Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

US Government funds pilot project for heated sand energy storage

pv-magazine.com

Post reply on HN
Print view View original

111–120 of 131 posts

Re: US Government funds pilot project for heated sand energy storage

#111

Post by credit_guy »

adrian_b wrote: post #89
NavinF wrote: post #48

Earlier quoted context omitted.

No way you'll get 65%. This sand won't be stored at the same temperature as a natgas generator's combustion chamber. Efficiency depends on delta T. I'd guess 20%

Nope. The report says that the sand will be heated up to 1200 Celsius degrees. This is much higher than the maximum temperature for steam turbines and equal to the temperature of the gas in the best gas turbines. Therefore they will use a combined cycle, first a gas turbine will use hot air passed through the sand and the exhaust from the gas turbine will produce steam for a chain of steam turbines with decreasing wo…

I did not read the report, but one way you can improve the round trip efficiency is to not let the sand cool below, let's say 1000 °C. You pay a one-time penalty of heating the sand to this temperature and then you operate the storage only between 1000 and 1200 °C. This reduces the capacity of the "sand battery", roughly by a factor of 6. But sand is (reasonably) cheap.

I have seen another proposal where instead of sand the material would be graphite, which can be heated to more than 2000 °C. Graphite also has a huge heat conductivity. But it's more expensive.

Re: US Government funds pilot project for heated sand energy storage

#112

Post by spxneo »

dsp_person wrote: post #99
spxneo wrote: post #84

I go to the beach fill up 50 gallon drums with it and then pipe hot water through it so that you can enjoy heat without electricity or gas. im obsessed with it. i love the way it feels on my body. i take warm sand baths with it. i have cold feet so i use nylon socks, fill it with sand providing endless massage and keeping it warm. ive yet to try different types of sand from other regions but Canadian beach sand does…

i can't tell if you are trolling or not

why would i be trolling?

Re: US Government funds pilot project for heated sand energy storage

#115

Post by zdragnar »

regularfry wrote: post #8
regularfry wrote: post #5

Earlier quoted context omitted.

I suspect it's because the thermal conductivity of sand isn't that great. If you've got your working fluid running through pipes embedded in hot sand, the system is likely bottlenecked on getting the heat energy from the main body of the mass through the cooler sand closest to the pipes. Do it the other way and the enormous surface area is working for you, so you can presumably get the energy out arbitrarily fast (or…

The thought occurs that if that is indeed the problem, you could attack it by mixing a metal in with the sand. You'd still get the thermal mass, but conductivity would no longer be a problem as long as it had been in a liquid phase at least once.

The problem isn't so much the sand, it's all the air gaps between the grains of sand.

Adding metal won't help any- once it gets to a liquid phase, it'll sink down, or if it doesn't stay liquid long enough, will just trap most of the air in it.

Edit: you'll also want to keep oxygen out of the environment in the liquid phase. Depending on the metal you use and the exact makeup of the sand, you'll wind up with some materials that are often used in refractory cement- aluminum, oxygen, and silicon will do the trick and absolutely ruin the effectiveness of your heat battery.

Re: US Government funds pilot project for heated sand energy storage

#116

Post by zizee »

credit_guy wrote: post #111
adrian_b wrote: post #89

Earlier quoted context omitted.

Nope. The report says that the sand will be heated up to 1200 Celsius degrees. This is much higher than the maximum temperature for steam turbines and equal to the temperature of the gas in the best gas turbines. Therefore they will use a combined cycle, first a gas turbine will use hot air passed through the sand and the exhaust from the gas turbine will produce steam for a chain of steam turbines with decreasing wo…

I did not read the report, but one way you can improve the round trip efficiency is to not let the sand cool below, let's say 1000 °C. You pay a one-time penalty of heating the sand to this temperature and then you operate the storage only between 1000 and 1200 °C. This reduces the capacity of the "sand battery", roughly by a factor of 6. But sand is (reasonably) cheap. I have seen another proposal where instead of s…

Sand has the added benefit over graphite of being nonflammable.

Re: US Government funds pilot project for heated sand energy storage

#117

Post by datameta »

zizee wrote: post #116
credit_guy wrote: post #111

Earlier quoted context omitted.

I did not read the report, but one way you can improve the round trip efficiency is to not let the sand cool below, let's say 1000 °C. You pay a one-time penalty of heating the sand to this temperature and then you operate the storage only between 1000 and 1200 °C. This reduces the capacity of the "sand battery", roughly by a factor of 6. But sand is (reasonably) cheap. I have seen another proposal where instead of s…

Sand has the added benefit over graphite of being nonflammable.

Sand will also benefit from greater insulation due to lower packing efficiency and therefore more air.

Re: US Government funds pilot project for heated sand energy storage

#120

Post by reify »

I love this idea

I have been following the progress of sand batteries.

So much so that I actaully made one at home.

https://hackaday.com/2022/11/21/making-a-do-it-yourself-sand...

I made some changes to this idea. I used a 12V supply from an old PC power supply to run the heat element in the sand. I used some course pool filter sand that I use for my aquariums.

I have a very chilly hallway with no radiator between my lounge and main entrance door.

It did work. Raised the temperature from 62F to a modest 70F. It took a few days to warm through and remain constant.

I see there are developments in Scandinavia to heat entire towns.

This is the good science I like to see.

Post reply on HN