Researchers in Sweden have developed a technique to produce rechargeable batteries made of concrete.
This approach could turn buildings themselves into energy storage systems, but has a number of issues to overcome. This follows several projects to use building materials for energy harvesting from light or heat.
The team from the Department of Architecture and Civil Engineering of Chalmers University recently developed a prototype of the concrete battery. This uses a cement-based mixture with small amounts of short carbon fibres added to increase the conductivity and flexural toughness. Then, embedded within the mixture is a metal-coated carbon fibre mesh - iron for the anode, and nickel for the cathode.
This had an average energy density of 7Wh per square metre (or 0.8 Wh per litre), ten times that of previous attempts at building a concrete battery. The energy density is still low in comparison to commercial batteries, but this is less relevant as a building can provide a large volume for storage.
"Results from earlier studies investigating concrete battery technology showed very low performance, so we realised we had to think out of the box, to come up with another way to produce the electrode. This particular idea that we have developed - which is also rechargeable - has never been explored before. Now we have proof of concept at lab scale," said research Dr Emma Zhang.
"We have a vision that in the future this technology could allow for whole sections of multi-storey buildings made of functional concrete. Considering that any concrete surface could have a layer of this electrode embedded, we are talking about enormous volumes of functional concrete," she said.
The researchers see applications that could range from powering LEDs, providing 4G connections in remote areas, or cathodic protection against corrosion in concrete infrastructure.
"It could also be coupled with solar cell panels for example, to provide electricity and become the energy source for monitoring systems in highways or bridges, where sensors operated by a concrete battery could detect cracking or corrosion," said Zhang.
The technical questions remaining to be solved for commercialisation of the technique include extending the service life of the battery, and the development of recycling techniques. "Since concrete infrastructure is usually built to last fifty or even a hundred years, the batteries would need to be refined to match this, or to be easier to exchange and recycle when their service life is over. For now, this offers a major challenge from a technical point of view," said Zhang.
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