Large scale cooling using mains water

A novel method for the cooling of large scale heat generating processes in cities has been identified, namely the use of mains water. Applications include data centres, underground railways, supermarkets, hospitals and large buildings in general. Two applications for this cooling method which are currently being investigated are the cooling of London underground stations and the cooling of data centres, and this is the subject of this publication. Mains water is distributed across London through a network of pipes, and varies in temperature between 5 and 20°C during the year. For much of the year, there is potential to raise the water temperature by a few degrees, while maintaining the mains water temperature within its current maximum limit. In fact, to increase the temperature of the entire mains supply by 1°C requires heat input of the order of 100 MW. Consequently, mains water provides a large cooling resource, which could be used to replace mechanically cooled chilled water for many air conditioning system applications, especially for large scale industrial use. In London alone mains water could deliver continuous cooling of more than 600MW. London underground stations and data centres typically have cooling loads ranging from 0.5 to 5 MW, and a large number of them could have their cooling needs met by this method. The results of calculations for potential energy, carbon and cost savings by using mains water for cooling for these applications are presented, and possible methods for transferring the heat are discussed. A number of other systems to which this cooling method could usefully be applied have also been identified and are described.