Thermophotovoltaics.

About

Background: Several obstacles have prevented conventional thermophotovoltaics (TPV) systems from reaching widespread commercial success. Among these are (1) high cost for high performance III-IV semiconductor substrates and cells; (2) low system efficiencies due to small system sizes and edge effects, and inefficient spectral control; (3) the absence of storage, which forces TPV to compete directly with less expensive flat plate PV; and (4) a large mismatch in power density between the highly concentrated sunlight input needed to reach high temperatures (> 1000 °C) and the order of magnitude lower power density infrared light output from the emitter to the TPV cell. As a result there is a need for improved systems and methods to address the above mentioned deficiencies. It is with respect to these and other considerations that the present invention is directed. Invention: The current invention makes three major improvements over existing concentrated solar power technology and can potentially reduce the cost by 70%, which would make it highly competitive with fossil fueled plants. Ultimately this can supply fully dispatchable solar electricity at a cost competitive with conventional generation. The idea is a new system layout that utilizes the most efficient and lowest cost component technologies and links them together using a liquid metal heat transfer fluid (LMHTF). In short the idea is concentrated solar thermophotovoltaics (TPV) with liquid silicon thermal storage. The idea of TPV has been around for decades, but a fundamental mismatch in power density between the incoming light and reradiation to the PV module has prevented a highly efficient design from emerging. With the new technology we're developing in my research group, where we can use liquid metal (i.e. molten tin) as a high temperature liquid heat transfer fluid, we can now solve the power density mismatch problem in TPV and enable a high efficiency design. The system design involves capturing sunlight at high temperature (above the melting point of silicon) in the sensible heat of liquid tin. Then the tin is used to melt a large container of silicon, which serves as a thermal battery. When electricity is desired, liquid tin is used in a heat exchanger to carry the heat from the solidifying silicon battery to a dense array of TPV modules, which can convert the upper portion of the emission spectrum to electricity. The remaining energy in the spectrum is reflected back to the emitter via silver backed mirror. By packing the PV densely within the array, thermal losses are minimized and an improvement in efficiency of almost a factor of two is possible with existing InGaAs PV cells. Potential Commercial Applications: ·  Can be used in high power solar devices ·  Can be used for utility scale power production ·  Can be produced at a lower cost and with a higher efficiency