[Solar Powered Refrigeration Unit]

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ACKNOWLEDGEMENT

I would take this opportunity to thank my research supervisor, family and friends for their support and guidance without which this research would not have been possible.

DECLARATION

I, [type your full first names and surname here], declare that the contents of this dissertation/thesis represent my own unaided work, and that the dissertation/thesis has not previously been submitted for academic examination towards any qualification. Furthermore, it represents my own opinions and not necessarily those of the University.

Signed __________________ Date _________________

EXECUTIVE SUMMARY

A small ammonia-water intermittent absorption refrigerator with a 1.44 m2 flat plate solar collector has been tested as a first step towards the development of a village ice maker. No oil or electricity is used. Regeneration takes place during the day and refrigeration at night. Rapid absorption is obtained by means of a new feature, first proposed by Swartman, in which the heat of absorption is dissipated from the flat plate. In the generator 15 kg of solution containing 46% ammonia in water are used. On a clear day the solution temperature rises from 30oC, to 88oC and 0.9 kg of pure ammonia is condensed at 32oC. During refrigeration the temperature of the ammonia drops to -7oC. The estimated overall solar coefficient of performance (cooling effect divided by solar heat absorbed) is 0.09, which though small is comparable with previously published work. Developments in the design are discussed.

TABLE OF CONTENTS

ACKNOWLEDGEMENTII

DECLARATIONIII

EXECUTIVE SUMMARYIV

CHAPTER 1: INTRODUCTION1

The Basis for Considering Solar Energy1

Objectives of the Study1

Possibilities for Research and Development2

The Rationale for Selecting Solar Refrigeration4

CHAPTER II: SOLAR REFRIGERATION7

Indices of Performance7

Operation of the Intermittent Ammonia-Water System8

Analysis of the Ideal Cycle8

Rigorous Analysis of the Ammonia-Water Cycle11

Historical Development13

CHAPTER III: DESIGN OF THE EXPERIMENTAL UNIT20

Choice of Configuration20

Operation of the System21

Concentration of Aqua-Ammonia23

Regeneration Phase of the Cycle23

Refrigeration Phase of the Cycle24

Collector-Generator Specifications25

The Volume of the Generator27

The Size of the Receiver for Ammonia29

Heat of Generation29

Heat of Condensation30

Further Details of the Design30

CHAPTER IV: EXPERIMENTAL TESTS33

Relationship between Plate Temperature and Solution Temperature33

Experimental Results33

Amount of Ammonia Distilled41

Cooling Ratio43

Heat Absorbed by Solution during Regeneration44

Solar Coefficient of Performance44

Discussion46

SECTION V: CONCLUSIONS AND PLANS FOR CONTINUING RESEARCH47

Conclusions47

Economic Considerations47

Modifications48

The Development of a Village Ice-Maker48

Alternatives50

REFERENCES52

APPENDIX A54

Charging54

Equipment54

Procedure54

APPENDIX B58

Estimation of Incident Solar Radiation58

CHAPTER 1: INTRODUCTION

The Basis for Considering Solar Energy

There are several important reasons for considering solar energy as an energy resource to meet the needs of developing countries. First, most the countries called developing are in or adjacent to the tropics and have good solar radiation available. Secondly, energy is a critical need of these countries but they do not have widely distributed readily available supplies of conventional energy resources. Thirdly, most of the developing countries are characterized by arid climates, dispersed and inaccessible populations and a lack of investment capital and are thus faced with practically insuperable obstacles to the provision of energy by conventional means, for example, by electrification. In contrast to this solar energy is readily available and is already distributed to the potential users. Fourthly, because of the diffuse nature of solar energy the developments all over the world have been in smaller units which fit well into the pattern ...