Comparison of Medium-size Concentrating Solar Power Plants based on Parabolic Trough and Linear Fresnel Collectors

Abstract

This paper compares the performance of medium-size Concentrating Solar Power (CSP) plants based on an Organic Rankine Cycle (ORC) power generation unit integrated with parabolic trough and linear Fresnel collectors. The CSP plants studied herein use thermal oil as heat transfer fluid and as storage medium in a two-tank direct thermal storage system. The performance of the CSP plants were evaluated on the basis of a 1 MW ORC unit with a conversion efficiency of about 24% and by considering different values of solar multiple and thermal storage capacity. The comparative performance analysis of the two CSP solutions was carried out with reference to the direct solar energy availability of Cagliari, Italy (1720 kWh/m2y) on a yearly basis by means of specifically developed simulation models.The results of the performance assessment demonstrate that CSP plants based on linear Fresnel collectors lead to higher values of electrical energy production per unit area of occupied land. The highest specific energy production of CSP plants based on linear Fresnel collectors is about 55-60 kWh/y per m2 of occupied land and it is achieved with solar multiples in the 1.74-2.5 range and storage capacities in the range of 4-12hours. The highest specific production of the solutions based on parabolic trough collectors is about 45-50 kWh/y per m2 of occupied land and is achieved with lower solar multiples (around 1.5-2.3). Owing to their better optical efficiency, the use of parabolic troughs gives better values of energy production per unit area of solar collector (about 180-190 kWh/m2 vs. 130-140 kWh/m2).