A bubble-wrapped, sponge-like device that soaks up natural sunlight and heats water to boiling temperatures, generating steam through its pores. Credit: George Ni at MIT
The solar thermal energy conversion system can easily generate steam from sunlight. It can help make technologies that rely on steam, like seawater desalination, wastewater treatment, residential water heating, medical tool sterilization and power generation, more efficient and affordable. The new device floats on water, converting 20% of incoming solar energy into steam at 100 degrees Celsius without expensive optical concentration devices and is made of cheap, commercially available materials, including bubble wrap and a polystyrene (plastic) foam.
“The system we have developed enables us to generate steam with solar energy without having to rely on direct sunlight,” said Dr. TieJun Zhang, Masdar Institute Assistant Professor of Mechanical and Materials Engineering. “”The technology is particularly suited for the UAE’s dusty climate, as it fully uses the entire spectrum of sunlight for thermal applications rather than just the direct portion, which can be hindered by the aerosols,” he added.
The receiver’s design is relatively simple: A floating, sponge-like device made of a spectrally-selective absorber allows visible light energy from the sun in, while restricting the amount of heat that radiates back out into the atmosphere. This heat-trapping effect significantly improves the device’s sunlight-to-steam efficiency.
The absorber is sandwiched between a top bubble-wrap layer, which allows for sunlight absorption while reducing the amount of heat lost to the air through convection, and a bottom insulating foam layer, which floats the entire structure on a body of water and reduces the thermal loss of the generated heat to the water below. The floating receiver acts like a sponge, constantly soaking up water and evaporating it, producing a continuous stream of steam.
The solar receiver was validated at MIT, where it demonstrated the ability to rapidly reach 100°C and generate steam during periods of low direct sunlight, such as during non-summer months and heavy cloud coverage.
“The technology we have demonstrated is particularly attractive for hot-arid region such as Abu Dhabi for potential applications in waste water treatment, sea water desalination, and even power generation,” Dr. Chen said. http://www.newswise.com/articles/masdar-institute-and-the-massachusetts-institute-of-technology-mit-develop-low-cost-solar-device-that-converts-sunlight-to-steam-in-dusty-environment
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