ENERGY EVALUATION OF SOLAR PHOTOVOLTAIC ENERGY-SYSTEMS

The energy balance of large-scale photovoltaic power systems was evaluated for both polycrystal silicon cells and amorphous silicon cells. The evaluated scale of their production were 10 MW/y, 1 GW/y. The energy payback time of 10 MW/y was 5.7 years for the polycrystal silicon cells and 6.3 years for the amorphous sillicon cells, which included construction energy for the power plant but excluded energy for storage. This estimation includes the introduction of current developing technologies and efficency improvement of PV cell production processes. Further reduction in energy payback time due to the progress of technology development and the effect of scale-up was expected for the production scale of 100 GW/y. These payback times were 3.2 years for the polycrystal silicon cells and 3.0 years for the amorphous silicon cells. Energy input for construction of the power station was relatively large in comparison with that for the production of PV cells. This suggested that the establishment of a more moderate system is essential for large-scale production of PV cells.