Giant 'sand battery' holds a week's heat for a whole town • Hacker News Board

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

#51

Post by pfdietz » Thu, Mar 14, 2024, 2:01 AM UTC

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.

> Could be driven by a solar furnace.

Perhaps more interestingly, it could be driven by combustion of an e-fuel as a backup in case the sand becomes depleted.

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

#52

Post by gregwebs » Thu, Mar 14, 2024, 2:03 AM UTC

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?

Much of the US has access to cheap natural gas. And a good amount of oil. The greater the cost of energy the more it drives innovation in energy usage as well as incentivizes projects that would have a longer pay back period where energy is cheaper. Although Norway has abundant energy but socialized the profits and is using them to advance their usage of renewables and electrification. In the US we privatize the gains and only socialize the losses.

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

#53

Post by Dalewyn » Thu, Mar 14, 2024, 2:05 AM UTC

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…

For some reason this description sounds exactly like a computer, and specifically the CPU/GPU, and I love it.

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

#54

Post by kiney » Thu, Mar 14, 2024, 2:09 AM UTC

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…

Thats just a regular storage heater...

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

#55

Post by heyalexej » Thu, Mar 14, 2024, 2:18 AM UTC

Here's a smaller scale water battery that heats an entire house year round. The water tank itself is placed in the center of the house across all 3 floors and actually makes for a quite nice design element as well. The energy is generated in the warm seasons and the volume of water is large enough to last through the entire winter. It's a German vid but subtitles are quite accurate.

https://www.youtube.com/watch?v=MBLiNHsod8Y

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

#56

Post by zdragnar » Thu, Mar 14, 2024, 2:25 AM UTC

logtempo wrote: post #39

gorpy7 wrote: post #3

This is great technology, simple and effective. I’ve spent many hours reverse engineering to see how effective and expensive it might be. I’ve found it’s very cost effective but heat can be hard to calculate. i like that they did a prototype. i think i’ll do one at some point. for an individual house it makes more sense to improve my insulation but i think ill still build a small version for fun.

it's how "rocket stove" works: https://en.wikipedia.org/wiki/Rocket_stove Since you burn the wood really fast, you need to delay that heat release. That's where sand comes in as a cheap and good enough material. There are also systems that heat water and store it in a tank, which also make sense if you want hot water in your house too.

Sand is actually pretty bad. Gravel is a little better, clay is best.

Sand is really only useful here because that much clay is usually significantly more expensive and would take forever to dry out.

Source: researched the shit out of and have built a rocket stove.

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

#57

Post by taneq » Thu, Mar 14, 2024, 2:43 AM UTC

bumby wrote: post #48

dragontamer wrote: post #41

Earlier quoted context omitted.

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 electricit…

If you’re using renewable energy that would otherwise go to waste for lack of storage, then that’s definitely saving (useful) energy.

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

#58

Post by komali2 » Thu, Mar 14, 2024, 2:46 AM UTC

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.

> Air conditioners are simple and cheap to install

Today. In my chats with the sort of home improvement types that seem to be in this thread, we're less concerned with today and more concerned with the cost of things in the future, as societies include "climate taxes" (in the form of actual taxes, subsidies, or whatever else) in the cost of things.

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

#59

Post by at_a_remove » Thu, Mar 14, 2024, 2:50 AM UTC

I've been obsessed, mildly, with Feolite. It could be brought back for these sorts of applications to great effect. It's got the volumetric heat capacity of water and the ability to withstand much greater temperatures without any annoying phase transitions. It was very popular in the UK, where they went in early on charging for electricity on a rate varying by hour. The basic formula is easy, but there's a lot of secret ingredients to get the heat capacity way, way up.

Speaking of home uses and phase transitions, they have made inroads into making materials with a phase transitioned tuned to household temperatures. Say you have aimed for seventy-two Fahrenheit. The temperature gets higher than that? The material melts, absorbing ambient heat. Then, as the temperature dips below seventy-two Fahrenheit, it freezes, releasing heat. It would make a fantastic sort of "heat capacitor," designed to deal with rapid, small-scale temperature fluctuations, while larger heat batteries could deal with fluctuations over days, weeks, and so on.

Only problem is that these phase transition materials tend to be terrifyingly flammable, so far. Like soaking all of your drywall panels in candle wax before putting them up.

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

#60

Post by noqc » Thu, Mar 14, 2024, 2:52 AM UTC

bicebird wrote: post #25

I was thinking of ways to get around the peak solar generation being when you don't need it for heating and genuinely really heartening to hear about solutions like this. The article doesn't mention the costs or complexity in building each unit but definitely implies it's cheaper than storing it batteries, which makes sense if it's essentially a heating element buried in sand. Wonder what the smallest viable size wou…

Peak solar is peak A/C usage in the summer, which is typically more expensive than heating. In colder times more energy is used at night, but I think less energy is still used at night in the winter than in the day in summer.