District cooling
District cooling (DC) is based on cold water being distributed in a network of pipes to provide cooling to a number of buildings like offices, hospitals, industries etc. The cold water pumped around the district cooling network is used to cool the air circulating in the properties´ ventilation system. The same water is then fed back to the production plant to be cooled again.
Increased efficiency and reliability
In a DC production plant, one or a combination of the following production techniques are most common.
Absorption chiller
Surplus heat from i.e. industrial processes or power production may be used for cooling production by integration of an absorption chiller to the plant since absorption chillers primarily use heat as primary energy and not electrical power.
Heat pump
The use of heat pumps is the most common way of producing district cooling since they are able to produce both heating and cooling at the same time.
Free cooling
Free cooling involves utilizing cold water from lakes and seas as a source for cooling. Water at temperatures of around 4 °C is pumped and used to cool the water circulating in the district cooling network by means of heat exchangers. The return water is then released back into the sea or lake.
To increase the efficiency and reliability, the production techniques are often combined with different kinds of storage solutions, such as seasonal storage like an aquifer solution where free cooling in winter is stored for use during the summer period or night-to-day storage, often as ice or water storage solutions, where the overcapacity during the night is accumulated for use during daytime.
In a DC system the Bernoulli filter plays a vital role protecting plate heat exchangers from fouling and clogging when used for free cooling. The same goes for heat pumps using raw water from lakes, rivers and seas for natural cooling source.
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Case:
La Défense
In Paris some of the first and also the largest European District Cooling systems exist. In the area of La Défense, Europe’s largest business district SUC, Société Urbaine de Climatisation, a subsidiary of International Group Dalkia, operates a district cooling system that supplies chilled water to be used in air conditioning systems in the buildings. SUC is also responsible for the production and distribution of cooling in the towns of Coubevoie and Puteaux, along the Seine River.