Researchers working at MIT's Department of Mechanical Engineering claim to have produced a sponge-like substance that helps convert water to steam using sunlight one-hundredth as bright as that required by conventional steam-producing solar generators. A composite of graphite flakes layered on a bed of carbon foam, the new material is reported to convert as much as 85 percent of received solar energy into steam.
In practice, the scientists say that the graphite flakes and carbon foam composite that they've created forms a porous insulating material structure that floats on water. After a number of experiments, the scientists found that the best method to maximize heat retention properties in the top layer was to exfoliate (expand a material by heating so that it increases in volume and lowers in density) graphite by cooking it in a microwave, causing it to bubble and swell. The outcome is an exceedingly permeable top layer able to maximize absorption and retention of solar energy.