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Last month, a new district heating (DH) project, the London Thames Gateway Heat Network, was the cover story of PE. DH, which uses waste heat, is not a recent development – the earliest book on the subject held by the Institute library dates to 1915.
The first appearance of the elements of DH came in the late 18th century, when centralised boilers were often used to heat factories. In the 1830s, waste heat from factories had been used to heat public baths and proposals were made to heat workers’ houses in the same way.
In 1877, the first commercially viable DH system was created by Birdsill Holly at Lockport, New York. The heat, in the form of steam, was generated by a large central boiler. His system was exported around the world, and hundreds of systems were installed.
In the UK, serious interest in DH did not occur until the 1940s. Prior to this, coal was cheap and plentiful, and the cost and wellbeing of labour to extract it, as well as the issue of air pollution, was not really considered. Coal fires, with a thermal efficiency of around just 10%, were therefore the standard means of providing warmth in individual houses. Many postwar housing estates used district heating. The Pimlico District Heating Undertaking, which used waste heat from Battersea Power Station, was the first installed, in 1950.
Following the oil crises of the 1970s, there was another wave of interest in district heating. Although this resulted in a number of systems being installed in the UK, much of the interest disappeared once oil prices fell.
Denmark reacted very differently, and by 2000 58% of all Danish households were supplied through DH schemes. Prior to 1973, almost 100% of the country’s heat had been generated through imported fossil fuel but the first oil shock prompted it to move towards a position of energy security.
The Danish government quickly built on a long history of district heating in the country, where the first system had been installed in 1901. The heating supply in all areas was planned, and as much combined heat and power as possible was installed. In tandem with a programme of insulating buildings it resulted in a 50% fall in requirements for space heating per person.