System Efficiency (non-module) Considerations in the Sizing Solar Photovoltaic Plants

This paper presents a review of the energy efficiency in solar photovoltaic (SPV) systems with special reference to quantification and improvement of non-module system efficiency. The system efficiency (also called as performance ratio) is composed of photopic efficiency (losses in light energy before actually interacting with the SPV cell surface) and electrical efficiency (losses in electrical energy output generated by the module and before it is used by the load). Non module system efficiencies of operating SPV plants range between 54.93 % to 70.16 % with an average value of 62.32 % and standard deviation of 4.57 %. System efficiency considerations are important in design of power plants for given end user loads. If the calculations are on the basis of kWpeak, a typical 100 kWpeak system gives a peak output of 50-65 kW at the load point due to system efficiency and also lowering of module efficiency due to non-standard operating conditions. System efficiency excludes auxiliary power (2-4 % of the generated power), losses in battery (~20 %) due to storage component loss of energy generated due to non-availability of the grid (for grid tied systems) and stochastic incident radiation loss (~16 %). System efficiency presents possibilities of improvement to 75-80 % level through improved system design and improved operation and maintenance practices.