Greenhouse gas emissions associated with photovoltaic electricity from crystalline silicon modules under various energy supply options

Abstract

The direct and indirect emissions associated with photovoltaic (PV) electricity generation are evaluated, focussing on greenhouse gas (GHG) emissions related to crystalline silicon (c-Si) solar module production. Electricity supply technologies used in the entire PV production chain are found to be most influential. Emissions associated with only the electricity-input in the production of PV vary as much as 0-200 g CO 2 -eq per kWh electricity generated by PV. This wide range results because of specific supply technologies one may assume to provide the electricity-input in PV production, i.e., whether coal-, gas-, wind-, or PV-power facilities in the ''background'' provide the electricity supply for powering the entire PV production chain. The heat input in the entire PV production chain, for which mainly the combustion of natural gas is assumed, adds another $16 CO 2 -eq/kWh. The GHG emissions directly attributed to c-Si PV technology alone constitute only $1-2 g CO 2 -eq/kWh. The difference in scale indicates the relevance of reporting ''indirect'' emissions due to energy input in PV production separately from ''direct'' emissions particular to PV technology. In this article, we also demonstrate the utilization of ''direct'' and ''indirect'' shares of emissions for the calculation of GHG emissions in simplified world electricity-and PV-market development scenarios. Results underscore very large GHG mitigation realized by solar PV toward increasingly significant PV market shares.

A Feasibility Assessment of Photovoltaic Power Systems in Ireland; a Case Study for the Dublin Region

“…The carbon intensity of the electric grid supplying the PV production chain has been shown to significantly affect life cycle GHG emissions [40], with emissions ranging from 1 g CO 2 -eq per kWh electricity generated by PV when the manufacturing process is supplied by 100% renewable electricity, to 218 g CO 2 -eq per kWh when the manufacturing process is supplied by coal electricity. This range of GHG emissions is still significantly lower than the carbon intensity of the Irish national grid at 457 g CO 2 per kWh in 2014 [1].…”

Photovoltaic Conversion: Outlook at the Crossroads Between Technological Challenges and Eco-Strategic Issues

“…The silicon technologies release also GHG directly, with the primary sources being the raw material itself, the various fluoride compounds involved in the manufacturing process as well as the incineration of the plastic used to encapsulate the solar cells, one of the common processes in the recycling of plastic materials. According to the estimates, the emission is virtually negligible, about 0.16 g CO 2 -eq/kWh for the raw material, whereas the incineration of plastic would be a source of 1.1 g (Reich et al, 2011 The fluoride compounds remain the Achilles heel of silicon cells since they have an even higher Global Warming Potential (GWP). CO 2 , methane and the nitrogen oxides have GWPs of 1, 23 and 296.…”

“…The estimate of the GHG attributed to PV systems is an increasingly complex exercise since it includes criteria that are as diversified as the technology used, the choice of manufacturing processes and the type of energies consumed, the techniques for assembling the cells and units, the power generated, the transportation of raw materials and the finished product, the components required for the installation of the units (Balance Of System/BOS) as well as the recycling processes. The BOS will, in turn, depend on the applications, the dimensions, the orientations and, above all, the location selected (Krauter & Rüther, 2004;Stoppato, 2008;Fthenakis & Kim, 2011;Reich et al, 2011). A major distinction is acknowledged between indirect emissions, which concern the overall energy, electricity included, needed to manufacture the units, and the direct emissions, which concern all of the chemical compounds, raw materials included, that are involved in the manufacturing process and are a potential source of GHG (Reich et al, 2011).…”

“…It is essential to point out that the GHG emission estimates for PV systems are not absolute since they are subject to a certain number of constraints, particularly the quality of the information provided by the manufacturers involved throughout the life cycle. Thus, the estimates are subject to future revisions as are the EPBT and ERF calculations (Reich et al, 2011;Held & Ilg, 2011). With respect to the direct emissions of the silicon industry, three critical phases are identified: the development of metallurgical-grade silicon from silica, its transformation into solar-grade silicon and the development of a structure and framework in the form of panels.…”

“…The BOS will, in turn, depend on the applications, the dimensions, the orientations and, above all, the location selected (Krauter & Rüther, 2004;Stoppato, 2008;Fthenakis & Kim, 2011;Reich et al, 2011). A major distinction is acknowledged between indirect emissions, which concern the overall energy, electricity included, needed to manufacture the units, and the direct emissions, which concern all of the chemical compounds, raw materials included, that are involved in the manufacturing process and are a potential source of GHG (Reich et al, 2011). It is essential to point out that the GHG emission estimates for PV systems are not absolute since they are subject to a certain number of constraints, particularly the quality of the information provided by the manufacturers involved throughout the life cycle.…”