Greenhouses are known to be the modern outlook for the agronomical industry in terms of high-end yield especially in the regions where climatic conditions are not stable like in the Middle East, Europe, and United States. Crop optimization is one of the major challenges facing the farmers and the controlled production centers can dictate this difficulty in the upcoming market. Greenhouses are considered as the high -tech production centers which can support the food industry to have a green revolution through the mass production of the vegetables and spices. Properly designed commercial greenhouses can increase the yield by minimizing the operational cost especially in terms of reducing the energy consumption. In order to have a properly designed greenhouse, the selection or up gradation of the shade structures can play a vital role. Conventional greenhouses are made of polycarbonate sheets and in some cases the polyhouses by using simple polyethylene sheets. In this scenario, the main drawbacks were the energy consumption, operational expenses and the effectiveness of the indoor temperature control. Custom designed shades based on the crop requirements can provide high production rate by reducing the energy consumption. The detailed microstructural analysis in conjunction with the photosynthesis demand can provide a better selection of the shade-net or curtains. Greenhouse shade structure can be upgraded using the motorized specially designed nets or by using thermal-reflective screens.
This up gradation can provide four stage advantages. In stage one this can decrease the 50% of heat energy and which will save the HVAC operational cost. During the stage, two better temperature control during the day and night will provide a good environment to provide proper PAR (Photosynthetically Active Radiation) for photosynthesis, in the wavelength range of 400 to 700 nanometer. Third and fourth stages are the protection from the frost as well heat stress during the different climatic conditions.
In the present market condition, the commercial greenhouses are being built in large scale by neglecting the energy saving options in shade structures. The commercial greenhouses using the upgraded shade structures can save the operational cost by 25 to 30%. Selection of this shade-nets or curtains can be done using the detailed microstructural analysis of the material. Shade-nets/curtains can be controlled manually, mechanically or can be automated in large-scale greenhouses. Flowering dates in the plants can be accelerated using the shading materials and delayed by the use of control treatment, which coincides with the results obtained in the previous studies .
This has proven with high land experiments . Greenhouse shade nets are used in order to protect crops and plants from adverse weather conditions, animals and pests, besides providing suitable conditions for plant growth. The essential performance properties required for greenhouse shade nets are the resistance to solar radiation and weathering. The intensity of the Photo Synthetically Active Radiation (PAR) directly influences plant growth. Other nonvisible radiations are ultraviolet (UV), infrared (IR) and far infrared (FIR). Polypropylene and polyester are more resistant to UV radiation than polyethylene, which is resistant to radiations in the visible region. The use of greenhouse shade nets in outdoor conditions also requires them to be resistant to abrasion.
The objective of the present work is to examine the effectiveness of the properly selected shade-net/curtain in commercial greenhouses in terms of high yield energy savings. This study was conducted to compare the traditional polycarbonate sheet with the innovation of properly designed shade curtain made-up from high-density polyethylene (HDPE) fiber reinforced material discover the best shading method for plant growth in an ideal energy conservation scenario. The study was conducted in the two identical greenhouses (planted with lettuce crop) located in Al Khawaneej farm in the Emirate of Dubai in the United Arab Emirates. Yield versus the energy consumption has been observed in a period of time and obtained the reduction in energy consummation of almost 20 to 30 %.