While electricity is a very efficient and an easy fuel to use, it’s generation exploits less than half the energy content of the primary fuel.
Combined heat and power uses primary fuel more effectively, which is why it is well regarded by the Government as a measure to reduce carbon-dioxide emissions. Together with a secure distribution system, which enables the flexible use of more fuels, this forms the sound foundation of a community heating system to be created.
A major scheme in Milton Keynes was initiated to achieve just this.
PPSL was engaged by Xergi Services/Thameswey Limited to design, supply and install a district heating network in the Avebury Boulevard area of Central Milton Keynes. PPSL carried out associated civil works and the installation of electricity cables as private wires. The network provides heat and power to The Hub, a development comprising of hotels, commercials, apartments and offices. It also supplies electricity and heat to a proposed new residential area in the west end of Central Milton Keynes. The area served has a radius of some 1.5 km with a private-wire network to distribute electricity.
The distribution system was designed to be extended and supply further consumers in the area.
Normal power stations convert only 40% of the energy content of primary fuel into electricity and huge quantities of heat are rejected. CHP makes use of much of that rejected heat, so that over 70% of the potential of the primary fuel is utilised.
A means of using the rejected heat is needed, which is often, as at Milton Keynes, a district heating network. Such a district heating network is highly effective in a mixed-use area that includes, for example, residential, schools/colleges and businesses.
The district heating system is designed for a flow of 85ºC with return temperatures of 50ºC.
Commercial and residential buildings in the area covered by the scheme do not have individual boilers. Instead, they are linked to the district heating system but individually separated by plate heat exchangers, converting the hot water into use for the heating and hot domestic water.
The Milton Keynes scheme is an impressive example of how to make use of a community district heating and electricity system.