Background
What is an Life Cycle Analysis (LCA)?
A Life Cycle Analysis (LCA) evaluates the environmental impacts of a product or process from production to disposal (Fthenakis et al., 2005). An LCA investigates the material and energy inputs required to produce and use a product, the emissions associated with its use, and the environmental impacts of disposal or recycling. The LCA may also investigate external costs such as environmental mitigation that is made necessary by the production or use of a product (Fthenakis and Alesma, 2006).
Brief History of Solar Power
Lifecycle Carbon Dioxide Emissions of Photovoltaics
Lifecycle carbon dioxide emissions refer to the emissions caused by the production, transportation, or installation of materials related to photovoltaic systems. In addition to the modules themselves, the typical installation includes electrical cable and a metal rack. Ground-mounted photovoltaic systems also include a concrete foundation. Remote installations may require additional infrastructure for transmission of electricity to the local electrical grid. In addition to materials, a life cycle analysis should include carbon dioxide emitted from vehicles during the transportation of photovoltaic modules between the factory, the warehouse, and the installation site. The graph below compares the relative contributions of these factors to the lifetime carbon dioxide impacts of five types of photovoltaic modules (Ito et al., 2007).
Production
The environmental impact of a silicon photovoltaic module involves the production of three main components: the frame, the module, and balance-of-system components such as the rack and inverter (Fthenakis and Alsema, 2006). Greenhouse gases are caused mostly by module production (81%), followed by the balance of system (12%) and frame (7%) (Fthenakis and Alsema, 2006).
Energy and Materials Usage
Transportation
Installation
Waste Generated
Air and Water Emissions
Comparison to Other Energy Sources
Total lifecycle emissoins associated with photovoltaic energy production are higher than those of nuclear power but lower than those of fossil fuel energy production. Lifecycle greenhouse gas emissions of several energy generation technologies are listed below: (Fthenakis and Alsema 2006).
- Silicon PV: 45 g/kWh
- Coal: 900 g/kWh
- Natural gas: 400-439 g/kWh
- Nuclear: 20-40 g/kWh
Conclusions
References
Life cycle assessment of photovoltaic electricity generation, A. Stoppato, Energy, Volume 33, Issue 2, February 2008, Pages 224-232