For solar thermal plants, it is much harder to make this evaluation, since a number of upstream and downstream components need to be taken into account to be able to determine the efficiency level of a plant. In practice, thermal energy storage devices, control systems and the actual consumption influence the effectiveness of the plants’ heat generation. Similarly, key parameters, such as the stored conventional thermal energy or solar efficiency, are dependent upon the location, system and use of the plant. Therefore, it is not possible to make a comparison.

This was what Stuttgart and Kassel universities set out to explore in their research project aimed at developing an independent benchmark criterion for evaluating the efficiency and controlling the functions of solar thermal plants. Together with a series of solar thermal and control system manufacturers, the performance indicators of the plants are being investigated, which operators, engineers and users will later be able to select. The results will be published as a code of practice. Based on the available measurement and control technology in existing plants, determining independent performance parameters will not require any large-scale investment on the part of users and operators. Instead, due to automatic controls in future, users will be able to monitor the plant’s performance in relation to the figures that can theoretically be expected and, if necessary, carry out efficiency-raising measures.

The project will receive €675,000 in funding from the Federal Ministry for Economic Affairs and Energy between 2016 and 2020. In addition to the aforementioned universities, seven German companies are also involved in the project, including suppliers of solar thermal plants and measurement and control systems, and companies specialising in heat contracting.