Domestic gas hybrid technologies and their interaction with the Danish energy system

The decision to remove fossil fuels from the Danish space heating market necessitates a development of electrification of the residential heating and greening of the district heating. Removing gas boilers and replacing them with electric heat pumps may, however, not be simple. It will require investments costs both for the end users and in the development of the infrastructure needed for supplying electricity to all users also in the coldest days of the year. Therefore, hybrid solutions (combining a gas boiler with an electric heat pump) are attractive: gas can take over during the very cold days of the year, making the costly development of an infrastructure needed for a limited time unnecessary. Considering also that electric heat pumps’ efficiency is not very high for low external temperature, the use of gas will bring better overall energy efficiency to the system. The paper describes the results obtained until now in Denmark from the introduction of the technology and from the first field test, obtained both on integrated technologies and with the so-called add-on technologies where a new electric heat pump is installed together with an existing gas boiler. The field tests carried out are part of a national programme aiming to promote the implementation of heat pumps in Denmark, and the results should be used not only to evaluate the performances, but also to find solutions to practical issues encountered and to uncover general feasibility, to bring the technologies into use in Danish houses.