Where waste heat is an opportunity
Heat recovery is especially cost effective if you use both heating and cooling systems, such as food processing. It can increase process heat and refrigeration capacity, avoiding capital investment in new systems.
The most common sources of waste heat in business are:
- boiler exhaust
- refrigeration systems
- air compressors
- hot waste water streams
- other hot gas discharges
- heat from your heated product(s) output.
How to know if heat recovery makes sense
The hotter the waste stream is compared to its surroundings, the easier it will be to re-use it. Recovered heat must ideally be hotter than the temperature you need it to be at the point of use for direct recovery (heat exchanger).
To decide if it’s practical and economic, also consider:
- The type of waste heat stream. It’s more cost-effective to recover heat from a liquid stream than a gas stream.
- The availability of heat. Ideally, there would be a good match between when your waste heat is available and when you need it. Otherwise you need to store it, for example in a hot water tank.
- How far the waste heat has to travel impacts piping costs.
- Effects on the original process and capacity of heat systems.
- Cost of energy substituted.
- Capital costs of the heat recovery system.
Waste heat at lower temperature can still be recovered
If the waste heat stream is at a lower temperature than you need, there are two options:
- Pre-heating. The temperature might not be enough to do all the heating work, but a lot of energy can still be saved by using heat for pre-heating, then finishing the work with another energy source.
- Heat pumps. If the amount of waste heat is large enough, it can be economic to use a heat pump to produce high-grade heat (high temperature) from low-grade heat (lower temperature). High temperature heat pumps able to produce heat up to 90°C are commercially available and a mature technology
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Co-funding for heat recovery projects
If you emit more than 10,000 tonnes CO2-e a year on stationary energy, you may be eligible for co-funding for an energy audit, feasibility study or systems optimisation related to heat recovery. Larger energy users can also be co-funded for industrial design advice.