The off-grid system ensures the energy only for own residential consumption in the two main forms, electrical and thermal. The CHP unit is governed by the power
drive strategy ensuring the balance between PV production and electricity consumption of the residence. The thermal energy balance is kept in equilibrium by the additional boiler that balances the ST production, the CHP unit production and the specific thermal energy consumption of residence.
In order to increase the performance indicators of the CCHP system, especially its efficiency, the PV electricity production is correlated to the energy consumption eliminating the excess production for the month with the biggest PV production and electricity consumption, respectively (in this month ePV = esys). Similarly to the mechanical compression chiller, the utilization factor of PV panel area is recalculated and the similar procedure is used for the utilization factor of the thermal panel. The calculation result shows kpv = 0.136 and kST = 0.062 (see Tables 6 and 36).
The calculation result (Table 37) allows the graphic representation of the electricity balance shown in Fig. 41 and the thermal balance shown in Fig. 42.
The monthly heat balance has a small excess. After the calculation of the heat and electricity from solar energy, it is necessary to verify the conditions set about architectural sustainability and utilization factors. For this case the results show a utilization factor of 19.8 % (less than 40 %).
The performance indicators obtained indicate a reduction of the PES = 64 % and a significant increase of the CCHP system’s global efficiency EFF = 84.6 %. The monthly distribution of PES is given by Fig. 43.
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Table 37 Performance improving for structural model type off-grid
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