greenhouse/polyhouse designs

GREENHOUSE TYPES, DESIGN AND PRECAUTIONS

Dr RK GuptaProfessor

Department of Agricultural EngineeringCSK HPKV Palampur

Greenhouse Principle

Short wave to long wave to entrap solar energy

1 4 8 10

Ultra violet Visible Infra red

Suppressed growth Normal growth Long and weak plants

X-ray 6x10-13 - 6x10-9m

UV 6x10-9 - 4x10-7m

Visible 4x10-7 - 8x10-7m

Infra red 8x10-7 - 8x10-4m

TV, Radio 8x10-5 - 8x105m

Photosynthetic & Visible Light

Far-red

USES OF GREENHOUSES• Growing high value vegetables

• Flowers

• Raising nursery of different vegetable crops

• Growing ornamental and medicinal plants

BenefitsRound the year production.

Export potential in floriculture

Suitable for adverse climatic conditions

More carbon dioxide available for plants

Higher produce inside the greenhouse

CLASSIFICATION OF GREENHOUSES(COST)

Low cost

Medium cost

High cost

CLASSIFICATION OF GREENHOUSES

• Low tunnels• Without cooling system• Fan pad system• Naturally ventilated

SHAPES OF GREENHOUSES

Soil, seed, water and environment

Environment o Temperature

o Relative humidity

o Evaporation

o Sunlight

CROP PRODUCTION FACTORS

NATURAL VENTILATION

NATURAL VENTILATION

• Percent of roof space ventilated has increased over time with design improvements

• Success is very crop specific• Even fully retractable roof designs are now

available• Cheaper to operate than active cooling

systems, but construction costs aren’t less expensive

Pad and Fan Cooling• Available for almost 50 years• Most common system for summer cooling• Originally the pad was composed of wood

shreds• Today it is composed of cellulose• Exhaust fans are placed on the opposite wall

GREENHOUSE FAN PAD SYSTEM

WOOD WOOL PAD SYSTEM

CELLULOSE COOLING PAD

SOIL, WATER AND SEED

• Good quality soil• Permanent source of water• Very good quality seed

Greenhouse Frameworks• The greenhouse framework supports the greenhouse

covering material.

Greenhouse Models

MATERIALS FOR FRAME

• Bamboo• Wood• MS Pipes• GI Pipes (Round and Square)• Aluminium

Greenhouse Frameworks

• The framework should be strong, yet allow the maximum amount of light to reach the plants.

• It is best if the framework requires little maintenance. • In high snowfall areas, it is important that the

framework be strong enough to withstand heavy snow loads.

• It should be capable of withstanding wind loads.

Greenhouse glazing• The covering of the greenhouse is referred to as the

glazing.• Considerations in choosing a glazing material include

durability, light transmission, cost, and affects on heating costs.

GLAZING MATERIALS

• Glass• UV Stabilized Polyethylene film

– Plain– Cross Laminated– Multi-Layered

• Poly-carbonate (Multi-Layered)

UV STABILIZED POLYETHYLENE

•Plain and Multi-Layered

•Available in various thicknesses

• Generally used for GH 200 micron (200 X 10-6 m) thick.

• High transmittance

• Three and five layered also available (Anti dust, anti dip, etc.)

• Cross-Laminated

•Available in gsm (g/sqm), 150 gsm is generally used.

• Greenhouse films are usually made from low density polyethylene (LDPE), linear low density polyethylene (LLDPE), ethylene-vinyl acetate copolymers (EVA) and similar polymers.

• The sun's ultra violet (UV) light transfers its energy to the polyethylene molecules causing them to become so energized that they are readily subject to oxidation.

• The mixing of UV stabilization chemicals at the time of production is to include components which will prevent as far as possible the onset of degradation process

UV STABILIZATION

• Several successful stabilizer like hindered amine light stabilizers (HALS) are used.

• HALS stabilizers protect greenhouse films by interfering with the propagation of free radicals.

• The HALS additive effectively restricts the multiplication of these free radicals. So a plastic film without proper UV stabilization (protection) will most certainly break down rapidly and leave the crop exposed.

• Hence all the greenhouse film manufacturers do stabilize their film against degradation due to solar radiation.

UV STABILIZATION

A cover of 200 microns thickness can be guaranteed for three years of service in the field against degradation due to UV.

UV STABILIZATION

• But a film which contains only a stabilization package, when used to cover a structure earmarked for growing crops, will not turn the structure into a greenhouse.

• At best the structure will be a “shelter”. There are many other parameters to be considered to call a UV stabilized polyethylene cover, a greenhouse cover.

• A crucial difference between a simple shelter and a greenhouse is that a greenhouse must be a heat trap. In a true greenhouse the escape of heat during the night is retarded in order to maintain optimal temperature for as long as possible.

Greenhouse Film

• The incident light can reach the plant as “direct” radiation or as “diffused” radiations which are at various angles with respect to one another and to a horizontal plane)

• A diffused film has an advantage over a clear film. Diffused light does not allow the shadow formation of the top layers of leaves to prevent essential light from reaching the lower leaves.

• The end result is a facilitation of an effective dispersion of total light to the darker areas inside the plant volume enhancing photosynthesis and hence the production of biomass.

Diffused film vs Clear film

Diffused film vs Clear film

• An UV blocker film does not allow the UV radiation (up to 381 nanometers where 400 nanometers marks the end of UV radiation and the beginning of visible light) to enter the greenhouse.

• Insects have compound eyes and they can see in the UV range as well as in the visible domain up to the red section (600-700 nanometers wave length).

• Blocking out the UV blocks significant part of the visible range of insects. Since the insects can not see many of the signals which they normally would see outdoors.

• When insects are under UV blocker film, a considerable decrease in white fly, thrips and other insect activity has been observed.

• Insects are the carriers and transmitters of many viruses & this film affects the insect activity it also is called Antivirus film.

UV Blocker (Antivirus film)

UV Blocker (Antivirus film)

Moisture inside the greenhouse condenses in the form of large drops of water on the inner side of the plastic cover, if the plastic is are untreated. This is undesirable because:

•The drops reflect back to the outer space a large portion of the incoming light.•The drops fall on the plants and serve as focal points for the spread of plant diseases.•water drops on the film focusing sunlight and scorching plant leaves

Anti Drip Film

• Slope of the greenhouse cover on the roof of the structure (a minimum of 22 degrees to the horizontal is desirable)

• Proper cladding of the film on the structure (to avoid folds, waviness and the like)

• The regime of periodical aeration of the greenhouse

• Height of the greenhouse

Requirement for Anti Drip Film

Anti Drip Film

An anti drip layer is always on the inner side of the plastic. It is very important to note that when a customer buys an anti drip film the anti drip side must be fixed on the inside facing the plants

Requirement for Anti Drip Film

Thermic FilmA thermic film is necessary for the places where the night temperature drops below the optimum temperature necessary for the plants. During the night, infrared additive creates a barrier to far infrared radiation (FIR: 5,000-20,000 nanometer) which is being emitted by all objects in the greenhouse. The net result is a decrease in the rate of temperature reduction during the night hours in the greenhouse. If the film cover is not thermic; the radiated energy will escape to outer space while the enclosed space within the greenhouse will eventually reach an equilibrium with the temperature of the air outside the structure.

Thermic Film

Five Layer Greenhouse sheet

Greenhouse Shade Nets• 30, 50,70 and

90 per cent shade

SITE SELECTION• Location

– Good Drainage – No obstructions (Shadow)– Connected to road

• Orientation– South facing

• Water– Permanent source

• Electricity

Greenhouse Orientation

Long side in EW direction (Facing south)


X 2X


• Locate the houses at a distance of 2 times the height of any object that might cast a shadow on the greenhouse

• Single ridge below 40 degrees north, run ridge north and south

Placement of houses for maximum light

SIZE

• Area required for production• Land available• Finance available

PROCEDURE FOR CONSTRUCTION

•Select the site

•Mark the boundary of greenhouse.

•Make excavation for foundation pipes

•Fix foundation pipes with cement concrete

•Fix all the hoops with foundation pipes

•Construct a ridge line by fastening/welding with hoops.

•Fix the glazing material with thin MS strip/screws

•Secure excess sheet in the channel around GH

•Construct a drainage channel around greenhouse.

Layout of GreenhouseSize 15 x 7 m=105 sq m

15 m

7 m

Make Diagonals Equal

Freshly cut bamboo culms of desired lengthare immersed with their butt ends in a solution of Boric acid: Borax (50:50) of about 10% concentration. The immersion ends should be done up to a length of about 30 cm of the but-end. The treatment may last for 8 to 12 days. In this process, stirring of the solution is demanded on every day to avoid sedimentation and also add small amount of the boric acid: Borax mixture to make up the uptake loss. This treatment is suitable for using as bamboo as greenhouse poles the end comes in constant contact with the ground

• Bamboo 3-6 years Old• Well treated• Dried In shade

SELECTED BAMBOO JOINTS

BAMBOO GREENHOUSE CONSTRUCTION

Damaged Due to Wind

Greenhouse Frame Maintenance• Check to make sure that any moving parts

such as greenhouse door hinges are not accumulating corrosion and if it looks like it may need oil for lubrication, don't put it off until later.

• Check for any stress fractures in the greenhouse frame and also check to make sure none of the fasteners holding your greenhouse together have come loose. If they have come loose, tighten them securely.

Greenhouse Frame Maintenance• If your greenhouse frame is painted wood,

check occasionally for any loose or blistering paint. If you find the paint is cracking or blistering, promptly scrape the paint off and allow to dry completely before sealing and re-painting the area.

• If your greenhouse frame is constructed of painted metal and you find rust forming, use a wire brush to remove any rust and then clean, prime & paint the affected area.

Greenhouse Cover MaintenanceYour greenhouse glazing should also be maintained regularly. •Should the glazing become dirty, your plants' ability to receive sunlight transmission is reduced considerably. Make sure that cleaning of your greenhouse glazing is a priority before winter. •If your greenhouse is covered with a greenhouse poly film, make sure to wash it thoroughly with a mild liquid soap and water solution.

Greenhouse Cover MaintenanceGreenhouse sheet should NOT be expected to perform longer than recommended by the manufacturer. Your greenhouse plants will only suffer if you put off replacing your greenhouse plastic past the recommended replacement interval due to decreased transmission of sunlight.

THANK YOU

greenhouse/polyhouse designs

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