Solar Energy conversions

Category: Education

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SOLAR ENERGY Conversion of solar energy into one or more forms of energy is an important priority today. The earth receives 170 pet watts of solar radiation. 30% is reflected into space and the rest is absorbed by the earth. The surface receives about 47% of the total solar energy that reaches the Earth. Only this amount is usable.


PETE DEVICE Photon-enhanced thermionic emission (PETE), a process developed by engineers at Stanford University , that harnesses both the light and heat of the sun to generate electricity and increases the efficiency of solar power production by more than twice the current levels. The device developed for the process reaches peak efficiency after it reaches 200°C; most silicon solar cells become inert after reaching 100°C

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Most photovoltaic cells, such as those used in rooftop solar panels, use the semiconducting material silicon to convert the energy from photons of light to electricity. But the cells can only use a portion of the light spectrum, with the rest just generating heat. So it becomes less accurate & less efficiency.

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Melosh’s group figured out how to use that heat by coating a piece of semiconducting material with a thin layer of the metal cesium. It made the material able to use both light and heat to generate electricity. While most silicon solar cells have been rendered inert by the time the temperature reaches 100°C (373.15°K), the PETE device doesn’t hit peak efficiency until it is well over 200°C

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A small PETE device made with cesium-coated gallium nitride glows while being tested inside an ultra-high vacuum chamber. The light would come in and hit our PETE device first, where we would take advantage of both the incident light and the heat that it produces, and then we would dump the waste heat to their existing thermal conversion systems

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The researchers used a gallium nitride semiconductor in the "proof of concept" tests. But they used gallium nitride because it was the only material that able to withstand at high temperature range. They are already exploring other materials that might work.

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advantage of the PETE system is that by using it in solar concentrators, the amount of semiconductor material needed for a device is quite small

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The cost of materials has been one of the limiting factors in the development of the solar power industry, so reducing the amount of investment capital needed to build a solar farm is a big advance.

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The PETE process could really give the feasibility of solar power a big boost. Even if we don't achieve perfect efficiency, let's say we give a 10 percent boost to the efficiency of solar conversion, going from 20 percent efficiency to 30 percent, that is still a 50 percent increase overall. And that is still a big enough increase that it could make solar energy competitive with oil.

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