District cooling entails the production and circulation of chilled water to multiple buildings through a network of insulated underground pipes. Cooled water is pumped from the central plant through the pre-insulated underground pipes connected to the building connections, which is called Energy Transfer Station (ETS). In the ETS, the coolness of the chilled water is used to chill down the water of the building through a Plate Heat Exchanger (PHE).
The PHE is composed of hundreds of parallel, vertical, thin, metal plates very close to each other. The cold water from the cooling plant flows between two of the plates, and the water returning from the building flows between the adjacent two plates, electronically controlled pumps push the building’s cool water through the building piping into fan coil units, where fans push the ambient air against cold coils, thus cooling down the air and pushing it into the room.
The water leaving the fan coil units, after having dissipated its coldness in the ambient air, is returned to the PHE a few degrees warmer to be re-cooled through exchanging its warmth with the coldness of the water pumped from the cooling plant. The warm water from this process, then flow back to the plant through a parallel network of reinsulated underground pipes, to be re-chilled, and then re-pumped back to the building, creating a closed circuit.
Treated Sewage Effluent (TSE) in the Middle East and other Gulf Countries is a resource that is under exploited Qatar Cool’s plants are equipped to use TSE in their plants, and have switched from portable water to TSE in the West Bay plants, in conjunction with local authorities. Qatar Cool will use the TSE for the cooling towers of the plants.
District Cooling systems allow for significant economies of scale as a result of the use of a single large cooling plant to replace multiple individual chiller units. Thus, In principal, the larger the central plant the bigger the potential gains.
District cooling follows a simple process as illustrated below
- Water is chilled at a central cooling plant
- Chilled water is pumped through a network of underground insulated pipes to customers’ buildings
- An air-conditioning water system inside the customer’s building circulates the chilled water
- Air is then pumped through the chilled water piping of the air-conditioning system producing cold air
Components of the district cooling system:
- Central cooling plant
- Pipe Distribution Network (PDN)
- Energy Transfer Station (ETS) or customer connection point.