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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

#131

Post by darkerside »

nimos wrote: post #130

Been curious if you can't do this with houses generally. Set a temperature range of say 21-25c. Drive the temperature up when there is excess wind/solar (was primarily thinking of EU) then let it fall off. Obviously works better the better insulated a house is. Has the advantage of turning everything in your home into a thermal battery with the only real cost being furnace controller, potentially even just software.…

Real estate is precious. You really want a massive heat battery taking up a lot of living space?

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

#133

Post by ametrau »

onetimeuse92304 wrote: post #127

100MWh = 3.6 * 10^11 joules sand's heat capacity = 830 J/kg degree C sand battery size is "13m tall and 15m wide". Assuming most voluminous possible shape that's 13m * 15m * 15m = 2925 cubic meters of sand (100% fill, no account for insulation, etc.) Dry sand density is about 1600kg/m3 Total weight of sand would be 2925m3 * 1600kg/m3 = 4.7Mkg (4.7kt) 4.7Mkg of sand has a heat capacity of 830J/kg * 4.7Mkg = 3.9 * 10^9…

They heat the sand to 600c. But you could just use more water. I don’t get it also.

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

#134

Post by nimos »

locallost wrote: post #121

Would it make sense to actually store it underground, or are the gains minimal when compared to the costs? In general, I'm impressed that there's so much research and investment in this field (storing excess renewable energy). I think most people don't realize how much and that the problem of the sun not shining and wind not blowing all the time will be solved much more quickly than most people think is possible.

https://en.wikipedia.org/wiki/Drake_Landing_Solar_Community

There was an experimental community in Alberta, Canada doing this. Seems to be relatively successful as pilot project.

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

#135

Post by dgacmu »

ametrau wrote: post #133
onetimeuse92304 wrote: post #127

100MWh = 3.6 * 10^11 joules sand's heat capacity = 830 J/kg degree C sand battery size is "13m tall and 15m wide". Assuming most voluminous possible shape that's 13m * 15m * 15m = 2925 cubic meters of sand (100% fill, no account for insulation, etc.) Dry sand density is about 1600kg/m3 Total weight of sand would be 2925m3 * 1600kg/m3 = 4.7Mkg (4.7kt) 4.7Mkg of sand has a heat capacity of 830J/kg * 4.7Mkg = 3.9 * 10^9…

They heat the sand to 600c. But you could just use more water. I don’t get it also.

Interesting! Wonder if it's also due to ease / lower risk of containment. And sand doesn't expand if you accidentally let it freeze, which is again nice from an "it won't rupture" perspective.

As to cost, the article does note that they're reusing crushed soapstone from a local byproduct, so maybe that helps reduce the cost?

That said, their FAQ says it's about heat capacity: https://polarnightenergy.fi/sand-battery

> Why do you use sand?

> Many solid materials, such as sand, can be heated to temperatures well above the boiling point of water. Sand-based heat storages can store several times the amount of energy that can be stored in a water tank of a similar size; this is thanks to the large temperature range allowed by the sand. So, it saves space and it allows versatile use in many industrial applications.

So perhaps they're also specifically targeting future applications where they would need to supply > 100C heat.

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

#136

Post by nimos »

dragontamer wrote: post #42
llm_trw wrote: post #33

Earlier quoted context omitted.

Just because something seems like should work doesn't mean it will. Air conditioners are simple and cheap to install. An insulated swimming pool in the basement is not.

1 cubic meters of water chilled 10C below ambient is 40MegaJoules of energy. Or in other words: 11kW-hrs of cooling, comparable to an entire Tesla Powerwall. We aren't talking about entire swimming pools here. Just a few cubic meters of water. Shift the temperature delta as you see fit but... It's actually very space efficient.

Air conditioners have a COP of about 3 though. So really its more like 3.5kwh of storage. If you want to go lower temperature to store more then your COP drops.

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

#137

Post by nimos »

darkerside wrote: post #131
nimos wrote: post #130

Been curious if you can't do this with houses generally. Set a temperature range of say 21-25c. Drive the temperature up when there is excess wind/solar (was primarily thinking of EU) then let it fall off. Obviously works better the better insulated a house is. Has the advantage of turning everything in your home into a thermal battery with the only real cost being furnace controller, potentially even just software.…

Real estate is precious. You really want a massive heat battery taking up a lot of living space?

I'm not suggesting adding anything. Homes have lots of stuff in them. Everything in your house becomes a thermal battery - tables, chairs, beds, walls, counters, clothes and so on. Just allow a range of temperatures and when energy is very low cost drive the indoor temperature to the upper range.

Ideally you have a brick/stone home with good exterior insulation.

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

#138

Post by Retric »

slow_typist wrote: post #85
Retric wrote: post #75

Earlier quoted context omitted.

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 c…

The monetary case of PV does not account for the damage that is done to the environment over the entire lifecycle. Solar hot water panels are ecologically superior. Not only are they more efficient in W/sqm. Their production is not as energy intensive (plumbing included), the recycling process is less complex, poisonous materials can mostly be avoided. If heat is the desired product, they probably beat PV by an order…

PV’s falling prices have also been associated with falling environmental harm. When you’re talking multiple orders of magnitude you just cannot require as much in production.

IE: You can’t burn 500 gallons of gas if the end product costs 500$. That applies not just to transportation but also how much material and thus mining the raw materials you need, including refining them, the amount of chemicals you can use per panel, how much electricity you can use in production of the device including precursors etc.

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

#139

Post by merelysounds »

onetimeuse92304 wrote: post #127

100MWh = 3.6 * 10^11 joules sand's heat capacity = 830 J/kg degree C sand battery size is "13m tall and 15m wide". Assuming most voluminous possible shape that's 13m * 15m * 15m = 2925 cubic meters of sand (100% fill, no account for insulation, etc.) Dry sand density is about 1600kg/m3 Total weight of sand would be 2925m3 * 1600kg/m3 = 4.7Mkg (4.7kt) 4.7Mkg of sand has a heat capacity of 830J/kg * 4.7Mkg = 3.9 * 10^9…

> But sand is quite expensive so my question is, why sand and not water?

The article says they will use a byproduct from a local industry, perhaps it's available for cheaper.

"The sand itself will also be sustainably sourced – it’ll consist of crushed soapstone, which is a manufacturing byproduct of another local industry. This material can apparently conduct heat even better than regular old sand.".

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

#140

Post by captainbland »

onetimeuse92304 wrote: post #127

100MWh = 3.6 * 10^11 joules sand's heat capacity = 830 J/kg degree C sand battery size is "13m tall and 15m wide". Assuming most voluminous possible shape that's 13m * 15m * 15m = 2925 cubic meters of sand (100% fill, no account for insulation, etc.) Dry sand density is about 1600kg/m3 Total weight of sand would be 2925m3 * 1600kg/m3 = 4.7Mkg (4.7kt) 4.7Mkg of sand has a heat capacity of 830J/kg * 4.7Mkg = 3.9 * 10^9…

They might get quite a good deal on types of sand which are no good for construction but are highly abundant like sea sand or desert sand.
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