New Solar Thermal Research Points At 10-Fold Increase In Energy Density
Originally published on Solar Love.
Researchers at Oregon State University are experimenting with ways to generate electricity using thermal solar materials. They are working with a process that changes strontium carbonate into strontium oxide and carbon dioxide. The strontium carbonate decomposes, but when the materials recompose they release stored heat.
“In these types of systems, energy efficiency is closely related to use of the highest temperatures possible. The molten salts now being used to store solar thermal energy can only work at about 600 degrees centigrade, and also require large containers and corrosive materials. The compound we’re studying can be used at up to 1,200 degrees, and might be twice as efficient as existing systems. This has the potential for a real breakthrough in energy storage,” explained Nick AuYeung, an assistant professor of chemical engineering in the OSU College of Engineering.
The materials that are being used are non-flammable and potentially cheaper than those currently used by CSP, though recent successes in using the new materials have occurred only in lab environments. If you are familiar with concentrating solar power, you know that it has been proven to work in real-world solar facilities. The costs of construction can be high, so this OSU research might be helpful in bringing them down.
Also, the solar thermal material currently used — molten salts — has some limitations. AuYeung said they typically can be heated to 600 degrees Centigrade, but the material he is using can be used at 1,200 C, which means it could be twice as efficient. Imagine being able to store about twice as much energy in the form of heat at a concentrating solar power plant. At that higher temperature, it might also be used to heat air and steam to turn turbines which generate electricity.
If you haven’t heard of concentrating solar power, you might have at least noticed some flurry of news stories about solar power killing birds. However, most of those stories were very sensational and grossly exaggerated the number that were killed.
Image Credit: Oregon State University
Reprinted with permission.
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I think they dont push molten salt to higher temperatures because it would involve making pipes and other components from more temperature resistant and more expensive materials.
Well, not exactly, but yes. Fluoride salts are stable up to 800°C. The limiting parameter is collector design, not material parameters. The reason they don’t approach this limit is because the added design complexity does not justify the added efficiency.
The author clearly did not understand the topic he wrote about. There are numerous issues such as this. And the blatant:
“AuYeung said they typically can be heated to 600 degrees Centigrade, but the material he is using can be used at 1,200 C, which means it could be twice as efficient.” – Double the temperature (In C, only really 66% more absolute energy) does not mean double the efficiency. It allows for some other clever design tricks such as multistage turbines which could Theoretically offer up to 2x improvements, but also increases real world losses… It’s not the double temperature that makes it more efficient as implied, it’s the changes in design that it might allow…
Strontium is far less common than calcium, a related alkaline earth element. Can Ca be used instead?
Above 1,000 deg C, you can think of a Brayton-cycle generator, aka a gas turbine running on hot air. It’s not that difficult to get to such temperatures at the focus of the heliostat field; the French solar furnace at Odeillo in the Pyrenees, built in the 1960s, easily gets over 3,000 deg C. You run out of materials that can stand up to the heat. The big problems are to design an efficient porous ceramic receiver, and a high-temperature storage scheme. Cutting out water/steam allows higher efficiencies and possibly lower costs. CSP isn’t dead.
Combined cycle Brayton/Rankine.
I am glad to see work is still being done in this arena, but batteries still seem to have so many inherent advantages in simplicity and low O&M costs compared to any type of thermal system.