Climate change: 'Sand battery' could solve green energy's big problem 1

[cmoreride]

Using low-grade sand, the device is charged up with heat made from cheap electricity from solar or wind.
The sand stores the heat at around 500C,

https://www.bbc.com/news/science-environment-61996520.amp

 

[stevenal]

The toughest question is about intermittency - how do you keep the lights on when the sun doesn't shine and the wind doesn't blow?

Anyone else notice the sand battery fails to address this problem?

 

[BridgeSmith]

I didn't make it past the OP's description of wind and solar as "cheap".

 

[TugboatEng]

The battery will be inexpensive to operate as well because there are no issues with circulating very hot sand through heat exchangers and conveyors.

 

[JoshPlumSE]

I believe this is a pretty similar concept to Bill Gates solar start-up for industrial applications.

https://www.cnn.com/2021/03/24/business/heliogen-solar-bill-gates-rio-tinto/index.html

 

[JoshPlumSE]

FWIW, I believe the Bill Gates / Heliogen solar concept is merely heating up rocks or such during the day when solar power is available in abundance then using these to generate power (at a lesser level) during the night.

It has SOME potential. The Heliogen concept is fairly similar to the Ivanpah plant, just without the gas powered turbine used to start it up or generate power when the sun isn't shining.

 

[TugboatEng]

It seems like they should chose a more ideal medium than "rocks". The thermal conductivity of rocks isn't very good which will limit power output. We see this already in geothermal. Water injection often used to stimulate dry wells. However, the rate of injection is critical as too much water will quench the well and it can take a very long time for the well to heat back up due to the poor thermal conductivity of the rock.

 

[GregLocock]

Hot water/heating is the bane of off grid systems in winter so they're looking at a sensible end use of the spare energy. I'm guessing they've got steel pipes in the sand, now I'm puzzled, they say they heat air with the sand, why not water, since that's what they want?

Cheers

Greg Locock


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[LittleInch]

"Why not water?"

Did you miss the bit about up to 600C?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[GregLocock]

Hot water, aka steam. 450 deg C was doable in a WW2 destroyer, don't tell me we've gone backwards!

Cheers

Greg Locock


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[TugboatEng]

Most Navy ships ran 600 psi plants for simplicity. A few destroyers got 1200 psi plants with separately fired super heaters in W boilers.

Us commercial sailors were cutting edge with our 950 psi plants. Then, oil got expensive. Diesel ships can burn MUCH lower quality oil than steamers. Bunker C is an obsolete product, IFO380, intermediate fuel oil 380 centistokes, is the closest alternative but very ashy in comparison. Meanwhile RMG 550 (residual marine, 550 centistokes, 980 gravity) is a popular diesel ship fuel. For longer trips there is RMK770 (residual marine, 770 centistokes, 1010 specific gravity). If you lose tank heating with that stuff you can't remelt it, it has to get shoveled out.

 

[LittleInch]

Greg, I agree it can be done, but if you can get the heat transfer you need with hot air its a lot less things to go wrong and look after.

For a pretty small pilot plant I can see why they didn't want high pressure steam / hot water flying around.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[GregLocock]

Yes I think the robustness argument has a lot going for it, especially for pilot project.

Cheers

Greg Locock


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[SnTMan]

It would seem they need to match design conditions of the existing district heating system?

EDIT: Of chourse they could do that with two water loops, they are apparently doing two now, one air one water. I guess

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[JoshPlumSE]

It seems like they should chose a more ideal medium than "rocks". The thermal conductivity of rocks isn't very good which will limit power output

For the Bill Gates / Heliogen situation, I believe this was being developed for (or by) a mining company. My guess is that it's a way to re-use some of the detritus from the mining operation.

Conceptually, it's reflected mirror (moved electronically in real time) to reflect sunlight to a spot where it generates heat / steam during the day.

When it's generating more power than can be used by the mining operation I suspect a portion of the mirrors move to heat rocks or such instead. Then at night (when they still need power, they dump the re-collected steam/ water onto the heated stone and produce steam again. Just enough to power whatever operations they have going on at night.

Not sure what the "Sand Battery" article is really talking about. But, my first thoughts were that it was likely somewhat similar. Keep in mind that these types of "articles" are really akin to a press release by the company to drum up investor money.