From bricks to batteries

Ordinary house bricks can be turned into batteries that can store electricity, raising the possibility that buildings could one day become literal powerhouses.

The new technology uses the porous nature of fired red bricks by filling the holes with nanofibres of a conducting plastic that can store an electrical charge. The first bricks that have been made can store enough electricity to power small lights. If their storage capacity can be increased, however, they may become a low-cost alternative to the lithium-ion batteries currently in common use.

Solving the storage problem

Strictly speaking, the power bricks are supercapacitors rather than batteries. Supercapacitors store electricity as a static charge in solids, rather than through chemical reactions as in batteries. The advantage of supercapacitors is that they charge and discharge far faster than batteries, but, up to now, they could hold only a small fraction of the energy.

Researchers around the world are working to increase the energy density of supercapacitors, as well as the charging speed of batteries. Finding better ways to store electricity is an important part of fighting the climate crisis, as it would allow a lot of renewable energy to be stored until it is needed. The availability of the energy is not consistent, however.

“A solar cell on the roof of your house has to store electricity somewhere, and typically we use batteries,” said Julio D’Arcy, at Washington University in the US city of St Louis, who was part of the research team. “What we have done is provide a new ‘food-for-thought’ option, but we’re not there yet.”

The energy density of the first power bricks, reported in the journal Nature Communications, is just one per cent of that of lithium-ion batteries. D’Arcy believes this can be increased by more than ten times by adding materials such as metal oxides to store more charge in the brick, which would also make the power bricks sellable.

But the hope is eventually to match the energy density of lithium-ion batteries. “If so, this technology is way cheaper than lithium-ion batteries,” D’Arcy said. “It would be a different world, and you would not hear the words ‘lithium-ion battery’ again.”

Modifying the bricks

Dan Brett, a professor of electrochemical engineering at University College London, said: “Heat has been the overriding area of interest when considering energy storage within the fabric of buildings. This study shows there is potential to store electrical energy as well.” He thinks that while using bricks as supercapacitors is a long way off, the “principle is proven” and the idea has room for development.

The researchers created small prototypes of the power bricks using chemical vapours to react with the red iron oxides in the bricks and then to make a network of plastic nanofibres. A special plastic, called PEDOT, was used, as it is a very good conductor of electricity. The reactions turned the red bricks a dark blue colour.

Another advantage of supercapacitors is that they can be charged and recharged many more times than batteries before losing their ability to store electricity. The power bricks can go through 10,000 charging cycles before their capacity falls significantly.

The charge stored by the first bricks is too small to give a shock when touched. But a wall of connected bricks would need an insulating coating, and the scientists showed this using epoxy resin, which even allowed the bricks to work underwater.

The reactions that are used to create the power bricks may have a small weakening effect on their structures, D’Arcy said, but, in any case, bricks are most commonly used today to decorate the outside of houses.

Richard McMahon, a professor of power electronics at the University of Warwick in the UK, said the research was very interesting. “Energy storage is of great contemporary interest, especially in the electrical form. [But] although this work is an interesting demonstration of a possibility, it is a long way from practical application.”

Searching for alternatives

The cost of lithium-ion batteries has fallen by 90 per cent since 2010, and pumped hydropower projects are effective where there are mountains. But storing large amounts of electricity remains a challenge, leading to a search for alternatives.

One company uses gravity to store energy by stacking large bricks into a tower, then setting the energy free by dropping the bricks back to the ground. Similar schemes using heavy weights and mineshafts are also being explored.

Compressing air into a liquid to store energy is another option, with a large plant now in construction near Manchester. Some experts are looking to hydrogen, which can be produced by splitting water molecules using renewable energy.

© Guardian News & Media 2020