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District cooling is basically the same as district heating. Instead of supplying heating and possibly domestic hot water, chilled water is supplied instead.
The chilled water is typically generated via a chiller(s) (refrigeration cooling) or a cooling tower(s) (evaporative cooling) the chilled water is then typically sent through fan coil units within the building to cool the air during periods of high ambient temperatures.
The equipment required on the cooling networks along with the benefits of the district approach are the same for cooling as they are for heating. The benefits of amalgamating the loads, reducing demand peaks apply to cooling networks as well as heating networks. Again, the district approach allows for greater utilisation of renewable cooling sources, such as the free cooling associated with lake and rivers.
District cooling also reduces the ‘heat island’ effect of multiple individual air conditioning units. Waste heat from these individual AC units contributes to the higher ambient temperatures seen in most cities with high individual AC unit use. District cooling plants can be located remotely from the dwellings and therefore the heat island effect close to dwellings is removed. Generally, for cooling, the capacities, in terms of both power and flow tend to be greater on cooling applications than heating applications. The flow is higher, due to the much smaller delta T associated with cooling circuits. Whereby with heating applications, delta T’s of 20 to 40 degrees C are common, on chilled applications, delta T’s of 8 to 10 degrees C are typical. This much lower delta T dictates higher volume flow rates for a given power output. The result is larger plate heat exchangers, pipes and pumps. The component types and hydraulic layout remains the same, but the sizes are generally larger. Due to the likelihood of condensation, pipework, valves, PHE’s and all associated equipment installed on the chilled network needs to be vapour sealed and it is common to see drip trays and condensation drains on the fan coil units.
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