MIT researchers say they have developed an energy storage system that could allow homes to store their own power without external batteries and highways to charge electric vehicles as they traveled on the road — no charging stations needed.
And the best part, the researchers say, is their system, called a supercapacitor, could be built from three of the world’s most abundant materials: cement, water, and carbon.
The researchers, who work at MIT’s Concrete Sustainability Hub, recently reported their breakthrough in the Proceedings of the National Academy of Sciences, a peer-reviewed scientific journal. They detailed how a tiny prototype — around 1 centimeter wide and 1 millimeter thick — powered an LED light at least 10,000 times.
The next step: developing large-scale supercapacitors to store wind, solar, and other renewable energy to help accelerate the transition from fossil fuels.
“Energy storage is a global problem,” said Franz-Josef Ulm, a professor of civil and environmental engineering at MIT and one of the creators of the supercapacitor. “If we want to curb the environmental footprint, we need to get serious and come up with innovative ideas to reach these goals.”
The supercapacitor, still years from commercialization, is part of the drive to improve storage systems considered critical to modernizing the power grid and do it with cheap, widely available materials. In 2022, MIT released a report saying that storing renewable energy at the scale needed to wean the world from fossil fuels was financially and technologically possible. But the cost and difficulty of obtaining critical components such as lithium, cobalt, and rare earth minerals pose significant challenges to achieving that goal, researchers said.
But engineers at MIT are not the only ones looking to solve this problem. Form Energy, a green energy supplier in Somerville, is developing batteries based on iron — another abundant material. Other MIT researchers, who founded the Marlborough startup Ambri, have developed a liquid-metal battery, which uses common materials such as calcium.
“The problem is that the lithium resources in the world are limited [and] many of the other technologies need rare earth materials which are also limited,” Soumendra Basu, a professor of material science and mechanical engineering at Boston University said. “So, to make energy storage with things that are abundantly available is a big deal.”
Ulm and his colleagues began working on the supercapacitor in March 2020, when they realized the potential of cement and carbon black, a powdery, black substance that conducts electricity. The technology is based, in some ways, on the notion that opposites attract.
Cement mixes easily with water, but carbon black repels water. When cement and carbon black are mixed with water, the carbon black clumps, permeating the concrete as a network of interconnected branches. Those branches provide the pathways to store the energy within the concrete.
Since cement is the main component, the energy storage system could be incorporated into buildings and roads. The foundation of a house, for example, could essentially become a battery, plugging directly into solar panels during the day and storing electricity to power lights, appliances, and heating and cooling systems at night.
By incorporating the cement-based energy storage system into pavement, the supercapacitor could work like a wireless charger for electric vehicles, potentially solving one of the biggest problems facing widespread EV adoption — a lack of charging stations. Energy stored in the road would charge the car battery as the EVs traveled over it, much like wireless cellphone charges.
Other efforts to turn roadways into EV chargers are underway, but using different technologies. In Indiana, the state Department of Transportation and Purdue University are using coils in the road to charge heavy-duty trucks as they drive.
Since transportation, buildings, and power plants account for large shares of greenhouse gas emissions, the MIT researchers say their energy storage system could help accelerate the adoption of clean technologies crucial to slowing climate change. “It’s something that we believe can permeate quickly into the real world,” said Admir Masic, associate professor of civil and environmental engineering at MIT and one of the creators of the supercapacitor.
The researchers still face considerable engineering challenges. For example, adding more carbon black increases the storage capacity of the cement mixture. But carbon black also degrades the structural integrity of the cement.
Michael Gevelber, associate professor of mechanical engineering at Boston University, said structural integrity concerns make it too risky to incorporate the energy-storage system into buildings and roads. He said other storage technologies, such as Ambri’s liquid-metal battery, are more developed, safer, and cheaper.
It “poses a question whether [the MIT supercapacitor] is really going to be that practical,” Gevelber said.
But the MIT researchers say they have a mixture they call the “sweet spot”: 90 percent cement and 10 percent carbon black. At those concentrations, the cement can stay strong and the supercapacitor can still hold a large amount of energy.
“Imagine our new devices as a multifunctional bone-like structure. We will need to design to compromise on some of these features, but still optimize for multifunctional performance,” Masic said. “It still has that backbone of cement.”
He also suggested that the supercapacitor could be used in addition to regular cement to make sure that homes and buildings maintain structural integrity.
Like many green technologies, this supercapacitor has its own impact on climate. Cement production contributes to around 7 percent of the world’s carbon emissions, according to the International Energy Agency, but some estimates put it as high as 9 percent.
Cement’s carbon footprint, however, is much smaller than the transportation sector’s. The emissions avoided by enabling greater use of clean energy and electric vehicles more than offsets emissions produced by concrete manufacturing, the MIT researchers said.
“This technology will allow us to efficiently move from non-renewables that are burning fuels and emitting CO2 into the atmosphere to renewable energy,” Masic said.
The researchers, meanwhile, are forging ahead. They are working to build construction bricks with the storage capacity of a 12-volt battery. Prototypes for energy-independent homes could be developed in three to five years, the researchers said, followed by self-charging parking spots and roads in about five years.
“There will be a lot of engineering challenges,” said Basu, the BU materials and engineering professor. ”But in terms of the scientific challenge of creating a good supercapacitor to do this, they’ve made great progress.”