Practices

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Integrating low-temperature renewables in district energy systems

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Image by Hands off my tags! Michael Gaida from Pixabay

Guidelines for policy makers

Reducing the heating and cooling sector’s emissions is critical to mitigating against changes in climate and reducing air pollution. In this regard, district heating and cooling systems can assist in scaling up renewable energy use, increasing energy efficiency, decreasing the utilisation of fossil fuels in the heating and cooling sector, and improving urban area air quality.

 

Traditionally, district heating systems have been built to run at high temperatures to satisfy high heat demands from poorly insulated buildings. Achieving the high temperatures required in most cases necessitates the use of fossil fuels. However, technology innovation, digitalisation and current trends towards more energy-efficient buildings may enable the broader deployment of clean energy technologies such as low-temperature geothermal, solar thermal and energy from water bodies as well as low-temperature waste heat sources in the new generation of district energy systems. These sources are widely available at the local level in many regions. Still, they remain largely untapped because they are not immediately compatible with current district energy infrastructure and existing building stock.

 

The utilisation of low-temperature renewable energy sources and sustainable waste heat in district energy systems is often hampered by barriers, including the following:

 

  • lack of data
  • insufficient knowledge and awareness about the best available technologies
  • disconnection with building renovation strategies
  • unfair competition with individual fossil-based heating systems or electric cooling systems
  • high upfront costs
  • budgetary constraints at the municipal level
  • inadequate regulation and lengthy authorisation procedures.

Given this background, this guidebook provides guidelines for policy makers and examples of available tools and solutions to facilitate the use of low-temperature renewable heat sources in new and existing district energy systems. An overview of applications for district heating and cooling and enabling technologies utilising low-temperature renewable energy is also presented. The guidebook focuses on energy systems utilising solar thermal, geothermal and energy in water bodies, which occur at low temperatures, as well as systems supported by heat pumps. Biomass, which represents the dominant renewable energy source in district heating, does not present major technical integration challenges with existing infrastructure running at high temperatures. Therefore, the integration of biomass into district heating will not be the focus of this report.