Compressor waste heat turned into process hot water
How an engineering plant with three 75 kW screw compressors can upgrade oil-cooler heat to 85 °C process hot water with a water-source heat pump, and what it saves against a diesel-fired hot-water generator.
▶Video: Waste-heat recovery heat pumps
V10 · 2–2.5 minLifting warm water from condensers, effluent and process cooling to useful heat
Video coming soon01Problem statement
- Most compressor power ends up as heat. Around 90% of the electricity a screw compressor draws leaves as heat in the oil cooler and is dumped to air or a cooling tower.
- Direct recovery is too cool. Recovered oil-cooler water at 50–60 °C is too cold for washers and feedwater, so it is usually left unused.
- Hot oil shortens compressor life. In Indian summers oil coolers struggle, and high oil temperature trips compressors and degrades the oil.
- Losses between fuel and process. Burning diesel in a boiler or heater and distributing the heat loses a quarter or more of the fuel's energy before it reaches the process.
- Compliance, safety and handling. Fired equipment brings boiler inspections, fuel storage and unloading, flue emissions and an attendant on every shift.
02Use case
The reference plant is an auto component factory with three 75 kW oil-injected screw compressors running round the clock. It uses hot water for parts washers, boiler make-up preheat and the canteen.
| Heat user | Process temp. | Basis | Heat, kWh/day |
|---|---|---|---|
| Parts washer tank make-up | 30 → 65 °C | 6,000 L/day, 30 → 65 °C | 244 |
| Boiler make-up water preheat | 30 → 80 °C | 10,000 L/day, 30 → 80 °C | 581 |
| Canteen and washroom hot water | 30 → 60 °C | 3,000 L/day, 30 → 60 °C | 104 |
| Storage and pipework standing losses | – | about 5% | 46 |
| Total useful heat | 975 | ||
Averaged over 20 running hours, the heat pumps need about 49 kW.
03P&ID
Tags: HP heat pump, TK tank, SG steam generator, P pump, PHE plate heat exchanger, TCV temperature control valve, TIC temperature indicating controller (panel), TT temperature transmitter, MT moisture transmitter, PT pressure transmitter, LT level transmitter, FS flow switch, NC normally closed. Process fluids are heated through their own exchanger, coil or jacket.
04Solution
System description
- 2 × SE-WWUHT-27 (54 kW total) (SE-WWUHT water-source, R245fa) delivering 85 °C, covering the day's 975 kWh in about 18.1 running hours.
- A 2,000 L insulated storage tank decouples the heat pumps from the process peaks.
- Heat source: compressor oil-cooler water at about 55 °C. Taking heat out of the oil-cooler loop lowers oil temperature and reduces the load on compressor cooling fans.
- The diesel-fired hot-water generator stays connected behind a normally closed valve as standby.
- A heat-recovery PHE on each compressor oil circuit heats a closed water loop to about 55 °C, which feeds the heat pump evaporator.
- The heat pump lifts this to 85 °C and charges the storage tank serving the washers, boiler make-up and canteen.
- The compressor's own oil cooler stays in circuit, so the compressors are protected whether or not the heat pump is running.
Selected equipment
| Model | SE-WWUHT-27 × 2 |
|---|---|
| Heating capacity | 27 kW each, 54 kW total |
| COP | 2.93 at the data sheet's rated condition (60/55 °C source water) |
| Power input | about 18.4 kW total at rated conditions |
| Rating | water or steam to 120 °C, R245fa |
| Supply temperature | 85 °C |
| Storage | 2,000 L insulated tank |
Ratings from the Sunniva TDS 2026 data sheets.
Control philosophy
TT-101 at the tank top starts the heat pump below 80 °C and stops it at 85 °C, provided the source loop is above 45 °C. A three-way valve on each compressor oil line keeps oil temperature within the maker's band, sending excess heat to the original cooler. TIC-201, TIC-202 and the canteen mixing valve control each user. The diesel generator remains as standby.
05Energy saving and ROI
Change any input to match a customer's site. Defaults are typical Indian prices for October 2026. The installed cost is a placeholder; replace it with the actual quotation.
| Existing | Heat pump | |
|---|---|---|
| Daily consumption | – | – |
| Annual energy cost | – | – |
| CO₂ per year | – | – |
06Benefits
Heat that is already paid for
The compressors produce this heat anyway. The heat pump only adds the lift to a useful temperature.
High efficiency
A warm 55 °C source gives a much higher COP than an air-source unit making the same water.
Cooler, longer-lived compressors
Steady heat removal keeps oil temperature down in summer and reduces high-temperature trips.
Lower energy cost
Each kWh of electricity delivers about 2.9 kWh of heat at the required temperature, against well under one kWh of useful heat per kWh of fuel burnt.
No flame on site
No burner, flue or fuel tank for this duty, and no fuel deliveries to schedule.
Built-in redundancy
Several machines share the load. If one is serviced, the others and the storage carry most of the day, with the existing heater in reserve.
07Engineering pointers
Site data to collect
- Compressor ratings, load profile and running hours
- Oil cooler type and existing heat recovery
- Hot water users, volumes and temperatures
- Monthly diesel use for hot water
- Present fuel or electricity use and monthly bill
- Sanctioned electrical load and spare capacity
- Space for the heat pumps and storage, with service access
Design notes
- Compressor warranty. Agree the heat-recovery tie-in and oil temperature limits with the compressor service provider before installation.
- Match source and demand. Heat is only available while compressors are loaded. Size storage so washers and canteen still have hot water during low-air periods.
- Electrical. About 18 kW of heat pump input at rated conditions, plus pumps and fans. Check spare sanctioned load before ordering.
- Source stream. The source must give up roughly two-thirds of the heat delivered. Confirm its flow and temperature over a full production day, and filter it before the evaporator.
- Water quality. Scale forms quickly above 60 °C. Use softened make-up and keep the heat pump loop closed, with process fluids on the far side of an exchanger or coil.
Service and warranty
Sunniva has supplied 5,000+ heat pumps since 2012, with nine service technicians across India, including remote sites such as Leh. All components carry a one-year warranty.
Talk to us
Compressor waste heat turned into process hot water
How an engineering plant with three 75 kW screw compressors can upgrade oil-cooler heat to 85 °C process hot water with a water-source heat pump, and what it saves against a diesel-fired hot-water generator.
▶Video: Waste-heat recovery heat pumps
V10 · 2–2.5 minLifting warm water from condensers, effluent and process cooling to useful heat
Video coming soon01Problem statement
- Most compressor power ends up as heat. Around 90% of the electricity a screw compressor draws leaves as heat in the oil cooler and is dumped to air or a cooling tower.
- Direct recovery is too cool. Recovered oil-cooler water at 50–60 °C is too cold for washers and feedwater, so it is usually left unused.
- Hot oil shortens compressor life. In Indian summers oil coolers struggle, and high oil temperature trips compressors and degrades the oil.
- Losses between fuel and process. Burning diesel in a boiler or heater and distributing the heat loses a quarter or more of the fuel's energy before it reaches the process.
- Compliance, safety and handling. Fired equipment brings boiler inspections, fuel storage and unloading, flue emissions and an attendant on every shift.
02Use case
The reference plant is an auto component factory with three 75 kW oil-injected screw compressors running round the clock. It uses hot water for parts washers, boiler make-up preheat and the canteen.
| Heat user | Process temp. | Basis | Heat, kWh/day |
|---|---|---|---|
| Parts washer tank make-up | 30 → 65 °C | 6,000 L/day, 30 → 65 °C | 244 |
| Boiler make-up water preheat | 30 → 80 °C | 10,000 L/day, 30 → 80 °C | 581 |
| Canteen and washroom hot water | 30 → 60 °C | 3,000 L/day, 30 → 60 °C | 104 |
| Storage and pipework standing losses | – | about 5% | 46 |
| Total useful heat | 975 | ||
Averaged over 20 running hours, the heat pumps need about 49 kW.
03P&ID
Tags: HP heat pump, TK tank, SG steam generator, P pump, PHE plate heat exchanger, TCV temperature control valve, TIC temperature indicating controller (panel), TT temperature transmitter, MT moisture transmitter, PT pressure transmitter, LT level transmitter, FS flow switch, NC normally closed. Process fluids are heated through their own exchanger, coil or jacket.
04Solution
System description
- 2 × SE-WWUHT-27 (54 kW total) (SE-WWUHT water-source, R245fa) delivering 85 °C, covering the day's 975 kWh in about 18.1 running hours.
- A 2,000 L insulated storage tank decouples the heat pumps from the process peaks.
- Heat source: compressor oil-cooler water at about 55 °C. Taking heat out of the oil-cooler loop lowers oil temperature and reduces the load on compressor cooling fans.
- The diesel-fired hot-water generator stays connected behind a normally closed valve as standby.
- A heat-recovery PHE on each compressor oil circuit heats a closed water loop to about 55 °C, which feeds the heat pump evaporator.
- The heat pump lifts this to 85 °C and charges the storage tank serving the washers, boiler make-up and canteen.
- The compressor's own oil cooler stays in circuit, so the compressors are protected whether or not the heat pump is running.
Selected equipment
| Model | SE-WWUHT-27 × 2 |
|---|---|
| Heating capacity | 27 kW each, 54 kW total |
| COP | 2.93 at the data sheet's rated condition (60/55 °C source water) |
| Power input | about 18.4 kW total at rated conditions |
| Rating | water or steam to 120 °C, R245fa |
| Supply temperature | 85 °C |
| Storage | 2,000 L insulated tank |
Ratings from the Sunniva TDS 2026 data sheets.
Control philosophy
TT-101 at the tank top starts the heat pump below 80 °C and stops it at 85 °C, provided the source loop is above 45 °C. A three-way valve on each compressor oil line keeps oil temperature within the maker's band, sending excess heat to the original cooler. TIC-201, TIC-202 and the canteen mixing valve control each user. The diesel generator remains as standby.
05Energy saving and ROI
Change any input to match a customer's site. Defaults are typical Indian prices for October 2026. The installed cost is a placeholder; replace it with the actual quotation.
| Existing | Heat pump | |
|---|---|---|
| Daily consumption | – | – |
| Annual energy cost | – | – |
| CO₂ per year | – | – |
06Benefits
Heat that is already paid for
The compressors produce this heat anyway. The heat pump only adds the lift to a useful temperature.
High efficiency
A warm 55 °C source gives a much higher COP than an air-source unit making the same water.
Cooler, longer-lived compressors
Steady heat removal keeps oil temperature down in summer and reduces high-temperature trips.
Lower energy cost
Each kWh of electricity delivers about 2.9 kWh of heat at the required temperature, against well under one kWh of useful heat per kWh of fuel burnt.
No flame on site
No burner, flue or fuel tank for this duty, and no fuel deliveries to schedule.
Built-in redundancy
Several machines share the load. If one is serviced, the others and the storage carry most of the day, with the existing heater in reserve.
07Engineering pointers
Site data to collect
- Compressor ratings, load profile and running hours
- Oil cooler type and existing heat recovery
- Hot water users, volumes and temperatures
- Monthly diesel use for hot water
- Present fuel or electricity use and monthly bill
- Sanctioned electrical load and spare capacity
- Space for the heat pumps and storage, with service access
Design notes
- Compressor warranty. Agree the heat-recovery tie-in and oil temperature limits with the compressor service provider before installation.
- Match source and demand. Heat is only available while compressors are loaded. Size storage so washers and canteen still have hot water during low-air periods.
- Electrical. About 18 kW of heat pump input at rated conditions, plus pumps and fans. Check spare sanctioned load before ordering.
- Source stream. The source must give up roughly two-thirds of the heat delivered. Confirm its flow and temperature over a full production day, and filter it before the evaporator.
- Water quality. Scale forms quickly above 60 °C. Use softened make-up and keep the heat pump loop closed, with process fluids on the far side of an exchanger or coil.
Service and warranty
Sunniva has supplied 5,000+ heat pumps since 2012, with nine service technicians across India, including remote sites such as Leh. All components carry a one-year warranty.