Page 230 - Materials Chemistry, Second Edition

Comparing Various Indicators for the LCA 219
Table 4 Properties of the PV systems that will be investigated in this chapter
Cell Cell eff a Module Module Active surface a Active surface b Weight a
a
2
b
2
2
type (%) eff (%) eff (%) (m /kWp) (m /kWp) (kg/m )
Mono 15.3 14.0 14 7.1 7 14.6
c-Si
Multi c- 14.4 13.2 13 7.6 8 14.6
Si
Ribbon 13.1 12.0 11 8.3 9 14.6
Si
a-Si 6.5 6.5 7 15.4 14 8.2
CIS 10.7 10.7 10 9.4 10 17.6
CdTe 7.6 7.1 10 14.1 10 19.0
a b
Ecoinvent report n°6; Raugei and Frankl (2009)
obtain a PV system of one kWp. It is not surprising that higher efficiencies result in
2
a lower active surface (m /kWp). This is important because households are gen-
erally restrained by the surface of their roofs to install a residential PV system.
The data found in the Ecoinvent (v 2.0) report about PV systems (report n°6)
are very similar to more recently published data by Raugei and Frankl (2009),
except for CdTe type systems, which have a considerably lower efficiency
according to the Ecoinvent report. In this paper, the Ecoinvent ‘‘module effi-
ciency’’ will be used. Up until now, thin film type solar systems such as CdTe, a-Si
and CIS modules have been more commonly used for large scale PV systems. Thin
film PV systems only had a market share of 10–15 % in 2008 (International
Energy Agency 2010), they are thus not the main focus of this chapter. However,
in the future, these thin film types are likely to become more important and gain
market share as their per kWp costs decrease (EPIA 2010)
To conduct our analysis, we made the following assumptions: the residential PV
systems are not integrated but installed on top of slanted roofs; a standard 3 kWp
installation is considered; the conversion coefficient (C) is 0.35MJ el /MJ prim and the
output ratio remains constant (module efficiency loss over time is not incorporated).
In the literature review, however, also large scale installations are evaluated. 4

3.2 Energy Indicators

3.2.1 Cumulative Energy Demand

The results of a CED analysis based on the Ecoinvent database for the different
types of slanted roof, nonintegrated, residential PV systems are presented in Fig. 3.
2
The CED is normally presented as a ratio: CED/kWp (MJ-eq/kWp) or CED/m

4
The environmental impact per kWp for large scale systems is generally slightly lower
compared to small scale systems due to economies of scale.