During normal operation, photovoltaic (PV) power systems do not emit substances that may damage human health or the environment. In fact, through the savings in conventional electricity production they can lead to significant emission reductions. There are, however, several indirect environmental impacts related to PV power systems that require attention.

The production of present PV power systems is relatively energy intensive, involves the use of large quantities of materials and smaller quantities of substances that are scarce and/or toxic. During operation, damaged modules or a fire may lead to the release of hazardous substances. Finally, at the end of their useful lifetime PV power systems have to be decommissioned, and resulting waste flows have to be managed.

Life-cycle approaches are needed to address the environmental impacts of PV power systems because these impacts originate mostly from manufacturing and end-of-life management. Environmental Life Cycle Assessment (LCA) is the appropriate tool at least for the assessment of energy related emissions. The calculation of Energy Payback Times and CO2 mitigation potentials can be seen as special forms of performing life-cycle assessments.

We were especially interested in calculating the Energy Payback Time (EPBT) and CO2 mitigation potential. These indicators are climate dependent, and therefore different for each country. Figures as low as 1 year EPBT are given for Thin Film technology systems, but what would happen if such systems were located in the UK? An Environmental Life Cycle Assessment was conducted using EBPT and CO2 emissions as environmental indicators in order to evaluate grid connected PV Systems in the UK.

Conclusions

From an environmental point of view, the use of PV as a replacement for fossil fuel-based electricity generation has environmental benefits in the UK, offering a significant potential for energy savings and CO2 mitigation. Although the energy payback time and the CO2 emissions for present-day systems are still relatively high, the EPBT is lower than their expected lifetime, ranging from 4 to 9 years. It is important, however, that manufacturers claim to be able to optimise PV module energy requirements, making possible a future decrease in the Energy Payback Time for grid-connected PV systems to around 2 years.

Very little data is available about recycling of PV system components. Under existing environmental regulations CdTe, CIS or crystalline Si modules may be classified as hazardous waste, needing a special disposal procedure, in some countries. The issue of the recycling of PV modules and other system components require attention. Recycling is very important for keeping LCA impacts low.