Perspectives on fourth and fifth generation district heating

Abstract

Fourth-generation district heating (4GDH) has been used as a label or expression since 2008 to describe a transition path for decarbonization of the district heating sector and was defined in more detail in 2014. During recent years, several papers have been published on a concept called fifth generation district heating and cooling (5GDHC). This article identifies differences and similarities between 4GDH and 5GDHC regarding aims and abilities. The analysis shows that these two are common not only in the overarching aim of decarbonization but that they also to some extent share the five essential abilities first defined for 4GDH. The main driver for 5GDHC has been a strong focus on combined heating and cooling, using a collective network close to ambient temperature levels as common heat source or sink for building-level heat pumps. It is found that 5GDHC can be regarded as a promising technology with its own merits, yet a complementary technology that may coexist in parallel with other 4GDH technologies. However, the term “generation” implies a chronological succession, and the label 5GDHC does not seem compatible with the established labels 1GDH to 4GDH.