Combined MGT – ORC solar – hybrid system. PART A : Plant Optimization

The renewed interest towards the low range power plants operating solicits the search of optimal solutions in terms of several key aspects: - The optimization of the thermal cycle in relation with the heat addition source, say an externally fired combustor, solar energy collectors, or waste heat from topping processes, together with the choice of the most favorable operating fluid. - The realization of the power plant with affordable costs, so more suitable with its employment as a distributed energy systems. This paper deals, in particular, with a combined cycle plant consisting of a topping micro-gas turbine (MGT) and of a bottoming ORC system (fig. 1 and fig. 2). A hybrid energy source is considered by means of the integration of the conventional fuel supply with a solar field. The authors’ work proceeds with the optimization of several main parameters, say: - The location and the size of the solar field (with parabolic trough assembly) and, therefore, of the temperature limits of the compressed air in the MGT; - The more appropriate working fluid in the ORC bottoming plant; - The off-design response for the best adaptation of the system to variable heat and power demands and to changes in the solar radiation intensity.