ABSTRACT
The temperature level that can be achieved with non-concentrating solar thermal collectors is limited. At the most a level of approximately 200°C can be reached with high-end vacuum tube collectors. A further increase of temperatures beyond this level is technically hardly achievable. In addition, above 100°C the collector efficiency decreases significantly. However, looking at the required temperature levels in the market segments of process heat or electricity generation by thermal processes, far higher temperatures are needed. Such temperatures can only be generated by the concentration of sunlight.
