Nearly 97% of all the water on earth is salt water. The typical process to remove salt is by boiling the water and capturing the steam. Desalination is expensive and energy intensive. Presently, there are more than 18,000 desalination plants across 150 countries.
New federally funded research reveals a method of purifying water by using solar power. The research, titled "Nanophotonics-enabled solar membrane distillation for off-grid water purification" was published this month in Proceedings of the National Academy of Sciences journal.
"Direct solar desalination could be a game changer for some of the estimated 1 billion people who lack access to clean drinking water," said Qilin Li, co-author of the study. "This off-grid technology is capable of providing sufficient clean water for family use in a compact footprint, and it can be scaled up to provide water for larger communities."
Credit: Rice University
The device works in correlation with another technology developed at Rice University, known as membrane distillation. This type of distillation works by running hot salt water down one side of a porous surface and purified water down the other.
"We report a direct solar method for desalination that utilizes nanoparticle-assisted solar vaporization in a membrane distillation geometry," says the article. Engineered nanoparticles capture solar energy and change it to heat, to enable the distillation.
The researchers used a very thin solar-heated membrane. They were able to produce 6 liters (1.3 gallons) of water per hour, per square meter of membrane. The prospect is to make these membrane panels available in different sizes according to daily water production needs.
"Depending on the water production rate you need, you could calculate how much membrane area you would need," said Li. "For example, if you need 20 liters per hour, and the panels produce 6 liters per hour per square meter, you would order a little over 3 square meters of panels."