What is the difference between a fan and pad cooling system and a fogging system in greenhouses?

First: The fan and pad cooling system

Mechanism of operation:

• A row of evaporative pads is installed on one side of the greenhouse.

• Outside air is drawn through these water-soaked pads.

• The water evaporates from the surface of the pads, lowering the air temperature.

• Fans (installed on the opposite side) draw this cool air in and distribute it inside the greenhouse.

Advantages:

✅ Significantly lowers the temperature (5–13°C depending on the climate).
✅ Highly efficient in dry and hot areas.
✅ Uniform cooling if the fans and pads are properly designed.

Challenges:

❌ Performance decreases in areas with high humidity.
❌ Requires regular maintenance of the pads to prevent clogging or algae growth.

Second: Fogging System

Mechanism of Operation:

• It relies on spraying very fine mist (micron droplets) of water inside the greenhouse.

• When this mist evaporates, it absorbs heat from the air, lowering the temperature.

• Requires high water pressure and special nozzles to generate fog.

Advantages:

✅ Consumes less water compared to pads.
✅ Provides additional humidification, useful in very dry greenhouses.
✅ High flexibility and can be operated as needed (cooling + increasing humidity).

Disadvantages:

❌ Limited effectiveness in reducing temperature compared to Fan & Pad (usually only 3–7°C).
❌ May lead to excessive humidity inside the greenhouse, increasing the risk of fungal diseases.
❌ Requires filters and careful maintenance of the nozzles to avoid clogging.

Conclusion:

• If the greenhouse is in a hot, dry area, Fan & Pad is best.

• If the greenhouse needs light cooling and increased humidity, Fogging may be more appropriate.

• In some large projects, the two systems are combined for optimal results.