Storing energy is among the world's greatest challenges, leading to an array of new technologies proposed as the solution. Perhaps the most surprising is to turn the bricks from which our houses are made into energy storage devices, holding onto electricity for use when we can't tap the wind or sun.
There is an easy way to turn a brick, or any other heavy object for that matter, into a store of energy – simply raise it up in a gravitational field and then use the work it does as it falls to power a generator. Architects also make great use of bricks' thermal capacity to hold onto the day's heat for nighttime warmth. However, Dr Julio D'Arcy of Washington University, St Louis, has something more exotic in mind.
D'Arcy noted bricks are usually red or light brown, a color given to them by hematite, a pigment humans have been using for at least 73,000 years. Having worked on the chemistry of rust, D'Arcy and colleagues were aware hematite can serve as an electrode, and the porous microstructure of bricks makes them well-suited to the task.
D'Arcy permeated two vapors through this porous structure. Encountering the hematite caused the vapors to form a polymer called PEDOT on deposition. In the process, D'Arcy turned an 8-percent hematite brick into a supercapacitor capable of storing charge and releasing it when needed.
In Nature Communications, D'Arcy reports the product is as stable as bricks and mortar, surviving 10,000 cycles of charge and discharge with 90 percent efficiency and unaffected by rain or temperature. We've all had the experience of a piece of fancy electrical equipment turn into a brick – who knew the opposite was also true?
D'Arcy's bricks can't remotely compete on energy density with lithium-ion batteries, so we certainly shouldn't expect them to be powering the cars of the future, let alone airplanes. So far, all D'Arcy has done with the stored energy is light a single LED for five minutes with three bricks.
On the other hand, the materials are certainly cheap, abundant, and able to serve their normal purpose while also storing electricity. D'Arcy foresees 50 bricks providing five hours of emergency lighting after being charged during the day by solar panels.
"Our method works with regular brick or recycled bricks, and we can make our own bricks as well," D'Arcy said in a statement, adding that the off the shelf bricks were bought for 65 cents each.
For PEDOT-layered bricks to become a widespread method of bulk energy storage, they will have to out-perform traditional batteries, newer flow battery systems, pumped hydro, compressed air, concrete-stacking cranes, and many other options. However, with many of these being limited in the locations where they can be applied, D'Arcy's idea may be another brick in the wall to protect the world we love from climate change's rising tide.