QUASI-DYNAMIC ANALYSIS OF THERMAL PERFORMANCE OF PARABOLIC TROUGH COLLECTORS

Kurzfassung

Thermal performance testing of parabolic trough collectors and collector loops plays an important role in prototype testing, collector certification and solar field commissioning. When testing for thermal performance, power output is calculated from measurements of mass flow, heat capacity and temperature difference between in- and outlet of the collector row. Testing conditions such as ambient temperature, irradiance and wind velocity are recorded. For the application of the commonly used steady-state testing analysis fluctuations especially in inlet temperature, irradiance and mass flow rate must be kept within a very small range. This restricts suitable testing periods when testing needs to be carried out outdoors and at commercial installations. Accepting wider ranges of data fluctuations the quasi-dynamic testing method is the preferred approach for obtaining a power output characterization. The underlying quasi-dynamic model as well as the data analysis based on deriving model parameters from preprocessed test data by means of multiple linear regression are described and discussed in this paper. Results are presented and compared to those obtained by steady-state analysis. Tests of a process heat collector carried out at DLR in Cologne serve as data base for this investigation.