Bronze Age technology makes renewable energy shift cheaper

A technology that dates back thousands of years could dramatically reduce the need for batteries and other renewable energy storage technologies, according to US researchers.

Firebricks are heat-absorbing bricks which emerged in the early Bronze Age, around 4000-3000 BCE. They were first used to line kilns, and have since been used in furnaces.

They are a cheaper and more efficient way to store heat for industrial processes like steel, cement and glass making, say the researchers.

The researchers have published a study in PNAS Nexus estimating that, if the world is running on 100% renewable energy by 2050, firebricks could reduce the global need for batteries by 14.5%, hydrogen by 31%, and underground heat storage by 27.3%.

“The difference between firebrick storage and battery storage is that the firebricks store heat rather than electricity and are one-tenth the cost of batteries,” says lead author Professor Mark Jacobson, an engineer at Stanford University, USA.

“The materials are much simpler too. They are basically just the components of dirt.”

Companies have recently started selling firebricks for industrial heat processes. They can be made to both insulate and absorb heat, with their compositions tweaked to do more of one or the other. The heat gets released by letting air flow through channels in between stacked firebricks.

Cement, steel, and glass making all need temperatures of more than 1,000°C to work. At the moment, this heat is mostly achieved by burning fossil fuels. According to the researchers, these processes are responsible for about 17% of annual CO₂ emissions worldwide.

While this heat can be produced with renewable energy like wind and solar, factories need consistent sources of energy to run and so need appropriate storage to account for the variable nature of wind and solar.

The researchers propose that firebricks, heated by renewables, could be used instead of batteries and hydrogen as storage.

“By storing energy in the form closest to its end use, you reduce inefficiencies in energy conversion,” says co-author Dr Daniel Sambor, a postdoctoral scholar at Stanford.

“It’s often said in our field that ‘if you want hot showers, store hot water, and if you want cold drinks, store ice’; so this study can be summarised as ‘if you need heat for industry, store it in firebricks.’”

The researchers analysed industrial processes in 149 countries, which are collectively responsible for 99.75% of anthropogenic carbon dioxide emissions.

They used modelling to examine 2 scenarios for how these countries’ energy systems would change if they were running on 100% renewable power by 2050. In one scenario, firebricks were used for 90% of industrial heat, while in the other, they weren’t used at all.

“We found that firebricks enable a faster and lower-cost transition to renewables, and that helps everyone in terms of health, climate, jobs, and energy security,” says Jacobson.

The firebrick scenario was US$1.27 trillion cheaper than the no-firebrick scenario in terms of capital cost, and dramatically reduced the need for other grid storage technologies.

“What excites me is that the impact is very large, whereas a lot of technologies that I’ve looked at, they have marginal impacts,” says Jacobson.

“Here I can see a substantial benefit at low cost from multiple angles, from helping to reduce air pollution mortality to making it easier to transition the world to clean renewables.”