Optical Performance of a Novel Two-Receiver Solar Central Tower System

A novel idea of using two receivers on the same tower in a solar tower system is introduced and investigated. The idea is to have two receivers at the same tower at different heights and sharing the same heliostat field. The pointing strategy for each heliostat is to pick the receiver that gives the maximum optical efficiency. To investigate this idea, two receivers are placed on the tower, one at the top and one at the midway up the tower. The biomimetic "spiral" distribution scheme is used to design the heliostat field, and the particle swarm optimization (PSO) method is used to obtain the optimum field shape factors. The model equations for calculating the optical field efficiency are presented and coded using the MATLAB software. The code is validated against known cases. To quantify the effect of the idea introduced in this paper, a solar field for the 50 MWth solar tower system with a single receiver is designed for Ma'an, Jordan (Ma'an enjoys high values of direct normal irradiance). It is found that the annual weighted optical efficiency for the 50 MWth plant in Ma'an for a single receiver is 67.14%, while it reaches 67.64% using the two-receiver system. Furthermore, the study shows that having two receivers on the same tower could save two heliostats and 11,000 m(2) of needed land area to obtain the same power as a single-receiver tower. The economic analysis for this 50 MWth plant shows that savings can be obtained from having an extra receiver on the same tower of the same quality as the main receiver when the specific land area exceeds 65 $/m(2).