Preliminary Hazard Analysis and Fault Handling Methods in Solar Thermal Power Plant Control Systems

Kurzfassung

Solar tower systems are a promising technology to provide sustainable and storable energy. However, many facilities report problems with the control systems during operation or during the commissioning phase. The problems include minor delays or even severe physical damages to the facilities. Because the technology just recently reached the Commercial markets, there exists not a lot of operating experience. This thesis provides an extensive risk and hazard analysis regarding the safety of Heliostat control systems for solar tower power plants. Potential risks and hazards are analysed, discussed and ranked by their severity, detectability and likelihood of occurrence. Fault injection methods are applied to examine the effects of given failures on the HeliOS control system. The most signifcant risks are identifed and four countermeasures are shown that aim to reduce the danger of that risks. Furthermore, parts of the actual implementation of the countermeasures within the HeliOS source code are shown and explained. The countermeasures include: Algorithms to more precisely calibrate the heliostat movement. Methods to avoid uncontrolled solar radiation in forbidden regions. Safety features that check the integrity of critical variables. And last but not least, the defnition of safety demands that clearly defne how a subsystem should react accordingly to the arrival of errors. The previously defned fault injection tests are repeated to test the effectiveness of the implemented countermeasures. The hazard analysis is re-evaluated to show the improvements that the countermeasures provide to the safety of the control system.