Cleaner Products through Life Cycle Design (Amorphous Silicon Photovoltaics)
Photovoltaic modules (PV), devices that convert solar energy into electricity, are emerging as an important alternative to electricity generating systems based on nonrenewable fossil fuels. This life cycle design demonstration project was a collaborative effort between the National Pollution Prevention Center at the University of Michigan, the National Risk Management Research Laboratory of the U.S. Environmental Protection Agency, and United Solar Systems Corporation, a leading manufacturer of thin film amorphous silicon PV modules. The primary objective of this project was to develop and apply design metrics for assessing and guiding the improvement of PV product systems. The total PV life cycle, encompassing material production, manufacturing and assembly, use, and end of life management was investigated. Energy payback time, electricity production efficiency, life cycle conversion efficiency, and life cycle cost metrics were evaluated for modules located in Detroit, Boulder, and Phoenix, three sites with different insolation. The study also explored the energy savings associated with several strategies for design improvement, including frameless modules, frame reuse, and an alternative procedure for module encapsulation. Life cycle air emissions, waterborne effluents, and solid waste were not investigated due to a lack of available data.
The life cycle design framework offered many useful insights for enhancing the energy performance of photovoltaic technology. Electricity production efficiency measures the sustainability of a system by comparing the amount of energy generated with the amount invested in a system over its entire life cycle. The United Solar UPM-880 module met the criterion of sustainability for most cases considered. Although the sustainability criterion was not met for some cases with low insolation, the energy performance of the UPM-880 exceeded the average efficiency of the national electrical grid for all cases considered. The aluminum frame was responsible for a significant fraction of the energy invested in the UPM-880 module and was the primary focus of efforts to improve the energy performance of this PV module. This document also contains process flow diagrams, material composition data, and detailed boundary conditions.