Direct steam generation in parabolic-trough collectors: A review about the technology and a thermo-economic analysis of a hybrid system

Direct steam generation in parabolic-trough collectors is considered a promising option for reducing the cost of electricity produced in solar thermal power plants. Indeed, the use of water instead of thermal oil allows reaching high temperature levels and reducing plant complexity. Furthermore, the integration of thermal energy storage system and the hybridization of the plant with a biomass boiler permit further cost reduction. This paper focuses on the historical and technological development of the direct steam generation concept and the thermoeconomic analysis of a hybrid direct steam generation-biomass power plant equipped with a thermal energy storage system. The exergy balance and cost balance equations have been applied to each component of the plant in four different operating modes that take into account the intermittency of the solar source. Exergy results show that the solar field requires further development in order to reduce associated irreversibilities. Finally, it was found that the integration of a thermal energy storage system and hybridization with a biomass boiler reduce the final cost of electricity to 17.36c€/kW he.