Abstracts Oral Presentations - Solar Food Processing Network

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International Solar Food Processing Conference 2009 SOLAR DRYERS FOR HIGH VALUE AGRO PRODCUTS AT SPRERI T. V. Chavda* and Naveen Kumar Sardar Patel Renewable Energy Research Institute, P.B.No. 2, Vallabh Vidyanagar– 388 120 (Gujarat), Tel : (02692) 231332, 235011, Fax : (02692) 237982 *E mail: tilak_chavda@yahoo.co.in, info@spreri.org Topic addressed: Solar food processing and back-up systems 1. Introduction Many agricultural, horticultural, chemical and pharmaceuticals products need drying to reduce their moisture content for various purposes like safe storage, easy handling, value addition, further processing and quality improvement. In order to achieve fast, reliable and hygienic drying, many in the organized sector employ mechanized dryers fueled through firewood, groundnut shells, saw dust, petroleum fuels like Low Density Oil (LDO) and diesel, Liquid Petroleum Gas (LPG) and electricity for drying the large quantities of low and high value products. The rise in cost of fuels and pollutants being added to the atmosphere, have resulted in a search of safer alternatives like solar drying. A solar dryer is an enclosed unit, to keep the product safe from damage, birds, insects and unexpected rainfall. The product is dried using solar thermal energy in a cleaner and healthier way. Solar dryers are found to be technically and economically feasible in many industrial and agricultural sectors. Roof space available in small-scale industries would normally permit installation of systems of one to two tones per day capacity. If a solar dryer were employed to replace an electrically operated dryer, the lifetime cost of solar dryer would only be a third of the electrical dryer at the present price of electricity. Similar analysis for diesel fuelled systems indicate that solar systems would cost only about half to that of diesel system. Solar dryers that have been developed at Sardar Patel Renewable Energy Research Institute (SPRERI) can be classified into direct and indirect systems. Direct dryers expose the products to be dried to direct sun light while the indirect systems protect the products from the exposure. Direct system, though are cheaper, but often lead to discoloration of the agro/chemical products resulting in poor quality of the final dried items. Thus, indirect type solar drying systems are highly suitable for industrial and commercial applications due to the good controls available, superior quality of the final dried products and scope of integrating with existing systems. Indirect type systems with thermal back-up are found to be the most adaptable and suitable for obtaining large quantities of high quality high value agro products. Mainly, all of the solar drying system consists of solar air heaters, drying chamber, blower, ducting, controls and thermal back up (optional). Solar air heaters are flat plate collectors/ packed bed collectors or unglazed collectors that can be installed on the ground, roof etc. In order to obtain maximum heat from solar energy, the solar air heaters need to be installed facing true south at a suitable tilt with respect to horizontal. Depending on the temperature of hot air, air flow rate and types of product to be dried, collectors are installed in series and parallel modes. It is essential that no shadow from any building or trees fall on the solar collectors throughout the year. 2. Summary SPRERI concentrated its work on indirect type forced circulation solar drying system and developed its first model with electrical back-up in its campus in the year 1995. This system was mainly used to generate basic data on solar drying of high value products including onion, Amla, potato, chilly, various other fruits, vegetables, ayurvedic and herbal products. Quality evaluations showed that the indirect solar dried products were far superior to the open sun dried ones in terms of good colour, texture and hygiene. The details of some of the 32
International Solar Food Processing Conference 2009 different models of indirect type solar dryers designed and installed by the institute in the field with financial assistance from different agencies like All India Coordinated Research Project on Renewable Sources of Energy of Indian Council of Agricultural Research, New Delhi (AICRP-ICAR on RES) and Ministry of New and Renewable Energy (MNRE) are given below. 1. Forced circulation glazed solar dryer: This dryer is suitable for drying high value agro products like ginger, tomato, amla etc. This is the most efficient design, though the cost of installation is also the highest. These types of dryers have been installed at M/s Shivam solar dryer, Ahmedabad (Fig.1 & 2), SPRERI, Vallabh Vidyanagar (Fig.3), M/s Handmade Paper Institute, Pune and M/s Swambe Chemicals, Vadodara. All the systems are working successfully. A temperature gain of 25°C could be easily achieved and the payback period for this type of system is around 3½ to 4½ years. Fig. 1 & 2 : Glazed solar air heater with LPG back up installed at M/s Shivam solar dryer Fig.3: Glazed solar air heater with electrical back up at SPRERI 2. Roof integrated unglazed solar dryer: This type of dryer is suitable for low temperature drying products like mushroom and leafy vegetables. Though the efficiency is lower but the cost of fabrication and installation is also lower and pay back period is also less than 2 years. This type of dryer has been installed at M/s Mashika Agritech, Vadodara as shown in Fig.4 and working satisfactorily. Total temperature gain of 10 to 15°C could be achieved. Fig.4: Unglazed solar air heaters with electrical back up at M/s Mashika Agritech, Vadodara 3. Roof integrated glazed-unglazed solar dryer: This type of system is installed at M/s Gujarat State Forest Development Corporation, Vadodara (Fig.5) for drying ayurvedic churnas and other herbal products. Its efficiency and pricing comes in the middle of above two types of the systems. The payback period for the system is around 3 years. Fig.5: Glazed & unglazed solar air heaters with electrical back up at GSFDC, Vadodara 33
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Abstracts Oral Presentations - Solar Food Processing Network

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