Page 246 - Materials Chemistry, Second Edition

Comparing Various Indicators for the LCA 235

6 Conclusions and Discussion

In this chapter, the environmental impact of residential 3 kWp PV systems is
evaluated using various life-cycle impact assessment methods (LCIA methods). In
general, the results indicate that, relative to fossil-based energy sources, PV sys-
tems have a lower environmental impact, even in regions with a low solar irra-
diation, and even if only lifetimes of 20 years are assumed. However, when
compared to other renewables, the results are not that promising. Wind technol-
ogy, for example, seems to have an impact that is significantly lower. Biomass has
an impact that is on average similar, although one must keep in mind that the
sustainability of biomass is still a heavily debated topic.
The energy payback time (EPT) of residential PV systems is less than 5 years in
regions with a low solar irradiation, such as Belgium and the United Kingdom and
about 2–3 years in regions with a high irradiation (such as the South of Europe and
central/south U.S.). As most authors consider lifetimes of PV systems to be at least
20 years, we can conclude that they are indeed a renewable source of electricity,
since more energy is produced than consumed. The lifetime energy production is
roughly 5 times higher than the lifetime energy consumption in region with little
sun. This could rise up to 12 times in sunny regions. Other energy efficiency
indicators such as the Fossil Energy Requirement (FER) confirm that PV tech-
nology is indeed a renewable technology, with FER’s lower than 1 in even the
most pessimistic case.
Since minimizing global warming is a frequently mentioned reason for gov-
ernments to stimulate the use of PV systems, the Global Warming Potential
(GWP) of PV was estimated and compared with other energy technologies. We
found that the GWP of 1 kWh of PV electricity is on average much lower than that
of fossil power plants, similar to biomass, but higher than wind or hydro plants.
The EI 99 method with three perspectives offers a much broader perspective
when compared to one-dimensional indicators. However, the EI 99 results differ
greatly depending on the used perspective. The Individualist view, that considers
fossil fuels to be unlimited and only looks at the short term effects, puts a high
weight on the amount of mineral extraction that comes with PV production.
According to the Individualist, gas fired power plants are a better option for
electricity production than PV systems. The Hierarchist and Egalitarian views,
however, do consider the use of fossil fuels to have a negative impact on the well-
being of future generations. According to these latter perspectives, PV systems are
a better option than gas or coal fired plants.
It is important to stress that the results obtained by the EI’99 method can be
misleading, since it involves a weighting step that can be considered quite arbi-
trary. One can argue that the very high weight that the Individualist gives to
mineral extraction is far from what most people would consider logical or rational.
It does, however, point out aspects that a one-dimensional indicator does not. The
EI 99 method showed us that other aspects then GHG emissions and energy