Lectures on Solar Electricity By Engr Tanveer ul Haq

Engr. Tanveer ul HaqChairman PEN Community

MS Electronics Scholar in GIKI

B.Sc Electrical Engg. From UCE&T BZU

Lecture 01:- Energy From Sun

Lecture 02:- Introduction to Solar Cells

Lecture 03:- Electronic Structure of Semiconductor

Lecture 04:- How solar cells work?

Lecture 05:- Typical Device Structure

Lecture 06:- Losses in Solar Cell

Lecture 07:- Silicon Solar Cell Technology

Lecture 08:- Typical Cell Fabrication Process

Lecture 09:- Structure of a Photovoltaic System

Lecture 10:- Photovoltaic Engineering

Lecture 11:- Power Conditioning and Control

Lecture 12:- Sizing of Photovoltaic System

Lecture 13:- Concentrating Photovoltaic

Bibliography And References

Lecture 01

Engr. Tanveer-ul-Haq

Energy From Sun

Contents

Solar Power

Solar Constant

Irradiance

Aerosols

Solar Radiation in Atmosphere

Air Mass

Solar Spectrum

7/22/2012 2Engr. Tanveer-ul-Haq

Solar Power

The luminosity of the Sun is about 3.86x10^26watts. This is the total power radiated out intospace by the Sun. Most of this radiation is in thevisible and infrared part of the electromagneticspectrum, with less than 1 % emitted in the radio,UV and X-ray spectral bands.


Solar Power

The sun’s energy is radiated uniformly in alldirections. Because the Sun is about 150 millionkilometers from the Earth, and because the Earthis about 6300 km in radius, only 0.000000045% ofthis power is intercepted by our planet. This stillamounts to a massive 1.75x10^17 watts.


Solar Constant

For the purposes of solar energy capture, wenormally talk about the amount of power insunlight passing through a single square meterface-on to the sun, at the Earth's distance fromthe Sun. The power of the sun at the earth, persquare meter is called the solar constant and isapproximately 1370 watts per square meter(W/m^2).


IrradianceThe total power from a radiant source falling on a

unit area is called Irradiance.

When the solar radiation enters the Earth’satmosphere, a part of the incident energy isremoved by scattering or absorption by airmolecules, clouds and particulate matter usuallyreferred to as aerosols.

Aerosols


Solar Radiation in Atmosphere

• Direct or Beam Raidiation

• Diffuse Radiation

• Albedo

• Global


Direct or Beam Radiation

The radiation that is notreflected or scattered andreaches the surface directlyin line from the solar disc iscalled direct or beamradiation.


Diffuse RadiationThe scattered radiation which reaches the ground is

called diffuse radiation.


AlbedoSome of the radiation may reach a receiver after

reflection from the ground is called Albedo.


GlobalThe total radiation consisting of these three (Direct,

Diffuse & Albedo) components is called global.


Air Mass

A concept which characterises the effect of a clearatmosphere on sunlight is the air mass, equal tothe relative length of the direct beam paththrough the atmosphere. One clear summer dayat sea level, the radiation from the sun at zenithcorresponds to air mass 1(abbreviated to AM1);at other times, the air mass is approximatelyequal to 1/cosθz, Where θz is zenith angle.




Solar SpectrumThe extraterrestrial spectrum, denoted by AM 0, is important for satellite

application of solar cell. AM 1.5 is a typical solar spectrum on the Earth’ssurface on a clear day which, with total irradiance of 1KW/m2, is used forthe calibration of solar cells and modules.


7/22/2012 Engr. Tanveer-ul-Haq 16

Introduction to

Solar Cells

Lecture 02


What are Solar Cells?

Solar cells represent the fundamental power

conversion unit of a photovoltaic system.

They are made from semiconductors, and

have much in common with other solid-state

electronic devices, such as diodes,

transistors and integrated circuits. For

practical operation, solar cells are usually

assembled into modules.


Different type of solar cells

• Monocrystalline Solar Cell

• Polycrystalline Solar Cell

• Amorphous Solar Cell


Crystalline Solar Cell

Crystalline silicon hold the largest part of the

market. To reduce the cost, these cells are

now often made from multicrystalline

material, rather than from the more expensive

single crystal. Crystalline silicon cell

technology is well established. The modules

have a long life (20 years or more) and their

best production efficiency is approaching

18%.


Monocrystalline Solar Cell


• Monocrystalline silicon is the most efficient

• Works in low light condition

• Absorbs 18% of available sun light

• Most expensive type of solar cell

Polycrystalline Solar Cell

• Most affordable in the market today

• Made of small silicon crystal mashed together

• It is durable and can be used for moderate

purposes

• Absorbs 15% of sun light available to it


Amorphous Solar Cells

Amorphous technology is most often seen in

small solar panels, such as those in

calculators or garden lamps, although

amorphous panels are increasingly used in

larger applications. They are made by

depositing a thin film of silicon onto a sheet of

another material such as steel. The panel is

formed as one piece and the individual cells

are not as visible as in other types.



The efficiency of amorphous solar panels is not as

high as those made from individual solar cells,

although this has improved over recent years to

the point where they can be seen as a practical

alternative to panels made with crystalline cells.

Their great advantage lies in their relatively low

cost per Watt of power generated. This can be

offset, however, by their lower power density;

more panels are needed for the same power

output and therefore more space is taken up.



• Cheapest and lightest

• Absorbs 10% of light available

• Used for vehicles like boats

• Work best in intense sun light


Some Other Types of Solar Cells

A variety of compound semiconductors can

also be used to manufacture thin-film cells (

for example, cadmium telluride or copper

indium diselenide). These modules are now

beginning to appear on the market and hold

the promise of combining low cost with

acceptable conversion efficiencies.


Some Other Types of Solar Cells

A particular class of high-efficiency solar cells

from single crystal silicon or compound

semiconductors (for example, gallium

arsenide or indium phosphide) are used in

specialised applications, such as to power

satellites or in systems which operate high-

intensity concentrated sunlight.


How Solar Cell Works

The solar cell operation is based on the ability

of semiconductors to convert sunlight directly

into electricity by exploiting the photovoltaic

effect. In the conversion process, the incident

energy of light creates mobile charged

particles in the semiconductor which are

separated by the device structure and

produce electric current.



Electronic

Structure of

Semiconductor

Lecture 03


Semiconductor Physics

The principle of semiconductor physics are

best illustrated by the example of silicon,

a group 4 elemental semiconductor. The

silicon crystal forms the so-called

diamond lattice where each atom has four

nearest neighbours at the vertices of a

tetrahedron. The four fold tetrahedral

coordination is the result of the bounding

arrangement which uses the four outer

electron of each silicon atom.

This crystal structure has a profound effect on

the electronic and optical properties of the

semiconductor.

According to the quantum theory, the

energy of an electron in the crystal

must fall within well defined bonds. The

energies of valence orbitals which form

bonds between the atom represent just

such a band of states, the valance

band. The next higher band is the

conduction band which is separated

from the valence band by the energy

gap or bandgap.

Band Structure

The width of the bandgap Ec - Ev is a very

important characteristic of the

semiconductor and is usually denoted by

Eg. This table gives the bandgaps of the

most important semiconductors for solar-

cell applications.

Material Energy gap (eV) Type of gap

crystalline Si 1.12 indirect

amorphous Si 1.75 direct

CuInSe2 1.05 direct

CdTe 1.45 direct

GaAs 1.42 direct

InP 1.34 direct

Doping

A pure semiconductor (which is called

intrinsic) contains just the right number

of electrons to fill the valence band, and

the conduction band is therefore empty.

Electrons in the full valence band

cannot move - just as, for example,

marbles in a full box with a lid on top.

For practical purposes, a pure

semiconductor is therefore an insulator.

Semiconductors can only conduct electricity

if carriers are introduced into the

conduction band or removed from the

valence band. One way of doing this is by

alloying the semiconductor with an

impurity. This process is called doping. As

we shall see, doping makes it possible to

exert a great deal of control over the

electronic properties of a semiconductor,

and lies in the heart of the manufacturing

process of all semiconductor devices.

Suppose that some group 5 impurity atoms

(for example, phosphorus) are added to the

silicon melt from which the crystal is grown.

Four of the five outer electrons are used to

fill the valence band and the one extra

electron from each impurity atom is

therefore promoted to the conduction band.

For this reason, these impurity atoms are

called donors. The electrons in the

conduction band are mobile, and the crystal

becomes a conductor. Since the current is

carried by negatively charged electrons,

this type of semiconductor is called n type.

A similar situation occurs when silicon is

doped with group 3 impurity atoms (for

example, boron) which are called

acceptors. Since four electrons per atoms

are needed to fill the valence band

completely, this doping creates electron

deficiency in this band. The missing

electrons - called holes - behave as

positively charged particles which are

mobile, and carry current. A semiconductor

where the electric current is carried

predominantly by holes is called p-type.

Semiconductor junctions

The operation of solar cells is based on the

formation of a junction. The important

feature of all junctions is that they contain

a strong electric field. To illustrate how

this field comes about, let us imagine the

hypothetical situation where the p-n

junction is formed by joining together two

pieces of semiconductor, one p-type and

the other n-type.

In separation, there is electron surplus in

the n-type material and hole surplus in

the p-type. When the two pieces are

brought into contact, electrons from the n

region near the interface diffuse into the

p side, leaving behind a layer which is

positively charged by the donors.

Similarly, holes diffuse in the opposite

direction, leaving behind a negatively

charged layer stripped of holes.

The resulting junction region then contains

practically no mobile charge carriers, and

the fixed charges of the dopant atoms

create a potential barrier acting against a

further flow of electrons and holes.

The potential barrier of a junction permits

the flow of electric current in only one

direction - the junction acts as a rectifier,

or diode. This can be seen in our example

where electrons can only flow from the p

region to the n region, and holes can only

flow in the opposite direction. Electric

current, which is the sum of the two, can

therefore flow only from the p-side to the

n-side of the junction (remember that it is

defined as the direction of flow of the

positive carriers!).

I-V characteristic of a diode

Light absorption by a

semiconductor

Photovoltaic energy conversion relies on

the quantum nature of light whereby we

perceive light as a flux of particles called

photons. On a clear day, about 4.4 x 1017

photons strike a square centimentre of

the Earth's surface every second.

Only some of these photons - those with

energy in excess of the bandgap - can be

converted into electricity by the solar cell.

When such photon enters the

semiconductor, it may be absorbed and

promote an electron from the valence to

the conduction band. Since a hole is left

behind in the valence band, the absorption

process generates electron-hole pairs.

Each semiconductor is restricted to

converting only a part of the solar

spectrum. The spectrum is plotted

here in terms of the incident photon

flux as a function of photon energy.

The shaded area represents the

photon flux that can be converted by

a silicon cell - about two-thirds of the

total flux.

The nature of the absorption process also

indicates how a part of the incident

photon energy is lost in the event. Indeed,

it is seen that practically all the generated

electron-hole pairs have energy in excess

of the bandgap. Immediately after their

creation, the electron and hole decay to

states near the edges of their respective

bands. The excess energy is lost as heat

and cannot be converted into useful

power. This represents one of the

fundamental loss mechanisms in a solar

cell.

How solar cells work?

Lecture 04

Engr. Tanveer ul Haq

This diagram shows a typical crystalline silicon

solar cell. The electrical current generated in

the semiconductor is extracted by contacts to

the front and rear of the cell. The top contact

structure which must allow light to pass

through is made in the form of widely-spaced

thin metal strips (usually called fingers) that

supply current to a larger bus bar. The cell is

covered with a thin layer of dielectric material

- the anti-reflection coating, ARC - to

minimize light reflection from the top surface.

Current in p-n junction under illumination

• This diagram shows a typical silicon solar cell

• Note the two possible electron energy bands:

LOW (black)- known as the valance band

HIGH (white)- known as the conduction band

When light falls on the solar cell, energy from the photons

generates electron-hole pairs on both sides of the p-n

junction.

• Electrons diffuse across the p-n junction to a lower

energy level.

• Holes diffuse in the opposite direction

• New electron-hole pairs continue to be formed while light

falls on the solar cell.

• As electrons continue to diffuse, a negative charge

builds up in the emitter.

• A corresponding positive charge builds up in the base.

• The p-n junction has separated the electrons from the

holes and transformed the generation current between

the bands into an electric current across the p-n junction.

• If an electrical circuit is made between the emitter and

base, a current will flow.

• The current continues to flow while the solar cell is

illuminated.

Solar cells are essentially semiconductor junctions under

illumination. Light generates electron-hole pairs on both

sides of the junction, in the n-type emitter and in the p-

type base. The generated electrons (from the base) and

holes (from the emitter) then diffuse to the junction and

are swept away by the electric field, thus producing

electric current across the device. Note how the electric

currents of the electrons and holes reinforce each other

since these particles carry opposite charges. The p-n

junction therefore separates the carriers with opposite

charge, and transforms the generation current between

the bands into an electric current across the p-n junction.

A more detailed consideration makes it possible to draw an

equivalent circuit of a solar cell in terms of a current

generator and a diode. This equivalent circuit has a

current-voltage relationship.

• In solar cell applications this characteristic is

usually drawn inverted about the voltage axis,

as shown below. The cell generates no

power in short-circuit (when current Isc is

produced) or open-circuit (when cell

generates voltage Voc). The cell delivers

maximum power Pmax when operating at a

point on the characteristic where the product

IV is maximum. This is shown graphically

below where the position of the maximum

power point represents the largest area of the

rectangle shown.

Efficiency of Solar Cell

The efficiency (n) of a solar cell is defined as the power

Pmax supplied by the cell at the maximum power point

under standard test conditions, divided by the power of

the radiation incident upon it. Most frequent conditions

are: irradiance 100 mW/cm2 , standard reference

spectrum, and temperature 25 0 C. The use of this

standard irradiance value is particularly convenient since

the cell efficiency in percent is then numerically equal to

the power output from the cell in mW/cm2.

Typical Device Structure

Lecture 05


High Efficiency Silicon Solar Cell

The passivated emitter solar cell has beendeveloped at the University of New South Walesin Australia for operation under ordinarysunlight. The point contact cell of StanfordUniversity USA, has been designed for optimumoperation under concentrated sunlight.

Gallium Arsenide Solar CellsThese are usually intended for operation on

satellite or in concentration systems.

The structure and band diagram of Gallium Arsenide Solar Cell

Amorphous Silicon Solar Cell

The structure of amorphous Silicon p-i-n Solar cell

Tandem Cell

Solar cells containing several p-n junctions arecalled Tandem Cell. Each junction is tuned to adifferent wavelength of light, reducing one ofthe largest inherent sources of losses, andthereby increasing efficiency.

The structure and spectral contribution of the tandem cell

Power Losses in Solar Cell

Fundamental Losses

Carrier generation in the semiconductor by lightinvolves considerable dissipation of thegenerated carrier energy into heat. In addition, aconsiderable part of the solar spectrum is notutilised because of the inability of asemiconductor to absorb the below-bandgaplight.

Can these losses be reduced?

Yes, but not with a simple structure that we have inmind at the moment. Such a device is called atandem cell and represents a stack of severalcells, each operating according to the principlesthat we have described. The top cell must bemade of a high bandgap semiconductor, andconverts the short-wavelength radiation. Thetransmitted light is then converted by thebottom cell. This arrangement increasesconsiderably the achievable efficiency.

Recombination

An opposite process to carrier generation isrecombination when an electron-hole pair isannihilated. Recombination is most common atimpurities or defects of the crystal structure, orat the surface of the semiconductor whereenergy levels may be introduced inside theenergy gap. These levels act as stepping stonesfor the electrons to fall back into the valanceband and recombine with holes as shown in nextfigure.

Defect-assisted recombination of

electron-hole pair

An important site of recombination are also theohmic metal contacts to the semiconductor.

What measure can one take to

minimise the recombination losses?

Surface recombination and recombination atcontacts which are considerable in theconventional silicon cell can be reduced byadapting the device structure of high efficiencysilicon cells. The external surfaces of thesemiconducter are here protected by a layer ofpassivating oxide to reduce surfacerecombination. The top layer of GaAlAs in theGaAs cell has similar purpose.

The contacts are surrounded by heavily-dopedregions acting as ‘minority-carrier mirrors’ whichimpede the minority carriers from reaching thecontacts and recombination. Recombinationreduces both the voltage and current output fromthe cell.

Collection Efficiency

The current losses can be grouped under the termof collection efficiency, the ratio between thenumber of carriers generated by light and thenumber that reaches the junction. Considerationof the collection efficiency affect the design ofthe solar cell. In crystalline materials, thetransport properties are usually good, andcarrier transport by simple diffusion issufficiently effective. In amorphous andpolycrystalline thin films, however, electric fieldsare needed to pull the carriers.

Other Losses

Other losses to the current produced by the cellarise from light reflection from the top surface,shading of the cell by the top contacts, andincomplete absorption of light.

Losses in Solar Cell

Lecture 06


Fill Factor

The short-circuit current and the open-circuit voltageare the maximum current and voltage respectivelyfrom a solar cell. However, at both of theseoperating points, the power from the solar cell iszero. The "fill factor", more commonly known by itsabbreviation "FF", is a parameter which, inconjunction with Voc and Isc, determines themaximum power from a solar cell. The FF is definedas the ratio of the maximum power from the solarcell to the product of Voc and Isc.

Graphically, the FF is a measure of the "squareness"of the solar cell and is also the area of the largestrectangle which will fit in the IV curve. The FF isillustrated below.

Series Resistance

The transmission of electric current producedby the solar cell involves ohmic losses. Thesecan be grouped together and included as aresistance in the equivalent circuit.

Series Resistance

It is seen that the series resistance affects the celloperation mainly by reducing the fill factor.

The power losses in Solar Cell

Temperature Effect

This has an important effect on the power outputfrom the cell. The most significant is thetemperature dependence of the voltage whichdecreases with increasing temperature (itstemperature coefficient is negative). The voltagedecreases of a silicon cell is typically 2.3mV per ˚C.The temperature variation of the current or the fillfactor are less pronounced and are usuallyneglected in the PV system design.

Temperature Effect

Temperature dependence of I-V characteristic of solar cell

Irradiance Effect

The light generated current is proportional to theflux of photons with above bandgap energy.Increasing the irradiance increases, in the sameproportion, the photon flux which, in turn,generates a proportionately higher current.Therefore, the short circuit current of a solar cell isdirectly proportional to the irradiance. The voltagevariation is much smaller (it dependslogarithmically on the irradiance), and is usuallyneglected in practical application.

Irradiance Effect

Irradiance dependence of the I-V characteristic of a solar cell

Summery

The solar cell is a semiconductor device that convertsthe quantum flux of photons into electric current.When light is absorbed, it first creates electron-holepairs. These mobile charges are then separated bythe electric fields at the junction. The electricaloutput from the cell is described by the I-Vcharacteristic whose parameters can be linked tothe material properties of the semiconductor.

Summery

Various solar-cell structures have been discussed inrelation to the principal power losses in a solarcell. In addition to the fundamental lossesassociated with light absorption, other losses,including recombination and losses dependent onthe structure of the device, have been analysed insome detail.

SILICON SOLAR CELL

TECHNOLOGY

Lecture 07


INTRODUCTION

The technology based on crystalline siliconis the most reliable and most developedphotovoltaic technology at the presenttime. It is not simple, however, andrequire the use of sophisticatedequipment and complex technologicalprocess. Four major stages need to befollowed to make photovoltaic modulesfrom sand

1. From sand to pure silicon

2. Growth of silicon crystals

3. From wafer to solar cell

4. From cell to module

FROM SAND TO PURE SILICON

GROWTH OF SILICON CRYSTALS

Silicon is first melted at 1400˚C. A small

silicon crystal properly cooled is used as a

seed to start the crystallization process.

As the seed is pulled out silicon solidifies

at the interface with the melt and, if the

pulling is slow enough, the silicon atoms

arrange themselves according to the

crystallographic structure of the seed.

This yields an ingot of single crystal

silicon.

THE BASICS OF CRYSTAL GROWTH

The degree of purity improves during the

growth process since impurities tend to

segregate towards the liquid phase. A

controlled amount of boron (or phosphorus)

is usually added to the melt to dope the

silicon p- or n-type.

METHODS OF GROWING SILICON CRYSTALS

There are various methods of growing silicon

crystals.

The one that resembles most closely the basic

description is the Czochralski method which is

also the most common in industrial use.

The second method is float zone process. The

purest silicon is obtained by this process.

CZOCHRALSKI METHOD

The cylindrical ingots aretypically 1 m long, 15 cmin diameter and 40 kg inweight. The growth rateis about 0.1-0.2 cm/min.To increase thethroughput, the cruciblecan be continuouslyreplenish with moltensilicon in some machines.Ingots up to 3.5 m longand 150 kg in weighthave been grown thisway.

CZOCHRALSKI METHOD

Another recent development is the use of

magnetic fields to reduce the interaction

between the molten silicon and the

crucible, thus reducing the usual carbon

and oxygen contamination from the latter.

The state of art for solar cells made from

CZ silicon is 18% efficiency for 100 cm²

industrial cell, and 19% efficiency for a 49

cm² laboratory cell with a laser-grooved

metal grid.

CZOCHRALSKI METHOD

CZOCHRALSKI METHOD

Even though the CZ process is commonly used

for commercial substrates, it has several

disadvantages for high efficiency laboratory or

niche market solar cells. CZ wafers contain a

large amount of oxygen in the silicon wafer.

Oxygen impurities reduce the minority carrier

lifetime in the solar cell, thus reducing the

voltage, current and efficiency. In addition, the

oxygen and complexes of the oxygen with other

elements may become active at higher

temperatures, making the wafers sensitive to

high temperature processing.

FLOAT ZONE METHOD

In this process, a molten

region is slowly passed

along a rod or bar of

silicon. Impurities in the

molten region tend stay in

the molten region rather

than be incorporated into

the solidified region, thus

allowing a very pure

single crystal region to be

left after the molten

region has passed.

Typical Cell Fabrication ProcessLecture 08


Typical Cell Fabrication Process

To transfer a silicon

wafer into a solar cell,

the wafer is subjected

to several chemical,

thermal and deposition

treatments. The cross

section of a silicon cell

shows the different

layers that need to be

formed.

Main steps of Fabrication Process

1. Surface texturing

2. p-n junction formation

3. Possible back P+ region formation

4. Front and back metal contacts

5. Antireflection layer deposition

Surface Texturing

Surface texturing, either in combination with an

anti-reflection coating or by itself, can also be

used to minimise reflection. Any "roughening" of

the surface reduces reflection by increasing the

chances of reflected light bouncing back onto

the surface, rather than out to the surrounding

air.

Surface Texturing

Surface texturing can be accomplished in a

number of ways. A single crystalline substrate

can be textured by etching along the faces of

the crystal planes. The crystalline structure of

silicon results in a surface made up of pyramids

if the surface is appropriately aligned with

respect to the internal atoms. One such

pyramid is illustrated in the drawing below.

Surface Texturing

An electron microscope photograph of a textured

silicon surface is shown in the photograph

below. This type of texturing is called "random

pyramid" texture, and is commonly used in

industry for single crystalline wafers.

Electron microscope photograph of a textured silicon surface.

Surface Texturing

Another type of surface texturing used is known

as "inverted pyramid" texturing. Using this

texturing scheme, the pyramids are etched

down into the silicon surface rather than

etched pointing upwards from the surface.

Electron microscope photograph of a textured silicon surface.

Surface Texturing

Multicrystalline wafers cannot be textured by

using either of the above methods. However,

multicrystalline wafers can be textured using a

photolithographic technique.

Electron microscope photograph of a textured multicrystalline silicon surface.

p-n junction formation

The wafers are usually p-type. The p-n junction is

then formed by thermal diffusion of n-type

impurity, usually phosphorus atoms diffuse into

silicon at a temperature of 900˚C or higher.

Figure shows a quartz diffusion furnace.

P+ region formation

Although it is not absolutely necessary and

might be considered irrelevant for low-

efficiency cell, a back P+ region may be

formed to improve the cell performance.

This feature creates a back surface field that

decreases the chances of carriers

recombining at the back surface. The easiest

way to form it is by depositing an aluminum

layer and alloying it at about 800˚C, or even

diffusing it at about 1000˚C.

Front and back metal contacts

Electrical contacts are usually formed by screen

printing. This technology is inexpensive, simple

and can be automated. The screen consists of a

mesh of wires imbedded in am emulsion. This

emulsion is photographically patterned and

removed from the places where metal is to be

deposited. A paste containing the metal is

squeezed through the screen onto the wafer.

Upon firing the organic solvents evaporate and

the metal powder becomes a conducting path

for the electric current.

Screen printing

Screen printing

Close up of a screen used for printing the front

contact of a solar cell. During printing, metal

paste is forced through the wire mesh in

unmasked areas. The size of the wire mesh

determines the minimum width of the fingers.

Finger widths are typically 100 to 200 µm.

Screen printing

Close up of a finished screen-printed solar cell.

The fingers have a spacing of approximately 3

mm. An extra metal contact strip is soldered to

the bus bar during encapsulation to lower the

cell series resistance.

Screen printing

Front view of a completed screen-printed solar

cell. As the cell is manufactured from a

multicrystalline substrate, the different grain

orientations can be clearly seen. The square

shape of a multicrystalline substrate simplifies

the packing of cells into a module.

Screen printing

Rear view of a finished screen-printed solar cell.

The cell can either have a grid from a single

print of Al/Ag paste with no back surface

field(BSF), or a coverage of aluminium that gives

a BSF but requires a second print for solderable

contacts.

Antireflection layer deposition

A thin layer of a transparent material which acts

as antireflection coating can be deposited

before or after the formation of the metal

contacts. This dielectric material has an

optimum value of refractive index between

those of silicon and glass. An antireflection of

silicon nitride is typically deposited using

chemical vapour deposition process (CVD).

Older cell designs use titanium dioxide (TiO2),

which provides a good antireflection coating

and is simpler to apply but does not provide

surface or bulk passivation.

Antireflection layer deposition

Wafers being deposited with silicon nitride

antireflection coating giving a blue color.

Lecture 09


The photovoltaic system consists of a number of partsor subsystem.

a. The photovoltaic generator with mechanicalsupport and possibly a sun tracking system.

b. Batteries (storage subsystem).

c. Power conditioning and control equipment,including provision for measurement andmonitoring.

d. Back up generator.

The choice of how and which of these components areintegrated into the system is governed by variousconsiderations.

There are two main categories of systems,

1. Grid connected

2. Stand alone

It consists simply of a photovoltaic generator alonewhich supplies DC power to a load whenever there isadequate illumination. This type of system iscommon in pumping applications. In other instances,the system will usually contain a provision for energystorage by batteries. Some form of powerconditioning is then frequently also included, as isthe case when AC current is required at the outputfrom the system. In some situation, the systemcontains a back-up generator.

Grid connected systems can be subdivided into thosein which the grid merely acts as an auxiliary supply(grid back-up) and those in which it may also receiveexcess power from the PV generator (gridinteractive). In PV power stations, all the generatedpower is fed into the gird.

Grid-Interactive systems use the light available fromthe sun to generate electricity and feed this into themain electricity grid. If at a particular moment intime more power is being produced than is requiredin the house, the extra power is sent back onto thegrid to be used by neighbouring households. At nightor when there is insufficient power being producedto supply the households needs, electricity is drawnfrom the grid in the same manner other householdsdo.

The heart of the system is the photovoltaic generator.It consists of photovoltaic modules which areinterconnected to form a DC power-producing unit.The physical assembly of modules with supports isusually called an array.

Most frequently, the cells in a module areinterconnected in series. The reason comes from theelectrical characteristics of an individual solar cell. Atypical 4-inch diameter crystalline silicon solar cell, ora 10cm×10cm multicrystalline cell, will providebetween 1 and 1.5 watts under standard conditions,depending on the cell efficiency. This power isusually supplied at a voltage 0.5 to 0.6 V. Since thereare very few appliance that work at this voltage, theimmediate solution is to connect the solar cell inseries.

The number of cells in a module is governed by thevoltage of the module. The nominal operatingvoltage of the system usually has to be matched tothe nominal voltage of the storage subsystem. Mostof photovoltaic module manufacturers thereforehave standard configurations which can work with 12volt batteries. Allowing for some overvoltage tocharge the battery and to compensate for loweroutput under less-than perfect conditions, it is foundthat a set of 33 to 36 solar cells in series usuallyensures reliable operation.

The power of silicon modules thus usually fallsbetween 40 and 60 W. The module parameters arespecified by the manufacturer under the followingstandard conditions:

Irradiance 1kW/m²

Spectral distribution AM 1.5

Cell Temperature 25˚C

Indeed, they are the same conditions as are used tocharacterise solar cells. The nominal output is usuallycalled the peak power of a module and expressed inpeak watts, W.

The three important electrical characteristics of amodule are the short-circuit current, open circuitvoltage and the maximum power point as functionsof the temperature and irradiance.

The temperature and irradiance dependence of the module I-V characteristic

Temperature is an important parameter of a PVsystem operation. The temperature coefficient forthe open circuit voltage is approximately equal to-2.3mV/˚C for an individual cell. The voltagecoefficient of a module is therefore negative andvery large since 33 to 36 cells are connected inseries. The current coefficient on the other hand, ispositive and small, about +6μA/˚C for a squarecentimeter of the module area.

Accordingly only the voltage variation with temperatureis allowed for in practical calculation, and for anindividual module consisting of nc cells connected inseries in set equal to:

dVoc/dT= -2.3×nc mV/˚C

It is important to note that the voltage is determined bythe operating temperature of the cells which differsfrom the ambient temperature.

As for a single cell, the short circuit current Isc of amodule is proportional to the irradiance, and willtherefore vary during the day in the same manner.Since the voltage is a logarithmic function of thecurrent, it will also depend logarithmically on theirradiance. During the day, the voltage will thereforevary less than the current. In the design of the PVgenerator, it is customary to neglect the voltagevariation and to set the short circuit currentproportional to irradiance:

Isc(G)=Isc(at1kW/m²)×G(in kW/m²)

The operation of the module should lie as close aspossible to the maximum power point. It is asignificant feature of the module characteristic thatthe voltage of the maximum power point, Vm, isroughly independent of irradiance. The averagevalue of this voltage during the day can be estimatedas 80% of the open-circuit voltage under standardirradiance conditions. This property is useful for thedesign of the power conditioning equipment.

The characterisation of the PV module is completed bymeasuring the Normal Operating Cell Temperature(NOCT) defined as the cell temperature when themodule operates under the following conditions atopen circuit:

Irradiance 0.8 kW/m²

Spectral distribution AM 1.5

Cell Temperature 20˚C

Wind speed > 1m/s

NOCT (usually between 42˚C and 46˚C) is then used todetermine the solar cell temperature Tc during moduleoperation. It is usually assumed that the differencebetween Tc and the ambient temperature Ta dependslinearly on the irradiance G in the following manner:

Tc-Ta= (NOTC-20)G(kW/m²) /0.8

Determine the parameters of a module formed by 34solar cells in series, under the operating conditionsG=700 W/m² and Ta=34˚C. The manufacturer’s valuesunder standard conditions are: Isc=3A; Voc=20.4;Pmax=45.9 W; NOCT=43˚C.

1. Short circuit current

Isc(G)=Isc(at1kW/m²)×G(in kW/m²)=3×0.7=2.1A

2. Solar Cell temperature

Tc-Ta= (NOTC-20)G(kW/m²) /0.8

Tc=Ta+ (NOTC-20)G(kW/m²) /0.8

=34+(43-20)0.7/0.8=54.12˚C

3. Open circuit voltage

dVoc/dT= -2.3×nc mV/˚C

Voc(54.21)=20.4-0.0023×34×(54.12-25)=18.1

4. We shall now determine the maximum power point using the simplifying assumption that the fill factor is independent of the temperature and the irradiance:

FF=45.9/3×20.4=0.75

Pmax(G,Tc)=2.1×18.1×0.75=28.5W

Thus, noting the manufacturer’s value of Pmax we see that the module will operate at about 62% of its nominal rating.

Lecture 10Engr. Tanveer ul Haq

A schematic diagram of a PV generator consisting ofseveral modules is shown. In addition tophotovoltaic modules, the generator contains by-pass and blocking diodes.

The module are connected in series to form strings,where the number of modules Ns is determinedby the selected DC bus voltage, and the numberof parallel strings Np is given by the currentrequired from the generator.

Analysis assume that all the modules are identical.In practice, the module are not identical, andtheir parameters exhibit a certain degree ofvariability for two reasons:

1. The solar cells and modules vary in quality as aresult of the manufacturing process. In general,the current produced by commercial modulessuffers a high degree of dispersion than thevoltage.

2. Different operating conditions may exist indifferent part of the PV array. For example onemust allow for different cleanness of differentparts of the PV generator, or some modules maybe obscured by a cloud which is covering only apart of the array.

This variability of component parameters hastwo important effects:

Firstly, the output power of the generator is lessthan the sum of values corresponding to allthe constituent modules. This gives rise tomismatch losses. These losses can beminimised by forming series strings frommodules with similar values of short-circuitcurrent.

Secondly, there is a potential for overheating the‘poorest’ cell of a series string. In somecircumstances, a cell can operate as ‘load’ forother cells acting as ‘generators’. Consequently,this cell dissipate energy and its temperatureincreases. If the cell temperature rises above acertain limit(85-100˚C) the encapsulating materialscan be damaged, and this will degrade theperformance of the entire module. This is calledhot spot formation.

This effect is illustrated in figure, which shows a cell ina string which does not produce current, this canhappen, for example, when the cell is shaded. Theshading of one cell converting it into a diode underreverse bias– therefore eliminate the currentproduced by the entire string.

Furthermore, the shaded cell will dissipate allthe power produced by the illuminated cellsin the string which can be considerable if thestring is large. The common technique used toalleviate this effect is to employ by-passdiodes which are connected across a block ofseveral cell in a string. This limits the powerwhich is dissipated in this block and providesa low-resistance path for the module current.

An important problem that confronts the designerof an array is whether the modules are to bemounted at fixed positions, or their orientationswill follow the motion of the sun.

In most arrays, the modules are supported at afixed inclination facing the equator. This has thevirtue of simplicity, no moving parts and low cast.The optimum angle of inclination dependsmainly on the latitude, the proportion of diffuseradiation at the site and the load profile.

By mounting the array on a two-axis tracker, up to 40%more of the solar energy can be collected over theyear as compared with a fixed-tilt installation. But thisincreases complexity and result in lower reliability andhigher maintenance costs. Single axis tracking is lesscomplex but yields a smaller gain. Where labour isavailable, the orientation may be manually adjusted toincrease the output. It has been estimated that, insunny climates, a flat plate array moved to face thesun twice a day and given a quarterly tilt adjustmentcan intercept nearly 95% of the energy collected with afully automatic two-axis tracking.

Tracking is particularly important in systems which operateunder concentrated sunlight. The structure of thesesystems ranges from a simple design bases on sidebooster mirrors, to concentration systems which employsophisticated optical techniques to increase the lightinput to the cell by several orders of magnitude. Thesesystems must make allowance for an important fact thatconcentrating the sunlight reduces the angular range ofrays that the system can accept for conversion. Trackingbecomes necessary once the concentration ratio exceedsabout 10 and the system can only convert the directcomponent of solar radiation.

Energy Stored Technology

Mechanical 1. Pumping water2. Compressed air3. Fly wheel

Electromagnetic Electric current inSuperconducting ring

Chemical 1. Batteries2. Hydrogen production

Some energy storage systems

Although a variety of energy storage methods areunder consideration, the majority of stand alone PVsystems today use battery storage. The batteries inmost common use are lead acid batteries because oftheir good availability and cost effectiveness. Nickelcadmium batteries are used in some smallerapplications where their ruggedness, bothmechanical and electrical, is considered essential.However, their high cost per amount of energystored has prevented their wider use inphotovoltaic's.

POWER CONDITIONINGAND CONTROL

Lecture 11


The Blocking DiodeWe know that a solar cell in the dark behave as a

diode. Without special precautions, this type ofnight-time operation of the photovoltaic generatorwill provide a discharge path for the battery. Thesimplest solution is to separate the generator andbattery by blocking diode. When the voltage at thebattery exceeds the voltage at the generator, thediode becomes reverse-biased and prevents thebattery discharge.

Effect of Blocking Diode

During daytime operation, however, there will be avoltage drop across the blocking diode which shouldbe taken into account when designing the system.In system using modern PV modules where theseries resistance is low and the I-V characteristicapproaches the ideal curve, the battery dischargecurrent via the PV generator at night can be verysmall. The power dissipated at the blocking diodeduring daytime operation may exceed the night-time discharge losses. For this reason, the blockingdiode is sometimes omitted from the circuit design.

Charge RegulatorMeasures must be taken to prevent excessive

discharge and overcharging of batteries. Varioustype of charge regulators are available that fulfillthis role. In small applications (up to 100W), a shuntregulator can be used to dissipate the unwantedpower from the generator. A commonimplementation is to use a transistor in parallel withthe PV generator which is set to conduct and divertcurrent from the battery at a certain thresholdvoltage value.

Charge Regulator

Charge RegulatorIn larger applications, it is advisable to

disconnect the battery from the generator bymeans of series regulator. This can be anelectromechanical switch (for example arelay) or a solid state device (bipolartransistor, MOSFET, etc) . The former deviceshave the advantage that they do notdissipate energy but their reliability can be aproblem in locations with high dust or sandoccurrence.

Charge Regulator

The battery may be protected against excessive discharge by a charge limiter. This device is introduced between the load and the battery and acts as a switch which opens when the battery charge reaches a minimum acceptable level.

DC/DC Converter

The variability of the power output from the PVgenerator will often operate away from itsmaximum power point. The associated lossescan be avoided by the use of maximum-power-point tracker which ensures that thereis always a maximum energy transfer fromthe generator to the battery.

DC/DC Converter

The principles of the MPP tracker aredemonstrated in figure for the situationwhen the PV generator feeds power to aresistive load.

DC/DC ConverterThe I-V characteristic of the generator and the

load, together with constant power curvesP=VI=constant is shown. It is seen that at theoperating point 1 the delivered power issignificantly below Pmax, the maximum powerof PV generator.

DC/AC converter (inverter)

This is standard item of electronic equipmentwhich is used in many different applications.The input power is the DC power from thephotovoltaic generator or battery and theoutput is AC power used to run AC appliancesor fed into the utility grid. The efficiency ofthe inverters usually depends on the loadcurrent being a maximum at the nominaloutput power.


The majority of inverter for PV application canbe classified into three main categories.

First one are variable frequency inverters.These are used for stand-alone drive/shaftpower applications, almost exclusively in PVpumping system.


• Second are Self commutating fixed frequencyinverters. These are able to feed an isolateddistribution grid and, if equipped with specialparalleling control, also a grid supplied byother parallel power sources.

DC/AC converter (inverter)Third are Line-commutated fixed-frequency

inverters. These are able to feed the grid onlywhere the grid frequency is defined byanother power source connected in parallel.The inverter will not work if such externalfrequency reference is lacking.


The advantages and draw back of these two inverter types are summarised.

Alarms, Indicators and monitoring equipment

The system electronics should include someindicators which display the state of thesystem, or at least its main parameters. Themain indicators should display the low chargestate for batteries and the over charge.

In some instances, the user should be warnedabout the state of the system by an alarm.

17/17/2012 Engr. Tanveer ul Haq

Sizing of a PV system, particularly a stand-aloneone, is an important part of its design. Sincethe capital equipment cost is the majorcomponent of the price of solar electricity,oversizing the plant has a very detrimentaleffect on the price of the generated power.Undersizing a stand alone system, on theother hand, reduces the supply reliability.

27/17/2012 Engr. Tanveer ul Haq

The sizing of a system requires a knowledge of thesolar radiation data for the site, the load profileand the importance of supply continuity. Inaddition, other constrains on the design (forexample economic) must also be known, Thesizing procedure then recommends the size ofthe photovoltaic generator and battery capacitythat will be optimum for the application. It willalso allow the nominal characteristics of theelectronic components to be specified.

7/17/2012 Engr. Tanveer ul Haq 3

The first step in designing a solar PV system is to find out thetotal power and energy consumption of all loads that need tobe supplied by the solar PV system as follows:

1.1 Calculate total Watt-hours per day for each appliance used.Add the Watt-hours needed for all appliances together to getthe total Watt-hours per day which must be delivered to theappliances.

1.2 Calculate total Watt-hours per day needed from the PVmodules.Multiply the total appliances Watt-hours per day times 1.3(the energy lost in the system) to get the total Watt-hours perday which must be provided by the panels.


Different size of PV modules will produce differentamount of power. To find out the sizing of PVmodule, the total peak watt produced needs. Thepeak watt (Wp) produced depends on size of the PVmodule and climate of site location. We have toconsider “panel generation factor” which is differentin each site location. For Thailand, the panelgeneration factor is 3.43. To determine the sizing ofPV modules, calculate as follows:


2.1 Calculate the total Watt-peak rating needed for PVmodules

Divide the total Watt-hours per day needed from the PVmodules (from item 1.2) by 3.43 to get the total Watt-peakrating needed for the PV panels needed to operate theappliances.

2.2 Calculate the number of PV panels for the systemDivide the answer obtained in item 2.1 by the rated output

Watt-peak of the PV modules available to you. Increase anyfractional part of result to the next highest full number andthat will be the number of PV modules required


An inverter is used in the system where AC poweroutput is needed. The input rating of the invertershould never be lower than the total watt ofappliances. The inverter must have the samenominal voltage as your battery.

For stand-alone systems, the inverter must be largeenough to handle the total amount of Watts youwill be using at one time. The inverter size shouldbe 25-30% bigger than total Watts of appliances.


In case of appliance type is motor or compressorthen inverter size should be minimum 3 timesthe capacity of those appliances and must beadded to the inverter capacity to handle surgecurrent during starting.

For grid tie systems or grid connected systems, theinput rating of the inverter should be same as PVarray rating to allow for safe and efficientoperation.


The battery type recommended for using in solar PVsystem is deep cycle battery. Deep cycle battery isspecifically designed for to be discharged to lowenergy level and rapid recharged or cycle charged anddischarged day after day for years. The battery shouldbe large enough to store sufficient energy to operatethe appliances at night and cloudy days. To find outthe size of battery, calculate as follows:

4.1 Calculate total Watt-hours per day used byappliances.


4.2 Divide the total Watt-hours per day used by 0.85 forbattery loss.

4.3 Divide the answer obtained in item 4.2 by 0.6 for depth ofdischarge.

4.4 Divide the answer obtained in item 4.3 by the nominalbattery voltage.

4.5 Multiply the answer obtained in item 4.4 with days ofautonomy (the number of days that you need the systemto operate when there is no power produced by PV panels)to get the required Ampere-hour capacity of deep-cyclebattery.

Battery Capacity (Ah) = Total Watt-hours per day used by appliances x Days of autonomy(0.85 x 0.6 x nominal battery voltage)


A house has the following electrical appliance usage:• One 18 Watt fluorescent lamp with electronic ballast

used 4 hours per day.• One 60 Watt fan used for 2 hours per day.• One 75 Watt refrigerator that runs 24 hours per day

with compressor run 12 hours and off 12 hours.The system will be powered by 12 Vdc, 110 Wp PV

module.


Total appliance use = (18 W x 4 hours) + (60 W x 2 hours) + (75 W x 24 x 0.5 hours) = 1,092 Wh/day

Total PV panels energy needed = 1,092 x 1.3= 1,419.6 Wh/day.


2.1 Total Wp of PV panel capacity needed =1,419.6 / 3.4 = 413.9 Wp

2.2 Number of PV panels needed = 413.9 / 110 =3.76modules

Actual requirement = 4 modulesSo this system should be powered by at least 4

modules of 110 Wp PV module.


Total Watt of all appliances = 18 + 60 + 75 = 153 W

For safety, the inverter should be considered25-30% bigger size.

The inverter size should be about 190 W orgreater.


Total appliances use = (18 W x 4 hours) + (60 W x 2 hours) + (75 W x 12 hours)

Nominal battery voltage = 12 VDays of autonomy = 3 days

Battery capacity = [(18 W x 4 hours) + (60 W x 2 hours) + (75 W x 12 hours)] x 3 (0.85 x 0.6 x 12)

Total Ampere-hours required 535.29 AhSo the battery should be rated 12 V 600 Ah for 3

day autonomy.


PV module specificationPm = 110 WpVm = 16.7 VdcIm = 6.6 AVoc = 20.7 AIsc = 7.5 A

Solar charge controller rating = (4 strings x 7.5 A) x 1.3 = 39 A

So the solar charge controller should be rated 40A at 12 V or greater.



Lecture 13Engr. Tanveer ul Haq

Principle

In Concentrating Photovoltaics (CPV), a large area ofsunlight is focused onto the solar cell with thehelp of an optical device.

By concentrating sunlight onto a small area, thistechnology has three competitive advantages:

1. Requires less photovoltaic material to capturethe same sunlight as non-concentrating pv.

2. Makes the use of high-efficiency but expensivemulti-junction cells economically viable due tosmaller space requirements.

3. The optical system comprises standard materials,manufactured in proven processes. Thus, it is lessdependant on the immature silicon supply chain.Moreover, optics are less expensive than cells.

Concentrating light, however, requires direct sunlightrather than diffuse light, limiting this technology toclear, sunny locations.

Despite having been researched since the 1970s, it hasonly now entered the solar electricity sector as aviable alternative. Being a young technology, there isno single dominant design.

The most common classification of CPV- modules is bythe degree of concentration, which is expressed innumber of "suns". E.g. "3x" means that the intensityof the light that hits the photovoltaic material is 3times than it would be without concentration.

Low

concentration

Medium

concentration

High

concentration

Degree of

concentration2 - 10 10 - 100 > 100

Tracking?No tracking

necessary

1-axis tracking

sufficient

Dual axis

tracking

required

CoolingNo cooling

required

Passive cooling

sufficient

Active cooling

reuqired in

most instances.

Photovoltaic

Material

High- quality

silicon

Multi-junction

cells

Fresnel LensA Fresnel lens, named after the French physicist,

comprises several sections with different angles, thusreducing weight and thickness in comparison to astandard lens.

Fresnel lenses can be constructed

in a shape of a circle to provide a point focus withconcentration ratios of around 500, or

in cylindrical shape to provide line focus withlower concentration ratios.

With the high concentration ratio in a Fresnel pointlens, it is possible to use a multi-junctionphotovoltaic cell with maximum efficiency. In aline concentrator, it is more common to use highefficiency silicon.

Parabolic MirrorsHere, all incoming parallel light is reflected by the

collector (the first mirror) through a focal pointonto a second mirror.

Parabolic Mirrors

The second mirror, which is much smaller, is also aparabolic mirror with the same focal point. Itreflects the light beams to the middle of the firstparabolic mirror where it hits the solar cell.

The advantage of this configuration is that it doesnot require any optical lenses. However, losseswill occur in both mirrors. SolFocus has achieved aconcentration ratio of 500 in point concentrator-shape with dual axis- tracking.

ReflectorsLow concentration photovoltaic modules use mirrors to

concentrate sunlight onto a solar cell. Often, thesemirrors are manufactured with silicone-coveredmetal. This technique lowers the reflection losses byeffectively providing a second internal mirror.

ReflectorsThe angle of the mirrors depends on the inclination

angle and latitude as well as the module design,but is typically fixed. The concentration ratiosachieved range from 1.5 - 2.5.

Low concentration cells are usually made frommonocrystalline silicon. No cooling is required.

The largest low-concentration photovoltaic plant inthe world is Sevilla PV with modules from threecompanies: Artesa, Isofoton and Solartec.

Luminescent ConcentratorsIn a luminescent concentrator, light is refracted in a

luminescent film, and then being channelledtowards the photovoltaic material.

This is a very promising technology, as it does notrequire optical lenses or mirrors. Moreover, it alsoworks with diffuse light and hence does not needtracking. The concentration factor is around 3.

There are various developments going on. For instance,Covalent are using an organic material for the film,whilst Prism Solar use holographic film.

Furthermore, this concentrator does not need anycooling, as the film could be constructed such thatwavelenghts that can not be converted by the solarcell would just pass thru. Hence, unwantedwavelenghts would be removed.

CoolingMost concentrating pv systems require cooling.

Passive Cooling: Here, the cell is placed on a claddedcermaic substrate with high thermal conductivity.The ceramic also provides electrical isolation.

Active Cooling: Typically, liquid metal is used as acooling fluid, capable of cooling from 1,700°C to100°C.

IQBAL. M., An Introduction to Solar Radiation, Academic,New York,1983.

LOF, G. O. F., DUFFIE, F. A. and SMITH, C.O., WorldDistribution of Solar Radiation, University of WisconsinReport No. 23, 1966.

LORENZO, E., Solar Radiation, in : Luque A., Solar Cellsand optics for Photovoltaic Concentration, Adam Hilger,Bristol, 1989, pp 268-304.

PAGE, J. K., The estimation of monthly mean values ofdaily total short-wave radiation on vertical and inclinedsurfaces from sunshine records for latitudes 40°N-40°S,in: Proc. United Nations on New Sources of Energy, Vol. 4,1961, pp. 378-390.

PALZ, W., ed. European Solar Radiation Atlas, Volumes 1and 2 2nd edn. Verlag TUV Rheinland, Cologne, 1984.

GREEN, M. A., Solar Cells, Prentice Hall, Englewood Cliffs,NJ, 1982.

HERSH, P. and ZWEIBEL, K., Basic Photovoltaic Principlesand Methods, U.S. Government Printing Office,Washington, DC, SERI/SP-290-1448, 1982.

PULFREY, D. L., Photovoltaic Power Generation, VanNostrand Theinhold, New York, 1978.

VAN OVERSTRAETEN, R. And MERTENS, R., Physics,Technology and Use of Photovoltaics, Adam Hilger, Bristol1986.

GREEN, M. A., Solar Cells, Prentice Hall, Englewood Cliffs,NJ, 1982.

HERSH, P. and ZWEIBEL, K., Basic Photovoltaic Principlesand Methods, U.S. Government Printing Office,Washington, DC, SERI/SP-290-1448, 1982.

PULFREY, D. L., Photovoltaic Power Generation, VanNostrand Theinhold, New York, 1978.

VAN OVERSTRAETEN, R. And MERTENS, R., Physics,Technology and Use of Photovoltaics, Adam Hilger, Bristol1986.

• BOGUS, K. Space photovoltaics– present and future, ESABulletin 41, 70-77.

• HILL, R., Applications of Photovoltaics, Adam Hilger Bristol,1988.

• MARKVART, T. Radiation damage in solar cell, Journal ofMaterials Science: Materials in Electronics 1 (1), 1990:1-8.

• MAYCOCK, P-D. and STIREWALT, E. N., A Guide to thePhotovoltaic Revolution, Emaus, PA., 1985.

• BLOSS, W.H.,PFISTERER, F., KLEINKAUF, W., LANDAU, M.,WEBER, H. and HULLMAW, H. Grid-connected solarhouses, In: proc. 10th European Photovoltaic Solar EnergyConf., Lisbon, 1991: 1295-1300.

Every care is taken to ensure that allinformation in these lectures are present andcorrect. But there may still be errors. If youfind an error or omission, please let us know,and we will correct it as soon as possibleafter verification.

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Lectures on Solar Electricity By Engr Tanveer ul Haq