Concrete batteries sounds like fiction, but……. Concrete is perhaps the most-commonly used building material in the world. With a bit of tweaking, it could help to power our homes as well.
On a laboratory bench in Cambridge, Massachusetts, a stack of polished cylinders of black-colored concrete sit bathed in liquid and entwined in cables. To a casual observer, they aren’t doing much. But then Damian Stefaniuk flicks a switch. The blocks of human-made rock are wired up to an LED – and the bulb flickers into life.
“At first I didn’t believe it,” says Stefaniuk, describing the first time the LED lit up. “I thought that I hadn’t disconnected the external power source, and that was why the LED was on. It was a wonderful day. We invited students, and I invited professors to see. At first they didn’t believe that it worked either.” The reason for the excitement? This innocuous, dark lump of concrete could represent a future of energy storage.
The goal of most renewable energy sources is that of endless clean power, bestowed on us by the Sun, wind and sea. Yet the Sun isn’t always shining, the wind isn’t always blowing, and still waters do not, in megawatt terms, run deep. These energy sources are intermittent, which, in our energy-hungry modern world, poses a problem. It means that we need to store that energy, currently in batteries.
However, batteries rely on materials such as lithium, which the world does not have enough of to meet the demand of the world’s quest to decarbonise its energy and transport systems. There are only 101 known lithium mines in the world. In addition, environmental analysts note that lithium mining uses a lot of energy and water, and can also sometimes lead to toxic chemicals leaking into local water supplies.
This is where Stefaniuk and his concrete come in. He and his colleagues at Massachusetts Institute of Technology (MIT) have found a way of creating an energy storage device, known as a supercapacitor, from three basic, cheap materials – water, cement and a soot-like substance called carbon black.
Supercapacitors are highly efficient at storing energy but differ from batteries in some important ways. They can charge much more quickly than a lithium-ion battery, and don’t suffer from the same levels of degradation in performance. However, supercapacitors also release the power they store rapidly, making them less useful in devices such as mobile phones, laptops or electric cars where a steady supply of energy is needed over an extended period of time.
However, according to Stefaniuk, carbon-cement supercapacitors could make an important contribution to efforts to decarbonise the global economy, if they can be scaled up.” He and his fellow researchers at MIT, and Harvard University’s Wyss Institute for Biologically Inspired Engineering, envisage several applications for their supercapacitors.
One might be to create roads that store solar energy, and then release it to recharge electric cars wirelessly as they drive along. The rapid release of energy from the carbon-cement supercapacitor would allow vehicles to get a rapid boost to their batteries.
Another would be as energy-storing foundations of houses – “to have walls, or foundations, or columns, that are active not only in supporting a structure, but also in storing energy inside them”, says Stefaniuk.
There will be issues to overcome. While carbon-cement supercapacitors could help to reduce our reliance on lithium, they come with their own environmental impact. Cement production is responsible for 5-8% of carbon dioxide emissions from human activity globally, and the carbon-cement needed for the supercapacitors could not be retrofitted in existing structures without tearing them down first. Nevertheless, it seems to be a promising innovation, says Michael Short, who leads the Centre for Sustainable Engineering at Teesside University in the U.K. The research “opens many interesting potential avenues around the use of the build-environment itself as an energy storage medium”, he says. “Projects such as low-emissions cement and energy-storing concrete raise the prospect of a future where our offices, roads and homes play a significant part in a world powered by clean energy.”
Another great example of where science might be able to take us, if we keep the politicians and lobbyists out of it.
