Life Cycle Assessment (LCA) is a structured, comprehensive method of quantifying material- and energy-flows and their associated emissions caused in the life cycle 1 of goods and services. The ISO 14040 and 14044 standards provide the framework for LCA. However, this framework leaves the individual practitioner with a range of choices that can affect the results and thus the conclusions of an LCA study. The present version of the IEA LCA guidelines is the result of the third update. They were developed and are updated to provide guidance on assuring consistency, balance, and quality to enhance the credibility and reliability of the results from LCAs on photovoltaic (PV) electricity generation systems. The guidelines represent a consensus among the authors—PV LCA experts in North America, Europe, Asia and Australia— for assumptions made on PV performance, decisions on process input and emissions allocation, methods of analysis, and reporting of the results.
Guidance is given on PV-specific parameters used as inputs in LCA and on choices and assumptions in life cycle inventory (LCI) analysis and on implementation of modeling approaches. A consistent approach towards system modeling, the functional unit, the system boundaries, water use modeling and the allocation aspects enhances the credibility of PV electricity LCA studies and enables balanced LCA-based comparisons of different electricity producing technologies. The current guidelines cover electricity production with ground mounted, building attached as well as building integrated PV systems. They are intended to be applied on assessing commercially deployed PV technologies.
The document discusses metrics like greenhouse gas emissions (GHG), cumulative energy demand (CED), use of mineral and metal resources, particulate matter, acidification and water use. Guidance is given for the definition of the energy payback time (EPBT), the non-renewable energy payback time (NREPBT), and the environmental impact mitigation potentials (IMP). The indicator energy return on investment (EROI) is described in a separate IEA report (Raugei et al. 2015). The interpretation of results should account for the fact that the environmental impacts may be significantly influenced by parameters that depend on the geographical zone and panel orientation as well as by a system’s boundary conditions and the modelling approach.
Transparency in reporting is therefore of the utmost importance. Following the guidelines in the chapter on the reporting and communication of the results serves the need for producing clear, comprehensive and transparent reports. At a minimum, the following parameters shall be reported in captions of result figures and tables:
1) PV technology (single and multi-crystalline silicon, CdTe, CIS, micromorphoussilicon);
2) Type of system (e.g., roof-top, ground mount, fixed tilt or tracker);
3) Module-rated efficiency and degradation rate;
4) Lifetime of PV and BOS;
5) Location of installation;
6) Annual irradiation, and expected annual electricity production with the given orientation and inclination or system’s performance ratio.
Further important information that should be documented in the LCA report are: the time-frame of data; the life cycle stages included; the lace/country/region of production (manufacturing components) modeled; the explicit goal of the study including technical and modeling assumptions and the name of the entity commissioning the study; the LCA approach used if not process-based; the LCA software tool (e.g., Simapro, GaBi, other); the LCI database(s) (e.g., UVEK LCI data DQRv2:2018, ecoinvent, GaBi, ELCD, Franklin, US LCI, IDEA) and impact category indicators used, always including the version numbers; the general information and assumptions related to the production of major input materials (e.g., solar grade silicon, aluminium (primary and/or secondary production)); and electricity source if known.