Buildings have a lot of surface area that's exposed to sunlight, so why just stop at rooftop solar panels? We've already seen solar energy-harvesting windows, and of course Tesla's solar roof. Thanks to research being carried out at the University of Exeter, we may soon also have the option of replacing opaque exterior walls with solar glass blocks.
Known as Solar Squared, the transparent blocks contain multiple optical elements that each focus incoming sunlight onto an individual solar cell. All of the cells within each block are linked together, and the blocks themselves can in turn be wired to one another, ultimately feeding into the building's electrical grid or a battery.