Using all sky imager to control the solar field of a parabolic trough power plant – Implementation steps for commercial application.

Parabolic trough power plants are complex hydraulic and thermal systems that use parabolic mirrors to heat a fluid for energy generation. The solar field is divided into several loops through which the fluid flows and is heated. A loop can be more than 600 m long [3] and consists of parabolic mirrors that focus the sun's radiation onto an absorber tube. To achieve the desired outlet temperature, the amount of fluid brought into the solar field can be controlled. The fluid is distributed in the solar field in such a way that approximately the same amount flows through each loop. In case of homogeneously distributed irradiation, e.g. under clear sky conditions, the control with the mass flow works well. Problems may occur in transient conditions such as cloud passing. In this case, shaded loops can receive too much mass flow and the fluid cools down, or loops that are not shaded by a cloud can receive insufficient mass flow and overheat in the process. As an emergency function, the parabolic mirrors are moved out of focus to prevent damage in the event of high temperatures. In order to be able to react better in such situations, a system was developed that provides a better overview of the irradiation in the solar field. A camera system with an all sky imager (ASI) takes pictures of the sky and the software creates spatially resolved irradiation maps. This information can be used in different ways. This paper presents different implementation depths for parabolic trough power plants. The implementation levels range from the ASI system as stand-alone system up to a fully integrated automatic control of the solar field. For each implementation level, the benefits of the provided information are shown and an overview on the implementation for the operator effort is provided. [ABSTRACT FROM AUTHOR]