[HN Gopher] Geothermal may beat batteries for energy storage
___________________________________________________________________
Geothermal may beat batteries for energy storage
Author : rbanffy
Score : 162 points
Date : 2022-10-11 09:21 UTC (13 hours ago)
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| [deleted]
| retrac wrote:
| The the ratio of area A to volume V for a sphere of radius R is
| 3/R. The larger the sphere, the less surface area to volume. A
| corollary of this is that a sufficiently large thermal tank has
| little in the way of heat loss to its surroundings in relation to
| its heat capacity.
|
| At large enough scale, it's probably the most efficient way to
| store energy for general heating purposes. Simple water has
| significant thermal capacity. 1 tonne (roughly 1 kilolitre, 1000
| litres) of water at 80 degC holds ~50 kWh of useful heat relative
| to normal indoor temperatures. Enough to heat a Canadian home
| overnight on a bad winter day and then some. 1 tonne of water
| isn't really that big; a typical car's interior volume would hold
| several tonnes of water. Home hot water storage, for heating over
| several days or a week, is quite viable with a large basement
| tank, and commercially available. Used with intermittent heat
| sources, and sometimes to save money when heat costs more at
| different times, like with electric time of use.
|
| A standard Olympic swimming pool holds several thousand tonnes,
| the largest indoor swimming pools tens of thousands of tonnes.
| 20,000 tonnes of water at 80 degC = about 1 gigawatt-hour of
| usable energy storage. Assuming no losses, That could heat many
| dozens of typical Canadian suburban homes all winter. What about
| _bigger_? Some lakes are so large their thermal capacity causes
| their temperature to significantly lag behind the seasonal
| changes, moderating the local climate. The largest fully
| artificial reservoirs are measured in cubic kilometres. That 's
| billions of tonnes. 1 cubic kilometre of hot water would have 30
| terawatt-hours or so. That's in the range of the yearly energy
| consumption of small cities. And at that scale, even a lightly
| insulated tank would lose an insignificant fraction of its heat,
| even over a timescale of months.
|
| Getting into less conventional territory, with much higher
| temperatures (perhaps a molten metal instead of water) and some
| real big tankers, it might be feasible to literally ship heat.
| This rarely made sense in the past except in some edge cases like
| using industrial waste heat. Fossil fuels were almost always the
| source of the heat to begin with. Just ship the fossil fuels. Far
| more energy dense and no conversion losses. But the economics are
| changing.
|
| (As an aside, the effect of the ratio of area to volume is just
| not intuitive to me, for some reason. But it's a very powerful
| scaling force in nature. It is why a bucket of water takes days
| to evaporate while tiny droplets of mist take seconds. Area for
| evaporation relative to volume. It even limits the maximum size
| of a terrestrial animal. Elephants push that limit. About a
| kilowatt just for base metabolism. In a thickly-walled airtight
| tank. A really big tank. They'd cook from the inside out without
| active cooling in a matter of hours. Their hearts are heat pumps
| and their ears are radiators.)
| bjourne wrote:
| > Assuming no losses, That could heat many dozens of typical
| Canadian suburban homes all winter.
|
| This honestly seem incredibly optimistic to me. Even a high-end
| thermos will lose its heat in less than a day. Faster in a cold
| environment. And afaik, temperature loss is proportional to
| temperature difference, so the hotter the liquid the faster it
| cools.
| retrac wrote:
| While literally zero loss is a violation of thermodynamics,
| with a really large tank and good insulation, it gets to
| self-discharge rates lower than most battery chemistries. A
| few percent per month. There's a small district heating
| system in Alberta driven with solar thermal power. It uses a
| large insulated soil heatsink. Most of the energy input is in
| the summer and it took four years to fully charge up to
| operating temperature. It holds enough heat to provide all
| required heating through the winter for ~50 large houses.
| pfdietz wrote:
| The thermal time constant for a sphere scales as radius
| squared (one factor of r due to volume/surface area, and one
| factor due to the temperature gradient scaling as 1/r). Your
| thermos is quite small.
| alfor wrote:
| EV batteries will store energy.
|
| As long as EV scale faster than solar/wind we will have little
| need for storage batteries.
|
| EV are moving in the direction of bidirectional charging and will
| thus become generator in peak demand period, the grid will become
| smarter and will offer differential price in function of
| offer/demand
| bjourne wrote:
| Arlanda airport outside of Stockholm uses a similar system:
| https://www.swedavia.com/about-swedavia/the-aquifer/ But in this
| case, the aquifer is naturally occurring and not man-made.
| Constructing underground aquifers requires a lot of energy so I
| wonder how many charge-and-drain cycles are needed before more
| energy is saved than spent.
| aaron695 wrote:
| Mrdarknezz wrote:
| Energy storage is the monorail of energy technology, expensive,
| unnecessary and conventional technologies like nuclear, hydro and
| geothermal is better in every regard.
| jandrese wrote:
| Nuclear has enormous political hurdles that translate into
| extreme project costs. Hydro and Geothermal are both
| geographically limited. Hydro especially is effectively tapped
| out at this point. You are chasing progressively less suitable
| locations for each install. Most of the best remaining places
| are far away from civilization and would require hundreds of
| kilometers of high tension wire to get to the nearest grid
| connection.
|
| Meanwhile battery prices are dropping year over year and
| installed capacity is still skyrocketing. Eventually the curve
| will level off, but we are not to the point of diminishing
| returns yet. Solar and Wind + Battery is shaping up to be the
| dominant power source of the future. It's all down to
| economics. Solar cells and wind turbines are not only getting
| cheap to buy, but once installed they require little
| maintenance and no ongoing fuel costs. Batteries are similarly
| low maintenance and the purchase price continues to drop as
| economies of scale and advances in technology make them cheaper
| and better.
| LinuxBender wrote:
| Many of the greenhouse Youtube channels I watch do a smaller DIY
| version of this. They have either dark barrels of water in the
| greenhouse with the windows facing south to the sun, or a thin
| metal wall filled with clay and pipes acting as a sun-heat-
| battery. They pump the water through the barrels or clay battery
| into pipes that are under ground to store the heat. In winter
| time they extract the heat from the ground keeping the greenhouse
| warm using a combination of solar and commercial power for the
| pumps. Heat is also extracted from compost bins at each end of
| the greenhouse. This works well in extremely cold climates in
| Canada and Alaska. A few of these folks do all of this without
| using any electricity at all and somehow manage to get water
| moving through the pipes using heat convection alone.
|
| I've been thinking about doing something like this but connecting
| it to pipes under the foundation of my home so I can get rid of
| the wallboard heaters or just leave them off. Electricity is the
| only commercial utility near me.
| m463 wrote:
| I remember reading about the enertia house, which had an
| interesting system.
|
| They used certain trees inside the house that would phase
| change at room temperature so would keep the temperature
| comfortable naturally.
|
| I think using a phase change is much better than just straight
| heating or cooling
|
| https://pogue.blogs.nytimes.com/2007/05/17/a-home-that-heats...
| JohnJamesRambo wrote:
| Can you share some of these greenhouse channels? I'd love to
| follow them to learn about how to better take care of my
| greenhouse.
| jonstewart wrote:
| It is probably far more cost effective to buy a new air source
| heatpump. They're so efficient and work well at low temps now.
| I have infloor radiant heat at a rural house in upper Midwest,
| have thought a lot about using solar heat pipes and adding a
| storage tank, and it's all so fiddly, pipes and pumps and
| manifolds and glycol and maintenance, all custom, all
| expensive. I'm almost certainly better off with PV panels and
| off the shelf heat pumps.
| xienze wrote:
| > They're so efficient and work well at low temps now.
|
| Can someone provide me model numbers for these heat pumps
| that "work well" at low temperatures? I've been through more
| than a few over the decades and currently have a Trane from
| last year and yep, still doesn't hold up very well once the
| temperature hits freezing. Don't get me wrong, I like heat
| pumps, but my eyes roll into the back of my skull when I hear
| over and over again that they're "so efficient now" at low
| temperatures.
| oittaa wrote:
| If you actually live in an area where temperatures drop
| below -30C regularly, you might want to consider a ground
| source heat pump. They are a bit more expensive than the
| typical air source heat pumps since there's some digging
| involved, but for a new house they aren't that much more
| expensive since there's already digging for electricity,
| plumbing, etc. For example ground source heat pumps are
| getting quite popular in Finland.
| xienze wrote:
| Who's talking about -30C? I'm talking about 32F, or 0C.
| I've yet to be impressed by a heat pump once the
| temperature gets at or especially below freezing.
|
| Geothermal heat pumps are great but at least in the US
| they are wildly expensive compared to traditional ones.
| You either need a large lot for horizontal laying of the
| pipe or a DEEP hole if going vertical ($$$). Plus they're
| uncommon enough that contractors are happy to charge a
| serious premium.
| jonstewart wrote:
| Fujitsu XLTH: https://www.fujitsugeneral.com/us/residential
| /technology/xlt...
|
| Mitsubishi Hyper Heat and H2i Plus:
| https://www.mitsubishicomfort.com/articles/what-is-a-heat-
| pu...
|
| Efficiency with these heat pumps severely decreases when
| temps go below 0F, but they still produce heat.
|
| Their sites are admittedly not all that clear.
| GreenBuildingAdvisor.com has a ton of useful info on it,
| like https://www.greenbuildingadvisor.com/question/cold-
| weather-p....
| 2Gkashmiri wrote:
| interesting. i have a PV system. i want to use the half
| installed central heating system (only piping laid down) (no
| boiler or FCU/room unit) and i have this crazy idea. use
| solar water heater to heat water, that feeds into a water
| storage tank, that water gets heated MORE by an air source
| water heater and a small circulation pump uses that water
| storage to heat the house.
|
| i am hoping, since we currently have 0 whole house heating,
| this would be better than nothing and the problem of not
| having consistent electricity to run the air source heat pump
| all times would be alleviated somehow by using solar water.
|
| is that crazy?
| mderazon wrote:
| I am currently looking to do something similar. I have zero
| heating in my house at the moment and have a 300L (65
| gallon) thermosiphon solar water heater [1] (tank plus
| panels all in one system) that gives me plenty hot sanitary
| water.
|
| I am looking to install an hydronic fan coil [2] radiator
| in my rooms and need water to heat them - I thought to use
| the excess heat from the solar heater to supply hot water
| to the fan coil units but I am not sure how do do that. If
| you have an idea, please share.
|
| 1. https://sol-aqua.com/thermosiphon-solar-water-heater/
|
| 2. https://www.arcticheatpumps.com/heat-pump-fan-coils.html
| jonstewart wrote:
| I assume you're on the grid?
|
| Yeah, sadly, it's crazy. Solar heaters are expensive and
| require a large area to get decent BTUs out of. If you can
| find free solar heaters that someone's giving away, that
| can make the difference, but they're often a few thousand
| dollars and that's about equivalent to a Fujitsu or
| Mitsubishi heat pump base install, especially when you
| factor in all the extra plumbing and pumps to/from the
| solar thermal array.
|
| WORSE, there's maintenance. You've got the potential for
| leaks (probability rises to 1.0 over the years), and you
| have to worry about the water freezing. That can be
| mitigated by using a glycol mix, but then you've got glycol
| and that lowers the efficiency.
|
| And then you have to think about climate. Is it reliably
| sunny in the winter? Or is it only sunny 1 out of 3 days,
| with long stretches of gray days? You are probably better
| off plowing that money into efficiency/insulation
| improvements to lower the overall heat load (and those
| improvements often have zero maintenance).
|
| I'd suggest looking into an air source heatpump that can
| produce domestic hot water, paired with a large storage
| tank. Check out Artic Heat Pumps:
| https://www.arcticheatpumps.com/
| jonstewart wrote:
| Oh, also: an air source water heater would need an external
| heat source--otherwise you've just made a closed system and
| won't be able to heat the house beyond what solar thermal
| provides, plus heat loss of the house.
| londons_explore wrote:
| Even a modern air source heat pump typically doesn't beat gas
| for $/kwh. Even in europe where gas prices are sky high,
| electricity still costs more when you look at the seasonal
| efficiency of heat pumps, which is typically advertised
| around 4.4, but various studies show that in most real world
| scenarios you typically won't reach the quoted lab numbers,
| so expect to get more like 2.5-3.0.
|
| Study: https://www.sciencedirect.com/science/article/pii/S037
| 877882...
| mint2 wrote:
| Claims like that really aren't helpful without numbers
| backing them up
|
| the cited paper gives the efficiency of heat pump but we're
| missing multiple crucial values to get from there to a
| comparison of heating costs
|
| Edit: https://great-home.co.uk/air-source-heat-pump-
| running-costs-...
|
| At current average British prices of 28p for electricity
| and 7p for gas, and using averages for both it looks like
| the commenter was mostly correct.
|
| Not 100% if the spf Gives the realistic cop
|
| In a new build that opted to forgo any gas connection, I'd
| be interested in seeing the costs from the substantial
| infra savings and hookup savings.
| dzhiurgis wrote:
| I read somewhere there's market failure too. Electricity
| price is largely proxy of gas price. While uk gov
| subsidises has they don't electricity...
| londons_explore wrote:
| From that paper, the average COP measured was 3.06
| (averaged between 2 and 7 degree outdoor temperatures,
| typical of the UK).
|
| The UK electricity price is currently fixed at 34p/kwh
| for electricity and 10.3p for gas.
|
| A new gas boiler has a COP(efficiency) of 1.054 (it can
| manage efficiency higher than 100% because gas is metered
| by the 'lower heating value', which assumes the exhaust
| gas escapes as steam, but the boilers actually condense
| most of that steam to water, getting additional energy
| out).
|
| So. Total price is: Gas: 10.3/1.054 = 9.77p/kwh in your
| home.
|
| Total ASHP price is: 34p/3.06 = 11.1p/kwh in your home.
|
| And this analysis ignores the fact that ASHP's typically
| have much worse efficiency making hot shower water (which
| a gas boiler doesn't), and obviously also have
| considerably higher upfront costs too.
| jandrese wrote:
| However, the ASHP can also be used to cool your home in
| the summer. In the past this has been a dubious benefit
| for most of northern Europe, but heat waves have been
| getting stronger, last longer, and happen more frequently
| as time goes on. This is turning into a serious
| consideration.
|
| Also, you can theoretically power a ASHP with renewable
| energy, while there are few if any carbon neutral
| replacements for natural gas.
| londons_explore wrote:
| Most boilers purchased today allow use with a Hydrogen
| mix, and some under development allow 100% hydrogen.
| Before the widespread extraction of natural gas, towns
| were powered with 'town gas', which is ~50% Hydrogen, so
| this is very much proven tech.
|
| There are a bunch of potential ways to make green
| hydrogen too.
|
| So, there very much is a path to green with a gas boiler.
| jandrese wrote:
| Green Hydrogen has not worked out so far. It is not clear
| that it even has a path forward. There are a lot of
| people hopeful that it will be a solution in the future,
| but as of today it is so uneconomical that even people
| willing to spend more to be green don't use it.
| teucris wrote:
| Thus the solar panels. So long as the installation proves
| to make financial sense, the PV production offsets the heat
| pump efficiency, even in winter months.
| londons_explore wrote:
| It would make even more sense to sell that power back to
| the grid, and then spend the $$$ earned on gas, which
| would work out cheaper overall.
|
| Obviously in many parts of the world, market distortion
| means the buy price and sell price for electricity is
| very different, and in that case a heat pump might make
| sense to combine with PV.
| jonstewart wrote:
| Exactly. Also, the top commenter noted that only
| electricity was available and currently was relying on
| massively inefficient baseboard heaters. Solar panels and
| heat pumps also have great rebate programs and eventually
| gas will be phased out. Some US cities are now banning
| gas on new construction in the near future.
|
| The point is that custom solar/geothermal installs seem
| neat and efficient --- waste not, want not -- but
| probably have a hard time competing with the economies of
| scale and low maintenance of PV panels and air source
| heat pumps.
| distances wrote:
| This may work in mild climates, but the areas where
| winter heating is most needed will have the solar panels
| under a bed of snow during the winter months.
|
| Additionally, winter months are usually the cloudy ones.
| It's not very uncommon to have just a couple of sunny
| days per month in European winters, driving down solar
| gains even if there's no snow cover.
| jws wrote:
| It's not as bad as this.
|
| In climates where you will have a bed of snow during the
| winter months, your optimum tilt angle for a fixed solar
| panel is something like 30deg off of vertical or steeper.
| I find that on mine the snow falls off since it is a
| south facing, steep, dark surface.
|
| You engineer to make sure you have enough energy captured
| each month to meet that months needs. That might lead you
| to a tilting mount, or just a fixed angle and having
| surplus energy most months.
|
| In my case, panels were much more expensive when I
| designed my system, I initially roof mounted them, but
| when replacing the roof under them I moved them to a pole
| and went with a tilting mount and manually move the
| panels twice a year. My load is much higher in the
| summer, but I still need some power in the winter. And
| northern winters can be cloudy a lot and have limited sun
| even on a clear day. At my location there is about a
| factor of 5 difference in solar energy per square meter
| per month. So you design for each month and then pick a
| solution that is best. In my case the summer load is so
| high that even though I get 5 times the energy, it is
| still the driving force on sizing the system.
| distances wrote:
| Interesting. Last winter my parents' rooftop solar had
| zero output until April, as it produces nothing until all
| the panels are clear of snow. Granted their installation
| is at a fixed angle that matches the roof, and this is in
| the Nordics.
|
| During summer months the production mostly covers and
| partly exceeds their use, but the sell price is so much
| lower that it doesn't even begin to pay for the rest of
| the year. But that of course then relates to the
| installed capacity.
| starlust2 wrote:
| They are on a pole on your roof or you moved them to the
| ground?
| jws wrote:
| I moved them to the ground. The roof pitch is about 1:1
| and I'm not feeling like trying to stick to it any more.
| The pole puts everything at a comfortable working height.
| jonstewart wrote:
| Selling PV electricity back to the grid is almost always
| many times worse, depending on state incentives, than
| consuming the electricity. For example, my utility sells
| electricity to me at 9 cents/KWh, but only buys from me
| at 2.5 cents, and charged me a fixed monthly fee for the
| meter to boot.
|
| If the commenter's house doesn't have gas, then it
| doesn't seem to make sense to install it, and the price
| differential in the US isn't as great as in the UK (how's
| that Brexit thing working out?).
| teucris wrote:
| Huh. We have a 1:1 credit system here in Washington.
| whafro wrote:
| And Massachusetts.
| cinntaile wrote:
| Considering solar owners are all pushing electricity onto
| the grid at the same time, when it is needed the least,
| such a system doesn't make sense. There are real costs
| associated with getting rid of all that unwanted energy.
| ridgeguy wrote:
| I think solar makes sense for most who use air
| conditioning. That's a load matched pretty closely to the
| timing of PV generation.
|
| Here in the Sierra foothills, it's been a blazing hot
| summer. About 90% of our PV generation powered our home
| air conditioning. We shipped very little energy to the
| grid on hot days. And it was awesome to have a
| comfortable environment without sucking grid power on the
| days when it hit 113degF.
| teucris wrote:
| > when it is needed the least
|
| I don't think this is true in many areas. In our area,
| during the summer the neighborhood is running A/C when
| the sun is at its peak. During the winter, heating. Also
| the transport loss from a power station is nothing to
| sneeze at - my understanding is that locally produced
| power often just results in reduced demand on the larger
| grid.
| smileysteve wrote:
| This seems like a (regulated) pricing error.
|
| There should be no economic way that a high efficiency
| turbine produces and distributes electricity to heat homes
| at a greater than 1:1 ratio compared to storing,
| pressurizing, and delivering, then burning in irregularly
| maintained consumer homes.
|
| Likely the error is that gas pipes to the house are
| subsidized (albeit the electrical likely is too, with heat
| pumps and induction stoves, the gas lines are unnecessarily
| redundant)
| dahfizz wrote:
| "high efficiency" turbines are not all that efficient.
| Burning gas releases 100% of the available energy as
| heat. Converting that gas to electricity is << 50%
| efficient. You also lose ~5% just transmitting the
| electricity to homes.
|
| Also, electricity from gas is relatively expensive. Other
| sources like coal or hydro are cheaper, which lowers the
| average cost of electricity.
| smileysteve wrote:
| But gas turbines should be more efficient than a burner
| under a boiler or a burner in a furnace.
|
| Yes, solar, wind, hydro, nuclear should be cheaper per
| unit (coal is not usually cheaper than gas in the US)
| dahfizz wrote:
| 95% efficient gas furnaces are the norm for newer
| houses[1].
|
| Getting electricity out of gas is fundamentally harder
| than getting heat out of it.
|
| [1] https://iwae.com/resources/articles/95-afue-gas-
| furnace-work...
| connicpu wrote:
| That's highly dependent on your local electricity and gas
| prices. A quick google search tells me residential
| electricity in Germany costs about 2-3x what it does where
| I live in the northwest US. We're on mostly government
| owned hydro power and electric prices have been stable for
| a long time, meanwhile gas keeps going up.
|
| EDIT: Did some quick math using my last power bill, at
| current prices a heat pump just needs to be about 2.9
| average COP to beat gas in cost for me, if gas keeps going
| up that'll keep dropping!
| titzer wrote:
| That's kind of disappointing news. I had a skim through the
| article and was surprised to find that it's all based on
| models. There wasn't a single empirical measurement of an
| installation of either kind. Not that I don't believe in
| modeling and its usages, but I am going to radically
| discount the findings of this paper because there was no
| actual experiment performed here, just fiddling with
| models.
| londons_explore wrote:
| Give it a re-read. They collected data from actual houses
| (although granted only 6 boiler-years worth of hourly
| data), then fitted a best fit model to that data, then
| used the model for their conclusions.
|
| They did that because they needed to compare the
| manufacturers datasheet lab figures to the real world
| figures, but there are 10+ variables that affect
| efficiency, and a direct comparison isn't possible unless
| all the variables match - hence using a model to act as
| the 'convertor'.
| cogman10 wrote:
| My uncle had a home like this built in the 70s. His whole home
| was solar heated.
|
| AFAIK, it worked pretty well year round.
|
| Solar heating is one of the most efficient usage of solar
| energy. The reason we don't generally do it more is because
| it's expensive and can be a headache to maintain (what happens
| when you spring a leak or your PVC pipes become brittle from
| sun exposure? Or when your heatbox ends up fogged or dirty).
|
| In that case, it can be a lot simpler to rely on heat pumps and
| geothermal energy storage.
| cookiengineer wrote:
| This reminds me a lot of the Earthship community in the middle
| of the desert, which always focusses on smart ways of reusing
| water for different purposes, and by not wasting water as much
| as possible. The houses usually have a clean/grey/blackwater +
| a rainwormbox system to process fecals and reuse it for growing
| plants. Their air conditioning system is basically just a pipe
| in the ground where the hot air flows through, cools down, and
| automatically gets pushed through the house when they open the
| windows on the roof.
|
| I was always wondering why there are no systems converting the
| unused electricity in potential energy by moving water to a
| higher ground. And more importantly: Why there are no water
| storages on the roof.
|
| [1] https://www.youtube.com/watch?v=wVp5koAOu9M
| dahfizz wrote:
| > Why there are no water storages on the roof.
|
| Quick math - 100 gallons of water 15 meters up off the ground
| has enough potential energy to run a microwave for 30
| seconds.
|
| Gravitational storage is pathetically weak. It only makes
| sense on massive, massive scales. In a residential setting,
| the storage will never outweigh the extra cost and risk of
| having so much water on your roof.
| rgmerk wrote:
| One minor but interesting exception - farmers have
| historically often put domestic water tanks on top of
| towers to ensure even water pressure. Direct pumping leads
| to cycles where the pressure in the system rises and falls
| as the pump cycles on and off, which is very unpleasant if
| you're trying to take a shower!
|
| I believe modern off-grid home water pumps use more
| sophisticated motor control to avoid the need for the
| raised tank.
| aappleby wrote:
| Off-grid domestic water uses tanks fitted with rubber
| bladders that keep the water at a roughly constant
| pressure and reduce the frequency the pump has to cycle.
| Dylan16807 wrote:
| That's not an exception, that's an entirely different use
| for a raised tank. And not a very big one either.
| sidewndr46 wrote:
| Secondary point: most residential structures are not
| designed to have 1000s or even 100s of gallons of water
| stored on the roof. Even 100 gallons is a huge amount of
| static load to add to a structure.
| soperj wrote:
| they do it a lot in NZ. Solar hot water heating.
| wharfjumper wrote:
| NZ has a lot of hydro and a reasonable amount of geo
| thermal generation. Solar, not so much.
| throw__away7391 wrote:
| Solar hot water is great, but that's not gravitational
| storage, e.g. pumping water up a hill with pumps and
| later using the flow of water back down to generate
| power.
| soperj wrote:
| You're right it isn't, but it is storing the water on top
| of the house.
| adamc wrote:
| Yes, but I'd expect it's much lesser amounts. 80 gallons
| is a decent sized water heater.
| biggoodwolf wrote:
| As commonly practiced in ALL sorts of places where houses
| are more than cardboard and some sticks. Ever read the 3
| piglets?
| chriswarbo wrote:
| > I was always wondering why there are no systems converting
| the unused electricity in potential energy by moving water to
| a higher ground. And more importantly: Why there are no water
| storages on the roof.
|
| Gravity is an incredibly feeble force, compared to
| electromagnetism (i.e. chemical bonds). Storing a practical
| amount of energy require a large mass x height.
| cogman10 wrote:
| > Why there are no water storages on the roof.
|
| Depends on the area, but sometimes collecting rain water is
| illegal.
|
| The other issue is that when dealing with rainwater, you need
| to clean it. Untreated, rainwater will likely develop a bad
| case of algae.
| lazide wrote:
| It's also really heavy - any amount likely to even light up
| a lightbulb for an hour or two would collapse a house
| without major reinforcement. Which would far outweigh any
| value of the storage.
| someweirdperson wrote:
| Water can freeze.
| psadri wrote:
| energy storage density of heating water >> lifting water.
|
| 1m^2 of water heated by 50C (20C - 70C) = 58KWh
|
| lifting 1m^2 of water by 10 meters (~ 3 stories!) = 0.03Kwh
| :-(
| psadri wrote:
| I think in the future we will see more homes with:
|
| Gray water recovery
|
| Thermal batteries (hot and cold)
|
| - Excess solar energy can be use to "charge" the hot or
| cold reservoirs for later use depending on season.
|
| Effluent heat recovery
|
| - Home appliances generate lots of heat (clothes driers,
| ovens, refrigerators, ...) that is currently vented to the
| atmosphere. Capture and use it to "charge" the hot battery.
|
| - I'd imagine a water (or other liquid) line that connects
| to each appliance's exhaust via a heat exchanger to make
| the above more efficient as a standard part of home
| plumbing.
|
| Smart appliances that sync with the home's energy system
|
| - eg: clothes dryer that has the option to turn only when
| there is excess electricity available. Same with EV
| charging, etc...
|
| [Edited for typos]
| starlust2 wrote:
| > Lots of home appliances generate lots of heat (clothes
| driers, ovens, refrigerators, ...) that is currently
| vented to the atmosphere. it'd love to capture that and
| use it to "charge" the hot battery.
|
| I've seen systems that use waste heat from central A/C to
| heat a swimming pool. In addition to the condenser they
| have a heat exchanger connected to the coolant line. Pool
| water is pumped through the heat exchanger and back out
| to the pool.
| merely-unlikely wrote:
| > I was always wondering why there are no systems converting
| the unused electricity in potential energy by moving water to
| a higher ground
|
| There are a bunch of pumped storage facilities around [1].
| But they work best at massive scale, so suitable locations
| are somewhat limited. Plus they are expensive to build and
| often face environmental protests (similar to building dams).
| Still, it's a solution I'm a fan of.
|
| [1] https://en.wikipedia.org/wiki/List_of_pumped-
| storage_hydroel...
| bobthepanda wrote:
| Also, any sort of hydro-based solution is susceptible to
| drought evaporating water below sufficient operation
| levels.
| cupofpython wrote:
| emphasis on massive scale.
|
| Moving 500,000 kg (over 1 million pounds) 7.5 meters (~25
| feet aka the height of a house) will give you about 10 kWh
| of energy. This is equivalent to running a 425W device all
| day, like a small air conditioner. The relationship is
| linear. Double the weight or the distance to double the
| energy. All of the metal at a scrap yard I know of amounts
| to less than half that weight, for reference.
|
| I'm also a fan because pumped storage is a really
| interesting storage method, but it is beyond niche. It is
| very tough to move that kind of weight around efficiently
| for what you get back. Pumping water to great heights is
| not easy either. (see also: moving rail-carts up a
| mountain)
| SECProto wrote:
| > All of the metal at a scrap yard I know of amounts to
| less than half that weight, for reference.
|
| That's not a great reference point when you're trying to
| visualize to pumped storage, as water is 1t/m3 while
| steel is up around 7 or 8. Also, 500t of steel at a
| scrapyard seems very small - 70m3?
|
| A better reference might be a back yard pool, which might
| be in the 30-40t range - so like lifting 15 back yard
| pools the height of your house to power a tiny AC.
| PaulHoule wrote:
| They are building a lot of them in China
|
| https://en.wikipedia.org/wiki/List_of_pumped-
| storage_hydroel...
| cupofpython wrote:
| Makes sense, it is definitely a useful tool. I just think
| it is insufficient to act as storage. It can be good at
| producing variable amounts of Watts on demand but not so
| good at storing enough Watt-hours to keep things running
| for very long. I can see a great appeal for it to help
| with load-balancing for a significant amount of
| choppiness between supply and demand on the hour
| timescale.
|
| For something like solar, where we will want to store
| over half our daily energy production at peak storage
| (ideally 2-3 days worth I think) - I don't think it holds
| up. Additionally, it doesnt seem like a good bet as a
| primary mechanism for either storage or on-demand
| generation if energy consumption continues to increase
| due to the rather large coefficients involved for scaling
| it up.
|
| "The United States generated 4,116 terawatt hours of
| electricity in 2021"[1]
|
| 4,116 TWh/year = 11.2 TWh/day
|
| The storage capacities for the largest items listed on
| the wiki is on the magnitude of GWh. The scale goes
| kilo-, Mega-, Giga-, then Terra. So we are talking about
| a need on the order of a thousand pumped storage
| facilities per country. The US would need over 50 of them
| per state (on average) in order to keep everything
| running without production for 24 hours. Doesnt matter
| how many solar panels we have, if we get 1 dark day then
| we would run out of power. If we tried to rely on solar
| entirely, we'd also still need very roughly half that
| amount of storage just to get through the night.
|
| lithium batteries are obviously much better suited for
| overnight storage, but I have no idea what the numbers
| are on how much lithium is physically available to use as
| such storage.
|
| If we want to get on the order of monthly to yearly
| storage to allow, for example, solar panels in alaska to
| provide enough energy for a resident to get through
| months of darkness - I have no idea what the leading
| storage options are, probably lithium still
|
| [1]https://www.statista.com/statistics/188521/total-us-
| electric...
| kenhwang wrote:
| It's not "beyond niche", it accounts for 95%+ of
| worldwide stored energy and is the de-facto energy
| storage mechanism that all new battery storage
| technologies are compared against. It also has round trip
| efficiency comparable to the li-ion batteries (80-90%),
| which is incredibly hard to beat.
| cupofpython wrote:
| 95% stored energy by what measurement? See my other
| comment. It is not accessible to everyone, nor can it be
| made accessible to everyone, and the current storage
| capacity is a marginal fraction of what we actually use.
| It's a short term load balancing tool that operates
| within a small energy window.
| fy20 wrote:
| That's around the weight of a fully loaded A380.
| jammaloo wrote:
| There is a great youtube channel that tests out different
| energy storage and harvesting setups, a lot of them focused
| around water.
|
| This is one where they use solar to pump water to the roof,
| and then use the potential energy overnight:
| https://www.youtube.com/watch?v=CMR9z9Xr8GM
| dahfizz wrote:
| A top comment on that video puts it into perspective well.
| That whole setup can store the energy of a single AA
| battery.
|
| He would be so much better off just charging a cheap
| battery. All the money wasted on pumps, wood, barrel,
| pipes....
| goda90 wrote:
| I was reading someone's description of their greenhouse. They
| built a cistern under it to catch rainwater for watering plants
| and ran heat pipes into it for warmth in the winter. I've been
| dreaming of doing the same at some point.
| aidenn0 wrote:
| Forget geothermal, I'd love an air-exchange system for the
| summers where I live. It's not uncommon for the low to be in
| the 50s, with the high in the 80s. If I could just store some
| of that overnight cool in water and then run it through the
| central air system, I almost wouldn't need AC.
| tyfon wrote:
| There is a school close to where I live that does something like
| this.
|
| During the summer they heat the bedrock using solar panels
| (thermal and electric via a heapump) to heat the bedrock far down
| using water pipes. In winter they extract this energy for
| heating, electricity and hot water making the school self
| sufficient for energy.
|
| Here is a write-up from the municipality about it, but it's in
| Norwegian
|
| https://www.drammen.kommune.no/om-kommunen/aktuelt/unikt-pro...
|
| Edit: translated version
|
| https://www-drammen-kommune-no.translate.goog/om-kommunen/ak...
| boxed wrote:
| That's just a ground heat pump no? I have the same on my house.
| It's pretty great. I get cooling in summer and heat in the
| winter.
| mnw21cam wrote:
| If you're in an area that gets hot enough in summer for you
| to want cooling, then yes you'll be pumping heat into the
| ground during summer and extracting it in the winter. For
| those of us who don't get hot enough in summer to want
| cooling, we're always extracting heat from the ground, and so
| the ground we're extracting heat from gets cold, which
| reduces the efficiency of the system. Having a solar powered
| mechanism for putting some heat back into the ground in
| summer would help alleviate this problem.
| brtkdotse wrote:
| > the ground we're extracting heat from gets cold
|
| Not if you're using deep drilled holes (100m+). You can run
| a heat pump of the differential indefinitely
| oittaa wrote:
| Apartment buildings in Finland have these 100m to 200m
| drill holes for the heat loops since you can't run those
| horizontally to the neighbor's yard. A bonus benefit is
| that the core of Earth has to basically cool down before
| they run out of heat to extract.
| fy20 wrote:
| Another approach would be to have a longer length of
| piping. The rate at which the soil temperature drops when
| you extract heat, and then 'recharges' naturally, will vary
| greatly if you have 100m vs 1000m of piping. This is why
| ground source heat pumps use pipes laid out in coils, as it
| greatly increases the surface area.
| majou wrote:
| Same idea in Alberta: http://dlsc.ca/borehole.htm
| rjmunro wrote:
| And at the Blavatnik School of Government building in Oxford:
| https://www.bsg.ox.ac.uk/about/our-building
| adev_ wrote:
| In a smaller scale, this is also what the French solar panel
| manufacturer Dual Sun [^1] sell with their geothermal+hybrid
| panels solution for individual houses.
|
| - In winter, heat is generated with a geothermal heat pump and
| an horizontal underground network of pipe.
|
| - In summer, the thermal solar excess energy is used to warm up
| the soil that has been cool down during winter and also to
| avoid permafrost.
|
| [1]: https://dualsun.com/applications/pompe-a-chaleur-solaire/
| ParksNet wrote:
| How effectively does the ground maintain this heat, and how
| much of it dissipates up and out?
|
| As a side effect: using a heat pump to heat the ground during
| summer also cools the building on top! (When its at the other
| side of the heat pump loop)
| bergenty wrote:
| Wait how long does that heat last. I wouldn't imagine more than
| a week since it's not insulated?
| 1970-01-01 wrote:
| The best part about geothermal is that it's one of the cheapest
| ways to make electricity, about as much as burning coal, with
| none of the pollution.
|
| https://en.wikipedia.org/wiki/Cost_of_electricity_by_source
| jillesvangurp wrote:
| Interesting option. It's all about the cost and efficiencies in
| the end.
|
| Converting electricity into heat and then back into electricity
| is a lossy process that is constrained by the second law of
| thermodynamics. Basically generating heat is easy and efficient.
| But converting it back to electricity is typically less than 50%
| efficient. Basically, it's several energy conversions in one
| process: you use electricity to produce heat, heat to produce
| mechanical energy, and then mechanical energy to produce
| electricity. All of those steps are lossy, some more than others.
| And it multiplies. It adds up to less than 50% efficiency, at
| best.
|
| Lithium ion batteries are much better at over 90% efficiency. But
| they are relatively expensive for large amounts of storage. So
| they don't scale. But they have no moving parts and you can scale
| the capacity at which they absorb and release energy pretty much
| linearly. Which is why they are popular for balancing the grid.
|
| Pumped hydro, which is a type of battery that has a relatively
| large amount of deployed capacity in some countries (many gwh of
| power stored) is both efficient and cost effective. But it's
| highly dependent on terrain. Yet parts of Canada run almost
| exclusively on hydro and pumped hydro.
| rnhmjoj wrote:
| > But converting it back to electricity is typically less than
| 50% efficient.
|
| It's generally much much worse than 50%. Say that you used a
| resistor to heat the water in a (perfectly insulated) boiler
| and want to know how much useful work you can extract from it,
| ideally. The answer is given by the exergy efficiency, which
| can be computed by attaching an imaginary heat engine to it,
| integrating the infinitesimal works dW = dQ[?]e_Carnot while
| the temperature drops from the initial T_boiler to T_ambient
| and dividing by the internal energy of the boiler.
|
| The result is e_exergy = 1 - T_ambient/T_lmtd where
| T_lmtd = (T_boiler - T_ambient)/log(T_boiler/T_ambient)
|
| is the logarithmic mean temperature difference. Even heating
| water to 90degC gives an efficiency of only 9%.
| jbay808 wrote:
| > Say that you used a resistor to heat the water
|
| If you're looking to maximize round trip efficiency, this is
| probably not a good starting point. Better to use a heat
| pump, as mentioned elsewhere.
| rnhmjoj wrote:
| Yes, if you're counting the heat output as part of the
| useful energy, but parent was specifically talking about
| converting electricity into heat and back again.
| jbay808 wrote:
| So am I. If you're going from electricity to heat for
| storage and back to electricity, you'll get better
| efficiency by using a heat pump to generate that stored
| heat. In general, sticking to processes that are as close
| to reversible as possible will be the most efficient.
| rnhmjoj wrote:
| Ok, I see your point now.
| Someone wrote:
| If you then use the lithium ion to produce heat, things start
| looking less favorable for it.
|
| Also, I think the "geothermal" part of this means your
| 'battery' gets partly charged for free.
| Schroedingersat wrote:
| Counter point is if you have work (or high grade heat) you
| can use it to move heat rather than just thermalising it.
| jillesvangurp wrote:
| This article is about storing energy generated using
| renewables in reservoirs; not about tapping into geothermal
| energy.
|
| The issue with geothermal is not that the energy isn't there
| but that getting to it involves a lot of expensive
| infrastructure. It's cost effective in some parts of the
| world and not really cost effective (relative to cheaper
| solutions) in other parts of the world.
|
| Using this instead would mean having to drill much less deep
| (so it's cheaper). You are sill throwing away more than half
| of the energy you put in though. Geothermal has similar
| inefficiencies except you get the energy that needs to put in
| for free. Not so with this solution: you have to generate the
| energy yourself.
| Someone wrote:
| > This article is about storing energy generated using
| renewables in reservoirs; not about tapping into geothermal
| energy.
|
| I think it's about both. They plan to create reservoirs
| that heat water _and_ use them to store warm water. Also
| for the latter the outside heat source will provide energy.
|
| FTA: _Enhanced geothermal systems (EGS) get around this
| geographical limitation by creating artificial reservoirs.
| Developers create fractures in hot, dry rock formations by
| drilling into or melting the rock, and then injecting water
| into the fissures. Production wells bring the heated water
| up for producing electricity. "For scales necessary to
| contribute to national or global electricity
| decarbonization, we need to be able to extract geothermal
| heat outside of conventional formations," Ricks says.
|
| [...]
|
| Once these EGS systems are in place, they would be ideal
| for storing energy as well as producing electricity. Excess
| wind or solar energy could be used to inject water into the
| artificial reservoirs_
| drewbeck wrote:
| Yeah that last line is key -- they're not creating heat
| with the excess energy, they're pumping water. The
| article doesn't have much specifics but the implication
| is they're achieving much higher efficiency than if they
| were doing electricity - heat - electricity
| Someone wrote:
| It's not clear from the article, but I think they're
| aiming to do both: create new geothermal sources by
| drilling (running, I guess, some of the risks of
| fracking) _and_ storing excess energy as heat in those
| sources.
| drewbeck wrote:
| yeah they're creating geothermal reservoirs to pump with
| water to then extract steam. any excess energy generated
| from renewables gets used to pump additional water into
| the reservoir.
| pfdietz wrote:
| Pumped thermal storage, where a reversible device is used to
| generate heat (and cold), then generate power from the heat
| (and the cold), can have efficiencies of up to 75%.
|
| https://aip.scitation.org/doi/10.1063/1.4994054
|
| "Insofar as the numbers I have presented in this paper are
| correct, they demonstrate that energy storage is a problem of
| 19th century science. No future laboratory breakthroughs or
| discoveries are required for solving it. All that is needed is
| fine engineering and assiduous attention to detail. Said
| poetically, this is 21st century rocket science."
|
| Even resistive heat can give efficiencies > 50% if the storage
| temperature is sufficiently high. For example, the ENDURING
| system from NREL (now being commercialized by Babcock & Wilcox)
| has a projected round trip efficiency of 53%, using sand heated
| to 1200 C to store the heat. Heat transfer from sand to the
| working gas is via a fluidized bed heat exchanger, a nicely
| compact system with very large heat transfer area.
|
| https://arpa-e.energy.gov/sites/default/files/2021-03/07%20D...
| ksidudwbw wrote:
| Not used for electricity just cooling and heating with heat
| pumps
| socialdemocrat wrote:
| They claim 90% efficiency, so I doubt you can compare this to
| heating a container and them driving a stream engine
| afterwards.
|
| I suspect they are here also utilizing geothermal heat and
| heatpumps which allows you to increase efficiency. If you heat
| water that is already quite hot, then you can get more energy
| back than you put in. Higher temperature differentials give
| better efficiency.
| moffkalast wrote:
| I wonder if it would be possible to scale down pumped hydro to
| something the size of a tall water tower. Probably not worth it
| due to the small height difference and volume, and you'd also
| lose efficiency due to the smaller turbine, but I still do
| wonder what the actual figures are like for something like
| that. Especially in cost per kWh stored compared to lithium.
| martin_a wrote:
| I saw a video like a month ago on YouTube where somebody
| pumped something like 250 liters of water on his roof (7
| meters elevation, if I remember correctly) and let it run
| through a homebuild generator.
|
| The power capacity of that setup was like that of an AA
| battery, if I remember correctly.
|
| You need huge amounts of water and lots of height difference.
| jandrese wrote:
| Yeah, pumped hydro is one of those power sources that
| doesn't scale down at all.
|
| However, home scale conventional hydro is a thing. If you
| live on a hill with a creek that runs down it you can
| install a generator that produces a usable amount of
| consistent power for the cost of a few hundred meters of
| PVC pipe, a barrel, some connectors, and a small electric
| turbine. Search for micro-hydro if you want to know more.
|
| Like all hydro solutions it's heavily dependent on the
| geography and only suitable for well under .1% of the
| population, but where it is feasible it can be a huge step
| towards off-grid living. Add in some batteries, maybe
| supplement with some solar panels, and you've got all of
| the electricity you need year round at a somewhat
| affordable price.
| martin_a wrote:
| > Search for micro-hydro if you want to know more.
|
| I've probably seen everything YT has to offer on that.
| :-D
|
| While I really enjoy those videos and the "let's just do
| it" vibe with old washing machines as generators, I'm
| also somewhat happy that Germany has rather strict
| regulations on how to use water from streams and rivers.
| Some installations are quite disturbing for local
| ecosystems. But being off-grid in remote areas these
| solutions seem like a probable compromise.
| ed312 wrote:
| Based on some extremely back of napkin math (e.g. doing one
| of those activities where you cycle to power a light bulb)
| that seems pretty far off. Was the flow rate extremely low?
| Have a link?
| rootusrootus wrote:
| Sounds like this one:
| https://www.youtube.com/watch?v=CMR9z9Xr8GM
|
| They do say it is about equivalent to a single AA
| alkaline. It is not exactly an optimized efficient setup,
| but still, it gets the point across. Pumped hydro is a
| grid scale option, in places that have the ability to
| store a _lot_ of water.
| martin_a wrote:
| That's the one!
| raphaelj wrote:
| 250L x 7m is 17kN, or about 5W/h, or about 2 AA 2450mAh
| cells from IKEA.
|
| Pumped storage scales well though, as the stored volume
| scales squarely to the required container material (e.g.
| storing 25,000L will only take 10x the material while
| storing 100x the energy).
| dmurray wrote:
| 250 litres x 7 metres is 1750 kilogram-force-metres.
|
| Wolfram Alpha [0] says this is about 5 Watt-hours, and
| gives some other handy comparisons:
|
| > [?] 0.45 x metabolic energy of one gram of fat ( [?]
| 38000 J )
|
| > [?] 0.63 x energy released by burning 1 gram of ethanol
| ( [?] 27000 J )
|
| > [?] metabolic energy of one gram of sugar or protein (
| [?] 17000 J )
|
| > [?] (0.02 to 0.09) x typical kinetic energy of a car at
| highway speeds ( 200000 to 900000 J )
|
| > [?] 0.5 x typical battery energy content of an alkaline
| long-life C battery ( [?] 9.6 W h )
|
| > [?] 0.55 x typical battery energy content of a
| nonrechargeable Lithium-Thionyl Chloride AA battery ( [?]
| 8.6 W h )
|
| > [?] 0.92 x typical battery energy content of a carbon-
| zinc D battery ( [?] 5.2 W h )
|
| Gravitational potential energy is just really, really low
| energy density. Fortunately it's reasonable to have
| pumped-storage reservoirs that contain trillions of
| litres of water.
|
| [0] https://www.wolframalpha.com/input?i=1750+kg+metres+i
| n+watt-...
| RosanaAnaDana wrote:
| Would you be able to help me figure out the gravitational
| potential energy of the red hill tanks?
|
| https://www.epa.gov/red-hill/what-red-hill-bulk-fuel-
| storage...
|
| They were recently decommissioned due to leaks, but I've
| often wondered if they could be repurposed as gravity
| battery storage.
|
| edit: if you want to check my math. I calculated the
| tanks at ~567 million liters, and am saying there is 120
| meters of vertical distance.
|
| They would be equivalent to a 0.1856 GW h (gigawatt
| hours) battery if repurposed in this way. https://www.wol
| framalpha.com/input?i=567810000*120+kg+metres...
| dmurray wrote:
| I think a bit more than that, the article says 250
| million gallons which is more like 960 million litres.
| That squares with the dimensions given: 15m x 15m x pi x
| 75m x 20 tanks = 1 million cubic metres = 1 billion
| litres.
|
| Oahu uses about 225MW on average in residential
| electricity [0], so this could store an hour or so of
| excess capacity. That's not nothing, but you might want
| to 5x or 10x it to really smooth out demand and supply
| peaks for the island.
|
| Note that you also need a set of tanks or a lake at the
| bottom of the hill. The tanks are 75m tall, so how are
| you accounting for that in your 120m of vertical
| distance?
|
| [0] https://www.eia.gov/todayinenergy/detail.php?id=49036
| gives 2,018 kWh per person in Hawaii
| empyrrhicist wrote:
| Water is just too heavy. Pressurized air would be easier.
| killjoywashere wrote:
| Joule for joule, pretty sure I'd rather be standing 10 feet
| from a failed water tower than a failed pressure vessel.
| 1/2 m*v^2. That squared gets you every time.
| moffkalast wrote:
| I think there's a start-up in Italy working on pressurized
| CO2 which apparently has some major benefits over using
| air.
| VaxWithSex wrote:
| Yes, higher liquifying point.
| jillesvangurp wrote:
| It can work, it's just a cost equation. You need a large
| amount of mass to get meaningful amounts of energy stored. So
| pumped hydro is nice because you are basically using natural
| reservoirs and some cheap pumps and pipes.
|
| A water tower needs to be built first and only stores a
| limited amount of potential energy. The problem is not the
| efficiencies but the cost of building a big enough tower. A
| tower with the same capacity of a pumped hydro reservoir
| would be insanely expensive. Or alternatively building many
| thousands of smaller towers that add up to the same capacity
| would also not be cheap.
|
| There are a few alternative gravity systems being tested out
| in the form of e.g. big cranes with weights that drive
| generators, mine shafts with similar systems, etc. Proving
| they work efficiently is not the issue. It's just scaling
| their deployment cost effectively.
| killjoywashere wrote:
| Why would you need a water tower? If you're in flat
| geography at sea level, you could probably access tidal
| energy to drive generators. If you're flat and far from
| water, couldn't you dig a shallow hole and a deeper hole,
| and put the generator and pumps in between? I mean, even in
| Kansas it's not that hard to find an elevation difference
| of 50 feet.
| jillesvangurp wrote:
| It's just an example from the comment I replied to was
| using; I agree it's not a very feasible thing to do. But
| I used it to illustrate the difference in cost between
| that and pumped hydro using natural reservoirs. The point
| being here that you'd need a stupidly large amount of
| water towers to come close to the amount of energy you
| can store in a pumped hydro reservoir
|
| Whether it's a water tower, a big crane, or whatever that
| holds the mass that you then use to drive a generator.
| You have to build it or use nature to have some natural
| height difference. Building infrastructure like that is
| expensive. So nature is preferable and way cheaper.
|
| I come from a relatively flat part of the world; so
| that's not really an option there. Gravity based
| batteries are nice where they can be done cheaply. But
| otherwise probably not ideal.
| Sakos wrote:
| > If you're in flat geography at sea level, you could
| probably access tidal energy to drive generators
|
| There are projects testing this, but ocean water is
| highly corrosive and maintenance is a nightmare.
| elif wrote:
| That's the problem with the US capitalist approach to
| renewable energy. "Can I downsize this to a scale that makes
| sense in our economic reality?" Dang, there dies another
| viable idea. Instead of changing the status quo we have some
| warm libraries and city halls.
| lotharcable wrote:
| It is 100% possible.
|
| The problem is that it's monumentally expensive. You will
| need to have a pretty big water tower to handle enough energy
| to run a microwave for a hour.
|
| P.E. = mg(h)
|
| So say we have 2,000 liters of water that is 50 meters high.
|
| 2000kg * 9.81m/s^2 * 50 * 80% efficiency = 784,800.0 joules.
|
| Say you have a 1100 watt microwave. A watt is 1 joule per
| second. That gives you enough energy to run that microwave
| for about 11 minutes.
|
| A better example would be existing municipal water towers. A
| 500,000 gallon water tower that is 129 feet tall costs about
| 2 million dollars. This is based on a public notice I found
| for a city in the USA.
|
| That is 1892700 liters and 39 meters. I am guessing that the
| average height the water actually falls is 25 meters.
|
| The average American household uses about 30Kwh per day.
| Which is 108,000,000 joules.
|
| 1892700 * 9.81 * 25 * .80 / 108,000,000 = 3.4
|
| So 2 million dollars for 3.5 households-days worth of energy.
|
| I don't know if having 1 days worth of energy is too much or
| too little per household.
|
| And beyond the cost of the tower itself you need the
| generators and lines and holding pond for the water. Or
| underground tank or whatever you want to use.
|
| It's very expensive.
|
| However it is probably the cheapest option right now as far
| as current technology goes.
|
| It would probably be cost effective for a off-grid shack in
| the woods, though.
| moffkalast wrote:
| > Or underground tank
|
| Hmm that is an interesting idea, but it would be even more
| expensive.
|
| If you take that water tower, place it on top of a 80 m
| hill, then dig down for say another 40 m for the second
| tank you now have a total of around 160 m of height
| difference. That would bring it up to 22 households-days or
| if my conversions are correct, 660kWh, which is not
| insignificant.
|
| Then again if google is correct the price for an equivalent
| lithium bank would be only like 100k so it's not even
| close.
| prox wrote:
| Big fan of gravity well storage, it seems simple and elegant.
| https://energyskeptic.com/2019/gravity-energy-storage/
|
| The above link has some numbers (2019 had it bookmarked so
| maybe it has improved)
| Schroedingersat wrote:
| That website is full of deranged ramblings which are
| largely disconnected from reality. Case in point:
|
| > MY NOTE: well whoop-dee-doo. China generates 16.2
| trillion terawatt-hours (TWh) a day. That's 64 billion
| times more than all of the open-cast mines can provide.
| Better start digging more holes!
|
| 16.2 trillion terawatt hours a day is ~4 million times the
| total global insolation or 35 billion times total global
| energy usage. This is more wrong than asserting that a
| single man on a bicycle generator could produce our entire
| primary energy worldwide.
| prox wrote:
| Thank you for letting me know! Did a bit of checking and
| deleting this from my bookmarks!
| Schroedingersat wrote:
| I find it's a useful barometer of what crazy
| disinformation is going to be spread next because it has
| been SEO'd so well.
|
| It also often covers interesting topics, and many of the
| stories are actually about something important or useful.
|
| Additionally many of the things it 'debunks' are actually
| terrible ideas, and some of the arguments it uses are
| valid.
|
| For gravity storage the costs and inefficiencies are a
| bit prohibitive for the use case of an unsubsidized high
| capacity (more than 1 day) option, and it's not really
| competitive with batteries for less (and is highly power
| limited).
| Retric wrote:
| Using batteries for the grid requires roughly the same amount
| of batteries as EV's do. A 100kWh battery pack for a car *
| 1,000 charge cycles / 25 years = 4,000 kWh of battery per year
| * ~290 million cars. That's enough to store almost 1/3 of all
| current electricity used in the US while ignoring busses and
| farm equipment etc.
|
| Of course actual cost depends on how much storage we need and
| future battery prices but adding something like 20-50$/month on
| future electricity bills gets offset by both cheaper
| electricity from solar and wind and less excess generating
| capacity. In that context large scale batteries seem like a
| perfectly reasonable solution.
|
| Which is supported by many current grid scale PV instillations
| including them so they can avoid a AC>DC step when charging the
| batteries and then sell during peak demand at a premium.
| elif wrote:
| As someone that charges lithium batteries for both cars as
| well as for my house, I can promise you there is 0% of me
| that wants to cycle my vehicle battery from 100 to 0 every
| day to arbitrage $1.80 of electricity.
| alfor wrote:
| But if you could cycle your battery from 50%-80% it's
| possible you don't get any meaningful wear on the battery.
|
| You could also just charge in period of low usage of the
| grid (if there were special tariffs for that)
| Retric wrote:
| I am suggesting we build ~twice as many batteries as EV's
| alone would need. With half being used for the grid not to
| directly use EV's for grid storage.
|
| Presumably if it gets anywhere close to similar scale grid
| batteries would end up with dramatically different form
| factors and chemistry as they don't need to worry about
| collisions, charging time, etc.
| manholio wrote:
| This is never going to happen. As a car owner, you are in a
| market competing with large providers of grid scale storage,
| that have large purchasing power, control over the battery
| chemistry and finer specifications of their hardware which is
| made to order for their needs etc. Meanwhile, you have a
| mobility-optimized low weight battery that has a single,
| monopoly supplier that will very likely treat the spare parts
| market as a profit center 5 years down the road.
|
| You will never be able to compete because you cannot
| differentiate, the product is fungible so mass always wins.
| It's essentially the bitcoin mining rig drama, the going was
| good until large scale mining operations were set up, with
| optimized ASICs etc. After that, good luck destroying your
| graphics card and car battery for pennies on the dollar.
| raphaelj wrote:
| Couldn't scheduling the EV charge when the demand is low
| while production is high help a lot balancing the grid, at
| basically no cost for the EV owner?
|
| Let's say I have a EV with a smart charger that will keep
| the vehicle at least 60% charged, but charge up to 100%
| when the energy price is low (e.g. during the night).
| manholio wrote:
| > at basically no cost for the EV owner?
|
| Only if you have a battery with unlimited charge cycles.
| This doesn't seem possible with current technology - and
| even if it were, manufacturers would still optimize for
| higher density and reasonable longevity after 100,000
| miles. Most people would average a charging cycle a week,
| so they can't see the difference between a 2000 cycles
| battery and a 50,000 cycles one in the life of the car,
| but they can definitely feel the effects of range
| anxiety.
|
| When you do daily or multiple times a day cycles, as is
| typical for grid applications, that's a completely
| different beast, for example a shallow charge cycle at
| 70% which increases the life 5x is much more profitable
| because it reduces overall battery replacement costs.
|
| And when you factor in the much higher costs per Wh for
| car batteries, which are custom spare parts not mass
| produced commodity cells, you will find that the cost you
| incur in vehicle depreciation far exceeds the value you
| could earn from intra-day energy market speculation.
| Retric wrote:
| I am not suggesting we use EV batteries for grid storage,
| just ~double the number of batteries created with half
| going to EV's and half going to the grid.
|
| Of course different constraints means different chemistry
| and form factors etc, but that's only going to make grid
| batteries cheaper.
| manmal wrote:
| Depending on charging strategy, LFP batteries can do 4000 -
| 7000 cycles. 1000 is way too conservative, for any kind of EV
| battery.
| chriswarbo wrote:
| > Using batteries for the grid requires roughly the same
| amount of batteries as EV's do
|
| EVs have much harder constraints. The most obvious is that
| they need to move around (requiring high energy density, for
| both mass and volume); they also need to cope with sporadic
| charging times, and be reasonably fast to charge. It's very
| hard to compete with the leading Lithium-ion batteries in
| this space.
|
| Grid storage isn't as constrained. Larger, heavier batteries
| are fine since they're just going to sit in one place. It's
| also easier to accomodate awkward/slow charging requirements,
| since they're always plugged in to the grid, and can be
| coordinated with other electricity sources/sinks if needed.
|
| This allows different chemistries to compete, based on e.g.
| price, longevity, safety, etc.
| Retric wrote:
| Yep, it's very possible that wildly different chemistry or
| even some other method wins. However, using the same
| battery chemistry in a cheaper form factor is the worst
| case. Aka if 2.3 Trillion on EV batteries works then the
| winner must cost less than 2.3 trillion.
| macintux wrote:
| Or have fewer externalities, since that's never properly
| priced into anything.
| Animats wrote:
| "Ricks and his colleagues' simulations found that the systems
| could store energy with up to 90 percent efficiency over one
| cycle."
|
| Heat, maybe, but electrical to heat and back to electrical, no
| way. You're limited by basic thermodynamics.
|
| They have a web site.[1] Not that it has any useful information.
|
| [1] https://www.fervoenergy.com/
| aaaaaaaaaaab wrote:
| Geothermal smartphones when?
| rexreed wrote:
| That puts real meaning into the term "landline"
| photochemsyn wrote:
| Hot dry rock schemes have been around for a while (apparently
| dating back to a project in 1970 in Los Alamos NM), but for it to
| work it seems you need some specific rock types. For example, one
| project only recovered 3% of the injected water due to losses
| into fractures. Here's a historical overview:
|
| https://www.sciencedirect.com/topics/engineering/hot-dry-roc...
| nullish_signal wrote:
| One wonders what the limits of "Thermal Heat" are from small
| "wells"(???) up to the heat content of the Earth's ore (Heat
| relative to sea level)
|
| How much heat is generated by Earth's gravity onto itself? How
| "renewable" is Geothermal energy, truly?
| snarfy wrote:
| About 47 terawatts
|
| https://en.wikipedia.org/wiki/Earth%27s_energy_budget#Earth'...
| flavius29663 wrote:
| That seems terribly low, but apparently it's correct (humans
| need right now about 18TW). This means a lot of Earth's heat
| is actually coming from the sun itself.
|
| One small nuance: the OP asked about the heat generated by
| Earth's mass. The 47TW is split between the original heat
| from the formation of the Earth and the nuclear decay of
| radioactive elements.
| [deleted]
| Archelaos wrote:
| From the Wikipedia article on "Geothermal energy":
|
| "Geothermal power is considered to be renewable because any
| projected heat extraction is small compared to the Earth's heat
| content. The Earth has an internal heat content of 10^31 joules
| (3*10^15 TWh), approximately 100 billion times the 2010
| worldwide annual energy consumption.[...] About 20% of this is
| residual heat from planetary accretion; the remainder is
| attributed to past and current radioactive decay of naturally
| occurring isotopes." --
| https://en.wikipedia.org/wiki/Geothermal_energy#Renewability...
| VilleOr wrote:
| Majority of geothermal enery comes from the decay of
| radioactive isotopes. It's not renewable, but there will be
| enough heat for millions of years.
| CorrectHorseBat wrote:
| Surprisingly it's about 50/50 radioactive decay and heat left
| over from the forming of the solar system: https://en.m.wikip
| edia.org/wiki/Earth%27s_energy_budget#Eart...
| HPsquared wrote:
| It's not renewable, but exploiting it doesn't reduce the
| overall output. It's "not depletable", you could say.
| Schroedingersat wrote:
| At some point you're increasing the conductivity of the
| crust and mantle.
|
| You have a bunch of bigger problems that come to roost much
| sooner than this if you're using that much geothermal
| though,
| CorrectHorseBat wrote:
| How is that different from renewables?
| marcosdumay wrote:
| It's not. Renewable on energy discussions basically means
| "not depletable".
| Schroedingersat wrote:
| The total budget for any given power source is surprisingly
| close to 100TW.
|
| Geothermal, you'd cool the crust and have to drill far deeper
| than is possible to exceed 50TW for long.
|
| Wind, if you exceed somewhere in the 1-10W/m^2 you slow down
| the wind and create turbulence.
|
| Solar, if you use more than ~1% of the land you're radically
| altering the albedo and habitat (so maybe up to 200TW).
|
| Fossil fuels create GHG and run out quickly.
|
| Nuclear creates enough waste heat in the 100-200TW range to
| cause as much radiative forcing as GHG does now.
|
| We each get our 10-100kW and that's about it for living on a
| planet that isn't one giant factory/heatsink.
| mschuster91 wrote:
| > Solar, if you use more than ~1% of the land you're
| radically altering the albedo and habitat
|
| Both of these may actually turn out to be beneficial. Putting
| up solar panels above agricultural land ("Agri-PV") is not
| just avoiding clobbering up arable land with PV panels, but
| also has benefits for the plants [1]: they need less water
| because less sun directly hits the plants and heats up the
| soil which means both more resilience in drought periods and
| more capacity to regenerate groundwater planes, and the soil
| erosion from wind is reduced as well.
|
| I wonder if putting up panels in the desert could help out
| de-desertification efforts as well for the same reasons.
|
| As for albedo - given that we're already having issues with
| global warming, it is not that far-fetched to say that solar
| radiation being reflected off to space is a good thing
| overall.
|
| [1] https://www.ise.fraunhofer.de/content/dam/ise/de/document
| s/i...
| Schroedingersat wrote:
| Agri-PV is one way of using the thermal budget (and a great
| one from a habitat-harm perspective as it causes a net
| reduction in human-occupied land).
|
| The albedo problem is the opposite of what your are
| thinking as it is another source of radiative forcing from
| putting a mostly black thing in the sun.
|
| A Shockley-Queisser limited solar panel mostly only
| reflects IR. So where your plants/dirt might have an albedo
| of 0.3, the solar panel absorbs 80-95% of the light (albedo
| 0.05 to 0.2). 20-30% becomes electricity (and later
| thermalises when used).
|
| This gives you a net forcing on the order of 100-250W or so
| _somewhere_ on earth for every m^2 of pv. If you cover too
| much land the radiative forcing is on the same order as
| GHG, hence the ~1% limit. 200-300W of work for 100-250W of
| new heat is a pretty fantastic deal compared to other
| options though.
|
| Putting it above existing asphalt or a similar surface is
| 'free' because albedo is already 0.1 there. Similarly wind
| is free from a radiative forcing perspective.
|
| Putting the panel in existing (light coloured) desert is
| much worse because deserts have an albedo around 0.4-0.6 so
| you are making 400-550W of new heat for your 200-300W of
| work.
|
| This also leads to the interesting thought of placing
| bifacial tracking modules sparsely on low albedo dead
| surfaces and painting the surface white for a net reduction
| in thermal forcing (is there a 1000km patch of volcanic
| rock somewhere? Gobi desert?)
|
| In the same framework, every joule of nuclear energy is a
| new watt of heating, and if it is from a steam engine, it's
| more like 3W (or even 5W once you include post-reactor heat
| as well as xW of heat for every 1W of pre-reactor work
| inputs of mining, milling, and enriching low quality ore).
|
| Of course these all only become relevant if we slash carbon
| intensity to under 2% of what it is today and continue
| trying to grow our energy usage exponentially.
| kansface wrote:
| Doesn't the nuclear heating happen regardless of us
| harnessing the energy or not?
| Schroedingersat wrote:
| Unenriched uranium will fission eventually, but you're
| talking trillions of years.
|
| There are some ore bodies that are concentrated enough to
| fission faster, but they are rare (and not the uranium
| that is typically mined for fuel).
| spywaregorilla wrote:
| It's interesting to wonder how profoundly different the world
| would be if everyone had access to geothermal energy at the scale
| of somewhere like Iceland.
| bagels wrote:
| I know they heat their homes with the geothermally warmed
| water, but their electricity rates don't seem to be
| significantly different than most places.
|
| "Iceland, March 2022: The price of electricity is 0.139 U.S.
| Dollar per kWh for households."
| spywaregorilla wrote:
| Iceland has the cheapest electricity in the world. They run
| heat under their roads so they don't need to be plowed.
| Aluminum is shipped to Iceland to be smelted just because the
| energy is so much cheaper.
|
| Iceland's electricity usage per capita is 4x that of the
| United States, and more than 2x the next highest country
| (Norway). They're the largest producer per capita as well.
| The population is not large, mind you, but it's noteworthy.
|
| https://en.wikipedia.org/wiki/List_of_countries_by_electrici.
| ..
|
| The rate for businesses is 0.066per kWh vs 0.128 in the US.
|
| All of which is obfuscated by taxes and subsidies of course.
| https://www.globalpetrolprices.com/Iceland/electricity_price.
| ..
|
| Technically it may be cheaper in some small petrol states but
| that feels misleading.
|
| Mind you I'm just regurgitating a quick google's worth +
| tourism fun facts.
| xienze wrote:
| > Iceland has the cheapest electricity in the world.
|
| Come again? If the parent post about about $0.139/kWh for
| households is correct, I can assure you there are many
| places in the US cheaper than that.
| spywaregorilla wrote:
| If you're asking for some contextual explanation why that
| $0.139 is not a sufficient figure to explain the issue,
| consider reading the rest of my post past the first
| sentence.
| wcoenen wrote:
| It is not clear to me how they use the solar and wind power.
|
| Are they heating the steam from a geothermal source, higher than
| the source's temperature, and sending it back down the geothermal
| well when power is cheap? And then later run the steam through a
| turbine when power is expensive?
|
| Or are they using cheap power to pump water into the well at high
| pressure, to force it it deeper into the fractured rock? And then
| later use the extra steam to produce power?
|
| Or something else?
| orthecreedence wrote:
| Every time I think of geothermal, I can't help but wonder what
| the at-scale externalities are. Sure, if a few people do it in
| their backyard, who cares...but hundreds of millions of people
| pumping heat into the ground to store for later? What terrible
| ecological outcomes will this have?
|
| I guess we'll see.
| ncmncm wrote:
| This is an example of "how can we keep X relevant in a world
| where it is not?" Geothermal is falling away because maintaining
| a steam turbine is expensive.
|
| There are plenty of efficient storage options that don't depend
| on a steam turbine. Those are favored except where the storage
| medium is also a transportable, valuable product, as for ammonia.
| (Ammonia is burned in combined-cycle turbines already built to
| burn NG.)
| helloooooooo wrote:
| It depends what you want to use the geothermal heat for. In
| Norway, in the winter, a lot of the energy use is going to be
| heating. Geothermal heating systems are quite common in
| northern and don't require lossy conversion
| ncmncm wrote:
| And pure thermal uses are not good storage for high-grade
| energy forms, e.g. electric, because of conversion losses. In
| Norway, pumped hydro is a good place to park high-grade
| energy.
|
| That said, for rarely drawn-upon storage, conversion
| efficiency doesn't matter very much. It is why back when
| hydrogen electrolysis still lost 40% off the top, it was
| considered fine for long-term storage. Now that it has
| exceeded 90%, it is useful in more places.
| mountaintimefrm wrote:
| Even low grade geothermal is pretty awesome. Example: "Nebraska
| retiree uses earths's heat to grow oranges in snow" -
| https://youtu.be/ZD_3_gsgsnk
| smileysteve wrote:
| In reading, it's not clear which types of batteries this is
| referring - lithium like the Tesla power wall is definitely not
| the ideal chemistry to use full time -- but we have different
| electrolytic (flow) or catalyst (fuel cell) driven batteries that
| have similar advantages of the geothermal method without the
| drilling or maintenance of underground systems.
|
| Flow batteries are minimally dangerous, have huge storage
| capacities, have a minimum maintenance per 1000 charge schedule,
| and while they are slow to "turn on" are faster than geothermal.
|
| Disclaimer; I have a small startengine investment in a Vanadium
| Flow battery company
| newyankee wrote:
| More the competition the better for the world.
|
| I still feel a well designed Lithium Iron Phosphate or Sodium
| based battery with > 5000 cycles can prove very cost effective if
| used properly. The high no of cycles reduces the levelized cost
| of storage significantly. Difficulty is scaling this to beyond
| 1-2 days at most.
| swayvil wrote:
| Competition is just a euphemism for fighting. You're saying
| that more fighting is better.
|
| Isn't that crazy? You'd think that fighting would be wasteful
| and upsetting. That peace would be better.
|
| It's a crazy world.
| Bakary wrote:
| Forget the word competition. Just think of it as smart people
| having an incentive to produce something with beneficial
| effects or externalities for once.
| nicoburns wrote:
| I'm not convinced competition is a euphemism for fighting.
| Competition can be friendly.
| swayvil wrote:
| You got any examples of "friendly, nonfighting type
| competition" in the business world?
| macinjosh wrote:
| https://www.cnet.com/tech/tech-industry/microsoft-to-
| invest-...
| rglullis wrote:
| All of the oligopolies? Do you really believe that, e.g,
| tech companies are "fighting" each other? What about Big
| Pharma? The Food industry?
|
| In any case, you are arguing semantics. Competition can
| be friendly.
| swayvil wrote:
| The tech, food and pharma industries fight each other
| tooth and nail.
|
| I don't think this "friendly competition" happens in the
| business world. It's just an ordinary fight.
| rglullis wrote:
| I guess we have different ideas for "fighting tooth and
| nail".
|
| - Steve Jobs and Eric Schmidt would regularly discuss
| matters together.
|
| - They have pretty solid "do not poach" agreements.
|
| - None of them actively blocks their products from
| running on each other platforms
|
| - None of them launch products with the sole intent of
| destroying each others cash cow. E.g, Google could
| release flagship products at budget prices _forever_ ,
| just to take from Apple's market share. They certainly
| wouldn't lose money over it. Why don't they do it?
|
| Competition? Ok, but it never comes to the point where
| they actually want to inflict damage on one another. This
| is as friendly as it gets.
| Schroedingersat wrote:
| The interesting thing is when they've been around for 30 years
| (providing they don't decay too much with time).
|
| A sodium battery with 100 useful cycles and 10 years left in it
| is great for cycling once a month.
|
| But even without that, if we see costs of $50/kWh then you only
| need to cycle 300 times to make it more worthwhile than some
| generation technologies..
| robocat wrote:
| Don't some battery chemistries have much higher self-
| discharge rates as they get older? If so, it might be
| uneconomic/wasteful to try to use old batteries.
| adrr wrote:
| For places with high car ownership, you can use electric cars
| as the battery storage. Just need lithium iron phosphate
| batteries to be standard in EVs. Telsa is using them in some of
| their models in China.
| wazoox wrote:
| An excellent discussion on the matter on the excellent Volts
| podcast: https://www.volts.wtf/p/the-extraordinary-potential-
| value#de...
| Breefield wrote:
| It's laughable this was published citing: "the storage capacity
| effectively comes free of charge" when the whole mess we're in is
| the tragedy of the commons.
|
| FWIW, the link to the Google article is much more interesting:
| https://cloud.google.com/blog/products/infrastructure/google...
| iancmceachern wrote:
| It's because of design efficiency. The most distilled and finest
| design utilizes each part for many things. Like a unibody car, or
| a fuel tank in the wing in an aircraft.
|
| In this case the material doing the thermal storage is also part
| of the building. It's not like there is a building and a separate
| 100 tons of thermal storage stuff, just make the house and
| foundation out of that 100 tons of stuff and then you only have
| to buy 100 tons of stuff, not 200. It's the same economy of scale
| with the labor and digging. You can dig 1 hole and put all this
| geothermal stuff in it along with the foundation, or you can dig
| 2 holes and have twice the everything. If you just combine all
| the items into one big effort, look for design efficiencies where
| you can combine parts and systems, and these systems/buildings
| can basically run themselves with just what is provided by the
| environment. They don't change the environment inside the
| building, they just regulate it between the 2 extremes, taking
| the edge off the high and lows.
| bombcar wrote:
| So can we combine this with the subway tunnels that are getting
| hotter and hotter each year?
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