Electrified Concrete Roads Could Help Solve the Recharge Riddle

Tesla’s Powerwall, a rectangular lithium-ion battery designed to be mounted on walls, can provide approximately half a day’s worth of power for your home. However, what if your home itself could serve as the energy reservoir?

Scientists have devised an innovative method of storing electricity within cement, using readily available and cost-effective materials. When expanded, this cement-based solution could store ample energy within a home’s concrete foundation, effectively meeting its daily energy requirements. Upon further scalability, this technology could be employed to power electric vehicles as they traverse electrified roadways. The potential breakthrough lies in achieving this scalability at a low cost, which could offer an almost boundless capacity for storing energy generated by intermittent renewable sources like solar and wind.

Presently, these cement-based devices are compact, merely sufficient to power a handful of LED lightbulbs. However, initiatives are already in progress to enhance their scale. Sang Nguyen, a mechanical engineer at Imperial College London not involved in the research, asserts that if the technology can be successfully expanded, it holds significant promise.

These cement devices function as simplified supercapacitors, a type of battery. They encompass two conductive plates separated by an electrolyte capable of conducting ions, all enclosed within a thin membrane. During the charging process, positively charged ions accumulate on one plate while negatively charged ions amass on the other.

The storage capacity of these supercapacitors hinges on the total surface area of their conductive plates. Over decades, researchers have aimed to incorporate them into structural components like the concrete used in constructions or the carbon composites found in transportation. Unlike conventional batteries, supercapacitors usually utilize nonflammable electrolytes, enhancing safety.

Nonetheless, cement—integral to concrete—is ordinarily a subpar electrical conductor. Consequently, recent endeavors have sought to enhance cement’s conductivity by infusing it with conductive forms of carbon like graphene or carbon nanotubes. While effective, these additives are expensive and challenging to manufacture in the volumes required by the cement industry, as stated by Franz-Josef Ulm, a civil engineer at the Massachusetts Institute of Technology (MIT).

In pursuit of a more economical alternative, Ulm and his team turned to carbon black, an age-old powdered carbon variety used as a pigment since ancient times. Carbon black, apart from being abundant and low-cost, possesses exceptional conductivity.

The researchers blended a small proportion of carbon black with cement powder and water. While the water combined readily with the cement, the water-repellent carbon black particles clustered together, creating an interconnected web within the solidifying cement akin to a network of wires.

After fashioning these wired cement formations into small plates, they produced supercapacitors measuring 1 millimeter in thickness and 1 centimeter in width—similar in size to a button. Following the addition of a membrane and an electrolyte derived from potassium chloride (a basic salt) and water, the scientists sealed the sandwich-like structure. Subsequent connection to a wire and flipping a switch resulted in the illuminated activation of LED lights by the cement supercapacitors.

According to findings published in the Proceedings of the National Academy of Sciences, if carbon black-infused cement were employed to create a 45-cubic-meter volume of concrete (approximately the quantity used in a typical home’s foundation), it could store 10 kilowatt-hours of energy. This quantum of energy would be sufficient to power an average household for an entire day. In a broader application, such technology could be implemented in constructing roads, parking lots, or driveways, thereby enabling electrified concrete to store renewable energy and distribute it to electric vehicles via inductive charging. This approach might involve transmitting electricity to car underbellies through copper coils embedded in roadways, resembling the way wireless chargers operate for smartphones. Notably, similar technologies are already under development in Germany and the Netherlands.

By presenting a more cost-effective substitute for pricier batteries, electrified cement could democratize renewable energy storage, particularly in developing nations, according to Admir Masic, a co-author of the study and a chemist at MIT. This innovation could usher in an era of accessible energy storage across the globe.

To achieve success, researchers must scale up the small button-sized plates. However, this isn’t a simple task, as larger supercapacitors typically experience a decline in electrical conductivity, making energy injection and extraction more challenging. Ulm suggests that one solution involves incorporating more carbon black into the mixture, although not to an extent that jeopardizes the cement’s structural integrity. In their investigations of structural concrete, the team discovered that up to 10% carbon black can be added without significantly compromising its strength. Ulm indicates that they have secured a patent for their technology and are presently working on upscaling it to match the output of a 12-volt car battery.