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 - Economic,
Environmentally friendly and Renewable
At-a-glance: Climate change - evidence and predictions
Warming World
At-a-glance: Climate change - evidence and predictions
Long Term High
At-a-glance: Climate change - evidence and predictions
Sea Level Rise
At-a-glance: Climate change - evidence and predictions
Growing Emissions
Quick
Climate
Quiz
Cows are guilty of speeding up
Global Warming.
A - True
True
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
DD -- UAE
UAE
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?
Share of total Primary
Energy Supply in 2002
10,376 Mtoe
Gas
21%
Coal
23%
Geothermal /
Solar / Wind
1%
Comb. Renew
& Waste
11% Hydro
2%
IEA Energy Statistics
Nuclear
7%
Oil
35%
Increasing percentage of Total World
Energy used for Electricity Generation
Quadrillion BTU
800
700
41.6%
600
500
Electricity
is
becoming
more
important
400
35.6%
300
200
100
0
2003
2030
Electricity
How much do we
1999
use?
2020
Total kwhrs 13 Trillion 22 Trillion
Population
Per capita kwhrs
6,004m
7,541m
2,165
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
Technically
exploitable
capability
Hydropower Regional Distribution
(TWh/yr)
• Potential in 150+
countries
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
Nat.
Gas
Oil
Coal
Nitrogen Oxides
43
142
359
Sulphur Dioxide
0.3
430
731
2
36
1 333
Particulates
Sources: U.S. Environmental Protection Agency; American Gas Association
• A Low CO2 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
• Silicon
Amorphous Thin Film
Mono crystalline
Multi crystalline
Solar power market share by technology
60%
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
Modules
Wafers
Strings
Cells
Ingot
Bars
Manufacturing Process
Let’s start on the
beach!
• The starting point is mined quartz sand, SiO2
• 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 hyperpure 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 ….
Bars
Ingot sectioning saw
Cropping saw
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
1. Surface etch …………………...
1
2. Texturing ……………………….
2
3. Junction formation …………….
3
4. Edge etch ………………………
4
5. Oxide Etch ……..……………...
5
6. Antireflection coating …….…...
7. Metalization ……………..……..
6
8. Firing ……..……………………..
7
9. Wafer/Cell Characterization
Manufacturing Process – Cell Production
Surface Etch
Texturing
Removes saw damage (about 12 m on all sides).
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
Wafer Etch
Station
Removes oxides from surface formed during diffusion
.
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
US$/watt
3
2.5
2
1.5
1
0.5
0
2003
2004
2005
2006
2007
2008
2009
2010
r
ead
Cost Breakdown
0.06
0.24
Produced in Low labour cost area
(Labour cost $2/hour)
COST: $ per watt
2.6%
10.5%
8.9%
0.24
0.06
0.2
1.78
78%
Materials
Equipment
Labour
Overhead
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.
£0.25
PV generated
£0.20
per kwh
£0.15
PV Per Kwh
per kwh Per Kwh
Fossil
Fossil generated
£0.10
£0.05
20
20
19
18
20
20
17
16
20
20
15
14
20
20
13
12
20
11
20
20
10
09
20
20
08
07
20
20
06
05
20
20
20
04
£0.00
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