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Photovoltaic energy conversion : an endoreversible process

Exploitable results

Research relevant to the development of thermodynamic analyses of photovoltaic energy conversion has been carried out.As a tool, the concept of endoreversible thermodynamics of photovoltaics has been introduced. Endoreversible processes are a special class of irreversible processing; the irreversibilities are all located in the transport of heat from the heat sources to the heat engine and from the heat engine to the heat sinks. It was demonstrated that photothermal solar energy conversion could be modelled as an endoreversible process. A photovoltaic converter proved to be more complicated than a photothermal one. A more general model of endoreversible engines was introduced, where thermodynamic reservoirs were characterized not merely by a temperature, but by a temperature and a chemical potential, and where not only energy but energy and matter were exchanged between reservoirs. The conversion efficiency of hybrid photothermal and photovoltaic convertors has been calculated. It was demonstrated that a hybrid converter could realise higher efficiencies than pure photovoltaic or photothermal converters. For a given light concentration and a given bandgap, a pure photothermal converter has only one degree of freedom, its temperature. Analogously, a pure photovoltaic converter has only degree of freedom, its bias voltage. A hybrid converter has 2 degrees of freedom, a temperature and a voltage. The maximum power point proved to be at negative voltage. A computer algebra has also been developed to handle symbolic equations in solar energy theory with speed and accuracy.