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US Government funds pilot project for heated sand energy storage

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Re: US Government funds pilot project for heated sand energy storage

#71

Post by foreverobama »

datameta wrote: post #38
chii wrote: post #33

Earlier quoted context omitted.

> 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.

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?

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Re: US Government funds pilot project for heated sand energy storage

#72

Post by nick238 »

leecarraher wrote: post #62

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?

Comparing water's 4.18 kJ/kg-K * ~75 K (25 °C -> 100 °C) 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?

Re: US Government funds pilot project for heated sand energy storage

#73

Post by stcredzero »

chii wrote: post #33
retrac wrote: post #28

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…

> 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.

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.)

Re: US Government funds pilot project for heated sand energy storage

#74

Post by usrusr »

chii wrote: post #33
retrac wrote: post #28

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…

> 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.

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.

Re: US Government funds pilot project for heated sand energy storage

#75

Post by nick238 »

pfdietz wrote: post #14

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.

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?

Re: US Government funds pilot project for heated sand energy storage

#76

Post by pfdietz »

mecsred wrote: post #41
stingraycharles wrote: post #34

Earlier quoted context omitted.

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.

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…

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.

Re: US Government funds pilot project for heated sand energy storage

#77

Post by pfdietz »

sgc wrote: post #59
scotty79 wrote: post #40

Earlier quoted context omitted.

With water you lose some due to evaporation.

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.

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.

Re: US Government funds pilot project for heated sand energy storage

#79

Post by clort »

non-chalad wrote: post #19
seanmcdirmid wrote: post #15

Earlier quoted context omitted.

How does this compared to pumped storage?

You can pump sand by bubbling compressed air through it. 1. https://www.youtube.com/watch?v=My4RA5I0FKs

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...)

Re: US Government funds pilot project for heated sand energy storage

#80

Post by sgc »

pfdietz wrote: post #77
sgc wrote: post #59

Earlier quoted context omitted.

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.

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.

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.

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