ANCIENT ROME–INSPIRED CEMENT BATTERY COULD TRANSFORM ENERGY STORAGE?

A technology inspired by techniques from Ancient Rome is being adapted to address one of today’s biggest challenges: energy storage. Researchers are exploring the properties of Roman concrete to develop a “thermal battery” capable of storing energy in the form of heat a promising alternative to fossil fuels such as natural gas.

The proposal is highly relevant. Approximately 30% of global energy consumption is used to generate heat, whether for industrial processes or for heating buildings and water.

The system is based on a well-known chemical reaction. When calcium oxide (quicklime) is mixed with water, it forms calcium hydroxide, releasing a significant amount of heat. The key advantage is that this reaction is reversible. By heating the material, the water can be removed, returning it to its original state and allowing the cycle to be repeated multiple times.

In practice, this turns the material into a rechargeable thermal battery.

Although the concept has existed since the 1970s, it is only now becoming viable due to falling renewable energy costs and advances in materials engineering.

Moving toward commercialization

One of the companies working to bring this innovation to market is the U.S.-based startup Cache Energy. The company has developed a system using small cement granules, roughly the size of corn kernels.

These granules are treated with a binding agent to maintain structural integrity during repeated charge and discharge cycles. When heated with electricity — ideally from renewable sources — they store energy. When later exposed to water, they release heat, reaching temperatures of up to approximately 540°C.

The system operates inside a compact reactor capable of producing around 100 kilowatts of thermal energy, with larger versions reaching megawatt scale. The granules can also be stored in silos, simplifying logistics and reducing infrastructure complexity.

Industrial and residential potential

Initially, the technology is focused on industrial applications, particularly processes that require continuous heat. However, there are plans to adapt it for residential use.

In this context, thermal batteries could be integrated with heating systems, storing energy when electricity prices are low — such as during periods of high solar or wind generation — and releasing heat later, reducing reliance on gas.

Real-world testing is already underway. A Whirlpool factory in the United States reported performance above expectations after evaluating the system.

The U.S. Department of Defense is also studying the technology for heating facilities during emergencies or grid failures. Meanwhile, universities and companies in Europe and Asia are showing interest, particularly due to volatile natural gas prices.

At the University of Minnesota Morris, researchers are exploring the possibility of heating an entire campus using locally generated wind energy combined with this system.

Technology was inspired by Ancient Rome (Image: Andrii Marushchynets / Shutterstock.com)

Challenges and competition

Despite its potential, the technology faces challenges. One of the main issues is identifying the optimal material composition to ensure efficiency and durability over multiple cycles.

In addition, it competes with other thermal storage solutions that use different materials and approaches. It remains unclear which model will dominate in specific applications.

However, the concept is particularly attractive in regions with high renewable energy production. In some cases, electricity supply exceeds demand, driving prices extremely low or even negative. Thermal storage systems like cement batteries can capture this excess and convert it into usable heat later.

Experts believe that combining renewable generation with thermal storage technologies could pave the way for greater energy independence at both local and regional levels.

Source: Vitoria Lopes Gomez - Adapted from The Wall Street Journal