Life‐cycle assessment of photovoltaic modules: Comparison of mc‐Si, InGaP and InGaP/mc‐Si solar modules

Abstract

A higher conversion efficiency of photovoltaic modules does not automatically imply a lower environmental impact, when the life-cycle of modules is taken into account. An environmental comparison is carried out between the production and use phase, except maintenance, of an indium-gallium-phosphide (InGaP) on multicrystalline silicon (mc-Si) tandem module, a thin-film InGaP cell module and a mc-Si module. The evaluation of the InGaP systems was made for a very limited industrial production scale. Assuming a fourfold reuse of the GaAs substrates in the production of the thin-film InGaP (half) modules, the environmental impacts of the tandem module and of the thin-film InGaP module are estimated to be respectively 50 and 80% higher than the environmental impact of the mc-Si module. The energy payback times of the tandem module, the thin-film InGaP module and the mc-Si module are estimated to be respectively 5Á3, 6Á3 and 3Á5 years. There are several ways to improve the life-cycle environmental performance of thin-film InGaP cells, including improved materials efficiency in production and reuse of the GaAs wafer and higher energy efficiency of the metalorganic chemical vapour deposition process.

Emissions from Photovoltaic Life Cycles

“…In those days, manufacturing of solar cells was for the most part using off-spec products of electronic-grade silicon and various allocation rules were applied to the energy and material inputs for each grade of silicon; also solar cells were much thicker than the current ones (1). Meijer et al evaluated 270-µm-thick Si PV with 14.5% cell efficiency fabricated from electronic-grade high-purity silicon (2). They estimated energy payback time (EPBT, the time it takes for a photovoltaic (PV) system to generate an amount of energy equal to that used in its production) for the module only of 3.5 years for the low level of insolation in The Netherlands (1000 kWh/m 2 /yr).…”

Energy payback time of the high-concentration PV system FLATCON®

“…9 Little is known about the EPBT of III-V solar cells due to the fact that their only present application is in space. Nevertheless, the EPBT of a mechanically stacked InGaP/mc-Si tandem-module has been calculated 10 to be approximately 5 yr. For solar thermal collectors an EPBT was published 11 in the range of 1-2 yr. It is important to bear in mind that these publications are based on different assumptions.…”

“…Therefore, according to other authors 8,10,12 electrical input or output energy of the system is multiplied by an 'electrical conversion factor' in order to get the primary energy equivalent. This factor depends on the country supplying the electric energy.…”

The potential of III‐V semiconductors as terrestrial photovoltaic devices

“…These studies have been extensively performed for Si, but only a few articles deal with III-V material. 79,80 Regarding the precursors used for MOVPE deposition of III-V cells (and in general for electronic devices) it is difficult to find studies about their abundance on Earth. Authors are aware of reports which study the abundance of Gallium, 81 Indium, Germanium, Arsenic, 82 but in some cases they are restricted only to domestic US availability.…”