Co-optimisation of the heliostat field and receiver for concentrated solar power plants

In a concentrated solar power (CSP) tower plant, it is essential to understand the performance of the subsystem formed by the heliostat field and the receiver, operated with an optimal aiming strategy that guarantees the safety and lifetime of the receiver while maximising performance. State-of-the-art studies optimise the heliostat field, aiming strategy and the receiver independently. However, the field and the receiver are interdependent and co-optimisation of the field-receiver subsystem is necessary to obtain the optimal configuration. Fast and accurate annual performance assessments of the subsystem are needed to calculate the annual energy output and the Levelised Cost of Energy (LCOE) of the full CSP system. In this study, a co-optimisation method is proposed based on coupled instantaneous optical, thermal and mechanical models integrated into a system-level model for annual simulation of full system and economics. The resulting system-model is then used for design optimisation based on a genetic algorithm. Several techniques are implemented to make this complex and computationally expensive problem tractable. The proposed method is used to optimise the design of two systems composed of a surround field and a liquid sodium-cooled cylindrical external receiver for first the annual performance and then the LCOE. The good behaviour of the method is confirmed by a sensitivity study. The LCOE-based optimisation leads to a less efficient system than the efficiency-based optimisation but a higher capacity factor. The methods presented are applicable to other CSP plant configurations, including state-of-art molten salt power tower plants.