The search for better/cheaper methods of distilling water or generating steam has been ever on going. Now researchers from MIT and the Masdar Institute of Science and Technology, led by George Ni, describe a prototype design that boils water under ambient sunlight.

Central to their floating solar device is a “selective absorber”—a material that both absorbs the solar portion of the electromagnetic spectrum well and emits little back as infrared heat energy. For this, the researchers turn to a blue-black commercial coating commonly used in solar photovoltaic panels. The rest of the puzzle involves further minimizing heat loss from that absorber, either through convection of the air above it or conduction of heat into the water below the floating prototype.

…

But it’s probably not a last. The researchers used computer modeling to look for factors they could optimize, and they calculated that the device should make steam even at about half of direct sunlight’s full intensity. With that much wiggle room, they say that a cheaper, less effective absorber material could bring the cost down even more. The current design should only cost about $6 per square meter to make, and the researchers think they could reduce that to $2 per square meter. At that price, they estimate you could produce steam for about five percent of the cost of a system that has to concentrate sunlight.