Corridors of heat and power

The UK government has made combined heat and power the central plank of its energy policy. Britain's Deputy Prime Minister, John Prescott, said: "This government has long been convinced of the value of CHP and community heating, both in terms of providing cost effective, reliable energy and heating, and in achieving the efficiency savings and reductions which will help us meet our environmental objectives. That is why, soon after coming to office, I launched a campaign aimed at potential users in the industry, and why I and my colleagues continue to promote the benefits of this technology wherever and whenever possible." For over 40 years, a district heating system was used to supply power and heating to various government buildings in the heart of London. It was recognised that this system was in need of refurbishment, and on 16 February, 1999, the new system was inaugurated. This scheme provides electricity and heat for 23 government buildings, including No 10 Downing Street.

A full study of the old system concluded that major refurbishment of the existing facilities was required, particularly the boiler plant. The refurbishment included new boilers, staged refurbishment of the distribution system and introduction of new controls at each building outstation.

The boiler house is located 17 m below ground level, and the installation of new plant without interrupting heat supplies was very demanding. Access was particularly difficult, and involved special arrangements.

To maintain the heat supplies during construction, the existing boilers were removed in stages, and replaced with a total of four modern shell and tube hot water boilers with dual fuel capability. These were each rated at 5.8 MWth delivering hot water to the distribution system at 160°C and 10 barg. The gas turbine is a 4.7 MWe Typhoon from Alstom, which discharges exhaust gas into a waste heat boiler rated at 8 MWth. Natural gas is used as the primary fuel, with distillate fuel used as a backup.

Noise containment played an important part in the design. Special attention was paid to containing noise breakout from the plant room by installing high specification silencing equipment in areas known to be a potential problem. This was particularly important due to the proximity of the plant room to government offices and the routing of the exhaust ductwork through the building.

Electricity from the CHP plant is sold to government departments in Whitehall at competitive rates, and any surplus is sold to an electricity company.