OPTIMIZATION OF SOLAR POWER

USING DIFFUSED REFLECTORS

Contents

1. INTRODUCTION

2. LITERATURE REVIEW

REFRERNCES

INTRODUCTION

1.0 BACKGROUND

The global energy demand is continuously increasing. In 2009, global energy production was

high, in fact 86% dependent on fossil fuel resources [1]. These resources are limited and their use

results in the massive climate change through the greenhouse effect and produced large scale

environmental pollution. To provide a sustainable and clean power production in future, focus of

the energy world is now shifting to renewable resources of which solar energy is a major one. In

2003, the world production of solar cells was estimated to be 742 MW while in 2009 was 9.34

GW, an increase of over 1000% in six years [1-2]. This extraordinary growth is driven to some

degree by improvements in materials and technology.

In the past 30 years till present, solar energy has increased in efficiency and its price levels have

improved dramatically. Today the theoretical efficiency of a solar PV cell is said to be around

the 25% to 30% mark and a practical efficiency around the 17% mark [1-2]. The improvement in

efficiency production of solar energy system will make big difference in the use of solar panels.

Several methods are used to enhance performance of solar units. The commonly used method is

by sun tracking, which has some disadvantages such as high cost. Other methods suggested here

are by using good reflectors e.g. mirrors or shiny objects/metals or using white reflectors. Highly

encouraging results have been obtained by using diffused reflectors in times past.

In this project, I am required to use my design and innovation skills to design a Solar System

which will be able to increase efficiency by tapping more sun rays using well aligned diffused

reflectors. The solar system which is to be built is a final year project in partial fulfillment for the

requirements for the award of B.Sc in Mechanical Engineering.

The report of the project will detail the Literature Research, Overview of the development of the

system, the results achieved, some discussions and reflections related to the project.

2.0 PROBLEM STATEMENTS

Increasing efficiency of solar panels so as to reduce cost

Creation of a well aligned system for best exposure to sun rays with good support

structure to always keep the machine in place and withstand adverse atmospheric

conditions such as strong wind during operation

Material selection

Cost implications of the project

3.0 OBJECTIVES

To create an alternative power source using solar power

To evaluate efficiency improvement of the solar unit by using reflectors so as to reduce

cost

To check the comparative advantage over other optimization processes

4.0 JUSTIFICATION

According to market economy, the increasing worldwide demand for energy, forces a continuous

rise in the price of fossil combustibles. This market behavior brings a positive challenge to the

scientific community as more funds are allocated for the research and development of new

alternatives. Among these renewable energy sources is solar energy.

Solar living and using solar electric panels to provide solar electricity for our homes could be an

easy transition from receiving power from the power companies. The cost difference with other

known sources could be an initial burden but in the long run, would be preferable. Solar panels

are used to tap energy from the sun but it has its limitation due to its low efficiency compared

with other sources. Because of this, a large number of panels are needed meaning more money is

used to set up a solar unit that is capable to meet our needs.

In this paper, an intelligent reflector system for efficiency maximization is proposed for

development to reduce number of panels needed so that the money to be spent on a solar system

can be reduced to some extent (bearing in mind that these reflectors cost less than panels)

5.0 SCOPE

In this project, scope is needed to specify the range in the completion of the project.

Basically for the development, the type, size and number of solar panels as well as the reflectors

are needed. The size of the platform, its weight and maximum weight it can carry must be

factored into the design for stability purposes. The alignment of the solar panels and the reflector

with each with respect to the direction of the sun rays must also be considered.

Below is a flow chart that gives more detail concerning the scope of the project.

FLOW CHART

A flow chart, or flow diagram, is a graphical representation of a process or system that details the

sequencing of steps required to create output. This flow chart was present steps or process of

final year project that I will present in this semester. Figure 1.0 shows that process to complete

my final year project.

NO

YES

NO

YES

Figure 1.0: Flow Chart

START

TOPIC GENERATION

COLLECTING DATA FROM ANY SOURCES

SKETCHING A DESIGN

DESIGN SELECTION

MODIFICATION OF DESIGN

FINAL DESIGN

METHODOLOGY

FABRICATE

EVALUATE PRODUCT

PRESENTATION

REPORT

END

The final year project starts with the title generation by me. Then, a proposal would be sent to

my proposed supervisor for deliberation, modification, if needed, and approval. From that data,

literature review is needed to achieve the objective. Data were to be collected from any research

such as book, magazine, web site, or video. This step helps to create a design that suite to the

product.

Regarding to the data that would be collected, a design is needed for the manufacturing process.

The designs were to be created by following the scope of project. It is to make sure the designs

are following to the specification. After that, the designs that would be created will continue to

the selection of designs and the best design will be a final design and improving the design if

needed. Then, it is ready to be manufactured.

A final design must be completed with dimensions to proceed to manufacturing process. The

manufacturing process would involve cutting, welding, grinding, drilling and so on. Then

proceed to the testing and evaluation process. A product will be tested to see if it fulfills the

requirement such as safety, ability and strength. During the test, if problem occurs, the process of

manufacturing the machine will step back to the previous process. The reason to step back is to

fix the error.

After all the parts would have been joined together with no errors, here comes the phase of result

and discussion. In this part, the function will be informed. Beside, how to achieve objective and

solve problem statement of the project would be discussed in this phase.

LITERATURE REVIEW

This chapter aims to provide the reader a brief knowledge of Solar Panel, details concerning

various reflectors and how reflectors are used in solar systems to improve efficiency.

Principle of Operation of Solar Energy

Solar energy is available in abundance in most parts of the world. The amount of power radiated

by the sun is 3.9 x 1026 W. This awesome amount of power can be scarcely comprehended. The

total energy produced in the world in each year by all the world’s energy sources is equivalent to

the amount the sun produced in about 1 billionth of a second [3]. Also, the amount of solar

energy incident on the earth’s surface is approximately1.5 x 1018 kWh/year, which is about

10,000 times the current annual energy consumption of the entire world. The density of power

radiated from the sun (referred to as solar energy constant) is 1.373 kW/m2 [4].

Solar cell is a device which converts photons in Solar rays to direct-current (DC) and voltage.

The associated technology is called Solar Photovoltaic (SPV). A typical silicon PV cell is a thin

wafer consisting of a very thin layer of phosphorous-doped (N-type) silicon on top of a thicker

layer of boron-doped (P-type) silicon. An electrical field is created near the top surface of the

cell where these two materials are in contact (the P-N junction).

When the sunlight hits the semiconductor surface, an electron springs up and is attracted towards

the N-type semiconductor material. This will cause more negatives in the n-type and more

positives in the P-type semiconductors, generating a higher flow of electricity. This is known as

Photovoltaic effect.

The amount of current generated by a PV cell depends on its efficiency, its size (surface area)

and the intensity of sunlight striking the surface. For example, under peak sunlight conditions a

typical commercial PV cell with a surface area of about 25 square inches will produce about 2

watts peak power.

Governing principles of Solar Energy

Solar irradiance: The amount of solar power available per unit area is known as

irradiance. Irradiance fluctuates according to the weather and the sun’s location in the

sky. This location constantly changes through the day due to changes in both the sun’s

altitude (or elevation) angle and its azimuth (or compass) angle. Figure 2 below shows

the two angles (the sun’s elevation angle and the sun’s compass angle) used to specify the

sun’s location in the sky.

Figure 2: Sun’s location in the sky

Solar constant: The solar constant is the amount of incoming solar electromagnetic

radiation per unit area, measured on the outer surface of Earth's atmosphere on a plane

perpendicular to the rays. The solar constant includes all types of solar radiation, not just

the visible light. It is estimated to be roughly 1,366 watts per square meter (W/m²) [4].

Direct and Diffused Reflection: Sunlight coming from the sun is reduced by about 30%

before it reaches the earth due to

o Scattering by atmospheric particles

o Scattering by aerosol, dust particles etc.

o Absorption by atmospheric gases

It is common to consider separately the ‘direct’ (or beam) radiation coming from solar disk and

the ‘diffuse’ radiation from elsewhere in the sky with their sum known as ‘global’ radiation. The

component of the radiation coming from all direction in the sky is diffused. When the sun is

directly overhead, it has diffuse component of about 10% when skies are clear. Percentage

increases with increased Air Mass.

Reflectors

A flat solar panel can incorporate reflectors at the side. This reflector is a reflective surface used

for gathering and reflecting solar energy in a system being powered by solar energy. It comprises

a substrate with a reflective layer for reflecting the solar energy, and in most cases an

interference layer.

The idea is to increase the sunlight intensity onto the panel by reflecting sunlight that would

normally have missed panel. Reflectors can be situated at an optimum angle to gain the greatest

possible level of sunlight that can be achieved onto the panel. This idea of using this type of

reflector is a lot simpler and less complicated than the existing concentrators. By increasing the

amount of sunlight onto the panel you also increase the amount of heat that is being produced as

well. Therefore a heat factor must be taken into consideration when designing a reflector system

onto the panel.

TYPE OF REFLECTOR PANELS

The type of reflector panel is used in a concentrating solar panel can influence the output power.

The different types of reflectors used (according to my research) include

Mirror

Aluminium reflectors

Stainless steel reflectors

Chrome film reflectors

Silver reflectors

White reflectors

Figure 3: A solar panel with reflectors attached

These different types of reflectors have been tested in times past to determine which type of

reflector will be both efficient, practical and do not produce excess heat. The reflective layer is

designed to reflect the maximum amount of solar energy incident upon it.

Reflection by a mirror:

Utilizing the reflected light from a mirror, the output current of the cell was significantly high.

Mirrors normally concentrate the sun beam over a small area of the panel. This result to a high

current density in the concentrated light beam area of the p-n-junction that creates non-uniform

current density in the panel and heated spot may be formed in the highly concentrated beam area.

This may degrade the useful life of the panel. So mirrors or highly reflecting surfaces are not

advisable for the purpose of performance enhancement of the solar panel.

Reflection by white Reflector:

A white reflector reflects all the electromagnetic rays from the sun. Hence it is a good method for

increasing amount of solar energy being converted to electrical energy through photovoltaic

cells. When the experiment was carried out with a solar panel using white reflectors aligned at

23.50 to the horizontal, it was found out that the percentage improvement is as high as around

25% as compared with a system with no reflectors [3].

Reflection by chrome film:

An overwhelming increase in power output when chrome film is used on the reflector plate. An

average power output of 25.94W was recorded for chrome reflectors. These chrome reflectors

produce a 27.65% increase in power output against aluminium foil and a 34.05% increase in

power output against stainless steel, although it is more expensive than the two. The reflectors

were fixed to optimal angle of 22.5° throughout the recordings [2].

Reflection by metallic film:

The layer comprises a highly reflective thin metal film. Because of sensitivity to abrasion and

corrosion, the metal layer is usually protected by the substrate on top, and the bottom may be

covered with a protective coating, such as a copper layer and varnish. Basically, the metals used

are silver, aluminium and stainless steel.

According to [1], by implementing reflector with panel, the rated output of a solar panel can be

increased. The output can be increased around 40% by using this method (using angles 450, 550

and 650 between the panel and the reflector, testing in cloudy and sunny days). The aluminum

finish reflector improved solar cell output than all other reflector. Despite this, aluminum is not

always used as the reflective layer. The use of silver as the reflective layer is claimed to lead to

higher efficiency levels, because it is the most reflective metal. This is because of aluminum's

reflection factor in the UV region of the spectrum. Locating the aluminum layer on the first

surface exposes it to weathering, which reduces the mirror's resistance to corrosion and makes it

more susceptible to abrasion. Adding a protective layer to the aluminum would reduce its

reflectivity.

Due to the result of [1] and availability as well as reduced costs of using aluminium reflectors, it

would be used in this project.

REFRENCES

[1] Antara Debnath Antu, Md. Robiul Islam Sarkar, Naser Md. Isteaque Alam – “Performance

Improvement of PV Solar System by Diffused Reflection”. Department of Electrical and

Electronics Engineering, BRAC University, Dhaka, Bangladesh, August 2010

[2] J. Rizk, and M. H. Nagrial – “Impact of Reflectors on Solar Energy Systems”. World

Academy of Science, Engineering and Technology, 2008.

[3] Rizwan ur Rahman, Dewan Ishtiaque Ahmed, Mufrad Ahmed Fahmi, Tithi Tasnuva, Md.

Fayyaz Khan – “Performance Enhancement of PV Solar System by Diffused Reflection”.

Department of EEE, United International University, Dhaka, Bangladesh. 2000

[4] Dr. P. Jayakumar – “Solar Energy - Resource Assessment Handbook” September 2009

[5] John A. Duffie, William A. Beckman – “Solar Engineering of Thermal Processes”. (2nd

edition).