Heat recovery is the
collection and re-use of heat arising from any process that would
otherwise be lost. The process might be inherent to a building,
such as space heating, ventilation and so on, or could be something
carried out as part of business activity, such as the use of ovens,
furnaces and the like. Heat recovery can help to reduce the overall
energy consumption of the process itself, or provide useful heat
for other purposes.
Ventilation systems bring cool fresh air into a building using
fans in Air Handling Units (AHUs). The AHUs also contain heating
coils to allow the fresh air to be raised to the required
temperature by the buildings boiler. The air continues to be heated
by the occupants and equipment in the room and all this heat energy
is lost when the air is extracted and dumped into the
The addition of heat recovery means that some of the heat
contained within the extract air can be recovered. The heat energy
is passed into the incoming fresh air effectively pre-heating it
and meaning the boiler needs to add less heat. The two air streams
need not mix directly to allow the transfer of heat.
Sources of 'waste' heat
You're likely to have sources of 'waste' heat in your building
whether you are in an office (e.g. from the heating or ventilation
systems) or a factory (e.g. in an industrial drying process or
compressed air system).
Waste heat from the following common sources often presents
opportunities for cost-effective heat recovery:
- ventilation system extracts
- boiler flue gases
- boiler blowdown
- air compressors
- refrigeration plant
- high temperature exhaust gas streams from furnaces, kilns,
ovens and dryers
- hot liquid effluents
- power generation plant
- process plant cooling systems.
Use the Heat
recovery checklist (CTL142) to help you decide whether your
building is likely to have any of these types of sources.
Improving the energy efficiency of heat
Where it's possible, the most cost-effective use of waste heat
is usually to improve the energy efficiency of the heat generating
Common uses (or 'sinks') for recovered heat include:
- pre-heating combustion air for boilers, ovens, furnaces, and so
- pre-heating fresh air used to ventilate the building;
- hot water generation, including pre-heating boiler feed
- space heating;
- other industrial process heating/pre-heating;
- power generation.
In most cases, heat recovery is far more efficient when the heat
source and heat sink are coincident - meaning they are physically
close together and occur at the same time.
Refer to the Heat
recovery overview guide (CTG057) for more information on the
various types of heat recovery technology and techniques and how
you can apply them to your business.
Further guidance on heat recovery systems
We have the following publications available for free
Energy efficiency support
If you'd like to improve energy efficiency of your organisation,
see our services to find out how we can
help. This includes financing and implementation support for
organisations seeking to invest in energy efficient equipment, for
more details visit our Implementation &
Visit our regional web pages for Scotland, Wales and Northern Ireland to get details
of our Government funded support.