Solar thermal aerogel receivers in solar heaters

Computer Engineering

Solar energy recovery has begun to take its place all over the world on the energy market due to the pureness of its electricity production. Commercial use of solar energy is unfortunately still rather small, mostly due to high prices and low efficiency compared to other sources. Current solar thermal receivers are insulated with vacuum tubes. This technology replaces these vacuum tubes with silica aerogels. Silica aerogels have an intrinsic spectral selectivity that allows them to pass solar radiation yet trap infrared radiation. In this way, they are both optically transparent and thermally insulating. By controlling the pH and drying time during processing, the aerogel microstructure can be optimized for this application. Through this technique, 95.5% solar weighted transmittance and a heat transfer coefficient <7 W/m2K were demonstrated for an 8 mm thick aerogel between 400°C and 100°C. These properties were also retained after the sample was exposed to 400°C and >80% relative humidity for >100 hours. By reducing the thermal losses from the system, aerogels also reduce the amount of optical concentration required for a desired thermal efficiency, which is why LFRs can be used instead of PTCs. STAR is not be susceptible to loss of vacuum which decreases annual energy average exergetic efficiency. Also, the STAR design allows for operating temperatures comparable to PTC receivers with less concentration area, meaning less land usage without sacrificing significant efficiency.

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