Design And Construction Of A Solar Dryer

ABSTRACT

The solar drying system utilizes solar energy to heat up air and to dry any food substance loaded, which is not only beneficial in that it reduces wastage of agricultural produce and helps in preservation of agricultural produce, but it also makes transportation of such dried produce easy and promotes the health and welfare of the people. This paper presents the design and construction of a domestic passive solar food dryer. The dryer is composed of solar collector (air heater) and a solar drying chamber containing rack of four cheese cloth (net) trays both being integrated together. The air allowed in through air inlet is heated up in the solar collector and channeled through the drying chamber where it is utilized in drying (removing the moisture content from the food substance or agricultural produce loaded). The design was based on the geographical location which is Abeokuta and meteorological data were obtained for proper design specification. Locally available materials were used for the construction, chiefly comprising of wood (gmelina), polyurethane glass, mild steel metal sheet and net cloth for the trays.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRACT

CHAPTER ONE

1.0      INTRODUCTION

1.1      BACKGROUND OF THE PROJECT

• AIM OF THE PROJECT
• OBJECTIVE OF THE PROJECT
• SIGNIFICANCE OF THE PROJECT
• SCOPE OF THE PROJECT
• PROBLEM OF THE PROJECT
• APPLICATION OF THE PROJECT
• ADVANTAGES OF SOLAR DRYER
• LIMITATION OF THE PROJECT

CHAPTER TWO

LITERATURE REVIEW

• INTRODUCTION
• OVERVIEW OF THE STUDY
• REVIEW OF SOLAR ENERGY
• REVIEW OF GLOBAL RADIATION
• CAPTURING SOLAR ENERGY
• IMPORTANCE OF SOLAR DRIED FOOD
• TYPES OF SOLAR DRYER
• REVIEW OF THE RELATED STUDIES
• EARLY WORK ON SOLAR DRYING IN INDIA

CHAPTER THREE

3.0     CONSTRUCTION METHODOLOGY

3.1      INTRODUCTION

3.2     GENERAL DESCRIPTION OF THE SOLAR DRYER

3.3      DESIGN DIAGRAM

3.4      MATERIALS USED

3.5     DESIGN CONSIDERATION

3.6     SYSTEM CONSTRUCTION

CHAPTER FOUR

• CONSTRUCTION PROCEDURE
• ASSEMBLING OF SECTIONS
• TESTING OF SYSTEM OPERATION
• PROBLEM ENCOUNTERED
• DESIGN CALCULATIONS

CHAPTER FIVE

• CONCLUSION
• REFERENCES

CHAPTER ONE

1.1                                                        INTRODUCTION

Drying is an excellent way to preserve food and solar food dryers are appropriate food preservation technology for sustainable development [1]. Drying was probably the first ever food preserving method used by man, even before cooking. It involves the removal of moisture from agricultural produce so as to provide a product that can be safely stored for longer period of time.

“Sun drying” is the earliest method of drying farm produce ever known to man and it involves simply laying the agricultural products in the sun on mats, roofs or drying floors. This has several disadvantages since the farm produce are laid in the open sky and there is greater risk of spoilage due to adverse climatic conditions like rain, wind, moist and dust, loss of produce to birds, insects and rodents (pests); totally dependent on good weather and very slow drying rate with danger of mould growth thereby causing deterioration and decomposition of the produce. The process also requires large area of land, takes time and highly labour intensive [2].

With cultural and industrial development, artificial mechanical drying came into practice, but this process is highly energy intensive and expensive which ultimately increases product cost [2]. Recently, efforts to improve “sun drying” have led to “solar drying”.

In solar drying, solar dryers are specialized devices that control the drying process and protect agricultural produce from damage by insect pests, dust and rain. In comparison to natural “sun drying”, solar dryers generate higher temperatures, lower relative humidity, lower product moisture content and reduced spoilage during the drying process. In addition, it takes up less space, takes less time and relatively inexpensive compared to artificial mechanical drying method. Thus, solar drying is a better alternative solution to all the drawbacks of natural drying and artificial mechanical drying [2].

The solar dryer can be seen as one of the solutions to the world’s food and energy crises. With drying, most agricultural produce can be preserved and this can be achieved more efficiently through the use of solar dryers.

• BACKGROUND OF THE PROJECT

Drying is one of the oldest methods using solar energy where the product such as vegetables, fruits, fish, and meat are to be dried by exposing directly to the sun. It is a simple process of removing the moisture contents from a natural or industrial product in order to reach the standard specification. This method is economical on a large scale drying because of cheaper operating costs compared to the drying machine.

 

However, this method has many disadvantages such as spoilt products due to rain, wind, dust, insect infestation, animal attack and fungi. Because of that, the solar dryer technology will become an alternative method which can process the products in clean, safe, hygienic and produce better quality and more nutritious foods. In general, this solar dryer has saved energy, labor intensive, time, less area for spreading the product to dry, makes the process more efficient and protects the environment.

 

Solar dryer can be classified by three types that is direct, indirect and mixed mode which it is according to the passive mode of drying, whether the product to be dried is exposed or not. The active solar dryer, auxiliary energy is necessary to operate the system. However, in the mixed mode solar dryer, it consists of both radiation with conduction of heat through the transparent cover and the convection of the heat from the solar air heater.

Food materials and crops are very sensitive to the drying conditions. Very short duration with high speed drying would caused a quality of dried product will be reduced due to over or under dry. Thus the selection of drying temperature is o ne of the most important thing to ensure the color, texture, flavor and value of the product will not degrade (Devahast, undated). Thereby, a new design of high efficiency solar dryer for small scale food was designed and tested for several products such as fruits and fish. Drying result obtained were compared with the result of the naturally direct sun-dried product.

1.2                                                   AIM OF THE PROJECT

The objective of this study is to develop a passive 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.

1.3                                             OBJECTIVE OF THE PROJECT

There are two main objectives to achieve in this research which are:

1. To study a charateristics and performance of the solar dryer
2. To develop a solar dryer system for food

1.4                                         SIGNIFICANCE OF THE PROJECT

A solar dryer is another application of solar energy, used immensely in the food and agriculture industry. Though sun is still used as the direct source for drying food items and clothes in certain parts of the world. An indirect source of solar power can also be used for the same purpose in the form of a solar dryer.

1.5                                                 SCOPE OF THE PROJECT

the solar dryer is design and constructed with the consideration of overcoming the limitations of direct and indirect type of solar dryer. So therefore, this work will be based on the importance of a solar dryer which is reliable and economically. The objectives of the work is to design and construct a solar dryer using locally available materials and to evaluate the performance of the solar dryer.

1.6                                              PROBLEM OF THE PROJECT

The main problem of drying directly under the sun is contamination – dirt, animals, insects etc. Also there is a fear of sudden change in weather conditions like wind or rain.

1.7                                          APPLICATION OF THE PROJECT

Solar dryers are a very useful device for:

1. Agricultural crop drying
2. Food processing industries for dehydration of fruits and vegetables.

• Fish and meat drying.

1. Dairy industries for production of milk powder.
2. Seasoning of wood and timber.
3. Textile industries for drying of textile materials, etc.

Thus, the solar dryer is one of the many ways of making use of solar energy efficiently in meeting man’s demand for energy and food supply.

1.8                                         ADVANTAGES OF SOLAR DRYER

1. The higher temperature, movement of the air and lower humidity increases the rate of drying.
2. Food is enclosed in the dryer and therefore protected from dust, insects, birds and animals.

• The higher temperature deters insects and the faster drying rate reduces the risk of spoilage by microorganisms.

1. The higher drying rate also gives a higher throughput of food and a smaller drying area (approximately one third).
2. The dryers are waterproof, therefore, the food does not need to be moved during raining.
3. Dryer can be constructed from locally available materials and are relatively low cost.

1.9                                           LIMITATION OF THE PROJECT

1. Can be only used during day time when adequate amount of solar energy is present.
2. Lack of skilled personnel for operation and maintenance.

• Less efficiency as compared with modern type of dryers.

1. A backup heating system is necessary for products require continuous drying