DESIGN, FABRICATION, AND TESTING OF A VARIABLE-ANGLE CONDENSER (VAC) SINGLE-SLOPE SOLAR STILL

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DESIGN, FABRICATION, AND TESTING OF A VARIABLE-ANGLE CONDENSER (VAC) SINGLE-SLOPE SOLAR STILL

ABSTRACT

This project report details the development of a Variable-Angle Condenser (VAC) mechanism to increase the functionality of solar stills. The estimated performance and the physical dimensions of the solar still were calculated using heat balance equations. The solar-still design process utilized CAD software to increase design efficiency and improve design development time. The test model had a basin area of 0.5m2 and a capacity of 50 litres. The materials for the solar still were selected using material selection processes that considered the required performance, cost, workability, material availability, and other design considerations for the solar still. The researcher fabricated the solar still using the materials selected and tested its performance for six days. The first set of three days of testing had a low volume of water in the solar still, and the second set of three days had a high volume of water. The highest solar irradiance recorded at the test site (Abuja, FCT) between the 16th of July 2021 and 22nd of July 2021 was 877 W/m2. The test results showed that the solar still had a maximum daily yield of 325 ml. The maximum bulk water temperature achieved by the solar still was 55.9℃. The maximum temperature difference between the water and inner glass temperatures was 6.5℃. The highest hourly efficiency observed from the solar still was 89.03%. Findings showed that having a low volume of water in the solar still was not optimal as higher thermal efficiencies were achieved on test days with a high volume of water in the solar still. The functionality of the VAC mechanism for the solar still was tested, and tests showed that the VAC increased the functionality of the solar still. The solar still’s condenser angle could now be changed through a range of degrees (5° to 20°). This added functionality of the VAC results in increased feasibility for the employment of solar stills for real-world use or production as optimum angles could be set based on the solar still deployment location conditions.

CHAPTER ONE

INTRODUCTION

1.1 Background

The human requirement for freshwater is inevitable and unarguably increasing. With the increase in the world population, there is a corresponding increase in the demand for freshwater for domestic and industrial purposes (McDonald, et al., 2011). Although water is abundant on Earth, only 2.5% of natural water is freshwater  (Perlman, 2013). Without adequate freshwater production, a freshwater shortage looms. Pollution of water bodies further compounds freshwater supply issues as industries commonly dump waste into water bodies rendering them impure for use.

Industrial desalination processes such as Reverse Osmosis (RO), Multi-Stage Flash Distillation (MSF), and Multi-Effect Distillation (MED) purify water to keep up with the high demand for freshwater. These processes are beneficial but have high installation, maintenance, and repair costs (Robbins, 2019). They are costly to set up and operate. The high prices make these industrial processes unsuitable for application in rural areas or those with dispersing populations.

Solar distillation is a possible solution to this problem. It is one of the oldest water purification processes known to man (Levey, 1959) (Mechell & Lesikar). Solar distillers (stills) use solar energy to provide the energy required to heat and evaporate water for distillation. Solar distillation is a sustainable freshwater production process. It uses solar energy, which is abundant, at no cost, and is available all over the globe. In contrast, the primary energy source employed for conventional desalination methods is expensive fossil fuels.

1.2 Research Problem

This project aims to increase the functionality of solar stills and increase their feasibility as a solution to freshwater supply in rural areas, e.g., Kubwa, FCT, Nigeria  (Sahara Reporters, 2021), by providing solutions to the following problems.

  1. High Energy Cost of Distillation: Industrial water purification processes provide freshwater for over 300 million people globally. However, these industrial methods face various challenges (Robbins, 2019). The major challenge faced being high energy costs (Peterson, 2017). Reverse Osmosis (RO) is currently the most energyefficient industrial water purification method. However, 30-40% of its energy cost is electricity (Bartholomew, Siefert, & Mauter, 2018).

Other freshwater production methods, such as the transportation of collected freshwater from inland areas, appear to be more attractive due to high energy costs. Lowering the energy cost of water purification by integrating renewable power and other technologies in existing technologies is necessary to make freshwater production more economically feasible.

  1. Negatory Environmental Effects of Current Water Purification Technologies: Using non-renewable energy for water purification progressively causes long-term damage to the environment (Greentumble, 2017). The costs associated with correcting these damages inevitably will make life more difficult for future generations. Freshwater production methods must be able to meet the freshwater demand requirements without causing further environmental damage.

Consideration of sustainable development methods to meet the freshwater needs of the current generation without impacting future generations is vital.

  • Non-Availability of Electricity in Rural Areas: Freshwater production technologies must be workable in areas with little or no electric power supply. The non-availability of electricity makes solar stills a feasible and sustainable freshwater production method in rural areas, such as Kubwa, FCT, Nigeria (Sahara Reporters, 2021).
  1. The Complexity of Solar Still Designs: Conventional solar stills produce lower yields than the current industrial desalination methods for freshwater production. Hence, researchers have employed various modifications to improve the productivity of solar stills. However, these modifications get complex and ultimately have their modification costs outweigh the increase in yield of the still. The high costs of improvement despite their increase in productivity is not suitable for release-to-market.
  2. Functionality Deficit in Solar Stills: Solar stills have a functionality deficit due to their fixed condenser (glass) angles. This deficit makes it hard to optimise the solar still condenser angles as the solar stills’ condenser angles cannot be changed after the solar still’s construction. Increasing the functionality of the solar still will increase its feasibility for employment in rural areas.

1.3 Motivation

The demand for cost-effective freshwater production has led to the research and development of various water purification methods. These water purification methods must be energyefficient, low-cost, environmentally friendly, and minimalistic to be feasible in rural areas. Without meeting these criteria, freshwater production methods will become unsustainable in the long term and will eventually fail.

The single-slope solar still developed in this project meets these criteria. It uses renewable energy for its operation. It is environmentally friendly as the only waste product of the solar still is brine. Its energy costs are net-zero as it does not require electricity for its operation. It needs little maintenance after installation. It has low complexity, is minimalistic, easy-toconstruct, and made from locally sourced materials. The main cost incurred for the solar still use is the fabrication cost.

Solar stills can help in offsetting the freshwater demand in conjunction with existing freshwater production methods by being an alternative source for freshwater production. The VAC mechanism developed in this project for solar stills will increase the feasibility of employing solar stills in rural areas that face freshwater production issues such as Kubwa, FCT, Nigeria (Sahara Reporters, 2021).

1.4 Scope of the Project

This project encompasses the design, fabrication, and testing of a Variable Angle Condenser (VAC) mechanism for single-slope solar stills. The tests conducted on the solar still aimed at measuring the yield and thermal efficiency of the solar still and the functionality of the VAC mechanism.

1.5 Aim and Objectives

This project aims to develop a Variable Angle Condenser (VAC) single-slope solar still and evaluate its performance as a feasible mechanism for increasing the functionality of solar stills.

The specific objectives of the project are to:

  1. Design a Variable Angle Condenser mechanism for single-slope solar stills.
  2. Fabricate a test model of the Variable Angle Condenser solar still.
  • Conduct tests to measure the fabricated single-slope solar still’s performance, including the functionality of the Variable-Angle Condenser.

DESIGN, FABRICATION, AND TESTING OF A VARIABLE-ANGLE CONDENSER (VAC) SINGLE-SLOPE SOLAR STILL

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