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.

[–] antrosapien@lemmy.ml 1 points 7 months ago (1 children)

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

[–] evranch@lemmy.ca 5 points 7 months ago (1 children)

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

[–] antrosapien@lemmy.ml 2 points 7 months ago

Fucking amazing😮😮 Write a blog if you document things.. Might come handy to beginners

[–] wizzor@sopuli.xyz 1 points 7 months 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.