Case
District heating
Energy efficiency in buildings
Heat pumps
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ProjectZero is Sønderborg’s cross-sector climate partnership, uniting citizens, businesses, utilities and the municipality to achieve a CO₂-neutral energy system by 2029 - and to serve as a living blueprint for cities around the world.
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Hospitals are among the most energy-intensive public buildings. Sønderborg Hospital relied on outdated gas boilers for heating while simultaneously needing large amounts of cooling for medical scanners, technical equipment, and operating rooms. This meant high CO₂ emissions, wasted excess heat, and an energy system that did not take advantage of the obvious synergy between heating and cooling demands.
The challenge was to replace fossil-based heating with a low-carbon solution that could both improve energy efficiency and indoor comfort – without compromising the hospital’s critical operations.
Watch Dorte Callesen, Head of Press at Sønderborg Hospital, explain the hospital’s green journey.
Sønderborg Hospital replaced gas boilers with two high-efficiency heat pumps that provide both heating and cooling. The system captures excess heat generated during cooling processes and reuses it for space heating and domestic hot water.
This allows the hospital to cover 91 % of its heating demand with recovered excess heat, while also providing comfort cooling that improves the indoor climate for patients and staff.
When the hospital produces more excess heat than it can use itself, the surplus is supplied to the local district heating network. In this way, the hospital functions as both an energy consumer and supplier, demonstrating practical sector coupling and smart energy flow optimization in a large public institution.
The heat pump solution has eliminated gas from Sønderborg Hospital’s heating supply and significantly reduced its carbon footprint. The hospital is now 91 % self-sufficient in heat and supplies approximately 15,800 MWh of excess heat to the local district heating grid each year – enough to heat around 877 Danish households.
By utilizing excess heat that was previously wasted, the project reduces overall heat production in the Sønderborg area by 28,300 MWh annually.
In addition to the climate benefits, the system improves indoor comfort and temperature regulation for patients and staff. The solution is scalable and replicable, offering a proven blueprint for how hospitals and other large institutions worldwide can decarbonize their heating systems while strengthening local energy networks.
The heatpumps bring a range of major benefits. Top of the list? They push fossil fuels out of the picture.
