Greenhouse Climate Control: Light, Temperature, and Humidity Management

Posted on Oct 29, 2024 in Physics

Control of Light

Using shaders, mesh, and covers, artificial light contributes to influencing plant growth.

Mesh Shading

  • Polypropylene woven raffia: Available in different colors, especially white and black.
  • Transparent polyester: High opacity to longwave radiation, preventing heat loss at night during the cold season. Used to retain heat accumulated during the day. Also used to protect from excessive solar radiation.

Whiteners (Covers)

Used to reduce solar radiation and luminosity during periods of excessive heat. “White of Spain” is a commonly used whitening product applied by spraying.

Artificial Light

  • Thermoradiation: Radiation emitted by a body based on its heat capacity.
    • Incandescent lamps
    • Halogen incandescent lamps
  • Luminescence: Electromagnetic radiation produced by exciting electrons in atoms.
    • Fluorescent lamps

Heating

Used to heat the ground or air inside the greenhouse.

Underfloor Heating

Expensive, used for highly profitable crops.

Hot Bed

Commonly used for multiplication, featuring a water pump, electric resistance, thermistor-controlled probe, programmer/timer, expansion vessel, safety valve, check valve, and air vent.

Air Heating

  • Stoves: Produce heat to warm greenhouses.
  • Heaters: Use hot water or steam.
  • Central heating: Distributes hot water or low-pressure steam.

Light Spectrum

Low-pressure lamps have a yellow light spectrum, while high-pressure lamps have a wider band, producing more colors.

Magnitudes of Light

  • Luminous flux (f): Amount of radiant energy visible to the human eye for one second.
  • Light output (h): Ratio of luminous flux to electric power (Watts).
  • Illuminance (E): Ratio of luminous flux to the surface area it illuminates.

Objectives of Artificial Light

  • Increase photosynthesis
  • Influence photoperiodism

Control of Moisture and Temperature

Cooling System (Cooling & Humidification)

Reduces temperature by passing forced air flow from outside through a wetted surface, cooling and humidifying the air. Panels are moistened on one wall, and exhaust fans are installed on the opposite wall.

Cooling System Materials

  • Panels
  • Water tank
  • Booster pump
  • Extractor fan

Mist System (Fog)

Increases humidity and lowers temperature by creating a spray or mist. Used in plant propagation to prevent desiccation.

Mist System Components

  • Pressure pump
  • Nozzles or foggers
  • Water supply
  • Automation

Ventilation

Natural Ventilation

Uses windows in sidewalls or zenith windows in the roof to create airflow.

Forced Ventilation

Uses fans or extractors to remove hot air and replace it with outside air.