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B5: Energy system design and optimization
The exploitation of solar energy conversion has become fundamental in the present scenario of growing energy demand. Thus an improvement of the efficiency conversion in photovoltaic (PV) devices is necessary in order to promote a massive worldwide implementation of this source, especially in the form of distributed micro-generation. Since it is well known that the most relevant efficiency constraint, especially for single junction solar cells, comes from the unused heat within the device, the implementation of hybrid thermo-photovoltaic solutions seem to be a very attractive approach. Among the several hybrid solutions proposed so far in the literature1-5, the coupling between thermoelectric and PV devices looks to be one of the most interesting to improve efficiency in electricity micro-generation.
A complete understanding of the viable opportunities for this application starts from a proper definition and analysis of the thermal losses occurring in PV cells. In this communication we propose a novel analysis of such losses, decoupling source- and absorber-dependent losses. This analysis enables an evaluation of the actual recoverable amount of energy depending on the absorber used in the PV cell. It shows that, depending on the material choice, the maximum available thermal power spans from 420 W/m2 for solar cells using single crystal silicon to ≈ 170 W/m2 for amorphous silicon-based cells. The model also allows to account for the difference in the thermal response between bulk and thin film solar cells due to the different heat capacity.
References
(1) Kraemer, D. et al. Appl. Phys. Lett. 2008, 92, 243503.
(2) Chow, T. T. Appl. Energy 2010, 87, 365-379.
(3) Parida, B.; Iniyan, S.; Goic, R. Renew. Sust. Energy Rev. 2011, 15, 1625-1636.
(4) Wang, N. et al., Energy Environ. Sci. 2011, 4, 3676-3679.
(5) Park, K.-T. et al. Sci. Rep. 2013, 3, 2123.