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Industry Forum Solar, Industry 26th EU-PVSEC Hamburg

Empire Riverside Hotel, 5th September 2011

Prof. Dr.-Ing. Michael Powalla

Zentrum für Sonnenenergie- und Wasserstoff-ForschungBaden-Württemberg (ZSW)

University of the State of Baden-Württemberg and National Research Center of the Helmholtz Association

Materials for Photovoltaics and Accumulators

Contents

Introduction

Thin-Film Photovoltaics

Photovoltaic Cell Technologies

Accumulators (with major input from Dr. Wohlfahrt-Mehrens, ZSW Ulm )

Battery Technology

Use Cases

Visions and Forecast

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Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (ZSW)

1988: ZSW was established as a non-profit foundation under the civil code.

2011: 200 employees work at 3 locations in Baden-Württemberg(Turnover: ca. 25 m. €)

Goal of the foundation:

Industry-oriented research and technology transfer in the field of renewable energy

• Photovoltaics – Thin-Film Technology

• Fuel Cells and Hydrogen Technology

• Electrochemical Storage

• Renewable Fuels and Reformers

• Systems Analysis and Consulting

ZSW’s Focus is on:

We work on the whole value chain: From materials science to production and product development.

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Stuttgart:Photovoltaics Division,Energy Policy and Energy CarriersCentral Office

Widderstall: Outdoor Test Facility

Ulm: Electrochemical Energy Technologies Division

ZSW Locations

6.600 m² new laboratories and offices: inauguration on 15th Sept. 2011

Development of Battery Research in Ulm:New ZSW Laboratory for Battery Technology (eLaB)

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Contents

Introduction

Thin-Film Photovoltaics

Photovoltaic Cell Technologies

Accumulators

Battery Technology

Use Cases

Visions and Forecast

Photovoltaic Technologies

Crystalline Si-modules: Si-wafers(mono-Si, multi-Si) 0.15 – 0.3 mm thick

0.01 – 0.04 m² diameterSi-wafer – cell – module~ 10 kg semiconductorper kW power

Thin-film technology: non-self-supporting films (a-Si/tf-c-Si, CdTe, CIS) a few µm thick

produced in m²high degree of vertical integration in production~ 0.2 kg semiconductor per kW power

Absorber Si

n+

p+

-+

High material quality Bulk crystals

n+

p+

High absorption Thin films

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Why Thin-film Solar Cells?

Low materials consumption Low energy consumption short energy payback time

- few process steps Direct fabrication of modules! Substrate sizes of up to 5.7 m2 possible (glass industry!)

- cost effective

- additional benefits: „nicer“, flexible, free choice of substrate (e.g. glass, metal, polymer, ...)

Crystalline silicon(mono-Si, multi-Si)

Thin film PV(a-Si/µc-Si, CdTe, CIS)

Thickness 150 µm – 300 µm

Thickness 3 µm – 5 µm

- thin

polycrystallinesemiconductors

Photovoltaic Materials

So

lar

cells

dyesolar cells

new concepts

silicon

organic cells

Multiband …

liquid electrolyte

solid electrolyte

CdTe

ChalkopyrideCIGSSe

III–V cells

thin-film

crystalline (wafer)monocrystalline

polycrystalline

Kesterite …

kristallin

amorphmikrokristallin

CdTe

chalcopyriteCIGSSe

amorphousmicrocrystalline

Thin Film

crystalline

“Work horse”

Advanced

R&D

6

Prof. Dr. M. Powalla / Seite 11

Quelle: http://upload.wikimedia.org/wikipedia/commons/7/74/PVeff%28rev100921%29.jpg

Prof. Dr. M. Powalla / Seite 12

Overview of Efficiencies

Photovoltaic MaterialLab.

cellPilot

production

Mass production

(module efficiency)

Monocrystalline Si 25 % 21 % 13 – 18 %

Polycrystalline Si 20 % 18 % 11 – 14 %

Amorphous a-Si/µcSi 13 % 8 – 11 % 7 – 10 %

Gallium-arsenide-basedmulti-junction cells (III/V)

42 % 26 % 22 %

Chalcopyrite (CIGS) 20 % 14 % 12 – 13 %

Cadmium telluride (CdTe) 17 % 12 % 10 – 11 %

Dye-sens. solar cells 11 % 3 – 5 %

Kesterite (CTZSS)

Organic cells

10 %

9 %

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Photovoltaic Thin-Film Technology

Rückkontakt

Frontkontakt

Substrat

Encapsulation Glass, foil + polymer

Glass, foil + polymer

Substrate Configuration

Absorber / p/n

Back contact

Front contact

Substrate

Absorber / p/n structure

Light

Frontkontakt

Rückkontakt

Encapsulation

Substrat

Superstrate Configuration

Absorber / p/n

Front contact

Back contact

Substrate

Absorber / p/n strukture

Light

Basic Principle

ZnO

Light

Glass (1-4mm)

TCO

n

Ag

p

i

n

pi

µc-Si:H

a-Si:H 3µm

a-Si/µc-Si tandem cells(„Micromorph“)

Mo (0.5 µm)

ZnO:Al (1 µm)

CdS (0.05 µm)

Glass (3 mm)

CIGS (2 µm)

i-ZnO (0.05 µm)

p

n

4µm

CIGS solar cells: CuIn1-xGaxSe1-ySy

Light

CdTe solar cells: CdTe

Light

Glass (1-4mm)

TCO

CdS (0.1 µm)

CdTe (3-8 µm)

Metal

Basic Principle: Thin-film Modules on the Market

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Upcoming New Thin-film Technologies

Organic solar cellDye-sensitized solar cell

FTO

TiO2 : Dye

glass

Electrolyte

Metal

glass

Light

ITO

PEDOT : PSS

glass

Organic absorber

Metal or TCO

Light

Highly absorbing thin-film gives name to technology

Transparent Conductive Oxide (TCO) for front contact

Production Depth

SG Si Si Wafer Si Cell Module

TF FabGlass,Raw materials

Module

Crystalline Silicon

Thin-film PV

All production steps in one line

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Production Technology (State of the Art)

1. Substrate• window glass, no standard size• 120 cm x 60 cm mostly used, or TFT “standards”• flexible foils more or less exotic

2. Thin-Film Technology• contact layers (TCO and metal): sputter, CVD• semiconductor:

• batch: PECVD, CBD• inline: co-evaporation, CSS, PECVD

3. Interconnection of cells• laser and mechanical patterning

4. Module technology• glass/glass laminates with EVA• glue bus bars, junction box etc.

Basic Principle: In-line Coating

VacuumLoad lock

VacuumLoad lock

Heating Deposition

Sputter cathodes orevaporation sources

Cleanedglass

Coatedglass

Basic Principle: Scribing Laser scribing system Source: Forschungszentrum Jülich

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Monolithically integrated thin-film module

P 1 P 2G 1 P 3G 2 P 1 P 2G 1 P 3G 2 Glass

MoCIGS

CdSi-ZnO

Zn:Al

xllC0

activearea

Example: ZSW-type CIGS Module

Interconnection of Single Cells to Modules

-

+

-

+

Module voltage is proportional to the number of series-connected cells.The current is proportional to the cell area (or „length“).

Voltage

Current

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Flexible Substrates Open new Application Areas

Contents

Introduction

Thin-Film Photovoltaics

Photovoltaic Cell Technologies

Accumulators

Battery Technology

Use Cases

Visions and Forecast

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Accumulators

Optimization of secondary batteries for various applications:

Traction Battery cycle stability

USV Battery floating battery

Mobility energy (energy density)

Hybrid electric vehicle(HEV) Battery power (power density)

Theoretical Limit of different sec. Battery Systems

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Ragone Diagram

Discharging time = spec. energy / spec. power

Electrochemical Storage

Storage + converterin one system Li-ion Batteries

Storage + converterin separate systems e.g. Redox Flow Batteries

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Redox-Flow-Batterye.g. Vanadium Redox Flow Battery

cell pump electrode (C)

Capacity (tank) and power (cell) can be separately dimensioned

Seasonal storage possible

By far the most interesting System: Lithium-Ion-BatterySpecifications for Storage Technology (Mobility)

Safetyalso by cockpit errorConsumer Battery: < 90 WhHybrid Vehicle: 1-2 kWhPlug-In HEV: 6 – 10 kWhBattery Vehicle : > 20 kWh

Costs< 300 €/kWh (system)

Energy DensityElectrical Range> 200 Wh/kg

Life Time>15 years or/and> 300,000 cycles HEV> 4,000 BEV

Operating Conditions-30°C through +50°C, quick loading

vibration, shock, crash

Power

> 100 kWel

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Functional Principle of Lithium-Ion-Battery - Combination of two Insertion Electrodes -

negative electrode / anode(e.g. graphite)

positive electrode / cathode(e.g. LiCoO2)

charge discharge

LiC6 C6 + Li+ + e- 2 Li0.5CoO2 + Li+ + e- 2 LiCoO2

electrolyte(z.B. LiPF6 / EC-DEC)

New Cathode Materials

Cathode is a limitationLiCoO2 150 mAh/gGraphite 320 mAh/g

Cathode with higher capacityand lower costs needed

Capacity (Ah/kg)

Po

ten

tial

ag

ain

st L

i/Li+

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New Cathode Materials

Layered structureLiCoO2, Li(Ni0,80Co0,15Al0,05)O2,

LiCo1/3Ni1/3Mn1/3O2

Spinel structureLiMn2O4, LiMn1.5Ni0.5O4

Olivine structureLiFePO4, LiMePO4

• Differences in Li+ diffusion• Differences in reaction mechanisms (phase transformation)• Differences in lattice stability in the delithiated state

Dependent on structure:

Comparison of Cathode Materials

MaterialPower density

Safety Stability Costsper Ah

Energy density

LCOLiCoO2

NCALiNi0,80Co0,15Al0,05O2

NMCLiNi0,33Mn0,33Co0,33O2

LMOLiMn2O4

LFPLiFePO4

Very good Very bad

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New Anode Materials

• “zero” strain• No reaction with electrolite• Very long life-time• Safe

• High capacity• Big volume change• Nano composite

Capacity [Ah/kg]

Po

ten

tial

ag

ain

st L

i/Li+

Alternative Anode Materials- Nanodisperse or meso porose TiO2 -

within the stability window of electrolyte no solid electrolyte interface (SEI) formation high thermal stability high safety no lithium plating

low capacity and lower cell voltage suited for high power cells and ultra long cycling life “high energy supercapacitor”

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Development Trends

Next generation of Li-Ion Batteries:

● High energy batteries (4C market)- high capacity anode and cathode materials- LiNi1/3Co1/3Mn1/3O2, LiNi1-xCoxO2

● High power batteries (Power Tools, HEV)- thin electrodes- Blend LiMn2O4 and LNC- LiMn2O4, LiFePO4

● Higher safety (Large batteries, HEV)- non flammable electrolytes, polymer electrolytes- safer cathode materials

● Cost reduction- replacement of cobalt and nickel

Battery Technology: Lithium-Ion-BatteryCylindrical

simple production (wrap) Firm body (40 bar) Defined opening pressure of

burst wave Safe leak tightness

+ High T-gradients in cell+ Bad packing density

Prismatic

Flat construction Good heat control Flexible dimensioning Simple battery stack

+ Difficult sealing+ Swelling at overpressure

Source: Varta

positive pole

negative pole

sealing gasket

Deckteil

Abstandhalter

Li-Verbindungen(cathode)

Grafitverbindungen(anode)

separator

overpressure valvedeflector

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Production Steps for Li-Ion Batteries

Source: http://www.mpoweruk.com/battery_manufacturing.htm

- 38 -

Lithium-Ion Battery Systems: Safety Issues

Source: W. Praas, 2008

Thermally Stable Cathode Materials

No Activity at Surface of Anode

Cell Structure

Stable Separator

Non-inflammable Electrolyte

Integration in Vehicle

Battery Management

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Contents

Introduction

Thin-Film Photovoltaics

Photovoltaic Cell Technologies

Accumulators

Battery Technology

Use Cases

Visions and Forecast

Requirements for Storage Systems

Cell 6 Ah 6 – 8 Ah 10 – 40 Ah > 40 Ah

Cell type cylindrical, prismatic prismatic prismatic, pouch

Cycle depth < 20% 50-70% 80-100%

Battery system Pb, Supercaps, Nickel/Metal hydride,

Lithium-IonLithium-Ion Lithium-Ion

Mild Hybrid Full HybridPlug-In Hybrid

BatteryE-Vehicle

Fuel CellE-Vehicle

Range Start / Stop Few km Up to 60 km 100 - 200 kmca. 500 km

Degree of Electrification 100%

H2

0 %

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Dr. M. Powalla / Seite 41

Important: Degree of Self-Consumption of PV, Combination with E-Vehicle, Decentralized Storage in a Smart Grid

Source: EnBW, Kundenzeitschrift

area neededVehicle today (Bio diesel): 10,000 m2

H2- Vehicle (H2 from bio mass): 1,000 m2

H2- Vehicle (H2 from PV): ca. 60 m2

E- Vehicle (PV): < 20 m2

Grid-Connected PV with Storage System

SOL-ION-System (25 systems in Germany) : Storage capacity from 10 to 12 kWh (Li ion batteries),PV-Power from 2 to 5 kWp,Inverter from 3 to 8 kW

Grid

PV Generator

SystemManagement

BatteryInverter

=

-Load

bidirectional energy flow

Stability with fluctuating PV input and fast load change:Self consumption vs. - Battery size

- PV size 80 % possible - Grid feed-in tariff

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Contents

Introduction

Thin-Film Photovoltaics

Photovoltaic Cell Technologies

Accumulators

Battery Technology

Use Cases

Visions and Forecast

Thin-Film PV:Cost Reduction Potential

Goal: 15 % – 18 % industrial module efficiency

- Standardization of processes and equipment- Understand correlations between preparation parameters

and material and interface characteristics- Develop multi-junction cells

New production processes (avoid expensive equipment)

Production costs from 2016 through 2025*

* Source: Strategic Research Agenda of EC (currently under revision)

a-Si/µc-Si CIS CdTe

< 0.5 €/Wp (@500 W/a) < 0.5 €/Wp < 0.4 €/Wp = 14 % = 16-17 % = 16 %

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Materialien, Recycling

Skaleneffekte

Fertigungs-technologie (Zelle + Modul)

Lithium-Ion-Battery: Cost Reduction Potential

BCG 2009

McKinsey 2009

McKinsey 2009 AT Kearney 2009

Li‐Tec 2009

Li‐Tec 2009

Anderman 2009

Anderman 2009

Fraunhofer 2009/CARB 2007

Fraunhofer 2009/

CARB 2007

Fraunhofer 2009/CARB 2007Fraunhofer 2009/CARB 2007

BCG 2009

SBLimotive 2009

McKinsey 2009

McKinsey 2009

AT Kearney 2009

CARB 2007

CARB 2007

0

300

600

900

1200

1500

2005 2010 2015 2020 2025 2030 2035

$/kW

h

Target costs 300 $/kWhEV target costs: 300 $/kWh

Source: Schott, B., C. Günther und A. Jossen, Batterie-Roadmap 2020+, ZSW-Studie, April 2010

Consumer cells today: 250 $/kWh

Quelle: SB LiMotive

• Materials, Recycling• Production Scale• Production Technology

(cell and module)

Visions:PV

New design concepts towards 30 % efficiency

Modern flat glass coaters can coat 3 x 6 m² plates with a

45s cycle time (1,500 m²/h), 9 km² SLSG per year

Modern „Roll-to-Roll Coater“ (width 4 m, speed 144,000 m²/h)

500 km² foil (1 x Bremen) per year

Or: Can we print our PV modules the way we print newspapers?

Li-Ion Battery

Li-Ion Technology will be the choice for e-mobility

Improve area and costs, energy and power density, safety and life-

time at the same time

no dramatic change in production technology needed but

correlated R&D Material-Cell-System needed for 250Wh/kg/15y

Significant increase of range/cycling due to new battery concepts