HOFOR, VEKS, and CTR strive to be DH CO2-neutral in 2025. To achieve this, they focus on existing and well-known technologies and new and less-tested ones.
By Lars Hansen, Market Director, CTR (Metropolitan Copenhagen Heating Transmission Company);
Morten Stobbe, Vice President, VEKS (DH in the Western suburban area of Copenhagen);
Sannah Grüner, Project Manager, HOFOR Greater Copenhagen Utility
Among these, electric-driven heat pumps (HPs) are a promising opportunity. They can utilize low-temperature heat sources that are otherwise not exploited: geothermal energy, industrial excess heat, sewage water, seawater, groundwater, and ambient air. As electricity is becoming more CO2-neutral year by year, so are electric-driven HPs. They also help integrate renewable energy into the electricity and DH systems (sector coupling).
Due to these promising perspectives, HOFOR, VEKS, and CTR started a demo project to assist the technology development of large HPs for DH and to establish and test a state-of-the-art facility to demonstrate the feasibility and optimization potential of the technology. In 2016, there were very few large-scale HPs in Denmark (>0.5 MJ/s), and the feasibility was low due to the relatively low costs of heat production alternatives.
HPs are considered a known technology, and for a while, the tax regime in Denmark has been regarded as one of the main barriers to implementing large-scale HPs. Even though refrigeration technology has a long track record, using HPs for heating purposes is quite a different story. The project has encountered and is addressing many important development areas, including:
Finding accessible heat sources with an adequate temperature and energy potential, especially during wintertime, is challenging if surplus heat from industries is unavailable. Moreover, heat sources and the technical challenges associated are, to some degree, location-specific. For example, the seawater temperature along the Danish coasts is generally low in winter due to shallow waters. In contrast, a stable temperature all year round can be found in the deep Norwegian fjords.
Suitable locations near both heat sources and DH networks in dense city areas where the high competition for land can make or break feasibility. Close collaboration with city planning is required since land for technical purposes is rarely prioritized.
Larger DH systems often have high forward temperature demands in winter (>80 °C), which lowers COP and increases HP material costs. Furthermore, production regulation concerning the heat and power markets is a central area where design, performance, and procedures for heat pumps need to be developed.
Technology optimization and operation experience
Hands-on experience and development of competencies and know-how cannot be underestimated when introducing new technology, as HP facilities are often customized to local conditions and system demands. At the same time, it can hopefully provide a more general understanding of the technical and economic optimization potential.
Main project deliverables and goals
The project’s main deliverable is the HP facility located in the Southern part of Copenhagen Harbor next to a sewage pumping station to demonstrate the utilization of energy from both sea and sewage water. The intention is not to combine the two low-temperature heat sources but to test both heat sources individually in the same project.
Concerning technology optimization, the development of automatic control systems is underway. “HP Autotune” is a function designed ideally to regulate the facility to achieve the best COP under any system conditions, especially source and sink temperatures, based on historical operation data.
“HP Doctor” is a maintenance program, which is hoped to provide a prototype for databased rather than standardized maintenance procedures.
The project has put much effort into an extensive measuring and data-collecting system compared to a commercial facility. This supports implementing a comprehensive test program developed by the Danish Technological Institute and the partnership to learn as much as possible about the optimization potential, especially regarding the optimization of COP under varying conditions.
It will be interesting to see if the project based on this can provide a more accurate picture of the technical and economic optimization potential.
The project has several research and development activities with a more general aim. This includes a Ph.D. project and researchers from the Technical University of Denmark (DTU) who are developing models and tools to assist DH companies and suppliers with technology choices, price estimations, etc. A specific model of the demonstration HP has been made, which may be applied later in the optimization process.
Furthermore, mapping HP potential in Greater Copenhagen (technical potential in terms of heat sources at a suitable distance to the DH net) has contributed to a dialogue with the City of Copenhagen regarding potential locations for future HP facilities.
The project has been underway for some time due to a need for technical adjustments of the high-pressure compressors. A technical issue has also been encountered in other ammonia facilities in Sweden and Norway and is currently being resolved. The test program is planned to resume in the summer of 2020.