ABSTRACT INNOVATIVE SOLAR TUNNEL DRYER MGIRED Journal Volume 3(2) : 28-32 ISSN 2393-9605 Food preservation or agro crop preservation means avoiding the microbial growth due to presence of moisture content in agro product. Food preservation techniques include pickling, sugaring, canning, dehydration, freezing, etc. Dehydration of fruits and vegetables is a promising food processing technology that increases shelf life of products for almost a year. It is a value addition process that can save 1/3rd losses of seasonal agro-products. Solar dryers can be used to carry food dehydration without relying on electricity. India is primarily an agriculture-dependent country. Indian rural economy is also improving at an accelerated rate with each passing day. The pattern of crops is changing fast with the farmers realizing that they cannot survive solely on conventional crops. This awareness is making farmers look towards horticultural crops such as fruits, vegetables spices, etc., which yield high income. This paper proposes a simple and innovative solar tunnel dryer; this technology utilizes the energy of the sun and wind to dry agricultural products, preparing them for proper storage, processing and export. Key words: Solar Dryer, Solar photovoltaic module, DC blower, UV-stabilized polythene sheet, drying chamber. INTRODUCTION Shanthi G Deputy Director (Solar), MGIRED e-mail : shanu.milu@gmail.com Since time immemorial, man has been using sun as a source of energy. This is one of the most prevalent, simple and cost effective methods practiced by most developing and underdeveloped countries, especially in the tropical regions of the globe, where good sunshine hours prevail throughout the year. Solar photovoltaic technology and solar thermal technology have to be used in right methods and places in order to realise the self sufficiency in energy especially in food processing industry; this paper has made an attempt to blend these both technologies to develop a unique method for drying agro products. 28
Original Research Article Shanthi Food commodities are laid on a platform with or without intermittent stirring. The sun's heat not only reduces the moisture level as desired, but also kills insects present in the food product. The crop is spread in an even layer on tables or drying racks inside the tunnel. The air below the semi-transparent collector is heated by the sun and spreads throughout the tunnel. The increased temperature decreases the relative humidity of the air, thereby allowing the air to more efficiently dry the crop. The moist air is further removed through the exhaust. CONSTRUCTION The major part of this drier is the outer cover which allows the sun's rays to pass through and dry the agro crops. Environmental conditions that could be damaging to outer cover include exposure to UV, moisture, chemicals, temperature and oxidation. Not all grades of thermoplastics are suitable for outdoor applications. Materials that are not UV stable will change both in appearance and molecular structure when exposed to UV, and over time can become brittle, crack, change colour, warp, etc. The cover of the solar tunnel dryer is a poly house framed structure with UV-stabilized polythene sheet of few microns thickness. The base is made up of iron legs and frame by welding the L-angle MS sections. Over the frame a plywood sheet is laid which is an insulating material, over this is put a black HDPE sheet, which can withstand higher temperatures. The material has benefitted from discussions about possible health and environmental problems caused by PVC and Polycarbonate, as well as its advantages over glass, metal, and cardboard. The crops to dry are spread over the sheet, over which the cover is kept. It is ensured that the cover and the base fit in well, thus ensuring vacuum in the drying chamber. A DC blower of 5.1W capacity is fixed on the higher side of the cover to ensure that the humid air inside the drying chamber is exhausted. There is a 12 Wp Solar photovoltaic module which supplies about 0.65 A of current at peak sunlight, even at partial sunshine it supplies about 0.35 A which is sufficient for the blower to function. Technical Characteristics The product is easily adaptable to the local environment and locally produced crops. The volume of the drying chamber is increased by increasing the height of two limbs of the outer cover, this can be observed in fig 1(a) 29
Innovative Solar Tunnel Dryer Dimensions of the cover Length 200 cm Height 1 55 cm Height 2 22 cm Figure (a), 1(b) Dimensions of the base Length 201 cm Height 8 cm Breadth 96 cm Breadth 96 cm Exhaust fan : 5.1 W, 12 V DC Solar PV Module : 12 W, 16.4 V DC Volume of the drying chamber : 0.739 cubic meters Weight of the dryer : 20 Kgs (Including weight of both the cover and the base) Cost of construction Sl. Component Approximate Cost No. 1. Solar module poly crystalline module will cost approximately Rs.600/- 2. Blower fan Rs.550/- 30
Original Research Article Shanthi 3. UV-stabilized 200µ thickness was purchased Rs.500/-. polythene sheet 4. Mild Steel sections 15kg were utilized therefore cost of the sheet can be estimated as Rs.630/- 5. HDPE sheet 3 mtrs cost Rs.320/- Total cost for construction of the solar dryer = Rs.2,600/-( approximately) Usability of the Innovative Solar Tunnel Drier It was observed that 20 Kg of Pongamia seeds lost 600 grams of weight when exposed to sunlight indirectly via the solar drier for 10 hours. Further observations with food crops like tomato and cash crops like areca nut etc, would give better observable results. Solar dryer can save fuel and electricity and drying time in solar dryer is reduced in comparison to open drying method. Fruits and vegetables dried in solar dryer are better in quality and hygienic than dried in open. Materials required for fabrication of solar dryer are locally available and the use of solar dryer involves no fire risks. The dryers can be connected in series and hence its capacity can be enhanced as per requirement and it can be dismantled easily so that its transportation is easy from one place to another. Since this particular dryer is having a permanent metal base though the cover gets torn in the course of time, it can be replaced and thus the whole structure is a permanent one which can be used to dry the agro products. CONCLUSION AND FUTURE STUDY A solar drying system, particularly for agro-products and marine products, is viable particularly in developing countries where labour costs are low and cost of fossil fuel energy is very high. The newly developed tunnel dryer is an idea obtained from the many existing solar tunnel type dries which are also called as green house dryers. This is an attempt to construct a solar dryer which can be a cost effective and built with locally available material. 31
Innovative Solar Tunnel Dryer Further the other foods or seeds for manufacturing Biodiesel will be dried using the solar dryer and will be tested for the performance suitable graphs and outcomes can be thus recorded on the basis of which a technical publication will be done in the near future. REFERENCES [1] Bano, T. etal (2015), Innovative Solar Dryers For Fruits, Vegetables, Herbs And Ayurvedic Medicines Drying 2015, International Journal of Engineering Research and General Science Volume 3, Issue 5, September-October, 2015 ISSN 2091-2730 [2] Jackson TH, Masry ME (1977). Sun Drying of Fruits and Vegetables in Ethiopia. Food Processing Section (Nazreth), Addis Ababa, Ethiopia, pp. 18-40. [3] https://en.wikipedia.org/wiki/food_preservation#irradiation 32