by Jaymi Heimbuch, San Francisco, Californiaon 03.22.11
Press photos via memsys
Using desalination to provide water to large communities is a controversial topic. But desalination has its uses where no one would argue its benefits — for instance, in a disaster area desal could be life saving. But how does one go about getting a plant to an area in need of fresh water supplies? Well, through our favorite method of course: convert a shipping container. But how does a shipping container-desal plant get the energy to run a process like reverse oasmosis? Our other favorite method, of course: solar power. A company from Singapore called memsys has developed a new technology that can trim the costs of desalination and make it more mobile. They’re using a process called vacuum multieffect membrane distillation — a mouthful to say, but promising for fresh water supplies.
The new process by memsys combines the two most popular forms of desal tech, thermal distillation and membrane distillation. The process includes a vacuum in which water is boiled at low temperatures, from 50-80 degrees Celcius, and the steam is passed through several membrane distillation processes at progressively lower temperatures and pressures. Energy is recovered during each step, in order to power the next step, thereby making the entire process far more energy efficient.
“We have the first modular thermal separation process,” Götz Lange, managing director of memsys, said during an interview with The New York Times. “We didn’t change the thermal technology itself — you can’t change physics — we are just the first to put this advanced technology of thermal separation into a very tiny, cheap and reliable modular concept.”
The article reports, “After seven years of development, a small demonstration unit, powered by solar energy for extra sustainability, was installed last year at Marina Barrage, a dam completed in 2008 across the mouth of Marina Bay that has converted what is left of the old Singapore harbor after massive land reclamation, into a freshwater reservoir.”
Designed for disaster relief, the shipping container unit can run entirely on solar power, and can produce 265 gallons of fresh water daily. The technology is already getting attention from businesses such as IBM, who is using it in a desalination project powered by waste heat from a concentrated photovoltaic generator, and an Australian company that wants to use the technology to clean brackish groundwater in a remote area in Western Australia.
While the technology might have a high per-unit price to start, that cost could come down. And when it comes to providing relief for disaster areas, it would be well worth the cost.