Imagine the possibilities of energy being stored in the concrete foundation of a home to meet the residents’ electricity needs, or a concrete roadway providing contactless recharging for electric vehicles while on the move.
Researchers at the Massachusetts Institute of Technology (MIT) have created a new supercapacitor that could be a game-changer in energy storage for renewable energy sources such as solar, wind, and tidal power.
Made from a combination of commonly available materials such as cement, carbon black and water, the new energy-storing supercapacitor will provide a low-cost alternative to traditional batteries, and allow energy networks to remain stable despite fluctuations in renewable energy supply.
Published in the journal PNAS, the study is led by MIT Professors Franz-Josef Ulm, Admir Masic and Yang-Shao Horn, along with postdoctoral researchers Nicolas Chanut and Damian Stefaniuk at MIT’s Department of Civil and Environmental Engineering, James Weaver at the Wyss Institute, and Yunguang Zhu in MIT’s Department of Mechanical Engineering.
The researchers created their supercapacitor by adding carbon black, a highly conductive material to a concrete mixture along with cement powder and water, and letting it cure. Similar to the two poles of a rechargeable battery, when the two plates of the capacitor are connected to a source of electricity, energy is stored; when connected to a load, the stored energy flows back out to provide power.
Masic finds the material fascinating “because you have the most-used manmade material in the world, cement that is combined with carbon black, a well-known historical material; the Dead Sea Scrolls were written with it. You have these at least two-millennia-old materials that when you combine them in a specific manner you come up with a conductive nanocomposite, and that’s when things get really interesting.”
Explaining the curing process, he says, “The water is systematically consumed through cement hydration reactions, and this hydration fundamentally affects nanoparticles of carbon because they are hydrophobic (water repelling).”
As the mixture evolves, “the carbon black is self-assembling into a connected conductive wire,” he adds.
Given the huge need for big energy storage, supercapacitors made of this material have great potential to support the world’s transition to renewable energy, Ulm says. Existing batteries are too expensive and mostly rely on materials with limited supply such as lithium, necessitating cheaper alternatives.
“That’s where our technology is extremely promising, because cement is ubiquitous,” Ulm says.
“Since the concrete would retain its strength, a house with a foundation made of this material could store a day’s worth of energy produced by solar panels or windmills, and allow it to be used whenever it’s needed,” the researchers say. Another advantage is that supercapacitors can be charged and discharged much more rapidly than batteries.
After testing out the most effective mix of cement, carbon black, and water, the team created small supercapacitors, about the size of button-cell batteries to demonstrate and prove the concept. Based on the outcomes, they are planning to build larger versions that could store a “house-worth of power”.
The researchers also found that increasing the quantity of carbon black in the mix boosted storage capacity but reduced the structural strength of the concrete. Such mixes could be used in applications that do not have a structural role.
These carbon-cement supercapacitors are also being considered for concrete roadways that could store energy produced by solar panels installed along the road, with the energy then used to charge electric vehicles.
Describing the system as very scalable, Ulm says, “You can go from 1mm-thick electrodes to 1m-thick electrodes, and by doing so basically you can scale the energy storage capacity from lighting an LED for a few seconds, to powering a whole house.”
The study was supported by the MIT Concrete Sustainability Hub, with sponsorship by the Concrete Advancement Foundation.
Image source: MIT