Two district cooling centrals in Copenhagen use seawater from Copenhagen Harbor for their cooling systems. For seven years, VLT drives controlling pumps and compressors have proven their worth, ensuring high efficiency and impressive security of supply.

Comfort, process cooling, and freezers

In chilly northern Europe, the need for cooling systems is not obvious to all. Nonetheless, there is a demand for cooling even in the frosty winter time. The Greater Copenhagen Utility (HOFOR) operates the seawater-based district cooling, which serves a wide variety of commercial customers. Business developer at HOFOR District Cooling, Admir Omeragic explains that 50 per cent of his customers use district cooling for comfort cooling, 40 per cent are using it for process cooling and 10 per cent for freezing facilities. This means that around half of the district cooling capacity is used to maintain a comfortable indoor climate in offices, shops and other places where many people share facilities. The 40% used for process cooling applies to server rooms, processing facilities or hospital equipment.

How seawater cools the city

The two district cooling centrals have a combined capacity of around 65 MW. During the winter, when seawater temperature is below 5.2 degree C, the system pumps sea water through a heat exchanger and the treated water on the output is sent out to customers as free cooling. During the warmer months of the year, the passive seawater cooling is combined with active compressor cooling. HOFOR pumps 6 degree C cooling water out to the end users and 6 degree C water is returned.

Customers save money, space and hassle

District cooling customers in Copenhagen enjoy multiple benefits – it costs less, it takes up less space and it makes no noise. “We are getting a lot of feedback from customers who are so happy to have got rid of their noisy roof-top chillers. And customers who have replaced their old air-conditioning facility with the much smaller receiver setup can now put the freed-up space to better use,” says Admir Omeragic, Business developer at HOFOR District Cooling.

The large numbers of VLT drives employed to control the pumps and compressors in the district cooling plant contribute to reducing CO2 emissions by more than 3000 tons per year.

Admir Omeragic Business developer at HOFOR District Cooling

Drives regulate pumps and compressors

An important contributor to the high efficiency of the district cooling system is the choice of high-power VLT drives to adjust the flow of all the main pumps to meet the changing cooling need.

The refrigeration compressor capacity is speed- controlled with high-power VLT drives and the HVAC system in the building uses some smaller Danfoss drives.

Contributing to high energy efficiency in HOFOR’s district cooling facilities, VLT drives also ensure an impressively high security of supply of 9.9803 per cent.

“Right from the beginning we chose to go with quality products from Danfoss in our facilities and we have never regretted that. It was easier for us to get an overview over the specifications and, on all parameters, such as maintenance, standards, efficiency and running costs, they have turned out to be optimal. We have had no problems whatsoever, even during this extremely hot summer we’ve just had, where everything has been running at full power, everything has worked perfectly,” says Admir Omeragic.