Development of concentrated solar power and conventional power plant hybrids

Kurzfassung

CSP hybrids are one of the possible technical solutions in order to increase the share of renewable energy and decrease greenhouse gas emission levels as well as fuel consump-tion. The main objectives of the thesis are to research state-of-the-art technologies in concentrated solar power (CSP) and conventional power plants, to comprehensively study the possible integration options and to develop one CSP hybrid configuration by using Advanced Process Simulator (Apros), which is a dynamic modelling and simula-tion tool for industrial processes. Furthermore, the objectives are to develop control strategy for the hybrid and demonstrate the operation of the hybrid under steady state and transient conditions in order to find challenges of hybrid systems and future devel-opment requirements. The theory is based on the available scientific literature for CSP, conventional power plants and CSP hybrids as well as on the information available from companies and organizations working with the technologies. The model development is based on the theoretical background as well as the know-how of VTT about Apros. Based on the simulations, solar steam fed to the joint high pressure turbine increases thermal efficiency and changes the thermal balance of the steam cycle. In addition, at-tainable solar shares are studied, in which design values of live steam and reheated steam temperatures of steam boiler are reached. Furthermore, as the steam generation is decreased from the solar field, transients can be seen in steam mass flows to turbines, power output of the turbines and steam temperatures and pressures. However, the mod-elled transients could be compensated with the steam boiler and the transients are ac-ceptable for turbines. Based on the conducted research, the main challenges of the hy-brid system are identified. These are, for example, attainable solar shares, design of the steam parameters in solar field and steam boiler and combination of the two steam lines, imbalance between turbines and heat surfaces, optimization of heat surfaces and opera-tion of steam boiler under fluctuating solar irradiation conditions. The developed and modelled CSP hybrid seems to be technically feasible at least with smaller solar shares. However, the hybrid system requires more research. Thus, future development requirements include, for example, improvement of the control engineer-ing of the hybrid, research on the optimal hybrid configuration and on the possibilities to reach higher solar shares, transient simulations with higher solar shares and conduct-ing exergy and economic analyses for the hybrid system. As a conclusion, the achieved results and the developed model in this thesis provide viable information for the future development of CSP hybrids.