Page 417 - A Comprehensive Guide to Solar Energy Systems

22

Life Cycle Analysis of Photovoltaics:

Strategic Technology Assessment

Vasilis M. Fthenakis
CENTER FOR LIFE CYCLE ANALYSIS, COLUMBIA UNIVERSITY,
NEW YORK, NY, UNITED STATES
fthenakis@bnl.gov

22.1 Introduction

Over the last 10 yr, the market for photovoltaics (PVs), as measured by their cumulative in-
stalled capacity, has been growing by about 45% per yr. Between 2005 and 2015, global solar-
PV capacity increased from about 5–220 GW, and it exceeded 350 GW as of the end of 2017 [1].
The fast growth of the PV markets is largely based on the promise to produce abun-
dant electricity at low cost to the environment. It is therefore important to monitor and
report indicators of the environmental performance of PV systems. Such indicators in-
clude the energy payback time (EPBT), the energy return on energy investment (EROI),
and the global warming potential (GWP). The framework for this type of evaluations is
life cycle assessment; it is also called life cycle analysis (LCA), accounting for material and
energy flows in all the stages of the system.
This chapter shows the current LCA status for the major currently commercial large-
PV technologies, namely: single-crystalline Si (sc-Si), multicrystalline Si (mc-Si), thin-film
cadmium telluride (CdTe), and copper indium gallium diselenide (CIGS). Within this vari-
ety of technologies, Si-wafer based technologies account for approximately 92% of the to-
tal production, while CdTe PV technology represents the largest contributor to nonsilicon
based PV systems. As efficiencies and material and energy usage in PV modules is continu-
ously increasing, an up-to-date estimate and reasonable projections of the energy and en-
vironmental performance of PV technologies are of key importance for long-term energy
strategy decisions. This chapter also presents a prospective LCA accounting for potential
improvements in silicon PV technologies, which account for most of the market and have
higher environmental footprint than thin-film technologies.

22.2 Life Cycle Analysis Methodology

LCA is a comprehensive framework for quantifying the environmental impacts caused
by material and energy flows in each and all the stages of the life cycle of a product or
an activity. It describes all the life stages, from “cradle to grave”, thus from raw materials
A Comprehensive Guide to Solar Energy Systems. http://dx.doi.org/10.1016/B978-0-12-811479-7.00022-1 427
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