Abstract
When buildings become more energy effective, the temperature levels of district heating systems need to be lower to decrease the losses from the distribution system and to keep district heating a competitive alternative on the heating market. For this reason, buildings that are refurbished need to be adapted to suit low-temperature district heating. The aim of this paper is to examine whether four different energy refurbishment packages (ERPs) can be used for lowering the temperature need of a multi-family buildings space heating and domestic hot water (DHW) system as well as to analyse the impact of the DHW circulation system on the return temperature. The results show that for all ERPs examined in this study, the space heating supply temperature agreed well with the temperature levels of a low-temperature district heating system. The results show that the temperature need of the DHW system will determine the supply temperature of the district heating system. In addition, the amount of days with heating demand decreases for all ERPs, which further increases the influence of the DHW system on the district heating system. In conclusion, the DHW system needs to be improved to enable the temperature levels of a low-temperature district heating system.
Highlights
The housing and service sector represents almost 40% of the total energy use in Sweden [1]
The annual energy use for the reference case and each energy refurbishment packages (ERPs) is presented in Figure 1 and the relative changes compared to the reference case are described below
For all ERPs, the influence of the domestic hot water (DHW) temperature is larger than the influence of the space heating temperature, wherefore the return temperature to the district heating system is similar for all ERPs
Summary
The housing and service sector represents almost 40% of the total energy use in Sweden [1]. Even though the use of fossil fuels is relatively low in this sector in Sweden, improved energy efficiency of buildings and their energy systems are important to reach political goals of a resource efficient society as well as to decrease the environmental and climate impact of our lifestyle [3]. Improved energy efficiency in buildings increases the possibility to use low-temperature heating systems due to the decreased heating load. Low-temperature heating systems combined with district heating increases the possibilities to lower the temperatures in the district heating system. Decreased return temperatures in district heating systems has proven to be one way to increase the electricity production in combined heat and power plants, and decreased supply temperatures might result in Energies 2019, 12, 4694; doi:10.3390/en12244694 www.mdpi.com/journal/energies
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