Environmental Engineering Reference
In-Depth Information
6.1 Structure and Functionality
Solar thermal energy is a technology for converting solar radiation into heat. The
fi eld of application for this technology is extensive. The higher the temperatures are
required to be, the more complicated the technical implementation. The principle is
similar with all solar thermal systems. A solar collector fi rst collects the sunlight.
The term collector comes from the Latin word 'collegere', which means to collect.
The main component of a collector is the solar absorber. It absorbs the sunlight and
converts it into heat (Figure 6.2). It then transfers this heat to a heat transfer medium.
Figure 6.2
Processes in a solar fl at-plate collector.
The heat transfer medium may simply be something like water, air or even oil or
salt. Heat loss is unavoidable during the conversion. Part of the solar radiation is
refl ected and does not even reach the absorber. A certain amount of heat is lost
before it can be transferred to the heat transfer medium. The trick is to construct a
collector so that heat loss is as low as possible but the collector is still cost-effective
to produce. Appropriate collectors should be used depending on the fi eld of applica-
tion and desired temperatures.
The effi ciency curve describes the performance of a collector. Research institutes
measure collectors under strictly defi ned conditions to determine the curve. These
characteristic curves can then be obtained from the manufacturer of the collector or
over the Internet.
■
http://www.spf.ch/spf.php?lang=en SPF Collector Test Reports
■
http://www.itw.uni-stuttgart.de
ITW Kollektor-Testberichte (in German)
