Control strategy is fundamental in managing such a large and complex plant as it determines how the single machines get involved in the operation of the overall system. For this purpose several PID and on/off controllers have been included in the selected layout. The most significant of them are committed to control the variable speed pumps (VP in Fig. 4.) which regulate the mass flow in each component, except the cogenerator where a fixed mass flow is imposed. The goal is to supply heat and
cold energy flows at constant and unique selected values. E. g. a PID controller regulates the mass flow in the primary solar loop in order to reach the winter/summer set temperatures (VP S1 in Fig. 4.), or the hot mass flow entering the generator of the absorption chiller is regulated in order to provide chilling water at the temperature requested by the users (VP H in Fig. 4.).

Further important control devices are the diverters (Div H and Div C in Fig. 4.) which deliver the flows to the single units according to the following hierarchies: solar tank, cogenerator tank and biomass boiler on the hot side, absorption chiller and compression chiller on the cold side; it has to be highlighted that the temperature of the hot storage tanks are checked by means of on/off controllers before they get involved in the operation.