Unleashing Flexibility from Electric Boilers and Heat Pumps in Danish Residential Distribution Network

This paper presents an overview of the electrical and thermal behaviour in a Danish residential area, followed by an examination of the possibility and need for interaction between the heating elements such as electric boilers (EBs) and heat pumps (HPs) and the electric distribution network. Under voltage and grid congestion are main focus issues for investigation of the electric network condition. In this paper, a model of a two layer stratified hot water tank, heated by an EB or a HP for grid integration, is proposed along with its advantages for demand response control. Responses using this model is compared to responses from an average model of the hot water storage tank to evaluate the benefit of the more detailed model. Finally, analysis on consumption patterns of electrical and thermal loads in residential buildings in Northern Jutland, Denmark, are used for analysis of the system and use of thermal units as flexible consumer loads in the low voltage (LV) distribution network grid. The models of EB and HP with storage tank are briefly discussed in relation to the actual control and flexibility based on grid condition and status of storage tank temperature or position of the stratified layer.

The problem formulation and models in the work are conducted based on the requirements and suggestions evolved from discussions with the local heat distribution utility. The requirements are framed based on their experience and vision to integrate more thermal units in the energy systems and thereby improving its techno-economic efficiency. The data used for the evaluation are also from the real household sites in Denmark provided by the district heating utility. Focus is on the low-voltage grid, and that’s very relevant since many doesn’t expect any flexibility from that voltage level. Study performed shows that usage of HP and storage unit has less impact on the grid voltage and congestion when compared to EB.