DESIGN AND FABRICATION OF A SOLAR GRAIN DRYER
Drying crops or grains by solar energy is of great economic importance the world over, especially in Nigeria where most of the crops and grain harvests are lost to fungal and microbial attacks. Proper drying could easily prevent these wastages, which enhances storage of crops and grains over long periods. India is blessed with abundant solar energy all the year round. Drying is one of the important and most energy consuming processes in the food- processing, chemical, printing, fabric dying industries, etc. In farmer level drying is being done on open yards without any good hygienic conditions. Generally thermal energy, maintained between 45 0C to 25 0 C depending on the products and production methods. A conventional fuel like electricity, firewood, diesel, furnace oil, kerosene, etc is producing that energy. The objective of this project is to modify design of a forced convection indirect solar dryer and its performance test on Grapes. The system consists of an air heating section. The solar dryer consists of different components such as solar panel, battery, heating element and blower. The blower is used to passing the hot air to the required place, so that the moisture contents in the place was removed. It offers a better control over drying and the product obtained is of better quality than sun drying. Solar Dryer Can be operated at higher temperature, recommended for deep layer drying.
TABLE OF CONTENTS
1.1 BACKGROUND OF THE PROJECT
1.2 PROBLEM STATEMENT
1.3 SCOPE OF THE PROJECT
1.4 OBJECTIVE OF THE PROJECT
1.5 ADVANTAGES OF THE PROJECT
1.6 LIMITATION OF THE PROJECT
2.1 REVIEW OF THE STUDY
2.2 DRYING OF GRAINS
2.3 PROCESSES USED IN THE FABRICATION
3.0 CONSTRUCTION METHODOLOGY
3.1 PARTS OF THE SYSTEM
3.2 MATERIALS USED
3.3 DESIGN CONSIDERATION
3.4 DESIGN CALCULATION NOMENCLATURE
3.5 COST ESTIMATION
4.0 TEST AND RESULT ANALYSIS
4.1 CONSTRUCTION PROCEDURE AND TESTING
4.2 ASSEMBLING OF SECTIONS
4.3 ECONOMIC OF THE PROJECT
4.4 PROJECT VIABILITY
4.7 PROJECT EVALUATION
4.8 RESULT AND DISCUSSION
5.2 FUTURE SCOPE
In the majority of countries, agriculture represents the biggest part of the economy. 80-90% of the working population is employed in agriculture. Despite these large numbers, national food production still does not meet the needs of the population. The lack of appropriate preservation and storage systems caused considerable losses, thus reducing the food supply significantly. The dent in food production caused by crop-failures as well as significant seasonal fluctuations in availability can be ironed out by food conservation, e.g., by drying. Sun drying of crops is the most widespread method of food preservation in a lot of countries due solar irradiance being very high for the most of the year. There are some drawbacks relating to the traditional method of drying, i.e., spreading the crop in thin layers on mats, trays or paved grounds and exposing the product to the sun and wind. These include poorer quality of food caused by contamination by dust, insect attack, enzymatic reactions and infection by micro-organisms. Also this system is labour and time intensive, as crops have to be covered at night and during bad weather, and the crops continually have to be protected from attack by domestic Animals. Non-uniform and insufficient drying also leads to deterioration of the crop during storage. Serious drying problems occur especially in humid tropical regions where some crops have to be dried during the rainy season. Traditional sun drying of sweet pepper and coffee. In order to ensure continuous food supply to the growing population and to enable the farmers to produce high quality marketable products, efficient and at the same time affordable drying methods are necessary. Studies have shown that even small and most simple oil-fired batch dryers are not applicable for the most farmers, due to lack of capital and insufficient supply of energy for the operation of the dryers.
The high temperature dryers used in industrialized countries are found to be economically viable in developing countries only on large plantations or big commercial establishments. Therefore the introduction of low cost and locally manufactured solar dryers offers a promising alternative to reduce the tremendous post harvest losses. The opportunity to produce high quality marketable products seems to be a chance to improve the economic situation of the farmers. However, taking into account the low income of the rural population in developing countries, the relatively high initial investment for solar dryers still remains a barrier to a wide application. 1.2 Solar radiation- The Energy Source For Solar Dry-ing The sun is the central energy producer of our solar system. It has the form of a ball and nuclear fusion take place continuously in its centre. A small fraction of the energy produced in the sun hits the earth and makes life possible on our planet. Solar radiation drives all natural cycles and processes such as rain, wind, photosynthesis, ocean currents and several other which are important for life. The whole world energy need has been based from the very beginning on solar energy. All fossil fuels (oil, gas, coal) are converted solar energy. The earth's atmosphere is being changed at an unprecedented rate by pollutants resulting from wasteful fossil fuel use. These changes represent a major threat to international security and are already having harmful consequences over many parts of the globe. It is imperative to act now. So it’s the time that we have to make some alternatives that will be helpful for overcoming the shortage and need of today. That is why there are alternatives sources that we are using like solar energy, wind energy, geothermal energy etc.
1.1 BACKGROUND OF THE STUDY
Energy is the most important need of today’s society and economy. Our work, leisure, and our economic, social and physical welfare all depend on the sufficient, uninterrupted supply of energy. The energy demand continues to grow, year after year. Drying is one of the methods used to preserve food products for longer periods. The heat from the sun coupled with the wind has been used to dry food for preservation for several thousand years.
Sun drying is still the most common method used to preserve agricultural products in most tropical and subtropical countries. However, being unprotected from rain, wind-borne dirt and dust, infestation by insects, rodents and other animal, products may be seriously degraded to the extent that sometimes become inedible and the resulted loss of food quality in the dried Products may have adverse economic effects on domestics and international markets.
Solar thermal technology is a technology that is rapidly gaining acceptance as an energy saving measure in agriculture application. It is preferred to other alternative sources of energy such as wind and shale, because it is abundant, inexhaustible, and non-polluting. Solar air heaters are simple devices to heat air by utilizing solar energy and it is employed in many applications requiring low to moderate temperature below 80°C, such as crop drying and space heating.
In ancient times, the sun and wind would have naturally dried foods. Evidence shows that Middle East and oriental cultures actively dried foods as early as 12,000 B.C. in the hot sun. Later cultures left more evidence and each would have methods and materials to reflect their food supplies—fish, wild game, domestic animals, etc.
Vegetables and fruits were also dried from the earliest times. The Romans were particularly fond of any dried fruit they could make. In the Middle Ages purposely built “still houses” were created to dry fruits, vegetables and herbs in areas that did not have enough strong sunlight for drying. A fire was used to create the heat needed to dry foods and in some cases smoking them as well. 
The importance of food drying is likely to increase. The global population is predicted to exceed eight billion by the year 2025 (Cliquet and Thienpont, 1995). Food production must therefore be increased to meet the rising demand but this is unlikely to come from simply growing crops on previously uncultivated land (Dyson, 1996). One strategy to increase food supplies is to minimize crop wastage. In developing countries alone, the minimum estimates of post-harvest losses, including those from poor drying, vary between 10-20% (Pariser, 1987). A 1978 report by the National Research Council of the National Academy of Sciences in Washington, D.C., cited by Salunkhe and Kadam (1998), puts post-harvest losses as high as 30-40% in both industrialized and developing countries.
In addition to foods for human consumption, many other products require Drying. These include organic crops like timber and rubber and inorganic materials like this has focused our attention on energy intensive processes like drying where fossil fuels can often be replaced by renewable and non-polluting sources of energy. Drying paint. All of the above arguments emphasize the importance of drying in people’s lives.
However, according to Mujumdar (1990), "drying is the most energy-consuming industrial process". It requires approximately 2.4 MJ to evaporate one liter of water. To dry one metric ton of most fruits in a conventional dehydrator to the safe moisture, content for long-term storage requires approximately 100 liters of oil. The shortage of energy is an issue in many countries, particularly those in the developing world. Even where conventional energy is plentiful, there is pressure to reduce the amount of fossil fuels used. Concern over global warming is universal and one metric ton of fruit in a conventional dehydrator produces approximately 300 kg of carbon dioxide. Technology the growers dry many crops at the point of production themselves so there is usually adequate land area available for the solar drying system.
Solar energy is an obvious energy source for drying various products, particularly food crops. Many crops are harvested in the summer months and are usually dried at temperatures below 700C - a temperature which can be readily attained by solar .
Some of the problems associated with open-air sun drying can be solved using a solar dryer, which comprises of collector, a drying chamber and sometimes a chimney.
Solar drying may be classified into direct, indirect and mixed-modes. In direct solar dryers the air heater contains the grains and solar energy 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.
In indirect dryers, solar energy is collected in a 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 roof.
1.2 PROBLEM STATEMENT
Solar air dryer is old concept, but in modern world many different parameters are been considered during its manufacturing. The design of solar dyer which gives some advantages as well as disadvantages such as friction losses ,vibration, expansion of acrylic glass due to heat and air flow, friction losses at the reducing cross- sections and leakages of air at small portions which cannot be identified . By considering all factors, we have taken decision to make solar food dryer, which is less costly, more efficient to poor people.
The objective of this study is to develop a mixed-mode solar dryer in which the grains are dried simultaneously by indirect radiation through the transparent walls and roof of the cabinet and by the heated air from the solar collector. The problems of low and medium scale processor could be alleviated, if the solar dryer is designed and constructed with the consideration of overcoming the limitations of indirect type of solar dryer. So therefore, this work will be based on the importance of a mixed mode solar dryer which is reliable and economically, design and construct a mixed mode solar dryer using locally available materials and to evaluate the performance of this solar dryer.
1.3 SCOPE OF WORK
In order to reach the project’s objective, the following scopes are identified:
· Designed a solar dryer according to the information obtained from the literature.
· Acquire materials needed is suitable for fabrication.
· Performance of solar dryer for collector efficiency, drying air temperature and weight loss will be compared with different types of drying method.
1.4 OBJECTIVES OF THE STUDY
The main objectives to achieve in this research that are:
·To study a characteristics and performance of the solar dryer system.
·To select and evaluate the optimum design of solar dryer.
·To test dynamically for its performance and suitability of campus use.
1.5 ADVANTAGES OF THE PROJECT
1. Much less time is required for drying as compared to direct drying because of black body.
2. Protection of the drying products from insects but also from birds, dogs, especially for drying meat and fish.
3. The product is hygienic because microorganisms, insects and flies are killed
4. Protection of rain.
5. Protection of pollution by dust etc.
6. Protection of the wind which can blow away the food
1.6 LIMITATION OF THE PROJECT
1. Not workable at night.
2. Efficiency decreases to a large extent on cloudy days.
3. Overheating may occur if regular attention is not paid.
4. Due to overheating, it can decrease the quality of food.
5. Change in taste and flavour of food may occur if regular monitoring is not done.
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