13 Photovoltaics in the Future Energy System
333
climate to be created; rather, it can be seen as an important policy risk for the further
development of the PV market.
13.3 Sustainability
Environmental aspects of photovoltaics and, more generally, sustainability issues,
form a very important subject for the further deployment of PV. These cover in
particular materials and resource questions, industrial production processes, water
usage, eco-friendly product design, land use, operation of PV systems, possible
hazards, energy payback time, CO 2 emissions and recycling of PV components.
PV is proposed as a clean energy technology with a high potential for reducing the
emissions of greenhouse gases. It is therefore also being called upon to contribute
to the decarbonization of the entire energy system. Great care needs to be taken
to ensure that this is actually the case: an independent confirmation of the results
obtained by the PV community is necessary.
Life cycle analysis (LCA) of PV systems is the science that provides quantitative results regarding key environmental indicators and possible critical issues. LCA
enables one to take into account the entire life cycle stages, from cradle to grave, in
measuring environmental and resource sustainability. In order to perform a meaningful LCA, Life cycle inventories (LCIs) are necessary and the availability of such data
is often the greatest barrier for conducting LCA. Different solar cell technologies
have different environmental characteristics, in particular regarding the chemical
processes and materials used, as well as concerning the energy used to produce the
PV modules. A complete description of PV LCA can be found in [24].
In industrial PV cell manufacturing, many processes are used that are common
to the semiconductor industry, such as processes for cleaning, purifying and doping
semiconductor materials. These processes employ hazardous substances such as
chemicals (e.g. hydrochloric acids, sulfuric acids, nitric acids, hydrogen fluorides)
as well as toxic elements and compounds (e.g. arsine, cadmium, gallium, lead, and
phosphine). These materials require special handling and operating standards to
prevent workplace hazards and exposure to toxics. Over the past decade, strong
efforts were undertaken to reduce the amount of materials used for solar cells and
modules and to reduce or avoid the use of critical processes. For silicon solar cells
for example, silicon material usage was greatly reduced by thinner wafers (see also
Fig. 1.5 in Chap. 1).
The dominant solar cell technology, crystalline silicon, requires an energy intense
process to gain metallurgical-grade and subsequently solar-grade silicon from quartz
sand (silicon dioxide). Depending on the energy mix (coal, nuclear, hydropower, or
other renewables) at the specific location of the silicon manufacturing plant, large
variations in the associated greenhouse gas emissions are “incorporated” into the
solar cell material.
The life-cycle of photovoltaics starts from the extraction of raw materials (cradle)
and ends with the disposal (grave) or recycling and recovery (cradle) of the PV
333
climate to be created; rather, it can be seen as an important policy risk for the further
development of the PV market.
13.3 Sustainability
Environmental aspects of photovoltaics and, more generally, sustainability issues,
form a very important subject for the further deployment of PV. These cover in
particular materials and resource questions, industrial production processes, water
usage, eco-friendly product design, land use, operation of PV systems, possible
hazards, energy payback time, CO 2 emissions and recycling of PV components.
PV is proposed as a clean energy technology with a high potential for reducing the
emissions of greenhouse gases. It is therefore also being called upon to contribute
to the decarbonization of the entire energy system. Great care needs to be taken
to ensure that this is actually the case: an independent confirmation of the results
obtained by the PV community is necessary.
Life cycle analysis (LCA) of PV systems is the science that provides quantitative results regarding key environmental indicators and possible critical issues. LCA
enables one to take into account the entire life cycle stages, from cradle to grave, in
measuring environmental and resource sustainability. In order to perform a meaningful LCA, Life cycle inventories (LCIs) are necessary and the availability of such data
is often the greatest barrier for conducting LCA. Different solar cell technologies
have different environmental characteristics, in particular regarding the chemical
processes and materials used, as well as concerning the energy used to produce the
PV modules. A complete description of PV LCA can be found in [24].
In industrial PV cell manufacturing, many processes are used that are common
to the semiconductor industry, such as processes for cleaning, purifying and doping
semiconductor materials. These processes employ hazardous substances such as
chemicals (e.g. hydrochloric acids, sulfuric acids, nitric acids, hydrogen fluorides)
as well as toxic elements and compounds (e.g. arsine, cadmium, gallium, lead, and
phosphine). These materials require special handling and operating standards to
prevent workplace hazards and exposure to toxics. Over the past decade, strong
efforts were undertaken to reduce the amount of materials used for solar cells and
modules and to reduce or avoid the use of critical processes. For silicon solar cells
for example, silicon material usage was greatly reduced by thinner wafers (see also
Fig. 1.5 in Chap. 1).
The dominant solar cell technology, crystalline silicon, requires an energy intense
process to gain metallurgical-grade and subsequently solar-grade silicon from quartz
sand (silicon dioxide). Depending on the energy mix (coal, nuclear, hydropower, or
other renewables) at the specific location of the silicon manufacturing plant, large
variations in the associated greenhouse gas emissions are “incorporated” into the
solar cell material.
The life-cycle of photovoltaics starts from the extraction of raw materials (cradle)
and ends with the disposal (grave) or recycling and recovery (cradle) of the PV