Optimal design of a hybrid CSP-PV plant for achieving the full dispatchability of solar energy power plants

Abstract

With the aim of providing fully dispatchable power using only solar energy, this paper focuses on a hybrid power generation system based on Concentrating Solar Power (CSP) and Photovoltaic (PV) plants. In particular, the CSP section is based on linear Fresnel collectors using thermal oil as heat transfer fluid, a two-tank direct TES system and an Organic Rankine Cycle (ORC) power plant. In the PV section, the PV array is coupled with a battery bank for electrochemical storage.The study evaluates the optimal design parameters (solar field area, TES capacity and ORC nominal power for the CSP section, nominal power of the PV array and battery capacity for the PV section) that minimize the energy production cost of the hybrid CSP-PV plant while the plant is constrained to follow a power output curve characterized by a constant power level. Moreover, to assess the influence of meteorological conditions, the study considers two different locations: Ottana (Italy) and Ouarzazate (Morocco).The results demonstrate that hybridization of PV and CSP technologies becomes highly cost-effective if a constant power output is required for daily time periods longer than about 16h, when the distinguishing feature of CSP plants of decoupling power generation from sunlight is effectively exploited, independently of the location under study. On the contrary, for production periods shorter than 8h, the use of a PV system coupled with a proper battery bank is the most cost-effective solution for both locations evaluated. Solar energy availability and unmet load fraction remarkably influence the hybrid plant design, especially for load duration periods in the range between 8 and 16h/day. As expected, due to the lower amount of available solar energy, the hybrid solar plant located in Ottana needs larger sizes of both CSP solar field and PV arrays than the same plant located in Ouarzazate resulting in higher energy production costs.