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PARIS, France, September 6, 2006 (Refocus
Weekly)
Roof-top solar PV systems recover their energy
content (from manufacturing and recycling) within 1.6 to 3.3 years,
depending on location, concludes an assessment from the
International Energy Agency.
Although solar electricity is pollution-free, PV systems require
a certain amount of energy which must be ‘reimbursed’ before they
can be considered as renewable and clean, explains ‘Compared
assessment of selected environmental indicators of photovoltaic
electricity in OECD cities’ produced by IEA’s Photovoltaic Power
Systems Programme. The energy is needed to manufacture and install
PV systems and, later, dismantle and recycle them.
PV systems mounted on rooftops produce the amount of energy needed
to recover their energy content in the range of 1.6 to 3.3 years,
and generate (during their service life) between 17.9 and 8 times
their initial energy content. Once they have reimbursed their
initial energy input, rooftop PV systems can avoid the emission of
40 tons of CO2, depending on their location and on the local
electricity mix available.
The report was prepared to provide “clear and well-documented
answers to politicians, decision-makers and the general public about
what PV can and cannot achieve in terms of renewable, clean energy
production and environmental protection,” it explains.
The results for solar PV facades are slightly worse than for
roof-top PV systems since they generate less energy for the same
installed capacity. They produce the amount of energy to recover
their energy content within 2.7 to 4.7 years, and produce (during
their service life) between 10.1 and 5.4 times their initial energy
content.
The contribution of PV facades to CO2 emissions mitigation can be up
to 23 tons of CO2 per kWp installed.
The energy payback time (EPBT) and energy return factor (ERF) depend
on the location of the PV installation, and the performance of PV
systems is assessed on a country-by-country basis in the report, and
on a city-by-city approach in larger countries “where the potential
for urban-scale integrated PV is highest with a view to both better
reflect the varying reality and to facilitate the use of the results
at national and local levels.”
The global range for 41 cities in 26 OECD countries are examined,
and the data “clearly demonstrate how beneficial urban-scale PV
systems are for reducing the use of highly-polluting conventional
energy sources and for contributing to improving the general
efficiency of large cities wherever they are located worldwide.”
Country results can be used to “raise the awareness of politicians
and decision-makers at national level in order to accelerate the
development and the deployment of PV technologies in a given
country.”
The study examines only grid-connected PV-systems that are made of
mainstream
components available on the market (standard multi-crystalline
silicon modules and standard grid-tied inverters) and
architecturally integrated in buildings. The average lifetime of PV
modules is estimated at 30 years, although actual power production
from the modules is generally over 25 years while the inverter (the
“weakest part of a grid-connected PV system”) is ten years.
For rooftop PV systems, the EPBT range of 1.6 to 3.3 years, is best
in Perth, Australia and the worst in Edinburgh, UK. For PV façades,
the range of 2.7 to 4.7 years showed the best case in Perth and the
worst in Brussels, Belgium.
Rooftop PV systems are expected to produce between 8 and 17.9 times
the amount of energy needed for manufacture, installation and
dismantling, and the best case was against shown in Perth and the
worst in Edinburgh. For PV façades, the range of 5.4 to 10.1 times
the amount of energy was best in Perth and worst in Brussels.
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