Monday, August 22, 2016

Bubble Wrap:  The Key to a New Floating Solar Thermal System

 A Multilayered "solar receiver" that floats on water (Photo Credit: George Ni/MIT) Click to Enlarge.
Solar thermal energy uses heat from the sun to generate electricity, heat and desalinate water, and treat wastewater, among other things.  However, it usually requires a costly array of mirrors to concentrate sunlight. Now scientists have developed a floating system that can boil water without such concentrators.
The new system can boil water under normal levels of sunlight, generating steam without optical concentration. It consists of a multilayered structure, a "solar receiver," that floats on water.
The researchers note that they made the solar receiver from a variety of low-cost and commercially available materials, with the system costing roughly US $6 per square meter overall.  By using even cheaper materials, they suggested it could be made for about $2 per square meter.  In contrast, solar thermal energy systems with optical concentrators that track the sun can cost as much as $200 per square meter.

The system can generate both high-temperature steam and lower-temperature vapor.  "Our system is about 20 percent efficient in terms of converting solar energy for steam generation," Ni says.  "We have much higher efficiency—about 70 percent—for lower-temperature vapor generation."

Near-term applications for this solar receiver may include desalination and wastewater treatment.  For desalination, the researchers would tweak the system to maximize production of lower-temperature water vapor and then develop a way to condense the vapor for collection. For wastewater treatment, the researchers would let the vapor dissipate into the atmosphere, "leaving behind smaller but more manageable quantities of concentrated waste," George Ni, a mechanical engineer at the Massachusetts Institute of Technology, says.

Read more at Bubble Wrap:  The Key to a New Floating Solar Thermal System

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