Solar process heat collector development

For applications requiring temperatures up to 250 °C, there is limited experience and suitable collectors are still needed. Therefore, for these applications, the development of high-performance solar collectors and system components is necessary. 

The aim of the solar thermal collector development is to improve and optimize them for the temperature level from 80 °C to 250 °C. There are different approaches like double-glazed flat plate collectors with anti-reflection coated glazing, stationary compound parabolic concentrator (CPC) collectors, evacuated tube collectors, vacuum flat plate collectors, small parabolic trough collectors, linear concentrating Fresnel collectors and a concentrating collector with a stationary reflector. 

Beside the minimization of collector losses at higher temperatures, the investigation of materials suitable for medium temperature collectors is important, and therefore appropriate durability tests are applied to specific materials and components to allow the prediction of service lifetime and to generate proposals for international standards. 

The collector efficiency curve is a good indication for the performance of a collector at different operating temperatures. Optical and thermal losses influence the efficiency of a collector. Thermal losses depend on the temperature at which the solar thermal collector is operating. Simple constructed collectors like an unglazed swimming pool collector have high losses already at relatively low temperatures. Process heat collectors have special 

In the following, an overview of some collector types is given  

---