Extended sector coupling systems of district heating and cooling technology using CO2 as a heat transfer medium

CO₂inloop aims to further develop the concept of CO₂ networks for heating and cooling. CO₂ networks can be used for supplying low-emission energy services to consumers in dense urban regions. In regions where district heating and cooling is already used extensively, the CO₂ network may provide options for further development as it provides options for use of smaller, uninsulated pipes resulting significantly lower investment and transition to renewable heating solutions by electrification using heat pumps.

Previous studies of such CO₂ grids are apparently only based on constant pressure levels. The high enthalpy of evaporation of CO₂ at around 50 bar takes effect for the heat transfer between the networks and the consumer. This means that the temperature in the lines is between 10 and 16°C. The CO₂inloop project aims to increase the flexibility of such CO₂ grids through the variation of the pressure level. The adjustment of the pressure level in the CO₂ networks influences the CO₂ mass in the circuit. CO₂ storage systems can compensate the variable CO₂ mass in the system, resulting in increasing flexibility potential and further sector coupling solutions, like integrating Solid Oxid Fuel Cells (SOFC), that can process natural gas, or even biogas directly with a high electrical efficiency of up to 60%.

The project will cover investigation of the CO₂ solution compared to conventional district energy systems from economic and environmental perspectives, including the system extensions and new control algorithms described above.

The CO₂ network should also be examined with an innovative simulation software based on the so-called soft sensor technology. This technology is currently being used for the simulation of water-based heating networks and is also to be used for the first time in CO₂inloop for CO₂ networks. A thermo-hydraulic real-time simulation of the entire CO₂ network should enable realistic monitoring with safety-enhancing effects.

• Prozess Optimal CAP GmbH
• Reiterer & Scherling GmbH
• Aros Teknik Aps
• Technical University of Denmark
• Aalborg Forsyning