A global transition to 100% renewable energy would be cheaper and simpler if firebricks, a form of thermal energy storage dating back to the Bronze Age, were used to generate most of the heat needed for industrial processes, according to new research from Stanford University.
Today’s industries require high temperatures for production, largely achieved through the continuous burning of coal, oil, fossil gas or biomass. With much of the world focused on reducing emissions by switching from fossil fuels to renewable sources such as wind, solar and hydro, the question is how to provide continuous heat on demand to industries in a 100% renewable world.
Researchers from Stanford University's Department of Civil and Environmental Engineering suggested in a recently published study that an old solution, firebricks, could be a solution to this problem.
“By storing energy in a form closest to its final use, you reduce inefficiencies in energy conversion,” says Daniel Sambor, a postdoctoral researcher in civil and environmental engineering and co-author of the study. “In our field, it’s often said, ‘if you want a hot shower, store hot water, and if you want a cold drink, store ice,’ so this work boils down to, ‘if you need heat for industry, store it in firebricks.’”
As energy from wind and sun fluctuates, it is important to have sources that can replace combustion fuels to store electricity or heat. Refractory bricks, which can withstand high temperatures without damage, have been used to line furnaces, stoves, fireplaces and ovens for thousands of years—probably since the early Bronze Age.
Similar to firebricks, firebricks can store or insulate heat, depending on the material they are made from. Firebricks used to store heat should have a high specific heat (the amount of heat that 1 g of a substance must absorb or lose to change its temperature by 1 °C (1.8 °F)) and a high melting point. Ideal low-cost firebricks with these properties include alumina and magnesia, or low-quality graphite. Insulating firebricks must withstand high temperatures but have low thermal conductivity to resist heat flow and slowly absorb heat from their surroundings. Silica has a low thermal conductivity, so it is regularly used in these types of firebricks.
Heat storage firebricks are another type of firebricks that provide more insulation and are then surrounded by steel, such as a thick steel container, to further reduce heat loss. Process heat can be extracted on demand from the firebricks by generating low to high temperature air by passing ambient or recycled air through channels in the bricks, or directly from the emission of infrared radiation from the red-hot bricks. The use of firebricks eliminates the need for battery storage or green hydrogen storage of renewable electricity, as electricity storage is replaced by firebricks storage.
The aim of the current study was to examine the impact of using firebricks to store most of the industrial process heat in 149 countries that have transitioned to 100% clean and renewable energy in a hypothetical future in 2050. The selected 149 countries are responsible for producing 99.75% of fossil fuel carbon dioxide (CO2).2) emissions globally. The researchers used computer models to compare costs, land requirements, health impacts, and emissions for two scenarios: one in which firebricks provide 90% of the industrial process heat, and a second scenario in which firebricks are not used.
“Ours is the first study to look at a large-scale transition to renewable energy with firebricks as part of the solution,” said Mark Jacobson, a professor of civil and environmental engineering at Stanford's Doerr School of Sustainability and the study's lead and corresponding author. “We found that firebricks enable a faster and more cost-effective transition to renewable energy, and that helps everyone in terms of health, climate, jobs and energy security.”
Across 149 countries, compared to a scenario where firebricks were not used, it was found that using firebricks significantly reduced capital costs by $1.27 trillion in 2050. Firebricks also reduced the need for energy storage capacity from batteries by about 14.5%, annual hydrogen production for grid electricity by about 27.3%, land needs by about 0.4%, and overall annual energy costs by about 1.8%. For the ‘no firebricks’ scenario, countries were assumed to obtain heat for industrial processes from electric furnaces, heaters, boilers, and heat pumps, and batteries were assumed to be used to store electricity for these technologies.
“The difference between firebrick storage and battery storage is that firebrick stores heat instead of electricity and is one-tenth the cost of batteries,” Jacobson said. “The materials are also much simpler. They're basically just components of the soil.”
An important question arises from the study: What about gases and particles from industrial combustion and CO2?2 emissions from industrial process chemical reactions – primarily from steel and cement production – that firebricks do not address? The researchers suggest that electric arc furnaces, resistance furnaces and boilers, induction furnaces, electron beam heaters, and dielectric heaters may cover industrial combustion that firebricks do not. CO2 emissions from steelmaking can be addressed by using green hydrogen instead of coke or coal to reduce iron ore to pure iron. And CO2 They suggest that emissions from cement production could be eliminated by using basalt (carbon-free calcium silicate rock) instead of limestone during the production of ordinary Portland cement (OPC) and by using geopolymer cement instead of OPC. By combining these techniques with firebricks, the researchers say, “it is possible to eliminate most, or even all, of the air pollution.”2 “Energy from industrial production without the need for carbon capture.”
High-temperature heat-storing firebricks are widely available commercially, and the researchers hope that using them to help transition to renewable energy will make the process cheap and simple, both of which will encourage people to support their new solution.
“If we propose an expensive and difficult way to transition to renewable electricity, we’re going to have very few takers,” Jacobson said. “But if it saves money compared to a previous method, it will be implemented faster. What excites me is that the impact is so big, whereas many of the technologies I’ve looked at have marginal impacts. I can see a significant benefit here at a low cost, from helping to reduce air pollution mortality to helping the world transition to clean renewable energy.”
The study was published in the journal PNAS Link.
Source: Stanford