Hybrid Solar Thermoelectric and Photovoltaic Energy Conversion

We are investigating hybrid technology that combines photovoltaics with thermoelectrics to convert solar light into electric energy. In brief, the rationale behind hybrid systems is to fully harness the energy embedded in the incoming solar radiation by combining a photovoltaic (PV) module with its narrow absorption wavelength range with a thermoelectric (TE) generator characterized by constant conversion efficiency in the whole solar radiation spectrum.

The primary objective of the investigation is the development of a prototype hybrid PV and TE devices that have the potential to be low-cost and high efficiency.

System design and optimization needs will be carried out in order to determine the devices and system configurations. The modeling will provide guidance for experiments. There are very few works so far on the above-discussed ideas, this underlines the novelty of this project although it also implies little work carried out on both modeling and experimental characterization.

Design of hybrid system. We have developed a methodology aimed at designing an optimized hybrid system with the highest possible solar energy to electricity transformation efficiency. The method provides the design constraints for the design of selective mirrors that split the broad solar spectrum into two parts: one directed to the PV element and one directed to the TE module. It gives the guideline for the combination of PV and STG modules in the most efficient way and enables the realization of the full potential of such hybrid systems.

The model uses the experimental external quantum efficiency (EQE) data for a specific solar cell module and the reported efficiency of STG. The approach can be extended to different configurations as long as one can provide EQE data.

Solar TE Modeling and Cell Fabrication. A solar thermoelectric generator prototype is under construction and it will undergo testing shortly. We wish to obtain efficiency results for the STG module using nanostructured material with an improved figure of merit ZT. The test results will be compared to the modeling results that describes the efficiency of the STG taking into account for the radiation and conductive losses within the system and the material properties of the thermoelectric employed.

Design and Fabrication of Frequency Selective Surfaces. The efficiency of STG depends strongly on the selective surfaces. We have been exploring the idea of using surface plasmons to enhance surface absorption in the solar spectrum while minimizing thermal emission at STC operation temperature. As a first step, we investigated theoretically the surface-plasmon enhanced light absorption in silicon.