is constructed at 12 kW-heat, which is (12-11)/11 = 9.1 % above needed capacity. This extra individual capacity investment is not needed the same way when a district heating solution is established because a peak and reserve load capacity deliver the security of supply. If, instead, an 11 kW capacity could be installed, the investment would totally be 8.5 million £ lower, which is 8.1 % lower than the original individual heat pump investment. See Table 2. Reducing capacity demand District heating systems are not affected by peak load hot tap water demand the same way as individual heat pumps because households in a heating network do not use hot tap water at the same time. The stored energy in the district heating network water can deliver the needed energy in peak load hours either by reducing the forward temperature momentarily or by increasing the forward temperature a couple of hours before the peak load hour occurs. Figure 1 shows a capacity duration curve for Manchester. The heat production capacity demand for one household is compared with the same need for capacity in a district heating system, including hot tap water and heat loss. In our example, the production capacity in the district heating system only needs to be 4.0 kW-heat compared to 11.0 kW- heat for the individual household. The reason is that the district heating system only needs to deliver average capacity demand on a daily basis compared to an individual heat pump delivering on an hourly basis. Theoretically, this saves 61.6 million £ investments in individual heat pumps or 59% of investments if the individual heat pump would have been 4 kW instead of 11 kW. This saving, though, is theoretically because of the heat piping network, and each household needs a district heating unit, which requires investments. The district heating capacity for producing heat, including heat loss, is significantly cheaper than individual technology.
The saved investment costs compared to individual solutions on the identified ways to reduce investments are calculated to be 8.1% regarding saving the extra individual capacity, 24.0% by reduced capacity demand, including heat network investments, and 7.0% by making a classic heat source design. The investment in heat source capacity by combining more technologies is almost on the same level as the classic design, as shown in the last four examples (columns). In the last three heat source designs, a heat storage capacity of 200 MWh (3,450 m3) is combined. See also tables 3 and 4 for more details. The OPEX cost comparison clearly shows that combined technologies, including heat storage, can reduce heat price costs significantly from a price of around 30 £/MWh to a price below 16 £/MWh. The reason for this is the possibility to choose operation on different technologies in hours where electricity prices result in very low heat prices. This result is important because society additionally gains value from this by reduced electricity prices, reduced electricity curtailment from wind turbines and solar PV, saved investment in power grids, saved investments in renewable power production capacity, and reduced balancing costs and investment costs for the security of supply in power system. Reducing extra individual capacity When an individual heating solution is established, the heat source capacity must be able to cover demand on the coldest day and hour during the year and heat the hot water immediately, which often requires 25 kW-heat capacity or within an hour less to heat a water tank. In our example, the capacity for individual supply must be at least 11 kW. To ensure capacity demand is covered, the installed equipment is chosen to be the size just above the maximum capacity demand, which in our example means the heat pump capacity
Figure 1: Heat production capacity demand district heating and individual heating per dwelling
20 HOTCOOL no.6 2024
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