Ancient Technology for a Modern Energy Storage Solution
The switch to renewable energy will in the future rely on the development of effective energy storage systems to store surplus power for use when the sun doesn’t shine or the wind doesn’t blow.
Scientists may have been developing ever more efficient batteries and cutting edge technologies to try and meet the challenge, but a technology that has been around for 3,000 years may offer one solution.
Firebricks, designed to withstand high heat, have been used since the era of the Hittites and now researchers from MIT think sometimes the old ways are the best ways. Under their proposal firebricks will play a key role in helping the world switch away from fossil fuels and rely instead on carbon-free energy sources.
According to their plan, firebricks will act as a medium in which to store heat for later use, either directly in industrial processes, or to generate electricity.
Excess power produced at peak generation will be fed into electric resistance heaters, that in turn will heat up a mass of firebricks, which can retain heat for a long time when enclosed in an insulated casing.
Researchers cheerfully admit the technology 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. Due to the low operating cost of solar and wind, when there is an excess of supply spot prices plunge, at times to almost zero. This can lead to generation being shut down for periods. By storing the energy, price fluctuations can be levelled out, energy supply equalised, and turbines can keep turning.
Technologically, the system “could have been developed in the 1920s, but there was no market for it then,” said Charles Forsberg, a research scientist in MIT’s Department of Nuclear Science and Engineering and lead author of a research paper describing the plan.
He envisages the main use of the technology being in industry, where heat is the more desired form of energy, rather than electricity.
In the USA for example, the demand for industrial heat is actually larger than the total demand for electricity. And unlike the demand for electricity, which varies greatly and often unpredictably, the demand for industrial heat is constant and can make use of an extra heat source whenever it’s available, providing an almost limitless market for the heat provided by this firebrick-based system.
At present, the options for storing excess electricity are essentially limited to batteries or pumped hydroelectric systems. By contrast, the low-tech firebrick thermal storage system would cost anywhere from one-tenth to one-fortieth as much as either of those options, Forsberg said.
Firebrick itself is just a variant of ordinary bricks, made from clays that are capable of withstanding much higher temperatures, ranging up to 1,600 degrees Celsius or more.
The advantage of using the heat stored in the firebricks directly is mainly one of efficiency. Turning that heat back into electricity is a bigger technical challenge, which would need to be further addressed. Theoretically an electricity-heat-electricity cycle would be about 70% efficient, while electricity-heat-industrial process approaches 100%.