An energy harvesting breakthrough
January 20, 2014 | By
Barbara Vergetis Lundin
MIT researchers have developed a new approach to harvesting solar energy that could improve efficiency by using sunlight to heat a high-temperature material whose infrared radiation would then be collected by a conventional photovoltaic cell. This technique could also make it easier to store the energy for later use.
According to the researchers, such a system combines the advantages of solar photovoltaic systems, which turn sunlight directly into electricity, and solar thermal systems, which can have an advantage for delayed use because heat can be more easily stored than electricity. The new solar thermophotovoltaic (STPV) systems could provide efficiency because of their broadband absorption of sunlight, scalability and compactness, and ease of energy storage. But obstacles threaten the potential of the technology, as previous experiments have been unable to produce a STPV device with efficiency of greater than 1 percent. However, the research team has already produced an initial test device with a measured efficiency of 3.2 percent, but it will have to reach 20 percent efficiency to be commercially viable. The team used simulated sunlight in their research and found that its peak efficiency came when its intensity was equal to a focusing system that concentrates sunlight by a factor of 750. This light heated the absorber-emitter to a temperature of 962 degrees Celsius. This level of concentration is already much lower than in previous attempts at STPV systems, which concentrated sunlight by a factor of several thousand; however, the researchers say that with further optimization, it should be possible to get the same kind of enhancement at even lower sunlight concentrations, making the systems easier to operate. For more:
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