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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

#41

Post by dragontamer »

0cf8612b2e1e wrote: post #23
dragontamer wrote: post #4

Earlier quoted context omitted.

IceBear went out of business with the opposite tech: tanks of water storing the cold generated from excess AC cycles. Cheap electricity can make cold, and then a fan can convert the cold water into cold air during peak hours when electricity was costlier. Fans still took electricity to run, but it'd only be a few hundred watts to run air-conditioning rather than kilowatts of power.

How long ago was this? The idea seems simple enough and would really benefit from the increasing glut of renewables. Even better, unlike a sand battery, you can potentially cycle it for several months of summer, by offsetting consumption by just a few hours feels like it could be economically viable. Then again, the competition is general purpose batteries which can be used all year and probably require less maintena…

It definitely seems economically viable to me

I'm hoping someone recreates it. It's just a few fans, a tub of water, a pump, and a slightly modified heat pump/air conditioner unit that can safely run down to 50F or so.

It's already viable for stadiums and other public events.

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

#42

Post by dragontamer »

llm_trw wrote: post #33
0cf8612b2e1e wrote: post #23

Earlier quoted context omitted.

How long ago was this? The idea seems simple enough and would really benefit from the increasing glut of renewables. Even better, unlike a sand battery, you can potentially cycle it for several months of summer, by offsetting consumption by just a few hours feels like it could be economically viable. Then again, the competition is general purpose batteries which can be used all year and probably require less maintena…

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.

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

#43

Post by Valgrim »

gorpy7 wrote: post #35

Ben_bai said it pretty well. water is good but it can cause rust, pressure, freeze, leak, etc. sand avoids most of this. the big thing is that sand can be heated much much hotter and this helps make up for its shortcomings relative to water. they likely charge and discharge with air blowing thru stainless steel network of pipes thru the sand. this would require special tuning. as someone else mentioned, the thing wit…

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 during the day is slowly released over time directly through the metal.

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

#46

Post by immibis »

Valgrim wrote: post #43
gorpy7 wrote: post #35

Ben_bai said it pretty well. water is good but it can cause rust, pressure, freeze, leak, etc. sand avoids most of this. the big thing is that sand can be heated much much hotter and this helps make up for its shortcomings relative to water. they likely charge and discharge with air blowing thru stainless steel network of pipes thru the sand. this would require special tuning. as someone else mentioned, the thing wit…

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.

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

#47

Post by tonyarkles »

dragontamer wrote: post #6
photonbucket wrote: post #5

I'm curious about "why sand", is it better at holding heat than say water?

Probably not. But sand doesn't freeze (or perhaps, sand doesn't melt) under normal temperatures. That's probably more important for an icy region.

Probably not relevant to the specific problem at hand because sand that's getting heated to 600 degrees is going to quickly boil off any residual moisture. As a warning, though, so that people don't experience the pain I got to experience, a pile of sand is really good at holding onto water internally and freezing when it gets cold. We had to replace our sewer line a while back and for various reasons were taking care of filling the hole and redoing the concrete ourselves. The sand guys left a big pile in the driveway for us and as soon as winter came the whole pile turned into a single giant rock despite having been out in the hot sun previously.

Exactly to your point, though, one of the great things about using sand for this application instead of water is that you can probably just shut the thing off for maintenance without having to worry about draining all of the sand out. If it freezes up due a bit of residual moisture content it's not going to expand nearly the same way that a silo full of water would, and it should be easy enough to thaw out just by putting some heat into it.

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

#48

Post by bumby »

dragontamer wrote: post #41
0cf8612b2e1e wrote: post #23

Earlier quoted context omitted.

How long ago was this? The idea seems simple enough and would really benefit from the increasing glut of renewables. Even better, unlike a sand battery, you can potentially cycle it for several months of summer, by offsetting consumption by just a few hours feels like it could be economically viable. Then again, the competition is general purpose batteries which can be used all year and probably require less maintena…

It definitely seems economically viable to me I'm hoping someone recreates it. It's just a few fans, a tub of water, a pump, and a slightly modified heat pump/air conditioner unit that can safely run down to 50F or so. It's already viable for stadiums and other public events.

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 electricity rate.

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

#49

Post by Gigachad »

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?

Less politically radicalised maybe? America should have all the tech and resources required to pull this stuff off, but it just doesn’t happen.

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

#50

Post by shellfishgene »

ben_bai wrote: post #20
photonbucket wrote: post #5

I'm curious about "why sand", is it better at holding heat than say water?

It's more effective volume wise. I did the math, some time ago here are the rough numbers. Sand has way less heat capacity then water per kg (about half). Water can be heated to 95C with standard unpressurized vessel. Sand in this application is heated to 600C. Sand is denser then water (kg/m3). For the same heat energy stored this comes out to about 2.5x more volume of water(95C) compared to sand(600C). Water and Sa…

The temperature also matters. If you need at least 50 C water to run district heating, about half of the energy stored in near boiling water cannot be utilized. This is much less with 600 C sand.
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