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1. Energy supply from photovoltaic and solar thermal systems
Photovoltaic systems
Electricity generation from 2002 to 2010 corresponds to the annual statements of the transmission
grid operators under the Renewable Energy Sources Act. Up to the end of 2001, electricity
generation was calculated on the basis of the installed capacity at the beginning of
the year plus half the relevant year’s capacity increase, multiplied by a specific power yield.
The specific power yield was made available as an average figure for Germany by the Solar
Energy Association [26]. The capacity increase was halved to take account of the fact that
new installations can only make a pro rata contribution to electricity generation in the first
year.
Solar thermal systems
The heat supply quoted is calculated from the installed collector area and a mean annual
heat yield. In the case of hot-water supply installations this is 450 kWh/m 2 *a. In recent years
installations solely for hot-water generation have been joined by increasing numbers of solar
thermal installations for combined hot water supply and central heating support.
Because the generation potential of installations for central heating support cannot be fully exploited
in the summer months, a reduced heat yield of 300 kWh/m 2 *a is used for calculation
purposes here. A yield of 300 kWh/m 2 *a is also used for swimming pool absorber systems.
Because the gradual addition of new installations during the year means that the collector area
available during the year is smaller than the installed capacity at the end of the year, only half
the increase in area for the year is used when calculating the heat supply for that year.
A factor of 0.7 kW th /m² is used for converting the area in to capacity [131].
2. CO 2 equivalent and SO 2 equivalent
The “Kyoto gases” CO 2 , CH 4 , N 2 O, SF 6 , PFC and HFC, are important greenhouse gases which
are to be reduced under the Kyoto Protocol. The extent to which they contribute to the
greenhouse effect differs. To be able to compare the greenhouse effect of the individual
gases, they are each assigned a factor – the relative global warming potential (GWP) – which
serves as a measure of their greenhouse effect in terms of the reference substance CO 2 .
Global warming potential is specified in the unit “CO 2 equivalent” and is calculated by multiplying
the global warming potential by the mass of the gas in question. It states the quantity
of CO 2 that would have the same greenhouse effect as the gas in question over a period of
100 years.
In view of the poor data availability situation, only the greenhouse gases CO 2 , CH 4 and N 2 O
are taken into account.
ANNEx: METhODOLOGICAL NOTES
Renewable Energy Sources in Figures
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