Environmental Control Systems
Deep dive into vertical farm environmental management.
Overview
Environmental control is the heart of vertical farming. Unlike outdoor agriculture, every parameter is controllable and optimizable.
┌─────────────────────────────────────────────────────────────────┐
│ ENVIRONMENTAL CONTROL SYSTEM │
├─────────────────────────────────────────────────────────────────┤
│ │
│ ┌────────────┐ ┌────────────┐ ┌────────────┐ │
│ │TEMPERATURE │ │ HUMIDITY │ │ CO2 │ │
│ │ Control │ │ Control │ │ Control │ │
│ │ │ │ │ │ │ │
│ │ HVAC │ │ Humidifier │ │ Injection │ │
│ │ Heat Pump │ │ Dehumid. │ │ Generator │ │
│ └─────┬──────┘ └─────┬──────┘ └─────┬──────┘ │
│ │ │ │ │
│ └─────────────────┼─────────────────┘ │
│ │ │
│ ┌─────▼─────┐ │
│ │ CENTRAL │ │
│ │ CONTROLLER│ │
│ └─────┬─────┘ │
│ │ │
│ ┌─────────────────┼─────────────────┐ │
│ │ │ │ │
│ ┌─────▼──────┐ ┌─────▼─────┐ ┌─────▼──────┐ │
│ │ LIGHTING │ │ WATER │ │ NUTRIENTS │ │
│ │ Control │ │ Control │ │ Control │ │
│ │ │ │ │ │ │ │
│ │ LEDs │ │ Irrigation │ │ Dosing │ │
│ │ Spectrum │ │ pH adjust │ │ EC monitor │ │
│ └────────────┘ └────────────┘ └────────────┘ │
│ │
└─────────────────────────────────────────────────────────────────┘
Temperature Control
Target Ranges by Crop Type
| Crop Category |
Day Temp (°C) |
Night Temp (°C) |
Differential |
| Leafy Greens |
18-22 |
15-18 |
3-5°C |
| Herbs |
20-25 |
18-22 |
2-4°C |
| Fruiting |
22-28 |
18-22 |
4-6°C |
| Microgreens |
18-21 |
16-19 |
2-3°C |
Control Strategies
interface TemperatureControl {
mode: 'manual' | 'scheduled' | 'adaptive' | 'ai_optimized';
// Setpoints
daySetpoint: number;
nightSetpoint: number;
// Deadband (prevent oscillation)
deadband: number; // ±1°C typical
// Control outputs
coolingStage: 0 | 1 | 2 | 3; // Multi-stage cooling
heatingStage: 0 | 1 | 2 | 3; // Multi-stage heating
}
HVAC Systems
| System Type |
Pros |
Cons |
Best For |
| Split AC |
Low cost |
Limited capacity |
Small rooms |
| Mini-split |
Zoned control |
Moderate cost |
Medium facilities |
| Heat Pump |
Efficient, heat recovery |
Higher upfront |
Production facilities |
| Chilled Water |
Scalable, precise |
Complex, expensive |
Large operations |
Humidity Control
Vapor Pressure Deficit (VPD)
VPD is the key metric for plant transpiration:
VPD = Saturation Pressure - Actual Vapor Pressure
Optimal VPD by Stage:
- Seedling: 0.4-0.8 kPa (high humidity)
- Vegetative: 0.8-1.2 kPa (moderate)
- Flowering: 1.0-1.5 kPa (lower humidity)
VPD Calculation
function calculateVPD(tempC: number, humidityPercent: number): number {
// Saturation vapor pressure (Tetens equation)
const svp = 0.6108 * Math.exp((17.27 * tempC) / (tempC + 237.3));
// Actual vapor pressure
const avp = svp * (humidityPercent / 100);
// VPD in kPa
return svp - avp;
}
Humidification Methods
| Method |
Droplet Size |
Coverage |
Energy |
Best For |
| Misting |
20-50 µm |
Wide |
Low |
Propagation |
| Ultrasonic |
1-5 µm |
Targeted |
Low |
Small zones |
| Fog |
5-20 µm |
Wide |
Medium |
Large areas |
| Evaporative |
N/A |
Wide |
Low |
Arid climates |
Dehumidification
Sources of Humidity:
├── Plant transpiration: 95%+ of water uptake
├── Irrigation: Evaporation from growing media
├── Human activity: Breathing, sweating
└── Fresh air: Outdoor humidity
Removal Methods:
├── HVAC: Condenses on evaporator coil
├── Dedicated dehumidifier: Efficient for high loads
├── Desiccant: Continuous, no condensate
└── Ventilation: If outdoor humidity lower
CO2 Enrichment
Why Enrich?
Ambient CO2: ~420 ppm
Optimal Growth: 800-1200 ppm
Maximum Benefit: 1500 ppm
Photosynthesis increases ~30-50% with enrichment
CO2 Sources
| Source |
Cost |
Control |
Safety |
Best For |
| Tank (compressed) |
Medium |
Excellent |
Safe |
Small/medium |
| Generator (propane) |
Low |
Good |
Heat/humidity |
Sealed rooms |
| Fermentation |
Very low |
Poor |
Safe |
Hobby |
| Air capture |
High |
Excellent |
Safe |
Large scale |
Control Strategy
interface CO2Control {
targetPpm: number;
hysteresis: number; // ±50 ppm typical
// Only enrich when lights on
enrichDuringLightsOnly: boolean;
// Integration with ventilation
pauseDuringVentilation: boolean;
// Safety limits
maxPpm: 2000; // Worker safety
alarmPpm: 1800;
}
Lighting Systems
Light Spectrum
Wavelength Ranges:
├── UV-A (315-400nm): Compact growth, secondary metabolites
├── Blue (400-500nm): Vegetative growth, compact structure
├── Green (500-565nm): Canopy penetration
├── Red (620-700nm): Photosynthesis, flowering
└── Far-Red (700-800nm): Shade avoidance, flowering
Optimal Ratios (general):
- Vegetative: Blue 30%, Red 60%, Other 10%
- Flowering: Blue 20%, Red 70%, Other 10%
LED Fixture Types
| Type |
Spectrum |
Efficiency |
Cost |
Best For |
| Full Spectrum |
White + Red/Blue |
Good |
Low |
General |
| Red/Blue |
Optimized peaks |
High |
Medium |
Leafy greens |
| Tunable |
Adjustable |
Good |
High |
Research, multi-crop |
| Sunlight Replica |
Full PAR + UV |
Excellent |
Very High |
Premium produce |
Light Metrics
PPFD (µmol/m²/s): Instantaneous light intensity
DLI (mol/m²/day): Daily light integral = PPFD × hours × 3600 / 1,000,000
Targets by Crop:
├── Microgreens: DLI 8-12
├── Lettuce: DLI 12-17
├── Basil: DLI 15-20
├── Tomatoes: DLI 22-30
└── Cannabis: DLI 40-65
Nutrient Delivery
Solution Management
interface NutrientSolution {
// Primary monitoring
ec: number; // Electrical Conductivity (mS/cm)
ph: number; // Target 5.5-6.5
// Temperature
tempC: number; // Target 18-22°C
// Dissolved oxygen
doPpm: number; // Target >6 ppm
// Macro nutrients (ppm)
nitrogen: number; // 150-250
phosphorus: number; // 30-60
potassium: number; // 150-300
calcium: number; // 150-250
magnesium: number; // 40-80
sulfur: number; // 50-100
}
Dosing Systems
┌─────────────────────────────────────────────────────────────┐
│ DOSING SYSTEM │
├─────────────────────────────────────────────────────────────┤
│ │
│ Stock Solutions │
│ ┌─────┐ ┌─────┐ ┌─────┐ ┌─────┐ ┌─────┐ ┌─────┐ │
│ │ A │ │ B │ │CalMag│ │pH Up│ │pH Dn│ │Sili │ │
│ └──┬──┘ └──┬──┘ └──┬──┘ └──┬──┘ └──┬──┘ └──┬──┘ │
│ │ │ │ │ │ │ │
│ ▼ ▼ ▼ ▼ ▼ ▼ │
│ ┌────────────────────────────────────────────────────┐ │
│ │ DOSING PUMPS │ │
│ │ Peristaltic pumps: Precise, low maintenance │ │
│ └────────────────────────────────────────────────────┘ │
│ │ │
│ ▼ │
│ ┌────────────────────────────────────────────────────┐ │
│ │ MIXING TANK │ │
│ │ - EC sensor │ │
│ │ - pH sensor │ │
│ │ - Temperature sensor │ │
│ │ - Level sensor │ │
│ └────────────────────────────────────────────────────┘ │
│ │ │
│ ▼ │
│ ┌────────────────────────────────────────────────────┐ │
│ │ GROWING ZONES │ │
│ └────────────────────────────────────────────────────┘ │
│ │
└─────────────────────────────────────────────────────────────┘
Air Circulation
Airflow Requirements
Purposes:
├── Temperature uniformity
├── Humidity distribution
├── CO2 distribution
├── Plant strengthening (thigmomorphogenesis)
└── Disease prevention
Velocity Targets:
├── At canopy: 0.3-0.5 m/s
├── Avoid dead spots
├── Avoid excessive wind stress
Fan Types
| Fan Type |
Use |
Placement |
| Circulation |
Air mixing |
Throughout canopy |
| Oscillating |
Variable airflow |
Above canopy |
| Exhaust |
Heat/humidity removal |
High in room |
| Intake |
Fresh air, CO2 dilution |
Low in room |
Sensor Networks
Sensor Placement
Zone Layout with Sensors:
┌─────────────────────────────────┐
│ [T/H] [T/H] │ [T/H] = Temp/Humidity
│ ●───────────────● │
│ │ [CO2] │ │ [CO2] = CO2 sensor
│ │ ● │ │
│ ┌───┴───────────────┴───┐ │ [PAR] = Light sensor
│ │ [PAR] [PAR] │ │
│ │ ● ● │ Zone │ [EC] = EC sensor
│ │ ▓▓▓▓▓▓▓▓▓▓▓▓▓▓ │ │
│ │ ▓▓ Plants ▓▓▓▓ │ │ [pH] = pH sensor
│ │ ▓▓▓▓▓▓▓▓▓▓▓▓▓▓ │ │
│ │ [EC] [pH] │ │
│ │ ● ● (reservoir)│ │
│ └───────────────────────┘ │
│ │
└─────────────────────────────────┘
Recommended Density:
- T/H: 1 per 20-50 m²
- CO2: 1 per zone (at plant height)
- PAR: 2-4 per zone (canopy level)
- EC/pH: At each reservoir
Calibration Schedule
| Sensor |
Frequency |
Method |
| Temperature |
Monthly |
Reference thermometer |
| Humidity |
Monthly |
Saturated salt test |
| CO2 |
Quarterly |
Cal gas (fresh air ref) |
| PAR |
Annually |
Reference meter |
| EC |
Weekly |
Cal solution |
| pH |
Weekly |
pH 4.0, 7.0 buffers |
Alert System
Alert Thresholds
interface AlertThresholds {
temperature: {
warning: { low: targetMin - 2, high: targetMax + 2 };
critical: { low: targetMin - 5, high: targetMax + 5 };
};
humidity: {
warning: { low: 50, high: 80 };
critical: { low: 40, high: 90 };
};
co2: {
warning: { low: 600, high: 1600 };
critical: { high: 2000 }; // Safety
};
ec: {
warning: { low: targetEc - 0.3, high: targetEc + 0.3 };
critical: { low: targetEc - 0.5, high: targetEc + 0.5 };
};
ph: {
warning: { low: 5.0, high: 7.0 };
critical: { low: 4.5, high: 7.5 };
};
}
Alert Escalation
Level 1: In-app notification
↓ (no response 5 min)
Level 2: SMS/Push notification
↓ (no response 15 min)
Level 3: Phone call
↓ (no response 30 min)
Level 4: Emergency contact
Best Practices
Daily Operations
- Check sensors - Verify readings match reality
- Inspect plants - Catch issues before sensors
- Review logs - Look for trends
- Maintain equipment - Filters, pumps, fans
Preventive Maintenance
| Equipment |
Weekly |
Monthly |
Quarterly |
| Sensors |
Visual check |
Calibrate |
Replace if needed |
| Filters |
Replace/clean |
Deep clean |
- |
| Pumps |
Check flow |
Lubricate |
Service |
| HVAC |
Check operation |
Filter |
Coil cleaning |
| LEDs |
Wipe |
Check spectrum |
Power audit |
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