Investigations into the spiral distribution of the heliostat field in solar central tower system

Abstract

The parameters and techniques involved in designing the heliostat field layout of Central Tower (CT) systems using the spiral distribution and the PSO algorithms are further investigated. The impact of extending typical domains of the shape factors on the design of the solar field and its performance are investigated and documented. Simplifications to the typical optimization procedures to design a solar field are introduced and documented. The effect of these modifications on the annual weighted efficiency of the solar field, the land required for the solar field and the computational time is documented. To quantify the effect of the introduced changes on the performance of CT, a 50 MWth CT plant is designed in Ma’an-Jordan to serve as a benchmark case for comparison purposes. Results showed that extending the domains for the shape factors “a” and “b” did not only change the optimum value of “a” and “b” but it also improved the system weighted efficiency by 0.84% and reduced the required land area by 1.8% (about 7000 m2).Moreover, several efforts are carried out aiming at accelerating the optimization process by reducing the two variables optimization, as the case in typical spiral algorithm optimization using PSO, into a single variable optimization, thus, eliminating the need for PSO technique. For example, a correlation between the optimal values of the shape factors “a” and “b” in the spiral distribution algorithm is established. Results of this action showed that the changes in field characteristics are less than 1%. Finally, the effect of changing the angular position constant in the spiral field pattern (the constant related to the golden ratio) on the field performance is investigated, and, it is found that the system performance is very sensitive to this constant, however, improvement of field efficiency is achieved using different values for this constant.