With CO₂ against CO₂

© Jan Reich, Imperial Germany media

© Jan Reich, Imperial Germany Media

In winter, we like to be warm and comfortably cooled in summer, so we imagine our home and the ambient temperature at our workplace. Of course, we are also accustomed to having hot water available upon request. In the context of climate warming, efficient and climate-neutral applications are becoming increasingly important in all areas of life.

How can this be achieved efficiently? Suitable solutions include CO2-filled heat pumps, which can be operated CO2-neutral in conjunction with renewable electricity. Unlike the fluorinated greenhouse gases (FCKW) previously used, the global warming potential (=1) is very low. With currently used refrigerants, such as R134a, the global warming potential is 1430 times higher. Additionally, CO2 allows for very high water flow temperatures, enabling efficient heating of existing buildings. In a building, the CO2 emissions generated by heating and cooling can be reduced by a factor of 20 in extreme cases. The biggest challenge for a CO2 heat pump is that the system must withstand higher pressures. A conventional system operates at 24 bar, whereas a system of this design must withstand at least 120 bar. This means, for example, that the components have a thicker wall.

The BKW Cold-Heat Supply Technology GmbH from Wolfschlugen and the Reutlingen University of Applied Sciences are jointly researching with Enisyst GmbH (Pliezhausen), which develops intelligent solutions for energy management and optimized control of complex energy systems.

This joint research project is supported by the "Central Innovation Program for Small and Medium-Sized Enterprises" (ZIM), funded by the Federal Ministry for Economic Affairs with 600,000 euros. However, it is about more than just refrigeration technology: Through precise simulation and analysis using AI, early and predictive maintenance is enabled, and faulty operating conditions are automatically detected. A convenient remote access option with an analysis tool for the system operator is included. The digital twin of the system reports deviations before the actual malfunction occurs, as has been the case so far, preventing larger defects or failures.

The control system is derived from conventional heat pump control and adapted to the required functionality. The control also includes the interface for integration into a so-called cold local heating network. The digital twin of this cold network allows, in addition to the described maintenance concept, precise modeling in complex energy systems. This also applies to manufacturing companies—particularly for heating and cooling—such as in combination with intelligent thermal management for machinery.

This research project achieves two goals with one stroke: Multi-family homes, district buildings, and companies are to be supplied with the newly developed system, thus opening up a new business field. In particular, this conversion aims to replace order declines from the automotive industry. The second aspect of the project is the potential to counteract climate change. It offers alternatives to fossil fuels for building heating while maintaining or securing comfort, providing a customer-oriented solution. It is a combined device that can be used for heating, cooling, and domestic hot water. Especially for passive houses with air heating, this CO2 technology in heat pumps represents an energetically and ecologically promising future technology.

The importance and urgency of this topic can also be gauged by the fact that both the University of Darmstadt is researching the efficient operation of production facilities with a variable cooler from BKW, and KIT in Karlsruhe is developing new heat pump technologies, where a highly efficient CO2 heat pump from BKW is also in use.