In the capital of Denmark, district cooling results in close to 70% reduction in CO2 emissions
Increasing demand for cooling
There is an increasing demand for air conditioning and cooling in Copenhagen as in many other cities around the world. The Copenhagen utility company, HOFOR, has built a district cooling system, which consists of a distribution net and two cooling plants. The district cooling system uses seawater to chill down the water supplied to the customers. The system supplies commercial buildings such as banks, department stores, and offices as well as cooling for data centres and other processes all year round.
Therefore, HOFOR can supply the increased demand for cooling in Copenhagen and help reduce CO2 emissions by up to 30,000 tonnes each year. The cooling system now supplies the centre of Copenhagen with cold water, and the pipe system is expanded in order to supply more customers in the future. HOFOR’s district cooling activities are the biggest of their kind in Denmark. The first cooling plant was opened in 2010, the second plant in 2013, and the system is still under expansion. From 2015 until 2020, it is the ambition to expand district cooling further by doubling the amount of customers and thereby contribute further to Copenhagen’s target to become CO2- neutral in 2025.
Cooling is produced centrally in three different ways:
In winter months, the chilled water to the customers is produced by using seawater. The seawater is pumped into the cooling plant through a pipe from the harbour. The seawater temperature is a maximum of 6 °C, when it is used directly to cool down the water for the customers. This is known as zero-carbon cooling. However, a small amount of electricity is used when pumping seawater into the cooling plant. In summer months, when the seawater is not sufficiently cold, energy must be used to chill down the water. Seawater is used to increase the efficiency of the other installations. Using seawater to remove the heat from the machines reduces electricity consumption by up to 70% compared to a local compressor.
Also during summer months, waste heat from the power plants is used for cooling. This method is known as absorption cooling and is only used when there is waste heat from the power plants available. The absorber minimises the CO2-emission.
Author: Henrik Lorentsen Bøgeskov, Head of District Cooling, HOFOR