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Giant 'sand battery' holds a week's heat for a whole town

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Re: Giant 'sand battery' holds a week's heat for a whole town

#71

Post by defrost »

mercutio2 wrote: post #69
immibis wrote: post #46

Earlier quoted context omitted.

Any system that involves an electrical solar panel connected to a low-temperature electrical heater is likely to be better served with a solar hot water panel, by about a 10:1 ratio.

Are you including the maintenance costs of the water panel in your estimate? I used to buy this argument, but then: A) PV panels got ridiculously cheap B) everyone I know with solar hot water has emptied their systems because the maintenance hassles were not worth dealing with Using high grade intermittent current to produce resistive heat isn’t high on my list of efficient things to do, but unfortunately neither is…

Might be a location thing; there are vast numbers of solar hot water systems here in W.Australia and typical maintainence is maybe just replace the tank outright and flush the lines every 20 years or so.

How 'clean' of salts, etc. is the water being put through your panels?

Hard water clogs up faster.

Re: Giant 'sand battery' holds a week's heat for a whole town

#72

Post by m463 »

I get that sand is inexpensive and simple and I like the idea - especially since it scales to an entire town (!)

But I can't help but think of one "technology" that could make a scheme like this MUCH more effective.

a phase change.

for example, it takes 1 calorie for water to go from 30 to 31 degrees F, but but it take 80 calories to go from solid at 32 to liquid at 32 F.

A project I remember reading about that was really interesting was a house constructed with logs that had a resin that phase changed around room temperature. The idea was that the logs would be heated by sunlight, and the resin in the logs would absorb lots of energy without easily going above room temperature. Then at night, they would slowly solidify and give off heat at room temperature. This would be a cool way to stabilize house temperatures without needing equipment.

EDIT: it was called the enertia house

I'm uncertain of the history, it seems there are a lot of different "enertia house" search hits.

Here's one explaining the idea:

https://enertia.net/howitworks.html

Re: Giant 'sand battery' holds a week's heat for a whole town

#73

Post by hanniabu »

chiph wrote: post #38
pfdietz wrote: post #15

NREL's ENDURING sand battery, storing heat at 1200 C in quartz sand. Round trip efficiency using turbines is estimated at ~53%. https://arpa-e.energy.gov/sites/default/files/2021-03/07%20D... The IP has been licensed by Babcock and Wilcox, who are the source of the nifty compact fluidized bed heat exchanger.

It's an interesting concept. Cheap. Doesn't take up a lot of space. Could be driven by a solar furnace. My concern is whether the cyclone particle separator will do a good enough job - gas turbine blades don't like being blasted with grit. I expect they'd need a heat exchanger to be sure to get only clean gas driving the turbines.

> Cheap.

Until patents are involved

Re: Giant 'sand battery' holds a week's heat for a whole town

#74

Post by Danieru »

dragontamer wrote: post #66
bumby wrote: post #48

Earlier quoted context omitted.

This has been around for a long time. The Detroit VA hospital used it, I believe with tanks under the parking structure. I also believe there were problems related to the maintenance of the tanks. But the important aspect is that this is a cost saving technique, not an energy saving one. You’ll spend more energy because of the thermal losses of the tanks, but hopefully it is more than offset by the cheaper electricit…

Energy is (sometimes) free, or even negative priced (!!!!). As it turns out: it's economically infeasible to turn off solar panels, wind, nuclear and sometimes Hydro (depending on water rights, it may be illegal to store water/energy at a water dam). In all of these cases, the energy is 0 cost or even negative cost.

You're confused, negative prices are not driven by techincal limitations. Solar, and especially hydro, and even nuclear can shut down just fine.

Solar and Wind instead drive prices negative because they have subsidized contracts. Each country is slightly different in implementation, between Feed-in-Tarif vs Feed-in-Premium. In either method there will exist prices which are negative to the market but positive to the producer.

Thus if you cannot plan long term to rely on negative prices. Those FIT schemes around the world are transforming into FIP, and the FIP premiums are getting lower and lower. Negative pricing in electricity markets will go away in a decade or two. This isn't magic or even special, solar is succeeding which means the subsidies are getting weakened.

Curtailing solar production is not a big deal. How many existing plants have grid operator directed shutoffs depends on your market. In Japan as of 2024 all new non-rooftop solar has it. Prior to 2020ish only Kyushu and Kansai regions required it. Now Tepco, Hokkaido, and Touhoku require it for new contracts. There are still a couple old contracted plants getting developed this year, but those are rarities.

And that's only Japan, which itself does not have a super strong duck curve yet: http://jepx.org/ Regions like California have had extreme duck curves for ages. While duck curves are a big worry for internet commentors, they've been points of discussion for grid operators are a lot longer. Hence the move to Feed in Premiums which will slowly make the duck curve a solar operator's problem and not a tragedy of the commons situation.

Re: Giant 'sand battery' holds a week's heat for a whole town

#75

Post by Retric »

immibis wrote: post #46
Valgrim wrote: post #43

Earlier quoted context omitted.

Some Youtube folks tried a much simpler approach: Take a large metal bucket or barrel. Put a heating element and a simple oven thermostat on the bottom. Fill with sand. Connect to a solar panel or other enrgy source. The air between the sand particles seem to actually provide a bit of convection and insulation. The thermostat turns the circuit off before getting too hot for the heating element. The heat accumulated d…

Any system that involves an electrical solar panel connected to a low-temperature electrical heater is likely to be better served with a solar hot water panel, by about a 10:1 ratio.

More like 4.5:1 solar is 20% or so efficient and solar thermal is only like 90% when including losses.

Anyway, the real question here costs both in equipment and labor. Solar hot water panels involve plumbing and need radiators etc they quickly pay for themselves when heating a large home but don’t scale down very well.

Running the numbers I was surprised how cost competitive the sand bucket is for something like a chicken coop. Sure the panel(s) are wasted most of the year, but you don’t exactly need an electrician to set this up either. Probably also worth considering for redundancy in some situations.

Re: Giant 'sand battery' holds a week's heat for a whole town

#76

Post by jessriedel »

m463 wrote: post #72

I get that sand is inexpensive and simple and I like the idea - especially since it scales to an entire town (!) But I can't help but think of one "technology" that could make a scheme like this MUCH more effective. a phase change. for example, it takes 1 calorie for water to go from 30 to 31 degrees F, but but it take 80 calories to go from solid at 32 to liquid at 32 F. A project I remember reading about that was r…

There's a pretty cool coffee mug based off the idea too

https://joeveo.com/pages/the-temperfect-mug

Re: Giant 'sand battery' holds a week's heat for a whole town

#77

Post by ImPostingOnHN »

jessriedel wrote: post #76
m463 wrote: post #72

I get that sand is inexpensive and simple and I like the idea - especially since it scales to an entire town (!) But I can't help but think of one "technology" that could make a scheme like this MUCH more effective. a phase change. for example, it takes 1 calorie for water to go from 30 to 31 degrees F, but but it take 80 calories to go from solid at 32 to liquid at 32 F. A project I remember reading about that was r…

There's a pretty cool coffee mug based off the idea too https://joeveo.com/pages/the-temperfect-mug

Coffee Joulies work off the same concept

https://www.baristamagazine.com/coffee-joulies-engineered-so...

Re: Giant 'sand battery' holds a week's heat for a whole town

#78

Post by hnaccount_rng »

anonu wrote: post #44

It feels that Europe is so far ahead the US in matters of environmental sustainability. Why is that? Is it more dense than the US, so they need to be more careful with resources?

It's also that the infrastructure of the US is very young. In Europe a 100 year old building is shockingly common. And they are still in use. Mostly because even back then (some) housing was already build in a lasting manner. And not being able/willing to tear them down gives you a baselevel of sustainability.

The other thing is that we used up most of "our" fossil energy reserves decades ago and what we want to burn today requires imports, which requires a reasonably stable world economy, a reasonably strong geopolitical position and ... well ... even the last conservative governments have woken up, that those assumptions may not be true any longer

Re: Giant 'sand battery' holds a week's heat for a whole town

#79

Post by sudhirj »

m463 wrote: post #72

I get that sand is inexpensive and simple and I like the idea - especially since it scales to an entire town (!) But I can't help but think of one "technology" that could make a scheme like this MUCH more effective. a phase change. for example, it takes 1 calorie for water to go from 30 to 31 degrees F, but but it take 80 calories to go from solid at 32 to liquid at 32 F. A project I remember reading about that was r…

Phase changes will probably work well for structures that would otherwise be used for insulation anyway - in the case of this particular idea though, I think heat is moved in and out using another medium, air in this case, so a phase change would complicate things greatly (hard to bubble air through lava). But yeah, something like a phase changing fluid (gas liquid) will probably work well, as it does in air conditioners right now.

Re: Giant 'sand battery' holds a week's heat for a whole town

#80

Post by usrusr »

m463 wrote: post #72

I get that sand is inexpensive and simple and I like the idea - especially since it scales to an entire town (!) But I can't help but think of one "technology" that could make a scheme like this MUCH more effective. a phase change. for example, it takes 1 calorie for water to go from 30 to 31 degrees F, but but it take 80 calories to go from solid at 32 to liquid at 32 F. A project I remember reading about that was r…

Phase change heat storage is well established techology. It's in the product you buy when you want to have building scale latent heat storage. I've even seen a company trying their luck at the business model of selling heat in twenty foot equivalents, e.g. for building sites. So it's safe to assume that they knew about this option. But there's also the square-cube-law, at some point it will be cheaper to insulate a larger volume of the cheaper material than a smaller volume of a material that requires less volume per unit of energy at the heat range you aim at. It's well possible that this line is between building-scale and grid-scale storage.
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