Abstract
Automated hydronic balancing in space heating systems is crucial for the fourth-generation district heating transition. The current manual balancing requires labor- and time-consuming activities. This article presents the field results of an innovative electronic radiator thermostat tested on two Danish multi-family buildings. The prototypes had an additional return temperature sensor on each radiator and an algorithm was used to accurately control valve opening to ensure automated hydronic balancing. The results highlighted that the new thermostat performed as expected and helped secure the cooling of district heating temperatures —defined as the difference between supply and return temperature—4–12 °C higher during the test compared to results obtained in 2020, when the prototypes were replaced with state-of-the-art thermostats in the first building. The measurements from the other building illustrated how only two uncontrolled radiators out of 175 could contaminate the overall return temperature. The remote connection of the thermostats helped pinpoint the faults in the heating system, although the end-users were not experiencing any discomfort, and secure, after fixing the problems, a return temperature of 35 °C. Future designs may consider integrating a safety functionality to close the valve or limit the flow in case of damage or malfunction to avoid a few radiators compromising the low-temperature operation of an entire building before the cause of the problem has been identified.
Highlights
Heating and cooling in buildings account for almost half of the total final energy consumption in the EU [1] and represent a strategic area to focus on for the ambitious EU targets of reducing CO2 emissions and moving towards a sustainable energy system
District heating is among the key technologies that can sustain the green transition of the energy system due to its flexibility to integrate several energy sources
To test the functionality of the new thermostat in two apartment buildings, the prototypes were installed on all radiators in part of the buildings and measurements on the heating system operation before, during, and after the test were collected and analysed to document how the thermostats performed in terms of limiting the return temperature to the district heating substation and ensuring hydraulic balancing in the heating systems
Summary
Heating and cooling in buildings account for almost half of the total final energy consumption in the EU [1] and represent a strategic area to focus on for the ambitious EU targets of reducing CO2 emissions and moving towards a sustainable energy system. For district heating systems to provide the most economical transition to renewable energy sources, it is essential that the technology is continuously improved to reduce the operating temperatures and increase the efficiency of the systems [3]. The district heating technological development aims to lower the operating temperature to an average of 55/25 ◦ C, with the possibility of increasing the supply temperature if necessary during extreme low outdoor temperatures. This is defined in the literature as fourth-generation district heating (4GDH) [4]. Lower operating temperatures will reduce the distribution heat losses in the networks, increase flue gases condensation and the power-to-heat ratio in combined heat and power (CHP) plants, increase the heat production from renewable sources—such as solar heating, geothermal heat, and excess industrial heat recovery—and the coefficient of performance of the heat pumps [3,4,5]
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