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.
In a DC production plant, one or a combination of the following production techniques are most common.
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 use heat as primary energy and not electrical power.
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 involves utilizing cold water from lakes and seas as a source of cooling. Water at temperatures 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 is then released back into the sea or lake.
To increase the efficiency and reliability, the production techniques are often combined with different kind of storage solution, 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 solution, where the overcapacity during the night is stored for use during daytime.
In a DC system the Bernoulli filter plays a vital role to protect plate heat exchanger from fouling and clogging when used for free cooling or in heat pumps with raw water from lakes, rivers and sea as natural cooling source.
Case story: 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.
The La Défense production facility feeds a fully 10 km network that runs from building to building, cooling 1.5 million square meters of office space. The water circulates in a closed circuit leaving the refrigeration units at 4.5°C and returning, after absorbing heat from the buildings, at 14.5°C. The cooling facility has a production capacity of 76.5 MW. Despite the size of the equipment used, the facility is a discrete one, located in a plain building, one that is soundproofed and well integrated into the urban landscape.
The condenser cooling circuit of the installation is cooled by water pumped from the Seine River thanks to two major pumping stations. In order to protect the plate heat exchanger (PHE) from clogging and fouling by the water from Seine River a Bernoulli Filter model BSG 500 is part of the installation. The BSG 500 is tailor-made for this installation with an outlet nozzle size of DN 400 in order to match the connection size of the PHE.
Facts and figures
Customer: Société Urbaine de Climatisation (Dalkia EDF) Location: La defense, Paris
Application: District Cooling
Filter model: BSG 500
Filtration: 2,0 mm
Operating flow: 3280 m3/h
Operating pressure: 1,5 bar g
Design pressure: 6,5 bar g