Development and Performance of a Solar Biomass Integrated Crop Dryer for Agri and Medium Scale Food Processing Industries

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Development and Performance of a Solar Biomass Integrated Crop Dryer for Agri and Medium Scale Food Processing Industries

1 Mrs. R. Priya,

Assistant Professor, Dept of EEE, Manakula Vinayagar Institute of Technology,

Puducherry

Abstract – In the larger parts of Asian-Pacific countries, agriculture represent the foremost part of economy. Almost 75% of the working population is employed in farming and agro connected works. In spite of these large numbers, food production still does not meet the needs of population. The lack of appropriate preservation and storage systems leads to extensive losses, thereby reducing the food supply significantly. The successful operation of post-harvest technologies is essential towards the food availability and security worldwide. Preservation of fruits, vegetables and food are essential for keeping them for a long time without further deterioration in the quality of the product. Several process technologies have been employed in an industrial scale to preserve food products; the major ones are canning, freezing, and dehydration. Among these, drying is especially good since it offers a highly effective and practical means of preservation to reduce postharvest losses and offset the shortages in supply. In many countries, agricultural products are dried under the open sun which degrades the quality of the dried products due to impurities and uneven drying rates. In order to be marketable on the world market, it has to meet high quality standards. Otherwise the price will decline resulting in low profits for the exporting country and the producing farmer. To produce high quality products for the world market as well as to reduce losses, the development of suitable dryers for tropical regions is urgently needed. Tropical countries are blessed with solar energy .It is one of the promising heat sources for meeting energy demand without putting adverse impact of environment. Biomass energy is also employed as auxiliary heating source due to its availability and cost effectiveness in rural areas. This paper describes a mixed mode natural convection of solar dryer integrated with a simple biomass burner for drying various agricultural products such as fruits, vegetables, medicinal plants etc. The dryer was designed for small-scale commercial producers of agricultural products in non-electrified locations. Commercial sizes of the solar dryer can be improved and produced for community level cooperative use and for prospective investors to fast track agricultural development in the rural areas.

Keywords: Food preservation, Post harvest Technologies, Open sun drying and Solar dryer, Biomass burner

  1. BACKGROUND

    In various parts of the world, awareness is growing up in renewable energy stream. Renewable sector plays a significant role in extending the available technological aspects to the field of agriculture to increase the productivity. Although India is a major producer of horticultural crops, many Indians are unable to obtain their

    2 Mr. P. L. Santhanakrishnan,

    Assistant Professor, Dept of EEE, Manakula Vinayagar Institute of Technology,

    Puducherry

    daily requirement of fruits and vegetables and the Human Development Index (HDI) is very low. Considerable quantities of fruits and vegetables produced in India go to waste due to Poor infrastructure for storage, processing and marketing, improper postharvest operations and the lack of processing. This results in a substantial gap between net food production and net food availability. Reduction of postharvest losses is very important in order to increase the food availability. Conventional techniques used in food preservation are salting, drying, refrigeration, freezing, sugaring, pickling, canning and bottling. Above all, drying is especially suited for developing countries with poorly established low-temperature and thermal processing facilities. It is an extremely effective method to reduce postharvest losses and counterbalance the shortages in supply. Drying is a method of dehydration of food products which means reducing the moisture content from the food to improve its shelf life by preventing bacterial growth. It is used in small agro farms to dry crops, agricultural products and foodstuff such as fruits, vegetables, aromatic herbs, wood etc. thus significantly contributing to the economy of small agricultural communities and farms.

  2. INDIAN SCENARIO

India is blessed with abundant solar energy. Meanwhile a large amount of food and grains are spoiled due to the lack of proper storage systems. Drying of food is an effective means of extending shelf life, improving quality and minimizing losses during storage since most of the water is taken out of the product during this process. Various drying techniques are employed to dry different food products such as open sun drying, industrial drying based on fossil fuel and solar-based drying system. Open Sun drying is economical, but the dried product quality is poor due to contamination, loss of vitamins, nutrients, and color changes. Industrial drying offers quality drying, whereas its high cost limits its use. In many rural locations and villages of countries, grid- connected electricity and supplies of other non-renewable sources of energy are either unavailable, unreliable or, for many farmers, too expensive. Sometimes, they employ motorized fans and/or electrical heating, leads to large initial and running costs barrier that they are rarely adopted by small scale farmers.

India is located in the equatorial sun belt of the earth, thereby receiving abundant radiant energy from the sun.

Most parts of India receive 47 kWh of solar radiation per square metre per day with 250300 sunny days in a year. As per MNRE report, most of the energy requirement for drying is fulfilled by fossil fuels such as coal and natural gas. India spends annually around 160 million tonnes of coal, 90 million tonnes of petroleum products and 240 million tonnes of other traditional conventional energy to meet its industrial, agro and domestic requirements. The use of solar energy in drying is becoming an important and viable alternative since it decreases consumption of conventional energy, and improves production efficiency. There is a significant potential for solar dryer in the agricultural sector also to dry agricultural products such as food grains, vegetables, fruits and medicinal plants, thereby eliminating dependency on open sun drying and industrial drying, while saving huge quantities of fossil fuels. It also has a high potential of diffusion in the domestic and industrial sector. It has advantages like low running cost and superior quality of food. Solar dryer is a low-cost device, operated by solar energy. A solar dryer without heat storage provides air with large variations in temperature to the dryer, and drying of food is not possible during partial clouds and late evening hours.

2.1 EARLY WORK ON SOLAR DRYING IN INDIA

  1. In NPL, New Delhi in 1954 solar heated air was used for drying of coal fines.

  2. In NPL, New Delhi in 1955, plane glass mirror concentrators with overall dimensions of 1.83m x 0.91 m were used for making jaggery from sugar cane and palm juice.

  3. Khadi & Village Industries Commission (KVIC), Ahmedabad in 1968, using similar mirrors erected a pilot plant which dehydrates palm nira and turns it into gur or syrup.

  4. Forest Research Institute (FRI), Dehradun, Developed a

    7.1 cu.m, capacity timber seasoning kiln in 1972.

  5. Central Arid Zone Research Institute (CAZRI), Jodhpur developed a solar cabinet dryer n 1972 and tested it for several years for drying fruits and vegetables.

  6. Annamalai University, in the year 1978 developed one ton per day solar paddy dryer.

  7. National Industrial Development Corporation (NIDC) of India developed several solar grain dryer in 1980 and put to use in few cities in India.

    2.2 Sun drying process Vs solar drying process

    Open sun drying is the cheapest method of drying food Sun drying (laying the crops under direct sunlight) is economical, but the product obtained by it is of lower quality due to contamination by dust, insects, birds, pets and spoilage due to sudden and unpredicted rain. Few negative impacts of natural Drying are loss of vitamins & nutrients, Slow process, poor product quality due to micro-organisms growth, Spoilage of product due to fungal growth, Requires large area, dependency on natural weather control over drying condition, UV radiation ,Ununiform drying .

    Solar dryers are specialized devices that control the drying process and protect agricultural products from damage by insect pests, dust and rain. Solar dryers are available in a range of size and design such as tunnel dryers, hybrid dryers, horizontal- and vertical-type dryers, multi-pass dryers and active and passive dryers Based on the heating modes and solar heat utilization, solar dryers are classified forced air circulation or active solar dryers and natural air circulation or passive solar dryers.

    1. PREFACE ABOUT DRYING TECHNIQUES Drying is one of the most important means for the

      preservation of many kinds of agricultural products. It means moisture removal from the product and helpful in preserving food product for long time and prevent product from contamination.

      Open sun drying, where the product is exposed directly to the sun allowing the solar radiation to be absorbed by the material, is one of the oldest techniques employed in agriculture. Solar energy is one of the promising heat sources for meeting energy demand without putting adverse impact of environment. Solar is one of the pillars for clean and environment friendly energy. Drying of agricultural food products is one of the most attractive and cost-effective applications of solar Energy. The solar dryer is less reliable due to the intermittent nature of solar energy. It has the interruption during the night time, cloudy days and rainy weather. In many countries, agricultural products are dried under the open sun. However, open drying degrades the quality of the dried products due to interference from external impurities and uneven drying rates. Numerous types of solar dryers have been designed and developed in various parts of the world, yielding varying degrees of technical performance.

      The reliability issue of solar dryer can be improved by the provision of auxiliary heating source powered by biomass energy. Since, biomass is the most widely used due to its availability and cost effectiveness in rural areas. This paper deals with the integration techniques of solar and biomass in mixed mode configuration for crop dryer to enhance the performance of the dryer and dried products. List of some advantages of solar drying are reducing the field losses of the products, permits better planning of harvesting season, reduces spoilage in storage drastically, permits the farmer to sell his product at better price , Enhanced product Quality and easy transportation with dried product

    2. SOLAR DRYER

      The objective of a solar dryer is to provide ample amount of heat i.e. more than ambient heat under given humidity. It increases the vapor pressure of the moisture confined within the product and decreases the relative humidity of the drying air so that the moisture carrying capacity of the air can be increased. Air is drawn through the dryer by natural convection or sometimes by a fan. It is heated as it passes through the collector and then partially cooled as it catches moisture from the material. The material is heated both by the air and sometimes directly by the sun. Warm air can hold more moisture than cold air to maintain relative humidity, so the amount of moisture removed

      S.No

      Physical structure

      Dimensions

      Heat Collector

      1

      Outer dimension

      24*48*6 Inches

      2

      Width

      24 Inches

      3

      Length

      48 Inches

      4

      Height from Ground

      12 Inches

      5

      Thickness

      6 Inches

      6

      Air Hole diameter

      3.5 Inches

      7

      Heat Absorber pipes

      7 Nos

      8

      Heat Absorber pipe length

      48 Inches

      9

      Heat collector distance from surface

      2.5 Inches

      10

      Air hole distance from end point

      0.5 Inches

      11

      Inclination angle

      45 Deg

      12

      Cover

      double walled UV stabilized polycarbonate material

      13

      Collector insulation

      0.3 Inches

      14

      Absorber thickness

      1 Inch

      15

      cover thickness

      0.5 Inch

      I6

      Distance between absorber and glass cover

      3.5 Inches

      Dryer Unit

      1

      No of trays

      4

      2

      Trays

      Aluminum and Iron

      3

      Max temperature Limit

      65 Deg

      4

      Height from the ground

      5 Inches

      5

      Height of the dryer

      24 Inches

      6

      Width

      26 Inches

      7

      Distance between trays

      5 Inches

      8

      Thermostat model

      EG01/2

      9

      Display SELEC

      TC 513

      Fan

      1

      Flow rate

      300m3/hr

      2

      Voltage

      12 V DC

      3

      Power

      12 W

      Biomass burner

      1

      Height from the ground

      6 Inches

      2

      Height

      18 Inches

      3

      Width

      18 Inches

      4

      Chimney Height

      3 Inches

      5

      Fuel door dimensions

      10*10 inches

      separate solar collector (air heater) and the heated air then passes through the grain bed, while in the mixed mode type of dryer, the heated air from a separate solar collector is passed through a grain bed, and at the same time, the drying cabinet absorbs solar energy directly through the transparent walls or the roof.

      The objective of this paper is to design a mixed-mode solar dryer in which the grains are dried simultaneously by both direct radiation through the transparent walls and roof of the cabinet and by the heated air from the solar collector. The materials used for the construction of the mixed-mode solar dryer are cheap and easily obtainable in the local market.

      Fig 1.Basic block diagram of solar crop dryer

      6. SPECIFICATION OF THE DRYER

      The design concept of the solar grain dryer is to collect the solar energy through asolar collector and use it to heat up a mass of air and then pass it through a drying chamber by natural convection. Hence the heat supply to the grain is by indirect absorption of solar radiation. The solar crop dryer was developed, constructed and assembled as shown in Figure 1. The dryer consist of the following components: Heat collector, drying chamber, air vents and biomass burner.

      depends on the temperature to which it is heated in the collector as well as the absolute humidity of the air when it entered the collector. The moisture absorption capacity of air is affected by its initial humidity and by the temperature to which it is subsequently heated. The drying process depends on the Size and shape, moisture content, Thickness of the layer, Turning intervals, Temperature of grain, Temperature, humidity of air in contact with the grain, Mechanical or chemical pre-treatment, velocity of air in contact with the grain. In the developing countries and in rural areas the traditional open-air drying methods should be substituted by the more effective and more economic solar drying technologies. This study is therefore devoted to the development, design, construction and performance of a passive solar grain dryer for small scale farmers in a tropical environment.

    3. HARDWARE DESCRIPTION

Solar drying is classified into direct and indirect solar dryer. In direct solar dryers, the air heater contains the grains and solar energy which passes through a transparent cover and is absorbed by the grains. Essentially, the heat required for drying is provided by radiation to the upper layers and subsequent conduction into the grain bed. However, in indirect dryers, solar energy is collected in a

Fig 2. Working of Solar & biomass integrated crop dryer

  1. SOLAR HEAT ABSORBER AND COLLECTOR Sunlight passes through the glazing and strikes the absorber plate, which heats up, changing solar energy into heat energy. The heat is passing through pipes attached to the absorber plate. Absorber plates are commonly painted with "selective coatings," which absorb and retain heat better than ordinary black paint. Absorber plates are usually made of metaltypically copper or aluminumbecause the metal is a good heat conductor. The heat collector was constructed using 2 mm thick aluminum plate, painted black, is mounted in an outer box built. The space between the inner box and outer box is filled with foam material of about 35 mm thickness and thermal conductivity of 0.05 Wm1 K1 .The top of the collector is made of one layer of

    0.5 Inch thickness of double walled UV stabilized polycarbonate sheet material with dimension of 24 Inches*48 Inches*6 Inches, which is more efficient than other materials. The advantages of PC sheets are High impact strength, Easy to fabricate, good electrical insulation properties, excellent toughness, Very good heat resistance, easily replaceable, easily bent and cannot be easily broken and more flexible and 200 times stronger than glass. The heat absorber is constructed of 12 Inches distance from the ground. It has 7 Nos of heat absorber pipes inside the collector box with length of 48 Inches and diameter of 1 Inch. There are two air-vents generally referred to as inlet air vent and outlet air vent. The air intake into the collector is through a 3.5 Inches slot made through the collector casing between the absorber plate and the bottom of the collector, which forms the airflow duct. The flat-plate solar collector is always tilted and oriented in such a way that it receives maximum solar radiation during the desired season. The best stationary orientation is due south in the northern hemisphere and due north in southern hemisphere. Therefore, heat collector in this work is oriented facing south and tilted at 45o to the horizontal. This inclination is also to allow easy run off of water and enhance air circulation.

  2. The Drying chamber

    The hot air from the heat absorber and biomass burner is acting as the heat source to the drying chamber. The drying chamber was built from aluminum material. An outlet vent was provided toward the upper end at the back of the cabinet to facilitate and control the convection flow of air through the dryer. Access door to the drying chamber for loading and off loading of the grains is positioned at the front side of the cabinet. This consists of four removable trays made of

    13 mm aluminum, which placed with the distance of 5 Inches each other. The roof and the walls of the cabinet are covered with polycarbonate sheets of 4 mm thick, which provides additional heating. The outlet air vent is the chimney which is situated on the top of the drying chamber. It is made of metal tube and ridged roofing sheet painted black which serve the exhaust of flue gas. It is circular in shape measuring 3 Inches high and of diameter of 1 Inche.

  3. Drying Trays

    4 No of trays each measuring 24 Inches*28 Inches are placed inside the drying chamber and were constructed from a double layer of fine wire mesh with a fairly open structure to allow drying air to pass through the items. The distance between each tray unit is 5 Inches.

    Fig 3. Solar & biomass integrated crop dryer layout

    Fig 2 & 3 shows the main components of the dryer, consisting of the solar collector (air heater), the drying cabinet and drying trays.

  4. Biomass Burner

    India being a large agrarian economy, biomass wood, agricultural residues, animal dung, etc. is available in enormous quantities and biomass contributes over a third of primary energy source in India. And, hence, over 40% of India's total energy requirement is met through biomass burning. Biomass-based dryer systems for rural applications could effectively make up for the absence of grid electricity supply in many remote areas and village electrification. Bio- mass includes all water- and land-based organisms, vegetation, and trees, and all dead and waste biomass such as municipal solid waste (MSW), bio solids (sewage) and animal wastes (manures)and residues, forestry and agricultural residues, and certain types of industrial wastes. Biomass has been a major energy source, prior to the discovery of fossil fuels like coal and Petroleum. Bio mass burner is constructed using aluminum plates. The dimensions of the burner are 18*18*18 Inches. The biomass products are feed into the burner through the opening window. The hot flue gas is collected from the burner and fed to the drying chamber.

  5. HARDWARE SETUP

    DRYING CHAMBER

    DRYING TRAYS

    Fig 4 Drying chamber layout

    Fig 5 Heat collector layout

    DRYING CHAMBER

    DRYING TRAYS

    BIOMASS BURNER

    Fig 6 Solar crop dryer integrated with biomass burner

    SOLAR HEAT COLLETOR

    CHIMNEY OUTLET

    BIOMASS BURNER

    DRYING CHAMBER

    HOT AIR

    Fig 7 Solar crop dryer integrated with biomass burner

  6. SPECIFIC UNIQUENESS OF THE PRODUCT

    • Its a hybrid system, since heat from solar and biomass is utilized for heating, which improves it heating efficiency.

    • The dryer unit is covered with polycarbonate sheet, so it retains the heat for a long time.

    • Bio mass burning furnace will supply heat during the night time, So the system gives drying heat 24/7.

    • It restricts the growth of microorganisms in the products.

    • Its operated from solar and biomass, so no need for Electrical supply. Best suitable in remote places also.

    • Affordable price.

    • Save lot of time.

    • Occupying less area, since physical structure is small.

    • It improves quality of the dried product, since uniform spread of heat through circulating fan.

    • Thermostat setup available for temperature monitor and control.

    • Only small amount of pollution due to biomass furnace, its also filtered by filters connected in chimney unit.

    • Wood and other wastes are usd as fuel in biomass furnace.

    POTENTIAL APPLICATIONS

    • Small scale and medium scale drying Industries

    • Useful setup for magalir suya uthavi kuzhu food products

    • Food processing Industries

    • Dairy industries for production of milk powder, casein etc.

    • Seasoning of wood and timber.

    • Textile industries for drying of textile materials. Agricultural crop drying

    • Food processing industries for dehydration of fruits and vegetables

    • Fish and meat drying

  7. RESULTS

    The solar dryer was placed over the roof top of a building based on the design. Axial flow fan was fixed at the top of the drying chamber and tested. The experiments were conducted in the month of March, from daily 9 am to 5 pm. The solar radiation was measured using pyranometer. The K-type thermocouples were used for the measurement of temperature in the collector assembly. The temperature was measured for each hour from 9 am to 5 pm at three points, namely entry, middle and exit of the glass cover, absorber plate and bottom insulation as it can be seen in Fig. 4. The temperature of the air in the drying chamber and the atmosphere were measured by the thermometer. A vane- type anemometer is used to measure the air velocity.

    Initial moisture content

    80 to 90%

    Final moisture content

    15 to 20%

    Max temperature

    70 o C

    Storage

    Sealed bags

    Required drying time

    Required drying temperature

    45 o C

    1. days

    2. hours /day

    Results obtained: Grapes

    Initial moisture content

    40 %

    Final moisture content

    9 %

    Max temperature

    70 o C

    Storage

    Containers

    Required drying time

    Required drying temperature

    45 o C

    1. days

    2. hours /day

    Groundnuts

    Initial moisture content

    80 to 90%

    Final moisture content

    15 to 20%

    Max temperature

    70 o C

    Storage

    Sealed bags

    Required drying time

    Required drying temperature

    45 o C

    1. days

    2. hours /day

    Green chilies

    Dried bitterguard

    Initial moisture content

    60 to 70%

    Final moisture content

    15 %

    Max temperature

    65 o C

    Storage

    Sealed bags

    Required drying time

    2days

    4 hours /day

    Required drying temperature

    45 o C

    Tulsi and medicinal leafs

    Dried mint leaves

    Fig.8 Dried Products samples

  8. CONCLUSION

The use of solar drying for food and agricultural products has a large potential from the technical and energy-saving point of view. The partial availability of solar energy in the day and the transient nature of solar energy are compensated by integration with biomass resources. With the hybrid proposed technologies, the performance of the solar thermal systems is enhanced by bringing the systems to operate continuously over the 24 hours per day with higher efficiency.

The conclusions that could be drawn are:

  1. The solar drying has been improved by integration with thermal back up such as biomass burner

  2. A solar and biomass integrated crop dryer was developed and its performance evaluated. With the data available, any convenient size can be produced at community level cooperative use and for any prospective investor.

  3. The mean drying rate of the dryer was 0.8 kg/day per every 10 kg of Crops whereas sun-drying rate was 0.3125 kg/day comparatively.

  4. Savings in time was achieved by using the solar grain dryer as against traditional sun-drying method

The results are encouraging and it is recommended to further investigate various integrations and back up technologies to enhance the performance of the solar thermal systems. Also the Future scope is to develop a crop dryer system with heat storage materials such as rock, water, sand and granite, metal scrap, pure paraffin wax, a mixture of aluminum power and paraffin wax.

REFERENCES

  1. Rosa Rolle S. (2006) Postharvest management of fruit and vegetables in the Asia-Pacific region. Asian Productivity Organization, Tokyo,

    Japan

  2. Karathanos VT, Belessiotis VG (1997). Sun and artificial air drying kinetics of some agricultural products. Journal of Food Engr.,31(1): 35-46.

  3. Leon MA, Kumar S, Bhattacharya SC (2002). A comprehensive procedure for performance evaluation of solar food dryers. Renewable and Sustainable Energy Reviews. 6: 367-393

  4. Aboul-Enein S, El-Sebaii AA, Ramadan MRI, El-Gohary HG (2000).

    Parametric study of a solar air heater with and without thermal

  5. Diemuodeke E. OGHENERUONA, Momoh O.L. YUSUF.Design and Fabrication of a Direct Natural Convection Solar Dryer for Tapioca;Department of Mechanical Engineering, University of Port Harcourt Department of Civil and Environmental Engineering, University of Port Harcourt, P.M.B. 5323, Choba, Rivers State, Nigeria; Leonardo Electronic Journal of Practices and Technologies ISSN 1583- 1078; Issue 18, January-June 2011 p. 95- 104.

  6. B Gutti, S. Kiman and A. Murtala, Solar Dryer- An effective tool for agricultural products preservation, Journal of Applied technology in Environmental Sanitation, 2(1), 2012, 31-38. [2].

  7. F. hang, M. Zhang, A. Mujumdar, Drying characteristics and quality of restructured wild cabbage chips processed using different drying methods. Drying Technology, 29(6),2011, 682-688.

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