Figure 2: Classic heat source design
When the demand curve is established, the last 20%—30% of heat production capacity demand often only covers 3- 5% of needed production. From an investment point of view, it then can be an idea to establish base load capacity covering around 70 – 80% of capacity demand and use cheap boiler technology for peak- load and reserve load capacity. By reducing the base load capacity, investments are saved for both base load capacity and the reserve and peak load capacity, which only need to cover up to 70 - 80% of capacity demand. In our example, the 70% line can be seen in Figure 3. The demand above 70% of capacity is 2.9% of total demand. Table 3 compares the differences between individual heat source investments and investments in a basic or classic heat source design. In the basic design, a total capacity of 30 MW
The network investments are calculated to be 34.8 million £ and unit investments in production technology, including household units, are calculated to be 37 million £, and then the combined savings by implementing a district heating solution can be calculated to be 25.2 million £, which is 24% lower than original individual heat pump design. See Table 2. Reducing costs by classic heat source design The basis for designing a heat source system for district heating is that security-of-supply requires that reserve load capacity should have a size that covers the largest base load unit if it, for some reason, falls out of production. If the heat source design is made carefully, investments in heat sources can be optimised. Figure 2 shows the classic district heating heat source design principle, dividing the capacity into base, peak, and reserve load capacity.
Figure 3: Capacity demand curve example - 70% of demand
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