Trends of the non dimensional free shaft speed are reported in Fig. 17: the reduction in n, with respect to the conventional gas turbine ("GT only"), occurs all over the day and becomes significant during the sunny hours. This is in agreement with the fact that pressure losses downstream of the compressor become more relevant at high solar rates, because of higher volume flow rates in the returning duct to GT. If n decreases, a reduction in compressor pressure ratio fi takes place (Fig. 18) and, consequently compressor outlet temperature reduces. A similar motivation can be addressed to explain differences of outlet turbine