Life cycle assessment of thin‐film GaAs and GaInP/GaAs solar modules

Abstract

This paper presents an environmental comparison based on life cycle assessment (LCA) of the production under average European circumstances and use in The Netherlands of modules based on two kinds of III-V solar cells in an early development stage: a thin-film gallium arsenide (GaAs) cell and a thin-film gallium-indium phosphide/gallium arsenide (GaInP/GaAs) tandem cell. A more general comparison of these modules with the common multicrystalline silicon (multi-Si) module is also included. The evaluation of the both III-V systems is made for a limited industrial production scale of 0Á1 MW p per year, compared to a scale of about 10 MW p per year for the multi-Si system. The here considered III-V cells allow for reuse of the GaAs wafers that are required for their production.The LCA indicates that the overall environmental impact of the production of the III-V modules is larger than the impact of the common multi-Si module production; per category their scores have the same order of magnitude. For the III-V systems the metal-organic vapour phase epitaxy (MOVPE) process is the main contributor to the primary energy consumption. The energy payback times of the thin-film GaAs and GaInP/GaAs modules are 5Á0 and 4Á6 years, respectively. For the multi-Si module an energy payback time of 4Á2 years is found. The results for the III-V modules have an uncertainty up to approximately 40%. The highly comparable results for the III-V systems and the multi-Si system indicate that from an environmental point of view there is a case for further development of both III-V systems.

Environmental impact of thin-film GaInP/GaAs and multicrystalline silicon solar modules produced with solar electricity

“…By means of an advanced epitaxial lift-off (ELO) technique, the solar cell is separated from the GaAs wafer (Schermer et al 2005); the technique is assumed to allow for 95% reuse of this wafer. A solar energy conversion efficiency of the thin-film GaInP/GaAs cell of 28.5% is considered (Mohr et al 2007). One kilowatt peak power corresponds to a GaInP/GaAs solar cell surface of 3.51 m 2 .…”

“…The thin-film GaInP/ GaAs module is based on a gallium-indium phosphide/ gallium arsenide (Ga x In 1− x P/GaAs; x = 0.51) tandem cell that has been developed at the Radboud University Nijmegen, The Netherlands. The manufacturing of the thin-film GaInP/GaAs module is described in detail by Mohr et al (2007). Figure 1a shows the production scheme of a thin-film GaInP/GaAs solar cell.…”

“…In scenario S, the following production steps have the highest contributions: the MOVPE reactor system with the gas scrubbing system (which are composed of stainless steel), the frame (which for a large part is based on aluminium and glass) and the cell growth process (caused by the electricity consumption The contribution analysis for global warming and for freshwater aquatic ecotoxicity shows that the impact scores of the cell growth process are strongly decreased when PV electricity instead of fossil electricity is used in this process. A further decrease can be achieved by improvement of the efficiency of the cell growth process and by reducing the electricity consumption in this process (Mohr et al 2007). …”

“…Excess arsine and phosphine are neutralised in a gas scrubbing system. The electricity consumption in the cell growth process is high: In terms of primary energy demand, the electricity consumption in the cell growth process involved covers two thirds of the energy demand in the GaInP/GaAs module production (Mohr et al 2007). Fulltime operation of the reactor system corresponds to an annual production capacity of approximately 0.1 MW p .…”

“…Most of the studies refer to PV systems based on silicon (Si) solar cells (Gürzenich et al 1999;Keoleian and Lewis 2003;Dones et al 2004;Gürzenich and Wagner 2004;Jungbluth 2005;Kannan et al 2006;Koroneos et al 2006a, b;Alsema and De WildScholten 2007). A wider variety of types of PV devices is available (Jäger-Waldau 2007), which may vary in their environmental benefit (Alsema 2000;Kato et al 2001;Meijer et al 2003;Fthenakis and Alsema 2006;Fthenakis and Kim 2007;Mohr et al 2007;Raugei et al 2007). The studies done so far have shown that the electricity consumption in the production process of a PV module determines a significant part of the environmental impacts of that production process because of the extensive use of fossil fuels in the energy production and the associated emissions.…”