Professor Humayun A MughalChairman, Akhter Group PLC

Photovoltaic Technology.

The answer toGlobal Warming?

Global Warming – a Reality

Energy Production – major Contributor

Growing Demand for Electricity – no Going back

Green Energy – is The Only Option

The PHOTOVOLTAIC technology – is the Green Option

PV is the ANSWER to our needs - Economic, Environmentally friendly and Renewable

Key Issues

Warming World A

t-a-glan

ce: Clim

ate chan

ge - evid

ence an

d p

redictio

ns

Long Term High A

t-a-glan

ce: Clim

ate chan

ge - evid

ence an

d p

redictio

ns

 At-a-g

lance: C

limate ch

ang

e - eviden

ce and

pred

iction

s

Sea Level Rise

                                             

Growing Emissions A

t-a-glan

ce: Clim

ate chan

ge - evid

ence an

d p

redictio

ns

Cows are guilty of speeding up Global Warming.

QuickClimate

Quiz

B - FalseA - True

Methane is the second most significant greenhouse gas and cows are one of the greatest methane emitters. Their grassy diet and multiple stomachs cause them to produce methane, which they exhale with every breath.

A - True

D - UAEC - Kuwait

B - CanadaA - Australia

Which country has the highest CO2 emissions per capita?

The Carbon Dioxide Information Analysis Center figures:UAE - 6.17 metric tonnes of carbon per capita

Kuwait - 5.97, US - 5.4, Australia - 4.91, UK - 3.87.If total greenhouse gas emissions are compared, some analysts say Australia comes out higher than the US.

QuickClimate

Quiz

D - UAEE - USA

The big CO2 emitters

ENERGY USE WorldWide Energy Consumption 1980-2030

Where does ourenergy come from? Share of total Primary

Energy Supply in 2002

10,376 Mtoe IEA Energy Statistics

35.6%

41.6%

Increasing percentage of Total World Energy used for Electricity Generation

Quadrillion BTU

Electricity is

becoming more

important

Electricity How much do we use?

1999 2020

Total kwhrs 13 Trillion 22 Trillion

Population 6,004m 7,541m

Per capita kwhrs 2,165 2,917Electricity Use: International Energy Outlook 2002Population: US Census Bureau

Focus on

ElectricityWorld Electricity Generation by Fuel

Coal

• Easy to find, cheap, but high emissions• Steps toward increased efficiency:• New Super-critical plant

designs• Gas turbine exhausts to heat boiler feedwater

• Increase in biomass co-firing• Improvements in thermal efficiency

Technically exploitablecapability (TWh/yr)

1999 generation(TWh)

Hydropower - Regional Distribution

Hydro

• Potential in 150+ countries

• Proven, advanced technology

• Often integrated with other developments

• Low operating costs, long plant life

• Extremely efficient conversion

Nuclear

• Little pollution

• Virtually 0 greenhouse gas• Environmentally benign plants

Nuclear shares of national electricity generation - 2005

Natural GasAir Pollution from the Combustion of Fossil Fuels kg of emission per TJ of energy consumed

  Nat. Gas

Oil Coal

Nitrogen Oxides 43 142 359

Sulphur Dioxide 0.3 430 731

Particulates 2 36 1 333Sources: U.S. Environmental Protection Agency; American Gas Association

• A Low CO2 emitter

• Hydrogen fuel cells

• Steps toward increased efficiency:• Combined-cycle power

plants• Acid gas re-injection

OilElectricity generation by:

• Conventional Steam

• Combustion Turbine

• Combined-cycle

• Air, land and water pollution

• Solid waste burden

Solar Energy

How much is available?The sun’s rays provide enough energy to supply 10,000 timesthe TOTAL energy requirementof mankind.

So, how do we harness it?• Solar

Thermal• Photovoltaic

The ULTIMATE source.

Photovoltaic Possible materials to make PV cells

• CiGs Copper Indium Gallium Diselenide

• Polymers

• CdTe Cadmium Telluride

• Silicon Amorphous Thin Film

Mono crystalline Multi crystalline

0%

10%

20%

30%

40%

50%

60%

Other Am. Silicon Ribbon/SheetCrystalline

Mono Crystalline Multi Crystalline

Solar power market share by technology

The Chain

Metallurgical

Grade Silicon

Electronic Grade Chunks

Ingot

Bars

Wafers

Modules

“Sand”

Strings

Cells

Manufacturing ProcessLet’s start on the beach!

• It’s not good enough! We need 99.999999% purity.

• Chemical companies produce metallurgical grade (99%) silicon.

• The starting point is mined quartz sand, SiO2

Manufacturing ProcessMetallurgical Grade Silicon

Silicon Dioxide is mined from the earth's crust, melted, and taken through a complex series of reactions that occur in a furnace with temperatures from 1500 to 2000 oC to produce Metallurgical Grade Silicon (MG-Si).

Source - Wacker

Manufacturing ProcessHydrochlorination of Silicon

MG-Si is reacted with HCl to form trichlorosilane (TCS) in a fluidized-bed reactor. The TCS will later be used as an intermediate compound for polysilicon manufacturing. The TCS is created by heating powdered MG-Si at around 300 oC in the reactor. In the course of converting MG-Si to TCS, impurities such as Fe, Al and B are removed.

Si + 3HCl -----> SiHCL3 + H2

Manufacturing ProcessDistillation of Trichlorosilane

The next step is to distill the TCS to attain a high level of purity. At a boiling point of 31.8oC, the TCS is fractionally distilled to result in a level of electrically active impurities of less than 1ppba. The hyper-pure TCS is then vaporized, diluted with high-purity hydrogen, and introduced into a deposition reactor for the polysilicon manufacturing process.

Manufacturing ProcessPolysilicon Manufacturing

Conversion of hyper-pure TCS back tohyper-pure Silicon in poly deposition bells.Thin U-shaped silicon slimrods heated to ~1100 oC.Part of TCS is reduced to Silicon that slowly growsover the slimrods to a final diameter of 20cm or more.

Besides the reduction to Silicon, part of the TCS disproportions to the by-product SiCl4.

Polysilicon has typical metal contaminationof <1/100ppb and dopant impurities in the rangeof <1ppb. It is now suitable for further processing.

Manufacturing ProcessPolysilicon Manufacturing

The process focus shifts to the silicon’s atomic structure.

It must be tranformed into ingots with a singular crystal orientation (this is the primary purpose of Crystal Growing).

Before the Polysilicon can be utilized in the Crystal Growing process, it must be first mechanically broken into a chunks of 1 to 3 inches and undergo stringent surface etching and cleaning to maintain a high level of purity.

These chunks are then arranged into quartz crucibles which are packed to a specific weight; typically more than 100kg for 200mm crystals to be grown.

The next step is the actual crystal growing process.

Manufacturing ProcessCrystal Growing

The crystal growing process simply re-arranges silicon atoms into a specific crystal orientation.

The packed crucible is carefully positioned into the lower chamber of a furnace (right).

The polysilicon chunks are melted into liquid form, thengrown into an ingot.

As the polysilicon chunks reach their meltingpoint of 1420 oC, they change from solid to hotmolten liquid.

Heat Exchange Method (HEM) is used to formcrystalline structure.

Manufacturing ProcessCrystal Growing

Computer Simulation of HEM Process

Manufacturing ProcessIngot Sectioning

The process in the furnace will see the molten liquid formed into an ingot, using a directional solidification system (DSS), that may be sectioned into silicon bars.

Manufacturing ProcessIngot Sectioning

The Ingot bricks are cut down ….

Ingot sectioning saw Cropping saw

Bars

Manufacturing ProcessWafer Production

…. and sliced to create wafers.

Wire Saw

Wafers

Production line designed to produce photovoltaic

solar cells with as-cut p-type wafers for starting material.

Manufacturing ProcessFrom Wafers

2. Texturing ……………………….

3. Junction formation …………….

1. Surface etch …………………...

4. Edge etch ………………………

5. Oxide Etch ……..……………...

6. Antireflection coating …….…...

7. Metalization ……………..……..

8. Firing ……..……………………..

9. Wafer/Cell Characterization

1

2

3

4

5

6

7

Manufacturing ProcessCell Production

.

Surface Etch Removes saw damage (about 12 m on all

sides).

Texturing Roughens surface to minimise light reflection

Manufacturing Process – Cell Production

.

Junction FormationPhosphorous diffused into wafer to form p-n junction

Diffusion Furnace

Manufacturing Process – Cell Production

.

Edge Etch Removes the junction at the edge of the wafer

Wafer Holder

Plasma Etch Station

Manufacturing Process – Cell Production

.

Oxide Etch Removes oxides from surface formed during diffusion

Wafer Etch Station

Manufacturing Process – Cell Production

.

Anti-Reflection CoatingA silicon nitride layer reduces reflection of sunlight and passivates the cell

Plasma PECVD Furnace

Manufacturing Process – Cell Production

.

MetalisationFront and back contacts as well as the back aluminum layer are printed

Screen Printerwith automaticloading and unloadingof cells

Manufacturing Process – Cell Production

.

FiringThe metal contacts are heat treated (“fired”) to make contact to the silicon.

Firing furnace to sinter metal contacts

Manufacturing Process – Cell Production

Module Production

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

2003 2004 2005 2006 2007 2008 2009 2010

Price TrendEstimate of global average solar module

prices

US$/watt

Cost Breakdown Produced in Low labour cost

area

10.5%

2.6%8.9%

78%

(Labour cost $2/hour)

The FutureIs Bright

Example of cost recovery on an installation amortised over 25 years.

Assumes an increase in fossil fuel costs of 5% pa.

PV generatedper kwh

Fossil generated

per kwh

Future DevelopmentsR&D is focused on increasing conversion efficiency and reducing cell manufacturing cost, to reduce electricity generation cost.

• Improved crystallisation processes for high quality, low-cost silicon wafers

• Advanced silicon solar cell device structures and manufacturing processes

• Technology transfer of high efficiency solar cell processes from the laboratory to high volume production

• Reduction of the silicon wafer thickness to reduce the consumption of silicon

• Stable, high efficiency thin-film cells to reduce semiconductor materials costs

• Novel organic and polymer solar cells with potentially low manufacturing cost

• Solar concentrator systems using lenses or mirrors to focus the sunlight onto small-area, high-efficiency solar cells

Laser Grooved Buried Contact Layer High Efficiency Si Cells Currently up to 19% Efficiency Production Efficiencies up to 17%

AKHTER Improved Cell Efficiency

AKHTER Solar Lens Development

Optical Design

• Polarisation effects and the effects of real draught angles and facet sizes.

• Lens Zones modelled as a series of annular cones.

Energy concentration achieved by new optical design onto a 20mm diameter detector, placed in the focal plane of the lens.

AKHTER Solar Lens Development

DETECTOR IMAGE: INCOHERENT IRRADIANCE

New optical design reaches82% efficiency with a power distribution on the solar cellwithin a factor of 3.

This reduces hotspot problems.

• Focal plane 135mm from back surface of lens.

• Lens 4mm thick with facets 2mm deep.

• 3 degree draft angle.

• Uses specialised optical materials

AKHTER Solar ConcentratorDesign Characteristics

Computer controlled Dual Axis Tracking System

Compatible with new concentrator technology

Independent of sensors which usually result in maintenance and operational problems

Plant operation may be monitored from anywhere in the world

AKHTER Tracking System

Space requirement – 500m x 600mProducing 18Million Kilowatt hours per yearEnough to meet needs of 10,000 Homes

AKHTER 10MW Solar Plant

Akhter Solar Concentrator Plant

Professor Humayun A MughalChairman, Akhter Group PLC

Thank you