A two-stage ammonia (R717) heat pump from Sabroe, a Danish subsidiary of international manufacturer Johnson Controls, will play a pivotal role in Germany’s first large-scale seawater district heating system, located in the town of Neustadt in Holstein.
According to a statement from the manufacturer, the new system will use water from the Baltic Sea to provide heating and hot water for 700–800 households, as well as a hotel and local businesses, in the city’s new harbor district.
“The seawater heat pump is the essential element of our climate-friendly heat supply concept,” said Thomas Anthoni, Project Manager for Heating at Stadtwerke Neustadt in Holstein (SWNH), the municipality’s utility provider. “With this solution, we are implementing a flagship project for the energy transition.”
Sabroe’s DualPAC heat pump was delivered in December 2023 and is expected to be operational in mid-2025, noted SWNH. Development of the district heating network is slated to continue into 2026.
“The seawater heat pump is the essential element of our climate-friendly heat supply concept. With this solution, we are implementing a flagship project for the energy transition.”
Thomas Anthoni, Project Manager for Heating at SWNH
‘Ideal’ solution
The DualPAC heat pump’s design, which allows it to achieve high-temperature lifts, makes it “ideal” for district heating applications, according to Johnson Controls.
The heat pump offers a heating capacity of 700kW (199TR) and water flow temperatures of up to 72°C (161°F). With a COP of at least 3, the unit will provide “great efficiency,” said SWNH in a previous announcement about the project.
The heat pump will be supported by additional systems during winter months – when seawater temperatures are colder – and periods of peak demand, including a nearby waste incineration plant and heat storage facility.
Decarbonizing heating
Funded by Germany’s Federal Ministry of Economic Affairs and Climate Protection, the Neustadt project is viewed as a model for decarbonizing heating infrastructure.
“Most of the world’s heating needs today are met with direct fossil fuel combustion,” explained Johnson Controls. “To decarbonize buildings and maintain a reliable grid, electrifying these systems with heat pumps is key.”
Compared to conventional heating methods, heat pumps consume roughly one-third of the energy, with the potential to generate up to eight times the energy they use.
“To decarbonize buildings and maintain a reliable grid, electrifying these systems with heat pumps is key.”
Johnson Controls
“Heat pumps are a crucial technology in the energy transition and provide an efficient and sustainable alternative to gas and oil heating,” said David Emin, General Manager for Johnson Controls, Germany. “Our cooperation with the Neustadt in Holstein municipality shows we can use the technology to harness one of the world’s most abundant and natural resources. We are proud to bring our expertise to this innovative project that is setting an example for carbon neutrality in Europe and beyond.”
With demand for heat pumps rising across Europe, Johnson Controls has recently expanded manufacturing facilities in Denmark, France and Turkey and is enhancing its product line to provide high-temperature units for broader applications.
