Bricks as an energy storage medium: At the moment, a group of scientists at Washington University in St. Louis, Missouri, is busy researching the transformation of customary masonry bricks into supercapacitors. The result are bricks that can swiftly store electricity and then release it again. Julio M. D'Arcy, an assistant professor of chemistry, has together with his doctoral and graduate students devised a polymer coating made of nanofibers that are conductive and permeate the porous structure of the brick. The iron ions in the material are decisive when it comes to transforming the brick into a “smart brick”. “The brick’s pigment is essentially a form of iron corrosion which we can use to create a plastic that conducts electricity,” says D'Arcy. The details: The brick is heated and exposed in the process to hydrochloric acid. The flowing gases dislodge the iron ions in the brick. Parallel to this ethylendioxythiophene, which together with the iron ions forms the conductive polymer, the PEDOT. Thus encased in the brick, the polymer coating then serves as an ion swarm that stores and conducts electricity. By applying an epoxy resin, the fire-proof stone can also be sealed watertight and temperature-resistant. What brick is conductive can be simply gauged by the color, as owing to the PEDOT generated during the transformation it goes dark blue. “We have essentially turned a construction material into a semiconductor,” comments D'Arcy. In order to enable electricity current to flow between the bricks using a bi-electron system, all you need to do is subsequently stack the bricks.
The result are bricks that function as supercapacitors, meaning they swiftly store energy and release it, for example in order to power sensors or emergency lighting. Solar energy can be used to charge the smart bricks, for example by a PV array on the roof. At the current stage of research, the volume of energy each brick can store is as yet less than that of a Lithium-ion battery. “We’re working actively to increase the volume of energy that our bricks can store. If we succeed in scaling up the energy density, then mobile devices could be powered by the bricks. We believe that we’re close to achieving that goal as the latest lab results point in a promising direction,” reports D'Arcy. As regards sustainability, the purpose-developed polymer is not biodegradable, but, or so Julio D'Arcy explains, can be removed from the brick at the end of its lifecycle. Both components can then be reprocessed in as environmentally friendly a way as possible. Moreover, already recycled bricks can be transformed into new “smart bricks”, too.