Paddy and seed dried gently with heat pumps
How a rice mill and seed unit drying 13 tonnes of paddy and seed a day can use a closed-loop heat pump dryer, and what it saves against a diesel-fired batch dryer.
▶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
- Cracked grain. Drying paddy too fast with hot air causes fissures, and the grain breaks in milling. Every 1% loss of head rice costs money.
- Seed germination. Seed must stay below about 43 °C or germination falls and the lot is rejected.
- Rain at harvest. Wet harvest weather loads the dryer with damp grain just when outside air cannot dry it.
- 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 unit dries freshly harvested paddy for its own rice mill and hybrid maize and vegetable seed for a seed company, about 13 tonnes a day through the harvest seasons. Drying runs round the clock in recirculating batch bins.
| Product | Drying | Basis | Water removed, kg/day | Conventional heat, kWh/day |
|---|---|---|---|---|
| Paddy | Air 40–45 °C | 10,000 kg/day, 22% → 14% | 930 | 1,674 |
| Hybrid maize and vegetable seed | Air 38–40 °C | 3,000 kg/day, 18% → 9% | 297 | 534 |
| Total | 1,227 | 2,208 | ||
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
- 5 × SE-AA-DR-11 (52 kW total) heat pump drying modules, removing about 1,227 kg of water a day in roughly 20 running hours.
- The diesel-burner batch grain dryer stays connected behind a normally closed valve as standby.
- A closed-loop heat pump dryer supplies dry, warm air at 40–45 °C to the existing recirculating bins.
- Low air humidity lets the grain dry at low temperature without stretching the drying time.
- Tempering periods between passes stay as they are, so moisture evens out inside each kernel.
Selected equipment
| Model | 5 × SE-AA-DR-11 |
|---|---|
| Heating capacity | 10.5 kW each, 52 kW total |
| Dehumidifying | about 61 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 holds air at 40–45 °C for paddy and 38–40 °C for seed. A return-air humidity sensor sets the dehumidifying duty. Grain moisture is checked with a meter at each pass, and the batch ends when the target moisture is reached.
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 grain | – | – |
| CO₂ per year | – | – |
06Benefits
More head rice
Gentle, low-temperature drying reduces fissuring, so more whole grains come out of the mill.
Seed stays viable
Air never exceeds the safe temperature for seed, protecting germination.
Independent of the weather
Dry air is produced even in rain, so wet harvests can still be dried on time.
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
- Tonnes per day of each crop in season
- Harvest moisture and target moisture
- Bin capacity and tempering practice
- Season length for each crop
- 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
- Dust. Grain dust clogs coils and is a fire risk. Fit filters on the return air and clean them each shift.
- Seasonal duty. Drying runs only in harvest seasons. Plan maintenance before each season and protect the units during idle months.
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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Paddy and seed dried gently with heat pumps
How a rice mill and seed unit drying 13 tonnes of paddy and seed a day can use a closed-loop heat pump dryer, and what it saves against a diesel-fired batch dryer.
▶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
- Cracked grain. Drying paddy too fast with hot air causes fissures, and the grain breaks in milling. Every 1% loss of head rice costs money.
- Seed germination. Seed must stay below about 43 °C or germination falls and the lot is rejected.
- Rain at harvest. Wet harvest weather loads the dryer with damp grain just when outside air cannot dry it.
- 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 unit dries freshly harvested paddy for its own rice mill and hybrid maize and vegetable seed for a seed company, about 13 tonnes a day through the harvest seasons. Drying runs round the clock in recirculating batch bins.
| Product | Drying | Basis | Water removed, kg/day | Conventional heat, kWh/day |
|---|---|---|---|---|
| Paddy | Air 40–45 °C | 10,000 kg/day, 22% → 14% | 930 | 1,674 |
| Hybrid maize and vegetable seed | Air 38–40 °C | 3,000 kg/day, 18% → 9% | 297 | 534 |
| Total | 1,227 | 2,208 | ||
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
- 5 × SE-AA-DR-11 (52 kW total) heat pump drying modules, removing about 1,227 kg of water a day in roughly 20 running hours.
- The diesel-burner batch grain dryer stays connected behind a normally closed valve as standby.
- A closed-loop heat pump dryer supplies dry, warm air at 40–45 °C to the existing recirculating bins.
- Low air humidity lets the grain dry at low temperature without stretching the drying time.
- Tempering periods between passes stay as they are, so moisture evens out inside each kernel.
Selected equipment
| Model | 5 × SE-AA-DR-11 |
|---|---|
| Heating capacity | 10.5 kW each, 52 kW total |
| Dehumidifying | about 61 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 holds air at 40–45 °C for paddy and 38–40 °C for seed. A return-air humidity sensor sets the dehumidifying duty. Grain moisture is checked with a meter at each pass, and the batch ends when the target moisture is reached.
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 grain | – | – |
| CO₂ per year | – | – |
06Benefits
More head rice
Gentle, low-temperature drying reduces fissuring, so more whole grains come out of the mill.
Seed stays viable
Air never exceeds the safe temperature for seed, protecting germination.
Independent of the weather
Dry air is produced even in rain, so wet harvests can still be dried on time.
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
- Tonnes per day of each crop in season
- Harvest moisture and target moisture
- Bin capacity and tempering practice
- Season length for each crop
- 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
- Dust. Grain dust clogs coils and is a fire risk. Fit filters on the return air and clean them each shift.
- Seasonal duty. Drying runs only in harvest seasons. Plan maintenance before each season and protect the units during idle months.
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.