Design Optimization of Linear Fresnel Reflector Systems

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

To keep global temperature rise within 1.5°C and meet global net zero targets, it has been suggested that the world needs around 6.7 GW of annual capacity additions from Concentrating Solar thermal Power (CSP) from 2020 to 2030. However, to realise this, improvements are needed to make the technology more cost efficient and attractive for investment. The Linear Fresnel Reflector (LFR) is an emerging CSP technology for power generation, yet needs to benefit from design improvements and cost reductions. This thesis aims to optimize the design parameters of an LFR to improve efficiencies and minimise energy costs. To begin with, optical and thermal models are developed and verified against existing baseline LFR systems. The research goes on to investigate how the optical and thermal models can be coupled together and solved simultaneously using optimization methods. Genetic Algorithm(GA) was selected after testing different optimization methods on a number of LFRdesigns. Simulations are carried out for performance and cost based objective functions: total theoretical efficiency and Levelized Cost of Electricity (LCOE), and five design variables are examined: mirror number, width and spacing; receiver height and operating temperature. The thesis further explores LFR systems usingthree different primary mirror types (flat, slightly curved and fully curved) and two alternative receiver temperature operating conditions (constant and variable).Three locations (Spain, China and Australia) are considered to evaluate how optimized LFR designs will change due to the region of installation. The maximum efficiencies for the alternative mirror configurations were found to be comparable,however the optimized design variables were significantly different. In comparison to using flat mirrors, an optimized LFR system using fully curved mirrors increased the total efficiency by 4.5% and reduced land area, mirror area and receiver height by 35%, 29% and 34%, respectively. The performance-based and cost-based designs were most sensitive to non-optimal values of receiver temperature andreceiver height, respectively. Changes in mirror spacing were the least sensitive.Optimized results showed that design variable changes from existing systems can drop the LCOE up to 23%; highlighting the importance of highly accurate optimization of the system design. Although, the optimized designs did not vary much between the case study locations, LCOE showed a clear difference. This suggests that the LOCE is largely dominated by the component costs and amount of direct radiation rather than location dependant solar irradiance profiles. Optimized LCOE ranged from 0.074 to 0.083 (USD/kWh), lower than currently reported values for CSP (0.108 USD/kWh). A sensitivity analysis on cost parameters showed that a 20% drop of mirror costs would drop current LCOE by 9.7%. The method presented in this study can be adapted by manufacturers and researchers to optimize mirror receiver layouts and operating conditions for other LFR configurations.
Date of AwardFeb 2023
Original languageEnglish
Awarding Institution
  • Coventry University
SupervisorJonathan Nixon (Supervisor), Mauro Innocente (Supervisor) & Janis Priede (Supervisor)

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