3. greenhouse types - II.pptx 6th sem portion

Greenhouse classification

1. GREENHOUSE TYPES

2. Types of greenhouse Greenhouse structures of various types are used for crop production. There is no single type of greenhouse which can be considered as best. There are advantages in each type for particular objective or application. Different types of greenhouses are designed to meet specific needs.

3. Greenhouse types Based on shape Based on utility Based on construction Based on covering material Based on cost of construction

4. Based on shape Lean to type Even span type Uneven span type Ridge and furrow type Saw tooth type Quonset type

5. Lean to type greenhouse

6. Lean to type greenhouse This design is used when greenhouse is placed against side of an existing building. It is built against a building using existing structure for one or more of its sides. Roof of building is extended with appropriate greenhouse covering material and area is properly enclosed. Typically facing south side. Width is limited to single or double row plant benches with total width of 7 – 12 feet. It can be as long as building it is attached to. It should face best direction for adequate sun exposure.

7. Lean to type greenhouse Advantage Usually close to available electricity, water and heat. Least expensive structure. This design makes best use of sunlight Minimizes requirement of roof supports. Disadvantage Limited space Limited light Limited ventilation and temp. control Height of supporting wall limits potential size of design.

8. Even span type greenhouse

9. Even span type greenhouse Standard type and full size structure Two roof slopes are of equal length(pitch) and width This design is used for greenhouse of small size and is constructed on level ground. 2 – 3 rows of plant benches These may be of several single and multiple span types. For single span types, span varies from 5 – 9m whereas length is around 24m. Height varies from 2.5 – 4.3m

10. Even span type greenhouse Comparison with lean to type Cost is more than lean to type But greater flexibility in design and provides space for more plants. Due to size and greater amount of exposed glass area, heat cost will be more. Design has better shape for air circulation to maintain uniform temperatures during winter.

11. Uneven span type greenhouse

12. Uneven span type greenhouse Constructed on hilly terrain Roofs are of unequal width making structure adaptable to side slopes of hill. This type of greenhouse is rarely used now – a – days as it is not adaptable for automation.

13. Ridge and furrow type greenhouse

14. Ridge and furrow type greenhouse These are A designed greenhouse connected to one another along length of eave. Eave serves as furrow or gutter to carry rain and melted snow away. Side walls are eliminated between greenhouse Structure with single large interior Consolidation of interior space reduces labour , lowers cost of automation, improves personal management and reduces fuel consumption as less exposed wall area through which heat escapes.

15. Saw tooth type greenhouse

16. Saw tooth type greenhouse The structure is similar to ridge and furrow type except there is a provision for natural ventilation in this type. Specific natural ventilation flow path develops in a saw tooth greenhouse.

17. Quonset type greenhouse

18. Quonset type greenhouse This type uses pipe arches or trusses for support. Pipe lines run along length of greenhouse. Covering material generally used is polythene sheet. Typically less expensive compared with gutter connected greenhouses Useful when small isolated area is required.

19. Quonset type greenhouse These houses are connected either in free standing style or arranged in interlocking ridge and furrow. This type provides sufficient area to plants to grow between overlapping portions of adjacent houses in interlocking ridge and furrow. It is best adapted to automation and movement of labourers.

20. Based on utility Design of such greenhouses depends on functions or utilities. Based on artificial cooling and heating, greenhouses classified into Greenhouses for active heating Greenhouses for active cooling

21. Greenhouses for active heating In winter, during night time, air temperature inside greenhouse decreases. To avoid cold bite to plants due to freezing, some amount of heat has to be supplied. To compensate heat loss, various methods have been adopted Using double layer polythene, thermo pane glass Using heating systems like unit heaters, central heat, radiant heat and solar heating system.

22. Greenhouses for active cooling In summer season, for plant survival, it is necessary to reduce the temperature of greenhouse for effective crop growth. Suitable modifications are made in green house so that large volumes of cooled air is drawn into greenhouse. This type of greenhouse consists of Either evaporative cooling pad with fan Or fog cooling system This greenhouse is designed to permit roof opening of 40% and in some cases nearly 100%.

23. Based on covering materials Covering materials are major and important component of greenhouse structure. They have direct influence on greenhouse effect inside the structure and they alter air temperature inside greenhouse. Types of frames and method of fixing also varies with covering material. Based on type of covering material, greenhouses classified as Glass greenhouse Plastic film greenhouse Rigid panel greenhouse

24. Glass greenhouse Only glass as covering material was used prior to 1950. Advantage of greater interior light intensity. These greenhouses have higher air infiltration rate which leads to lower interior humidity and better disease prevention. Lean to type, even span, ridge and furrow type designs are used for glass greenhouse construction.

25. Plastic film greenhouse Flexible plastic films like polyethylene, polyester and polyvinyl chloride are used as covering materials Plastics have become popular as they are cheap and cost of heating is less when compared to glass greenhouses. UV stabilized film can last up to 4 years only. Disadvantage – short life Quonset and gutter connected design suitable for this covering material.

26. Rigid panel greenhouse Polyvinyl chloride rigid panels, fibre glass reinforced plastic, acrylic and polycarbonate rigid panels are used as covering materials. These panels can be used in Quonset and ridge & furrow type frames. This material is more resistant to breakage and light intensity is uniform throughout greenhouse. High grade panels have long life up to 20 years. Disadvantage – Accumulation of dust and harbour algae Darkening of panels and reduction in light transmission Chance of fire hazard

27. Based on construction Type of construction is predominantly influenced by structural material. Span of house states the selection of structural members and their construction. Higher span, material should be stronger and more structural members are used to make sturdy truss type frames. For smaller spans, simpler designs like hoops can be used. Based on construction, greenhouses broadly classified as Wooden framed greenhouse Pipe framed greenhouse Truss framed greenhouse

28. Wooden framed greenhouse In general, greenhouse with span less than 6m, only wooden framed greenhouses are used. Side posts and columns are constructed of wood without use of truss. Pine wood is commonly used Inexpensive Possess required strength Timber locally available with good strength, durability and machinability also can be used.

29. Pipe framed greenhouse Pipes are used when span is around 12m. In general, side posts, columns, cross ties and purlins are constructed using pipes. Pipe components are not interconnected but depend on attachment to sash bars for support.

30. Truss framed greenhouse Truss frames are used when span is greater than or equal to 15m. Flat steel, tubular or angle iron are welded together to form truss. Struts – support members under compression Chords – support members under tension Angle iron pipeline running throughout length of greenhouse are bolted to each truss. When wide truss greenhouses of 21.3 m or more are to be constructed, columns are used. Most of glass houses are of truss frame type as these are best suited for pre fabrication.

31. Based on cost of construction Cost of construction depends on material used and level of technology used in greenhouse Based on cost of construction, greenhouses classified into Low cost or low technology greenhouse Medium cost or medium tech greenhouse High cost or high tech greenhouse

32. Low cost greenhouse Simple framed structure made up of locally available materials like bamboo, timber etc. with UV stabilized film as cladding material. Has no specific control device for regulating environmental factors inside. Has got simple technique of opening and closing of side wall for regulating temperature and humidity.

33. Low cost greenhouse Light intensity can be controlled by providing different shade nets. This type of greenhouse is useful for high rainfall and cooler regions. Such structures in high rainfall areas are called rain shelters which are useful for crop production. Low cost greenhouse are most useful for production of vegetable seedlings.

34. Medium cost greenhouse This type of greenhouse is operated manually or by semi automatic control device leading to minimum investment. Framed structures are made of GI pipes. Structures are connected through nut and bolt system and are fixed stable on ground so that it does not get disturbed by force of wind.

35. Medium cost greenhouse Evaporating cooling pads and misting arrangements help in maintaining favourable humidity inside greenhouse. Greenhouse requires a lot of attention and care, it is difficult to maintain a particular environment which the plant needs. It also requires more man power to control all the equipments as these devices are either manual or semi automatic. These type of greenhouses are suitable for dry and humid climates.

36. High cost greenhouse There is a control system consisting of sensor, computer, operator and a signal receiver. All control systems are aimed at satisfying conditions provided by sensor. It helps in sensing and measuring variable parameters and compares measurements using standard values. Whole system is controlled by help of micro processor. Technologies involved in both high and medium cost greenhouses are nearly similar Difference - high cost has automatic control system

37. High cost greenhouse This type of greenhouse is suitable for any climatic condition. Crops coming under domain of floriculture are usually sensitive to temperature and humidity, so high tech greenhouses are most suitable for these type of crops. Disadvantages Demands high initial cost Needs skilled and experienced operators Higher cost for maintenance, care and operation.

38. Based on climatologically conditions Winter greenhouse Constructed in those countries where outside ambient temperature is very low compared to requirement of plant growth. It is required to catch maximum incoming solar radiation. So south side is usually made of glass, sometimes doubly glazed and interior surface of north wall is painted white. Use of moveable insulation to prevent unwanted heat loss, provision for storage facilities for sundown hours. Windows are provided in east and west walls for ventilation. Summer greenhouse Constructed in those countries where outside ambient temperature is very high compared to requirement of plant growth. One has to design greenhouse such that inside temperature will not reach very high. This type of greenhouse has two sets of windows placed in south and north wall. These windows can be used to cool greenhouse by free convection. Another way is to duct windows in south walls through which air is blown after it has evaporative cooled by passing through evaporative pads.

39. Based on environmental control Naturally ventilated Do not have any environmental control system except provision of adequate ventilation. Environmental controlled Helps to extend growing season or permits off season production by way of controlling light, temperature, humidity, carbon dioxide level and nature of root medium.