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ANNEx: METhODOLOGICAL NOTES
Gas Relative greenhouse potential 1)
CO 2
Ch 4
98 Renewable Energy Sources in Figures
1
21
N 2 O 310
Gas Relative acidification potential
SO 2
NO x
Nh 3
1
0.696
1.88
The acidification potential of SO 2 , NO X , HF, HCl, H 2 S
and NH 3 is determined in a similar way to global
warming potential. It is expressed in the unit “SO 2
equivalent” and shows the quantity of SO 2 that has the
same acidifying effect.
In view of poor data availability, only the air pollutants
SO 2 and NO X are taken into account when calculating
the emissions avoided.
1) The calculations in this brochure use the IPCC figures from 1995 [56]. These are prescribed for greenhouse gas reporting
under the Framework Convention on Climate Change and under the Kyoto Protocol in accordance with the UNFCCC
Guidelines [34].
Global warming potential is based on a time horizon of 100 years, with CO as reference substance.
2
3. Calculating avoidance factors and avoided emissions for renewables­based
electricity generation
The emissions avoided by using renewables are calculated on the basis of the quantities of
electricity generated from renewables and on substitution and emission factors.
Substitution factors indicate the fossil fuels that are replaced by the renewable source in question.
Emission factors specify the quantity of greenhouse gases and air pollutants emitted per
kWh of fossil or renewable electricity. They are made up of direct emissions during electricity
generation and the emissions arising from the upstream chain. The upstream chain comprises
the pollutant emissions arising from the production of the generating installations and
from the production, refining and transport of the fossil and renewable energy sources. In
the case of combined heat-and-power generation, allocation is in accordance with the “Finnish
method” laid down in EU Directive 2004/8/EC.
The substitution factors used are based on the “Report on CO 2 reduction in the electricity sector
through the use of renewable energy sources in 2008 and 2009” (Gutachten zur CO 2 -Minderung
im Stromsektor durch den Einsatz erneuerbarer Energien im Jahr 2008 und 2009 (Klobasa
et al. [88]). An electricity market model was used to calculate the extent to which renewables
replace conventional energy sources, given the existing portfolio of power plants. To date, renewables
have not yet replaced the base load supplied by nuclear power plants, because the
latter have lower variable costs than lignite power plants.
Compared with previous years, the latest report (Klobasa et al. [88]) shows much lower replacement
of electricity from lignite power plants. The reasons lie partly in a changed generation
mix (less electricity generated from nuclear power), and partly in a revised method,
which now takes account of imports and exports of electricity. As a result, the calculated
greenhouse gas saving due to renewable energies in the years 2008 to 2010 is two to four
million t CO 2 equivalent lower than a calculation based on the substitution factors used in
earlier years.