MIT readapts ancient firebrick technology to boost profitability of renewables

MIT
© MIT / Power plant with firebrick-based thermal storage system

One of the barriers to the large-scale adoption of clean energy is what to do with the excess electricity produced when demand is low. There are storage options like batteries or pumped hydroelectric systems, but it can be costly, and it's a problem that makes renewables less profitable compared to fossil fuels. Now, researchers at MIT say that the ancient technology of firebricks could be a low-tech, low-cost way to store carbon-free energy, making a widespread switch over to renewables much more economically feasible.

According to MIT News, firebricks -- which are essentially made of a type of clay that can withstand high temperatures -- date back over 3,000 years to the time of the Hittites. The researchers have adapted the firebrick concept into a system they call Firebrick Resistance-heated Energy Storage, or FIRES, which they detailed in a paper published in The Electricity Journal.

Ted HoodTed Hood/Public Domain

The underlying idea is to convert this excess electricity into heat that is absorbed and stored into firebricks for later use. For instance, a FIRES system could use this excess output to power electric resistance heaters that warm up a mass of firebricks. These heated firebricks can then be covered with an insulated casing, so the energy can be used later for industrial applications or heating, or even converted back to electricity. All this could potentially change the landscape for adopting renewables, says MIT:

The technology itself is old, but its potential usefulness is a new phenomenon, brought about by the rapid rise of intermittent renewable energy sources, and the peculiarities of the way electricity prices are set. [..] FIRES would in effect raise the minimum price of electricity on the utilities market, which currently can plunge to almost zero at times of high production, such as the middle of a sunny day when solar plant outputs are at their peak. [..]

But by diverting much of that excess output into thermal storage by heating a large mass of firebrick, then selling that heat directly or using it to drive turbines and produce power later when it’s needed, FIRES could essentially set a lower limit on the market price for electricity, which would likely be about the price of natural gas. That, in turn, could help to make more carbon-free power sources, such as solar, wind, and nuclear, more profitable and thus encourage their expansion.

One of the big draws is that firebricks are about one-tenth to one-fortieth cheaper than conventional options for storing excess electricity, such as batteries or pumped hydroelectric systems. Modern firebricks, which can endure temperatures of up to 1,600 degrees Celsius (2,912 Fahrenheit) or more, can be made with varying properties by altering their chemical compositions or the way they are stacked. For instance, silicon carbide, which is already produced in large amounts worldwide for things like sandpaper, could be one potential material that's high in thermal conductivity to be used for firebricks. Bricks that are made to hold more heat could be insulated with bricks that are less thermally conductive.

Right now, the researchers are working to refine the system, and plan to build a real-world prototype to see if it'll work on a larger scale. Innovative ideas like this have their roots in ancient, time-tested techniques, but could be poised to change the game for renewables in the future. To find out more, see MIT News and read the paper here.

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