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consider the implications for a post scarcity future (slrpnk.net)
submitted 2 years ago by to c/solarpunk@slrpnk.net
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[–] 9 points 2 years ago (8 children)

This has me thinking

The resurgance of sand batteries has been interesting. While not great for converting back into electricity, it's great for heating and cooling which is a massive portion of our energy consumption. They can also store quite a ton of energy with crazy efficiency, especially when paired with heat pumps. And from what I've been able to deduce, they aren't dependent on beach sand and can use rougher or man-made sand reliably.

First if we could get enough large buildings and neighborhood/home installation sand battery heating & cooling infrastructure operating with heat pumps. Then when during high times of energy production we can dump the energy into the sand battery infra and help keep the grid stablizied and keeping our heat & cooling overall percentage of use down.

In the end, we're going to need tons of solutions and strategies for storing excess production during low demand times. I'm hopeful to see where we go here, the crazy things were seeing in energy storage is extremely interesting. I'm super excited to see the advances were seeing in calcium and sulfur based batteries expand in adoption and the production lines can scale with demand.

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  • [–] 7 points 2 years ago (4 children)

    I've been really curious about the possibility of a small DIY sand battery type system. I currently store my "negative value" midday solar power by dumping it into a water tank and using it to feed my hydronic heating system.

    However as we know that results in a tank containing useless low-grade heat on a cloudy day, where a sand battery would result in a small amount of usable high-grade heat.

    The cooling equivalent could actually be implemented fairly easily at home with common consumer ice machines (which are effectively heat pumps). Make ice when there's surplus, dump it in an insulated hopper with a heat exchanger for night-time cooling, recycle the near-freezing melt water to make ice the next day. Water is a lot easier to handle because it can be pumped instead of conveyed, and you get the advantage of phase change storage.

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  • [–] 1 point 2 years ago

    I have been running the numbers on one myself and it seems to me the best case would be to actually have one inside my home, since the waste heat will also end up heating the space. I admit it is similar to just having a lot of thermal mass in the house.

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  • [–] 1 point 2 years ago (2 children)

    That's really interesting you're storing power. Was it diy??

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  • [–] 5 points 2 years ago (1 child)

    Entire system is home built and programmed except the inverter which was a surplus rack-mount.

    The dump load in the water tank tracks the battery bank voltage, drawing more power as the voltage rises into the float range. This is used to sense available surplus power, which is used to turn on other dump loads, i.e. air conditioning in summer.

    I have a couple window units that are cranked to max cooling and come on in sequence as the surplus power rises, on an early summer day with clear skies it can get to the point of needing a sweater in the house :D I'm migrating to a homebuilt multi-stage heat pump this year after the prototype worked quite well last year.

    Also seriously considering the ice storage concept for hot nights, though I might need to make an actual ton of ice!

    Just made a deal on 8 massive surplus AGM batteries too to refresh my bank

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  • [–] 1 point 2 years ago (2 children)

    Yes, also it doesnt technically have to be sand, there are concrete mixes and even just bedrock that can be used for similar purposes. I've been looking at sand batteries myself for this reason: run the battery hot when power is cheap, let it cool when not.

    This sort of thing is of course why it's useful to have a market mechanism for energy, it can encourage us to build environmentally friendly solutions.

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  • [–] 1 point 2 years ago (1 child)

    Actually a modern "sand battery" does have to be sand or at least a granular material. The difference between a sand battery and thermal mass is that you use a conveyor to superheat small fractions of the sand, allowing the isolation of high grade heat.

    If you have a single kWh to store and 1 ton of sand to work with, you could heat 1kg of sand to hundreds of degrees (sand battery), or 1 ton of sand by one degree (thermal mass).

    1 ton of slightly warm sand is useless, while you can extract the high grade heat from the 1kg and get your 1 kWh back.

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