Normally, the term “power brick” affectionately refers to the AC adapter of something like a laptop. But what if this term was quite literal, with an actual brick?
A team led by Hongmin Wang at the University of Washington set out to create a real powerhouse. More specifically, they wanted to see if they could use a vapor deposition technique to make ordinary red bricks into a part of a supercapacitor. That is actually not the case free as strange as it sounds, seeing that the red of a brick is an iron mineral, and iron is a common part of some battery chemistry. Bricks are also often porous, which means that there is a lot of surface where a thin coating can interact with that iron.
The process (something they had developed earlier) involves heating the brick in a box along with hydrochloric acid and an organic compound that is mercifully shortened to “EDOT.” The two liquid substances evaporate and condense on the envelope surface of the brick. The acid dissolves part of the iron mineral, and contains iron atoms that help the organic molecules to bond together to form polymer chains (graduated to “PEDOT”) that coat the surface. The polymer forms microscopic, entangled fibers that form a continuous and electrically conductive layer on each face of the brick, which remains otherwise. (However, this has the effect that the brick turns black.)
Electron microscope imaging scans with the fibrous PEDOT layer on the surface of three different bricks with varying porosity.
The team tested performance in a few configurations, including one with a solid gel electrolyte between the stones such as mortar. Decorating the whole thing in epoxy makes it waterproof (as in, “works under water” waterproof) and also prevents the electrolyte from ever drying out. Many combinations of bricks connected in series and parallel are apparently possible, although for testing they have bound three units of thin sugar cube-sized bricks in series. After fully charging in 15 seconds, this configuration powered an LED for about 11 minutes before the voltage dropped from the initial 2.7 Volts to below the required 2.5 Volts.
Three larger brick supercapacitors in series light an LED. The split brick on the right shows the color change of the PEDOT coating.
Even with full-size bricks, the total energy storage… is less than enormous. They estimate that a wall of this brick could hold about 1.6 watt-hours per square meter of wall area. This means that a wall three feet by six feet (10 feet by 20 feet) can hold about 20 watt-hours of electricity. As a result, the researchers’ pitch for this idea is less dramatic than “turn your house into a battery!”
“Our supercapacitor technology adds value to a ‘dirty cheap’ building material and demonstrates a scalable process that provides energy storage for deployment of embedded micro-devices in architectural applications that use exposed brick,” they write. These powered walls are unlikely to challenge Tesla’s Powerwall (13.5) kilowatt-hours in less than a square meter on the wall) every time fast. But it’s a creative concept – a supercapacity brick would definitely not be just another brick in the walls.
Nature Communication, 2020. DOI: 10.1038 / s41467-020-17708-1 (About DOIs).
