This document summarizes a research study conducted by students at the University of St. La Salle comparing the efficiency of a solar-powered phone charger to a wall phone charger. The study includes an introduction outlining the background, problem statement, hypothesis, objectives and limitations. It also includes a literature review on solar energy and efficiency calculations. The methodology section describes the experimental research design used to test the chargers. The findings are presented, showing the solar charger had an efficiency of 69.33% compared to 71.85% for the wall charger. In conclusion, the researchers determined the solar charger to be as efficient as the wall charger, while noting it took longer to fully charge a battery. Recomm

1. UNIVERSITY OF ST. LA SALLE
Aside from being portable, a Solar-powered
Phone Charger is as efficient as the Wall
Phone Charger
A research requirement for English 2
Kirby Cabrillos, John Vingem Geaga, Reg Vincent Natividad, Ryan Ceazar Santua
10/7/2013

2. Contents
1) Abstract ........................................................................................................................ 3
2) Chapter I ...................................................................................................................... 5
3) Introduction ................................................................................................................. 5
a) Background of the Problem .................................................................................... 5
b) Problem Statement .................................................................................................. 6
c) Hypothesis of the Study .......................................................................................... 6
d) Significance of the Study ........................................................................................ 7
e) Research Objectives ................................................................................................ 8
f) Scope and Limitations of the Study ........................................................................ 8
g) Definition of Terms............................................................................................... 10
4) Chapter II .................................................................................................................. 11
5) Review of Related Literature ................................................................................... 11
a) The Conversion of energy from light into electricity ........................................... 11
b) Potential of Solar Energy ...................................................................................... 12
c) Computing for Efficiency ..................................................................................... 13
d) Analysis of the Related Literature and Related Studies........................................ 14
6) CHAPTER III ........................................................................................................... 15
7) Methodology .............................................................................................................. 15
a) Kind of Research................................................................................................... 15
b) Research Design.................................................................................................... 16
c) Efficiency Test ...................................................................................................... 16
d) Experimental setup................................................................................................ 16
e) Measurement of the output currents and voltages for both chargers and tabulation
of results ................................................................................................................ 17
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3. f) Computation for the efficiency ............................................................................. 17
g) Calculation for the charging time ......................................................................... 18
h) Method of Analysis ............................................................................................... 18
8) Chapter IV ................................................................................................................. 19
9) Research Findings ..................................................................................................... 19
a) Efficiency test ....................................................................................................... 19
b) Calculation for the time required for a 1220 mAh battery to completely charge . 22
10) Chapter V .................................................................................................................. 23
11) Summary, Conclusions, Discussion and Recommendations ................................. 23
a) Summary ............................................................................................................... 23
b) Purpose of the Study ............................................................................................. 23
c) Restatement of Research Question ....................................................................... 23
d) Research Methodology ......................................................................................... 24
e) Results ................................................................................................................... 24
f) Conclusions ........................................................................................................... 24
g) Discussions ........................................................................................................... 25
h) Recommendations ................................................................................................. 25
12) Bibliography .............................................................................................................. 27
a) Books .................................................................................................................... 27
b) Published Thesis ................................................................................................... 27
c) Electronic Sources ................................................................................................ 28
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4. Abstract
Aside from being portable, a Solar-powered Phone Charger is as efficient as the Wall
Phone Charger
Kirby Cabrillos, John Vingem Geaga,
Reg Vincent Natividad, Ryan Ceazar Santua
October, 2013
As world‟s resources are diminishing, government agencies and non-government
organizations are pushing a greener solution through the use of renewable energy
sources. It was forecasted by some scientists such as Thomas Alva Edison that Solar
Energy will be the future energy source. However, it is still being studied on how to
improve the technologies used for utilizing solar energy. The solar panel for example,
laboratories throughout the world are chasing to develop the most efficient solar panel. At
present, the German-French research team holds the record for creating the 44.7 %
efficient solar panel. This means that their solar panel made of nitrogen and boron can
convert the 44.7 % of sunlight it receives into energy.
The portable solar phone charger is one of the devices that use light to charge a
phone. It is really portable that people on the road or on a camping can carry it into their
pocket and charge their phone where ever they want. However, it all boils down on how
fast the solar charger could transmit its charge and how efficient the charger is. A solar
charger can charge a phone anywhere but it should also be considered if it is as efficient
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5. as a wall charger. With this problem, an experiment was conducted to check if a solar
charger is as efficient as the wall charger. Efficiency test was conducted with the solar
charger and the wall charger. With the result obtained from the experiment, the solar
charger that has 69.33 % efficiency is close to the wall charger that has 71.85 %
efficiency. The result indicates a positive response and researchers conclude that solar
charger is indeed efficient as the wall charger. Also, the time for a 1220 mAh battery to
be fully charged using both chargers was calculated. The result indicates that it takes 2
hours and 40 minutes to charge the battery much longer compared with the 2 hour time
recorded for the wall charger.
The experiment shows that the world is now a bit closer to the perfection of solar
technology. Further studies on solar technology would help for the study on renewable
energy.
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6. Chapter I
Introduction
This chapter presents the background of the problem, problem statement, and
hypothesis, significance of the study, and the scope and limitations of the study.
Background of the Problem
Mobile phones are currently the most popular form of wireless communication in
almost all the countries throughout the world. According to the estimation of the
International Telecommunication Union, there are over 6.8 billion cellphone users around
the world and the number is growing fast as technology gets better and cost of production
lowers.
However, the average lifetime of a cellphone battery according to G. Chiang and
S. Bajaj (2011) is only around 8-12 hours with moderate usage. This becomes very
inconvenient for people especially on the road or occupied with work. People must bring
a wall phone charger and look for a power source in order to charge. Meanwhile, the
portable solar-powered phone charger is a device that uses light rays of a minimum
amount as the energy source to charge a phone. Cellphones are then charged without
plugging into a power source.
One of the advantages of using a solar-powered phone charger is its portability.
The size and weight of the charger make it fit into anyone‟s pocket. However, the
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7. worthiness of a solar charger boils down to how quickly it transmits a charge, and how
much power it gives off to the phone or how efficient the solar charger is.
The Webster‟s dictionary defines efficiency as the quality or degree of being
efficient. Technically, efficiency refers to as the ratio of useful energy delivered by a
dynamic system to the energy supplied to it. Efficiency is simply derived by the total
output over the total input.
Problem Statement
This research deals with the examination of the efficiencies of both solar-powered
phone charger and the wall phone charger. Specifically, the study should able to answer
the question if a portable solar-powered phone charger is as efficient as the wall phone
charger.
Hypothesis of the Study
Solar-powered phone charger is as efficient as the wall phone charger. With a
very little marginal difference of about ±5%, the study will prove the researcher‟s
hypothesis that a solar charger is as efficient as a wall phone charger.
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8. Significance of the Study
“I‟d put my money on the sun and solar energy. What a source of power! I hope
we don‟t have to wait until oil and coal run out before we tackle that” (Thomas Alva
Edison, 1931).
The oil embargo of the 1970s prompted a national surge of interest in solar
energy. A solar water heater was installed in the White House, and photovoltaic panels
first came into play, notably in California. While previously solar power as a direct
source of electricity had been limited to esoteric functions, such as in spacecraft,
companies began to form with the idea of using solar as a regular source of power for
ordinary homes (E. Goffman, 2008).
Theoretically, solar might seem an ideal energy source, as it is free and virtually
limitless. According to Greenpeace, The solar radiation reaching the earth„s surface in
one year provides more than 10,000 times the world„s yearly energy needs. Furthermore,
harnessing just one-quarter of the solar energy that falls on the world's paved areas could
meet all current global energy needs comfortably (Flavin).
A recent study conducted by the United States National Renewable Energy
Laboratory (NREL) shows that the annual average solar energy power in the Philippines
is around 4.5 to 5.5 kWh per square meter per day and the Asia has the minimum solar
energy technical potential of 0.18 terawatts and a maximum of 6.56 terawatts annually.
Results are much higher compared to Europe which has only 0.24 of maximum energy
potential. The North Africa has the highest potential of 17.55 terawatts and followed by
the Sub-Sarahan Africa with 15.12 terawatts.
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9. Studying about solar technology would be very essential for the world‟s
nonrenewable energy resources are already diminishing. The future of this technology
relies on such studies that involve reviewing the present solar technologies.
Examining if a single solar charger could charge a cellphone efficiently as the
wall phone charger, would determine on which areas on solar technology have to
improve.
Research Objectives
This study aims to examine the efficiencies of a solar charger and a wall phone
charger and be able to analyze the results and conclude that a solar charger is as efficient
as a wall charger.
Scope and Limitations of the Study
This study mainly focuses on examining the efficiencies of both solar charger and
a wall charger to conclude that the solar charger is as efficient as wall phone charger.
This study also involves the computation for the complete charging time of a
1220 mAh Li-ion battery using both of the chargers. The results may not be applied to all
solar devices since the study only covers a single solar charger and wall phone charger
for testing.
This study would have been more comprehensive, meaningful, and far-reaching if
it covered more solar devices which should have provided the much detailed basis for
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10. comparison. This, however, would mean more time, money and resources which
researchers didn‟t have.
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11. Definition of Terms
Amperes –unit of current, milli-Amperes –Amperes over 1x10^-3
Complete charging time- the time required for a battery to be fully charged
Current –rate of flow of electric charge, can be calculated by voltage divided by the
resistance.
Efficiency- The quality or degree of being efficient. In this research, it is referred to as
the relationship of voltage and current by output power. It is given as the output power
divided by the input power.
Kilowatt hour (kWh) - a unit of work or energy equal to that expended by one kilowatt
in one hour.
mAh- milli Amperes-hour. Battery rating.
Photovoltaic (PV) cells – semiconductor material such as silicon that generates voltage
when light strikes at it.
Power- needed to turn on a mechanical or electrical device.
Power (solar input) - product of voltage and current coming in of the circuit.
Power (solar output) - product of voltage and current coming out of the solar cell.
Voltage- Electric potential or potential difference expressed in volts.
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12. Chapter II
Review of Related Literature
This chapter presents a synthesis of facts that supports the following topics: The
conversion of energy from light into electricity; the solar energy potential; mathematical
approach in determining efficiency; and calculating the time for a battery to be
completely charged.
The Conversion of energy from light into electricity
sunlight
solar panel
charger
circuitry
battery
Figure 2.1: The Conversion of light energy to electrical energy flowchart.
Just as Law of Conservation of Energy states that “Energy cannot be created nor
destroyed but can only be transformed from one form to another”. This is where the idea
of solar energy came from, to transform the sun‟s raging light into lifelong, unharmful,
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13. and sustainable energy source for the human beings. An online journal, HowStuffWorks
explained the process on how sunlight is converted into electrical energy. Light basically
from the sun is absorbed by the Photovoltaic (PV) cells (made of semiconductor material
like silicon) or commonly known as solar cells, and directly converts into electricity.
When light strikes the semiconductor material, a certain amount is absorbed
which means energy from the source is transferred into the material and magnetic field
causes electrons to flow in a certain direction that now produces the current. The power
generated by the PV cells flow through a circuit design to charge the battery.
Potential of Solar Energy
A famous online magazine Live Science (2012) stated that the sun is the power of
the future in the 21st century. In the past, harnessing solar energy was an expensive option
for many to invest in and bank on solar energy for the provision of their energy needs.
However, advancements in technology made solar energy available with much lower cost
and improved efficiency.
Now with further study and understanding, solar energy can become the main
source of energy for all. Think Solar Energy, an online database stated that the solar
energy is the future source of our energy source and continuous improvement is a must.
The market share of solar energy is still low. Current electricity generation from PVs is
only of the order of 2.6GW compared to 36.3GW for all renewable energies,
hydroelectric power excluded. Developed countries are steadily increasing their
investments in solar power plants, and IEA projections for 2030 give an enhancement of
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14. solar electricity generation up to 13.6GW (80% of which will be from photovoltaic cells,
and the rest (2.4GW) from solar thermal plants). However, this amount will not exceed
6% of the total electricity production from non-hydro renewable energies. It is worth
noting that passive solar technologies for water heating, not included in these statistics,
represent a fairly large amount of power. IEA estimates a power production of 5.3GW in
2002 and an increase up to 46GW by 2030.
Computing for Efficiency
Power as defined by the Webster‟s dictionary is the time rate at which work is
done or energy emitted or transferred. In science, power can be calculated in various
ways. Power can be calculated in terms of resistance and current, it is the square of the
current multiplied by the resistance (P = I2R). Power can also be calculated in terms of
current and voltage, it is simply the product of the current and the voltage (P = IV).
In all sciences, efficiency is defined as output over input. The efficiency of an
engine for example is the ratio of the output work or energy to the input work or energy.
By this, efficiency could be plotted in an equation as:
or
. Each battery
has a rating. This rating refers for how much a particular battery can hold charges. An
iPhone 3gs battery for example has 1220 mAh. Computing the time to completely charge
a battery is given by the formula, hours =
. Continuous current refers to
as the current running in a single direction of the battery.
A recent study about the power generated from the transformer-rectifier circuit
was published by an online journal, righto.com (2012). Based on their study, the average
power output of the transformer-rectifier circuit is around 6.5 Watts.
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15. Analysis of the Related Literature and Related Studies
The related literature and related studies cited contains information relevant to the
experiment. Scientific ideas and results are presented in order to provide mathematical
approach for determining the efficiency of any device.
After a thorough review of the related literature and studies, it was found out that
there are several studies about the energy efficiency of different types of cellphone
chargers. They were however focused on the energy loses when the cellphone is not
connected in the charger but the charger is still connected in the power source.
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16. CHAPTER III
Methodology
This chapter presents the kind of research and research design used for the study
as well as the procedures of the experiment. The procedure used in this study was based
on the study conducted by Porter, et al (2008) regarding the Energy Efficiency Battery
Charger System Test Procedure that was commissioned by the Pacific Gas and Electric,
California Energy Commission-Public Interest Energy Research Program, and Southern
California Edison.
Kind of Research
The kind of research used in determining whether a portable solar-powered phone
charger is as efficient as a wall phone charger was experimental research.
Experimental research is a design in which “an investigator manipulates and
controls one or more independent variable or more variables for variation concomitant to
the manipulation of the independent variables” (Kerlinger, 1986). Experimental research
has been considered by Travers (1978) as the most prestigious method of advancing
scientific knowledge.
V. Ardales (1992) stated that the “ideal true experiment” study is the best done in
a laboratory setting where the researchers have full control in manipulating study
variables and ruling out confounding ones.
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17. In this research, the independent variable was the input power of both solar
charger and wall phone charger. And the dependent variable was the efficiencies of the
solar charger and the wall phone charger. While the extraneous variables were the time
which the experiment was conducted, the type of the weather on the date of testing, the
type of solar panel used, and also the number of trials conducted.
Research Design
The research was divided into two parts, the efficiency test and the calculation for
the time in which batteries will be completely charged. In efficiency test, currents and
voltages were measured for the output side of the chargers.
The test for solar charger was conducted in four trials with an interval of one hour
starting at 11 o‟clock in the morning. The test for the wall charger was also conducted at
the same time. The test was replicated four times to determine its average power.
The calculation for the time in which the battery will be completely charged was
done after completing the efficiency test. With the given formula, hours
=
, the time can now be drawn by the quotient of the battery rating over
the continuous current.
Efficiency Test
Experimental setup
The solar charger used in the experiment was ROHS P2600TM.While the wall
phone charger used was an original box type iPhone adapter charger. The same multi16 | P a g e

18. tester was used for each of the chargers. The experiment was conducted outdoor with an
approximate air temperature of 29 degree Celsius. The experiment started at exactly 11
am.
Measurement of the output currents and voltages for both chargers and tabulation
of results
Being the independent variable, the input current for the solar charger was set at
1000 milli-Amperes and the input voltage at 6 Volts since it was found on the product
specification. Meanwhile, for the wall charger, the power was at 6.5 Watts.
The next step was finding the output power for both chargers. Using a multitester, the current and the voltage were measured in the output terminals of the portable
solar-powered phone charger; its product was then recorded under the output power of
the solar charger. The same procedure was done for the wall charger and the result
however, was recorded under the output power of the wall charger.
Computation for the efficiency
A simple calculation was conducted to determine the efficiency of both chargers.
For the portable solar-powered phone charger, the recorded average output power was
divided by the input power. To get its percentage, the quotient was multiplied by 100.
This was labeled as efficiency percentage of a solar charger.
The same procedure was followed in computing the efficiency of the wall
charger. The result was labeled as efficiency percentage of a wall phone charger.
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19. Calculation for the charging time
The battery was connected in series with the multi-tester (ammeter function),
1kilo ohm resistor and the charger to identify what current was flowing through the
circuit and the result was labeled as the continuous current. The continuous current
divided the battery rating and the result was the time for the battery to be completely
charged.
Method of Analysis
All gathered information was recorded and presented in both tabular and
graphical form. The results from each test were then reviewed for any error in
calculations.
The efficiency percentage of the wall phone charger was multiplied by 0.05
(based from the 5% difference hypothesis of the researchers) to get the magnitude of the
range. The success of the hypothesis as well as the study relies on this result. If the
absolute value of their difference fits on the range, the study is therefore successful.
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20. Chapter IV
Research Findings
This chapter presents the data gathered from the efficiency test and the calculation
for the time required for a 1220 mAh Li-ion battery as well as the analysis of the results
and the analysis and interpretation of data.
The main purpose of this study was to determine the efficiency of both chargers
and prove that solar charger is as efficient as the wall charger.
A very simple experiment was conducted by the researchers. They used the
battery of an iPhone 3gs with a rating of 1220 mAh as the unit for calculating the time
required to charge completely.
Efficiency test
With the procedure to measure currents and voltages described in the third chapter
of this study, following results were obtained.
Solar
charger
Wall
charger
Trial
1
2
3
4
Ave.
1
2
3
4
Ave.
Input (independent)
Current (mA) Voltage (V)
1000
6
1000
6
1000
6
1000
6
1000
6
NA
NA
NA
Output
Current (mA) Voltage (V)
795
5.5
797
5.3
797
5.5
794
5.4
795.75
5.23
953
4.8
960
4.9
957
4.9
958
4.9
957
4.88
Table 4.1: Summary of measured currents and voltages (Note: the interval for each trial is in 1hour)
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21. Table 4.1 shows the summary of the measured currents and voltages for both the
solar charger and the wall charger. Since the input power for a wall charger was already
given at 6.5 Watts, its current and voltage values were not needed anymore. The input
current for the solar charger was 1 Ampere and its input voltage was 6 Volts.
Calculating for the power and the efficiency of both devices, these data were
gathered:
Input Power
(Pi=IiVi)
Solar
Charger
Wall Phone
Charger
Output Power
(Po=IoVo)
% Efficiency
(Po/Pi)x100
6 Watts
4.16 Watts
69.33 %
6.5 Watts
4.67 Watts
71.85 %
Table 4.2: Calculated Input and Output power, and percentage Efficiency
Table 4.2 shows the calculated input and output powers for both devices. The
efficiency was also derived with the calculated output and input power.
The average output power for the solar charger was 4.16 Watts while the output
power of the wall charger was 4.67 Watts. The Output power of the wall charger was a
bit higher compared to the solar charger. However, the input powers of both devices were
not the same. Solar charger‟s input power was given by 6 Watts meanwhile the wall
charger has 6.5 Watts. Calculating for their efficiency, the solar charger provided the
value of 69.33 %. This means that the solar charger only uses 69 percent of its input
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22. power. The percentage efficiency obtained from calculating from the wall charger‟s input
current and voltage was 71.85 %. The efficiency of the wall charger is a bit higher
compared to the solar charger.
0.8
0.7
Output power
0.6
0.5
0.4
0.3
0.2
0.1
0
0
0.2
0.4
0.6
0.8
1
1.2
Input power
Figure 4.1 Efficiency of the solar charger (blue) and the wall charger (orange)
Figure 4.1 shows the linear relationship between the output and the input power of
a solar charger and wall charger. The 5 % difference can be calculated by taking the 5%
of the wall charger efficiency or by simply multiplying 0.05 to the 71.85 % which would
yield a difference of 3.59. Subtracting the difference from the wall charger‟s efficiency
would give the minimum range of the 5% difference that is 68.26. Meanwhile, by adding
the difference to the efficiency would give the maximum range of 75.44. Now that the
range at which the researchers assumed to conclude that solar charger is as efficient as
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23. the wall charger is 68.26 % to 75.44 %. Efficiencies that fall under this range are
considered as efficient as the wall charger.
Calculation for the time required for a 1220 mAh battery to completely charge
Charger used
Solar Charger
Wall Charger
Continuous current
458 mA
615 mA
Battery rating
1220 mAh
Complete Charging Time
2 hrs., 40 min
2 hrs.
Table 4.3: Summary of calculated complete charging time
The current flowing through the terminals of the battery and the solar charger was
measured and the result was 458 mA. The result for calculating the time was 2.66 hours
or 2 hours and 40 minutes.
While the current flowing through the battery and the wall charger in series
connection was recorded at 615 mA. There, the time required for the battery to
completely charge using the wall charger is 1.98 hours or about 2 hours.
Charging a battery using a solar charger takes longer than using a wall charger.
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24. Chapter V
Summary, Conclusions, Discussion and Recommendations
This chapter presents the summary of the study. Included in this summary are a
review of the purpose of the study, a restatement of the research question, the research
methodology used, and a summary of the study results, conclusions and discussion.
Recommendations for further research and possible studies conclude this chapter.
Summary
Purpose of the Study
The main purpose of this study was to examine the efficiency of a solar-powered
mobile phone charger and prove that it is as efficient as the wall phone charger.
Restatement of Research Question
The research questions for this study were: (1) what is the efficiency of a solarpowered mobile phone charger and a wall phone charger? (2) What is the time required
to completely charge a 1220 mAh battery using both chargers , and (3) is solar-powered
mobile phone charger efficient as the wall phone charger?
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25. Research Methodology
There were two experiments conducted for this research. First, the efficiency test
which was testing the solar charger and recording the output current. Multiplying the
output current and output voltage provided the output power. And the input power was
given by the charger specifications. Dividing the output power over the input power
provided the value for efficiency. Multiplying the quotient by 100 provided the
percentage efficiency of the product. Using the same procedure above, the efficiency of
the wall charger was measured. The ideal efficiency of the charger was 100 percent.
An ideal charger refers to a charger which doesn‟t have power losses due to some
factors like heat and power absorbed by each components of the charger. An ideal
charger is not yet available today since all components of a charger is working, and work
requires energy, the energy is then the reason why it is impossible for now to achieve a
hundred percent efficiency for a device.
Results
The calculated efficiency of the solar-powered phone charger was about 69
percent and the wall charger efficiency was at 71.85 percent. The time required for a
battery to fully charge a 1220 mAh using a solar charger is 2 hours and 40 minutes.
Meanwhile for the wall charger, it takes about only 2 hours.
Conclusions
The findings of this research indicate a positive response that solar-powered
charger is as efficient as a wall charger. The calculated efficiency of the solar charger
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26. falls within the range which was assumed by the researchers to be ±5%. With 69 % of
efficiency, solar charger is within the range of 68.26 % to 75.44 %. With this, the
portable solar-powered phone charger is indeed as efficient as the wall phone charger.
The power generated by solar charger is 4.16 Watts and it can completely charge
a 1220 mAh battery for 2 hours and 40 minutes. While the use of the wall charger takes
only 2hours to charge the same battery.
With these conclusions, the researchers are now able to conclude for the problem
of this study.
Discussions
These findings indicate the wall charger has a higher efficiency and it takes a
shorter time to charge a battery. However, it still indicates a positive result. Not all
energy are transferred but dissipated to other forms like heat.
There may be several reasons why the efficiency is not that high aside from the
power losses. The type of solar cells was not that really new and it may have also low
efficiency (referring to the power absorbed from the sun).
Recommendations
After obtaining the results discussed above that answer to the problems presented
in determining if the solar charger is as efficient as the wall charger, the researchers have
arrived at the following recommendations to further improve the study:
1. The study has focused only on the efficiency of a single solar charger. In lined
with this, researchers highly recommend using other varieties of solar chargers.
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27. 2. If the future researchers may come into the probability of making efficient
chargers, researchers recommend using highly efficient solar panels and design a
stable circuit with lesser but effective components.
3. Moreover, future researchers are recommended to use varying amount of light to
consider the effects of brightness in charging.
4. Lastly, for future studies, it is recommended to use brand new products and much
newer materials. It is also recommended to focus more on the possibilities of
utilizing the solar energy as future energy sources for any electrical devices.
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28. Bibliography
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29. Green, M. A., Emery, K., Hishikawa, Y., Warta, W. (2011), Solar Cell Efficiency Tables,
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