Reducing costs by combining technologies Combining more and different heat sources can be an important strategy from a district heating network company and consumer perspective. By combining technologies, investments may be lowered further, especially if low- investment demanding high-grade waste heat sources can be implemented in heat source design. Further, it can be important to have more and different technologies that use different fuels and electricity to ensure that the produced heat is always the cheapest possible. Combining complementary heat sources like electricity-producing technologies and electricity-consuming technologies makes heat prices low, whether the electricity price is high or low. Table 4 is an expanded version of Table 3. It shows more different heat source designs and combinations of heat sources, including storage, to make it possible to avoid peak load on natural gas boilers compared to the classic design. The investment costs for storage are total costs, which include additional costs not directly related to the storage tank (Buildings, etc.) The technical lifetime used for all technologies is 25 years, which is short for CHP. It could be augmented to be longer, which would only decrease the investment costs per MWh delivered heat. Combining different technologies can reduce capacity compared with the classic design, especially if heat storage is used for peak load delivery. When the technologies can be divided into smaller and more units with the same costs per MW-heat capacity, peak, and reserve load capacity investment costs can be reduced. If, for some reason, a larger plant is cheaper per MW-heat capacity, some of the benefits from having more and different technologies may be lost. The design with the lowest investments is the high-grade waste heat combination because most investments are expected to be in the supplier of high-grade waste heat. Investments in connecting the source, which in some cases can be significant
and differ greatly depending on the source and distance to the source, are not included in this calculation.
The main conclusion from the different combinations of heat sources is that high-grade waste heat sources should be preferred, but it is also possible to combine different technologies and choose low-carbon solutions without increasing investments. The large benefit of combining technologies is the possibility of changing technology if fuel and electricity prices change. This not only gives consumers a reliable heat price but also increases the heat network company's possibility of profit and, at the same time, competitiveness. A second benefit of combining technologies and heat sources is the ability to choose production patterns according to hourly power prices and deliver flexibility/reserve capacity to the power market, which normally is paid for. The benefits from power prices are investigated in the next chapter for the same technology combinations. Benefits power prices To simulate the benefits of having a heat storage system and the flexibility of multiple heat sources, all electricity prices in the first half of 2023 in England are mapped, and a model is made for heat production without and with heat storage on the same heat delivery as above. A storage with a capacity of 200 MWh is included, which will demand an investment of 0.53 million £. Over 25 years, this investment will cost 0.002 £/ MWh per MWh-heat delivery to consumers.
Below, Table 5 shows input data for the scenario combining CHP with a heat pump, electric boiler, and gas boiler:
The strategy is to choose production using electricity-based technologies with the lowest heat production prices first. If more production than needed, prioritised heat is allowed to
Heat production design model
100.000
Annual Heat demand
Input
MWh-heat
20%
Expected share hot tap water
Input
17%
Heat loss
Input
Natural gas price including variable tariffs
47
Input
£/MWh
Waste heat price
20
Input
£/MWh
No Technology prority
Capacity MWh
Heat efficiency Elec efficiency O&M costs £/MWh-heat
10
99%
0,5
1 Electric boiler
Input
MW-heat
10
350%
3
2 Heat pump air-to water
Input
MW-heat
10
100%
0
3 Waste heat - small
Input
MW-heat
10
50%
40%
5
4 CHP Gas Engine
Input
MW-heat
10
100%
1
5 Natural gas boiler
Input
MW-heat
200
Storage capacity
Input
MW-heat
3.450
(1MW = 17.25 m3 water in tank, 90/40 °C)
Calc.
m3
20
Storage level first day
Input
MWh-heat
Table 5: Data input for simulating the value of storage
23 www.dbdh.dk
Made with FlippingBook - Online magazine maker