Enhanced thermodynamic and economic investigation of using heat recovery steam generators for solar thermal power plants

This study investigates the use of heat recovery steam generators (HRSGs) connected to three types of concentrated solar power (CSP) technologies for solar thermal power plants for the city of Faro-Poli located in northern Cameroon. The HRSGs are designed for the solar thermal power plants using solar tower (ST) technology as HRSG-1 and using parabolic trough collector (PTC) and linear Fresnel reflector (LFR) technologies as HRSG-2. HRSG-1 operates under temperatures between 56.4 and 314.9 °C, whereas HRSG-2 (PTC) and HRSG-2 (LFR) work under temperatures between 57.9 and 264 °C. The exergoeconomic analysis reveals that costs per exergy unit of the solar field system vary from 2.31 to 5.32 $/GJ and that relative cost differences and exergoeconomic factors of HRSG-1 (ST), HRSG-2 (PTC), and HRSG-2 (LFR) are 0.086 and 90.0%, 0.063 and 85.2%, and 0.112 and 72.0%, respectively. The results also show that costs per exergy unit of the HRSGs connected to these three CSP technologies are between 2.41 and 8.41 $/GJ. The avoidable-endogenous exergy destruction values are 158.5, 498.8, and 570.4 kW for HRSG-1 (ST), HRSG-2 (PTC), and HRSG-2 (LFR), respectively. Further, it is seen that HRSG-1 owns the lowest levelized cost rate of product with a value of 0.36 $/h, while the other two HRSG-2 technologies have a value of 1.08 $/h. Finally, the sensitivity analysis shows the cost reduction potential of the HRSGs to make them economically viable. It is concluded that the HRSG-1 (ST) is the most efficient technology considering its impact on the overall exergy efficiency, the levelized cost rate of product, and the cost per exergy unit.