The principles of district cooling are similar to district heating. The source for the cooling is often the low temperature of the deep water in a lake or the sea. Cold water from a depth of 30 to 45 metres is pumped in a constant cycle to the production sites, where it cools the transport water in the pipes of the cooling network.
The lake remains unaffected
Afterwards it is pumped back into the lake, where it quickly returns to its previous temperature. In other words, the lake's natural conditions remain unaffected. New techniques also make it possible to store the cold water underground, and to supply homes with that cold energy in summer time.
The production sites usually also have compression refrigerating machines, which provide extra cooling if the lake water is not sufficient. In this way cooling is secured at all times.
District cooling reduces CO2 emissions
Cooling systems can also use waste heat from Combined Heat and Power (CHP) units or excess heat from waste incineration plants to run absorption refrigerators for cooling during summer time, greatly reducing electricity usage. District cooling enables a CO2 reduction of up to 75 per cent compared to traditional air conditioning.
District cooling for air conditioning
There are two ways to produce central district cooling: using natural sources and generating chilled water via district heating and electricity. In both cases, Vattenfall feeds the cold water produced into its central district cooling network. The cold water circulates in a closed loop between the central cooling station and the buildings.