The Future of Solar Energy - gaccwest.com · The Future of Solar Energy Eicke R. Weber Fraunhofer-Institute for Solar Energy Systems ISE, and ... Source: G.W. Crabtree and N.S. Lewis,

ALBERT-LUDWIGS-

UNIVERSITÄT FREIBURG

!st Solar Symposium GACC San Francisco July 14, 2008

The Future of Solar Energy

Eicke R. Weber

Fraunhofer-Institute for Solar Energy Systems ISE,

and

Albert Ludwigs University, Freiburg, Germany


Protect the basis of human life on earth from

the catastrophic consequences of climate

change

Limited availability of non-renewable energies

Reduction of geopolitical conflict potential

Why do we need to transform the global energy system?


Time before present [kys] For reasons unknown,

the last ca. 10,000 ys were

extraordinary stable: “Holocene”

Temperature fluctuations in the last 100kys

Source: A. Ganopolski et al., 2001, Nature 409, 153-158


[CO2] 2004: 380 ppm, far above the highest peaks in 500 kys!

When will the temperature follow the [CO2]?

How high will it climb?

Will we terminate the Holocene irreversibly?

-400 -350 -300 -250 -200 -150 -100 -50 0

Tem

per

atu

re(°

C)

CO

2(p

pm

v)

Time before present [kys]

280

260

220

200

240

2

0

-2

-4

-6

-8


Globale climate change: the end of the holocene?

Human influence on the composition of the atmosphere is well established.

There has been a strong correlation between CO2-content of the

atmosphere and the earth„s temperature within the last > 500 kyrs.

The CO2-concentration today is more than 380ppm, far above the highest

value in the last 500 kyrs (ca. 290ppm); an increase to 500pm and more

can be expected.

Dramatic temperature increases and climate instabilities can bring about

the END OF THE HOLOCENE by human influence!


Development of the crude oil price

since 1960July 11,2008:

$147/barrel!

Daily oil production:

ca. 86 Mb/d

crude oil needed:

ca. 87 Mb/d

oil production

might never again

catch up with

consumption!


Strategies to reduce use of fossil fuels and CO2 emission

Energy efficiency - in production, traffic, building sector

Nuclear energy - non-renewable supply, final storage not clear, dangers during operation: no good solution for the global energy problem

Clean coal technologies - requires carbon sequestration, unproven technology, energy inefficient, may create danger of accidental release

Geothermal - reliable, efficient, but good sites are limited

Wind - good, but fluctuating production, limited number of suitable sites

Hydro - can be switched on instantaneously, suitable for storage,Good sites limited, production should be maximized

Biofuels - interesting as liquid fuel for traffic, production energy intensive

Solar energy (Photovoltaic, Solarthermal) - unlimited energy sourcePV: continuous price reduction through savings of scale


Each hour the sun delivers to earth the amount

of energy used by humans in a whole year

Sun radiation onto earth corresponds to

120,000 TW

Total human energy need in 2020: 20TW!

Magnitude of Solar Energy

Source: G.W. Crabtree and N.S. Lewis, Physics Today, March 2007


Solar energy

is the only kind of energy that can solve the

earth’s energy problems!


Other Renewables

Oil

Coal

Gas

Nuclear Energy

Hydropower

Biomass (traditional)

Biomass (modern)

Solar Electricity (PV

and solarthermal)

Solarthermal (Heat only)

Geothermal

Wind

Exemplary Path, global primary energy consumption

Jahr2000 2020 2040

200

600

1000

1400

2100

EJ/a

0

10

30

40

50

20

TW

Source: Scientific Council of the German Federal Government on Gobal Environment Change, 2003, www.wbgu.de


Solar thermal plant in Almeria, Spain


PV can easily supply a

substantial part of the

world energy needs

Area required to produce

20 TW through PV:

6 sites, 340 x 340 km2

each producing 3.3 TW

(using 15% PV cells,

1600hrs/a of sunshine)

Required Area for PV


Annual installation of PV modules (worldwide)

Source: 2000-2003 Strategies Unlimited, EPIA “solar generation” 2006, 2010 Rogol, LBBW Report 2007

AnnualModuleShipment(CrystallineSilicon)

MWp/a

2000 20122005 2010

15% Growth

25% Growth

2001 2002 2003 2004 2006 2007 2008 2009 2011

1,600

2,000

4,000

1,200

800

400

3,600

3,200

2,800

2,400

4,400

4,800

40 % CAGR

Projection (2003)Actual Shipments

2006: more than 1.9 GWp

Far above the most optimistic

Forecast!

2003: 600 MWp

Forecast 2010:

> 12 GWp!


First 20% mono Si lab cell (4 cm²)

First 20% mono Si

production cell (100cm²)

Residential roof program, JPN

Renewable energy law, D

Development of the global PV-market

Graph: G. Willeke, 2008

1990: 1/3 thin-film, c-Si, mc-Si

2007: 2.4 Gwp,

>90% c-Si & mc-Si!

Germany 2007:

about 1.2 GWp!


Two technologies currently dominate the PV market:

Single Crystals:

- highest efficiency

- slow process

- high costs

Poly (multi) crystalline:

- low cost

- fast process

- lower efficiency

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Interesting further approaches: ribbon, sheet material,

but: savings of scale?


Price learn curve of crystalline Si PV-modules

d [µm] = 400 300 200 100 50

cell [%] = 10 15 18 20 22%

20202010

(25%)

[€/Wp]

100

10

1

1980

1990

20002004

110-210-310-4 102 103

Installed Peak Power (cumulative) [GWp]

10-1 10

Graph: G. Willeke, ISE

(30%)


Competitiveness of PV power and utility prices

Source: W. Hoffmann, AMAT and EPIA, 2007

PV power

Peak power

Bulk power


July 15, 2008 CaliSolar Confidential 18

The Problem of the Si feedstock shortage Forecast April 2007(Rogol, Munich 07)

Source: Wacker 2nd SoG-Si workshop 2005


Increased production of semiconductor-grade

Si: for 2010, > 70 kt/a expected;

Thinner cells (but: limits cell size!);

Thin film cells, such as a-Si, CIS, CIGS, CdTe

(but: limited efficiency, >10% difficult!)

Thin-film c-Si cells on various substrates

(of special interest: metall. grade mc-Si!);

Upgraded metallurgical-grade Si (‚dirty Si„)

Highly efficient cells for concentrators

Possible solutions of the Si feedstock shortage:


From quartz to coal to metallurgical Silicon (mg-Si)Raw material

C SiO2

Consumable

electrodes

Electric

energy Filter

Cleaned gas

Charge

material

Liquid metal

Refining

Silicon

Solidification

SizingCrushing

CraterRecovered energy Silica

Source:

B. Ceccaroli and O. Lohne

Source: Elkem

• 1 Mio. t/a

• 1 $/kg

Source: RW silicium


From mg-Si to ultrapure poly-Si: the Siemens Process

‘fluidised bed’ reactor fractional distillation

mg-Si powder

hot Si dust

exhaust (SiHCl3,

SiCL4, H2, Metall Chloride)

heating elements

HCl

quartz tube

ca. 30.000 t/a

ca. $100/kg

Alternative for PV: upgraded metallurgical Si, umg-Si (‚dirty silicon‘)


Silicon feedstock material

Metallurgical Si: 98% to 99.9% pure,

metallic conductivity, impurities in several-ppm and more range

Semiconductor-grade Si: Siemens process, Si distilled in gase phase;

B, P: well controlled, metals in ppb and below range

Solar-grade Si: purified via gas phase, simple crystallization;

B, P: well controlled, other impurities around&below ppm range

Upgraded metallurgical Si: Dopants reduced in liquid phase;

B,P: reduced just as needed, other impurities in ppm range

Latest industrial results: InterSolar session A1: Roy Johnson, CEO, CaliSolar


Concepts worked on at ISE: InertCell, EpiCell

EpiCell: Epitaxial silicon thin-film

solar cell on (near) metallurgical

grade wafer substrate

low grade silicon

wafer

silicon base layer

200 µm

20 µm

base contact

emitter contact

emitter layer 1 µm

texture / ARC

wafe

r equiv

ale

nt

PMG-Si wafer~1 cm

200 µm

base contact

emitter contact

emitter layer 0.5 µm

texture / ARC

Inert

Wafe

r

InertCell: Wafer solar cell made

from (moderately) purified silicon,

impurities inactivated


‚dirty‘ (upgraded mg-Si)

p++ silicon substrate

back contact

front contact

clean epitaxial (SiHCl3)

silicon layer

20 µm

200 µm

emitter

antireflection coating

Graph: G. Willeke, 2008

Concepts for PV from umg-Si at ISE: EpiCell


500 1000 1500 2000 25000

200

400

600

800

1000

1200

1400

1600

Le

istu

ng

sd

ich

te [

W/m

2µ

m]

AM15

GaInP

GaInAs

Ge

Wellenlänge [nm]

Efficiencies beyond the Shockley-Queisser limit

Maximum efficiencies

(theoretical, without

optical concentration):

2-jct. cells: 45.3%

3-jct. cells: 51.2%

4-jct. cells: 54.9%

...


ARC

n-graded Ga1-x

InxAs buffer layer

p-Ge substrate (100)

p+-AlGaInAs - barrier layer

p-GaInAs - base

n-GaInAs - emitter

n+-AlGaInP/AlInAs - barrier layer

p++-AlGaAs

p+-AlGaInP - barrier layer

p-GaInP - base

GaInP - undoped layer

n-GaInP - emitter

n+-AlInP - window layer

cap layer

n++-GaAs or GaInP

p+-GaInP - barrier layer

GaInAs - undoped layer

p+-GaInAs - barrier layer

1.8 eV

1.3 eV

front contact

rear contact

p++-AlGaAs

n++-GaInAs

n- doped window- and nucleation layer

n-Ge diffused emitter

0.7 eV

Ga0.65In0.35P

tunnel diode

Ga0.83In0.17As

tunnel diode

Ge substrate

High-efficiency ISE triple-junction solar cells


GaInP/GaInAs/Ge

solar cell with = 35.2 %

at C = 500

Triple-junction solar cell for high optical concentration, > 35%


Amonix (US)Solar Systems (AUS)

High-concentration PV tracker systems

Concentrix Solar (D)

InterSolar session B6:

A. Gombert, CTO


P 1 P 2 P 3Glass

Mo

CdS

ZnO:Al

i- ZnO

Cu(In,Ga)Se2

CI(G)S – Solar Cell,

schematic

Source: ZSW (Stuttgart)

Record efficiency: 18% (small area)

Best module efficiency: ca. 11%


Aluminum

Absorber

Polymer AnodeITO

Substrate

Organic Solar Cell

Donor

Akzeptor

record = 4,8%

FMF, ISE = 3,7%


Conclusion I: the big picture for solar energy

PV will grow in the coming decades 10 - 100 times in volume,

from a $15 B market into a $100 - 300 B market,

replacing fossil fuels, reducing climate gases, and providing energy

for the world, including developing countries such as China and India.

PV provides valuable peak power, today it is already economically

competitive in certain areas; lower cost of PV and rising cost of oil and other

fossil fuels will result in grid parity in the near future

Crystalline Si will remain the dominant PV technology for a long time,

the current shortage will be overcome by increased production of pure Si

and the introduction of purified (upgraded) metallurgical-grade Si.

Only crystalline Si offers any amount of PV power without any ressource

limitation, i.e. it is truely sustainable even in a 100s of GWp/a market.


Conclusion II: the big picture for solar energy

One key to decreasing costs for PV is the production volume;

therefore intelligent support mechanisms such as intelligent feed-in laws

are required worldwide for the next 10-15 years.

Organic solar cells, other „3rd generation‟ concepts will serve

interesting market niches, but are not likely to affect the global picture.

Thin film modules out of a-Si, CIS, or CdTe have an interesting market

opportunity today, their long-term success will depend on efficiency

improvements and cost reduction.

A second key to decreasing costs for PV is the use of alternative Si

with higher impurity content: Defect Engineering for umg-Si


Attractive feed-in tarifs without cap have demonstrated to be the most effective

mechanisms for the rapid introduction of PV

and other renewable energies - this is the free market at work!

Quota system: requires utilites to produce a certain quota of renewable energy,

target group: utilities, keeps power production centralized.

Comparison of PV support systems:

Feed-in system: offers an attractive price for each kWhr produced,

target group: anybody who likes to make a good investment

(German system: guarantees about 10% annual return on investment!)

Rebate system: offers rebates (cash or tax incentives) for installation of PV,

lessens price pressure, net metering: frustration for energy-efficient houses,

target group: environmentally conscious homeowners

Documents

The Future of Solar Energy - gaccwest.com · The Future of Solar Energy Eicke R. Weber Fraunhofer-Institute for Solar Energy Systems ISE, and ... Source: G.W. Crabtree and N.S. Lewis,