Seventy possibilities for future district heating

The ongoing transformation of European district heating systems from the use of fossil-based technologies to non-fossil heat supply is summarised with a selected collection of 70 opportunities linked to fossil-free energy. These possibilities are exemplified by 284 completed, planned or proposed cases. The 70 opportunities for carbon-free district heating include using heat, connecting customers, moving heat, storing heat, sequestering carbon dioxide and adding heat along with some aspects for the entire value chain to heat use from heat recovery or heat generation. The set of 70 possibilities is neither complete nor does it contain any recommendations as to which possibilities should be used.

The time horizon for the project has been 2030, linked to the EU’s goal of reducing greenhouse gas emissions by 55% compared to the emissions of 1990. This inventory of early projects for fossil-free district heating has produced the following three important conclusions.

First: activities for fossil-free district heating can be divided into replacement and supporting opportunities. Substitute options in heat supply include linear supply from renewable energy, heat recovery from processes that generate residual heat, and non-fossil means to meet peak demand on very cold days. The linear heat supply is based on geothermal heat, solar heat and electricity supply. New heat recovery activities are possible from many different societal processes, such as biorefineries, hydrogen supply, petrochemical plants, electricity distribution, district cooling, data centers, battery factories, food supply and wastewater. Thermal layers can make the heat delivery more independent of the heat input, which also provides additional opportunities to reduce peak loads. Supporting opportunities mainly include activities to obtain lower temperatures in heat distribution networks, which increases profitability when using low-temperature heat sources. These activities are performed when using heat, connecting customers and moving heat. A planned support activity is also the separation of biogenic carbon dioxide from the natural carbon cycle, although a suitable international compensation system for this is still lacking.

Second: the nature of fossil-free opportunities differs from traditional fossil fuel-based experiences. The availability of fossil-free opportunities depends on local conditions, while fossil fuels were transported from available global resources, giving full freedom to use fossil fuels anywhere in the world. As a result, fossil-free district heating systems will not be as similar as traditional district heating systems were with fossil fuels. The local conditions for fossil-free district heating provide slightly lower degrees of freedom for the implementation of replacement options in existing buildings or systems. Therefore, it is important for the future to utilise the higher degree of freedom that is possible in new buildings and systems by using new methods and more.

Third: the common denominators of the 70 opportunities identified are number of degrees of freedom for fossil-free, action plans to obtain lower temperatures in heat distribution networks, different ways of using heat pumps to upgrade low front temperatures to meet higher temperature needs of customers, possible smart digitisation options, clear delivery responsibility, favorable institutional frameworks and digital planning tools. These seven common denominators are effective tools to obtain more efficient fossil-free district heating systems, since the traditional district heating technology was once designed for systems based on the use of fossil fuels.