Environmental Engineering Reference
In-Depth Information
protection. The collectors are mostly integrated into buildings and, consequently,
do not require any extra land. The materials used in solar thermal systems -
such as glass, copper and plastic - are for the most part just ordinary materials
commonly used in standard construction. Materials that are a problem for the
environment, such as PU-foam and PVC, are used in some solar collector systems,
but most manufacturers of collectors consciously avoid them as a matter of
principle.
Energy is needed to manufacture solar thermal systems. In Central Europe, it takes
between six months and two years before a solar thermal system delivers the same
amount of energy that was used in its production. This period is shorter in countries
with a lot of sunshine. Many manufacturers place a great deal of emphasis on
environmental protection and renewable energies during the production of thermal
solar systems. The zero-emissions Solvis factory in Braunschweig, Germany, is an
example.
Some attention needs to be paid to the size of electrical pumps in solar systems.
These pumps require electric energy to operate. However, this requirement for
auxiliary energy is usually smaller by many orders of magnitude than the energy
saved by a solar system. Photovoltaic systems can be used to enable the auxiliary
electric energy required by solar thermal systems to be covered directly by the sun.
Many solar thermal systems also use chemicals such as antifreeze or cooling agents.
Typical antifreeze products like Tyfocor L have a minimal effect on water quality,
and, therefore, are largely safe for the environment.
Special protective measures are required if ammonia is used for solar cooling in
absorption-refrigerating machines. Ammonia is toxic and dangerous to the environ-
ment. Ammonia that escapes can bind to water. Lithium-bromide is also harmful to
human health, but less so than ammonia.
6.7 Solar Thermal Markets
In terms of world markets for solar thermal collectors, one country puts all the rest
to shame: China. Around 93 million square metres of collectors were installed in
the country in 2006. These collectors deliver about 65.1 gigawatts of heat power.
The Chinese collector market comprises more than 60% of the entire world market
(Figure 6.22 ).
One of the main reasons for the booming solar market in China is the poor supply
of electricity and gas in rural regions. Seventy-fi ve percent of the 1.3 billion Chinese
live in the country. In these rural areas solar thermal energy is often one of the least
expensive alternatives for providing hot water, and sometimes the only one. With
its widespread use of solar thermal energy, China has developed into a market leader
in collector manufacturing. More than 1000 companies now produce and distribute
solar collectors in China. Around 150 000 people were employed in the solar thermal
energy (European Solar Industry Federation ESTIF, 2003) sector in the year 2000.
In contrast to many other countries, China specializes in highly effi cient vacuum-
