immediate cost is
             | higher for spot power, it can still be far cheaper in the
             | long term than building more base load generation (often
             | fossil fuel because renewable still isn't a viable
             | replacement for base loads). And running base load
             | generation under capacity is wasteful for emissions and
             | overall efficiency.
             | 
             | Once we start to crack the whole energy storage thing
             | renewables will be A LOT more valuable since we will be
             | able to start to use them for base load. Storage allows you
             | to create reliable energy delivery that's predictable -
             | that's essential if we ever want to eject fossil fuels from
             | the grid. Or we could stop being childish about nuclear
             | power - frankly I think we can solve the storage problem
             | long before we can convince people to be rational about
             | nuclear :p
             | 
             | It probably seems crazy for the uninitiated, but there are
             | a lot of efficiencies in markets that occur naturally over
             | time. You see distortions in the market from CA's stupid
             | and politically motivated choices - what seems crazy to you
             | is the market adapting to the model that CA is forcing. Is
             | it nuts? Yup. Is it necessary? Nope - these wounds are
             | entirely self inflicted. Pretending the world is different
             | than it actually is doesn't solve anything and the people
             | of CA are paying a hell of a lot more for electricity
             | because they are trying to live in a pipe dream for where
             | we are today.
        
           | reincarnate0x14 wrote:
           | A lot of people look at these and think "that doesn't seem
           | like it'd be remotely worth it for something that size" but
           | it's really hard to explain just how badly California has
           | painted itself into a corner on distant generation, huge
           | variance between excess renewable capacity and peak load, and
           | transmission congestion. The numbers don't make sense to
           | people.
           | 
           | Pretty much all the solar plants we're putting in now have
           | combined battery storage systems either for voltage support
           | or "peaker" sales opportunities. In some places (like literal
           | islands) it's about capacity smoothing or resilience, but the
           | driving force behind all the investment is the US western
           | interconnect with arbitrage opportunism starting to make real
           | money and looking to make much, much more over the next
           | decade.
           | 
           | If government-sachs is betting on this, they've probably got
           | an even more pessimistic take on the CAISO market than I do.
        
             | buryat wrote:
             | > it's really hard to explain just how badly California has
             | painted itself into a corner on distant generation
             | 
             | source needed if you're making such a bold statement
        
               | EricE wrote:
               | Just read the constant stream of news about it? They keep
               | shutting down power plants in the name of the
               | environment, but just shift the generation outside of the
               | state. It's a numbers game that's meaningless as long as
               | they still consume power, but it lets them virtue signal
               | all over the place to people who don't pay attention to
               | details - which sadly is most of us. How many times when
               | we are give stats do we really wonder about the context
               | around them?
        
       | MPSimmons wrote:
       | That sounds dangerous.
        
       | hinkley wrote:
       | Dave Borlace (Just Have a Think) has been covering this space a
       | bit. There's a whole space in power storage that also overlaps
       | with carbon capture that I suspect will probably end up being the
       | winning play because cogeneration can often double system
       | efficiency, making unprofitable things profitable.
       | 
       | One way we can reduce carbon intensity is to stop using fossil
       | fuels to generate industrial CO2.
       | 
       | There's a kind of metal-air battery that actually absorbs CO2
       | while charging, and emits it while discharging. There is also air
       | liquification as power storage, in which you can separate the
       | oxygen, carbon dioxide and nitrogen into different containers.
        
       | AlexTWithBeard wrote:
       | In early 20th century in London there was an alternative
       | hydraulic "power grid" with plants (aka pumps), storages and an
       | underground distribution network of pipes. A building, for
       | example, could connect to high pressure water mains and use it to
       | power elevators. Electricity eventually won, but it's interesting
       | to see an idea coming back.
       | 
       | Zeppelins next!
       | 
       | [1] https://en.wikipedia.org/wiki/London_Hydraulic_Power_Company
        
         | samstave wrote:
         | There also used to be "central turbines" whereby there was a
         | central spinning rod that one could attach belts to in order to
         | spin a thing to get work out of it...
         | 
         | called line and shaft
         | 
         | https://www.youtube.com/watch?v=7qt5tltnvF8
        
           | cjrp wrote:
           | Really cool, sort of like how an ICE drives ancillaries
        
             | spenczar5 wrote:
             | Cool indeed, but pretty dangerous and difficult to
             | reconfigure. Electric wires and motors are so much smaller,
             | and easier to protect, and more interoperable, so you can
             | see why they won out.
        
               | AlexTWithBeard wrote:
               | That was one of the reasons behind having factory
               | whistles: all workers take their places, the whistle,
               | then the whole thing is started. While it's running
               | people are not supposed to move around.
        
           | Someone wrote:
           | That was normal in the age of steam. Having lots of tiny
           | steam engines on the factory floor does not make sense.
           | Keeping them running is too labor intensive, they would be
           | fire risks, and they're less efficient.
        
             | DuskStar wrote:
             | And in the age of water, running shafts to the waterwheel
             | was vastly easier than having a wheel at each station.
        
           | DrBoring wrote:
           | I once saw this in use at a restaurant to drive ceiling fans.
           | I looked up some videos:
           | 
           | https://www.youtube.com/watch?v=y-uCvwEq3co
           | 
           | https://youtu.be/1IWTM1rNCnw?t=78
        
           | snalty wrote:
           | There's a cool working example of this at Kelham Island
           | Museum in Sheffield, England.
        
         | IncRnd wrote:
         | Hydraulic refers to liquid. Pneumatic refers to compressed air.
        
         | adrianmonk wrote:
         | That is an interesting system (which I had never heard of), but
         | it seems pretty different from this.
         | 
         | The London system used water under pressure and was used for
         | power distribution, whereas this one compresses air and is for
         | energy storage.
         | 
         | And the Wikipedia article says the London system used "large
         | vertical pistons" with weights to store energy, whereas this
         | one pressurizes air.
        
         | JoeAltmaier wrote:
         | The University of Iowa campus has a steam system under the
         | campus, installed in the last century. Nowadays the steam is
         | recovered waste from the electric plant. But it's still in use!
        
           | bumby wrote:
           | If you want to find good candidates for saving the campus
           | tons of money, go to the roof of one of the tallest buildings
           | on a cold day and look for the buildings that are venting
           | lots of steam. They likely have a failed steam trap somewhere
           | in the building. It's not uncommon for failed steam traps to
           | save thousands of dollars a year apiece when fixed.
        
         | javajosh wrote:
         | Zeppelins with modern materials and technology would be very,
         | very cool. I'd ride in one.
        
           | Melatonic wrote:
           | The military is actually doing a ton of work with blimp and
           | zeppelin like things currently - you do not hear about it
           | much but there is a a ton of testing and research being done.
        
           | xwdv wrote:
           | What would be even cooler is zeppelins with swimming pools
           | and jacuzzis while you take in the views of the sky.
        
             | LargoLasskhyfv wrote:
             | Made out of transparent material, so you could look down
             | too.
        
             | dr_dshiv wrote:
             | Glass-bottomed ballroom, anyone?
        
               | AlexTWithBeard wrote:
               | Plane spotting gets a new color with that.
        
             | javajosh wrote:
             | I'm picking up what you're putting down.
        
         | freefal wrote:
         | A bit tangential, but New York City has an operating steam
         | system that's still widely used by commercial customers.
         | 
         | https://en.wikipedia.org/wiki/New_York_City_steam_system
        
           | dmix wrote:
           | The interesting part of the NYC one is the scale
           | 
           | > Today, Consolidated Edison operates the largest commercial
           | steam system in the world (larger than the next nine
           | combined).
        
           | radicaldreamer wrote:
           | San Francisco has one too, used primarily for heating
           | buildings
           | https://clearwaycommunityenergy.com/system_lists/energy-
           | cent...
        
           | antupis wrote:
           | District heating is pretty normal at northern Europe altought
           | now we use mostly water.
        
             | m4rtink wrote:
             | The district heating in Brno here in Czech Republic is in
             | the process of converting from steam to hot water, mainly
             | due to cost savings. Modern isolated hot water pipes loose
             | a negligible ammount of heat in transfer while there was
             | green grass growing on top of the old buried steam pipes
             | even in winter.
             | 
             | That and the old textile industry that directly used steam
             | no longer exists.
        
             | pinot wrote:
             | District heating with water is vastly more safe, I imagine
             | that's why its used.
             | 
             | I remember my apartment in germany had a "Heat" meter on
             | the water line, always wondered how that worked.
        
               | krab wrote:
               | We have a calorimeter - it should count volume of hot
               | water times the temperature difference. I heard it's not
               | very precise.
        
           | Naga wrote:
           | Downtown Ottawa has a similar steam system too, although I
           | think it's mostly government buildings instead of private,
           | commercial buildings that are hooked up to it.
        
           | wefarrell wrote:
           | It is funny (if not terrifying) that we have literal geysers
           | spring up on crowded city streets every once in a while.
        
         | mderazon wrote:
         | Isn't that the concept behind "streampunk" ?
         | 
         | https://en.m.wikipedia.org/wiki/Steampunk
        
         | _pmf_ wrote:
         | The Amish use compressed air:
         | http://www.amishfamilyvalues.com/amish/amish-electricity/
        
           | caseyohara wrote:
           | This is interesting:
           | 
           | "This was a crisis. Without electricity, the Amish couldn't
           | store milk, and the church was adamant that Amish were not
           | going connect to the local electric company. Finally a
           | solution was found. It was decided that diesel generators
           | could be used to power the refrigerators. This decision
           | allowed the Amish to continue their tradition as dairy
           | farmers without having to use public electricity."
           | 
           | So the Amish are allowed to use electricity, just not from
           | the public grid? Generators seem like a weird loophole to
           | their own rules.
        
             | flyinghamster wrote:
             | > So the Amish are allowed to use electricity, just not
             | from the public grid? Generators seem like a weird loophole
             | to their own rules.
             | 
             | That depends greatly on the congregation. Each congregation
             | sets its own rules on how to deal with technology. "Not
             | inside the home" is a very common technological limit. Cell
             | phones might be stored in a shed, fed by solar chargers,
             | for use out in the field. A workshop might have electricity
             | from a wind/solar installation or even a diesel generator,
             | but not the attached house.
        
             | s1mon wrote:
             | If you think this is weird, wait until you see the
             | convoluted/clever things that some Jewish people do to work
             | around the sabbath.
             | 
             | https://www.npr.org/2019/05/13/721551785/a-fishing-line-
             | enci...
             | 
             | https://en.wikipedia.org/wiki/Shabbat_elevator
             | 
             | https://en.wikipedia.org/wiki/Sabbath_mode
        
             | userbinator wrote:
             | If they are against centralisation, that makes sense; but
             | then, unless you drill your own wells and refine the crude
             | yourself, you're still getting fuel from someone else.
        
         | rcurry wrote:
         | I once took a tour of the Mabel Tainter theater in Menomonie
         | Wisconsin. The original light fixtures had been built to work
         | off of both gas and electricity, just in case the whole
         | newfangled electricity thing didn't work out.
        
         | mabbo wrote:
         | This sort of system is used today in many modern industrial
         | facilities. Case in point: Amazon warehouses.
         | 
         | Lots of the mechanical automations inside some of those
         | warehouses are powered by compressed air in open loop systems.
         | As the conveyor pushes the item off, onto a different lane,
         | there's a distinct hiss of air escaping. The movement of the
         | machine was powered by compressed air.
         | 
         | Out in the parking lot in these facilities, you'll see a huge
         | compressed air tank (or many), constantly being refilled. Tubes
         | from these go into the building like arteries in a body. Often
         | inside the building there will be buffer tanks to help ensure
         | constant pressure.
         | 
         | Source: worked for a few years with guys who maintained these
         | systems. Some of what I learned may be wrong, so feel free to
         | correct me.
        
           | throw8932894 wrote:
           | It is pretty common in regular workshops. Compressed air
           | powers drills, riveting machines, sprays guns, jack
           | hammers... Tools powered by compressed air are simpler (no
           | electronics), more durable and cheaper.
        
             | bin_bash wrote:
             | You forgot the most important reason they're used: they're
             | far more powerful!
        
             | mnahkies wrote:
             | My favourite thing about air tools was not having to worry
             | about batteries (most electric hand tools I've used are
             | battery only so no opportunity to use an extension lead
             | like you use an air hose)
        
               | grawprog wrote:
               | Most electric hand tools are usually available for
               | cheaper in a corded variety. The only electric hand tool
               | I haven't seen come corded are impact drivers and most
               | impact drivers I've used will last a day or two using it
               | 8 hours a day even off a 2aH battery.
               | 
               | For me, I like air powered tools because of their power
               | and reliability. They'll almost always have more torque
               | and power than similar electric tools.
        
               | WheatM wrote:
               | Air tools defintely don't have more torque than electric
               | tools, they rely on speed to overcome their shortcomings
               | in torque. The main high torque application in air tools
               | is in impact wrenches, which use very fast hammering
               | action. Modern battery impact wrenches can match the
               | performance of the best air wrenches.
        
               | throwawayboise wrote:
               | The motor also doesn't create sparks so they are more
               | useful in flamable atmospheres.
        
           | bumby wrote:
           | They aren't really the same types of systems.
           | 
           | Pneumatic "muscle pressure" is common in lots of industrial
           | applications, especially those that operate in austere
           | environments. But those are different than the tech being
           | researched in the article in large part because the
           | mechanical compressors in industrial applications are hugely
           | inefficient. Many constant volume compressors have 90%+ of
           | the energy as waste heat.
           | 
           | I believe the article is referencing isobaric (constant
           | pressure) compressed air energy storage (CAES) that have much
           | better efficiencies.
        
             | cinntaile wrote:
             | How does this work? How can you compress air without
             | raising the pressure? Are you sure you don't mean
             | adiabatic?
        
               | bumby wrote:
               | An external pressure (usually water) keeps it at a
               | constant pressure.
               | 
               | Think of a bag of air under water on the ocean floor. The
               | height of the water column is (relatively) constant, so
               | the pressure in the bag is also constant.
        
               | ryan_j_naughton wrote:
               | According to PV=nRT (ideal gas law), no you cannot in a
               | closed system!!! But Hydrostor isn't violating any laws
               | of physics -- they are simply capturing that heat so that
               | it doesn't become waste heat!
               | 
               | Hydrostor has a thermal management system that captures
               | the heat and stores is during compression. Then it reuses
               | the heat when it is decompressing the air.[1]
               | 
               | This seem extremely promising as a much smaller footprint
               | solution than pumped storage and much more sustainable
               | and lower cost than any other energy storage solution. I
               | just heard about them today, and I'm extremely impressed.
               | 
               | [1] https://www.youtube.com/watch?v=cOWjwwKSR78
        
               | [deleted]
        
             | mabbo wrote:
             | Oh I agree it's not quite the same as in the article. I was
             | comparing to what the parent comment was saying about large
             | pneumatic tube networks in ages past.
        
           | enginoor wrote:
           | The common term is "pneumatics" and the components are
           | prevalent in all automation and manufacturing. The air
           | required is typically compressed on site.
           | 
           | Pneumatic actuators are relatively inexpensive, have a binary
           | state that is easy to control, and offer a high power
           | density.
        
             | laurent92 wrote:
             | How do they avoid bacteria/mould from growing in tanks and
             | flocking the pipes and releasing in the room? Do such
             | systems ever get cleaned up?
        
               | [deleted]
        
               | HPsquared wrote:
               | The air in industrial pneumatic systems is filtered and
               | dried, which would prevent these issues.
               | 
               | Pneumatic systems often use small orifices and valves to
               | control the air flow which would be quickly clogged by
               | any debris, so cleanliness is important.
               | 
               | An aside: PID control was, back in the day, mostly
               | implemented in pneumatic control systems (using a set of
               | levers, bellows springs and nozzles). Pneumatic control
               | systems were (and still are) used a LOT in industrial
               | control systems where e.g. flammable environments where
               | electrical equipment is too much of a risk.
               | 
               | https://control.com/textbook/closed-loop-
               | control/pneumatic-p...
        
         | MSFT_Edging wrote:
         | There was an article on here earlier about Amish tech and they
         | also make use of a lot of pneumatic machines for daily tasks.
        
       | dylanz wrote:
       | Is this similar to a trompe?
       | https://en.m.wikipedia.org/wiki/Trompe
        
       | rdtwo wrote:
       | In the 80s my grandfather used to do this for the former Soviet
       | Union. Long story short they were pressuring a salt mine at night
       | for energy storage and somebody failed to report a water leak
       | during the day. They tried to depressurize the mine but it ended
       | up blowing up anyway killing a couple people in The process. This
       | shit can be really dangerous if done incorrectly.
        
         | faeyanpiraat wrote:
         | How did the situation go from a water leak to an explosion?
        
           | alan-crowe wrote:
           | The Lake Peigneur Drilling Accident is a tale of water
           | getting into a salt mine from the lake above, due to drilling
           | for oil in the wrong place. As the water dissolved the salt,
           | the hole grew bigger and bigger, exponentially. The lake
           | emptied into the salt mine, turning it into brine.
           | 
           | https://en.wikipedia.org/wiki/Lake_Peigneur
           | 
           | So I'm picturing water leaking into a salt mine full of
           | pressurized air. Naively it makes a hole, and a hole is just
           | a leak. But if the water starts dissolving the salt in a
           | process that runs away, then it is more like popping a
           | balloon, but on a grand scale.
        
             | rdtwo wrote:
             | Exactly this. Popped a balloon that just happened to be the
             | size of a mountain
        
         | slingnow wrote:
         | Can you name a method of large scale energy storage that isn't
         | dangerous if done incorrectly?
        
           | karmakaze wrote:
           | I think the comment is more about being easy to do
           | incorrectly/dangerously. Pumping water up into a reservoir
           | seems easier/safer.
        
             | thehappypm wrote:
             | You've picked the one that probably has the highest death
             | toll worldwide!
        
             | xhkkffbf wrote:
             | Read up on the Johnstown Flood.
             | 
             | https://en.wikipedia.org/wiki/Johnstown_Flood
        
             | WJW wrote:
             | Lots of water in a reservoir is not particularly safe in
             | itself. For example, in December 2000 at the Grande Dixence
             | a high-pressure pipeline from the dam burst, causing a
             | landslide that wiped out a small hamlet and killed three
             | people. It's also not hard to find reports of massive
             | amounts of casualties and/or property damage from dams that
             | just outright fail.
        
               | Choco31415 wrote:
               | An underground reservoir of water though should still be
               | safer. Only the operator(s) on site might be impacted by
               | a failure.
        
             | rdtwo wrote:
             | Yeah a large pressure vessel is basically a bomb. No matter
             | how many layers of protection you add on the technology
             | always wants to go too a rapid critical failure. Using
             | statistics and layers of protection you can always show it
             | to be safe to handle anything but when you get to such low
             | probability your models be always be off and variables that
             | you think are independent are actually linked (bad
             | maintenance practices being one)
        
             | usrusr wrote:
             | Water reservoirs for energy generation/storage have gone
             | through accidents killing thousands. I suggest looking up
             | Vajont on Wikipedia.
             | 
             | The project mentioned in the article seems particularly
             | safe to me as they seem to run it with constant pressure,
             | defined by the hydrostatic head of their deeply dug
             | cavities. They don't really have a pressure vessel, they
             | have a flooded cavern where they create a bubble by pushing
             | in air. If you pop off a seal from the pipes connecting
             | compressors/turbines to the bubble could still hurt
             | yourself a lot shooting parts through the room, but that
             | should be all.
             | 
             | The cavity they build is 2000 feet deep, which equates to
             | the pressure of a CO2 cartridge that you'd use for e.g.
             | carbonating a beverage. Not coincidentally at all I think,
             | they either aim for the deepest cavity were hydrostatic
             | pressure isn't enough to liquefy parts of the air, or for
             | the least deep dig that gives them liquefication, where the
             | air "boils off" as they open the valves.
        
               | rpeden wrote:
               | Pumped storage is a bit different than an ordinary
               | reservoir with a dam, though. You have more opportunity
               | to build it in a place where it's less likely to cause
               | harm is something goes wrong. It has been used pretty
               | effectively on both sides of the border near Niagara
               | Falls for 60+ years.
               | 
               | It's not perfect, of course. Accidents still happen, for
               | example: https://en.wikipedia.org/wiki/Taum_Sauk_Hydroele
               | ctric_Power_... although fortunately nobody was killed.
        
       | 0898 wrote:
       | This brings to mind the other post about the Amish that's on
       | today's front page. I believe the Amish sometimes use compressed
       | air as an alternative form of power.
        
         | wongarsu wrote:
         | Also quite popular in mines because it doesn't create sparks.
        
         | MisterTea wrote:
         | I read an article in a woodworking magazine about how one Amish
         | woodworking shop was built to avoid using electricity. The
         | whole shop ran off a stationary diesel engine driving a shaft
         | in a floor trench and belt drove the larger stationary
         | machinery like band saws, table saws, planers, drill presses,
         | joiners and so on. But what about hand tools? A large belt
         | driven air compressor off the diesel engine handled a myriad of
         | air power tools like drills, orbital sanders, buffers and all
         | that. Really neat setup.
        
           | blincoln wrote:
           | My father once told me that a lot of machine shops used to be
           | set up that way, except that the powered shaft ran along the
           | ceiling instead of in a floor trench. "Just throw a belt up
           | over the shaft" and attach it to the machine you want to use,
           | was how he described it.
           | 
           | I don't know if it's still there, but there used to be a
           | fancy restaurant in the Eastlake part of Seattle that had
           | started out that way, and still had the old Art Deco-ish
           | drive shaft running around the ceiling. It was a neat touch
           | point when I saw it and remembered my dad's description from
           | years before.
        
             | robotresearcher wrote:
             | Yes, the industrial revolution was powered this way. Water
             | wheels and steam engines as central power plants, with
             | power distributed mechanically.
        
               | bootlooped wrote:
               | My understanding is that this paradigm was incredibly
               | dangerous, with a lot of workers losing hands and arms in
               | accidents. Turning on or off a given machine involved
               | physically putting the belt on or pulling it off, and you
               | could easily get caught in it. A very clever system for
               | the technology of the day, but it's good we don't use it
               | anymore, at least without more advanced safety mechanisms
               | and practices.
        
               | throwawayboise wrote:
               | I would have assumed they would have clutches so that
               | individual machines could be disengaged. The large open
               | belts running up to the drive shaft on the ceiling were
               | dangerous regardless.
        
           | noselasd wrote:
           | This is basically how most indistrial setups was before
           | engines and motors became a commodity. You had water wheels
           | as your main power source, from which other tools was driven
           | via belts and gears.
           | 
           | Later the waterwheel was replaced by an electric motor or a
           | fuel powered engine - but still built around just one source
           | of power, with elaborate setups to drive different tools.
           | With the added benefits you could build factories and
           | workshops outside main water sources.
        
             | MisterTea wrote:
             | There is a wonderful museum in Windsor Vermont called
             | American Precision Museum which still has the original
             | overhead shaft and pulley system along with machinery. Went
             | there in the early 90's as a kid and they did mention that
             | it was converted to electric and the motors were still
             | working supposedly.
             | 
             | The Edison museum in Orange NJ also has such a preserved
             | shop setup but electric driven by one or two big motors on
             | an elevated platform.
        
           | bobsmooth wrote:
           | I thought the whole schtick of the Amish was that they don't
           | allow themselves to become reliant on technology, electricity
           | just being an example. I doubt that Amish guy knows how to
           | rebuild that engine should it fail.
        
             | a2tech wrote:
             | They don't believe in having technology in the home. Most
             | Amish are perfectly willing to work with modern equipment
             | for their shops and businesses. Go by an Amish milking shed
             | anywhere in the country--as my dad would say 'they're lit
             | up like a shit house in the fog'. Electric lights from one
             | end to the other with modern milkers inside.
        
             | willcipriano wrote:
             | The Amish only allow technology that they think will
             | improve their lives. Many have cell phones, but don't use
             | Facebook for example. I'd also bet he could repair the
             | engine if he needed to.
        
               | yetihehe wrote:
               | There was a comment somewhere where they used modern cnc
               | machines to make parts for their air tools.
        
           | lostapathy wrote:
           | Also adds a ton of pollution from using (often old and poorly
           | maintained) Diesel engines in the name of avoiding the
           | electric grid. Adding to that, compressed air is a much less
           | efficient source of power than using electricity directly.
        
             | toss1 wrote:
             | Yes, but air tools can be really nice to use,esp for
             | grinding, cutting, sanding operations. For one, you can
             | press/dig hard enough to bog or stop the tool and nothing
             | hapoens - you just pick it uo and it speeds back uo again -
             | do that with an electric tool and you'll have a dead motor
             | paperweight real soon.
             | 
             | Air tools can also be lighter and no worries abt damaging
             | the cord or carrying the battery.
             | 
             | Many good air tools can also have a better feel, especially
             | if you can control the air flow trigger.
             | 
             | (I don't have a bias either way, use both in my shop, but
             | just wanted to point out that both have advantages)
        
               | lostapathy wrote:
               | I agree - air tools are awesome in some cases, although
               | modern brushless tools are often competitive if not
               | superior to air tools compared to how things were a
               | decade ago.
               | 
               | My complaint, really, is just how selfish it is to go out
               | of your way to use a dirty energy source as a workaround
               | for limits in your personal belief system.
        
       | CarbonCycles wrote:
       | This isn't new...I recall grad students working on this as far
       | back as 2010.
       | 
       | Some citations from an article: "Bottled wind could be as
       | constant as coal." Wired Magazine. Retrieved 7/15/2010, 2010,
       | from http://www.wired.com/wiredscience/2010/03/compressedair-
       | plan... 59
       | 
       | Cavallo, A. (2005). Controllable and affordable utility-scale
       | electricity from intermittent wind resources and compressed air
       | energy storage (CAES). Science Direct.
        
         | rplnt wrote:
         | > This isn't new...
         | 
         | Well, yeah, this is in the opening of the article:
         | 
         | > It updates a long-standing technology that never took off for
         | electrical storage.
         | 
         | There is/was plant operational since 1970s in Germany[1], which
         | looks similar to the Wired article, but different from some
         | other solutions posted in comments. Missing some parts perhaps
         | to be viable.
         | 
         | 1. PDF: http://www.fze.uni-
         | saarland.de/AKE_Archiv/AKE2003H/AKE2003H_...
        
       | NotChina wrote:
        
       | belorn wrote:
       | How does the economics of this look like, and how do they
       | intended to get back the investment. If its to buy low when
       | wind/solar production is high and sell when production is low,
       | what will the cost per watt be? If its subsidies, how much will
       | this cost the government?
       | 
       | The article seem to mostly describe this as a technology project
       | to test the technology at scale, but they do also mention
       | profits. Is the basic premise of buy low sell high, exclusively
       | on renewables, enough to offset the cost from energy conversion,
       | building, staff and other costs, and if so, by what degree
       | compared to other method to produce energy? When is it estimated
       | to have paid its initial investment?
        
         | EricE wrote:
         | Energy storage if you want to rely solely on renewable energy
         | sources is THE KEY to making that even remotely feasible.
         | 
         | Current solar and wind renewables are NOT predictable nor
         | reliable for sustained power generation. With Coal, Natural
         | Gas, Nuclear and Hydro you can generate power on demand, no
         | matter what the environment is doing. Well, Hydro in the west
         | is getting dicey with the drought - but even that is far more
         | stable than wind/sun which can vary wildly week to week, day to
         | day or even hour to hour.
         | 
         | That's why technology like this is so exciting. If you can look
         | at the average production of a renewable over a month, then
         | within a year the peak month, then look at the worst months,
         | then have enough storage to cover a percentage of a peak month
         | based off the hedge of the worst month then you are getting to
         | a point where a solar farm isn't just an opportunistic source
         | of power based on how much the sun is shining, but a reliable
         | energy source that can be counted on whether the sun is shining
         | or not.
         | 
         | Same for wind farms.
         | 
         | Energy storage is crucial if we seriously want to transition to
         | renewables and hence the investment from Goldman Sachs.
         | 
         | If this company is even remotely successful in actually
         | delivering then $250M is a pittance to what they will receive
         | back in the long term.
         | 
         | There are also a lot of unused/abandoned underground structures
         | - from various wells that are now dry of the resource they were
         | originally drilled for to mines that are no longer productive.
         | The problem has been sealing them from seepage so you don't
         | loose your stored air - this article was light on details but
         | that seems to be this companies claim to fame. They seem to
         | have found economical ways to deal with those issues - enough
         | to convince the boffins at Goldman Sachs they are worthy of
         | investment. I guarantee you Goldman is not just tossing out
         | money willy-nilley without performing some significant due
         | diligence!
        
           | belorn wrote:
           | The question is still economics. At minimum the cost per
           | watt/h need to be cheaper than to build a nuclear plant and
           | have it run when demand exceed supply from renewables. Is
           | this true for compressed air?
           | 
           | When people discuss green hydro as a storage solution the
           | numbers so far, from what I have managed to interpret, is
           | around 3-5 times that off nuclear for the same amount of
           | energy delivered. It is still technically possible to make a
           | profit given enough subsidies and time, and it get much more
           | economically if the hydrogen can be used directly in the
           | production chain like steel and fertilizer. Right now there
           | are a steel foundry in Sweden testing the technology and
           | economics doing that, through I don't know how much subsidies
           | and tax reductions were involved.
           | 
           | Which all means the question about economics remains. There
           | are many alternatives to fossil fuels but the primary
           | question everyone debates is the issue of price. Without a
           | price per watt/h or a time frame for when the investment get
           | repaid its impossible to separate the practical from
           | impractical, and the subsidy question is very relevant when
           | discussing this on a national level.
        
       | sauwan wrote:
       | The round trip efficiencies for these compressed air storage have
       | typically been terrible (<50%). That's mostly because compressing
       | air is super inefficient (lots of wasted heat). Are they able to
       | harness that waste heat in some productive way?
       | 
       | ETA: Just saw the video. Looks like they store the heat to boost
       | generation on the return trip. This [1] says they get ~60%
       | efficiency.
       | 
       | [1] https://www.inceptivemind.com/hydrostor-build-largest-
       | compre...
        
         | arnaudsm wrote:
         | 60% is great! That's much better than hydrogen, but still far
         | from lithium. Let's hope the $/kWh is decent.
        
           | thehappypm wrote:
           | Especially when you consider that the use case here is
           | surplus energy, like when the wind is blowing harder than can
           | be consumed. Efficiency might not be so important if you're
           | buying free wind or solar energy, as long as it's above some
           | minimum threshold. 60% feels pretty good.
        
           | danans wrote:
           | It's not quite lithium ion efficiency, but it serves a
           | different duration energy storage market (up to 24 hours vs
           | single hours for lithium ion battery storage), and it has a
           | much longer service life (50 years), so the levelized cost of
           | storage might be lower than lithium ion battery storage.
        
             | sokoloff wrote:
             | The lithium ion batteries in my car store energy for weeks
             | on end with losses around 1-2% per week (after an initial
             | couple percent rapid drop).
        
               | danans wrote:
               | What I meant is that current grid scale lithium ion
               | battery storage projects are designed for at maximum a
               | few hours between charge and discharge. They are mostly
               | for shorter window grid stabilization, not to store
               | energy for days or weeks.
               | 
               | LiIon grid scale batteries are still very expensive as a
               | long term energy storage solution, they are sized to
               | provide higher value grid ancillary services, like
               | frequence regulation.
        
       | smm11 wrote:
       | I had a huge burrito last night, and I am as I type, a massive
       | compressed air storage device.
        
       | nkurz wrote:
       | Interesting. There's a good video describing the operation here:
       | https://www.youtube.com/watch?v=cOWjwwKSR78
       | 
       | After watching it, I now understand that they aren't flooding the
       | entire borehole, but rather are building a smaller high-pressure
       | chamber at the bottom. The chamber is connected to pipes to a
       | surface reservoir. When air is pumped into the chamber, it
       | displaces water up toward the surface. When generating, the water
       | flows back into the subsurface chambers, forcing out the high
       | pressured air.
        
         | keewee7 wrote:
         | What goes into building and burying large scale underground
         | structures like those air caverns?
        
           | mschuster91 wrote:
           | Not much, technologically this is a conventional mine
           | project, only that you mine air volume instead of rock and
           | have to take care of the cavern being reasonably airtight
           | afterwards.
        
             | jhallenworld wrote:
             | Also you could do it underwater if you live near a coast.
             | Basically an upside down cup with a pipe in it, sunk as
             | deep as possible.
        
           | buryat wrote:
           | you don't have to build those caverns as they already exist
           | and we have extracted gas and liquids from them, also the
           | volume should be already known as we know how much we pumped
           | out (unless it's an old site)
        
             | srcmap wrote:
             | Isn't the complexities related to making those caverns air
             | and water tight for long period of time for long term
             | energy storage requirements?
        
               | count wrote:
               | They don't need to be air/water tight for long term, just
               | tight enough with a known leakage factor.
        
               | edzillion wrote:
               | But how cheap is it to determine the leakage factor? I
               | suppose they can just pour in the equivalent water and
               | see if it leaks?
        
         | flyinghamster wrote:
         | A similar thing is done for natural gas storage. A well will be
         | drilled into a rock dome that lies atop a layer of saltwater-
         | saturated sandstone. Gas is then pumped into it, displacing the
         | water, and then can be withdrawn later.
         | 
         | A report from 1961:
         | https://www.ideals.illinois.edu/bitstream/handle/2142/42910/...
        
         | mirekrusin wrote:
         | I wonder what is the loss/recovery %age.
        
           | epistasis wrote:
           | I don't have specific numbers, but in other batteries of this
           | type, the length of storage time before discharge affects the
           | efficiency. Heat stored from compression is lost over time.
        
             | ehnto wrote:
             | I was curious about that as well. I think it's best
             | application would be to compensate for large amounts of
             | rising and falling generation from solar grids, that way
             | the cycle is daily. Being quick to come online and meet
             | demand makes it good for maintaining grid stability at a
             | much lower cost as well, like the Hornsdale Power Reserve
             | facility https://hornsdalepowerreserve.com.au/.
        
         | tikkabhuna wrote:
         | Totally out of my depth here, but does cooling the gas down
         | have the added benefit that it'll be heated by the earth whilst
         | stored?
        
           | JohnL4 wrote:
           | I'm guessing not. Earth's heat is way lower down. Think of a
           | cave: always cold. I think what's going on is they're taking
           | the heat out and storing it more efficiently than just
           | dumping it down the ground, where (1) it would leak away,
           | representing energy loss, and (2) as it leaks away, the air
           | would lose pressure. (It would leak away b/c it's harder to
           | insulate an entire mine, basically.) So, they pull it out
           | ahead of time and put it back in when they decompress the air
           | (which I think would add pressure back in due to heating a
           | gas and maybe reduce problems caused by super-chilling other
           | plant hardware? Anyway, seems fitting to add back what you
           | took out if you're shooting for a closed system.)
        
             | OneLeggedCat wrote:
             | > Earth's heat is way lower down
             | 
             | Very incorrect.
        
             | Raidion wrote:
             | This isn't correct. Deep mines are notoriously hot, because
             | you're digging towards magma. Google says temps increase by
             | 3deg C for every 100m.
        
               | emptysongglass wrote:
               | Naive question but couldn't our forerunners who otherwise
               | succumbed to cold in harsher climates have exploited this
               | fact to dig subterranean villages and towns?
               | 
               | What's the element I'm missing as to why they didn't?
        
               | inglor_cz wrote:
               | Pre-industrial holes may collapse long before you reach
               | -100 meters. Even -5 meters is a challenge in certain
               | places.
               | 
               | Also, digging (or rather drilling) in bedrock is hard
               | without motorized equipment and good steel.
               | 
               | Also, supplying fresh air down there is a problem.
               | 
               | Also, preventing the mine from flooding is usually a huge
               | problem.
               | 
               | Mining is hard and a lot of people lost their lives doing
               | that. That said, if your only intent is to get a bit
               | warmer, you may basically try a good cave. Caves tend to
               | have temperatures above freezing for the whole year.
        
               | nervousvarun wrote:
               | And of course the difficulty with caves is hibernating
               | predator(s) (bear is the one I can think of maybe more?)
        
               | inglor_cz wrote:
               | And lions:
               | 
               | https://en.wikipedia.org/wiki/Panthera_spelaea
               | 
               | IDK if these lions hibernated, but their bones are
               | definitely found in caves all over Europe. Often with
               | human remains or artifacts nearby.
        
               | WiseWeasel wrote:
               | Difficulty of digging with the tools they had, inability
               | to stabilize the structure to prevent cave-ins, lack of
               | pumps to remove accumulating water, insufficient
               | ventilation and filtration technology/unable to deal with
               | poison gases, inability to light their environment
               | without contributing to the poor air quality, difficulty
               | accessing resources like food and clean water, lack of
               | desire to live in a damp, dusty hole.
        
               | Ekaros wrote:
               | Also for example Finland can be at least in north
               | considered harsh climate. But these are also areas that
               | suffered of ice age that scrapped most of the softer
               | rocks away leaving only the tougher stuff like granite.
               | Which makes digging very difficult, specially pre-
               | industrial times.
        
               | sulZ wrote:
               | Digging 100m down is difficult and dangerous
        
               | PixelOfDeath wrote:
               | Ever tried to dig down a few 100m in your garden?
        
               | m4rtink wrote:
               | Try 390m, by hand:
               | 
               | https://en.m.wikipedia.org/wiki/Woodingdean_Water_Well
        
               | mikewave wrote:
               | More like, ever tried to dig down more than a foot or
               | two? Unless you have really soft ground, even a good
               | steel spade and shovel aren't any guarantee of success.
               | Powered augers are often needed to make holes for fence
               | posts, etc.
        
               | cortesoft wrote:
               | That it is really hard to dig down 100m without modern
               | digging equipment.
        
               | Melatonic wrote:
               | Do you have a source for that increase? I was not able to
               | find it. Seems very suspect considering that the earths
               | outer crust is approximately 20 to 30 miles thick. Are
               | you suggesting that if we go approximately halfway
               | through the outer crust, say 15 miles, the temperature is
               | going to be 725 degrees warmer than surface temp?
        
               | wcoenen wrote:
               | Page 62 of https://archive.ipcc.ch/pdf/supporting-
               | material/proc-renewab...
               | 
               | > _The heat is transferred from the interior towards the
               | surface mostly by conduction, and this conductive heat
               | flow makes temperature rise with increasing depth in the
               | crust on average 25-30degC /km_
        
               | count wrote:
               | https://www.nationalgeographic.org/encyclopedia/crust/
               | 
               | Not sure about the rate per-mile, but literally it's that
               | hot, yes, but not even 15 miles. Just down 5-7km under
               | the oceans, for example at the Mohorovicic discontinuity
               | the temp ranges from 392 to 752F.
        
               | Melatonic wrote:
               | Under the ocean is already much, MUCH closer however to
               | the mantle. Oceanic crust is drastically thinner than the
               | land we walk on.
               | 
               | In the Nat Geo article they quote a mine in South Africa
               | reaching up to 55C (131 F) at the bottom and the mine is
               | 4km deep. At a rate 3 degrees Celsius per 100m it should
               | be 120 degrees Celsius over ambient. Which obviously does
               | not add up.
        
               | m4rtink wrote:
               | They reached 160C rock when building an industrial
               | railway in Japan:
               | 
               | https://en.m.wikipedia.org/wiki/Kurobe_Seny%C5%8D_Railway
               | 
               | Cooled down to 40C since the 60s.
        
               | andrewflnr wrote:
               | Have you been in a cave? They're chilly, usually around
               | 50F, year round. IIRC those "deep mines" are a LOT deeper
               | than any compressed air storage system is likely to be.
        
             | JohnL4 wrote:
             | "Looked the temp gradients up, after 50ft, temp of the
             | earth is 50F, and raises one degree F every 60ft." (So, at
             | 300 feet, 54 degrees; at 500, 57.5 degrees.)
             | 
             | (http://www.welshcoalmines.co.uk/forum/read.php?14,46717,46
             | 71...)
             | 
             | "...but other parts of the mine was very cold you made sure
             | you had plenty to ware it depended where you worked"
             | 
             | (https://www.quora.com/Are-coal-mines-cold/answer/Keith-
             | Scott...)
             | 
             | "Underground mines maintain a constant temperature, around
             | 55 degrees Fahrenheit."
             | 
             | (https://www.quora.com/Are-coal-mines-cold/answer/Tom-
             | Inghram)
             | 
             | <<The temperature on average is in the 50s, but you still
             | sweat an enormous amount when you start laboring." - Alan
             | Bates, working in the coal mines of Letcher County,
             | Kentucky.>>
             | 
             | (https://www.quora.com/Whats-it-like-working-in-a-coal-
             | mine/a...)
             | 
             | Yes, a 4000m gold mine is hot. I doubt that's where they're
             | storing their compressed air.
        
             | benreesman wrote:
             | This comment is an example of why I've become skeptical of
             | the downvote button. It sounds like people read it, knew
             | better, and politely pointed out that it was incorrect.
             | 
             | Everyone who might have shared the same misapprehension
             | learned something and the parent wasn't being an asshole.
             | 
             | Doesn't that add to the discussion?
        
               | ndm000 wrote:
               | Side question - do you need to reach a certain level of
               | membership with HN to see the downvote button? I may be
               | missing something, but seems that's only allowed for
               | certain individuals.
        
               | nkurz wrote:
               | Yes, there's a minimum number of points required to
               | downvote. I think it's currently 500. Here's an
               | unofficial FAQ that give more information about the
               | thresholds: https://github.com/minimaxir/hacker-news-
               | undocumented/blob/m...
        
               | nautilius wrote:
               | Didn't downvote, but I am not a big fan of simply making
               | stuff up on the fly as response. I've met my share of
               | people who rather go this route than put in a 5sec Google
               | search or simply admit they don't know something, and I
               | try to avoid them.
        
               | nkurz wrote:
               | Yes, when considered along with the corrective responses,
               | it adds to the discussion. This is why it shouldn't be
               | flagged and removed. On the other hand, it's factually
               | wrong and would be misleading if people were to trust the
               | claims uncritically, which I think justifies a downvote.
               | Keeping it visible but lower on the page and showing it
               | in gray seems like a pretty good compromise. Can you
               | suggest a better way of giving more prominence to correct
               | information? Or do you think that's not the right
               | priority for the site?
        
           | [deleted]
        
           | notatoad wrote:
           | what would be the benefit to it being heated by the earth
           | during storage?
           | 
           | all the temperature management here looks to just be
           | counteracting the temperature changes that naturally occur
           | when you compress or expand a gas. i imagine if you
           | compressed it and then pumped hot air into water-filled
           | caverns you'd get some negative effects of thermal shock.
        
             | locuscoeruleus wrote:
             | Wouldn't the cooled down gas expand when heated leading to
             | higher pressure, so you need to pump gas down?
        
             | halpert wrote:
             | Hot air should have higher pressure, so theoretically you
             | could get more displacement. But your pumps also have to
             | work harder to create a pressure differential. Hard to say
             | which effect would be bigger.
        
         | sauwan wrote:
         | Is the voice in that video AI generated?
        
         | laputan_machine wrote:
         | The big question is how on earth are they digging out these
         | caverns? That seems like a huge challenge, given that they're
         | so far underground. Everything else seems relatively
         | straightforward
        
           | [deleted]
        
           | rplnt wrote:
           | It says repurposing old mining operations. Not sure how
           | feasible that is.
        
             | ed_balls wrote:
             | I had a similar idea for repurposing an old mining
             | operation. You take a closed gold, uranium or copper mine
             | which is 1000-2000 meters deep. You create a nuclear rector
             | at the bottom with "fire and forget" design. Only robots
             | can do the maintenance. After 60 years you disable it, pour
             | concrete into the shaft and move to the next location. If
             | it melts, who cares? It's not gonna poison water supply.
             | 
             | Why was this not built before? I have no idea. Maybe robots
             | are essential, we didn't have deep enough mines that were
             | abandoned, energy was cheaper, no push for no emissions,
             | it's not economical, other risks.
        
               | deeviant wrote:
               | The footprint of a nuclear power plant is pretty huge.
               | That machinery is generally not optional even if doing a
               | "fire and forget" design. Underground space would come at
               | a premium cost, likely far more than could be saved on
               | reactor design.
               | 
               | Also nuclear power plants obviously generate an
               | absolutely massive amount of heat that needs to be
               | dissipated, a task that would be difficult and expensive
               | underground.
        
               | VTimofeenko wrote:
               | inb4: not a specialist. AFAIR remote control robots were
               | tried when Chernobyl disaster was being cleared up, and
               | the radiation destroyed the electronics. But perhaps the
               | shielding technologies progressed enough to mitigate
               | that.
               | 
               | Having nuclear stuff underground requires extremely
               | precise geological surveys, so that the stuff does not
               | wind up in aquifer.
        
               | creato wrote:
               | You need a hot _and_ cold reservoir to generate power.
               | Where is the heat going to go? This is why power plants
               | are often built on rivers or near the ocean.
        
               | ed_balls wrote:
               | you need to pump water, probably flooding 80% of the
               | mine. Since there are no humans involved 70+ celsius is
               | not a problem.
        
               | VTimofeenko wrote:
               | The heat still has to be managed, otherwise Kyshtym[1]
               | happens. 160 tons of flying concrete is no joke.
               | 
               | https://en.m.wikipedia.org/wiki/Kyshtym_disaster
        
               | laurent92 wrote:
               | In France we're storing highly radioactive items
               | underground. Here is how dissipation works:
               | 
               | - After a few dozen years, the concrete is expected to
               | breach,
               | 
               | - Radioactive atoms mix up with soil and dissipate both
               | upwards and downwards, mostly thanks to water,
               | 
               | - After 400 years and for thousands of years, they reach
               | the surface, where they should be diluted enough to not
               | be dangerous,
               | 
               | So I guess having badly contained radioactive containers
               | would be much worse.
               | 
               | One thing to remember is that pressure underground is
               | extremely high (stone weighs a lot more than water, and
               | light rock tends to "float" onto denser rock). If a
               | melted reactor were squeezed, it would spread materials
               | into the soil much quicker.
        
           | crunchyfrog wrote:
           | Shaft mining is often used to reach underground deposits of
           | iron, coal, etc. I believe they'd use the same process here.
        
           | buryat wrote:
           | lots of mining caverns already had pressurized gas that was
           | extracted, so those caverns are pretty tight to pump back
           | some air
        
       | seedragons wrote:
       | Not a single "hot air" joke? Not sure to be impressed everyone's
       | more mature than me or disappointed.
        
       | reedf1 wrote:
       | Given it's GS, $250m is peanuts.
        
         | 1-more wrote:
         | > Goldman Sachs agreed and invested $250 million from its
         | private equity division.
         | 
         | Maybe they're referring to Goldman Sachs Capital partners which
         | has 39.9B[0] under management which means this is 0.62% of
         | their portfolio. In a totally chalk and cheese comparison that
         | would be having 200k in your 401k and taking a $1,250 position
         | in a stock, which isn't nothing but is a pretty small bet, I
         | agree. Curious though if I'm guessing the part of GS correctly;
         | I have no idea how they're structured and just spent like three
         | minutes searching.
         | 
         | [0]
         | https://en.wikipedia.org/wiki/Goldman_Sachs_Capital_Partners
        
         | woofcat wrote:
         | I see that you've been down-voted however they have 40 billion
         | in assets under management.
        
           | WHA8m wrote:
           | I didn't dv, but that'd be .63%. That's not peanuts I'd
           | say...
        
       | epistasis wrote:
       | Grid storage is going to be big business in the future, on the
       | order of size of storage for electrical vehicles. (And these will
       | certainly not be mutually exclusive markets! Vehicle to grid tech
       | will become widespread, as is already seen in the new F150
       | Lightning truck). Lithium ion will dominate for the foreseeable
       | future, as the industry has scaled to massive sizes and already,
       | and has the advantage of being currently unstoppable in the EV
       | space.
       | 
       | Batteries with a design that can decouple the energy from the
       | power ratings, like this one, will be able to address parts of
       | the market that lithium ion cannot. And if the cost per MWh of
       | additional energy is cheap, and round trip efficiency stays above
       | 50% or so, that sort of battery will have a huge edge in a part
       | of the market that currently has no clear winners.
       | 
       | There are many competitors in the non-lithium ion storage space,
       | but one of the top contenders to watch is Form energy, which has
       | a rust-based battery, and is rumored to have a cost as low as
       | $20/MWh, about a tenth of that of lithium ion.
        
         | buryat wrote:
         | > Grid storage is going to be big business in the future
         | 
         | it's already a big business
        
         | octo_t wrote:
         | Seems like everyone wants to make everything in Rust these
         | days! /s
        
         | samstave wrote:
         | Isn't Afghanistan known to be sitting on top of ~1 trillion$
         | worth of lithium, and also Bolivia?
        
           | czbond wrote:
           | I still believe that's why the U.S. invaded anyway. We didn't
           | care about overtaking a country for some silly resistance
           | leader. You do it for big money to bilk - like Iraq and oil.
        
             | maybelsyrup wrote:
             | Like others I don't think that that's why the US invaded,
             | but I do think it had something to do with the enormous
             | shit-fit thrown by the DC foreign policy / national
             | security / defense commentariat when we pulled out of
             | Afghanistan last summer.
        
             | nradov wrote:
             | Unlikely. When the USA invaded Afghanistan in 2001 no one
             | was really sure whether lithium batteries would be the
             | right technology.
        
             | abakker wrote:
             | But we left without taking any lithium. At some point
             | second and third order hypotheticals are just conspiracy
             | theories. There is no evidence we invaded Afghanistan to
             | get lithium, and at the time (2001), we were not worried
             | about lithium shortages or grid storage.
        
         | EricE wrote:
         | Lithium Ion is not sustainable for the long term - we have
         | neither the materials nor the manufacturing to not only keep up
         | what would be required for full scale car and grid uses, but
         | don't forget Lithium Ion batteries have a finite lifespan and
         | need to be replaced. The more you put into service, the more
         | you have to manufacture beyond just the batteries needed for
         | new requirements.
        
           | epistasis wrote:
           | I'm not sure that your predictions will hold here. More
           | lithium is discovered as demand grows, and there have been
           | huge additions to known reserves in just the past few years.
           | Looking at current numbers and saying "that's it" is clearly
           | wrong, and given its overall abundance and lack of demand
           | until now, it's a really strong prediction to say that we
           | won't have enough for at least 500TWh of storage, if not
           | more.
           | 
           | Manufacturing capacity is expected to increase 10x every five
           | years, with roughly 20-30TWh/year production in 2031. I can't
           | think of any fundamental constraints there, could you specify
           | why that can't increase?
           | 
           | Lithium recycling is being planned by nearly all
           | manufacturers and many countries will mandate it. If lithium
           | supplies are short, recycling will be highly profitable. If
           | lithium is super abundant, recycling may be more expensive
           | than recycling, and a program like what we currently use for
           | lead acid batteries might be needed for a circular economy.
           | But the fundamental point is that end of life for the battery
           | does not mean that the lithium is gone, it's not a fuel.
           | 
           | How did you collect this odd set of concerns? Did you think
           | of them or did you find them in the media somewhere?
        
             | EricE wrote:
             | It's all a question of economics. I think technologies like
             | the one in this article, or the one I think holds the best
             | long term promise - super capacitors - are far more likely
             | to displace lithium ion batteries before all that
             | infrastructure you describe scales out. Recycling a battery
             | pack out of a car like a Tesla is far different than
             | recycling a traditional led acid battery from a car.
             | Recycling the quantity of batteries required to support the
             | grid at scale is even more of a non-trivial problem. And if
             | recycling isn't economically viable because lithium is so
             | abundant what do you do with the spent batteries? Bury
             | them?
             | 
             | Especially for electric cars - without something like a
             | supercapacitor or hydrogen that can charge quickly and
             | doesn't have massive battery pack replacement costs built
             | in to the total cost of ownership equation, electric cars
             | are not going to become mainstream; they will remain fringe
             | oddities.
             | 
             | FYI if you aren't aware of super capacitors there has been
             | significant progress in bringing them to scale:
             | https://undecidedmf.com/episodes/revisiting-the-
             | supercapacit...
             | 
             | I don't think Lithium is going away tomorrow - but I think
             | it's crazy to bank on it for all our future needs or pitch
             | it for grid storage. If it was so viable for grid storage
             | then where are the really large deployments at scale? As
             | you point out its mature tech. Someone would have scaled up
             | production and done it already if it was such a no brainer.
             | If Elon thought he could make more money at it than cars or
             | space do you not think he would already be there focusing
             | on it vs. those other ventures? Heck at one point Elon was
             | thinking of doing his own candy but didn't since he didn't
             | find anything really revolutionary enough to separate his
             | potential offering from what was already out there. So it's
             | not like he has a super narrow focus only on what he's
             | already working on, and he already has a ton of in-house
             | knowledge about lithium ion batteries.
             | 
             | That a company with as high knowledge of lithium battery
             | tech like Tesla is only tangentially focused on grid power
             | solutions instead of heavily diving in is, I think, one of
             | the larger tells out there. And do you think Tesla would
             | still be as successful if it didn't have substantial tax
             | incentives? That's a distortion that's often overlooked
             | when talking about overall economic viability.
             | 
             | There is far more than just raw resource availability or
             | basic manufacturing capabilities at play here - and grid
             | scale requirements just amplify those issues. I dunno why
             | so many people are so eager to hand wave the limited
             | lifetime of chemical batteries but it's a significant
             | issue; any tech that doesn't have 100% replacement over a
             | short fixed lifetime is going to beat the pants off of
             | chemical batteries over the long haul. It isn't even
             | remotely close. Utilities think in 50 year lifetimes, not
             | 5. These aren't solutions for cars; this is base
             | infrastructure that's COSTLY. There is probably some
             | maintenance with these compressed air solutions, but I'm
             | pretty confident it's no where near that of being forced to
             | replacing the most expensive part of your entire storage
             | solution every X years.
             | 
             | Just look at the value of a used electric cars vs. new. As
             | people are learning about battery pack replacement costs or
             | especially with Tesla, limited options on repair/partial
             | replacement and probably loosing access to
             | supercharging(one of the biggest reasons to pick Tesla
             | right now), used prices on electric cars have steadily
             | declined (and that's being a bit polite). When you have
             | someone blowing up a used Tesla because they feel it's not
             | economically viable to replace the battery pack, that' an
             | issue that shouldn't just be hand waved away
             | https://carbuzz.com/news/fed-up-tesla-owner-blows-up-his-
             | mod...
             | 
             | All of this is in its infancy, but chemical batteries are
             | already in a pretty deep hole from an economics
             | perspective. Unless there is a breakthrough on preventing
             | dendrite formation that dramatically (dramatically!)
             | increases the lifespan of chemical batteries they are a
             | transitory but not long term solution.
             | 
             | Supercapacitors aren't without their issues. You can fill
             | them up instantly (if you have the means to move that much
             | energy that quickly!) but they can also discharge all their
             | energy instantly - which is a great way to also describe a
             | bomb. So things like that will have to be worked out to
             | make them safe - but I see that as far less of a problem
             | than dealing with the perpetual churn of chemical
             | batteries.
        
         | KennyBlanken wrote:
         | > one of the top contenders to watch is Form energy, which has
         | a rust-based battery.
         | 
         | Form is still in the cell prototyping stage, as best I can tell
         | - maybe not even that. There's zero information on their
         | website about where they are in the development process or
         | really anything substantial about their design.
         | 
         | ESS on the other hand has a design they've had out testing in
         | the field for a couple years ( https://essinc.com/ess-inc-to-
         | deliver-two-energy-warehouse-s... is one such location) and has
         | been shipping actual product:
         | https://www.businesswire.com/news/home/20211115006337/en/ESS...
         | and they've been pretty open about their design, though some of
         | their old whitepapers have been removed from the site.
         | 
         | Competition in the market is certainly a good thing, but Form
         | needs to do more than just have a shiny website, a screengrab
         | of a zoom employee meeting, and a blog with 'industry insight'
         | posts (because they have nothing to show for tech/product.)
        
           | epistasis wrote:
           | Agreed that Form has lots of hype, but that's one thing that
           | can be needed in addition to working tech. Utility decision
           | makers are not the best at adding new tech to the grid or
           | dealing with innovation. Having some big industry names and
           | the support of the business press that the utility execs and
           | shareholders read is it's own form of currency when dealing
           | with such archaic businesses.
        
         | Melatonic wrote:
         | I have been saying for years that we should have a windmill
         | system you could place on top of a building or home that powers
         | a larger, highspeed flywheel buried underground below the
         | house. Ideally with the flywheel in vacuum and balanced by
         | magnets for reduced friction. This ensures no loss converting
         | energy types (mechanical to mechanical) and it can be used
         | later for electricity or other energy in small, large bursts
         | (sort of like a capacitor). You would still want batteries for
         | energy storage but this would drastically increase the lifespan
         | of those batteries by reducing stress on their chemistry.
         | Batteries really do not like to discharge in short, high
         | intensity bursts. There are flywheel based UPS systems that
         | work sort of in a similar principle and they have much longer
         | maintenance intervals vs a battery type UPS>
        
           | epistasis wrote:
           | I think both battery and solar tech has advanced to the point
           | that solar plus batteries undercut a lot of grid supplied
           | energy in costs.
           | 
           | Or at least it would, if the overhead for current solar
           | installers wasn't so high. Retail prices for equipment are
           | incredibly low, but the boom-and-bust cycle caused by
           | uncertain regulatory terrain ends up requiring successful biz
           | to have massive marketing costs, which results in really high
           | prices overall.
        
           | WheatM wrote:
        
       | 2OEH8eoCRo0 wrote:
       | Has anybody considered building flywheels into each wind turbine?
        
         | toss1 wrote:
         | Interesting question, but seems unlikely.
         | 
         | If you're thinking of a direct mechanical linkage, you wouldn't
         | want to put it up on the tower because the mass to effectively
         | store megawatt-scale power is way more than you'd want to
         | support up high. Also, since the wind blade usually swivels to
         | the wind, you'd want to avoid the rotational inertia. So, you'd
         | need a mechanical linkage to transmit the power to the ground,
         | maybe installing it under the tower base.
         | 
         | You would not want to use a direct mechanical attachment, i.e.,
         | resembling a combustion engine - transmission flywheel, because
         | this would impair the ability of the wind turbine to start.
         | Generally, turbines are designed for minimum inertia to easily
         | start in low-wind conditions. A direct connection would impede
         | that.
         | 
         | Now, we're adding a clutch-sort of mechanism, and that has its
         | own additional complexity, weight, and energy.
         | 
         | Moreover, considering that we're trying to store megawatt-scale
         | energies, we are at a large mass spinning very fast, and
         | probably spun up with an electric motor.
         | 
         | So, it would seem the best way to do that would be to make a
         | flywheel farm, with the flywheels below ground to contain
         | failures. At this point, why locate it in the probably
         | inconvenient location where the wind turbines are located, and
         | instead put it somewhere more convenient, such as nearer to the
         | consumption areas?
        
         | buryat wrote:
         | flywheels storing a lot of energy are very dangerous, if
         | something happens it's a flying thing that destroys everything
         | on its way
        
           | 2OEH8eoCRo0 wrote:
           | Like a giant rotating wind turbine?
        
             | toss1 wrote:
             | Yes, except with several orders of magnitude more energy
             | and rotating mass.
             | 
             | Wind turbine blades are engineered for minimum mass and
             | inertia, are manufactured primarily from fiberglass and/or
             | carbon fiber, are hollow, and the largest mass is in the
             | center.
             | 
             | In contrast, flywheels are engineered for the highest
             | practical inertia, are manufactured from the highest
             | density material that works, and concentrate that mass as
             | far out as possible.
             | 
             | When a wind blade fails catastrophically, it makes a mess
             | of splinters right around the tower, as shown in [0] and
             | [1].
             | 
             | In contrast, just a small automotive flywheel explosion,
             | contained in a legally mandated scattershield, is almost as
             | spectacular [2], [3]. Now, magnify that from a flywheel
             | just designed to smooth the power from a 375kW (500HP)
             | engine to the scale of a flywheel to STORE the energy of a
             | megawatt-scale wind turbine.
             | 
             | So, no, the danger of a megawatt-scale energy storage
             | flywheel is NOT like the danger of a "giant rotating wind
             | turbine".
             | 
             | [0] https://www.youtube.com/watch?v=M-o-4yYb59g [1]
             | https://www.youtube.com/watch?v=sbCs7ZQDKoM&t=40s [2]
             | https://www.youtube.com/watch?v=kPat3akDiek [3]
             | https://www.youtube.com/watch?v=f4oxoBKRZgA
        
               | mygoodaccount wrote:
               | [0] is a doctored video. Go frame by frame just before
               | explosion and watch tracking of horses. [1],[2],[3] is
               | real
        
             | buryat wrote:
             | i agree, wind turbines do rotate but not at high speeds,
             | disintegration of one doesn't lead to catastrophic
             | outcomes. Flywheels on the other hand are meant to rotate
             | at high speeds and hold lots of energy, so destruction of
             | the spindle would lead to some pretty big bad results
        
               | PaulDavisThe1st wrote:
               | This sounds like a perfect question for Randall "XKCD"
               | Munroe's "What If" column:
               | 
               | " _What if_ a 5MW flywheel broke it 's spindle?"
        
         | lbriner wrote:
         | I'm not sure how that would help? If you had a flywheel and you
         | didn't need the energy, what do you do with it? At least
         | without a flywheel, you can easily stop the turbine.
         | 
         | Also, any flywheel that would add significant difference would
         | probably weigh hundreds of tonnes, which would make
         | construction massively more expensive and difficult.
        
           | 2OEH8eoCRo0 wrote:
           | If you don't need the energy you just let the flywheel spin
           | freely. It's a mechanical battery. I agree with your second
           | point though- it would add considerable mass to the hub
           | assembly of the wind turbine and there is no clear way to
           | transmit the mechanical energy to ground level.
        
       | Murkin wrote:
       | Can someone explain why this is better than just using pumps to
       | pump water up from the reservoir and extract the energy with when
       | the water returned back?
        
         | buryat wrote:
         | not a lot of places have enough terrain to create a lake, plus
         | in some places there's already shortage of water so removing it
         | from usage would be pretty bad
        
         | reincarnate0x14 wrote:
         | It's not, but it doesn't require a giant reservoir next to a
         | 100m+ elevation change. Almost all of the really good locations
         | for dams already have them, and their water discharge rates are
         | driven by a lot more than just power generation.
        
         | tristor wrote:
         | It requires less surface area, both due to compressibility and
         | due to hydrodynamics. Additionally, water is a strong erosion
         | source, air is not, so this can make use of existing
         | excavations much easier and deep excavation is very very
         | expensive.
        
         | hannob wrote:
         | Pumped water only works if you have the right conditions. I.e.
         | you need a certain altitude difference and enough space to have
         | an upper and a lower water storage facility.
         | 
         | Pumped water storage is very efficient and an established
         | technology, so when it's possible it's a good choice, but it's
         | not possible everywhere.
        
       | photochemsyn wrote:
       | It's probably some kind of hedge strategy for energy crises like
       | the recent Texas disaster (which appears to have been very
       | profitable for GS [1]). Having this capacity around when other
       | sources go down means they'll be able to provide power in similar
       | situations and so reap massive profits. Climate chaos == $$$ I
       | guess.
       | 
       | > Bloomberg March 5, 2021
       | 
       | > Goldman Sachs Group Inc. could gain more than $200 million from
       | the physical sale of power and natural gas and from financial
       | hedges after spot prices surged across much of the U.S.,
       | according to people with knowledge of the matter. Morgan
       | Stanley's gains could come in under $200 million, according to a
       | person with familiar with the matter, and Bank of America Corp.
       | stands to rake in profits as well...
       | 
       | > The historic cold that battered the central U.S. last month led
       | to sweeping blackouts as ice formed on wind turbines and
       | pipelines froze, forcing oil and gas wells to shut. As traders
       | and power suppliers struggled to find fuel to meet obligations,
       | prices skyrocketed. In Oklahoma, gas traded at more than 300
       | times normal levels, while electricity in Texas surged to $9,000
       | per megawatt-hour.
       | 
       | Full article: [1]
       | https://www.investorvillage.com/smbd.asp?mb=5028&mn=126049&p...
        
         | qeternity wrote:
         | > Having this capacity around when other sources go down means
         | they'll be able to provide power in similar situations and so
         | reap massive profits. Climate chaos == $$$ I guess.
         | 
         | I understand that people don't like when others profit from a
         | crisis, but this is also how we solve these problems. Having
         | more generation capacity than we otherwise would have is a good
         | thing, even if Goldman make money on the back of it.
         | 
         | I'm not arguing there isn't more to be done, but when people
         | say "greed is good" this is what they mean.
        
         | igammarays wrote:
         | This is where capitalism goes off the rails. Instead of
         | investing $250m into making the power grid more secure and
         | reliable, they choose to invest in profiting off disaster.
        
           | jvanderbot wrote:
           | providing instant-on, scalable energy capacity to the grid is
           | _both_ potentially profiting off disaster _and_ investing
           | 250m into making the grid more reliable and secure.
        
           | EricE wrote:
           | As others said, energy storage technology is going to be the
           | only thing that makes renewable energy more than a curiosity.
           | Renewable energy is neither reliable nor predictable which is
           | why it can not replace base load requirements.
           | 
           | However, if we had sufficient energy storage capacity, they
           | we could indeed fully transition to renewable energy once and
           | for all!
        
           | epistasis wrote:
           | You are sorely mistaken, this sort of battery is _exactly_
           | what makes the grid more reliable and secure. Especially on
           | grids like Texas, which have massive amounts of renewables.
           | 
           | Batteries are the Swiss Army knife of the grid, they can fix
           | all sorts of problems, from inadequate transmission capacity,
           | to frequency regulations, to peaking needs.
        
       | throw1234651234 wrote:
       | Heh. This ties in with the "Amish Hackers" article here:
       | https://news.ycombinator.com/item?id=29905288, which states that
       | the Amish use compressed air to store electricity.
        
       | hannob wrote:
       | Interesting.
       | 
       | The German energy company RWE has announced a while ago that they
       | want to build a compressed air storage facility. However the
       | project went nowhere and was silently buried at some point.
        
         | EricE wrote:
         | Preventing air leakage is frightfully hard - air molecules are
         | a lot smaller than liquid molecules :)
         | Apparently these guys have found an economical way to deal with
         | it.  If true then I can easily see why Goldman jumped on them.
        
       | escapecharacter wrote:
       | Ah, FartTech
        
       | surfmike wrote:
       | This made me wonder what happened with LightSail energy, and
       | found this takedown:
       | https://www.greentechmedia.com/squared/letter-from-sand-hill...
       | 
       | Compressed air still seems like a promising idea to help solve
       | the scale of energy storage we need, so I'm happy to see more
       | companies taking a crack at it.
        
         | [deleted]
        
       | boringg wrote:
       | GS isn't known for their scientific prowess - signal that they
       | believe there is money in large scale ESS. Not sure if it's
       | validating the technology at all though. Compressed air has been
       | around for a long time at this point.
        
         | objektif wrote:
         | Who is known for their scientific prowess? A16z and with
         | sprawling investments in web3? Capital is capital. We should be
         | cheering on these types of investments regardless. Electric
         | motors have been around for a looong time as well..
        
           | boringg wrote:
           | The VC and investment world in energy technology is quite
           | different then the A16z and traditional VC world or financial
           | heavyweights.
           | 
           | Having had GS invest in companies in the energy tech space in
           | the past and having not particularly great success - I
           | wouldn't think this is a strong signal. More that the
           | financial heavyweights think there is action and they want to
           | get in.
        
             | objektif wrote:
             | Goldman has army of analysts that are covering the field.
             | Many many more than Even VCs that specialize in it. I would
             | definitely write them off when it comes to smart investing.
        
               | boringg wrote:
               | Financial analysts != energy technologists with a
               | scientific background.
               | 
               | Its small money on a broad industry bet thats all in an
               | economy with very few quality investments available.
               | Don't read too much into it.
        
               | EricE wrote:
               | So you think it's in GS's best interest to make
               | uninformed decisions on a continual basis?
               | 
               | Seriously?
        
               | boringg wrote:
               | Never said it was uninformed. I was implying that this
               | really isn't a big deal except for the company who got
               | invested in.
        
               | boringg wrote:
               | Put another way it sounds like a corporate investor or VC
               | into an industry they know a little about but have heard
               | good things. Goldman Sachs is not known to be a good
               | energy investor. Who knows maybe now they are.
        
         | buryat wrote:
         | the governments should invest instead i agree but it doesn't
         | hurt if a private venture can help us all
        
       | Giorgi wrote:
       | I really enjoy learning about quirky ways to "store" energy,
       | there is also one case that allows "storing" of energy by pushing
       | massive concrete blocks uphill and when energy is needed, blocks
       | simply slide down and generate energy. Not sure if this can be
       | called "Storing" though.
        
         | konschubert wrote:
         | The more efficient version of this idea looks like this:
         | 
         | https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit...
        
           | EricE wrote:
           | It's only efficient if you have the right environment for it
           | to work (enough space, enough of an elevation gradient,
           | etc.).
           | 
           | If you can't build it where you need it, then efficiency
           | doesn't really matter now, does it?
        
           | s1artibartfast wrote:
           | I don't know that this is always the case. I think that solid
           | mass gravity storage projects have quite high efficiency.
           | 
           | there is no rule that water+ turbines is more efficiency than
           | Solid mass + alternators.
        
       | trembonator wrote:
        
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