Fan & Pad Structure: A Complete Guide to Evaporative Cooling in Protected Cultivation

Fan & Pad structure, also known as a fanpad system or evaporative cooling system, is an advanced climate-control setup used in greenhouses and polyhouses to regulate temperature and humidity. It plays a crucial role in maintaining optimal growing conditions, especially in hot and dry climates.

This guide explains everything you need to know about fanpad structures, how they work, their components, installation principles, management practices, and maintenance requirements in a simple and practical way.

What Is a Fan & Pad Structure?

A Fan & Pad structure is a cooling system installed in polyhouses or greenhouses to reduce internal temperature through evaporative cooling. It consists of:

• Cooling pads installed on one side of the structure
• Exhaust fans installed on the opposite side
• A water circulation system that keeps the pads wet

When hot air enters through the wet pads, it cools down before circulating inside the structure.

Why Temperature Control Is Critical

In protected cultivation, temperature directly influences:

• Photosynthesis rate
• Flowering and fruiting cycles
• Water uptake
• Nutrient absorption
• Pest and disease pressure

High temperatures can cause plant stress, leaf burn, reduced growth, and poor development. A fanpad system helps maintain a stable environment during hot conditions.

How the Fan & Pad System Works

The fan & pad system works on the principle of evaporative cooling.

Step-by-step process:

1. Water flows continuously over cooling pads.

2. Exhaust fans create negative pressure inside the structure.

3. Hot outside air is drawn through the wet cooling pads.

4. As air passes through the pads, water evaporates.

5. Evaporation absorbs heat, reducing air temperature.

6. Cool air circulates inside the structure.

This creates a controlled internal climate.

Main Components of a Fanpad Structure

A complete fan & pad system includes:

1. Cooling Pads

Usually made of cellulose material with a honeycomb structure.

2. Exhaust Fans

Industrial-grade fans installed on the opposite wall.

3. Water Tank

Stores water for pad circulation.

4. Pump

Circulates water to keep pads continuously wet.

5. Distribution Pipes

Deliver water evenly across pads.

6. Gutters

Collect excess water and return it to the tank.

Types of Cooling Pads

Cooling pads vary in:

• Thickness (100 mm, 150 mm, 200 mm)
• Material composition
• Airflow resistance
• Durability

Common types:

• Cellulose pads (most widely used)
• Aspen pads
• Synthetic fiber pads

Cellulose pads are preferred due to high cooling efficiency and durability.

Types of Exhaust Fans

Exhaust fans used in fanpad systems are:

• Direct drive fans
• Belt-driven fans
• Cone fans (high efficiency)

Fan selection depends on:

• Structure size
• Air volume requirement
• Desired air exchange rate

Structural Design Requirements

Proper structure design ensures efficient cooling.

Key design elements:

• Pad wall on one side
• Fan wall on opposite side
• Airtight sidewalls
• Proper sealing to prevent air leakage
• Uniform length-to-width ratio

Typical recommendation:

• Maximum airflow path length: 30–40 meters for effective cooling.

Installation Guidelines

Installation must follow proper alignment principles:

• Pads installed vertically
• Fans positioned evenly across wall
• Water distribution uniform across pad surface
• Sufficient water storage capacity

Improper installation reduces cooling efficiency.

Airflow Management Principles

Airflow is critical for cooling success.

Key rules:

• Maintain uniform airflow across the crop canopy.
• Avoid dead zones.
• Ensure negative pressure inside the structure.
• Proper fan spacing prevents uneven cooling.

The air exchange rate should match crop requirements.

Water Circulation System

Water system includes:

• Pump
• Distribution header
• PVC pipelines
• Gutter collection
• Storage tank

Continuous water flow keeps pads saturated. Intermittent water supply reduces the cooling effect.

Cooling Efficiency Factors

Cooling efficiency depends on:

• Outside temperature
• Outside humidity
• Pad thickness
• Air velocity
• Water saturation level

Lower outside humidity improves evaporative cooling performance.

Ideal Climate Conditions for Fanpad Systems

Fanpad systems work best in:

• Hot and dry climates
• Regions with low humidity
• Areas with high solar radiation

They are less effective in high-humidity coastal climates.

Temperature Control Strategy

Effective temperature control includes:

• Activating fans at set temperature
• Gradual fan staging
• Combining with shade nets
• Monitoring real-time temperature

Thermostat-based control improves consistency.

Humidity Management in Fanpad Systems

While cooling reduces temperature, it increases humidity.

Monitor:

• Relative humidity levels
• Condensation on leaves
• Air movement

Excess humidity may require additional ventilation.

Automation & Sensor Integration

Modern systems use:

• Temperature sensors
• Humidity sensors
• Timers
• Automated controllers
• Smart climate management panels

Automation improves precision and consistency.

Maintenance of Cooling Pads

Regular pad maintenance includes:

• Cleaning dust accumulation
• Removing algae formation
• Checking water flow uniformity
• Replacing damaged pads

Pads usually last 3–5 years with proper care.

Maintenance of Exhaust Fans

Fan maintenance checklist:

• Clean blades
• Lubricate bearings
• Check belt tension
• Inspect motor condition
• Ensure secure mounting

Regular servicing ensures stable airflow.

Water Quality Management

Water used in pads must be:

• Low in dissolved salts
• Free from debris
• Clean and filtered

Poor water quality leads to scaling and reduced pad life.

Common Problems & Troubleshooting

Problem: Uneven Cooling

Cause: Air leakage or blocked pad

Solution: Seal structure and clean pads

Problem: High Humidity

Cause: Overcooling

Solution: Increase ventilation rate

Problem: Reduced Airflow

Cause: Fan malfunction

Solution: Inspect motor and belts

Energy Efficiency Considerations

Energy efficiency can be improved by:

• Using high-efficiency fans
• Installing proper insulation
• Maintaining sealed structure
• Using variable speed drives

Proper design reduces unnecessary energy use.

Seasonal Management Practices

Summer

• Run system continuously during peak heat
• Monitor water levels
• Clean pads regularly

Winter

• System rarely needed
• Protect pads from freezing
• Cover pads if not in use

Seasonal adjustment improves longevity.

Advantages of Fan & Pad Structures

• Effective temperature reduction
• Uniform cooling
• Improved air circulation
• Enhanced growing environment
• Suitable for large-scale structures

Limitations of Fanpad Systems

• Less effective in humid climates
• Requires continuous water supply
• Needs regular maintenance
• Higher energy consumption compared to natural ventilation

Understanding limitations helps better management.

FAQs

What is a fan and pad system?

 

A fan and pad system is an evaporative cooling setup used in greenhouses or polyhouses to reduce internal temperature by drawing air through wet cooling pads.

How much temperature can a fanpad system reduce?

 

In dry climates, it can reduce temperature by 8–12°C depending on humidity levels.

Is a fanpad system suitable for humid areas?

 

It is less effective in high-humidity conditions because evaporation rate decreases.

How often should cooling pads be cleaned?

 

Pads should be inspected monthly and cleaned as needed to prevent dust and algae buildup.

What water quality is required for cooling pads?

 

Clean, low-salinity water is recommended to prevent scaling and extend pad life.

Conclusion

Fan & Pad structures play a vital role in maintaining controlled climate conditions in protected cultivation systems. By understanding airflow principles, water management, installation standards, and routine maintenance practices, growers can ensure consistent temperature regulation and plant-friendly conditions throughout hot seasons.

At Nature Harvest Farms, structured climate management through well-designed fanpad systems supports stable growing environments and healthy crop development. When designed and managed correctly, a fanpad system becomes a reliable tool for creating a stable, controlled environment that supports healthy plant growth under challenging climatic conditions.