BASIC SOLAR POWER SYSTEM

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BASIC SOLAR POWER SYSTEM

BY

OWEN WALSH

ELX3

PROJECT SUPERVISOR

1

DR. PASCAL O’CONNOR



Abstract

A basic solar power system is a system which takes the power from the sun and convertsit into electrical power.

Solar panels use what’s called “the photovoltaic effect”, this was discovered by Edmund

Becquerel in 1839, to produce electricity directly from sunlight.

Solar panels work best from direct sunlight but also work well even on cloudy days.Solar panels can supply a large amount of the electricity needs of a normal household.

They are usually mounted on the roof and can be connected into the local electrical utility

as seen in Fig. 1. This may be a costly investment at first to install but you will see thebenefits over time with a smaller electricity bill.

The applications are almost endless, but each has the same idea in mind: harnessing the

power of the sun to make clean, affordable electricity.

Fig. 1

2



Acknowledgements

I would like to thank my project supervisor Dr. Pascal O’Connor for all his help

throughout the year and for pointing me in the right direction.

I would also like to thank Liam Carroll for his help also and for providing me

with information needed to complete this project.

3

Lastly I would like to thank the other lecturers, technicians and classmates for

there help throughout the year.



Table of Contents

HOW SOLAR PANELS WORK ................................................................................................. 5

ANATOMY OF A SOLAR CELL............................................................................................... 6

MEAN DAILY SUNSHINE IN IRELAND................................................................................. 8

SOME QUESTIONS THAT ARE ASKED REGULARLY...................................................... 9

TRAJECTORY OF THE SUN................................................................................................... 10

SOLAR TRACKERS.................................................................................................................. 11

THE SYSTEM ............................................................................................................................. 13

TESTS CARRIED OUT ............................................................................................................. 14

Test 1............................................................................................................................. 15RESULT GRAPHS FOR TEST 1......................................................................................................... 16



Test 4............................................................................................................................. 23

RESULTING GRAPH FOR CHARGE TEST ......................................................................................... 25 Test 5............................................................................................................................. 26

RESULTS FOR TEST 5 ..................................................................................................................... 26 Incandescent bulb versus CFL Bulb ............................................................................. 27

PRACTICAL APPLICATIONS................................................................................................ 28

Lights along a Path........................................................................................................ 28

Electric Gates................................................................................................................ 29

OPPORTUNITIES FOR FURTHER TESTING ..................................................................... 30

Angle of Panel............................................................................................................... 30

Grouping of Panels ....................................................................................................... 30

Solar Tracker................................................................................................................. 30

4

BIBLIOGRAPHY ....................................................................................................................... 31



How solar panels work

The solar cells which are used to power a calculator and can be seen on the front of it areknown as photovoltaic cells also known as modules.

A module is made up of a group of cells that are all connected together either n series or

parallel in one frame an example of this would be a solar panel.Photovoltaic is the process by which you convert the energy you receive from the sun

into electricity. This process was first used in space but now it can be seen in manydifferent applications such as powering your house or on a boat to keep batteries charged.

The photovoltaic cells are made up of special materials called semi-conductors.

The most common type of this type of material is silicon and this would be the mostwidely used due to its chemical properties.

An silicon atom consists of 14 electrons which are on three different shells. The 2 shellswhich are closest to the atom are completely full but the outer shell is only half full

having only 4 electrons on it.The Atom is always wanting to have its outer shell full therefore it will share electrons

with four atoms next to it. It is this process that forms what is known as the crystalline

structure which is important to a PV cell.When the light from the sun hits the panel a certain amount of it is absorbed by the

semiconductor material there absorbing the energy. It is this energy that knocks the

electrons loose and allows them to flow freely. The cells also have electric fields whichcause the freed electrons to flow in a certain direction. This is then what’s known as

current. The current can then be drawn from the cell by attaching 2 cables to the cell, one

on the top and one on the bottom.It is this current combined with the cells voltage which determines to output power whichis taken from the cell.

5



Anatomy of a Solar Cell

Before now, the silicon was all electrically neutral. The electrons were balanced out bythe extra protons in the phosphorous. The missing electrons (holes) were balanced out by

the missing protons in the boron. When the holes and electrons mix at the junction between N-type and P-type silicon, however, that neutrality is disrupted.. Right at the

junction they do mix and form a barrier, making it harder and harder for electrons on theN side to cross to the P side. Eventually, equilibrium is reached, and we have an electric

field separating the two sides.

The effect of the electric field in a PV cell

This electric field acts as a diode, allowing (and even pushing) electrons to flow from theP side to the N side, but not the other way around. It's like a hill -- electrons can easily go

down the hill (to the N side), but can't climb it (to the P side).So we've got an electric field acting as a diode in which electrons can only move in onedirection. When light, in the form of photons, hits our solar cell, its energy frees electron-

hole pairs. Each photon with enough energy will normally free exactly one electron, and

result in a free hole as well. If this happens close enough to the electric field, or if freeelectron and free hole happen to wander into its range of influence, the field will send the

electron to the N side and the hole to the P side. This causes further disruption of

electrical neutrality, and if we provide an external current path, electrons will flow

through the path to their original side (the P side) to unite with holes that the electric fieldsent there, doing work for us along the way. The electron flow provides the current, and

the cell's electric field causes a voltage. With both current and voltage, we have power,

which is the product of the two.

(Information and graphs taken form www.howstuffworks.com)

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Operation of a PV cell

Silicon happens to be a very shiny material, which means that it is very reflective.

Photons that are reflected can't be used by the cell. For that reason, an antireflectivecoating is applied to the top of the cell to reduce reflection losses to less than 5 percent.

The final step is the glass cover plate that protects the cell from the elements. PV

modules are made by connecting several cells (usually 36) in series and parallel to

achieve useful levels of voltage and current, and putting them in a sturdy frame completewith a glass cover and positive and negative terminals on the back.

Unfortunately, the most that a simple cell could absorb is around 25 percent, and more

likely is 15 percent or less.

Basic structure of a generic silicon PV cell

7

(Information and graphs taken form www.howstuffworks.com)



Mean Daily Sunshine in Ireland

(Graph taken from the official met eireann website)

The sunniest months in Ireland would be the summer months especially May and June.

At this time of the year the amount of sunshine averages between 5 to 6.5 hours per day

over a lot of the country. The South East of the country gets the most amount of sun andcan get up to 7 hours a day in early summer.

The dullest month of the year would be December. At this time of the year the amount of

sunshine is only about 1 hour and almost 2 hours in the south east..Over the space of the year the average amount of sun most areas receive is approximately

between 3 and four hours.

Ireland receives 1400 to 1700 hours of sunshine each year compared to the sahara desertwhich gets the most amount of sunshine and receives around 4300 hours a year.

The skies in Ireland are completely covered in cloud for at least fifty percent of the yeardue to where the country is situated in the northwest of Europe.

8



Some questions that are asked regularly

Will solar work in Ireland?

• Yes, The average amount of power you would get from solar panels each daywould be about the same as you would get from other countries in Northern-

Europe. This would mean that Ireland is just as good for solar as Germany and

Austria which would be classed as the 2 largest markets for solar in Europe.

Do Solar Panels work just as well in the winter?

• The principle of a solar panel is to work on light not heat, therefore yes it wouldwork just as well in winter but what you would have to take into consideration is

the fact that there are less hours of light in the winter therefore you power wouldbe reduced proportionally.

Can I connect equipment directly yo the solar panel?

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• Yes. You can hook up your solar panels directly to equipment given that the loadis accounted for correctly. You can connect up stuff like fans and pumps. If the

load needed by the equipment is greater then the output the efficiency of theequipment will reduce greatly so you would be better off using a battery and

inverter.



Trajectory of the sun

(Pictures taken from www.pinyondesign.com)

The different seasons are caused because of the fact that the rotation of the Earths axis isnot perpendicular to the plain of its trajectory around the sun. This angle varies

depending on what time of the year it is.

There are only 2 days in the year when the axis of the earth is exactly perpendicular to its

rotation around the sun. They are March 22nd and September 21st. These are the only 2

days where there is exactly 12 hours of light and 12 hours of darkness.

After March 21st the days start to get longer as the sun and the sun sits higher in the sky at

noon. These day lengths keep increasing until June 21st Which is the longest day of the

year. After this they keep decreasing until it reaches December 21st

which would be theshortest day of the year. At this time of the year the sun sits a lot lower in the sky as can

be seen from the diagram above.

When building a Solar power system you have to take all of this into consideration when

mounting the panel.

10



Solar Trackers

A number of panels can be set up into groups called arrays. This arrays are used a lot on

buildings.On stand alone systems you can fit what’s called a solar tracker. They greatly increases

the amount of power which you can receive from the sun to almost double as can be seen

from the graph below. The tracker uses motors to track the sun through the sky from

when it rises to when it sets.

Figure 3 Graph showing power output for tracked and non-tracked array.

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This graph can be used to determine the angle at which a solar

panel will be perpendicular to the sun at mid-day at anylatitude.

12



The system

The system I built consisted of:

• 18W Solar Panel : Height 638mm, Width 278mm, 36 x 0.5 Watt cells, cost 200

euro

• Charge Controller : Included with system purchased, 4 Amp controller

• Battery: Yuasa 12V 4Ah

• Inverter: 600 Watt 12dc to 230v ac

• Light Bulb: 60 Watt Incandescent

After purchasing the system I wired it up as shown below:

As you can see the solar panel feeds the charge controller. The charge controller thencontrols and regulates the charging of the batteries from the panel. The charge controller

is connected to the batteries via a fuse. From the batteries the inverter takes the charge

and converts the 12 volt dc to 230 volt ac. From the inverter I was then able to carry out a

number of different tests to check various aspects of the panel.

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Tests Carried Out

Test 1

This test was carried out at home. It was a bright sunny day. The panel was placed on topof a garden shed at approximately 45 degrees to the sun. It was carried out over a nine

hour period to verify that the solar panel was functioning correctly and to see at whattime of the day was the most power being produced from the panel.

14



Test 1

Weather Reports taken from Cork Airport for 15-03-2009

Date Rainfall

(mm) Max

Temp Min

Temp Sunshine

(hours) Gusts Windspeed gmin

15/3/2009 11.5 11.6 3 5 29 11.0 -0.4

Readings Taken for 15-03-2009

Weather

Conditions

Time Voltage

( Volts )

Current

( Amps )

Power

(Watts)

Clear

sunny

09:00 14.91 0.54 8.05

Clear

sunny

10:00 14.98 0.57 8.53

Clear

sunny

11:00 15.23 0.68 10.35

Clear

sunny

12:00 15.92 0.91 14.48

Clear

sunny

13:00 15.98 1.11 17.37

Clear

sunny

14:00 15.52 1.05 16.29

Clear

Dull

15:00 14.70 0.90 13.23

Dull

Overcast

16:00 14.51 0.82 11.89

DullOvercast

17:00 13.09 0.63 8.24

Dusk

Dull

18:00 12.89 0.59 7.60

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Result Graphs for Test 1

0

2

4

6

8

10

12

14

16

Voltage (Volts)

9:00 11:00 13:00 15:00 17:00

Time (hours)

Voltage Test

voltage

0

0.2

0.4

0.6

0.8

1

1.2

Current (Amps)

9:00 11:00 13:00 15:00 17:00Time (hours)

Current Test

Current

0

2

4

68

10

12

14

16

18

Power (Watts)

9:00 11:00 13:00 15:00 17:00

Time (hours)

Resulting Power

Power

16



Test 2This test was carried out at home. It was a dull overcast day. The panel was placed on top

of a garden shed at approximately 45 degrees to the sun. It was carried out over a nine

hour period to verify that the solar panel was functioning correctly and to see at whattime of the day was the most power being produced from the panel.

17



Test 2


Date Rainfall

(mm)

Max

Temp

Min

Temp

Sunshine

(hours)

Gusts Windspeed gmin

17/3/2009 18.2 9.1 3.7 6 21 13.0 -0.3


Weather

Conditions

Time Voltage

( Volts )

Current

( Amps )

Power

(Watts)

Dull

Overcast

09:00 14.23 0.45 6.4

Dull

Overcast

10:00 14.82 0.49 7.26

Dull

Overcast

11:00 15.10 0.50 7.55

Dull

Overcast

12:00 15.01 0.82 12.3

Dull

Overcast

13:00 15.13 0.98 14.8

Dull

Overcast

14:00 15.05 1.0 15.05

Dull

Overcast

15:00 14.81 0.83 12.2

Dull

Overcast

16:00 14.12 0.72 10.16

Dull

Overcast

17:00 13.98 0.52 7.26

Dusk

Dull

18:00 12.21 0.46 5.61

18




0

2

4

6

8

10

12

14

16

Voltage (volts)

9:00 11:00 13:00 15:00 17:00

Time (hours)

voltage Test

volt age

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Current (Amps)

9:00 11: 00 13:00 15:00 17:00

Time (hours)

Current Test

current

19

0

2

4

6

8

10

12

14

16

Power (Watts)

9:00 11:00 13:00 15:00 17:00

Time (hours)

Resulting Power

Power



Test 3

This test was carried out in C.I.T over a two hour period. The panel was placed on the

ground facing south at an angle of approximately 45 degrees. From this test I was hoping

to verify Test 1 that the most power produced by the panel was between mid-day and

14:00 but the readings varied slightly due to weather conditions. Test 2

20




Date Rainfall

(mm) Max

Temp Min

Temp Sunshine


7/4/2009 13.7 9.7 2 2 36 14.3 -0.5


Time Voltage(Volts)

Current(Amps)

Power(Watts)

11:00 13.5 0.36 4.86

11:15 13.72 0.56 7.68

11:30 13.91 0.58 8.06

11:45 14.18 0.62 8.79

12:00 14.32 0.74 10.59

12:15 14.96 0.82 12.25

12:30 15.12 1.01 15.27

12:45 15.34 0.98 15.03

13:00 15.42 0.81 12.49

13:15 15.40 0.76 11.7

13:30 15.21 0.75 11.4

13:45 15.01 0.62 9.3

14:00 14.75 0.54 7.96

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12.5

13

13.5

14

14.5

15

15.5

Voltage (Volts)

1 1: 00 11 :3 0 1 2: 00 12 :3 0 1 3: 00 1 3: 30 14 :0 0

Time (15 mins)

voltage Test

voltage

0

0.2

0.4

0.6

0.8

1

1.2

Current (Amps)

11:00 11:30 12:00 12:30 13:00 13:30 14:00

Time (15 mins)

Current Test

Current

0

2

4

6

8

10

12

14

16

Power (Watts)

11: 00 11: 30 12: 00 12: 30 13: 00 13: 30 14: 00

Time (15 mins)

Resulting Power

Power

22



Test 4

This time I was testing to see how long it would take to charge a 12V 4Ah battery.

I first drained the battery using a light bulb which was connected up to the inverter,

The inverter has a setting on it that when the battery drops below 12V it cuts out sotherefore I started the charge form 12V.

I then started to charge the battery using the panel. I charged it over a period of fourhours. Over the last hour the voltage readings started to level off which meant that thebattery was reaching its fully charged state.

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Test 4


Date Rainfall

(mm) Max

Temp Min

Temp Sunshine


21/4/2009 0 14.2 5.0 7.2 0 3.9 1.4


Time Voltage

09:00 10.1

09:30 11.5

10:00 12.1

10:30 12.32

11:00 12.45

11:30 12.7

12:00 12.91

12:30 13.03

13:00 13.05

13:30 13.07

14:00 13.08

24



Resulting Graph for Charge Test

12V 4Ah Battery Charging

0

2

4

6

8

10

12

14

9:00

9:30

10:00

10:30

11:00

11:30

12:00

12:30

13:00

13:30

14:00

Time (hours)

Voltage (

Volts)

Voltage

25



Test 5

This test was carried out to see how many panels you would need to power a

children’s playroom.

The only thing which requires power in the playroom is the light.

So I had to figure out going by my tests how many panels I would need to keep a

bulb powered in the playroom. The average bulb used would be a 100Watt bulb.

Results for Test 5

• The average power for dull day is 9.85 Watts

• The average power for a bright sunny day is 11.6 Watts

• Therefore average power from the panels is 10.72 Watts

(These results vary throughout the year depending on light hours during the day.)

However,

A 100Watt bulb draws approximately 0.43 AmpsTherefore using a 4Ah battery you would only be able to power the light for 9.3hrs

approx.

26



Incandescent bulb versus CFL Bulb

Bulb Type Watts Current Time(4Ah

Battery)

Lumen Cost perunit

Incandescent

100W 0.43 9.3hrs 1380 €1.50

CFL

28W 0.12 33.3hrs 1750 €9.50

LED

3W 0.013 307.6hrs 140 €21.30

• From the table above you can see that even though the Incandescent bulb drawsmore current the CFL bulb actually gives out more light.

• The LED only gives out 140 lumens of light therefore to match that of the CFL

bulb you will require 13 led lights. (13 x 140 = 1820lumens)

• Therefore 13 lights mean’s you are drawing 0.169Amps. This is roughly equal to

that of the current drawn by a CFL bulb.

27

• To conclude depending on what application you need decides whether to use agroup of LED’s or a CFL bulb. These 2 types are a lot more efficient then an

Incandescent bulb.



Practical Applications

Lights along a Path

• Each Light draws 0.013A

• Therefore 8 Lights would draw (8 x 0.013 Amps = 0.104Amps)

• The average time for the lights to be on would be 10 hrs (12hrs in winter, 8

hours in summer).

28

• On average they would use 1.04Ah from the battery, this could be easily

topped up by the solar panel the next day giving you continuous power to the

lights.



Electric Gates

The motor used to open and close the gates draws approximately 4 amps from the batterysource

Because the gate only takes approximately 10 to fifteen seconds to open and close it

would only be drawing that amount of current for a short period of time.

To open and close the gates onse you would draw approximately 8.3 % of the batteries

power, given that you open and close the gates 3 to 4 times a day you would only beusing 33.2 percent of the batteries total power which could easily be charged by the panel

the next day.

29

http://images.google.ie/imgres?imgurl=http://www.sussexirongates.co.uk/automatic_gates_1.jpg&imgrefurl=http://www.sussexirongates.co.uk/automatic_gates.html&usg=__xXtKl1q2gUHZ0aPujfpRMByZa6I=&h=450&w=600&sz=104&hl=en&start=1&um=1&tbnid=adh4iteq7lgpoM:&tbnh=101&tbnw=135&prev=/images%3Fq%3Delectric%2Bgates%26hl%3Den%26um%3D1



Opportunities for further testing

Angle of Panel

• The angle the panel is a crucial test but time restricted me to a small number of tests. The panel should be tested for power at a number of different anglesthrough out the day to compare the different effects the angle and position has on

the power output.

Grouping of Panels

• Another type of test that could be carried out is to group a number of panels

together and carry out power tests on each individual panel and then on the group

of panels as a whole unit.

Solar Tracker

30

• Another test would be to attach the panel to a solar tracker and compare theresults from a normal panel and a panel mounted on a tracker. You would then be

able to see the advantages of the tracker and see if it would be feasible to mount

it.



Bibliography

On building this system I acquired a lot of information from a number of different

resources.

Here is an Example of a few:

InternetI got a lot of information from a number of different sites and found the internet most

helpful.

www.howstuffworks.com

www.meteireann.ie

www.sei.iewww.solarsolutions.com

www.wikipedia.com

BooksI got some information from a number of books here is a list of a few.

Progress in Photovoltaic

Solar Energy seeing the light

Wind and Solar Power Systems

LecturersI could not have done it but for the help of the lecturers who helped me whin I had a

problem to figure out a solution.

Dr. P. O’Connor

Liam Carroll

http://www.howstuffworks.com/

http://www.meteireann.ie/

http://www.sei.ie/

http://www.solarsolutions.com/

http://www.solarsolutions.com/

http://www.sei.ie/

http://www.meteireann.ie/

http://www.howstuffworks.com/

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BASIC SOLAR POWER SYSTEM