The following main components have been included in the plant scheme (Fig. 4.):

• vacuum tube (VT) collectors;

• one co-generation unit based on a reciprocating gas engine and controlled by the heat load;

• one absorption chiller.

The VT collectors and the cogeneration unit are connected in parallel. Biomass boilers have been selected to assist the heat production with a renewable source. One compression chiller gets involved whenever the absorption chiller does not match the entire cooling demand. Solar collectors are exclusively connected to a storage tank. Thus, the solar fraction is only used when the tank reaches selected temperature levels and heat is required at the same time, otherwise it is stored. Also the cogeneration unit is served by a tank. However, in this case, the storage is employed to buffer the variable load and to prevent that the engine frequently switches on/off. The selected DS consists of radiant panels and fan coils, respectively for heating and cooling mode. It is connected to the heating and cooling facility by means of a heat exchanger. Therefore, the medium flowing through the DS is different from the one flowing through the facility. In this way, the variation of the heating and cooling demand, i. e. the variation of the mass flow in the DS, is smoothed and the machines can operate under more stable conditions.