Heating & Cooling pipes
Heating and cooling pipes are used to link buildings together to form a district energy network to distribute the thermal energy from a decentralised energy generation station.
Tradiationally the pipework used in these networks is buried in the ground and pre-insulated, however, the civil costs associated with this are high and if possible the networks should be laid within buildings, for example in underground car parks.
Heating networks typically fall into two categories, low temperature (a flow temperature of circa 80°C) and high temperature (a flow temperature of circa 100 to 120°), although there are temperature in between these and each network must be designed to be compatible with the connected buildings and take into account the local topography.
If at all possible the use of a lower temperature network is recommended as this significantly reduces heat losses, increases the energy which can be used for lower temperature sustainable energy sources, and lower cost piping systems can be utilised.
For lower temperature systems which operate with flow temperatures which are below 95°C it is possible to utilise plastic pre-insulated pipework which is manufactuered in rolls of up to 100 metres. Although this pipework can only be used for heat loads up to a certain size.
Above this size, or where the use of plastic pipe is not possible then typically 12 metre lengths of pre-insulated steel pipework are used with bonded insulation which can contain alarm wires to detect moisture.
For cooling networks the pipe systems described above also apply, however to reduce costs further some practitioners are using more innovative types of materials.
It is important to remember that as cooling networks tradiationally operate with a much lower temperature difference between flow and return, pipe sizes are much larger than those for the same heat load, which typically operates with a delta T of more than five times that of a cooling network. This issues has a considerable impact on network costs and spatial planning