Modelling District Heating Network Costs

Abstract: The solution of the undergoing climate and energy crises requires a radical transformation of the energy system, in which sustainability, no carbon emissions and energy efficiency ought to play a paramount role. This revolution should extend to all areas of the energy system, including the space heating and cooling sector, which accounts for a third of the European final energy demand and, in the European continent, it is still mostly supplied by fossil fuels.District heating is a simple but powerful technology that can contribute to tackle this challenge. As a network infrastructure, it is characterised by the flexibility of the heat production, allowing the incorporation of a wide range of heat sources over time. Furthermore, it enables the recycling of heat that would otherwise be wasted and the use of local heat sources in a more cost-effective manner. Moreover, its coupling with the electricity sector can facilitate the increase of intermittent electric renewable energy sources. Nevertheless, at the moment, district heating only covers a tenth of the European space heating and cooling needs, albeit with significant differences among countries. In addition, the development of new district heating networks is capital intensive and can only be justified in those areas where the concentration of the heat demand is sufficiently high to deliver a lower cost to society than an individual alternative. Therefore, it is crucial to assess the potential of district heating and to identify the target areas for in-depth investigations. This necessity demands easy and straightforward tools, which can provide a first order approximation of the construction cost of new networks. One of these tools is the capital cost model developed by Persson & Werner, which is based on, among others, the effective width parameter. This is an indicator of the required trench length in an area supplied by district heating and has been related to the building density. This work has contributed to the understanding of the effective width parameter in a wide range of building densities, taking advantage of one of the largest district heating networks in Denmark, and provided new equations that relate it to various indicators of building density. Furthermore, the average pipe diameter of district heating pipes has been linked to another crucial parameter in district heating technology, the linear heat density, extending prior work conducted by Persson and Werner. In addition, Persson and Werner's model and the newly found empirical expressions have been validated in various Danish district heating networks, showing that the model provides relatively accurate results on an aggregate level and large areas but dismally fails in low-extension areas. Finally, the model has been applied to the European Union showing that district heating networks could potentially supply a third of the heat demand in 2050.