[HN Gopher] US Government funds pilot project for heated sand en...
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US Government funds pilot project for heated sand energy storage
Author : Capstanlqc
Score : 178 points
Date : 2024-04-04 12:59 UTC (10 hours ago)
(HTM) web link (www.pv-magazine.com)
(TXT) w3m dump (www.pv-magazine.com)
| bell-cot wrote:
| > The sand used in the thermal energy storage (TES) system could
| be heated to the range of 1,100 C using low-cost renewable power.
| [...] when electricity is needed, the system will feed hot sand
| by gravity into a heat exchanger, which heats a working fluid,
| which drives a combined-cycle generator.
|
| So this is _definitely_ not a "bury your heating coils in a sand
| dune, then connect..." technology.
|
| Quartz melts (per Wikipedia) at 1,713 C. Hotter would obviously
| be more efficient (basic thermodynamics) - but from the linked
| govt. report, it sounds like getting usefully hotter would lead
| to excessive technical problems.
|
| Beyond sourcing the sand (a real issue in many places), this tech
| sounds incredibly benign, environmentally. Zero-ish rare elements
| / nasty chemicals / emissions. And the worst-case "melt-down"
| leaves just a pile of burning-hot sand.
|
| Edit: IANAME (not a Mech. Engineer), but that govt. technical
| report looks like great stuff if you're seriously into energy
| storage tech, or just an amateur gearhead. Direct link:
| https://www.nrel.gov/docs/fy23osti/84728.pdf
| smallmancontrov wrote:
| Huh, it intuitively seems like piping working fluid to the sand
| ought to be easier than moving the sand to the working fluid.
| Is the moving-sand approach fundamentally desirable thing (I
| can't imagine why) or is it just a simplification for the proof
| of concept?
| regularfry wrote:
| I suspect it's because the thermal conductivity of sand isn't
| that great. If you've got your working fluid running through
| pipes embedded in hot sand, the system is likely bottlenecked
| on getting the heat energy from the main body of the mass
| through the cooler sand closest to the pipes.
|
| Do it the other way and the enormous surface area is working
| for you, so you can presumably get the energy out arbitrarily
| fast (or, at least, that's no longer the bottleneck).
| regularfry wrote:
| The thought occurs that if that is indeed the problem, you
| could attack it by mixing a metal in with the sand. You'd
| still get the thermal mass, but conductivity would no
| longer be a problem as long as it had been in a liquid
| phase at least once.
| bell-cot wrote:
| Storing & moving fine-grained bulk dry stuff is _really_ old,
| cheap, & reliable technology - think of grain silos.
| dexwiz wrote:
| Yes, and under certain conditions sand is a fluid. Remember
| fluid !== liquid. Gases, liquids, and loose material can
| all be fuilds.
| pfdietz wrote:
| Piping the working fluid to the sand means your pipes have to
| increase in size and cost as you add more sand. Dropping the
| sand into a heat exchanger means the heat exchanger doesn't
| increase in cost with the volume of sand.
| sandworm101 wrote:
| >> Is the moving-sand approach fundamentally desirable thing
| (I can't imagine why) or is it just a simplification for the
| proof of concept?
|
| I suspect this is about operating temperatures. If you run
| pipes through the thermal mass then you will be slowly
| heating/cooling the entire mass. That means the temp will be
| constantly changing and would basically never be at optimum.
| But by withdrawing small amounts of sand to be cooled/heated
| separately, the bulk can remain at an optimum. Only the
| removed sand is cooled. So your tank of "hot" sand remains at
| the same temperature until the last bit of hot sand is gone,
| rather than it slowly cooling as you withdraw heat from the
| bulk. That no doubt makes thermal transfer more efficient and
| predictable.
| AlexAndScripts wrote:
| This seems like a really cool technology that also doesn't need
| much engineering to make it viable. Why isn't it already
| widespread?
| spxneo wrote:
| there is a DIY community around it and because it is so
| simple to make I just dont see any need to rely on commercial
| solutions. Literally store sand somewhere and heat it, use it
| for days or months depending on the setup.
| HPsquared wrote:
| Thermal storage works nicely with solar thermal plants. Not so
| good for direct electricity storage though.
| bell-cot wrote:
| Pretty inefficient, yes. Thermodynamics is a harsh mistress.
|
| But if the other choice is "throttle down the wind farm,
| because the grid doesn't need that much power" - then a
| _really_ cheap /simple/safe (but inefficient) storage tech
| could prove pretty useful.
| seanmcdirmid wrote:
| How does this compared to pumped storage?
| pfdietz wrote:
| Modern pumped hydro might have a RTE of 80%.
| non-chalad wrote:
| You can pump sand by bubbling compressed air through it.
|
| 1. https://www.youtube.com/watch?v=My4RA5I0FKs
| clort wrote:
| seems to me that this would result in heat-loss as the
| air is heated quickly then ejected from the mass. perhaps
| the bubbled gas doesn't hold a significant amount of heat
| though? (but if it did, it could be used to extract the
| heat without pumping the sand...)
| pfdietz wrote:
| One can get higher round trip efficiency (practically,
| perhaps 65%) using pumped thermal storage. Here, one uses
| some thermal cycle in reverse to separate "cold" and "hot",
| then reverse that to discharge. This also reduces the maximum
| temperature needed to maybe 500 C, below the creep limit for
| cheap steel. The cold end would be maybe -100 C, stored in
| something like liquid hexane.
| bell-cot wrote:
| True. But the govt. report on this idea seems confident of
| 50% RTE, or 55% if they used a more-complex turbine system.
|
| For limited & short-term use, the plant with vastly-more-
| expensive storage masses _might_ make sense.
|
| But as soon as you were faced with NIMBYs or
| environmentalists (hexane's MSDS is far closer to hydrogen
| fluoride's MSDS than it is to sand's), or if you are
| working in a less-prosperous part of the world...sand is
| _great_ stuff.
| ndonnellan wrote:
| I was going to chime in to second this. In a former life I
| worked on power towers and we had designs for air receivers
| that would potentially work really well with this type of
| system:
|
| - High temperatures - Intermittent solar input not a problem -
| tall central structure (?? maybe a plus given the paper's tall
| storage vessels)
|
| But high temperature air receivers have their own problems,
| mostly around receiver material properties (thermal cycling /
| stress) and heat loss. It's really hard to focus a lot of light
| from the sun into a tiny aperture, because the sun isn't really
| a point source, and no mirror is perfectly shaped.
| ejb999 wrote:
| I am really intrigued by using sand for energy storage - what I
| don't get (not my field) is given a typical 2000sf house, located
| in the colder part of the country as an example, how much heat
| could be stored for how long? i.e. is it even feasible to use
| solar panels to power resistance heaters all spring/summer/fall,
| to save up enough heat to keep a house warm for the entire
| winter? if so, how many panels would you need and how big a sand
| battery would it take.
|
| I am not planning on doing this, but explaining it on a scale
| that I can relate to would be helpful, because I know, for
| example, that said house can store a winter's worth of heat in a
| 1000 gallon oil tank, or small woodshed big enough for 6 cords of
| wood.
| ceejayoz wrote:
| https://en.wikipedia.org/wiki/Seasonal_thermal_energy_storag...
|
| > In Alberta, Canada, the homes of the Drake Landing Solar
| Community (in operation since 2007), get 97% of their year-
| round heat from a district heat system that is supplied by
| solar heat from solar-thermal panels on garage roofs. This feat
| - a world record - is enabled by interseasonal heat storage in
| a large mass of native rock that is under a central park. The
| thermal exchange occurs via a cluster of 144 boreholes, drilled
| 37 metres (121 ft) into the earth. Each borehole is 155 mm (6.1
| in) in diameter and contains a simple heat exchanger made of
| small diameter plastic pipe, through which water is circulated.
| No heat pumps are involved.
|
| That development is 52 homes. They are presumably engineered to
| be highly energy efficient and it's not a perfect comparison to
| sand, but it's less than I'd have imagined.
| giarc wrote:
| https://www.cbc.ca/player/play/1.7155409
|
| I live in Calgary and have seen a few articles about Drake
| Landing recently.
| ulnarkressty wrote:
| Storing heat in bedrock sounds like a good idea, but there
| are risks, e.g. https://www.thelocal.de/20170818/this-
| historic-german-town-i...
| NewJazz wrote:
| 155 mm huh? Did they use NATO standard mortars to make these
| boreholes :p?
| dubcanada wrote:
| There is no standard borehole size, 155mm drill head is
| quite easily acquired in Canada
| jrockway wrote:
| I don't think that the sand units you can install in your home
| have the ability to store energy across seasons. They are more
| like hot water heaters; heat when you have solar, but you can
| use some hot water at night when electricity is more expensive.
|
| So this would be like, in a mild climate, the sun is going to
| keep your house warm during the day and you are generating some
| solar. You use the solar to heat up the sand, and then
| overnight, you recover some of that energy to use for heat. (I
| think you can get electricity back out of the heated sand as
| well, but it's like 70% efficient compared to >90% for a
| lithium battery. So I think the big application is in heating,
| less for charging your car after you get home from work.)
| cdtwigg wrote:
| The temperatures we're talking about (1000C) would be
| incredibly dangerous in residential applications, plus a small
| installation would lose too much energy to the environment due
| to the ratio of surface area to volume. More practical IMO is
| to use a daily cycle like what Harvest Thermal is doing: store
| energy in your water heater tank during the daytime and release
| it at night.
| dheera wrote:
| > winter's worth of heat in a 1000 gallon oil tank
|
| That's a massive fire risk because it is combustible fuel. A
| pile of hot sand in an auxilary, non-flammable structure isn't
| going to catch fire.
| 0cf8612b2e1e wrote:
| Huge amount of the rural population already have an oil or
| propane tank sitting within a hundred yards of their house.
| Being even slightly remote means you require backup heating
| options for when things fail.
| nick238 wrote:
| A 1000 gallon tank stores about 146 gigajoules of energy
| (diesel motor fuel = 138,700 BTU/gallon, "138700 BTU * 1000
| in gigajoules").
|
| 1000 gallons of sand (about 6000 kg) heated 1000 degC above
| ambient stores about 1000 K * 6000 kg * 1.1 kJ/kg-K (from the
| paper, on page 9) = 6.6 gigajoules.
|
| So to match a fuel tank for energy storage, it needs to be at
| least 22x the volume, have extremely good insulation (even
| more volume), a heat-exchanger, and sand-handling augers.
| Additionally, the sand needed to be heated in the first
| place, which means a good electrical connection, but if you
| have that power in the first place, just use that during the
| winter? The nice part about fuel is that a man and a truck
| can move a few thousand gallons of hydrocarbons several
| hundred miles out to the middle of nowhere and transfer that
| energy at megawatt speed with a hose.
| 0cf8612b2e1e wrote:
| I think this is a surface area/volume problem. A smaller
| installation is going to have a larger relative surface area
| given the amount of stored heat, so your losses/insulation
| requirements are going to be much worse.
| michael1999 wrote:
| A single house is too small to make that work. I can't see how
| you could insulate such a small volume for more than a few
| hours. It can start to work at district scale, but the Finns
| are just targeting a few days.
|
| https://www.euronews.com/green/2024/03/10/sand-batteries-cou...
|
| https://en.wikipedia.org/wiki/Drake_Landing_Solar_Community
| zardo wrote:
| https://www.renewableenergymagazine.com/storage/first-commer...
|
| This is 8MWh (of heat), the 1000 gallon oil tank is about
| 40MWh.
|
| Something like a two story basement filled with sand at the
| maximum temperature of a home oven is probably in the ballpark.
| usrusr wrote:
| A very low key variation of heat storage is using a ground-
| source heat pump in winter and then in the summer using the
| same heat pump for cooling the house and replenishing the
| ground source while doing so.
|
| Small ground sources, or ground sources with neighbors too
| close who do the same, will actually accumulate noticeable
| ground cooldown from season to season if they are not
| replenished. Free air conditioning comfort from the
| replenishing effort, or free replenishing from the air
| conditioning, you can spin it however you like. It's very low
| gradient and certainly won't get you through winter without a
| another power source, but it absolutely is seasonal heat
| storage.
| xnx wrote:
| Does this differ in design from the Finish sand battery from 2
| years ago: https://news.ycombinator.com/item?id=32006791
| pfdietz wrote:
| Yes, this involves higher temperature (the sand is stable up to
| ~1200 C) and transfer of heat from the sand to a working gas by
| means of Babcock & Wilcox's fluidized bed heat exchanger
| technology. This is a neat idea that intimately mixes the gas
| and sand for very rapid and compact heat transfer.
|
| Using resistive heaters, round trip efficiency (back to
| electricity) is estimated to be around 52%.
| michael1999 wrote:
| The Finnish system is just heat->heat. They generate heat when
| the wind is blowing, and inject heat back into the district
| system when it isn't. Super simple - resistive heating, and
| passive heat transfer.
|
| This system produces electricity. Exciting, but much fancier.
| dubcanada wrote:
| A stirling engine can generate heat from electricity, such as
| those used in MicroCHP, you can burn wood, produce heat, and
| generate electricity from that heat. You could do the same
| with a pile of sand.
|
| You just need to pipe liquid through the sand, and a supply
| of cooler water.
| jarito wrote:
| Undecided did a couple of videos on this technology. It seems
| quite useful for heat storage - as other commenters have noted,
| it isn't that efficient for pure electric <-> electric storage.
|
| * How a Sand Battery Could Change the Energy Game -
| https://www.youtube.com/watch?v=G6ZrM-IZlTE
|
| * Sand Batteries for Home Usage -
| https://www.youtube.com/watch?v=KVqHYNE2QwE
| dagurp wrote:
| I like this one too
| https://youtu.be/KVqHYNE2QwE?si=GM80NBsE_Ms8oT-n
| pfdietz wrote:
| I have wondered if this technology could be used in open loop
| mode where the sand is replaced with some material that you want
| to thermally process. For example, olivine particles that become
| more reactive with CO2 (for mineral carbonation for CO2
| sequestration) after being heat treated. Run the particles though
| once and use them afterwards.
| nick238 wrote:
| Feed in calcium carbonate, heat it up and sequester the CO2,
| and use the hot calcium oxide once then ship it off to the
| cement plant.
|
| Or, how about taking an existing cement plant and have it use
| the air heat-exchanger/turbine/generator setup described in
| this project to recover the energy in the red-hot clinker? I
| assume they'd have some sort of heat exchanger system already
| to preheat feedstock using the outflow, however?
| retrac wrote:
| Heat storage has an aspect that was counterintuitive to me, but
| follows from basic geometry. It benefits greatly from large
| scale, since the ratio of the volume to surface area [1]
| decreases the larger you make a container. Accordingly, if a heat
| tank is large enough, the surface area becomes negligible
| relative to its volume, and it, in effect, becomes well-insulated
| by its own mass. For really big tanks, like might be used for an
| entire town to heat itself over a winter, practical self-
| discharge rates can be just a few % per month, which is better
| than most rechargeable battery technologies.
|
| [1]
| https://commons.wikimedia.org/wiki/File:Comparison_of_surfac...
| chii wrote:
| > better than most rechargeable battery technologies
|
| you can't compare heat storage to electricity, because you
| can't directly use heat for anything else other than for
| heating, where as electricity can be used to perform motion.
|
| If you used heat storage as a battery, there's an additional
| loss when converting to electricity.
|
| However, if the heat is cheap/free during summer, storing it
| for winter is a no brainer.
| datameta wrote:
| The sand is gravity-fed into a heat exchanger which transfers
| the heat to a fluid that drives a combined cycle turbine, in
| this case. I'm curious what the conversion loss is here.
|
| To add to that, what is the energy expenditure of building
| the battery compared to sand containment plus heat exchanger
| and turbine - i.e. mining, refining, transport, manufacture,
| delivery?
| robviren wrote:
| Gas turbine efficiency targets for combined cycle are
| targeting 65%, so loss is at least 35%. To me I the loss
| sucks, but if it can be cheap to build and maintain it
| matters less. If solar is the energy source and that gets
| driven cheap enough then that loss could be acceptable.
| NavinF wrote:
| No way you'll get 65%. This sand won't be stored at the
| same temperature as a natgas generator's combustion
| chamber. Efficiency depends on delta T.
|
| I'd guess 20%
| regularfry wrote:
| They're estimating over 50%, apparently. The sand is
| stored at over 1000 degrees. Not combustion temperatures,
| true, but also nothing to sniff at.
| adrian_b wrote:
| Nope.
|
| The report says that the sand will be heated up to 1200
| Celsius degrees.
|
| This is much higher than the maximum temperature for
| steam turbines and equal to the temperature of the gas in
| the best gas turbines.
|
| Therefore they will use a combined cycle, first a gas
| turbine will use hot air passed through the sand and the
| exhaust from the gas turbine will produce steam for a
| chain of steam turbines with decreasing working
| temperatures.
|
| There should have been no problem in reaching a 65%
| efficiency for the conversion from heat to electricity,
| except that between hot sand and a gas burner there is
| the same difference as between an electric capacitor and
| a battery, while heat is extracted from the sand, it
| cools down.
|
| Presumably, when the sand becomes too cold, the gas
| turbine is bypassed and the hot air just produces steam.
| When it becomes even colder, I suppose that the first
| steam turbine is also bypassed and only the low-
| temperature steam turbines are used.
|
| This will lower the average efficiency, probably to
| around 50%. If the residual heat (after the steam
| turbines) had been used for heating or for cooling (i.e.
| heat-powered air conditioning), the efficiency could have
| been higher, e.g. over 80% in the beginning, while the
| sand is still very hot.
| ajb wrote:
| IIUC there is a physical limit from thermodynamics in
| converting back, based on the temperature. So when
| efficiencies are quoted, it could be either the
| proportion of input energy retrieved, or the proportion
| of the theoretical max efficiency achieved. I'm guessing
| you're quoting the former?
| Scoundreller wrote:
| Doesn't even need to be seasonal.
|
| Plenty of times+places where you only need heating at night
| and still have some net electrical draw (because the sun
| isn't shining at night).
|
| Also, cold fronts move in with a lot of wind, but then it can
| stay cold a few days with calm winds until a warm-front moves
| in.
| politician wrote:
| Nit: Rechargeable batteries have a loss when converting the
| chemical energy stored inside to electricity. There's no free
| lunch.
| cogman10 wrote:
| Yes, but for Lithium and sodium batteries you are looking
| at 90+ efficiency.
| 2OEH8eoCRo0 wrote:
| Is a battery electricity or is it a chemical reaction?
| westmeal wrote:
| you kinda can with sterling generators I think
| inetknght wrote:
| > _you can 't directly use heat for anything else other than
| for heating, where as electricity can be used to perform
| motion._
|
| Maybe today. But NASA has some interesting metal tires [0][1]
| which might change your mind for the future.
|
| [0]: NASA info https://technology.nasa.gov/patent/LEW-TOPS-99
|
| [1]: Neat youtube vid:
| https://www.youtube.com/watch?v=vSNtifE0Z2Q
| quickthrowman wrote:
| > you can't compare heat storage to electricity, because you
| can't directly use heat for anything else other than for
| heating
|
| You can use heat to generate steam that can spin turbines to
| perform work. But, I am not sure if it's practical to
| generate steam from a sand battery, my background is in
| electrical construction. I'm guessing the sand battery isn't
| nearly as hot as a natural gas steam boiler's combustion
| chamber.
|
| https://www.johnsoncontrols.com/en_sg/hvac-
| equipment/chiller...
| smallmancontrov wrote:
| Is absorption refrigeration bad enough to be permanently non-
| viable here? Or is it "just" a matter of scaling a niche
| technology?
| bumby wrote:
| Define "bad enough" in more specific terms.
|
| I believe it largely depends on the application. If you
| have a lot of waste heat, it's potentially a way to get
| "free" refrigeration. (e.g., a paper plant that uses a lot
| of steam can use absorption chillers to make use of waste
| heat.) If fuel is much cheaper than electricity, it can be
| economically viable. Peak shaving can save lots of money.
| etc. But it's probably not competitive purely in terms of
| energy efficiency or GHG emissions.
| smallmancontrov wrote:
| If I had exact figures, I wouldn't need to ask for
| anyone's intuition. Thankfully, ChatGPT was willing to
| work with me, and I will summarize the results here.
|
| Typical refrigeration COP (Coefficients of Performance):
|
| Absorption refrigerator: 0.6-1.2
|
| Compressor refrigerator: 1.5-4.0
|
| Estimated TES economic advantage: 1.1-2.5x
|
| Conclusion: yes, absorption refrigeration is probably
| inefficient enough to make it a long shot in this
| application. The only way I can see it becoming viable is
| if extremely hot TES can completely change the efficiency
| game, and then only just.
| bumby wrote:
| The temperature in TFA are outside the range of most
| commercial absorption chillers, so this is more about
| making cheap electricity. I would imagine absorption
| would be more applicable if the same tech was used to
| generate lower-quality heat that's not suitable for a
| combined-cycle generator.
| stcredzero wrote:
| _because you can 't directly use heat for anything else other
| than for heating_
|
| There's Stirling Engines. If the solar collection is pure
| thermal, and if that collection and the storage can be made
| dirt cheap, then the 37% or so efficiency of conversion to
| electricity stops being a problem. But what are currently
| problems with Stirling Engines -- Hardly any of the
| industrial optimization has been applied to them Re: Wright's
| Law. So they are quite costly! Heat pipe solar thermal could
| be made dirt cheap through economies of scale, and it works
| very well, even in climates like England's.
|
| I could envision house construction changing to include sub-
| basements which are just polystyrene insulated boxes filled
| with sand. By over-provisioning storage by 4X, houses in cold
| climates could have huge electrical power stores, especially
| in summer. (Especially if the house uses heat exchangers
| which can draw directly from the thermal store.)
| usrusr wrote:
| But that doesn't really matter before all heating demand is
| served from storage. Sure, heat will never be the be all end
| all of energy storage, but there's _a lot_ of demand in
| places that have winter. On top of this, when the conversion
| to heat is done by heat pumps, you not only get the benefit
| of a warmer baseline during the conversion, you also get some
| free cooling while charging.
| adrian_b wrote:
| Heat can be used directly not only for heating, but also for
| cooling.
|
| There are air conditioning systems that are powered by heat,
| not by electricity.
|
| There are places where the power plants use the residual heat
| from the generation of electricity not only for heating
| during the winter, but also for cooling during the summer, by
| producing chilled water.
| autoexecbat wrote:
| > There are air conditioning systems that are powered by
| heat, not by electricity.
|
| How does that work?
| xkcd-sucks wrote:
| https://en.wikipedia.org/wiki/Absorption_refrigerator
| jaggederest wrote:
| Half of all primary energy usage is for heating purposes.
| Heat is the best format to displace, as well, since a
| significant chunk of all that primary energy use is direct
| fossil fuel combustion right now.
|
| Especially since you can use heat to drive a heat pump, which
| ends up actually achieving above unity efficiency effectively
| since the heat input is used to move additional heat from the
| environment. Even if it's inefficient, if the heat would
| otherwise have been wasted, it's a net benefit.
| stingraycharles wrote:
| Gravity seems much more natural to me than heat; eg pumping
| water up a dam and releasing it again when you need the energy.
|
| It strikes me that heat has the problem that it always loses
| energy in its "stable state" because the surrounding
| environment absorbs the heat, and gravity doesn't have this
| problem.
| scotty79 wrote:
| With water you lose some due to evaporation.
| sgc wrote:
| That was my first thought too. But lakes lose ~20% / year
| to evaporation, and with the use of shade balls that is cut
| by ~90%, so we are at 2% / year - which is about the same
| as very efficient daily loss from heat storage.
| pfdietz wrote:
| If the heat is being turned back to electricity, a heat
| sink is needed and if this is done by evaporation the
| water loss will greatly exceed that of natural
| evaporation from a PHES facility.
| sgc wrote:
| It's not the evaporation per se that matters in the
| pumped hydro, it is the evaporation loss of water you
| already invested in pumping, so it is just an efficiency
| loss. The vapor loss for the heat sink is indirect, you
| usually just calculate the turbine efficiency. I don't
| know if the (generally much smaller) pumping requirements
| for turbines is already included in their efficiency
| calculations, but it would need to be of course.
|
| Either way, it just goes to show further that pumped
| hydro would be more efficient, when and where it is
| feasible.
| usrusr wrote:
| With a mineshaft gravity storage you could actually try to
| spin up a convective loop powered by geothermal that dries
| the sand over time, allowing you to lift dry sand when
| charging and abseil heavier wet sand when discharging.
| mecsred wrote:
| The issue of finding a location that has dramatic elevation
| change, a basin capable of storing vast amounts of water, and
| a suitable source/sink for pumping make pumped hydro
| difficult to deploy. Then there are additional logistics
| challenges such as environmental damage and proximity to
| human settlements for maintenance and engineering teams
| (prior challenges mean you don't really get to select the
| locations).
|
| Heat sinks meanwhile can be built wherever you have a big
| rock by drilling some holes. Additionally, gravity definitely
| does lose stored energy in its "stable state", through
| evaporation and water entering the water table. Losses depend
| on geology and local climate, but it's not negligible.
|
| Not to say that pumped hydro is a bad technology, it's just
| got it's own challenges and uses. It's most applicable in the
| form of electrical grid storage. But specifically on the
| scale of keeping towns and cities warm, heatsinks outperform
| almost across the board.
| sandworm101 wrote:
| And, if you inundate an area of wilderness to create
| reservoir you have to also count the lost carbon capture of
| the growing plants, and the significant methane emissions
| of the now dead and rotting plant matter under the water.
| In dry deserts this may be negligible, but the mountains
| where people most want to install hydro projects are
| generally very forested.
| pfdietz wrote:
| The "vast basin" part of that is an exaggeration.
|
| Look at https://www.whitepinepumpedstorage.com/ and the
| sizes of the upper and lower reservoirs there. This is to
| be a 8 GWh, 1 GW facility.
| mecsred wrote:
| "vast" is a pretty non specific word so I can maybe see
| why you would think that? I feel like it's pretty obvious
| from context I'm not talking about an inland sea here.
| The quoted 5000 "acre-feet" in that project is a
| considerable amount of water for a man-made structure!
|
| Either way, the details page[1] supports all of my above
| points. It even comments on the page how rare it is to
| find a suitable site like the one they've chosen.
|
| [1]https://www.whitepinepumpedstorage.com/project-details
| standeven wrote:
| Pumped hydro is great, but the potential energy from gravity
| is actually really low. Stacking blocks will probably never
| work, and pumped hydro only works due to scale and existing
| geography. It's also not modular and can't be co-located with
| generation or loads unless the geography works out.
| syllablehq wrote:
| Terrament is working on a modular gravity storage solution
| that uses deep mine shafts to gain 20x more height than
| stacking blocks above ground. So you don't need water or
| mountains. And since gravity storage uses ballast that is
| really just dumb weight, it could even be economical to make
| that ballast a secondary storage like thermal storage.
| lambda wrote:
| Pumped hydro is great, but only in certain areas where you
| already have the elevation gain available.
|
| Compressed air storage is another one that's pretty good, but
| it's only particularly good if you can store it in
| underground caverns or unused mines, so it's also geography
| dependent.
|
| For longer term storage, producing hydrogen can be a good
| one.
|
| And batteries are actually fast becoming competitive with
| some of these options from the other end, generally better
| for shorter term storage but getting better at longer term.
| Even shorter term, flywheels can be a good option.
|
| There's room for several different types of grid-scale energy
| storage, based on how efficient they are at different energy
| storage periods and numbers of charge-discharge cycles, and
| also in some cases on local conditions, like the availability
| of terrain and water sources for pumped hydro.
|
| There's a good paper here which shows what the most efficient
| energy storage systems are for various combinations of length
| of storage (hours per discharge) against number of discharges
| per year, and for each one shows the current cost, and a
| predicted cost based on trends in technological advancements:
| https://www.sciencedirect.com/science/article/pii/S254243511.
| ..
|
| There's a lot of the chart that is dominated by pumped hydro
| currently, but plenty of other storage technologies that are
| more cost effective on different timescales and numbers of
| discharges. But it looks like it's predicted for prices of
| battery storage and hydrogen storage to fall relative to the
| others, causing a different predicted landscape in 20 years.
|
| And some of these, like pumped hydro, are dependent on
| geographic features, or access to certain resources, so even
| when one dominates overall, there can be others that dominate
| in particular geographical regions.
| bumby wrote:
| An extrapolation directly to heat transfer is the Biot number
|
| https://en.m.wikipedia.org/wiki/Biot_number#:~:text=The%20Bi...
| .
| today20201014 wrote:
| > the ratio of the volume to surface area decreases the larger
| you make a container
|
| Did you mean to write the reverse? i.e the ratio of the surface
| area to volume decreases the larger you make a container.
| hardlianotion wrote:
| Yes.
| adverbly wrote:
| I also think this is a very interesting approach to take. This
| might be a pipe dream but it would be really cool if we could
| just turn a big chunk of desert into a battery by plumbing some
| heat exchangers through it.
|
| Or maybe just putting a gigantic Fresnel lens in the desert and
| pointing it at the ground. I almost wish someone would try this
| just to see what would happen.
| nick238 wrote:
| Love the idea. Hate the acronym...ENDURING, short for "Economic
| loNg-DURation electrIcity storage by using low-cost thermal
| energy storage aNd hiGh-efficiency power cycle"?
| ELDESbULCTESaHEPC.
| scotty79 wrote:
| It could be interesting to burry heating coils in the ground
| under the house and maybe dig deep, insulated petimeter
| foundation to better keep the heat inside. Power them with solar
| of course at times of negative prices.
|
| Or dig out a deep cellar, insulate on the sides and a the bottom
| against heat loss and moisture and put back the earth you dug out
| with heating element in the center. You don't even have to
| insulate wires that go through earth to the heating element
| because electricity passing through earth will get turned to heat
| as well.
|
| It might be nice additional heating for cooler climates.
|
| If you dug deep enough to have actual cellar on top of that you'd
| have a very warm cellar, you could put underground swiming pool
| there.
| throwitaway222 wrote:
| Seems to me that direct battery storage research is a much much
| much MUCH better use of government research funding. Sure if you
| want to use sand heat holders for heating houses, fine.. but for
| conversion to electricity? bleh
| leecarraher wrote:
| it seems the primary benefit for sand over water, is a 1:10
| operating temp vs. 5:1 specific heat. So it depends on whether
| the added complexity of working with a hotter, solid is worth not
| having to build a facility that is 2x bigger. Are there other
| benefits I'm missing, or is this concrete block gravity storage
| vs pumped water storage, all over again?
| nick238 wrote:
| Comparing water's 4.18 kJ/kg-K * ~75 K (25 degC -> 100 degC) to
| the sand's 1.1 kJ/kg-K * 900 K?
|
| I think you can (or it's easier) get more useful work out of a
| lesser amount of hotter stuff, even if the thermal energy or
| total heat is the same. Unsure of that, I don't know what the
| specific principle is. I'd vaguely gesture at the 2nd law of
| thermo as if I poured a cup of boiling water into a pot of
| room-temperature water, the total heat leaving the pot would
| wind up being the same as the heat leaving the cup, but less
| useful?
| NegativeK wrote:
| Sand doesn't leak down or up (via evaporation) nearly as much.
|
| It's also far less of a precious resource and non-corrosive,
| compared to the most common version of water.
| hamilyon2 wrote:
| What if we grind asteroids and send bags of sand from orbit? Sand
| will overheat while falling giving us free energy and sand. Sand
| is valuable.
| bugbuddy wrote:
| Whatever you are on, I need some of it. It must be good.
| spywaregorilla wrote:
| Also an unstoppable onslaught of kinetic weapons
| kylehotchkiss wrote:
| Like a giant Turkish coffee stove?
| pfdietz wrote:
| Here are some informative slides on the technology from 2021:
|
| https://arpa-e.energy.gov/sites/default/files/2021-03/07%20D...
|
| Previously linked at
| https://news.ycombinator.com/item?id=28451131
| spxneo wrote:
| I go to the beach fill up 50 gallon drums with it and then pipe
| hot water through it so that you can enjoy heat without
| electricity or gas.
|
| im obsessed with it. i love the way it feels on my body. i take
| warm sand baths with it. i have cold feet so i use nylon socks,
| fill it with sand providing endless massage and keeping it warm.
|
| ive yet to try different types of sand from other regions but
| Canadian beach sand does the job.
| dsp_person wrote:
| i can't tell if you are trolling or not
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