Concentrated solar power and circulating fluidized bed power plant hybrids: Final results of the COMBO-CFB project

Concentrated solar power (CSP) is a renewable energy technology, which is able to provide dispatchable power according to demand. Dispatchability is typically achieved by decoupling solar thermal collection and power production with a thermal energy storage system. However, storage solutions for direct steam generating CSP technologies are still in a development phase. Hybrid system, in which solar field is integrated to a conventional power plant, is another option to produce renewable load-following power. The main idea in a hybrid system is to compensate the variation in solar thermal production with the steam boiler. In addition to dispatchable nature of power production, hybrid system offers several other possible benefits with respect to stand-alone CSP plant, such as reduced fuel consumption and emissions, enhanced plant efficiency and reduced production costs. However, the highly dynamic nature of the process imposes some challenges for the design and operation of the system, in particular in the case of significant solar share. Dynamic analysis of the system is foreseen to be utmost important in the plant design phase in order to take into account all the dynamic interactions in the process, which could affect for example the balance of different boiler heat transfer surfaces and turbine sections. The project "Combination of Concentrated Solar Power (CSP) with Circulating Fluidized Bed (CFB) power plants" (COMBO-CFB) aimed at developing innovative, flexible and high-efficient hybrid concept, which is able to balance the distributed intermittent production. The concept development included both experimental work and dynamic modelling and simulation. The research focused on the capacity building in terms of different CSP technologies, hybrid concepts and thermochemical processes, and in technical feasibility of the hybrid concepts, including the benefits provided by different concepts, challenges and possible future improvements. Three different hybrid concepts were studied in detail, namely: 1) Feedwater preheating concept, 2) Cold reheat line concept, and 3) High pressure turbine concept.