Sustainability Report - Bank Sarasin-Alpen

Solar Energy 2005
Assessing the sustainability of PV systems
It is frequently assumed that renewable energies must, a priori, be sustainable.
The manufacture of PV cells in particular is an energy-intensive process that
uses a lot of chemicals, and it is therefore worth taking a closer look at this issue.
EU project “Crystal Clear”
confirms PV systems’ short
energy payback times
An EU project conducted in this area under the name “Crystal Clear” 7 , which
runs to 2008, is currently examining the entire life cycle of the PV cell from the
silicon raw material to the finished PV module. The aim is to reduce the production
costs for solar modules by approximately 60%. The intention is also to try
and cut the energy payback time from the current 3-5 years to just two years.
Before this could happen, more up-to-date figures had to be collected, as all
studies on the subject of energy payback times of crystalline solar systems had
previously been based on a study published in 1992 by the Munich energy research
institute Forschungsstelle für Energiewirtschaft. This was in turn based
on German production lines using technology developed in the eighties.
Preliminary Crystal Clear results, which were presented in June at the 20th
European Photovoltaics Conference in Barcelona, show an improvement of
around 25% in energy payback times compared with five years ago. This is
mainly attributable to advances in the efficient use of the silicon raw material.
Further improvements are anticipated with the wafer thickness being reduced to
150 µm. The project examined solar modules with polycrystalline and monocrystalline
cells and modules with string ribbon cells. With the latter type of cell,
there is no sawing of the wafer, thereby resulting in highly efficient use of silicon,
which is a very energy-intensive material. The energy payback time for PV systems
in Central Europe (750 kWh/kW) is 2.6 to 4.4 years, and for Southern
Europe (1,275 kWh/kW) 1.5 to 2.5 years.
Fig. 15: Energy payback time for modern solar systems (preliminary results)
5
Southern Europe
Central Europe
4
3
Years
2
1
0
Ribbon/sheet Polycrystalline Monocrystalline
Source: EU Crystal Clear project, 2005
The environmental rating of photovoltaics is determined not only by the energy
payback time, but also by the disposal and recycling problem. The PV industry is
not directly affected by the new European environmental directives WEEE and
RoHS 8 . Even so, a preliminary warning needs to be sounded.
7
8
Project results can be found under: www.chem.uu.nl/nws/www/publica/E2005-32.pdf
www.bmu.de/elektrogesetz
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