Page 229 - Materials Chemistry, Second Edition

218 R. Laleman et al.

net-energy loss when considering all the steps in the energy production chain. The
difference between NER and EPT is that, for a given technology, the NER score will
be more favorable if its lifetime is longer, while the EPT will remain the same.

2.6 Fossil Energy Requirement

The Fossil Energy Requirement provides a score for the ‘‘renewability’’ of a kWh
of produced electricity. Unlike the NER, it only contains the nonrenewable part of
the electricity. It is thus not equal to the inverse of the NER. The FER can be
calculated by dividing the total amount of nonrenewable energy required for
production (i.e., the nonrenewable part of the CED as defined in Sect. 2.3) by the
total lifetime energy production (LEO) of the PV system (Cherubini et al. 2009).
A low FER indicates that the electricity produced has a high ‘‘renewability’’ 3

ð5Þ
FER ¼ CED non ren = LEO kWh prim =kWh el
Cherubini et al. (2009) also mentions the Cumulative Energy Requirement
(CER), which contains both the renewable and the nonrenewable part;

CER ¼ FER þ RER kWh prim =kWh el ð6Þ
with CER = Cumulative Energy Requirement
FER = Fossil Energy Requirement
RER = Renewable Energy Requirement
The Renewable Energy Requirement (RER) is, according to Cherubini et al.,
2009, equal to 1 for most of the renewable energy sources, except for biomass.
Biomass electricity production has a high RER since a lot of (renewable) energy is
needed to produce biomass. By consequence, the CER for electricity from biomass
is very high, even higher than for fossil-fueled technologies. These high scores
could be misleading. We therefore chose to only mention the FER’s here.

3 LCA of a 3 kWp PV system

3.1 Introduction

Table 4 shows that the efficiency of a PV module varies substantially according to
the type of solar cell used, with the lowest efficiencies for amorf-Silicon-type cells
(a-Si; about 7 %) and the highest for monocrystalline Si solar cells (mono c-Si;
2
about 14 %). The column titled ‘‘active surface’’ shows how much m is needed to

3
Cherubini et al. (2009) uses MJ/MJe, however, we prefer to use kWh prim /kWh el.