District heating and cooling (DHC) technology as part of the future smart energy system

What is DHC and how does it work? District heating delivers heat from the source (gas, renewable or waste energy, etc.) in the form of steam or hot water to buildings through underground pipes in a closed loop system. The water is then returned to the source, reheated and delivered back to the buildings in a continuous cycle. A district cooling system works in the same way, except chilled water is piped to the buildings for use in air conditioning.  

Heating and cooling in the residential sector are responsible for about 40% of overall energy use. As building and transport systems have evolved, DHC technology has developed through several generations since its introduction at the end of the 19th century. The direction of development of the first three generations has been in favour of lower distribution temperature. 

Fourth generation DHC (4GDHC) further addresses the challenge of adapting district heating and cooling for low-energy buildings and helping the development of renewable energy by using lower-temperature waste heat and connecting the electricity network with the thermal grid. 

Tractebel is involved in several ongoing 4GDHC projects: 

• Heating district using geothermal heat coupled with heat pump 

• Cooling district using standard chillers coupled with ice thermal storage 

Our teams also propose smart solutions combining heating and cooling district with electricity and gas grids and the use of renewable sources: 

• Coupled heating and cooling district using combined heat and power (CHP) with standard and absorption chillers 
• Use of lake or non-potable water network for chillers cooling 

A recent success in France, with ENGIE, is the GéoMarne project, in the suburbs of Paris. In this project, we are in charge of project management services for the power plant and the networks, both in the design and the execution of the project. The key technical characteristics are:  

• Deep geothermal energy (Dogger aquifer -1900 m), coupled with heat pumps, back-up by gas boilers, P_total = 47 MW 
• District heating: 19 km in Champs sur Marne and Noisiel towns 
• Geothermal plant: Pre-FEED and basic design, procurement, detailed design, construction and hook-up, commissioning, industrial tests, acceptance of works (including 3D – BIM (Revit)) 
• District heating: design of the network with FATHOM (thermal-hydraulic simulation) 
• Commissioning: September 2021  
• Supply of heating and hot water for > 10 000 equivalent houses 
• > 80% renewable energy 

“The next generation of DHC (5GDHC), based on the exchange of thermal energy between buildings with different needs and the supply of very low-temperature water (close to the ground) to decentralized heat pumps, is beginning to emerge. As it evolves, Tractebel will continue to promote it and other innovative solutions that favour a smart energy system. Technologies like these, that reduce both emissions and primary energy consumption, bring us one step closer to achieving our purpose of engineering a carbon-neutral future”.  Marine BAGONNEAU, Project manager, Tractebel in France