Masdar Institute postdoctoral researcher, Dr. Jin You Lu, characterizes the nanoporous solar absorber with UV-Vis-NIR spectroscopy. Credit: Tahra Al Hammadi, Masdar Institute News
“Our research team has developed a simple and cost-effective fabrication technique to create solar absorbers that can harness a greater share of the solar spectrum, thus increasing their efficiencies, while also maintaining low emission levels,” said Masdar Institute’s Dr. TieJun Zhang, Assistant Professor of Mechanical and Materials Engineering.
Dr. Nicholas X. Fang, Professor of Mechanical Engineering at MIT said “We are very excited that this MIT-Masdar Institute collaboration has led to new insights in the emerging field of plasmonics, which quantify the interactions between the electromagnetic field and free electrons in a metal. By trapping sunlight with plasmonics, the solar absorber developed by our team can achieve higher efficiency levels. ” The work contributes to a larger Masdar Institute-MIT project aimed at developing a solar-powered, combined electrical power plant and cooling system.
The novel fabrication technique involves patterning a solar absorber with tiny holes with diameters <400 nm cut into the absorber at regular intervals, greatly enhancing the range of solar energy that can be absorbed. Close to 90% of the all the wavelengths of light are absorbed by the nano-hole patterned absorber. Unlike traditional solar absorbers, this absorber requires very little material with only 2 layers: a semiconductor film and a reflective metallic layer, with a total thickness of 170 nanometers.
“This idea can be applied to most conventional solar absorbers. With this unique patterning, the absorbers can be boosted to harvest more solar energy from the ultraviolet and visible regions of the electromagnetic spectrum,” said Dr. Jin You Lu. To optimize efficiency, it is desirable to maximize solar absorption and reduce the thermal radiation of heat from the absorber. But as the solar absorber takes in more energy, its temperature increases, causing it to lose energy in the form of thermal radiation.
The sweet spot of a solar absorber then, is the point when optimal levels of sunlight are absorbed with the least amount of energy escaping back into the atmosphere through radiation. “By taking advantage of the ultrathin film coatings and patterning, we are able to maximize the absorption spectrum while keeping the solar absorber’s emission levels quite low,” Dr. Lu explained.
The team is now working to optimize the system with alternative metals for the reflective metallic layer, eg aluminum, copper or silver, which will reduce the costs of the solar absorber further. https://news.masdar.ac.ae/explore-news/stories-by-type/transformation/item/9191-novel-solar-absorber-to-improve-efficiency-of-concentrating-solar-power-technology.html
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