Characteristics of collectors

The collector efficiency indicates the ratio of the heat output generated by the collector to the solar radiation output. The efficiency depends on ambient conditions, type of use and operating parameters. Depending on the region, a lower collector efficiency can be compensated by a higher irradiation power and a higher ambient temperature.

The collector characteristic curve (efficiency characteristic curve) shows the efficiency as a function of a variable parameter (usually the difference between average collector temperature and ambient temperature). With the help of this characteristic curve, suitable applications for collectors can be determined.

Figure 10: Efficiency curves of different collector types (Source: Ingenieurbüro Junge; http://www.ing-büro-junge.de)