Your Home Could Soon Power Itself—With Concrete

Homes could soon feature columns of concrete mixed with charcoal that have the ability to store electricity and discharge it when needed by occupants.

Researchers at the Massachusetts Institute of Technology (MIT) have successfully developed a supercapacitor—which can act like a battery, but they stress is different, as it doesn't degrade through use—out of widely available materials, in the hopes of providing a cheap and architectural way of saving renewable energy from going to waste.

The innovation comes at a time when many nations are standing up energy storage networks as production transitions away from fossil fuels, to avoid excess renewable energy from being wasted when demand is low and to meet consumer energy needs when demand is high.

But the designers of the concrete supercapacitors are already setting their sights on even more ambitious uses of the technology: from finding a way of charging electric vehicles while they are on the road to keeping the lights on when extreme weather events hit.

"These are sort of the frontiers where we are working right now with this technology, now we have shown how it scales," Franz-Josef Ulm, professor of engineering at MIT and the project's leader, told Newsweek. "These two materials here come together to form potentially an energy storage solution for everyone, everywhere."

How It Works

Unlike a battery, which converts chemical energy into electrical energy, a supercapacitor holds electrical energy in a conductive material—such as electrolytes, or salt water—on the surface of an electrode.

This conductive material is separated with an insulating one, stopping electrons from flowing like in a circuit, meaning they build up—like the static that builds up when you rub a balloon. But how do you make one out of concrete?

"Here, the wonder[s] of chemistry take place," Ulm explained. "When you mix cement—which loves water, it's hydrophilic—with carbon black [refined charcoal], which hates water, then the carbon black first clumps and then the same water is consumed within the hydration reaction" that forms solid concrete.

"As a consequence of this consumption, these clumps loosen and build up a volumetric wire throughout the material," he added. "That volumetric wire is everywhere, and as a consequence we can store [an] enormous amount of counter-charges from the salt solution onto this volumetric wire."

As concrete is naturally porous, those pores can be filled with salt water, connected by the carbon "wire" that runs through the concrete. In a disc between electrodes, it looks "a little bit like Oreos," Ulm said, which can be attached to each other in a stack.

A key concern in the transition to renewable energy is the use of rare earth materials such as lithium, which is mined in a handful of countries with questions about the impact on the environment and human rights, in batteries in electric vehicles to energy storage units.

By comparison, concrete and charcoal are materials that are widely available in most parts of the world—the former being regarded as the most consumed material after water. Ulm noted that, because concrete comes in powder form, the design of a supercapacitor can be fine-tuned to meet "any type of application."

They are also materials that are comparatively cheap. While the price of lithium is expected to rise by 4,000 percent in the next two decades, and a metric ton in the U.S. already costs $37,000, the same weight in concrete costs just $130.

While an average consumer lithium battery can be charged and discharged 300 to 500 times, Ulm said that "you can do this a zillion times without losing efficiency" with a supercapacitor, as it does not need to convert one form of energy into another.

Homes Reimagined

The wind isn't necessarily blowing or the sun shining when people want to watch the TV, and this poses an issue for renewable energy producers. As peaks in demand are offset from peaks in supply, it means fossil fuels are still relied on for when energy usage is highest, and a large amount of renewable energy goes to waste.

Originally conceived for homes that have their own wind turbine or solar panels, the concrete supercapacitors are aimed to be baked into the architecture of people's houses to account for this difference.

"You charge it during the day and during the nighttime, like a battery, you ... use the charge, which has been stored during the day," Ulm said.

He explained that changing whether the supercapacitor was needed for fast charging, such as with wind energy, or slower charging, such as with solar, was a matter of adapting the concrete's thickness. Each 3-centimeter Oreo holds a volt, so for the standard 110 volts needed for household appliances, a column of just under 11 feet would be needed—or roughly one story.

"A column [is] a visible thing, which everybody knows in their homes," Ulm said. "But columns are also used for piles in foundations. You can also lay them down—they don't have to be circular, they can be square ... In that sense, these materials can be built in, in this layered system, into the foundations, the walls, the structural elements actually in the home."

He added: "So we open here a new way of multifunctional design of buildings to combat the impacts of global warming." At the same time, as concrete production is responsible for 4 percent to 8 percent of global CO2 emissions, by giving it another function, "we also hope that the production of cement becomes part of the solution for combatting climate change."

However, not everyone has a solar panel on their roof, and the shift toward battery storage is motivated by entire energy grids switching to renewables. But Ulm suggested concrete supercapacitors could help there too.

"If everybody had one of these supercapacitors in their foundations [or] in their wall systems, and they were connected to the [energy] system, we would be talking about a real smart grid, in the sense that it involves everybody," he said. "Everybody is contributing with their building to achieving the energy transition."

Electric Avenues

Ulm and his team's ambitions for their concrete supercapacitors do not end with domestic energy storage. More and more people are switching to electric vehicles, but with them come complaints about charging infrastructure and their mileage between charges.

The MIT researchers are focusing on developing what Ulm describes as a "self-charging road," which, like charging an iPhone without a cable, aims to "store energy into the pavement structure" and use electromagnetic induction to charge an electric vehicle, either in a parking space or even "while you are driving."

Keeping the Lights On

As climate change worsens, extreme weather events are occurring with more regularity, including prolonged heatwaves and fast-spreading wildfires, deadly flash floods and unprecedented tropical storms.

When many of these weather phenomena occur, the first thing to be cut is the power. During wildfires, this is done for safety, while major storms often knock out power lines. Instead of having to fire up the generator, what if a home could carry on using the energy stored in its walls?

Ulm said he has already received similar requests about using the technology on the East Coast during hurricane season.

While he appears certain it can be done, the more porous a concrete is, the more brittle it is—so his team is working on ways of strengthening the outer structure of the supercapacitor columns to withstand extreme weather. "There will be a sweet spot for these particular applications," Ulm said.