Figure 3: Modelling of district heat generators with multiple inputs and outputs in a complex system configuration
sensitivity analysis has shown that important parameters for their economic feasibility are the specific fuel costs in winter and the delta T between the maximum storage temperature when fully charged and the minimum storage temperature when fully discharged (see Figure 4).
Optimizing the seasonal thermal storage integration. The different heat supply options in the district heating network are considered available in the summertime, resulting in a potential heat surplus. The optimization model foresees different sizes of seasonal thermal storage. A simplified
Figure 4: Results of a simplified sensitivity analysis: impact of the delta T in the storage and the specific fuel costs in winter on the return on investment of a seasonal thermal storage
winter (see Figure 5). As a result, the used storage capacity is 2.5 times higher compared to using the storage only between the return temperature of 60°C and 95°C.
Since the biomass price scenarios were optimistic, the analysis aimed to increase the delta T to improve the economic performance of the seasonal storage. The model used heat pumps to decrease the storage temperature to 5°C after the
Figure 5: Mean temperature level in the seasonal district heating storage
24 HOTCOOL no.5 2024
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