Developed as early as 1600 BC in what is modern-day Turkey, firebricks – which are essentially bricks made of clay capable of withstanding high temperatures – are being eyed by scientists for thermal heat storage. Led by principal research scientist Charles Forsberg, researchers at Massachusetts Institute of Technology (MIT) recently published a paper illustrating how what they are calling the “Firebrick Resistance-Heated Energy System” (abbreviated as FIRES), can aid and encourage the transition from fossil fuels to renewable energy.
MIT graduate students Daniel Stack, Daniel Curtis, Geoffrey Haratyk, and Nestor Sepulvedan also contributed to the paper, which was published in Electricity Journal late last month. The idea is to exploit the unused excess electricity generated (from wind farms when strong winds are blowing at night for example) by converting electricity into heat via electric resistance heaters and heating up insulated firebricks, which can store heat for long periods of time. Later, the thermal energy stored can be used directly in industries or converted back to electricity through generators.
FIRES has the potential to be especially revolutionary for industry, where demand for industrial heat outweighs that for electricity, according to Forsberg. The scientist adds that there’s a constant demand for industrial heat, providing an “almost limitless” market for the heat provided by firebrick technology. The oversupply of renewable energy during non-peak times would also allow renewable energy providers to optimize their production, effectively raising electricity prices and enabling suppliers to operate at full capacity, even during down times. Earlier this year, wholesale electricity prices decreased to near zero in cities across Europe and the U.S. – evidence of the economic limitations of using low-carbon electricity sources without an efficient model for energy storage.
For a heat storage capacity of 1,500 megawatt-hour, the required firebrick volume is approximately 3,000 cubic meters (105,944 cubic foot), providing 142 megawatt-electric for six hours, which is similar to the firebrick heat storage system associated with the Adele ACAS system (pictured above).
With utility gas turbine technology coming into the market, the efficiency of converting electricity to heat is very close to 100 percent, and the roundtrip FIRES efficiency (electricity-to-heat-to-electricity) can be above 70 percent. The FIRES system would effectively compete with the less-than-perfect battery storage system that the renewable energy sector currently relies on. “However, unlike other storage systems, if the auxiliary combustion chambers are maintained, there is assured peak generating capacity burning fossil fuels, biofuels, or ultimately hydrogen,” the research reads.
The research finds that FIRES converts low-cost electricity into high-temperature hot air and stored heat to replace fossil fuels in industry. While the technology itself isn’t new, recent changes in the electricity market can create incentive to deploy FIRES. The estimated capital costs of firebrick technology to provide heat for industry ranges between $5 and $10 per kilowatt-hour, which is less than any other technology currently available.
“The transition from a fossil-fuel-based electricity system to a low-carbon electricity system is a transition from low-capital-cost, high-operating-cost electricity generators to high-capital-cost, low-operating-cost nuclear, wind, and solar systems with low marginal generating costs,” reads the paper’s conclusion.