###### Abstract  
Currently, Micro Gas Turbines (MGTs) are widely used in small buildings, such as offices, hospitals, or households, in which electricity and thermal energy are needed. Their reliability, flexibility, and compactness allow these devices to operate in different regimes to fulfill the power demand. The opportunity to operate at partial-load is deeply investigated in this paper. To cope with the fast, unpredictable demand of energy, thermal storage and batteries are most commonly installed. The potential of these two components for the operating cost is also investigated in this paper in order to provide guidelines on their sizing. Moreover, the thermal and electrical energy demands depend on different factors such as building size, weather, day of the week, and location, all modeled in this work; the possibility to buy and feed electricity into the grid adds a further variable to the economic analysis. All these factors were considered in this study and led to the creation of an optimization algorithm, which was able to determine the optimal operating profile of the system for every single scenario. The operational optimization of a micro gas turbine, the MTT Enertwin, is presented. Data from experimental measurements were implemented in the algorithm in order to characterize the system performance. Concerning the input power demands, data for Germany according to the norm VDI 4655 were considered; hence, the results are formally limited to this region. However, considerations of batteries and thermal storage were broadly valid; also, the results can be of international interest in countries with a similar climate and habits. With this study, it is shown that the optimal operational strategy is in the vast majority of cases the full-load, with savings up to 20% with respect to partial-load. Furthermore, batteries between 1.5 and 2 kWh constitute the best compromise between installation costs and savings; the investment can be generally paid off in less than 3 years. Finally, a threshold of 400 L for thermal storage was identified. Micro Gas Turbine (MGT); MTT Enertwin; Combined Heat and Power (CHP); operation optimization; battery; thermal storage +
Footnote †: journal: 15 June 2022  
to provide the most comprehensive study. In fact, due to the long time needed to start (minutes), an MGT cannot cope with the much faster, unpredictable demand of energy (seconds). For this reason, thermal storage tanks and batteries are typically installed near the end-user CHP system, to help reduce the transportation and distribution losses [4]. The energy demand affects the CHP system operation at every moment. The following scenarios are possible:  
* The system is running, and the demands are directly fulfilled with the energy produced;
* The system is running, but there is partial or no demand: the water tank and the batteries are loaded. If the batteries are full, electricity can be fed back into the grid;
* The system is not running, and the demands are fulfilled with the energy from the water tank and batteries. If the batteries are empty, electricity is provided from the grid;
* The system is not running, and there is no demand: nothing happens, apart from heat losses removing heat from the water tank. A compromise among the overall losses and fulfilling the demand and installation costs must be found. One of the novelties of this study is the sizing of thermal storage and batteries depending on the building size and the climate zone where the system is installed. In order to fulfill the electrical and thermal power demands, MGTs can operate in a wide range of regimes, the so-called full-load and partial-load. The time sequence of the starts, stops, and operation points of the system over 24 h is called the operative profile. The scope of this paper is to determine the most economical operative profile of an MGT-based CHP system. This is done by means of an economic analysis via the optimization of the control strategy and the minimization of the total costs.