What is district cooling?
As the name implies, district cooling is all about cooling produced elsewhere. Instead of each building having its own cooling plant, the cold air is supplied by a central unit which can be operated using lots of different resources and effective methods. Both the property owner and the environment benefit from this.
Quite simply, district cooling is simple, safe, comfortable cooling distributed in a closed circuit with minimal environmental impact.
How it works
District cooling is based on cold water being distributed in a network of pipes in the same simple ways as district heating. The technology itself is simple. You cool water in a location and then feed it through a network of pipes to homes, offices, hospitals, industry and other environments in need of cooling. The cold water pumped around the district cooling network is used to cool the air circulating in the properties’ ventilation systems. The same water is then fed back to the production plant to be cooled again.
The temperature of the water fed to properties is around 6 degrees, while the return water is in excess of 16 degrees. The return water is heated as much as possible while premises and processes are being cooled.
At the property, a heat exchanger is often used to link up to the building’s cooling system. Adaptation to an existing system requires just minor adjustments.
Many different methods
District cooling is produced using a range of very different techniques which are often combined in order to utilise local conditions as efficiently as possible. Producing district cooling in conjunction with district heating is especially smart, because we often need cooling when we least need heating.
Free cooling involves utilising cold water from lakes, seas or other waterways. Water at a temperature of around 4 degrees is pumped and used to cool the water circulating in the district cooling network by means of heat exchangers. The return water – now at a temperature of 12–16 degrees – is then released back into the sea or lake. Snow collected in winter can also be used.
Absorption cooling is another technique utilising the thermal energy generated in the production of district heating and so can use waste heat from industry or waste incineration. The water to be used for the district cooling is cooled by vaporising water at a temperature of around 3 degrees. Water can be boiled at such a low temperature because there’s a massive underpressure in the system.
Heating pumps are able to produce both heating and cooling at the same time, and currently this is the most common way of producing district cooling in Sween. Many district heating plants are already using heating pumps so as to utilise the heat present in purified waste water, for example. Heating pumps are based on a process reminiscent of the process used in fridges and include powerful compressors.
District cooling in future
In today’s world, more energy is used to produce cooling than is used to produce heat. Here in Sweden, more and more people are discovering that district cooling is a simple, safe and easy way to create an indoor environment offering supreme – and consistent – comfort. So the future’s looking bright for district cooling, and a number of locations are currently evaluating their options for introducing district cooling. More or less all current producers of district cooling are planning expansion.