Hot sand as an energy storage/transfer medium.

[Shannow]

This is a really really clever idea.

http://www.cleantechconcepts.com/2016/01...energy-storage/

Desert sand, stored in an "hourglass" type arrangement, and dropped through a "venturi" at the focal point of a solar collector, heating it from 250C to 800C (or more).

Hot sand is stored, and used to shift heat into a process (could be any), and cooled (250C) sand returned to the top of the hourglass.

No pressure, no nasty molten salts, no environmental contamination if you leak some, and hot sand won't have convection currents to accelerate heat loss.

 

[OneEyeJack]

On the way to Yuma from San Diego there's a lot of sand as far as the eye can see once you're in it. It'w where they filmed an episode of Star Wars.

Just think, some day in the future that could be an economic center of prosperity because it would have unlimited cheap energy if they can work this idea into something practical.

Glamis sand dunes

 

[Kira]

There's a axiom in energy collection which has to do with heat rising. I believe it to be plenary dynamic such that anything going against it is flawed.

Example: Various hot oil 'trickle down collectors' spilled oil down a dark metal sheet thus heating it. However the heat was bathed out of the oil is something I forget but the point is that this style collector was dismissed as a high school project due to its reliance on the layer of mechanics needed to extract the heat.

Good for a camping trip water heater in a blazing hot locale but not for operations of scale.

I wonder if this system (involving conveyer belts and shifting heat extraction coils into sand pits) is similarly limited. Kira

 

[RedOakRanch]

Sand is listed as a carcinogen in CA. So we can't do it... Just poking fun of my state, I sell sand and it has to have the warning labels just like cigarettes!

 

[Rick in PA]

Originally Posted By: RedOakRanch
Sand is listed as a carcinogen in CA. So we can't do it... Just poking fun of my state, I sell sand and it has to have the warning labels just like cigarettes!


What's the carcinogen? Asbestos?

 

[ironman_gq]

Originally Posted By: Rick in PA
Originally Posted By: RedOakRanch
Sand is listed as a carcinogen in CA. So we can't do it... Just poking fun of my state, I sell sand and it has to have the warning labels just like cigarettes!


What's the carcinogen? Asbestos?


More than likely silica dust, they're worried about silicosis which is usually something you see in the refractory and concrete industries but can happen anywhere your exposed to super fine silica dust for long periods of time.

 

[PandaBear]

It would take a lot of energy moving the sand up the hourglass too.

I'd imagine having 2 tanks of refrigerants, 1 above ground in the desert and 1 under, with turbine generator in the middle, would be quite efficient in continuous, 24 hour power generation.

But why would you want to store power for night time use? There's cheap idle capacity and the peak load is when the sun is shining (air conditioning).

 

[CT8]

I am still waiting for the hydrogen revolution to happen.

 

[A_Harman]

From the article:

"To discharge the system, a heat exchanger is immersed in the heated moving sand, producing superheated steam that runs the turbine. "

The guy that really makes out on this system is the one that supplies the heat exchangers and the sand pumps. They're going to need a lot of them. What marvelously wear resistant material are they using? I don't see copper or aluminum lasting very long as heat exchangers with sand flowing through them. On the other side, ceramic or tungsten carbide would have great wear resistance, but have low thermal conductivity, so would not be great for heat exchange.

And who wants to tackle the challenge of coming up with a pump that will last a useful amount of time while pumping sand at 1000C? I think that even ceramics would wear out quickly.

 

[Shannow]

A Harmann,
all good questions...and I don't think that they are insurmountable.

I'll drop back to my familiar territory.

Power station boilers survive with highly abrasive flyash running through them at very very high velocities...Erosion rates increase with gas speed to the power of 3.7...the sliding velocities will be much, much slower, albeit with a much denser medium.

Circulating fluidised bed boilers are now quite common, with a "boiling" bed of sand and fuel in direct contact with the tubes.

That end (1000F) the tube materials are usually 304L, with T22 in the lower temp areas, and 105 in the areas that they are filled with water. (Funnily, the erosion performance of the stainless versus chrom moly is different. The CrMo tends to get abraded at the 1:30 and 10:30 positions (gas flow at 12:00), while the stainless gets eroded at the 12:00 position).

Yeah, we ceramic coat some parts that display abnormal erosion due to localised effects.

Technology for moving and lifting the sand would most likely be something like a Magaldi Ash Hopper/Cooler.



We put a couple of these on the boilers at Wallerawang, and they are very good...I've heard rumours that they are front runners in carrying hot sand up hill.

edit...here they are

http://www.bloomberg.com/news/articles/2...-produce-energy