Flue-cured tobacco barns run on heat pumps
How a cluster of three Virginia tobacco curing barns can be cured with a closed-loop heat pump dryer, and what it saves against wood or briquette-fired flues.
▶Video: Heat pump dryers for food and agri products
V08 · 2–2.5 minClosed-loop drying of spices, fruit, fish, grain and more
Video coming soon01Problem statement
- Curing schedule is strict. Yellowing at 35–38 °C, leaf drying at 45–55 °C and stem drying up to about 70 °C must each be held closely. Wood fires make this hard.
- Firewood use. Traditional barns burn several kilograms of wood per kilogram of cured leaf, with pressure on local forests.
- Leaf quality loss. Temperature swings give green or scalded leaf and lower grades at auction.
- Losses between fuel and process. Burning briquettes 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 site has three flue-cured Virginia barns of about 3,500 kg green leaf each, curing in rotation on a 6-day cycle through the January to April season. This is about 1,750 kg of green leaf a day on average.
| Product | Drying | Basis | Water removed, kg/day | Conventional heat, kWh/day |
|---|---|---|---|---|
| Yellowing and lamina drying | Air 35–55 °C | 1,750 kg/day green leaf, 85% → 55% | 1,167 | 2,100 |
| Midrib (stem) drying | Air 60–70 °C | 583 kg/day partly dried leaf, 55% → 12% | 285 | 513 |
| Total | 1,452 | 2,613 | ||
Conventional hot-air dryers use about 1.8 kWh of heat per kg of water removed. That figure is the baseline the savings are measured against.
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
- 3 × SE-AA-DR-21 (63 kW total) heat pump drying modules, removing about 1,452 kg of water a day in roughly 20 running hours.
- The wood or briquette-fired barn flue furnace stays connected behind a normally closed valve as standby.
- A closed-loop heat pump dryer heats and dehumidifies barn air, following the yellowing, leaf drying and stem drying stages.
- The barn structure and leaf sticks stay as they are. Flue pipes are replaced by a heat pump air handler.
- Moisture is removed on the cold coil, so vent losses are much lower than in a flue-cured barn.
Selected equipment
| Model | 3 × SE-AA-DR-21 |
|---|---|
| Heating capacity | 21 kW each, 63 kW total |
| Dehumidifying | about 74 L/h total (pro rata to the published 12–120 L/h range) |
| Drying air | rated 70 °C, 75 °C maximum |
| Refrigerant | R134a |
| Ambient | −5 to 43 °C |
| Water removed per kWh | about 2.4 kg |
Ratings from the Sunniva TDS 2026 data sheets.
Control philosophy
TIC-201 follows the curing schedule, holding dry-bulb temperature at each stage. A wet-bulb or humidity sensor sets dehumidifying duty, keeping humidity high during yellowing and low during drying. Each barn runs its own programme from a simple controller.
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 | – | – |
| Cost per tonne of green leaf | – | – |
| CO₂ per year | – | – |
06Benefits
Closer curing control
Dry-bulb and wet-bulb follow the schedule closely, giving more even colour and better grades.
No firewood
Wood use and the labour of stoking furnaces through the night are removed.
No flue leaks
Without flue pipes there is no smoke or fire risk inside the barn.
Heat recovered from the moisture
The evaporator condenses water out of the air and the condenser puts that latent heat back into the drying air, so about 2.4 kg of water leaves per kWh of electricity.
Closed loop, clean product
Air recirculates inside the chamber. No dust, smoke or outside humidity reaches the product, whatever the weather.
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
- Number and size of barns
- Green leaf per curing and curing cycle
- Curing schedule used
- Present wood use per barn
- 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
- Barn insulation. Old brick barns leak air and heat. Seal and insulate walls and roof before fitting a heat pump dryer.
- Stem drying temperature. Stem drying needs air close to 70 °C. Keep the final stage at the dryer's upper limit and allow a little more time.
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.
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Flue-cured tobacco barns run on heat pumps
How a cluster of three Virginia tobacco curing barns can be cured with a closed-loop heat pump dryer, and what it saves against wood or briquette-fired flues.
▶Video: Heat pump dryers for food and agri products
V08 · 2–2.5 minClosed-loop drying of spices, fruit, fish, grain and more
Video coming soon01Problem statement
- Curing schedule is strict. Yellowing at 35–38 °C, leaf drying at 45–55 °C and stem drying up to about 70 °C must each be held closely. Wood fires make this hard.
- Firewood use. Traditional barns burn several kilograms of wood per kilogram of cured leaf, with pressure on local forests.
- Leaf quality loss. Temperature swings give green or scalded leaf and lower grades at auction.
- Losses between fuel and process. Burning briquettes 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 site has three flue-cured Virginia barns of about 3,500 kg green leaf each, curing in rotation on a 6-day cycle through the January to April season. This is about 1,750 kg of green leaf a day on average.
| Product | Drying | Basis | Water removed, kg/day | Conventional heat, kWh/day |
|---|---|---|---|---|
| Yellowing and lamina drying | Air 35–55 °C | 1,750 kg/day green leaf, 85% → 55% | 1,167 | 2,100 |
| Midrib (stem) drying | Air 60–70 °C | 583 kg/day partly dried leaf, 55% → 12% | 285 | 513 |
| Total | 1,452 | 2,613 | ||
Conventional hot-air dryers use about 1.8 kWh of heat per kg of water removed. That figure is the baseline the savings are measured against.
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
- 3 × SE-AA-DR-21 (63 kW total) heat pump drying modules, removing about 1,452 kg of water a day in roughly 20 running hours.
- The wood or briquette-fired barn flue furnace stays connected behind a normally closed valve as standby.
- A closed-loop heat pump dryer heats and dehumidifies barn air, following the yellowing, leaf drying and stem drying stages.
- The barn structure and leaf sticks stay as they are. Flue pipes are replaced by a heat pump air handler.
- Moisture is removed on the cold coil, so vent losses are much lower than in a flue-cured barn.
Selected equipment
| Model | 3 × SE-AA-DR-21 |
|---|---|
| Heating capacity | 21 kW each, 63 kW total |
| Dehumidifying | about 74 L/h total (pro rata to the published 12–120 L/h range) |
| Drying air | rated 70 °C, 75 °C maximum |
| Refrigerant | R134a |
| Ambient | −5 to 43 °C |
| Water removed per kWh | about 2.4 kg |
Ratings from the Sunniva TDS 2026 data sheets.
Control philosophy
TIC-201 follows the curing schedule, holding dry-bulb temperature at each stage. A wet-bulb or humidity sensor sets dehumidifying duty, keeping humidity high during yellowing and low during drying. Each barn runs its own programme from a simple controller.
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 | – | – |
| Cost per tonne of green leaf | – | – |
| CO₂ per year | – | – |
06Benefits
Closer curing control
Dry-bulb and wet-bulb follow the schedule closely, giving more even colour and better grades.
No firewood
Wood use and the labour of stoking furnaces through the night are removed.
No flue leaks
Without flue pipes there is no smoke or fire risk inside the barn.
Heat recovered from the moisture
The evaporator condenses water out of the air and the condenser puts that latent heat back into the drying air, so about 2.4 kg of water leaves per kWh of electricity.
Closed loop, clean product
Air recirculates inside the chamber. No dust, smoke or outside humidity reaches the product, whatever the weather.
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
- Number and size of barns
- Green leaf per curing and curing cycle
- Curing schedule used
- Present wood use per barn
- 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
- Barn insulation. Old brick barns leak air and heat. Seal and insulate walls and roof before fitting a heat pump dryer.
- Stem drying temperature. Stem drying needs air close to 70 °C. Keep the final stage at the dryer's upper limit and allow a little more time.
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.