Environmental Engineering Reference
In-Depth Information
China is by far the world's largest solar water heater manufacturer and
user (see also the section on 'Use of renewable energy sources for heat and fuel
protection'). By the end of 2002 the accumulated installed area of solar
domestic hot water systems in China was about 40 million m
2
. The annual
production and sales volume was expected to reach about 8 million m
2
in
2002. There are more than one thousand manufacturers producing and selling
solar thermal systems, realizing a total turnover of more than one billion
Euros. Evacuated tube collectors dominate the Chinese market and exports. In
Europe about 1.1 million m
2
had been installed by 2002. Here the flat-plate
collector dominates. About half the new installations have been realized in
Germany. Chapter 3 describes solar collectors for domestic water heating in
detail.
Besides collector systems that use solar energy actively, so-called
passive
use of solar energy is possible. Well-oriented buildings with intelligently
designed glass facades or transparent insulation are used for this purpose. With
the combination of active and passive use of solar energy, it is also possible to
build zero-energy houses, especially in moderate climatic zones such as Central
Europe. The entire energy demand of these buildings is covered by solar energy.
Some prototypes, for instance the energy self-sufficient solar house in Freiburg
(Germany), have proven the high potential of solar energy use (Voss et al,
1995).
Photovoltaics
Another technology for using solar energy to generate
electricity is photovoltaics. Solar cells convert the sunlight directly into
electrical energy. The potential for photovoltaic systems is huge. Even in
countries with relatively low annual solar irradiance such as Germany,
photovoltaics theoretically could provide more than the total electricity
demand. However, an electricity supply based entirely on photovoltaic systems
is not feasible since it would generate a high surplus of energy in the summer
that would have to be stored at considerable cost. The combination of
photovoltaic systems with other renewable energy generators such as wind
power, hydro power or biomass is preferable. This would allow the whole
electricity demand to be satisfied free of carbon dioxide emissions while
avoiding high storage capacities and cost (Quaschning, 2001). Chapter 4 deals
with photovoltaics in detail.
Indirect use of solar energy
Natural processes transform solar energy into other types of energy. Technical
energy converters can utilize these indirect solar energy sources. One example
for indirect types of solar energy is waterpower. Solar irradiation evaporates
water from the oceans. This water rains down at higher altitudes. Streams and
rivers collect this water and close the cycle at the estuaries. Hydro-electric
power stations can convert the stored kinetic and potential energy of the water
into electricity. Types of indirect solar energy are:
