Heliostat field layout methodology in central receiver systems based on efficiency-related distribution

• A model for exact calculation of the mean annual optical efficiency is presented.
• A methodology and related code for heliostat filed layout have been developed.
• There will be no serious decline in the individual heliostat’s efficiency.
• AEED-based field improves PS10 field by 0.57% in the mean annual efficiency.
• ECRD-based field substantially reduced the land area.

This paper deals with a methodology for heliostat field layout. The methodology, described and validated herein, includes a detailed calculation model for the heliostat field’s mean annual optical efficiency covering the factors of cosine efficiency, shading and blocking efficiency, mirror reflectivity, atmospheric attenuation and receiver interception efficiency. Certain measures are taken to reduce the time consumption for the calculation of the shading and blocking efficiency. On the basis of the performance calculation model the field generation methodology, in which the heliostat field is generated by means of adding the heliostats to the field in sequence, is proposed. This new methodology does not yet perform a grand optimization and it currently depends on the running of other codes to determine optimum tower height and receiver dimensions. In this described methodology, the annually equivalent efficiency distribution (AEED), in pursuit of the maximization of the field’s efficiency, is first proposed and calculated as the basis of positioning the heliostats. Not only the shadowing and blocking effects of the existing heliostats, but also the effects of the heliostats added to the existing heliostats are considered in AEED. The newly added heliostat should be positioned on the best position of the updated AEED so that the average efficiency of the existent heliostats including that new heliostat reaches a maximum. The PS10 field is rearranged by using the AEED-based method and the result shows that the rearranged field improves the original PS10 field by 0.57% in the mean annual optical efficiency and 1.19% in the insolation unweighted efficiency. Furthermore, on the basis of the above method, the cost is taken into account and the efficiency/cost ratio distribution (ECRD) is then used for field generation. The rearrangement result suggests that ECRD-based field has substantially reduced the land area of AEED-based field and shown a good performance in the levelized energy cost.