University’s solar-powered still improves ancient water cleaning technology
For for centuries people have used sunlight to filter water but a new solar technology could be a game changer
More than two-thirds of the earth’s surface is covered with water, but most of it is useless for healthy human hydration. Excluding seawater, glaciers and polar ice caps, less than 1 percent of the planet’s life-sustaining water is in lakes, rivers, streams and underground aquifers. Much of that readily available drinking water requires treatment to eradicate harmful microbes and toxins.
As a result, access to clean drinking water is limited and precarious for many of the world’s people. Water scarcity profoundly affects 1 out of 9 people, according to the Water Project, and most illnesses in underdeveloped countries are linked to poor water and sanitary conditions. Natural disasters like the 2010 Haiti earthquake or the 2004 Indian Ocean earthquake and tsunami can lead to emergency situations that affect millions of people who lose access to potable water.
The sheer number of impoverished people who are teetering on the edge of access to clean drinking water prompted a team of researchers at the State University of New York at Buffalo’s school of engineering and applied sciences to figure out a way to improve solar distillation, a long-established, cost-effective yet problematic process of extracting clean drinking water from contaminated sources using simple materials and sunlight.
“We have a lot of need for this technology and we hope we can collaborate with people, organizations and agencies to develop this,” said Qiaoqiang Gan, associate professor of electrical engineering at the university and a co-author of a recent study describing a new method to improve the efficiency of using sunlight to distill clean drinking water.
The idea of using the sun’s heat to vaporize and recondense water has been known since at least the 4th century B.C. when the Greek philosopher Aristotle first described that salt could be removed from seawater using the sun’s heat to create water vapor. Such solar stills have been used since the industrial revolution, but one major drawback to the technology has been the output. Evaporation and condensation are not fast processes, and most solar stills, especially simple, low-cost ones, are unable to produce enough water to sustain one person in survivalist mode.
But rising awareness of water scarcity issues has led researchers like Gan and his team in Buffalo to apply new techniques to make solar distillation more efficient. Their solar vapor generator and condenser uses porous paper covered with carbon black, a material that has a near-zero reflectivity and therefore absorbs a higher amount of solar heat. The carbon-covered paper is then placed over floating white polystyrene foam and a thermal insulator that helps concentrate the solar heat onto the carbon layer. The device is then placed on the surface of a dirty water source while the paper acts as a sponge and the carbon as an evaporator. The vapor then condenses on the angled wall of the vaporizer, seeping into a culvert that collects the potable water.
Gan and his team have claimed that their prototype produces as much as three times more potable water as comparable solar stills, or about 4.2 cups an hour under sunny conditions. The average healthy adult needs about eight cups of water a day. Crucially, this is all done using cheap materials that can be scaled, meaning arrays of floating stills could be tapped in emergency situations to provide a considerable amount of fresh drinking water to a disaster-struck community, especially in the sunny parts of Africa, Asia and Latin America.
In November, the researchers registered a company called Sunny Clean Water and are hoping to have a production-ready version of their prototype by the end of the year.
Gan, 37, spoke to Salon about his team’s work to improve the efficiency of a renewable-energy-using technology that’s been around for a very long time.