A Demand-Responsive Control Strategy to Reduce Return Temperature at District Heating Systems

What is it about?

In this paper, an innovative approach to managing district heating systems, which are large-scale networks providing heat to multiple buildings within a community, is introduced. The method focuses on a demand-responsive control, which means the system can adjust itself based on the actual heat demand characteristic of the end-users. One key aspect of this strategy is that it can work with different types of substation configurations commonly found in district heating systems. These configurations, known as direct and indirect substations, have different ways of transferring heat to buildings. The approach takes into account their specific characteristics to ensure the most efficient operation possible. Instead of relying solely on traditional methods like adjusting the supply temperature based on the weather, this new strategy takes a different route. The design is maintained to monitor how well each building indoor heating system is performing and adjust the supply temperature accordingly at the district level. This way, it is ensured that each building gets the right amount of heat to stay comfortable without wasting energy. It's important to note that sometimes the standard methods, like adjusting for weather, might not be enough to keep everyone comfortable. This highlights the need for proper setup and ongoing optimization of district heating systems. This demand-responsive control strategy offers a solution to adapt to these situations, ensuring comfort and efficiency for all users.

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Photo by Alexandr Podvalny on Unsplash

Photo by Alexandr Podvalny on Unsplash

Why is it important?

This current paper aims to explore and formulate an operational control philosophy aimed at achieving lower return temperature degrees at the District Heating (DH) level, with particular emphasis on space heating as an alternative to conventional rules-of-thumb, such as the weather-compensation curve. The pipe dimensioning determined during the design stage is influenced by the control strategy to be considered during DH operation. Consequently, the strategy developed within this research work, which involves boosting supply temperature during the coldest peak periods, demonstrates the potential to reduce the required flow rate at these times, thereby affecting the sizing of the pipes. The operational control method developed, as detailed in this paper —a completely novel control strategy— proposes a new resetting strategy for DH supply temperature structured as demand-responsive operational control. This control automatically adjusts the supply temperature in response to feedback signals of demand nature from end-users and their equipment. The primary concept behind this control is to fine-tune the supply temperature to an optimal level, resulting in a reasonably low return temperature from the end-users under varying conditions. Taking into account end-user behaviour and limitations on the maximum supply temperature, a real-time temperature resetting can be modelled within a demand-responsive framework.