Mushroom compost and growing rooms heated by heat pumps
How a 5 tonne-per-day button mushroom farm can heat its Phase II tunnels and growing rooms with heat pumps, and what it saves against a diesel-fired steam boiler.
▶Video: Hot air from heat pump hot water
V05 · 2–2.5 minAir coils for spray dryers, stenters, kilns, paint booths and ovens
Video coming soon01Problem statement
- Phase II needs precise heat. Compost must be pasteurised at 57–60 °C and then conditioned at 45–48 °C. Overshoot kills useful microbes and undershoot leaves pests and moulds.
- Rooms need reheat to dehumidify. Growing rooms are cooled to remove moisture and then reheated, so heat is needed even in summer.
- Live steam in tunnels. Injecting boiler steam into tunnels is hard to control and wastes condensate and treated water.
- 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 farm produces about 5 tonnes of button mushrooms a day from 20 insulated growing rooms and two Phase II pasteurisation tunnels. It runs year round, with rooms held at 16–18 °C and 85–90% relative humidity.
| Heat user | Process temp. | Basis | Heat, kWh/day |
|---|---|---|---|
| Phase II tunnel air heating | Air 57–60 °C | 3,000 m³/h × 1.2 kg/m³ × 1.005 kJ/kgK × 35 K = 35 kW × 20 h | 703 |
| Growing room heating and reheat | Rooms 16–18 °C | 20 rooms × 4 kW average × 20 h | 1,600 |
| Casing, shelf and floor washing | 60 °C | 4,000 L/day, 25 → 60 °C | 163 |
| Storage and pipework standing losses | – | about 5% | 123 |
| Total useful heat | 2,589 | ||
Averaged over 20 running hours, the heat pumps need about 129 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
- 1 × SE-HT-150V (142 kW) (SE-HT high-temperature heat pump) delivering 70 °C, covering the day's 2,589 kWh in about 18.2 running hours.
- A 4,500 L insulated storage tank decouples the heat pumps from the process peaks.
- The diesel-fired steam boiler stays connected behind a normally closed valve as standby.
- Hot-water coils in the tunnel AHUs replace steam injection for raising and holding Phase II temperature.
- Each growing room AHU gets a hot-water reheat coil after the cooling coil for humidity control.
- The 65–70 °C storage tank also serves cleaning and casing preparation.
- Humidity in tunnels is added with a small humidifier, so the heating and wetting duties are controlled separately.
Selected equipment
| Model | SE-HT-150V × 1 |
|---|---|
| Heating capacity | 142 kW each, 142 kW total |
| COP | 3.4 at A20 °C / W70 °C, interpolated from the data sheet's 60, 70 and 80 °C points |
| Power input | about 41.8 kW total at rated conditions |
| Rating | rated 75 °C, 80 °C maximum, R134a |
| Supply temperature | 70 °C |
| Storage | 4,500 L insulated tank |
Ratings from the Sunniva TDS 2026 data sheets.
Control philosophy
TT-101 at the top of the tank starts the heat pumps below 64 °C and stops them at 70 °C. TIC-201 follows the Phase II recipe for compost temperature using the tunnel coil valve. TIC-202 in each room controls reheat to hold temperature while the cooling coil removes moisture. The boiler stays as standby for tunnel peaks.
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 mushrooms | – | – |
| CO₂ per year | – | – |
06Benefits
Tighter Phase II control
Hot-water coils let the tunnel follow its recipe within ±1 K, which helps compost quality.
Reheat at low cost
Room reheat runs all year and moves from boiler or electric heat to the heat pumps.
Less water treatment
Live steam injection stops, so treated boiler water no longer disappears into the compost.
Lower energy cost
Each kWh of electricity delivers about 3.4 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
- Daily mushroom output and number of growing rooms
- Phase II tunnel size, batch weight and recipe
- Room ventilation and humidity set points
- Current boiler fuel use
- Hot water use for washing
- Present fuel or electricity use and monthly bill
- Sanctioned electrical load and spare capacity
- Space for the heat pumps and storage, with service access
- Winter minimum ambient at site
Design notes
- Ammonia from compost. Tunnel exhaust is rich in ammonia. Keep heat pump outdoor units well away from tunnel exhaust and use copper-free coils in the tunnel AHUs where possible.
- Hygiene. Coils in growing rooms must be easy to clean and disinfect between crops.
- Condensation. Insulate hot-water pipework through cold, humid growing rooms and slope coil drip trays to drain.
- Electrical. About 42 kW of heat pump input at rated conditions, plus pumps and fans. Check spare sanctioned load before ordering.
- Ambient correction. Ratings are at 20 °C air. Ask Sunniva for the correction at your site's winter design temperature.
- 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
Mushroom compost and growing rooms heated by heat pumps
How a 5 tonne-per-day button mushroom farm can heat its Phase II tunnels and growing rooms with heat pumps, and what it saves against a diesel-fired steam boiler.
▶Video: Hot air from heat pump hot water
V05 · 2–2.5 minAir coils for spray dryers, stenters, kilns, paint booths and ovens
Video coming soon01Problem statement
- Phase II needs precise heat. Compost must be pasteurised at 57–60 °C and then conditioned at 45–48 °C. Overshoot kills useful microbes and undershoot leaves pests and moulds.
- Rooms need reheat to dehumidify. Growing rooms are cooled to remove moisture and then reheated, so heat is needed even in summer.
- Live steam in tunnels. Injecting boiler steam into tunnels is hard to control and wastes condensate and treated water.
- 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 farm produces about 5 tonnes of button mushrooms a day from 20 insulated growing rooms and two Phase II pasteurisation tunnels. It runs year round, with rooms held at 16–18 °C and 85–90% relative humidity.
| Heat user | Process temp. | Basis | Heat, kWh/day |
|---|---|---|---|
| Phase II tunnel air heating | Air 57–60 °C | 3,000 m³/h × 1.2 kg/m³ × 1.005 kJ/kgK × 35 K = 35 kW × 20 h | 703 |
| Growing room heating and reheat | Rooms 16–18 °C | 20 rooms × 4 kW average × 20 h | 1,600 |
| Casing, shelf and floor washing | 60 °C | 4,000 L/day, 25 → 60 °C | 163 |
| Storage and pipework standing losses | – | about 5% | 123 |
| Total useful heat | 2,589 | ||
Averaged over 20 running hours, the heat pumps need about 129 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
- 1 × SE-HT-150V (142 kW) (SE-HT high-temperature heat pump) delivering 70 °C, covering the day's 2,589 kWh in about 18.2 running hours.
- A 4,500 L insulated storage tank decouples the heat pumps from the process peaks.
- The diesel-fired steam boiler stays connected behind a normally closed valve as standby.
- Hot-water coils in the tunnel AHUs replace steam injection for raising and holding Phase II temperature.
- Each growing room AHU gets a hot-water reheat coil after the cooling coil for humidity control.
- The 65–70 °C storage tank also serves cleaning and casing preparation.
- Humidity in tunnels is added with a small humidifier, so the heating and wetting duties are controlled separately.
Selected equipment
| Model | SE-HT-150V × 1 |
|---|---|
| Heating capacity | 142 kW each, 142 kW total |
| COP | 3.4 at A20 °C / W70 °C, interpolated from the data sheet's 60, 70 and 80 °C points |
| Power input | about 41.8 kW total at rated conditions |
| Rating | rated 75 °C, 80 °C maximum, R134a |
| Supply temperature | 70 °C |
| Storage | 4,500 L insulated tank |
Ratings from the Sunniva TDS 2026 data sheets.
Control philosophy
TT-101 at the top of the tank starts the heat pumps below 64 °C and stops them at 70 °C. TIC-201 follows the Phase II recipe for compost temperature using the tunnel coil valve. TIC-202 in each room controls reheat to hold temperature while the cooling coil removes moisture. The boiler stays as standby for tunnel peaks.
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 mushrooms | – | – |
| CO₂ per year | – | – |
06Benefits
Tighter Phase II control
Hot-water coils let the tunnel follow its recipe within ±1 K, which helps compost quality.
Reheat at low cost
Room reheat runs all year and moves from boiler or electric heat to the heat pumps.
Less water treatment
Live steam injection stops, so treated boiler water no longer disappears into the compost.
Lower energy cost
Each kWh of electricity delivers about 3.4 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
- Daily mushroom output and number of growing rooms
- Phase II tunnel size, batch weight and recipe
- Room ventilation and humidity set points
- Current boiler fuel use
- Hot water use for washing
- Present fuel or electricity use and monthly bill
- Sanctioned electrical load and spare capacity
- Space for the heat pumps and storage, with service access
- Winter minimum ambient at site
Design notes
- Ammonia from compost. Tunnel exhaust is rich in ammonia. Keep heat pump outdoor units well away from tunnel exhaust and use copper-free coils in the tunnel AHUs where possible.
- Hygiene. Coils in growing rooms must be easy to clean and disinfect between crops.
- Condensation. Insulate hot-water pipework through cold, humid growing rooms and slope coil drip trays to drain.
- Electrical. About 42 kW of heat pump input at rated conditions, plus pumps and fans. Check spare sanctioned load before ordering.
- Ambient correction. Ratings are at 20 °C air. Ask Sunniva for the correction at your site's winter design temperature.
- 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.