Integration of parabolic trough and linear Fresnel collectors for optimum design of concentrating solar thermal power plant

Abstract

A concentrating solar power (CSP) plant with parabolic trough collector (PTC) using thermal oil as heat transfer fluid (HTF) is the most commercially established technology. On the other hand, linear Fresnel reflectors (LFRs) with direct steam generation (DSG) are developed and proposed as cheaper alternative to PTC systems. The optical efficiency of LFR systems is lower than that of PTC systems. Also low-cost LFR systems produce saturated steam, resulting in higher aperture area requirement compared to PTC-based CSP plants of the same capacity. In this paper, integration of parabolic trough and linear Fresnel collectors for an optimum design of a CSP plant is proposed. The integrated CSP plant configuration combines the advantages of conventional HTF-based PTC fields and DSG of LFR fields. Thermo-economic comparisons between PTC-based, LFR-based and integrated CSP plant configurations, without hybridization and storage, are presented in this paper. An approximate, but simple selection methodology for these configurations, based on the values of relative collector field costs per unit of energy gain and relative isentropic efficiency of turbines, is also proposed to generate selection diagram. This diagram helps in selecting optimum configuration for the CSP plant. The applicability of the proposed methodology is demonstrated through an illustrative case study. Detailed simulations are advisable in case of design point close to separation lines between different regions in the selection diagram.