Page 235 - Materials Chemistry, Second Edition

224 R. Laleman et al.

An important conclusion than can be drawn from this is that using a weighted
multidimensional method, such as the Eco-Indicator, can lead to surprising results.
The advantage of providing an overall score that takes into account many types of
environmental impact and provides an elegant overview is unfortunately related to
the disadvantage of the subjectivity of the weighting step. One cannot have one (a
single overall score) without the other (some kind of weighting).

3.4.3 Mineral Extraction

Given the large impact that the individualist places on mineral extraction, it can be
interesting to have a closer look at this particular aspect of ‘‘sustainability’’ which
is rarely considered in the literature (Kato et al. 1997; Ito et al. 2003; Pehnt 2006;
Raugei et al. 2007a, b). Table 5 shows that the production of PV systems requires
a vast amount of minerals, even if most of the metals are assumed to be recycled
(ecoinvent report n°6). However, when compared to the weight of 3 a kWp PV
system, the results are not that surprising (Table 4). Removing the aluminum
frames can significantly reduce the CED—and by consequence the environmental
impact—of a solar panel (Alsema and Nieuwlaar 2000) but this is rarely done in
practice.

4 Literature Review

4.1 Energy Payback Time Review

The EPT has been a popular measure to estimate the environmental impact of PV
systems. The overview presented in Fig. 8 indicates that the data from the Eco-
invent database are in line with results found in the literature. Generally speaking,
2
the EPT is 4–5 years in a low-irradiation case (950 kWh/m /y) and 2–3 years in a
2
high irradiation case (1,700 kWh/m /y).

Table 5 Life-cycle crude ore extraction of iron, aluminum, and copper for a 3 kWp PV
installation (Ecoinvent v2.0) and total weight of a 3 kWp PV system (calculations based on
Ecoinvent report n°6)
Mineral Ore Mono c-Si Multi c-Si a-Si CdTe CIS Ribbon Si
Fe (kg) 103.23 106.50 189.13 112.94 77.43 77.22
Al (kg) 75.95 80.54 145.04 135.17 89.66 87.95
d
Cu (kg) 25.30 25.41 26.37 39.44 24.14 25.56
Weight of 3 kWp PV system (PV modules only)
Weight (kg) 311 333 379 804 496 364
d
Is the sum of all the Copper ore types available in Ecoinvent (v2.0)