System Dynamics Analysis in Summer Regime

For simulating the whole system, the scheme presented in Fig. 53 in Chap. “Functional Design of the mCCHP-RES System” was modified considering the equipment characteristics. In this case, the time horizon for the system simulation was 3 days. The sources which discharge in the electric subsystem are the fol­lowing: Stirling engine, driven by the voltage controller, and PV panel. The power variation graphs of the two sources are shown in Figs. 34 and 35.

Fig. 34 Profile of the power generated by PV panel

Fig. 36 Total consumed electrical power

The electric load has the following components:

• hydraulic station pumps for the adsorption chiller;

• circulation pump of the cold water toward the ventilo-convectors;

• circulation pump of the thermal agent from the pellet boiler to the hot water tank;

• circulation pump of the thermal agent from Stirling engine to the hot water tank;

• circulation pump of the solar thermal panel.

Figure 36 presents the graph of the total consumed electrical power. This graph was established taking into consideration a series of consumptions that occur only while the equipments operate (pellet boiler, DHW) and it was considered that the cooling equipment, together its pumps, operates permanently.

In the given conditions regarding the evolutions of the source power and of the load, the battery voltage and the energy accumulated in the battery are presented in Figs. 37 and 38. It can be noticed that a permanent regime is obtained. Therefore, the operation in dynamic regime of the electrical subsystem takes place accordingly to the requirement of the battery voltage control to the set point (48.5 V).

In the thermal subsystem there are three sources of energy: Stirling engine, the ST panel, and the pellet boiler, which are controlled by the temperature controller of the thermal agent in the hot water tank. The evolutions of the powers of the ST panel and the pellet boiler are presented in Figs. 39 and 40. The evolution of the thermal power of Stirling engine is the one from the graph of its electrical power, presented in Fig. 35, multiplied by three.

Fig. 37 Battery voltage evolution in Summer Regime

Fig. 40 Pellet boiler power evolution in Summer Regime

The thermal load contains two components: the power absorbed by the condi­tioning equipment, which is considered to be constant at approximately 30 kW, and the variable power in the domestic water circuit, which was presented in Fig. 26 (for the domestic water circuit, the same load as in winter regime is considered). Figure 41 illustrates the performance of the temperature control loop. It can be noticed that the temperature of the thermal agent tracks the setpoint value (80 °C) with admissible dynamic errors.

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