Transcript Photovoltaic Technology Answer to the Global Warming
Photovoltaic Technology.
The answer to Global Warming?
Professor Humayun A Mughal
Chairman, Akhter Group PLC
Key Issues
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 -
Environmentally friendly
and
Economic, Renewable
Warming World
Long Term High
Sea Level Rise
Growing Emissions
Quick Climate Quiz
Cows are guilty of speeding up Global Warming.
B - False
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.
Quick Climate Quiz
Which country has the highest CO2 emissions per capita?
A - Australia C - Kuwait E - USA B - Canada
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.
The
big
CO
2
emitters
ENERGY USE WorldWide Energy Consumption 1980-2030
Where
does our energy come from?
Geothermal / Solar / Wind 1% Comb. Renew & Waste 11% Hydro 2% Coal 23% Oil 35% Share of total Primary Energy Supply in 2002 10,376 Mtoe
IEA Energy Statistics
Gas 21% Nuclear 7%
Increasing percentage of Total World Energy used for Electricity Generation Electricity is becoming more important Quadrillion BTU 800 700 600 500 400 300 200 100 0 35.6% 2003 41.6% 2030
Electricity
How much do we use?
1999 2020 Total kwhrs Population Per capita kwhrs 13 Trillion 22 Trillion 6,004m 2,165 7,541m 2,917
Electricity Use: International Energy Outlook 2002 Population: US Census Bureau
Focus on
Electricity
Gas 15%
World Electricity Generation by Fuel
Coal 39% Oil 10% Other 1% Nuclear 16% Hydro 19%
Coal
• Easy to find, cheap, but high emissions • Steps toward increased efficiency: • New Super-critical plant designs • Increase in biomass co-firing • Gas turbine exhausts to heat boiler feedwater • Improvements in thermal efficiency
Hydro
• Potential in 150+
countries Technically exploitable capability
(TWh/yr)
Hydropower Regional Distribution 1999 generation
(TWh) • Proven, advanced technology • Extremely efficient conversion • Low operating costs, long plant life • Often integrated with other developments
Nuclear shares of national electricity generation - 2005
Nuclear
• Little pollution • Virtually 0 greenhouse gas •
Environmentally benign plants
Natural
Gas
Air Pollution from the Combustion of Fossil Fuels
kg of emission per TJ of energy consumed
Nitrogen Oxides Sulphur Dioxide
Nat. Gas 43 0.3
Oil 142 430 Coal 359 731
Particulates
2 36 1 333 Sources: U.S. Environmental Protection Agency; American Gas Association • A Low CO
2 emitter
• Steps toward increased efficiency: • Combined-cycle power plants • Acid gas re-injection • Hydrogen fuel cells
Oil
Electricity generation by: • Conventional Steam • Combustion Turbine • Combined-cycle • Solid waste burden • Air, land and water pollution
Solar Energy
The ULTIMATE source.
How much is
available?
The sun’s rays provide enough energy to supply 10,000 times the TOTAL energy requirement of mankind.
So ,
how
do we harness it?
• Solar Thermal • Photovoltaic
Photovoltaic
Possible
materials
to make PV cells • CdTe
Cadmium Telluride
• CiGs
Copper Indium Gallium Diselenide
• Polymers
Solar power market share by technology 60%
• Silicon
Amorphous Thin Film Mono crystalline Multi crystalline 50% 40% 30% 20% 10% 0% Other Am. Silicon Ribbon/Sheet Crystalline Mono Crystalline Multi Crystalline
The Chain
“Sand” Metallurgical Grade Silicon Electronic Grade Chunks Ingot Wafers Modules Strings Cells Bars
Manufacturing Process
Let’s start on the
beach!
• The starting point is mined quartz sand, SiO
2
• Chemical companies produce
metallurgical grade (99%) silicon.
• It’s not good enough!
We need 99.999999% purity.
Manufacturing Process
Metallurgical 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 Process
Hydrochlorination 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 Process
Distillation 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 Process
Polysilicon Manufacturing
Conversion of hyper-pure TCS back to hyper-pure Silicon in poly deposition bells.
Thin U-shaped silicon slimrods heated to ~1100 oC.
Part of TCS is reduced to Silicon that slowly grows over 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 contamination of <1/100ppb and dopant impurities in the range of <1ppb. It is now suitable for further processing.
Manufacturing Process
Polysilicon 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 Process
Crystal 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, then grown into an ingot.
As the polysilicon chunks reach their melting point of 1420 oC, they change from solid to hot molten liquid.
Heat Exchange Method (HEM) is used to form crystalline structure.
Manufacturing Process
Crystal Growing
Computer Simulation of HEM Process
Manufacturing Process
Ingot 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 Process
Ingot Sectioning
The Ingot bricks are cut down …. Ingot sectioning saw Cropping saw Bars
Manufacturing Process
Wafer Production
…. and sliced to create wafers. Wire Saw Wafers
Manufacturing Process
From Wafers Production line designed to produce photovoltaic solar cells with as-cut p-type wafers for starting material.
Manufacturing Process
Cell Production
3 4 1 2
1. Surface etch …………………...
2. Texturing ……………………….
3. Junction formation …………….
5
6. Antireflection coating …….…...
6
7
9. Wafer/Cell Characterization
Manufacturing Process –
Cell Production
Surface Etch
Removes saw damage (about 12 m on all sides).
Texturing
Roughens surface to minimise light reflection .
Manufacturing Process –
Cell Production
Junction Formation
Phosphorous 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 Coating
A silicon nitride layer reduces reflection of sunlight and passivates the cell
Plasma PECVD Furnace
.
Manufacturing Process –
Cell Production
Metalisation
Front and back contacts as well as the back aluminum layer are printed .
Screen Printer with automatic loading and unloading of cells
Manufacturing Process –
Cell Production
Firing
The metal contacts are heat treated (“fired”) to make contact to the silicon.
Firing furnace to
.
sinter metal contacts
Module Production
Price Trend
Estimate of global average solar module prices 4.5
4 3.5
3 2.5
2 1.5
1 0.5
0 US$/watt 2003 2004 2005 2006 2007 2008 2009 2010
Labour Overhead
Cost Breakdown
0.06
Produced in Low labour cost area (Labour cost $2/hour)
COST: $ per watt
2.6
%
0.06
8.9
%
0.24
10.5
%
0.2
Materials Equipment Labour Overhead 1.78
78 %
£0.25
The Future
Is Bright
Example of cost recovery on an installation amortised over 25 years. Assumes an increase in fossil fuel costs of 5% pa.
£0.20
PV generated per kwh £0.15
PV Per Kwh Fossil Per Kwh £0.10
£0.05
£0.00
2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020
Future Developments
R&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
AKHTER
Improved Cell Efficiency
Laser Grooved Buried Contact Layer High Efficiency Si Cells Currently up to 19% Efficiency Production Efficiencies up to 17%
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.
AKHTER
Solar Lens Development Energy concentration achieved by new optical design onto a 20mm diameter detector, placed in the focal plane of the lens.
DETECTOR IMAGE: INCOHERENT IRRADIANCE
AKHTER
Solar Concentrator Design Characteristics New optical design reaches 82% efficiency with a power distribution on the solar cell within 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
Tracking System 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
10MW Solar Plant Space requirement – 500m x 600m Producing 18Million Kilowatt hours per year Enough to meet needs of 10,000 Homes
Akhter Solar Concentrator Plant
Thank you
Professor Humayun A Mughal
Chairman, Akhter Group PLC