Table of Contents
- High grade (>400 °C): Recuperators, regenerators, steam generation. Medium grade (100–400 °C): Air-to-air plate or heat-pipe exchangers, absorption chillers. Low grade (<100 °C): Ventilation recovery, pre-heating water, heat pumps.
- Exhaust-to-supply air (HVAC, drying, booths) Hot water pre-heat from process cooling Exhaust-to-boiler combustion air Heat-pump upgrade of low-grade heat to useful temperature
- Operating hours (continuous beats seasonal) Temperature difference (bigger ΔT = more recoverable energy) Local fuel/electricity price Capital and maintenance cost For air-to-air ventilation and drying, payback of 1–3 years is typical; high-grade process heat can be under a year.
- Is waste heat always worth recovering? Not always. Very low temperature or intermittent streams may not justify equipment; a quick energy audit decides it. Where do air-to-air exchangers fit? They are the simplest, most cost-effective option for ventilation and low-grade exhaust, which is exactly where most buildings waste heat.
Almost every industrial and commercial process rejects heat: exhaust gases, warm water, or hot product streams. Waste heat recovery captures that energy for reuse instead of dumping it.
- High grade (>400 °C): Recuperators, regenerators, steam generation.
- Medium grade (100–400 °C): Air-to-air plate or heat-pipe exchangers, absorption chillers.
- Low grade (<100 °C): Ventilation recovery, pre-heating water, heat pumps.
- Exhaust-to-supply air (HVAC, drying, booths)
- Hot water pre-heat from process cooling
- Exhaust-to-boiler combustion air
- Heat-pump upgrade of low-grade heat to useful temperature
- Operating hours (continuous beats seasonal)
- Temperature difference (bigger ΔT = more recoverable energy)
- Local fuel/electricity price
- Capital and maintenance cost
For air-to-air ventilation and drying, payback of 1–3 years is typical; high-grade process heat can be under a year.
Is waste heat always worth recovering?
Not always. Very low temperature or intermittent streams may not justify equipment; a quick energy audit decides it.
Where do air-to-air exchangers fit?
They are the simplest, most cost-effective option for ventilation and low-grade exhaust, which is exactly where most buildings waste heat.