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I'm confused... this is basically the same as molten salt, just with sand instead of salt. Molten salt has been around for a very long time and is how solar th

I'm confused... this is basically the same as molten salt, just with sand instead of salt. Molten salt has been around for a very long time and is how solar thermal power plants store energy and continue to generate power after dark. Is there an innovation here that I'm missing?

zdragnar 4y ago
Molten salt is very corrosive, and this only heats to 600C, and sodium chloride doesn't melt until 800C. This is a cheaper, lower maintenance option.
- scythe 4y ago
  The molten salt used for energy storage is a sodium nitrate – potassium nitrate eutectic with an operating temperature range of 200-550 C and a much lower corrosion behavior than chloride salts.
  - zdragnar 4y ago
    ah, fair enough. The design in the photo is much more vertical than horizontal- maybe they're designing for space constraints? I would imagine 500*C molten salt would be significantly more efficient than sand, so the only charitable thing I can come up with is they're simply putting the cheapest materials they can (discard sand, free electricity) to good use.
zardo 4y ago
Different application and price point. This doesn't operate at a high enough temperature to make generating electricity back from it feasible, so it's only good for heating. But, you can build big and cheap for seasonal scale storage, and it can be underground with a secondary land use on the surface.
michael1999 4y ago
Non-electic. Direct heat storage for district heating with zero high-tech involved. Resistive heaters, air ducts, a silo, sand, and some fans -- all established enough for utility use.
marcosdumay 4y ago
I guess not needing an insulated tank (that can crack if the power runs out) makes things much cheaper. And the higher the operational temperature, the less difference it makes if you use a complex phase change design or a simple bunch of cheap sand. But I doubt 600°C is enough to make sand win.
leetnewb 4y ago
Interestingly, next generation solar thermal storage might be sand-like as well: https://www.azocleantech.com/article.aspx?ArticleID=1057 https://www.azocleantech.com/article.aspx?ArticleID=1057

zdragnar 4y ago

Molten salt is very corrosive, and this only heats to 600C, and sodium chloride doesn't melt until 800C. This is a cheaper, lower maintenance option.

scythe 4y ago
The molten salt used for energy storage is a sodium nitrate – potassium nitrate eutectic with an operating temperature range of 200-550 C and a much lower corrosion behavior than chloride salts.
- zdragnar 4y ago
  ah, fair enough. The design in the photo is much more vertical than horizontal- maybe they're designing for space constraints? I would imagine 500*C molten salt would be significantly more efficient than sand, so the only charitable thing I can come up with is they're simply putting the cheapest materials they can (discard sand, free electricity) to good use.

zardo 4y ago

Different application and price point. This doesn't operate at a high enough temperature to make generating electricity back from it feasible, so it's only good for heating. But, you can build big and cheap for seasonal scale storage, and it can be underground with a secondary land use on the surface.

michael1999 4y ago

Non-electic. Direct heat storage for district heating with zero high-tech involved. Resistive heaters, air ducts, a silo, sand, and some fans -- all established enough for utility use.

marcosdumay 4y ago

I guess not needing an insulated tank (that can crack if the power runs out) makes things much cheaper. And the higher the operational temperature, the less difference it makes if you use a complex phase change design or a simple bunch of cheap sand. But I doubt 600°C is enough to make sand win.

leetnewb 4y ago

Interestingly, next generation solar thermal storage might be sand-like as well: https://www.azocleantech.com/article.aspx?ArticleID=1057 https://www.azocleantech.com/article.aspx?ArticleID=1057