Cooling tower heat turned into hot water
How a pharmaceutical plant with 1,000 TR of water-cooled chillers can recover condenser heat to make 60–65 °C process hot water, and what it saves against a furnace-oil fired boiler.
▶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
- Heat thrown away at the cooling tower. Every kW of cooling sends about 1.2 kW of heat to the cooling tower fans, where it is lost to the air along with evaporated water.
- Steam used for low-grade jobs. Boiler feed preheating, AHU reheat and washing only need 50–65 °C water, yet they are fed from a steam boiler running at 7–10 bar.
- Cooling tower water losses. Evaporation, drift and blowdown from the towers use large volumes of treated make-up water every day.
- Losses between fuel and process. Burning furnace oil 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 makes oral solid dosage forms and runs three shifts. Its water-cooled chillers total 1,000 TR and reject heat through cooling towers at 32–37 °C, while the boiler house heats feed water, AHU reheat coils and washing water.
| Heat user | Process temp. | Basis | Heat, kWh/day |
|---|---|---|---|
| Boiler feed water preheating | 30 → 60 °C | 30,000 L/day make-up and condensate top-up, 30 → 60 °C | 1,045 |
| AHU reheat coils (humidity control) | Hot water 60–65 °C | 4 AHUs × 15 kW average reheat × 20 h | 1,200 |
| Equipment and area washing | 60 °C | 10,000 L/day, 30 → 60 °C | 348 |
| Storage and pipework standing losses | – | about 5% | 130 |
| Total useful heat | 2,723 | ||
Averaged over 20 running hours, the heat pumps need about 136 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
- A Customized water-source cascade machine of about 140 kW, two-stage water-source machine built to duty, lifting 32 °C to 70 °C.
- A 4,500 L insulated storage tank decouples the heat pumps from the process peaks.
- Heat source: chiller condenser water return at about 32 °C. Cooling the condenser water reduces cooling tower fan power and make-up water use.
- The furnace-oil fired steam boiler stays connected behind a normally closed valve as standby.
- A side stream of condenser water is taken from the return header before the cooling tower and passed through the heat pump evaporators. The cooled water rejoins the tower basin.
- The heat pumps lift this heat to 65–70 °C into a stratified storage tank that serves feed water preheating, AHU reheat and washing.
- The cooling tower stays in service as before and handles any heat the heat pumps do not take, so chiller operation is unchanged.
- AHU reheat moves from steam or electric coils to hot-water coils on the same AHUs.
Selected equipment
| Machine | Customized water-source cascade |
|---|---|
| Capacity | about 140 kW, built to duty |
| Concept | two-stage water-source machine built to duty, lifting 32 °C to 70 °C |
| COP used | 3.2 (estimate) |
| Supply temperature | 70 °C |
| Storage | 4,500 L insulated tank |
Capacity is sized from the heat demand above. COP is an estimate until Sunniva engineering confirms the design.
Control philosophy
TT-101 at the top of the tank starts the heat pumps below 62 °C and stops them at 68 °C. TT-102 at the bottom stages a second unit when demand rises. A flow switch on the condenser side stream stops the heat pumps if the chillers are off. TIC-202 holds the AHU off-coil temperature and the existing steam supply 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
Less cooling tower load
Heat taken by the heat pumps never reaches the tower, so fan power, evaporation and blowdown all fall.
Two uses of one compressor
The same heat pump that makes hot water also cools condenser water, which helps the chillers run at lower head pressure.
Steady reheat
Hot-water reheat coils give smoother room humidity control than modulated steam valves.
Lower energy cost
Each kWh of electricity delivers about 3.2 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.
Solar-ready
Running hours can be placed in daylight so rooftop solar supplies much of the electricity, which also cuts CO₂ further.
07Engineering pointers
Site data to collect
- Chiller capacity, number of units and hourly load profile
- Condenser water flow and supply/return temperatures
- Hot-water users, their temperatures and daily volumes
- Cooling tower make-up water consumption
- Boiler fuel use for the low-temperature duties
- 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
- Water quality. Condenser water carries scale, biofilm and treatment chemicals. Use a strainer and an intermediate PHE or cleanable evaporators, and check the treatment programme with the water treatment vendor.
- Do not starve the chillers. Size the side stream so the condenser water temperature at the chiller inlet never rises. The heat pumps should only ever cool the water further.
- Match the hours. Recovery is only available while the chillers run. Log chiller load by hour before sizing.
- 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.
- Performance figure. The COP on this page is an engineering estimate, not a data sheet value. Sunniva engineering will confirm it for the actual source and supply temperatures.
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
Cooling tower heat turned into hot water
How a pharmaceutical plant with 1,000 TR of water-cooled chillers can recover condenser heat to make 60–65 °C process hot water, and what it saves against a furnace-oil fired boiler.
▶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
- Heat thrown away at the cooling tower. Every kW of cooling sends about 1.2 kW of heat to the cooling tower fans, where it is lost to the air along with evaporated water.
- Steam used for low-grade jobs. Boiler feed preheating, AHU reheat and washing only need 50–65 °C water, yet they are fed from a steam boiler running at 7–10 bar.
- Cooling tower water losses. Evaporation, drift and blowdown from the towers use large volumes of treated make-up water every day.
- Losses between fuel and process. Burning furnace oil 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 makes oral solid dosage forms and runs three shifts. Its water-cooled chillers total 1,000 TR and reject heat through cooling towers at 32–37 °C, while the boiler house heats feed water, AHU reheat coils and washing water.
| Heat user | Process temp. | Basis | Heat, kWh/day |
|---|---|---|---|
| Boiler feed water preheating | 30 → 60 °C | 30,000 L/day make-up and condensate top-up, 30 → 60 °C | 1,045 |
| AHU reheat coils (humidity control) | Hot water 60–65 °C | 4 AHUs × 15 kW average reheat × 20 h | 1,200 |
| Equipment and area washing | 60 °C | 10,000 L/day, 30 → 60 °C | 348 |
| Storage and pipework standing losses | – | about 5% | 130 |
| Total useful heat | 2,723 | ||
Averaged over 20 running hours, the heat pumps need about 136 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
- A Customized water-source cascade machine of about 140 kW, two-stage water-source machine built to duty, lifting 32 °C to 70 °C.
- A 4,500 L insulated storage tank decouples the heat pumps from the process peaks.
- Heat source: chiller condenser water return at about 32 °C. Cooling the condenser water reduces cooling tower fan power and make-up water use.
- The furnace-oil fired steam boiler stays connected behind a normally closed valve as standby.
- A side stream of condenser water is taken from the return header before the cooling tower and passed through the heat pump evaporators. The cooled water rejoins the tower basin.
- The heat pumps lift this heat to 65–70 °C into a stratified storage tank that serves feed water preheating, AHU reheat and washing.
- The cooling tower stays in service as before and handles any heat the heat pumps do not take, so chiller operation is unchanged.
- AHU reheat moves from steam or electric coils to hot-water coils on the same AHUs.
Selected equipment
| Machine | Customized water-source cascade |
|---|---|
| Capacity | about 140 kW, built to duty |
| Concept | two-stage water-source machine built to duty, lifting 32 °C to 70 °C |
| COP used | 3.2 (estimate) |
| Supply temperature | 70 °C |
| Storage | 4,500 L insulated tank |
Capacity is sized from the heat demand above. COP is an estimate until Sunniva engineering confirms the design.
Control philosophy
TT-101 at the top of the tank starts the heat pumps below 62 °C and stops them at 68 °C. TT-102 at the bottom stages a second unit when demand rises. A flow switch on the condenser side stream stops the heat pumps if the chillers are off. TIC-202 holds the AHU off-coil temperature and the existing steam supply 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
Less cooling tower load
Heat taken by the heat pumps never reaches the tower, so fan power, evaporation and blowdown all fall.
Two uses of one compressor
The same heat pump that makes hot water also cools condenser water, which helps the chillers run at lower head pressure.
Steady reheat
Hot-water reheat coils give smoother room humidity control than modulated steam valves.
Lower energy cost
Each kWh of electricity delivers about 3.2 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.
Solar-ready
Running hours can be placed in daylight so rooftop solar supplies much of the electricity, which also cuts CO₂ further.
07Engineering pointers
Site data to collect
- Chiller capacity, number of units and hourly load profile
- Condenser water flow and supply/return temperatures
- Hot-water users, their temperatures and daily volumes
- Cooling tower make-up water consumption
- Boiler fuel use for the low-temperature duties
- 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
- Water quality. Condenser water carries scale, biofilm and treatment chemicals. Use a strainer and an intermediate PHE or cleanable evaporators, and check the treatment programme with the water treatment vendor.
- Do not starve the chillers. Size the side stream so the condenser water temperature at the chiller inlet never rises. The heat pumps should only ever cool the water further.
- Match the hours. Recovery is only available while the chillers run. Log chiller load by hour before sizing.
- 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.
- Performance figure. The COP on this page is an engineering estimate, not a data sheet value. Sunniva engineering will confirm it for the actual source and supply temperatures.
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.