Innovative sand battery can heat entire town for a week

[Endymio]

As you even noted, water is 3 times more efficient than sand at storing heat.

Untrue, and not what he stated. Most solid materials are far more efficient at storing heat long-term than water. And while water wins on energy density at low temperatures, as mbk34 points out, it loses at ultrahigh temps.

BTW, the average melting point of copper cables is 1085C so how do you propose keeping the transmission cables connected to any heating elements from melting when the sand reaches your magic 1830C?

Oops! It's 1830F, not 1830C. And instead of arguing an obviously losing position, why not learn what's actually being proposed here?

And the cost to construct solar farms and windmills ....

Sigh. The solar farms and windmills are already built. That's the entire point. This battery is intended to capture some of the energy these are currently wasting.

 

[mbk34]

I don't care what country you're from. As you even noted, water is 3 times more efficient than sand at storing heat. BTW, the average melting point of copper cables is 1085C so how do you propose keeping the transmission cables connected to any heating elements from melting when the sand reaches your magic 1830C? And the cost to construct solar farms and windmills and connecting cables and heating elements to underground sand pits far outstrips the cost of geothermal wells. The costs to construct windmill farms and solar farms to heat such pits are more expensive by a factor of 10. You're also not factoring in the maintenance costs of windmills or solar farms. Again, if rocks and sand made sense for thermal storage and heating towns, it would already be in use the world over but it isn't for very good reasons.

I was simply saying that in my country we've been using electricity to store thermal energy for houses since the 1970's. Water is 3 times more efficient up to 100C but that's a low temp for storage unless you're just making a cup of tea. Why does it matter what temp copper melts? My kettle boils to 100C but the cables leading to it are cold. Electric aluminium smelters go to 800C without any issue. They just don't use copper as the heating element.

The solar farms and wind farms are already built. The problem is what to with the extra electricity that gets generated at times when no-one wants it. That's why we need large scale batteries to store the energy. The largest one I'm aware of is in Switzerland storing 20GWh but Australia is currently building a 120GWh plant. To put that in perspective that's 60 million times larger than Tesla's largest car battery. These sand batteries are just a different way to store energy.

If geothermal wells work out cheaper in your vicinity then great, go with them. That still leaves the issue with what to do with the electricity produced by wind farms etc when no-one wants it.

 

[ferrellsl]

People have been using heated stone and rock to store heat for even longer; it's even more inexpensive -- no water tanks required.

You don't seem to realize that different applications require different solutions. For thermal storage at lower temperatures, water is by far the most energy-dense material. But water loses heat very quickly, which isn't a big problem for, say, adding thermal mass to a building to mediate daily temperature swings. But it's an enormous issue for an installation intending to store heat for several months.


Oops! This same company already installed a working sand battery two years ago. This is just a larger version of the same technology.


Sigh, Finland is not Iceland. Geothermal is not widely available throughout the country, and is restricted to a few anomalous sites like Varisto. This research paper will explain why:

"The use of geothermal energy in Finland is restricted ...This is due to geological conditions as Finland is a part of the Fennoscandian (or Baltic) Shield ... Topography is subdued and does not easily produce advective distribution of geothermal heat... rock porosity and its water content are low. This practically excludes geothermal systems utilizing hot wet rock. The lithosphere is very thick in Finland (150-200 km), and heat flow is mostly below continental average (< 65 mW m-2). Measured heat flow density values in the uppermost 1 km of bedrock range from very low (<15 mW m-2) values to 69 mWm-2,... in order to reach 100ºC, depths from 6 to8 km are required. These numbers suggest that Finland is not a good candidate for either wet or dry hot rock systems..."

https://www.geothermal-energy.org/pdf/IGAstandard/WGC/2000/R0778.PDF

No, no they haven't heated homes for centuries with rocks. Using a fireplace to heat a brick or stones to put in your bed on a cold night isn't the same as heating sand to 1000C+ to heat a city. And even if they COULD heat this sand to target the temp of 1000C+ mentioned in the article, they make no mention of how they're going to extract that heat and transmit it to homes that need it. So said "battery" is essentially useless and would require as as-yet undeveloped and expensive technology for heat transmission. This entire article reads like a bad Star Trek episode with pseudo-scientific terms tossed about and no real facts. I don't care if it's Finland, Iceland or Candy Land. Water tanks aren't required for geothermal wells either and the water is typically under high pressure in these systems so boiling isn't a problem. A much better use of excess electrical capacity would be to store that electricity in large Tesla batteries on the surface due to the efficiency and being able to tie said "real batteries" into an already existing electrical infrastructure, not heating the ground and then trying to extract and distribute that heat again to homes spread out over a large are. That is just ludicrous, as is the article.

@Endymio And I suppose you just make up facts for convenience. But here are several sources that show the true melting point of copper and it is in fact 1084C, not the 1830C you're claiming. I didn't quote Fahrenheit temps at any time for the melting point of copper, you did:

https://en.wikipedia.org/wiki/Copper

https://www.onlinemetals.com/en/melting-points

Melting Points of Metals - Muggy Weld

This chart shows the various melting points of metals, for use in welding, soldering, and brazing applications. Complete guide for informational purposes.

www.muggyweld.com

Melting Points of Metals | Values in Celsius, Fahrenheit & Kelvin | Fractory

Refer to this chart for the melting points of various metals and alloys. For example, copper melts at 1084°C and steel has a melting point that ranges from 1371°C to 1593°C

fractory.com

So you're either misinformed, a fool, a liar or possibly all 3. Or you have a reading comprehension problem. I'll go with the latter. Nor did I claim they'd use copper heating elements as I know those would melt before the sand reaches the target temp of 1000C+ that the developers want to reach with this ludicrous "battery". Whatever element they use, the wiring leading to it will melt and certainly a copper heating element would melt as they wouldn't be able to maintain an 84C margin of error.

 

[mbk34]

No, no they haven't heated homes for centuries with rocks. Using fire to heat a brick or stone to put in your bed on a cold night isn't the same as heating sand to 1800C to heat a city. And even if they COULD heat this sand to 1800C, they make no mention of how they're going to extract that heat and transmit it to homes that need it. So said "battery" is essentially useless and would require as as-yet undeveloped and expensive technology for heat transmission. This entire article reads like a bad Star Trek episode with pseudo-scientific terms tossed about and no real facts. I don't care if it's Finland, Iceland or Candy Land. Water tanks aren't required for geothermal wells either and the water is typically under high pressure in these systems so boiling isn't a problem. A much better use of excess electrical capacity would be to store that electricity in large Tesla batteries on the surface due to the efficiency and being able to tie said "real batteries" into an already existing electrical infrastructure, not heating the ground and then trying to extract and distribute that heat again to homes spread out over a large are. That is just ludicrous, as is the article.

@Endymio And I suppose you just make up facts for convenience. But here are several sources that show the true melting point of copper and it is in fact 1084C, not the 1830C you're claiming: https://en.wikipedia.org/wiki/Copper

https://www.onlinemetals.com/en/melting-points

Melting Points of Metals - Muggy Weld

This chart shows the various melting points of metals, for use in welding, soldering, and brazing applications. Complete guide for informational purposes.

www.muggyweld.com

Melting Points of Metals | Values in Celsius, Fahrenheit & Kelvin | Fractory

Refer to this chart for the melting points of various metals and alloys. For example, copper melts at 1084°C and steel has a melting point that ranges from 1371°C to 1593°C

fractory.com

So you're either misinformed, a fool or a liar or possibly all 3. Or you have a reading comprehension problem. I didn't quote Fahrenheit temps at any time, you did.

They have been storing heat in stones since Roman times so that's about 2000 years. You can heat anything to any temperature if you apply enough heat. Obviously it will turn to liquid or gas at some point (even rocks). You wouldn't heat ever single building in a town, unless it was a very small town, but you can provide heat to apartment blocks, municipal buildings, schools and office blocks. You'd normally use insulated pipes carrying some form of heat transfer fluid (oil, pressurised water, air etc). In Iceland they use geothermal energy to heat 90% of their homes and I assume the same method of transferring heat would be used in this case.

Tesla batteries are just one way of storing electricity but it's an expensive option and the batteries do wear out over many discharge cycles. Pumped hydro is currently the best way to store massive amounts of electricity but you need the right geography for that. There's loads of other methods from hydrogen storage to liquid air to massive spinning weights. But in this case, they're heating sand.

 

[Endymio]

here are several sources that show the true melting point of copper and it is in fact 1084C, not the 1830C you're claiming.

Reading comprehension for the win. The OP stated the sand was heated to 1830F. You misread that as Celsius, not Fahrenheit, and have resisted all attempts to correct you since.

even if they COULD heat this sand to target the temp of 1000C+ mentioned in the article, they make no mention of how they're going to extract that heat and transmit it to homes that need it.

Wrong again. Their proposal is highly detailed. Why not read it?

Nor did I claim they'd use copper heating elements as I know those would melt

If you know they wouldn't use copper, then why on earth did you claim this "couldn't work" because the copper would melt? Why not admit your error, instead of further compounding it?