Figure 3: Number of radiators in operation for December 2023 and January 2024.
For example, in a common residential apartment building in Viborg, Denmark, with a yearly heating consumption of 314 MWh(30 apartments), a yearly average return temperature of 37 °C can secure a discount on the overall heating bill of 940 EUR. The yearly bonus can be increased to 3,200 EUR if the average annual return temperature can be reduced to 32°C – equivalent to a discount on the heating bill of 107 EUR per apartment. On the contrary, an annual average return temper- ature of 45°C corresponds to a yearly penalty of 1,930 EUR. The introduction of motivation tariffs helped, among other ac- tivities, to incentivize the improvement of the heating systems operations and reduce the yearly supply and return temper- ature in the Viborg district heating network from 80/50 °C in 2002 to 68/40 °C in 2023. However, there are two potential ar- eas for improvement: 1. The penalties or bonuses are equally divided among all flats/ tenants. In cases of rented properties, the building owner does not have any interest in investing to secure optimal op- eration of the heating systems 2. By equally dividing the fines or incentives, the heating bills do not fairly reflect the actual influence of each end-user in the overall average return temperature
compensate for the lack of heat emitted from the non-active radiators. The difference is evident from the extra temperature measurements from the sensors mounted on the distribution pipelines in two staircases of one building part of the survey, as presented in Figure 4. Higher temperatures were observed when more radiators were turned off in the apartments connected to the distribution pipelines in Staircase 1, resulting in an overall return temperature of 45 °C. On the contrary, on Staircase 2, where the users have good habits in keeping most radiators in operation, the overall return temperature in the distribution pipelines was as low as 28 °C. The economic impact of return temperature on the end-users energy bills While the magnitude of the impact may differ depending on local conditions, in a building equipped with 175 radiators, the presence of just two poorly performing valves within those ra- diators could increase the overall building return temperature by 5°C [2]. Such an increase in the overall return temperature at the building level inevitably influences heating bills. Danish district heating operators incorporate penalties or bo- nuses into the final heating bills based on the yearly average return temperature from each building. These price adjust- ments are linked with the motivation tariffs part of their heat- ing price structure. [3]
Figure 4: Impact of radiator operation on the overall return temperatures in two different staircases
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