Solar District Heating (SDH) is in the early market development stage. Large solar thermal plants feeding into district heating networks represent only about 1% of the installed capacity of solar thermal systems, despite the fact that competitive prices lower than 40 €/MWh can be reached. In the long run, solar district heating could represent 4-15% of the total technical potential of solar thermal energy.

Today, the commercial application of Solar District Heating is spreading to several countries. In particular in Denmark, where SDH is operated at feasible heat costs and the building of plants is booming. SDH activities are also well underway in Austria and in the implementation phase in Germany, Italy, France, Spain and Norway.

This Task aims to develop technical and economic requirements for the commercial market introduction of solar district heating and cooling (DHC) for a broad range of countries. The activities aim to improve technological know-how, market know-how and understanding of the boundary conditions as well as to provide expert know-how for project initiation and implementation and for training. A key element will be the direct cooperation of SDH experts with associations and companies in the district heating sector as a means to bridge the gap between these sectors.


  • Characteristics of solar thermal systems for DHC >0.5 MW up to GW systems
  • Technical and economic specifications of district heating networks which are relevant for the integration of solar thermal systems and hybrid technologies (large scale storages, industrial waste heat, heat pumps, etc.)
  • Analyses of system components and their integration: system temperature requirements, optimization of hydraulic systems, interdependences between large collector fields and seasonal storages, control strategies, self-learning controls, large collector field performances, assessment and design of large seasonal storages (>50.000 m³), system performance guarantees, system ratings and certificates
  • Modular design of large SDH/SDC systems including hybrid technologies (large scale storages, industrial waste heat, heat pumps, etc.)
  • Up-scaling potential of existing medium/large SDH/SDC systems to up to GWth systems
  • Economic requirements of large SDH/SDC systems, market analyses of global and country developments 

Cooperation with IEA DHC

The IEA Technology Collaboration Programme on District Heating and Cooling including Combined Heat and Power (IEA DHC) officially cooperates with Task 55 of the IEA Technology Collaboration Programme on Solar Heating and Cooling (IEA SHC). The SHC Task 55 will integrate input provided by IEA DHC in its publications and communication, and receive reviews for Subtask A and additional information from the IEA DHC.


In recent years, megawatt-scale solar supported district heating systems have gained increasing attention all over the world. and several ambitious projects have successfully been implemented.  Large scale solar thermal district heating systems and their large-sized seasonal storages have become an attractive solution for districts´ cost effective and low carbon heat supply. In a next step, large systems will become even bigger and likely grow in size from MEGA to almost GIGA-size to meet the increasing energy demands of districts and cities. These concepts of large-scale solar thermal and seasonal storages are well scalable and transferable to other district networks, independent of their age.

The effective operation of a SDH network and its seasonal storage guarantee a primary energy consumption reduction of >70% in thermal needs (compared to conventional heat generation systems). Depending on the waste heat available and the districts´ energy demands, it is possible to reduce the primary energy consumption up to 100%.

This Task is a follow-on to IEA SHC Task 45: Large Scale Solar Heating and Cooling Systems.  Task 45 focused on components and collector performances of large-scale (>0.5 MW) solar thermal systems. This Task will focus on the Solar Thermal System characteristics of very large SDH (solar district heating) and SDC (solar district cooling) installations > 0.5 MW up to GW systems.


Objectives of the Task are:

  • Description of low cost and high performance large-sized SDH/SDC systems, their main components, hybrid technologies (large scale storages, industrial waste heat, heat pumps, etc.) and guidelines for their construction
  • Simulation of the integration of large seasonal storages, hybrid technologies and large collector arrays into different district heating networks
  • Description of crucial components of modular conception and construction of SDH/SDC systems
  • Elaboration of business and financing calculation models
  • Validation of measurement methods of tests on field collector performances and singular collector tests in the laboratory
  • Country reports, license requirements, feasibility studies and a database on large SDH/SDC systems in established and new markets
  • Expert and industry workshops and presentations to communicate task findings
  • Cooperation on a moderate level with the IEA Technology Collaboration Programme on District Heating and Cooling including Combined Heat and Power (IEA DHC), focusing SDH/SDC network designs and analyses