Introduction
Greenhouse equipment consists of tools and systems that serve to upgrade crop quality and quantity and to minimize the human labor. The main function of this equipment is to maintain the climate conditions constant during all seasons.
In this website we have tried to explain briefly what some of this equipment do and clarify their functions for the reader.

1. Cover
The components related to greenhouse cover are:

• PE plastic
• Polycarbonate sheets
• Motor and gear box to open/close top windows
• Top window rack and pinion
• Anti-insect net
• Side/Front windows motor and gear box roll up system
• Plastic clamps

The low costs of plastic, greenhouse structure and the speed of the installation process have made prefabricated Multi-span greenhouses popular among the farmers. Plastic cover, in spite of having a low cost performs the same functions as the glass cover and only it needs to be replaced every few years at relatively low cost. These plastic covers last 1-2-3-5 years in some areas with different thicknesses and resist the damaging effect of UV rays.

Polycarbonate sheets in wave or double layer shapes are also used to cover greenhouses. These sheets have lower costs than glass but higher costs than plastic, however because of the relatively long durability (10 years) and the high resistance against the wind and rain fall has made them popular to cover side walls and gables of greenhouses. Because of their low flexibility, they are seldom used to cover the roofs of greenhouses.

In all mechanized greenhouses top windows are used for natural ventilation system. These windows open and close along the greenhouse length. A rack and pinion mechanism including a control bar which transmits the power from a 3 phases motor and gear box through window arm opens and closes the top window. The time and area of open/close of the window is determined and controlled by climate control computer which in turn follows the parameters entered by the user or greenhouse production manager. For instance, when there is strong wind and the windows are open, the sensor outside the greenhouse sends the wind speed to the computer and the computer that is programmed (e.g. over 50km/h wind speed) to send a closing signal to the motor to close the windows.

The side/front windows in case they use plastic cover, use plastic roll up systems to open/close windows. They use a telescopic arm and a square profile to roll up plastic up to 120 meters of length.

When all greenhouse windows are open for ventilation, anti-insect nets are installed to prevent the entry of harmful insects and the exit of beneficial insects.

2. Cooling Systems
Greenhouse cooling system includes:

• Extractor fans
• Circulating fans
• Fog and fan systems
• Cellulose pads
• Cellulose pad frame
• Chiller systems

Various systems exist to reduce the temperature during the hot season being pad n fan the most common one. Greenhouses also require cooling for winter time. Cooling the greenhouse during the winter is done by horizontal airflow fans or circulation fans.

Evaporative cooling systems are based on the process of heat absorption during the evaporation of water.

Regardless of the summer cooling system used, a lower temperature can be achieved in a greenhouse that is full of plants as opposed to one that is only partially full. Plants transpire considerable quantities of water. As this water evaporates from crops, it absorbs heat from these plants and the surrounding air, thereby cooling both. Crops can transpire up to 6 kg/m2/day. Growers can take advantage of this cooling assistance by ensuring that transpiration is fostered. Substrate could not be allowed to dry excessively, and the greenhouse should be kept as full of plants as possible.

In the north of Iran where humidity is too high the pad and fan system does not cool the greenhouse. In these areas only the extractor and circulation fans can move the wet air and therefore cool the greenhouse by evaporation. In the south of Iran however because of high temperature and humidity chiller systems can be used to cool greenhouses.
The frame where the pads are situated is used both to hold the pads and for water circulation.

Fog and Fan system is also used to cool greenhouses and provide humidity which uses the same principle to cool the greenhouse.

3. Heating Systems
The equipment for heating greenhouses includes:

• Air heaters in different types and capacities
• Hot water boilers
• Thermostats and thermo switches

Heating equipment in winter time plays a critical role especially in conventional and non-mechanized greenhouses. The main function of this equipment is to protect the crops against the cold and to maintain a constant temperature in the greenhouse. If the structure cannot resist the snow load, even without a crop inside, using heating system is necessary. The best heating system in a greenhouse is hot water heating system as less humidity is evaporated. However the high cost of the system has caused it to be not as popular as air heating systems.

In hot air heating systems, the hot air is blown by high power fans and is distributed in the greenhouse using galvanized or plastic channel.

4. Irrigation
The irrigation equipment includes:

• Drippline with in line drippers
• Irrigation tapes with in line drippers
• Irrigation filters
• PE tanks for water and nutrients
• Hydroponic injection computer unit

Considering the shortage of water in most areas, drip irrigation is used for both outside and greenhouse crops.

The systems require relatively high investment in the beginning, but the reduction in water consumption, higher quality and quantity compensates for the high initial cost.

In this system usually a large water reservoir serves to hold the water for a few days consumption from which the irrigation water is driven to small tanks inside the unit. The large water reservoir can be an open pool or prefabricated water tank to be assembled in the site.

In drip irrigation system commonly the water is delivered to the small tanks where the nutrients are poured and mixed using air blower pumps. The computer then calculates the correct quantity of the mix and pumps it to the greenhouse. Different filters are used to clean the water in the path.

Hydroponic system can use various fertilizer tanks, connected to the main computer, at the same time. This machine pumps the mix into the irrigation red at predefined time intervals measuring and adjusting PH and EC of the water.

5. Shading and Energy Saving Screens:
Shading system includes:

• Shading and energy saving screen
• Motor and gearbox to open/close the screen
• Rack and pinion shading mechanism
• PET wire to hold the shade

Regular shades are mostly used to block certain amount of sun light that burns the plants. Aluminum double purpose shades perform two functions, to block the sun light and to prevent the escape of hot air during the cold winter nights.

The open/close system of shade is a back and forth mechanism that is driven by a relatively strong three phase motor and gear box. A motor could be enough for up to 7500 m2 greenhouse.

PET wire is used to hold the shade in perfect horizontal position which is installed below and above the shade. These polyester wires are tied on the 50*50 square profiles that support the whole system.

6. Hydroponic Substrate Equipment:
Hydroponic substrate system includes:

• Substrate black and white cover
• Coco peat, coco chips and perlite
• NPK fertilizer
• Grow bags
• Plastic pots

One of the advanced production systems is to eliminate soil and use neutral artificial material as substrate. Plastic cover is used to separate substrate from the soil. In hydroponic system the soils pests and weeds are practically eliminated, the water and fertilizer consumption is controlled and reduced as well. In this system, because the nutrients are delivered directly to the roots, the plant energy is used for development and products will have better quality and quantity. Plastic pots can also be used to hold the substrate and the plant.

The material used for substrate must be chemically neutral and be able to maintain high quantity of water. Coco peat which is the tissue surrounding the skin of the fruit, after being processed and compressed is a kind of substrate that can hold the water 10 times its own weight. Perlite or vermiculite are used to mix with coco peat and give the substrate additional favorable physical properties.

NPK fertilizer is used as plant nutrient mostly and sometimes the microelements are mixed and injected to satisfy plant needs.

Grow bags are long bags full of substrate on which holes are made where the seedlings can be planted.

7. Fog System
Fog system includes:

• Fog nuzzles
• Fog control equipment
• Compressor

Mist or fog systems are used to provide humidity and reduce temperature in hot and dry areas. These systems work with water and compressed air at the same time. Water and compressed air are delivered to the greenhouse using different piping systems. The greenhouse is divided in sectors which are controlled by electric valves and the main computer. The sensors transmit humidity content of the greenhouse to the computer and the computer sends the signal to the compressor and the water pump to inject air and water into the greenhouse. The air and the water meet inside the nuzzles and the nuzzle sprays the mist into the air. When the amount of humidity reaches de desired level, the sensor sends the data to the main computer and the computer sends a signal to stop the system. The humidity reduces the temperature as well specially if accompanied by circulation fans.

8. Climate Control System
Climate control systems include:

• Meteorological station that includes wind, rain, humidity, light and temperature sensors
• Temperature, humidity, light and CO2 sensor for inside the greenhouse
• Climate control computer
• Advanced climate control computers

9. Other Greenhouse Equipment
Some of the other equipment used in the greenhouse includes:

• Film tape to fix plastic cover
• Seedling trays
• Artificial light
• Shading paints and paint removers