Solar Thermal Systems – Year - Round Heating from the Sun - Renewable Energy and Climate Change - page 117

Figure 6.1 Modern solar thermal collector systems are an important alternative to conventional oil and
natural gas heating. Photos: www.wagner-solar.com.
It was not until the oil crisis in the 1970s that solar thermal power was rediscovered.
In the years that followed there were still many teething problems, and not all
systems ran smoothly. Today a variety of solar thermal system variants are avail-
able, and these systems are much more sophisticated than in the past (Figure 6.1).
In combination with optimized heat insulation and other renewable heating systems,
such as biomass heating and renewably operated heat pumps, these systems can
make an important contribution towards the supply of carbon-free heat.
Solar Collectors, Solar Absorbers, Solar Cells or Solar Modules
- What Next?
These terms are often used interchangeably, so to avoid confusion it's impor-
tant to be clear about what exactly they refer to.
A sun collector or solar collector is used to extract heat from the radiation of the sun.
Thus, a collector always makes something hot. At the heart of a solar collector is a solar
absorber . The solar absorber absorbs the radiation of the sun and converts it into heat.
Solar collectors are used to heat domestic water supply, supplement room heating and
produce high-temperature process heat. Thermal power plants can even generate electric-
ity from high-temperature heat (see Chapter 7). However, even then solar collectors are
fi rst used to produce the heat.
A solar cell is a photovoltaic cell that converts solar radiation directly into electric energy
(see Chapter 5). Although a solar cell can also get hot, it is different from a solar col-
lector in the sense that this is an undesired side effect. The heat actually reduces effi -
ciency during the production of electricity. A solar module consists of a large number
of solar cells and also generates electric energy from sunlight.