Design of heliostat field for an unfired solarized micro gas turbine in a closed cycle with mass flow control regulation

Interest in smart networks has increased over the past decade. One of the main advantages is the possibility of producing electricity on site and autonomously. In this scenario, small or very small generators, installed near of the places of consumption, play a fundamental role. A real possibility is offered by the Micro Gas Turbine (MGT). Such a machine has the possibility to follow the electric load of the network and is also suitable to use solar energy as a source of heat in the cycle, through the concentration of direct normal radiation (DNI). With the solar power supply, the regulation capacity of the MGT can be exploited in order to convert all the thermal power collected. In this work, the solar field, of an unfired closed solarized micro gas turbine employing air as working fluid with mass flow control system, has been analyzed. The mass flow control system is able to adjust the mass flow rate by means of a variation in density, to control the turbine inlet temperature (TIT), as the incoming thermal power varies. The volumes of the engine, as well as the speed triangles, do not change; therefore, by keeping a TIT constant, it is possible to control the power production, according to the incident solar radiation, without a degradation of efficiency. The concentrating solar tower and receiver systems are able to produce thermal power suitable in MGT and in this case represent the only one heat source. The heliostats field control system operates together with the mass flow one, so the optimization of the solar field plays a fundamental role in controlling the TIT and increasing the energy production. This article illustrates the study of the heliostat field suitable for the aforementioned control system. Different heliostats size and solar multiple (SM) have been taken in to account to choose the best configuration of the solar field. The analysis has been carried out by the open source Solar PILOT, while the weather data of Seville town have been considered. The results show that the heliostats field best configuration allows getting a substantial energy production and let to adjust the solar flux precisely in order to control, with the mass flow control system, the TIT.