Page 227 - Materials Chemistry, Second Edition

216 R. Laleman et al.

compare the results. Sustainability and intergenerational equity are complex con-
cepts and, by consequence, one should accept that sustainability assessments imply
complex trade-offs. It is therefore crucial to have a good understanding of the
assumptions and weighting methods incorporated in the EI 99 method.

2.2 Global Warming Potential

The Global Warming Potential (GWP) assessment method, developed by the
Intergovernmental Panel on Climate Change (IPCC 1997; IPCC 2001), is fre-
quently used in energy research to investigate the impact of a product or a service
on global warming (Bravi et al. 2007; Heller et al. 2004; Lechon et al. 2008; Mohr
et al. 2009). Three GWP methods have been developed, each for a different time
span (20, 100 and 500 y). In this study, the 100 y method was used. Using the 20y
or 500y time span has no significant impact on the overall results.

2.3 Cumulative Energy Demand

The Cumulative Energy Demand (CED) is a very popular LCIA method, espe-
cially in renewable energy technology research (Huijbregts et al. 2006; Jungbluth
et al. 2007a, b; Jungbluth et al. 2008a, b; Alsema 1998; Alsema 2000; Alsema and
Nieuwlaar 2000; Alsema and de Wild-Scholten 2005; De Wild-Scholten and Al-
sema 2006). The CED aims to quantify all the energy that is consumed (or wasted)
during the life cycle of a product. The CED is usually expressed in terms of
primary energy (MJ prim ). In Ecoinvent, a different unit is used, namely energy
equivalents (MJ-eq).

2.4 Energy Pay-back Time

The Energy Pay-back Time (EPT) is a frequently used parameter because of its
input–output format and its ease to interpret. The EPT is, however, not straight-
forward to calculate. The formulas used to calculate the EPT are briefly summa-
rized below (based on (Alsema 2000; Frischkneicht and Jungbluth 2007; Jungbluth
et al. 2007a, b; Pacca et al. 2007). The first step is to calculate the Yearly Energy
Output (YEO [kWh/year]) of the energy technology. There are two ways to do so.
One starting from the Output Ratio (OR);
:
YEO = OR Power ð1Þ
With OR = Output Ratio [kWh/kWp/year]