Techno-economic and operational assessment of concentrated solar power plants with a dual supporting system

This study evaluates the benefits of integrating a full renewable dual back-up system (biomass and Thermal Energy Storage (TES)) in Concentrated Solar Power (CSP) plants. Two plants of 50 MWe capacity each are modelled and simulated, based on Parabolic Trough and Solar Tower technologies, with the integration of a biomass grate boiler in parallel to the power island. The Analytic Hierarchy Process is used as a Multi-Criteria Decision Method to compare the performance according to technical, economic, and operational criteria of 7 operating strategies. These strategies have been defined for integrating the biomass block for five levels of TES (No-TES, 5, 10, 15 and 20 h). The results show that the participation of biomass back-up favours the operation of the system as a base-load plant, increasing the capacity factor (CF) up to 71%, the net electric efficiency up to 10%, and reducing the cost of generation down to 56%, compared to stand-alone CSP plants. For the considered solar resource (Seville, Spain), reasonable generation costs (0.153 USD/kWh) can be achieved for a balanced trade-off between biomass and TES while allowing a firm energy supply (CF ≥ 80%) and reducing the required flexibility to the boiler. In addition, generation with a high solar share (over 50%) can be achieved with the proposed dual supporting system, favouring access to solar-driven incentives, as well as reducing the sensitivity of the system to the risks associated with biomass supply.