Abstract
For photovoltaic (PV) energy systems, we estimated CO2 emissions per kWh under technology development and expansion of the cell production scale, considering the life cycle of the PV energy system, including as module production ana power plant construction. For polycrystalline silicon cells, CO2 emissions of a 3 kW PV system and a 1000 kW PV system were 17g-C/kWh and 39g-C/kWh, respectively, when the annual cell production scale was 10 MW. On the other hand for amorphous silicon cells, they were 10g-C/kWh and 47 g-C/kWh, respectively. In order to reduce CO2 emissions of PV energy systems, it is necessary to use less raw materials which are needed in proportion to the area of the module, such as alminum frame and cover grass. Improvement in total system efficiency, including the cell efficiency and the lifetime, is also effective in reducing CO2 emissions of PV energy system.
We also evaluated the relation of CO2 emissions of electric power output between PV energy system and utility to be used for module production for the case of a PV system being widely introduced into the utility grid, because the CO2 emissions of PV power output depend on utility power output.
