Type of Hydroponics

   Hydroponic systems are distinguished by their being active or passive. In an active hydroponics system the nutrients are provided to the plants by making use of a pump while in a passive hydroponics system the passing of the nutrients to the plant depend upon the growing medium. However the passive Hydroponics system do not provide sufficient oxygen to the plant and hence the growth rate of the plants are not optimum. Hydroponic systems are also different on recovery and non recovery type. In recovery system the nutrients are recycled while in a non recovery system it is just the opposite. Here are some different types of hydroponics.

 

 1. Ebb and flow system
      Ebb and flow is one of the most preferred ways of doing Hydroponics gardening. This system is active as well as recovery type. Also known as flood and drain this system is quite easy to understand. The plant is kept in a reservoir containing nutrient solution. When the pump is started the nutrient are pumped in to the plant. After the water reaches the determined level, it is drained in to a river while the oxygen is sucked by the roots.

  

   
2. Nutrient film technique
    Nutrient technique is also a recovery type active Hydroponic system. In this kind of hydroponics system a submersible pump is used and the roots are suspended in a grow tube. The grow tube is in such an angle that the solution of the nutrients get recycled by flowing over the roots and then coming back to the reservoir. The oxygen requirement is solved by making use of air stones or air stones. This system is highly effective and a bit difficult to build. A single mistake can cause the whole plant to dry.

3. Floating Hidroponic

    
     This is the simplest of all active hydroponics systems. The platform that holds the plants is usually made of Styrofoam and floats directly on the nutrient solution. An air pump supplies air to the air stone that bubbles the nutrient solution and supplies oxygen to the roots of the plants. It can also called Water culture, it is the system of choice for growing leaf lettuce, which are fast growing water loving plants, making them an ideal choice for this type of hydroponics system. Very few plants other than lettuce will do well in this type of system. This type of hydroponics system is great for the classroom and is popular with teachers.

 4. Drip Irrigation

     This method isprobably the most widely used type of hydroponic system in the world.  Operation is simple, a timer controls a submersed pump. The timer turns the pump on and nutrient solution is dripped onto the base of each plant by a small drip line.

    Drip irrigation is the most efficient method of irrigating. While sprinkler systems are around 75-85% efficient, drip systems typically are 90% or higher. What that means is much less wasted water! For this reason drip is the preferred method of irrigation in the desert regions of the United States. But drip irrigation has other benefits which make it useful almost anywhere. It is easy to install, easy to design, can be very inexpensive, and can reduce disease problems associated with high levels of moisture on some plants.

5. Aeroponics

    This method is probably the most high-tech type of hydroponics gardening. Like the N.F.T. system the growing medium is primarily air. The roots hang in the air and are misted with nutrient solution.

     The misting are usually done every few minutes. Because the roots are exposed to the air like the N.F.T. system, the roots will dry out rapidly if the misting cycles are interrupted.

A timer controls the nutrient pump much like other types of hydroponic systems, except the aeroponics system needs a short cycle timer that runs the pump for a few seconds every couple of minutes.

Source 1

Source 2

 

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Type of Greenhouse

Greenhouses come in an array of styles, sizes, materials and colours so there is sure to be one to suit every garden and every gardener’s pocket. While many of these differences are largely a matter of cosmetic appeal or personal preference, a few can have a real bearing on making the all-important decision as to which one to buy.

Greenhouses give you the opportunity to control the growing seasons for your plants. You can also grow plants that would normally not survive in your climate. Glass is the most traditional material for greenhouses, but they can be made of plastic or various types of acrylic surfaces as well. Greenhouses are available in several different styles, each of which meets different spatial, economic and planting needs. 

Lean-To Greenhouse

Lean-to greenhouses are essentially half of a traditional greenhouse building attached to a house or other building at a doorway. This type of greenhouse is generally split along the ridge line and can only be as tall as the supporting wall since they are basically cut in half. These greenhouses are useful when you have limited space available for a full greenhouse. They do have more limited space, and temperature control as well as ventilation are more difficult to maintain. This style is the least expensive type of greenhouse.  The ridge of the lean-to is attached to a building using one side and an existing doorway, if available. Lean-tos are close to available electricity, water and heat. The disadvantages include some limitations on space, sunlight, ventilation, and temperature control. The height of the supporting wall limits the potential size of the lean-to. The wider the lean-to, the higher the supporting wall must be. Temperature control is more difficult because the wall that the greenhouse is built on may collect the sun's heat while the translucent cover of the greenhouse may lose heat rapidly. The lean-to should face the best direction for adequate sun exposure. Finally, consider the location of windows and doors on the supporting structure and remember that snow, ice, or heavy rain might slide off the roof or the house onto the structure.

Even span Greenhouse

An even-span is a full-size structure that has one gable end attached to another building . It is usually the largest and most costly option, but it provides more usable space and can be lengthened. The even-span has a better shape than a lean-to for air circulation to maintain uniform temperatures during the winter heating season. An even-span can accommodate two to three benches for growing crops. The even-span greenhouse gives you more usable space, and you can add on to the unattached end. The even-span greenhouse gives you more uniform temperature control for the greenhouse and allows more air circulation.

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Nutrient Solution Pattern

It is nutrient solution pattern in NFT Beds which is simulated by CFD. The square indicated that the area of root zone.

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Abstract of Research

MATERIAL SELECTION ON NUTRIENT FILM TECHNIQUE (NFT) BEDS USING COMPUTATIONAL FLUID DYNAMIC  (CFD)

Abdul Wahhaab¹, Herry Suhardiyanto¹, and Ahmad Indra Siswantara²

1 Departement of Mechanical and Biosystem Engineering, Faculty of Agricultural Technology, Bogor Agricultural University, IPB Dramaga Campus, PO BOX 220, Bogor, West Java, Indonesia

² Departement of Mechanical Engineering, Faculty of Engineering, University of Indonesia, Depok, West Java, Indonesia

ABSTRACT

Nutrient Film Technique (NFT) is one of hydroponic technology that nutrient solution circulate in a crop's root zone at anytime with 3 mm tickness.  A computer model has been developed to simulate the thermal distribution of NFT beds using Computational Fluid Dynamic (CFD).  The objective of this research are to develop a simulation model of moving heat flow of nutrients in the NFT bed in several types of materials with a CFD program and to determine the optimal type of materials in the design of beds.  The crop that is used as a object of a research is a tomato.  Tomato grown in two different beds, with and without zone cooling.  CFD use for simulate heat transfer on these beds and simulate on model of beds with several different materials.

The results showed that the distribution of nutrient solution temperature along the beds change over time follow the greenhouse temperature.  The simulation on different material of beds like PVC, fiberglass, glass, asbestos, porcelain, cement, and styrofoam showed that fiberglass is the highest temperature 28.9-32.3 ^oC and porcelain is the lowest temperature 28.9-31.2 ^oC. Otherwise, the lowest heat transfer coefficient is fiberglass and the highest is porcelain. High or low heat transfer coefficient will affect the release of heat from inside the beds to the environment.  According to analysis, the optimum of material which used for NFT beds design are cement, porselaian, and glass.

Keywords: Material, NFT Beds, CFD

For full paper, you can download it on 'download category'

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Greenhouse

A greenhouse (also called a glasshouse) is a building where plants are grown. These structures range in size from small sheds to very large buildings. A miniature greenhouse is known as a cold frame.

A greenhouse is a structure with a different types of covering materials, like glass or plastic roof and frequently glass or plastic walls; it heats up because incoming visible solar radiation (for which the glass is transparent) from the sun is absorbed by plants, soil, and other things inside the building. Air warmed by the heat from hot interior surfaces is retained in the building by the roof and wall. In addition, the warmed structures and plants inside the greenhouse re-radiate some of their thermal energy in the infra-red, to which glass is partly opaque, so some of this energy is also trapped inside the glasshouse. However, this latter process is a minor player compared with the former (convective) process. Thus, the primary heating mechanism of a greenhouse is convection. This can be demonstrated by opening a small window near the roof of a greenhouse: the temperature drops considerably. This principle is the basis of the autovent automatic cooling system. Thus, the glass used for a greenhouse works as a barrier to air flow, and its effect is to trap energy within the greenhouse. The air that is warmed near the ground is prevented from rising indefinitely and flowing away.

Although there is some heat loss due to thermal conduction through the glass and other building materials, there is a net increase in energy (and therefore temperature) inside the greenhouse.

Greenhouses can be divided into glass greenhouses and plastic greenhouses. Plastics mostly used are PEfilmPC or PMMA. Commercial glass greenhouses are often high tech production facilities for vegetables or flowers. The glass greenhouses are filled with equipment like screening installations, heating, cooling, lighting and may be automatically controlled by a computer. and multiwall sheet in

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