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                      -- Multi-layered solar still produces free drinking water

"A completely passive solar-powered desalination system developed by researchers at MIT and in China could provide more than 1.5 gallons of fresh drinking water per hour for every square meter of solar collecting area. Such systems could potentially serve off-grid arid coastal areas to provide an efficient, low-cost water source.

The system uses multiple layers of flat solar evaporators and condensers, lined up in a vertical array and topped with transparent aerogel insulation. It is described in a paper appearing today in the journal Energy and Environmental Science, authored by MIT doctoral students Lenan Zhang and Lin Zhao, postdoc Zhenyuan Xu, professor of mechanical engineering and department head Evelyn Wang, and eight others at MIT and at Shanghai Jiao Tong University in China.

The key to the system’s efficiency lies in the way it uses each of the multiple stages to desalinate the water. At each stage, heat released by the previous stage is harnessed instead of wasted. In this way, the team’s demonstration device can achieve an overall efficiency of 385 percent in converting the energy of sunlight into the energy of water evaporation.
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"10th February 2020 11:00 am

Engineers from MIT and China’s Shanghai Jiao Tong University have developed a solar still that can desalinate a record amount of water.

Known as the thermally-localised multistage solar still (TMSS), the device evaporates and condenses water numerous times, working in much the same way as alcohol stills. It has multiple layers of flat solar evaporators and condensers, positioned in a vertical array with an insulating aerogel at the top.

At each stage, heat released by the previous stage is harnessed rather than wasted, meaning energy from the sun is converted to evaporation energy with an overall efficiency of 385 per cent. On a rooftop in MIT, the TMSS produced 5.78 litres of water a day per square metre of solar material. According to MIT professor of mechanical engineering Evelyn Wang, this is twice as much water as any other passive solar-powered desalination system has produced."