Page 103 - Materials Chemistry, Second Edition

3.2 Energy Analysis 87

from the web site of IEA (www.iea.org). Thesestatisticsalsoprovide theexports and
imports, not classified by countries though.
Apart from the smaller countries that produce either a surplus or are dependent
on import, imports and exports are usually the same and together make up about
10% of the total amount of electricity produced in the country. The numbers
of OECD (world) of 2007 depict an overall electricity production of 10 000 TWh
including a startling high proportion of more than 85% of nuclear energy and fossil
energy sources (the same as in Europe). Apart from hydropower (13%), renewable
energies do not yet contribute significantly.
For the energy calculation in the context of LCI, the final electricity consumption
must be extrapolated to the primary energy needed to produce the usable electricity.
For this purpose, the mix of electricity production serves as the basis. The
efficiencies with regard to specific energy sources have to consider the average
operating state of the power plant (conversion losses), transmission and distribution
losses as well as the typical upstream processes like transportation of energy sources,
and so on. These processes are considered by good generic data bases or can be
deduced from the sub processes.
In the context of renewable energy contributing to the electricity mix, the primary
energy it is related to has to be defined (see Section 3.2.2). As for hydropower,
the primary energy is set equal to the potential energy of the water by using
an efficiency of 90% or 85%. For thermal processes, the corresponding average
efficiency is approximately 35%. The CED, for example, per kilowatt hour, is equal
to a weighted and averaged primary energy necessary for the supply of 1 kWh (see
Section 3.2.2).
In LCA the primary energy should be split into renewable/non-renewable and
fossil. This is necessary for the conducting an impact assessment later (see
Chapter 4), in particular for the calculation of the global warming potential – GWP.
High electricity consumption in countries with a high proportion of fossil primary
energy always implies a high GWP whereas hydropower and other renewable forms
of energy contribute far less.
The production of electricity does not only cause the emission of greenhouse
gases (mostly CO and CH ) but also other emissions that have other impacts
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on the environment (e.g. radioactive emissions and acid forming gases). For an
LCI, those data must be procured or extracted from a generic data base and then
be attributed to the unit processes. Apparently friendly types of production like
hydropower can have serious effects on natural ecological systems (dams and
artificial lakes), which are difficult to quantify (impact category land use). Obvious
damage occurs with the extraction of coal and lignite in surface mining (coal pits),
which relates to the same impact category. Transmission of electric current can also
have environmental impacts, for example, by the use of the isolation gas SF ,which
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is an extremely strong greenhouse gas that may be released to the atmosphere by
leakages. However, on the other hand it has to be assessed whether its use does not
save more energy and thus reduce more greenhouse gas emissions than caused
by SF .
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