The overall electrical consumption for the space heating and the domestic hot water production will be illustrated in this paragraph considering its distribution depending on the Tariff. The following electrical consumptions have been taken into account:
- Heat pump; in the Air Source Heat Pump has been evaluated also the contribute of the auxiliary heat exchanger;
- Primary pump; obviously this contribute has been considered only in the Ground Source Heat Pump;
- Secondary pump and DHW pump;
- Electrical resistance placed inside the domestic hot water tank; this electrical consumption has been evaluated only in the case variation 2.
74
11.1.1 Ground Source Heat Pump
Figure 35 Monthly electrical consumption GSHP reference case
Figure 36 Monthly electrical consumption GSHP variation 1 with 3 Kelvin
Figure 37 Monthly electrical consumption GSHP variation 1 with 5 Kelvin 0
Total electrical consumption depending on the Tariff [kWh]
Reference case
Tariff 1 Tariff 2 Tariff 3 Tariff 4
0
Total electrical consumption depending on the Tariff [kWh]
Variation 1 with 3 Kelvin
Tariff 1 Tariff 2 Tariff 3 Tariff 4
0
Total electrical consumption depending on the Tariff [kWh]
Variation 1 with 5 Kelvin
Tariff 1 Tariff 2 Tariff 3 Tariff 4
75
Figure 38 Monthly electrical consumption GSHP variation 2
Figure 39 Annual electrical consumption GSHP reference case and variation 1 with 3 Kelvin
Figure 40 Annual electrical consumption GSHP reference case and variation 1 with 5 Kelvin 0
Total electrical consumption depending on the Tariff [kWh]
Variation 2
Tariff 1 Tariff 2 Tariff 3 Tariff 4
529 654
Reference case Variation 1 with 3 Kelvin
[kWh]
Annual electricity demand for space heating and DHW [kWh]
Tariff 1 Tariff 2 Tariff 3 Tariff 4
-15 %
Reference case Variation 1 with 5 Kelvin
[kWh]
Annual electricity demand for space heating and DHW [kWh]
Tariff 1 Tariff 2 Tariff 3 Tariff 4
-24 %
-13 % +33 %
+39 %
76
Figure 41 Annual electrical consumption GSHP reference case and variation 2
Figure 39 and Figure 40 show how the application of Demand Side Management in the space heating doesn’t increase the total electricity demand. In fact in the reference case the yearly electricity demand is 2858 kWh and in the variation 1 with 3°C and 5°C it is 2853 kWh and 2869 kWh respectively. Furthermore in this type of optimization another important result is to move electrical consumption from times with positive residual load to times characterized by negative residual load during which the renewable energy production is higher than the electricity demand. That is very important in order to maximize the use of renewable energy. This behavior is more evident shifting the heating curve with the parameter X that is increased from 3°C to 5°C. In fact on the one hand the electricity consumption connected to negative values of residual load is 36% in the reference case, on the other hand this percentage increases to 45% and 49% in the other two cases. At the same time the application of Demand Side Management to the production of domestic hot water (Figure 41) in this context isn’t an effective solution. The mainly result is to increase the electricity demand to 3723 kWh. Since the only consequence has been to increase the electricity consumption when residual load is negative (Tariff 1 and Tariff 2) the combined optimization of space heating and domestic hot water has not been considered. In fact the electrical resistance that increments the set point temperature at the top of the domestic hot water tank to 65°C is not effective in terms of storing energy inside the tank because the tank capacity is too small and because the water originating from the aqueduct is cold (10°C).
529 926
Tariff 1 Tariff 2 Tariff 3 Tariff 4
+75 % +97 %
-7 % +2 %
77
11.1.2 Air Source Heat Pump
Figure 42 Monthly electrical consumption ASHP reference case
Figure 43 Monthly electrical consumption ASHP variation 1 with 3 Kelvin
Figure 44 Monthly electrical consumption ASHP variation 1 with 5 Kelvin 0
Total electrical consumption depending on the Tariff [kWh]
Reference case
Tariff 1 Tariff 2 Tariff 3 Tariff 4
0
Total electrical consumption depending on the Tariff [kWh]
Variation 1 with 3 Kelvin
Tariff 1 Tariff 2 Tariff 3 Tariff 4
0
Total electrical consumption depending on the Tariff [kWh]
Variation 1 with 5 Kelvin
Tariff 1 Tariff 2 Tariff 3 Tariff 4
78
Figure 45 Monthly electrical consumption ASHP variation 2
Figure 46 Annual electrical consumption ASHP reference case and variation 1 with 3 Kelvin
Figure 47 Annual electrical consumption ASHP reference case and variation 1 with 5 Kelvin 0
Total electrical consumption depending on the Tariff [kWh]
Variation 2
Tariff 1 Tariff 2 Tariff 3 Tariff 4
743 900
Reference Variation 1 with 3 Kelvin
[kWh]
Annual electricity demand for space heating and DHW [kWh]
Tariff 1 Tariff 2 Tariff 3 Tariff 4 -9 %
Reference Variation 1 with 5 Kelvin
[kWh]
Annual electricity demand for space heating and DHW [kWh]
Tariff 1 Tariff 2 Tariff 3 Tariff 4 -16 %
+37 % +26 % -9 %
79
Figure 48 Annual electrical consumption ASHP reference case and variation 2
Figure 46 and Figure 47 show that also in this case the Demand Side Management applied to the space heating is effective in order to increase the portion of electrical consumptions characterized by negative values of residual load. More specifically the electricity demand covered by electrical feeding with Tariff 1 and 2 is 34% in the reference case, 41% in the variation 1 with 3 Kelvin and 45% in the variation 1 with 5 Kelvin.
Furthermore it’s important to highlight that the overall electrical demand increases only of 2%
in both variation 1 with 3°C (4457 kWh) and variation 1 with 5 Kelvin (4436 kWh) if it is compared to the reference case (4339 kWh). At the same time its value is higher than the one of Ground Source Heat Pump because the efficiency of this system is lower. As for the previous case the Demand Side Management applied to the production of domestic hot water is not effective because the mainly consequence is to increase considerably the overall electrical consumption up to 5177 kWh. In fact on the one hand the electrical consumption connected to Tariff 3 and 4 remains almost unchanged, on the other hand the consumption connected to Tariff 1 and 2 increases of 42% and 57% respectively.