Most solar and solar thermal systems work by harnessing the bright light of the sun and converting it to electricity and/or heat. Their effectiveness is, to some degree, dependent on their level of exposure to light. When the sun is low on the horizon, these systems are low on output. Researchers at Wake Forest University point out that there is more to the energy from the sun than what we are able to see. The sun emits a broad spectrum of energy that is essentially invisible to the naked eye and, according to Wake Forest researchers, that invisible energy was just begging to be tapped.
According to a recent announcement from the university, it has developed a solar thermal device that harnesses infra-red solar energy in even weak, but visible light, then converts it to electricity and heat that can be used to warm a home and, potentially, cut home heating costs by as much as 40%.
The researchers’ new solar thermal device uses an array of clear tubes that are 5 millimeters in diameter. Those tubes are filled with an oil that is mixed with a special dye, The mixture flows through the tubes, which lay flat within the device. The solar thermal system works by drawing heat from any visible light and infra-red radiation. That energy super-heats the oil mixture, which is then converted to electricity by a spray-on polymer photovoltaic on the back of the tubes.
Wake Forest researchers point out that standard, rooftop solar cells miss about 75 percent of the sun’s rays at any given time because they can’t take advantage of infra-red heat. As a result, they are typically most effective between 10:00 AM and 2:00 PM. Because of the curvature of the tubes inside this new device, it is able to draw energy virtually from sunrise to sunset. The report goes on to say that “tests of the solar-thermal device have shown 30 percent efficiency in converting solar energy to power. By comparison, a standard solar cell with a polymer absorber has shown no greater than 8 percent conversion efficiency.”
An added advantage to the device is that it is super flat and can harness energy at oblique angles. That sort of form factor should allow it to be stealthily integrated into building projects by manufacturing it to look just like standard roofing tiles. The research team says it intends to build the first square-meter-size solar-thermal cell sometime this summer.
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