Waste heat recovery in screw compressors
Waste heat recovery in screw compressors is one of the key strategies for improving energy efficiency in industry. Approximately 80–90% of the electrical energy consumed by a compressor is converted into heat, representing a significant potential for useful reuse.
Utilizing waste heat from screw compressors is an excellent way to reduce CO₂ emissions and increase energy efficiency. Screw compressors generate substantial amounts of heat that can be recovered and used for space heating, domestic or process water heating, or other industrial applications.
Advantages of Waste Heat Recovery
• Reduced CO₂ emissions – Lower demand for additional energy sources means reduced fossil fuel consumption and fewer emissions.
• Lower energy costs – Reusing compressor heat reduces the need for other heating energy sources.
• Sustainability – Companies that recover waste heat can significantly improve their environmental footprint.
How Waste Heat Is Generated in Screw Compressors
Screw compressors operate by compressing air through the rotation of intermeshing screws. During this process, a large amount of heat is released due to:
• Air compression – When air is compressed, it heats up.
• Friction and mechanical operation – Moving components produce heat through friction.
• Oil cooling – The oil in the compressor is cooled by a fan and an oil/air heat exchanger. The heated air can then be used for space heating with warm air.
Alternatively, the compressor may include an oil/water heat exchanger (recuperator), which uses water to cool the oil. The heated water can then be used to preheat the return flow in heating systems, heat domestic water, or preheat process water.
Methods of Waste Heat Utilization
1. Water Heating
One of the most efficient ways to utilize waste heat is water heating via heat exchangers, which can be applied for:
• Domestic hot water (sinks, showers, kitchens)
• Industrial processes (cleaning, material preheating, pasteurization)
• Building heating (radiator heaters or underfloor heating systems)
Example: A 75 kW compressor can provide enough heat to warm several thousand liters of water per day.
2. Space Heating
Compressors generate hot air that can be directed into the ventilation system.
• Direct heating – Warm air from the compressor is directed into workspaces.
• Indirect heating – Through heat exchangers, the recovered heat warms water that circulates in the radiator system.
3. Drying and Industrial Processes
Industries requiring drying processes (wood, textile, food, etc.) can use waste heat for:
• Preheating drying air
• Drying materials and products
• Thermal processing of products
4. Integration with District Heating Systems
In large industrial facilities, excess recovered heat can be fed into district heat networks, further reducing CO₂ emissions.
How Much Can Be Saved?
Up to 70% of waste heat can be recovered and reused.
CO₂ emissions can be reduced by dozens of tons per year.
Example Calculation
To estimate savings from waste heat recovery on a 75 kW screw compressor, we consider the following assumptions:
• Waste heat potential: About 80–90% of the electrical energy consumed by the compressor is converted into heat.
• Recoverable heat: Up to 70% of that heat can be utilized for water heating, space heating, or industrial processes.
• Operating hours: Compressor operates 8 hours/day, 250 days/year.
Available Heat Calculation
• Electrical energy consumption:
75 kW × 8 h/day = 600 kWh/day
600 kWh/day × 250 days = 150,000 kWh/year
• Waste heat available (90% of input energy):
150,000 × 0.9 = 135,000 kWh/year
• Usable heat at 70% system efficiency:
135,000 × 0.7 = 94,500 kWh/year
Conclusion
By recovering waste heat from a 75 kW screw compressor, it is possible to achieve significant annual energy savings and reduce CO₂ emissions by almost 19 tons each year.
Waste heat recovery is therefore a smart investment — improving energy efficiency, reducing environmental impact, and lowering operating costs, while contributing to a more sustainable industrial future.
Inquiry
OMEGA AIR d.o.o. Ljubljana
Cesta Dolomitskega odreda 10
1000 Ljubljana
Slovenia
Cesta Dolomitskega odreda 10
1000 Ljubljana
Slovenia
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