Bronze Age Technology Could Help Drive Clean Energy Transition

A technology with roots dating back to the Bronze Age could prove to be a quick and inexpensive solution to help achieve the UN’s climate goal of achieving net-zero emissions by 2050, according to new research from Stanford. Nexus PNAS.

The technology involves assembling heat-absorbing bricks into an insulated container where they can store heat generated by solar or wind power for later use at the temperatures required by industrial processes. The heat can then be released when needed by passing air through channels in the stacks of “firebricks,” allowing cement, steel, glass and paper factories to operate on renewable energy even when wind and sun are unavailable.

These systems, which several companies have recently begun commercializing for industrial heat storage, are a form of thermal energy storage. The bricks are made of the same materials as the insulating bricks that lined primitive iron kilns and furnaces thousands of years ago. To optimize heat storage rather than insulation, the materials are combined in varying amounts.

Batteries can store electricity from renewable sources and provide electricity to generate heat on demand. “The difference between firebrick storage and battery storage is that firebricks store heat, not electricity, and they’re 10 times cheaper than batteries,” said study lead author Mark Z. Jacobson, a professor of civil and environmental engineering at the Stanford Doerr School of Sustainability and School of Engineering. “The materials are also much simpler. They’re basically just dirt.”

High heat storage

Many industries require high temperatures for production. Temperatures in factories must reach at least 1,300 degrees Celsius (nearly 2,400 degrees Fahrenheit) to make cement, and 1,000 degrees Celsius (about 1,800 degrees Fahrenheit) or more for glass, iron, and steel production. About 17% of all carbon dioxide emissions worldwide currently come from burning fossil fuels to produce heat for industrial processes, according to calculations by Jacobson and co-author Daniel Sambor. Generating industrial heat from renewable sources could nearly eliminate those emissions.

“By storing energy in the form closest to its end use, you reduce the inefficiency of energy conversion,” said Sambor, a postdoctoral fellow in civil and environmental engineering. “In our field, we often say, ‘If you want a hot shower, store hot water, and if you want a cold drink, store ice,’ so this study can be summed up as, ‘If you need industrial heat, store it in firebricks.’”

Significant savings

The researchers set out to study the impact of using firebricks to store most of the process heat in 149 countries in a hypothetical future in which every country switched to wind, geothermal, hydroelectric and solar power for all energy purposes. The 149 countries account for 99.75% of global carbon dioxide emissions from fossil fuels. “Our study is the first to examine the transition to renewable energy on a large scale with firebricks as part of the solution,” Jacobson said. “We found that firebricks enable a faster and cheaper transition to renewable energy, which helps everyone in terms of health, climate, jobs and energy security.”

The team used computer models to compare costs, land requirements, health impacts and emissions under two scenarios of a hypothetical future in which 149 countries in 2050 use renewables for all energy purposes. In one scenario, firebricks provide 90% of industrial process heat. In the other, there is no adoption of firebricks or other forms of thermal energy storage in industrial processes. In the scenario without firebricks, the researchers assumed that heat for industrial processes would come from electric furnaces, heaters, boilers and heat pumps, and batteries would be used to store electricity for these technologies.

The researchers found that the firebrick scenario could reduce capital costs by $1.27 trillion across all 149 countries compared with a scenario without firebrick storage, while also reducing grid demand and the need for battery storage.

Clean energy, cleaner air

Solutions that accelerate the transition to clean energy are also linked to human health. Previous studies have shown that air pollution from burning fossil fuels causes millions of premature deaths each year. “Every bit of fuel we replace with electricity reduces air pollution,” Jacobson said. “And because there’s a finite amount of money to make a rapid transition, the lower the cost to the entire system, the faster we can implement it.”

Jacobson has spent his career understanding air pollution and climate problems and developing energy plans for countries, states and cities to address them. But his focus on firebricks is relatively new, inspired by a desire to identify effective solutions that could be adopted quickly.

“Imagine if we were to propose an expensive, difficult way to switch to renewable electricity—we would have very few takers. But if it saves money over the previous method, it will be implemented more quickly,” he said. “What excites me is that the impact is very large, whereas many of the technologies I’ve studied have marginal impact. Here, I see a significant benefit at low cost on many fronts, from helping reduce air pollution mortality to facilitating the world’s transition to clean renewable energy.”