Aalborg University Hospital's thalassothermal system

Using lake water to heat and cool a new hospital

The cement manufacturer Aalborg Portland uses massive quantities of chalk in its production process. Many excavations have over time formed a chalk lake at the company’s facilities, and this now provides district cooling for the new Aalborg University Hospital. The water is transported approximately 3.5 km to the hospital’s cooling distribution centre to cool patient rooms, personnel and clinical facilities and medical equipment.

Artelia provided client consultancy for the lake water heat exchanger building and the cooling distribution centre, each of which plays an important role in the comprehensive system.


In September 2018, the utility company Aalborg Forsyning committed to providing a more sustainable cooling system for the new Aalborg University Hospital (NAU), contributing to the region’s climate action plan and its targets for reducing CO2 emissions. The idea was to use cold water from the sea or a lake (thalassothermics). The solution finally chosen was to draw from the chalk lake at Rørdal, an artificial reservoir created when Aalborg Portland exploited this quarry.

The water near the bottom of the more than 30 metre deep lake has a temperature ranging between 4 and 14 degrees throughout the year. This is a resource that provides electricity savings of approximately 80 % compared with an ordinary cooling system and a total of 500 to 700 tonnes of CO2 saved per year.
As a client consultant to Aalborg Forsyning Artelia Denmark prepared the tender documents and supported its client throughout the project development process. The installation is designed to provide a capacity of 7.3 MW, which can be extended to 11 MW. This thalassothermal solution emits significantly less carbon than other heating and cooling systems.