Demand Response in District-heated Buildings

Heating and cooling account for approximately half of the total energy consumption in the European Union. That is why the European Commission in its strategy for the heating and cooling sector is emphasising ways to develop energy-saving and greenhouse gas-reducing solutions in buildings. District heating is one of the most efficient heating methods, especially in colder and densely populated areas. The challenges of district heating are large fluctuations in daily and seasonal consumption that are difficult to mitigate in the inflexible centralised production system. Additionally, district heating is mainly produced with fossil fuels and, thus, it is facing a shift towards low-carbon as well as more cost-effective systems. On the other hand, attention is being paid to the indoor air conditions in properties. The latest indoor air classifications focus on the thermal comfort of individuals in buildings that promote not only a healthy environment but also increased work efficiency. Therefore, heating control systems in buildings give priority to the comfort of people. This dissertation investigates the addition of flexibility to the district heating system by using the thermal inertia of building structures, as well as the thermal comfort of individuals during periods of demand response. In this dissertation, demand response refers to control measures for space heating in water-circulating radiator networks as a response for external requirements in demand. This dissertation develops rule-based control algorithms for room-level temperature control via water-circulating radiator thermostats connected to a cloud service. These control algorithms are applied in district-heated office buildings. The system allows for individual thermal comfort while performing optimised and targeted heating control. In addition, a district heating system with dynamic heating pricing was modeled for evaluating demand response by shifting loads in time on the building level and by utilising a centralised thermal energy storage. The results of the dissertation show that individuals report poorer thermal comfort than previously anticipated on days of demand response. Additionally, the modeling results also show that the demand flexibility of district heating utilising the thermal mass of buildings is of little benefit to the district heating company. Thus, demand response itself does not bring savings to the property owner either. However, field studies show that room-based control enables individual heating, which can save energy even in highly energy-efficient office buildings.