School of Mechanical and Industrial Engineering
SOLAR WATER HEATER
Report
Group member
ID.NO.
1. Amir Kelifa
ATR/5911/11
2. Robel Mengesha
ATR/5374/11
3. Samuel Zekarias
ATR/2292/11
4. Sumeyya Nuru
ATR/6784/11
Submitted to: Dr. Kamil D.
ACKNOWLEDGEMENTS
We would like to acknowledge our warmest thanks to our teacher, Dr. Kamil Dino, who made this work
possible. We are grateful to our supervisor, Mr. Mulugeta, whose advice and support have been
invaluable throughout this project. His friendly guidance and expert advice have been invaluable
throughout our workshop period. We also appreciate the contributions of Mr. Sema and all the people in
the workshop to our work.
TABLE OF CONTENT
ACKNOWLEDGEMENTS
TABLE OF CONTENTS
CHAPTER ONE
INTRODUCTION
1.1 Background
1.2 Problem Statement
1.3 Aim and Objectives
CHAPTER TWO
LITERATURE REVIEW
2.1 Solar Energy Potential for Water Heating
2.2 Solar Insolation at System Site
2.3 Operating Principles of a SWH Based on the Thermosyphon Principle
2.4 Types of Solar Water Heating Systems
2.5 Solar collector concepts
2.6 Main Components and Material Selection of a Solar Water Heating System
CHAPTER THREE
DESIGN AND METHODS
3.1 Design and Dimensioning of the SWH
3.2 Construction of the Solar Water System
3.4 Solar Water Heater Performance Evaluation
CHAPTER FOUR
RESULTS AND CONCLUSION
4.1 Results and Discussion
4.2 Conclusion and Recommendation
CHAPTER ONE
INTRODUCTION
1.1 Background
The sun is the world’s largest energy resource and solar energy is a form of renewable energy which is
abundant in our environment. The world's dependence on fossil fuels has caused a lot of harm to the
environment. The combustion of these fuels has raised the levels of greenhouse gases in the atmosphere. This
has caused global warming which has led to climate change, floods, forest fires, rising sea levels and the
melting of glaciers. These are just some consequences of the over-reliance on fossil fuels for our energy
demands. Solar energy provides an alternative and environmentally friendly energy source to the fossil fuels
used for our energy needs. Over the last few decades, solar energy systems have gained more recognition
because they can provide energy at a low long-term cost and minimal environmental damage. Researchers have
developed several techniques for harnessing solar energy; these techniques include applications for space
heating, water heating, electricity generation and many others.
The practice of using the sun for heating water for domestic use can be traced back to several ancient cultures.
Records show the solar water heater (SWH) was first invented in the Roman Empire around 200 B.C.E (Gong
& Sumathy, 2016). The Romans had a simple system, they used the solar heating concept to heat their public
baths to enable a reduction in using coal and the labour required. in the late 18th century (1767) ,the Swiss
natural scientist Horace Bénédict de Saussure builds a “simple solar water heater”, which is made of a wooden
box with a black bottom and covered with glass. The solar collector reaches temperatures of almost 90 °C. De
Saussure found that whenever the insulated box was exposed to solar radiation, the insides reached temperatures
greater than water’s boiling point. He had shown the green-house effect for the first time.
The first commercial solar water heater was patented in 1891; within five years, about 30 percent of the homes
in Pasadena, California, had solar domestic hot water systems installed. Given the comparatively high cost and
inconvenience of using conventional fuels to heat water, many households were eager to invest in these solar
hot water heaters. However, the Climax system was limited in that the heating element doubled as the storage
tank, thus restricting the amount of hot water available. William J. Bailey solved this drawback in 1909 by
developing a system which had the collector and the tank separate from each other. It was the first system in
history that transported the working fluid using the thermosiphon principle. This principle made it possible for
water to circulate without the use of a mechanical pump. William Bailey’s company was called the Day and
Night SWH Company, emphasizing the advantage his solar water heating system had over that of Clarence
Kemp’s. By the 1920s, the discovery of natural gas and oil in southern California led to the emergence of gas
water heaters. This crippled the solar water heating industry. Reductions in electricity cost and the copper
scarcity during the Second World War replaced whatever was left of the solar industry.
In the 1970s, about half a century later, the SWH got global attention again, revitalized by the OPEC embargo
which caused a major oil crisis and a hike in oil prices. Ever since, the solar water heating industry has
expanded all over the world. Growing concerns about the planet’s increasing carbon emissions, global warming
and climate change have flared up interest in the solar water heating industry. As of 2018, the SWH market was
valued at over a billion dollars; the yearly installation is expected to surpass three million units by 2025.
A study in Ethiopia has found that there is very high hot water demand in tanneries and edible oil factories,
medium demand in textile factory and low demand in particle board factory. In all the factories under study the
major hot water consumptions is during the day time which is an advantage for the solar energy application.
Based on the demand study and solar energy data, it was possible to design SWH systems for each factory. The
analysis results on solar water heating indicate that it will cost the factories about 5 USD cents per kWh and the
payback period will be 6 – 7 years. In addition to the advantage of using clean energy, the factories can save
their energy cost by 26-33% by implementing the solar water heating systems. The above results were for
conservative estimates. If an optimized SWH system is considered, the savings can even be higher. It is evident
from this result that the SWH system is economically feasible for the factories.
1.2 Problem Statement
As a result of Ethiopia’s rapid GDP growth over the previous decade, demand for electricity has been steadily
increasing. Despite the country's energy potential, it is struggling to meet the growing electricity demand due to
its population.
The use of solar applications for water heating will lead to better reliability of service for hot water needs and
will have minimal negative impact on the environment. This would reduce the reliance on electric heaters,
which have higher operational costs and depend on fossil fuels as a primary energy source.
1.3 Aim and Objectives
The aim of the project is to build a cost-efficient solar water heater (SWH).
The objectives are:
1. To design a cost-efficient solar water heater .
2. To construct the solar water heater.
3. To carry out the performance evaluation of the constructed solar water heater.
CHAPTER TWO
LITERATURE REVIEW
2.1 Solar Energy Potential for Water Heating
The solar energy that the Earth receives in a day is far greater than the total amount of energy that humans use
up in the same time period. Eighteen days of the incident solar radiation on Earth would give an equivalent
amount of energy when compared to all the planet's reserves of natural gas, coal and oil (Union of concerned
scientists, 2015). Outside the earth’s atmosphere, solar radiation contains about 1,300 watts per square meter. A
third of this gets reflected into space once it reaches the earth’s atmosphere, the rest travels toward the surface
of the earth. On average, over the earth’s surface, every square meter receives about 4.2 kilowatt-hours of solar
energy in a day (Union of concerned scientists, 2015).
Although the solar energy received by the Earth daily is greater than amount used by humans, the intensity of
this solar energy or radiation incident on the Earth’s surface depends on some factors. These factors include the
geographic location and its inherent climate, the weather patterns or season and the time of day. At certain
periods within the year, the Earth is near the sun, this is because the Earth revolves elliptically around the sun.
When the Earth is nearer the sun, its surface receives a higher amount of solar radiation. Earth’s rotation around
the sun is on a tilted axis of 23.5° and this plays a role in determining the incident radiation at a given location.
For the six months within the two equinoxes, the Earth’s tilted rotation brings about longer daytime in the
northern hemisphere. The southern hemisphere on the other hand, has longer days for the six months after the
fall equinox. The southern parts of the United Kingdom and other middle latitudes get higher amounts of
radiation during summer due to the longer days. However, during winter, regions around the middle latitude
receive lower amounts of solar energy because the solar rays are incident at a tilted angle during winter in
middle latitude regions (Office of energy efficiency and renewable energy, 2013). The intensity of the solar
radiation received on the earth’s surface depends on the angle the sun’s rays make with the earth’s surface. This
angle ranges from 0°: when the sun is just above the skyline, to 90°: when the sun is directly overhead. The
greatest intensity of solar radiation striking the Earth’s surface can be observed at solar noon. This is when the
sun is at its highest position (90°) in the sky, on a clear, cloudless day (Energy information administration,
2020). At angles less than 90°, the solar rays travel longer distances through the atmosphere, making them less
intense by the time they reach the Earth’s surface.
Scientific researchers record the amount of solar radiation incident on specific locations at various periods
during the year. These values are used to estimate the amount of solar radiation incident in other locations with
similar latitudes and local weather. Solar energy measurements are usually expressed as the total amount of
solar radiation on a horizontal surface, or as the total solar radiation on a surface tracking the sun. Solar
radiation data is usually represented as kilowatt-hours per square meter (Office of energy efficiency and
renewable energy, 2013).
2.2 Solar Insolation at System Site
The solar insolation is the actual amount of solar radiation incident upon a unit horizontal surface over a
specified time for a given locality. It is important for the geographical location selected as the site for a solar
powered system to be studied. The performance of any solar powered system is reliant on the insolation
available at the system’s site. The insolation available at different geographical locations vary, therefore the
meteorological data of the area where the system is located is necessary for the system design. Ethiopia lies
between latitudes 3°N to 17.5°N and longitudes 33°E to 47.5°E, and is a region with high solar irradiance
throughout the year.
Since Ethiopia is located near the equator, its solar resource is obviously of significant potential. The annual
average daily radiation in Ethiopia reaching the ground is estimated to be 5.5kWh/m 2 /day which vary from a
minimum of 4.5kWh/m 2 /day in July to a maximum value of 6.5kWh/m 2 /day in February and March.
2.3 Operating Principles of a Solar Water Heater Based on the Thermosyphon Principle
When exposed to sunlight, solar radiation passes through the transparent cover of the solar collector and strikes
the black-coated metallic plate which absorbs the incident solar radiation as heat. This causes an increase in the
internal energy of the solar collector and causes it to become hot. The working fluid in the piping system, firmly
bound to the black-coated metallic plate, absorbs this heat. This working fluid, then expands due to the heat
addition, hence it reduces in density. Based on the thermosyphon principle, the heated fluid rises by natural
convection, through the pipes at the top of the collector into the storage tank, while the cool fluid from the
storage tank flows into the collector by gravity. Hence, the heated water gets transported due to an increase in
both temperature and volume (Ogie et al., 2013). The cycle continues in this manner till the water in the storage
tank is at the required temperature. When the required temperature is achieved, the valves can be closed
manually, or a thermostat can be used to monitor and control the cycle. Figure 2.1 shows a typical flat-plate
collector.
2.4 Types of Solar Water Heating Systems
Based on the means by which the heat transfer fluid flows through the SWH, solar water heating systems are
either passive systems or active systems.
2.4.1 Active SWH:
This includes two types itself:
o Direct-Circulation Systems: the water is circulated using a pump through the collectors into the home, and it
is used mainly in places that rarely freezes.
o Indirect circulation systems: a non- freezing, heat-transfer fluid is circulated using a pump through the
collectors and a heat exchanger, which heats the water used into the house. This type is mainly used in freezing
temperatures.
2.4.2 Passive SWH:
This includes two types itself:
o Thermosiphon Systems: in this type, water rises naturally from the collectors to the storage tank, after the
water is heated it rises in the tank and the cooler water sinks down and it requires no external force to move the
water such as a pump.
o Integral Collector- storage Passive Systems: water flows in large tubes within the collector by the pressure
of normal water and stays in the tubes to heat which work also as a storage for the water. When the hot water is
required, the heated one is circulated by cold pressure that replaces it in the tubes.
2.5 Solar collector concepts
1. Aluminum foil plate with a refrigerator condenser coil: Basic components: Aluminum foil,
Refrigerator condenser coil, wooden frame, Glass cover
Aluminum foil: The aluminum foil is to serve as a solar reflector. Meaning the incoming heat will not
only be absorbed by the condenser coil but also reflected back to the pipes once more by the aluminum
foil.
Refrigerator condenser coil: Condenser coils usually come in small diameters. This makes them
conducive for our purposes since they are designed for optimum heat exchange. Additionally, they are
factory designed for the purpose of heat diffusion and are usually made of copper.
wooden frame: We use wood as our frame because it has low thermal conductive properties. This means
that the thermal loss is minimized.
Glass cover: This will be useful in creating greenhouse effect and trapping heat within the frame
Features
The aluminum foil is to serve as a
solar reflector. Meaning the incoming
heat will not only be absorbed by the
condenser coil but also reflected back
to the pipes once more by the
aluminum foil.
Cons
Aluminum foil has low thermal mass, this
means the foil in itself will not carry much
heat but rather reflect it off.
Condenser coils in the market are expensive
going on up to 1000 ETB on the market.
Condenser coils usually come in small The dimension of our collector may only be
diameters. This makes them conducive defined by the size of the condenser coil.
for our purposes since they are
designed for optimum heat exchange.
Additionally, they are factory
designed for the purpose of heat
diffusion and are usually made of
copper.
We use wood as our frame because it
has low thermal conductive properties.
This means that the thermal loss is
minimized.
This will be useful in creating
greenhouse effect and trapping heat
within the frame
2. Wooden panel painted black to absorb heat with spiral tubing:
Basic components:
Spiral tubing made of rubber tubes painted black, Black wooden panel:
Features
Cons
The spiral setting of the tubing will increase
heat transfer area. Additionally, painting out
surfaces black will provide with increased
heat absorption.
Wood is not a very good thermal mass due to
its material property and low density
Black painted panel will also serve the
purpose of solar absorption
Wood is not a reliable material in terms of
thermal resistance and may be damaged over
time
We can also use glass as a cover
Rubber tubing is not suitable for heat transfer
3. Copper pipes with aluminum covering to enhance heat conduction:
Components: Frame made out of roof edging, copper pipes and hinges, black paint, glass cover, wooden
back board, solar fins, aluminum sheets (to protect from moisture), foam seal tape, polycarbonate
*The collector frame is to be designed out of roof edging which is produced out of aluminum also.
Features
Cons
The roof edging frame is suitable for higher
structural support and also resistance to the
elements and corrosion
Might be expensive and difficult to acquire
components for.
Copper pipes are ideal for higher heat transfer
since copper is a great heat conductor.
Solar fins that are made out of aluminum will
provide higher heating. Aluminum is a good
conductor of heat. In fact, it has a high
conductivity comparable to copper.
Wooden back board serves as a support for
the copper pipes and also a thermal insulator.
Aluminum seals to protect from moisture
exposure of the wooden backboard
Foam seal tape to provide edge insulation
Polycarbonate traps the heat within the
collector frame box at a higher level than
glass
Very high efficiency and temperature output.
Water can be heated to boiling temperatures.
Cost effective Solar thermal water heater concept
This is the optimized solar thermal water heater concept, moving forward that we hope to design.
A. Basic components:
1. Solar collector:
This is a mechanism by which the solar energy is harvested and converted into heat energy. A major
working consideration here will be a heat exchanger mechanism. Meaning that the water to be heated is
made to circulate in such a way that the thermal energy diffuses into the water. The construction will
consist of two components.
1.1 Tubing: The water is circulated through tubes which are made smaller so as to facilitate water
diffusion. Smaller diameter of tubing implies higher surface area to volume ratio which is desirable
in our case. The tubing is made out of copper to be thermally permeable so as to let the heat through
to the water with the highest efficiency.
1.2 Pipe joints: These are to be used to connect to parallel water pipes. We will be using T-joints to
create that link.
1.3 Metal frame: We will use a metallic frame in order to improve the thermal and structural properties.
Additionally, we will use aluminum for our purposes in order to have lower weight.
1.4 Back board and surround insulation: Our frame is constructed with thermally insulating materials. In
our case we will be using wood which is a good choice since there is reduced thermal exposure. We
will need to use hydro protection from the pipes. We will use aluminum foil for that. There is a need
for thermal insulation on the edges of the frame to create thermal insulation.
1.5 Glass cover: We desire to create a greenhouse effect. This is when the thermal energy that travels
through the glass in the form of radiation is unable to escape back out in the form of convection.
Depending on the availability of materials, we hope to use glass but in the event we can’t procure
glass, we will be using transparent plastic covering alternatives.
1.6 Aluminum fins: We hope to use aluminum that encloses the pipes so as to provide increased thermal
retention. Aluminum is known to have highly conductive properties and also very easy to manipulate
and shape to our desired geometry. Therefore, it is the perfect candidate to serve our purposes.
2. Water tank:
This is going to be important in storing the water for extended lengths. The water is pumped in and out
of the tank. We need this tank to be thermally insulated so the water can be kept at the desired
temperature for extended amounts of time. Preferably produced from plastic.
3. Water pump
We will use a water pump to aid in circulating the water. The water tank is normally placed above the
solar collector mechanism. This is because gravitational force will assist in allowing the downward flow
of water. Additionally, thermosiphon will be relevant in this case especially as the water gets heated.
This is a phenomenon where the heated water with lower density will tend to rise above cold water with
higher density there by creating a cyclic circulation. These two forces in addition to the work of the
pump will serve in circulating the water about our system.
4. Connector pipes: These pipes can be made out of PVC in order to reduce heat loss in transmission from
the point of exit from solar collector to point of entry into water tank. We will be using 8.5 mm piped.
CHAPTER THREE
DESIGN AND METHODS
3.1 Design and Dimensioning of the SWH
The sizing of a solar water heating system depends on the daily hot water requirement, the required capacity of
the storage tank, collector area sufficient for the heating load, and the solar irradiance at a particular location.
The objective of the solar water we are designing is to provide warm water for hand wash purposes. So the daily
hot water requirement will be decided accordingly. We have estimated the daily hot water demand for this
purpose to be 20 liters per day. And we will get the total volume of the storage tank by multiplying it by a factor
of 1.2 which accounts for some unforeseen circumstances.
Total storage tank volume:
Determination of thermal energy required
Now that we found the total volume to be heated, we can calculate the amount of thermal energy required to
heat up 24 litres of water using the following formula:
Where
Qst-amount of thermal energy required to heat the total water volume from Ti to To(KWH)
m-total mass of the water to be heated
Cw-specific heat capacity of water in J/kg0C
Ti=ambient temperature=130C
To=outlet temperature=500C
Collector Sizing based on the heat energy required
The solar collector is sized according to the amount of heat energy required by the system. The irradiance
values at the system site and the collector efficiency are also important in the determination of the collector
area. Efficiency of the collector can be calculated by:
Where
I=solar irradiance in KWH/m2/day
Ac=collector area in m2
η= Collector efficiency
From data we have found that the Irradiance in Ethiopia is highest in the month of January at about
5.085KWH/m2/day
Assuming efficiency of 40%
Determination of pipe diameter
We can find the pipe diameter by using the following formula:
The heating time per flow cycle, tn is given by:
Where:
t=total heating time=7hrs
n=number of flow cycles=5
The volumetric flow rate is determined by the following formula:
Where:
Vst = total storage volume =24litres
Let us assume the flow velocity U=0.1m/s
3.3 Construction of Solar Water Heater
1. The first step is to cut the pipes to appropriate dimensions, thread and then assemble them.
2. Then we constructed the wooden frame. This was done by cutting the wood to the specified dimension
and attaching the sides using glue and nails.
3. Following this, we cut ply wood to dimension to serve as the base of the wooden frame
4. A sheet metal was cut to dimension to be placed on top of the ply wood
5. We cut pexi-glass to dimension to fit our wooden frame
6. The inside of the frame was thoroughly spray painted black to ensure thermal properties
7. We then constructed the frame using angle iron and rectangular hollow section. The metals were joined
by welding
8. The collector was assembled
9. We finally placed the collector on the frame, and installed the water tanker and the tube connections.
3.4 Solar Water Heater Performance Evaluation
I. Testing Protocol Model
Many test procedures have been proposed by various organizations to determine the thermal
performance of solar water heaters. Testing of the complete system may serve a number of
purposes.
The main one is the prediction of the system’s long-term thermal performance. System
testing may also be used as a diagnostic tool to identify failure and causes of failure in
system performance.
Other purposes include the determination of the change in performance as a result of operation
under different weather conditions or with a different load profile. The International
Organization for Standardization (ISO) publishes a series of standards, ranging from simple
measurement and data correlation methods to complex parameter identification ones. ISO9459
was developed by the Technical Committee, ISO/TC180d Solar Energy, to help facilitate the
international comparison of solar domestic water-heating systems. Because a generalized
performance model, which is applicable to all systems, has not yet been developed, it has not
been possible to obtain an international consensus for one test method and one standard set of
test conditions. Therefore, each method can be applied on its own.
Based on that , ISO9459 has at the time being three active parts within three broad
categories. These are :
Rating Test
This is used for characterizing the performance of solar domestic water heating systems operated
without auxiliary boosting and for predicting annual performance in any given climatic and
operating conditions. It is suitable for testing all types of systems, including forced circulation,
thermosiphon, and Freon-charged collector systems. The results allow systems to be compared
under identical solar, ambient, and load conditions. The entire test sequence usually takes 3–5
days and the result is the daily solar contribution
1
for one set of conditions. An indoor test procedure in which the solar simulator is replaced
by a controlled heat source, used to simulate the solar energy gain, is also described. This
test has not been widely adopted.
Black Box Correlation Procedures
This is applicable to solar-only systems and solar preheat systems. The performance test for
solar-only systems is a “black box” procedure, which produces a family of “input–output”
characteristics for a system. The test results may be used directly with daily mean values of
local solar irradiation, ambient air temperature, and cold-water temperature data to predict
annual system performance. The results of tests performed permit performance predictions for a
range of system loads and operating conditions, but only for an evening draw-off. This one is a
commonly used testing procedure for homemade solar water heaters and the one we are going to
implement to test our prototype.
Testing and Computer Simulation
It is a draft standard that suggests a procedure for characterizing annual system
performance and uses measured
component characteristics in the computer simulation program TRNSYS . The procedures
are used to determine collector performance, whereas other tests are specified for
characterizing the storage tank, heat exchangers (if used), and control system. It presents a
procedure for the dynamic testing of complete systems to determine system parameters for
use in a computer model. This model may be used with hourly values of local solar
irradiation, ambient air temperature, and cold-water temperature data to predict an annual
system performance and gives a very reliable and accurate results.
II. Instrumentation
Instrumentation used in solar energy systems varies from very simple temperature and pressure
indicators, energy meters, and visual monitors to data collection and storage systems. It is
generally preferable to have some kind of data collection to be able to monitor the actual energy
collected from the solar energy system. Visual monitors are used to provide instantaneous
readings of various system parameters, such as temperatures and pressures at various locations
in the system. Sometimes, these are equipped with a data storage. Energy meters monitor and
report the time-integrated
Solar Water Heater Performance Evaluation
2
quantity of energy passing through a pair of pipes. This is done by measuring the flow rate and
the temperature difference in the two pipes. Most energy meters must be read manually, but
some provide an output to a recorder. Automatic recording of data from a number of sensors in a
system is the most versatile but also the most expensive system. This requires an electrical
connection from the various sensors to a central recorder. Some recorders also allow processing
of the data. Nowadays, systems are available that collect and display results online on the
Internet. These are very helpful in monitoring the state of the system, although they add to the
total system cost. In countries where schemes such as the guaranteed solar results operate, where
the solar energy system provider guarantees that the system will provide a certain amount of
energy for a number of years, however, this is a must
The above stated instruments might not be readily be available in our case therefore we have to
utilize existing apparatus to measure our data . The instruments we used are :
1. Type *** Thermocouples to measure
Between pipes and inner case
Absorber surface
Ambient temperature
2. Data Logger :
To collect temperature readings in specified time increments
3. Stopwatch & calibrated container :
To obtain the volume flow per minute
III. Test Variables and Setup
Independent variables :
Absorber
Galvanized steel pipes
Insulation
Fiberglass
Black paint
Solar Water Heater Performance Evaluation
3
Along with these mentioned variable the total radiation from the sun is considered to be an
independent variable as well
Testing to evaluate (Dependent Variables):
Length of time to heat up 20L of water at a range between (13-50°C)
Ability for the system to retain heat
Efficiency of the system
IV. Testing Setup
The figure below shows the designed solar water heater. The collector is tilted at an angle of
9°with respect to the horizontal plane . Since Ethiopia is in the northern hemisphere , the
system is directed south for the testing . The ambient temperature ,
the inlet and outlet temperature from the collector were measured every hour from 10am to
3pm for a single day . It should be noted that the weather condition and the time constraint
affected the accuracy of the test & limited the duration.
The flow rate was determined by using a stopwatch and a calibrated container to obtain the
volume of flow per minute. This was done repeatedly, and an average value of ———litres /min
was found. The solar irradiance data for the time period was also obtained from the “Solcast”
website.
V. Testing procedure
1. The solar water heater was positioned southwards to ensure reception of solar radiation
throughout the testing period
2. The storage tank was then filled with water using the buffer tank an connected flexible
pipes
3. The ambient temperature was recorded, and the initial readings of the inlet and outlet
temperatures were taken from the attached thermometers
4. The inlet valve to the collector was opened to start the cycle
5. Step 3 was repeated every hour till the end of the heating period
6. The irriadiance values for the day were obtained from the Solcast website.
Solar Water Heater Performance Evaluation
4
CHAPTER FOUR
RESULTS AND CONCLUSION
4.1 Results and Discussion
Results
The data required for the performance analysis of the SWH can be seen below. , the
instantaneous system efficiency was calculated using Equation below for each set of data.
=
heat output
Qst heat
input = I A c
Where I is the solar irradiance in KWh/m 2 /day , η is the collector efficiency and Ac is the
collector area in m2
Time(h) Ambient
Temp(C)
08:15
17
Outlet Temp(C) Inlet Temp(C) Efficiency(%
)
40.2
17.2
15.9
08:30
17.4
42.6
19.1
16.3
08:45
17.3
30.4
19.1
7.84
9:00
19.5
29.3
18.8
7.28
9:15
20.1
25.6
18.9
4.65
Table : Readings for the first experiment
Challenges during testing
 Leakage
 Difficulty in measuring inlet and outlet temperature
 The plastic container kept losing heat due to material type used
 Level of outlet valve aligned with the outlet from the collector
5
4.2 Conclusion and recommendations
Conclusion
In this work, the design and construction of a 20-litre capacity portable solar water heater has
been carried out. using relevant equations to size the major components of the system. The
materials for the components were then selected with consideration to the design calculations,
machinability, market availability and cost of the materials but later were modified due to
constraints in manufacturability . The system was tested, and the following results were
observed. From a single day of testing , the highest outlet temperature recorded was —-°C . For
the last three hours of testing , the highest outlet temperature recorded was —-°C . This
difference clearly shows that the system performs better during the sunny & dry season when the
irradiance levels are higher. The highest irradiance recorded was —— W/m2 on the —— hour of
testing while the highest efficiency recorded from the system was ——% .
Recommendations
Due to time and financial constraints, the following are recommended as future
modifications that should enhance system testing and performance:
1. Installation of a sensor to determine water level and control flow.
2. Installation of a flow meter to easily get flow rate of working fluid.
3. Computer based simulations on TRYNSYS to measure component characteristics and
implement necessary modification.