P10
The schematic cold duration curve below illustrates the production of district cooling in combination with ATES (including a warm and a cold well) and waste water. The cold well (dark green) is base load cooling in summer heating up the warm well, whereas the heat pump is peak load in combined production with heating (grey). Moreover, the heat pump generates process cooling in combined production with heat as first priority. (grey). The heat pump must, to comply with Danish legislation, cool down the ground water in winter (dark blue). Thereafter the heat pump is available for the rest of the year to “cool” the treated waste water or rather to extract heat (light green). Heat from combined production of heat and cold, directly or via ATES, is very efficient corresponding to a COP factor of 5.6. It will in general be more cost effective than heat from the CHP plants, whereas heat from waste water “only” has a COP factor of 3.4. Heat pump- Combined heating & cooling Heat pump- Cooling ground water 10 9 8 7 6 MW COLD
Moreover, as the heat production cost in the summer period is very low in the heat transmission system, it turned out to be profitable to establish ground source cooling in combination with the heat pump and thereby store cold water from winter to summer and supplement the heat from the waste water with heated ground water in winter (ATES). In this way, the project adds district cooling, waste water and ground water to be part of the integrated energy system in Copenhagen. As the heat pump installation is connected to both a chilled water tank, ground source cooling and the district heating system, it is possible to optimise the production with respect to both electricity prices and the alternative heat production cost of all plants that produce heat to the Greater Copenhagen district heating system.
Heat pump
MW COLD
5
Finally, it turned out that there was available space at the existing waste water treatment plant for the construction of the chilled water tank and the heat pump energy centre. This symbiosis is another good reason for organising all municipal services into one municipality-owned organisation that operates in the interest of the local community. As the heat pump is expected to operate with more than 6,000 max load hours and having a 10 kV cable close to the plant, it proved to be profitable for TF to connect to the high voltage grid and invest in transformers and thus establish a small “micro power grid at the waste water treatment plant” owned by TF. Heat pump Hours 0 Winter
10
Heat pump- Cooling waste water
4
9
MW COLD
3
MW COLD
8
Ground source cooling
Heat pump- Combined heating & cooling
10
2
7
9
Heat pump- Cooling ground water 1
Peak from storage tank
6
8
Heat pump- Combined heating & c
5
7
8760 Summer
Heat pump- Cooling waste water
Heat pump- Cooling ground wa
6
4
Heat pump
5
3
Ground source cooling
Heat pump- Cooling waste wa
4
Figure 2 shows the district cooling area and the waste water treatment plant.
2
3
Ground source coo
Peak from storage tank
1
2
Hours
8760 Summer
0 Winter
Peak from storage t
1
Hours
8760 Summer
0 Winter
Figure 3: Schematic duration curve of the generation of cold energy.
As there are other heat sources and heat storage tanks in the district heating system, the heat production from waste water will be optimized considering the electricity price and the value of the heat in the Greater Copenhagen district heating system. It will e.g. typically not generate heat in case of large electricity prices due to lack of wind energy (intermittent operation in light green area).
Heat Pump Installation
2000 m3 chillet water tank
Energy Centre District Cooling Phase 1 District Cooling Phase 2 Waste Water Piping District Heating Existing District Heating
0
0,02
0,04
0,09
0,14
0,18
Kilometers
Figure 2: Map of the district cooling system in Taarnby.
E N E R G Y A N D E N V I R O N M E N T
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