To examine this effect, a process-chain-analysis for a complete cycle of production, use, and recycling is carried out. In carrying out that, the results from the examinations above will be taken into account:
• Energy expense for production
• Transport and installation
• Yield of the PV generators during their lifetime
Due to a lack of industrial experience in recycling of PV modules, a recycling rate of 25% was taken for granted. This value represents a lower limit, other examinations such as Bruton et al. 1994 claim that values of up to 70% are feasible. Figure 9.3 shows the principal difference in terms of CO2-emission resp. CO2-reduction between conventional and PV power plants. While the PV power plant at the beginning of its life-cycle is showing some negative contribution to CO2-reduction (but later it reduces CO2-quite well). The contribution of conventional fuel-based power plants is always negative over the entire life cycle.
Fig. 9.3. Reduction of CO2 during a life cycle of an 4.5 GWp PV power plant operated in Germany in comparison to a 700 MW coal power plant with the same electrical yield (3.5 TWh/a).