Environmental Engineering Reference
In-Depth Information
COP values are usually much lower than the ideal value. They are in the range
2.5-4 for electric heat pumps and between 1.2 and 2 for gas motor heat
pumps. Low COP values destroy the ecological benefits of heat pumps. If a
heat pump used for room heating (with a COP of 3) is driven by electrical
energy from conventional power stations with an average efficiency of 33 per
cent, the primary energy demand is the same as that of a condensing boiler
with an efficiency of nearly 100 per cent. Earlier heat pumps used CFCs as the
working medium, which had harmful effects on the ozone layer and the
climate. Today alternative working fluids exist.
If renewable energy resources provide the mechanical power, a heat pump
can produce useful heat that is climatically neutral. Therefore, the heat pump
could play a more important role in a future climatically sustainable energy
supply.
Wind energy
More than 100 years ago, wind power had a dominant role in
the energy supply of many countries. Technically advanced windmills ground
corn or pumped water. In the US thousands of Western Mills were used in
agriculture, but all these windmills were mechanical systems. Wind generators
providing electricity started to enter the market in the early 1980s in Denmark
and the US. In Germany wind power had an unexpected boom in the 1990s,
making Germany the largest wind power market in the world. In 2002, the
German wind power industry achieved a turnover of nearly
4 billion and
created more than 45,000 new jobs. Altogether, 15,797 wind generators with
a total capacity of 15,327 MW and an electricity generation potential of 30
TWh/year were installed in Germany by mid-2004 (Ender, 2004). This is
equivalent to nearly 6 per cent of Germany's electricity demand. If Germany
continues with the same growth rates as in the late 1990s, it will cover more
than 10 per cent of its electricity demand in a few years. More recently, Spain
started a similar exploration of its wind potential.
Although Germany only has limited areas suited for setting up wind farms,
the potential is considerable. Excluding conservation areas and allowing for
safe distances to settlements due to noise considerations, 53.5 GW could be
achieved from installations onshore. This capacity could produce 85 TWh/year,
15 per cent of the electricity demand. The German offshore potential is 23.6
GW, which could produce 79 TWh/year. The potential in other countries is even
higher. In the UK, wind power could produce well above 1000 TWh/year,
which is much more than the total British electricity demand. Also the US could
cover its entire electricity demand using wind power. Chapter 5 describes in
detail the use of wind power for electricity supply.
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G
LOBAL
U
SE OF
R
ENEWABLE
E
NERGY
S
OURCES
The contribution of renewable energy sources to the global primary energy
supply was 13.5 per cent in 2001 (IEA, 2003b). Biomass is the most important
renewable energy source today and has a share of 80 per cent among the
