Page 241 - Materials Chemistry, Second Edition

230 R. Laleman et al.

between 2 and 20. This is equivalent to a FER of 0.5–0.05. These numbers indicate
a technology that is renewable, since the electricity produced (kWh el ) exceeds the
primary energy consumed (kWh prim ). The reason for these high-energy ratios is
that the report does not include the energy content of the fuel, which is somewhat
surprising, and results in the strange notion that the energy ratio of a fossil tech-
nology can be higher than one.
The above discussion illustrates the difficulties that arise when there is a lack of
general methodology and definitions. The need, thus, for a more uniform approach
seems clear. The approach followed by Cherubini et al. (2009) seems to be a good
way forward, in the authors’ opinion. By mentioning both the renewable
(Renewable Energy Requirement) and nonrenewable (Fossil Energy Requirement)
energy need, a more balanced view of the environmental impact of the technology
is provided. In general, the definition of an energy indicator should always be
stated clearly such that misinterpretations can be avoided; unfortunately, this is not
always the case.

5.3 Global Warming Potential of 1 kWh of electricity

5.3.1 GWP of 1 kWh of PV electricity

Figure 11 shows that both the estimated lifetime and the irradiation have a strong
impact on the global warming potential of a PV-produced kWh of electricity. A PV
system installed in Belgium (BE) with an estimated lifetime of only 20 years pro-
duces electricity with a GWP of 116 gCO 2 -eq per kWh. This is almost twice the
impact of a kWh produced in Switzerland (CH) with a PV system that has an expected
lifetime of 30 years (66 gCO 2 -eq). Under optimal conditions—a PV system installed
in Spain with a lifetime of 30 years—the GWP could be reduced to 44 gCO 2 -eq.
The bottom part of Fig. 11 shows that results from Ecoinvent data are similar to
the literature. However, one can still find authors claiming that GHG emissions
could be as high as 160 gCO 2 -eq per kWh. This seems to be very pessimistic and is
not in line with Ecoinvent data, nor with most of the literature. Overall, we can
safely conclude that the GHG emissions from a kWh of crystalline PV systems
produced electricity are likely to be in the range of 50–100 gCO 2 -eq/kWh, with the
lower end being valid for sunny regions like Spain and Italy, and the higher value
being valid for regions like Belgium, the United Kingdom, and Germany.

5.3.2 Global Warming Potential of 1 kWh of Electricity

In this section, the results for the GHG emissions of a residential PV system are
compared with results from various renewable and nonrenewable electricity pro-
duction technologies. The data in Table 7 show that, overall, the emissions from
PV systems are much lower than emissions from fossil-fueled electricity