In some parts of the world, one of the main ways of obtaining drinking water involves using the heat of the sun to boil salty or tainted water. That process, known as "solar steam generation," may soon be made simpler and less expensive … using burnt wood.
The basic idea behind solar steam generation is that untreated water gets drawn up through a surface-located material that's heated by sunlight, to the point that the water boils. The resulting steam rises, condenses and is collected in the form of purified water, while the salt and/or contaminants are left behind.
When it comes to the material used, scientists have recently had the most success utilizing things like graphite and copper. A University of Maryland team led by Liangbing Hu, however, has achieved similar results using wood that's carbonized (burned black) on the upper surface, to help it absorb solar heat.
The best results were obtained utilizing wood that was particularly porous, such as poplar and pine. Those pores drew the water into the wood from underneath, and carried it to the surface by capillary action. Once on the solar-heated surface it boiled away, thus drawing more water up from below.
The wooden blocks used in the lab tests were about the size of the palm of a hand. That said, Hu believes that the technology could easily be scaled up for use in water treatment plants.
A paper on the Maryland research was published this week in the journal Joule.