By Joshua Worth

Professor Luping Tang

Imagine an entire 20-story concrete building that can store energy like a giant battery. Thanks to unique research from Chalmers University of Technology in Sweden, such a vision could someday become a reality. Researchers from the Department of Architecture and Civil Engineering recently published an article outlining a new concept for rechargeable batteries made of concrete as part of a research project funded by the Swedish Energy Agency.

The ever-growing need for sustainable building materials poses great challenges for researchers. Dr. Emma Zhang, formerly of Chalmers University of Technology and now senior development scientist at Delta of Sweden, joined Professor Luping Tang’s research group several years ago to search for the building materials of the future. Together they have succeeded in developing the world’s first concept for this type of battery.

The concept starts with a cement-based mixture with short carbon fibers added to increase the conductivity and flexural toughness. Then, a metal-coated carbon fiber mesh is embedded within the mixture  – iron for the anode and nickel for the cathode. Extensive experimentation resulted in the prototype the researchers now present. “Results from earlier studies investigating concrete battery technology showed very low performance, so we realized we had to think out of the box, to come up with another way to produce the electrode. This particular idea we have developed – which is also rechargeable – has never been explored before. Now we have proof of concept at lab scale,” Zhang explains.

Tang and Zhang’s research has produced a rechargeable cement-based battery with an average energy density of 7 watt-hours per square meter (or 0.8 watt-hours per liter). Energy density is used to express the capacity of the battery, and a modest estimate says the performance of the new Chalmers battery could be more than ten times that of earlier attempts at concrete batteries. The energy density is still low compared to commercial batteries, but this limitation could be overcome thanks to the huge volume at which the battery could be constructed when used in buildings.

The fact that the battery is rechargeable is its most important quality, and the possibilities for utilization if the concept is further developed and commercialized are almost staggering. Energy storage is an obvious possibility, and monitoring is another. The researchers see applications that could range from powering LEDs, providing 4G connections in remote areas, or cathodic protection against corrosion in concrete infrastructure. “It could also be coupled with solar panels for example, to provide electricity and become the energy source for monitoring systems in highways or bridges, where sensors operated by a concrete battery could detect cracking or corrosion,” suggests Zhang.

The prototype battery

The concept of using structures and buildings in this way could prove revolutionary because it would offer a solution to the energy crisis by providing a large volume of energy storage. Concrete, which is formed by mixing cement with other ingredients, is the world’s most commonly used building material. From a sustainability perspective, it is far from ideal, but the potential to add functionality to it could offer a new dimension. Zhang comments, “We have a vision that in the future, this technology could allow for whole sections of multi-story buildings made of functional concrete. Considering that any concrete surface could have a layer of this electrode embedded, we are talking about enormous volumes of functional concrete.”

Fellow researcher Emma Zhang

The idea is still at an early stage. The technical questions remaining to be solved before commercialization can be a reality include extending the service life of the battery and the development of recycling techniques. “Since concrete infrastructure is usually built to last 50 or even 100 years, the batteries would need to be refined to match this or be easier to exchange and recycle when their service life is over. For now, this offers a major challenge from a technical point of view,” says Zhang.

But the researchers are hopeful their innovation has a lot to offer. “We are convinced this concept makes for a great contribution to allowing future building materials to have additional functions such as renewable energy sources,” concludes Tang.