11/6/2012

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Overview to Solar PV

Professor Richard R. Lunt Department of Chemical Engineering and Material Science,

Department of Physics, Michigan State University

Solar PV Training Session I

Nov 2nd, 2012

Outline – Week 1

• Review of Solar Energy Potential

• How PVs Work

• Materials New and Old

• Theoretical Limits/Next Generation

____Break_____

• PV Configurations and Wiring

• PV Toys!

• Conclusions

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Map of the World Scaled to Energy Consumption by Country

Newman, U. Michigan, 2006

In 2002 the world burned energy at a rate of 13.5 TW/yr

How fast will we burn energy in 2050 ?

Energy use estimates from Nocera, Daedalus 2006 & Lewis and Nocera, PNAS 2006

If we use energy like in U.S. we will need 102TW

Conservative estimate 28~35TW

How much is 13TW per Year?

100 Billion 100W Bulbs Running all

Year

82,000 Billion Hamburgers =

32 burgers per day per person!

Drive in car (40mi/gal.) =

Driving 1 time around earth per person per

year

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Worldwide Energy Supply

REN21 2006 global status report on renewables

Geothermal

Hydroelectric

Nuclear

Solar

Where do we use energy:

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How does the US use energy?

Motivation for Clean Renewable Energy

IPCC 4th Assessment Report, plot from NASA

Climate Change Predictions

High growth Moderate growth

Low growth

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0

10

20

30

40

50

Energ

y Pote

nti

al (T

W)

Potential of Alternative Energy Sources

Practical potential

(10% eff., 1.5% of Land)

N. Lewis “Powering the Planet” (MRS Bulletin 32, 2007)

• 13TW – Worldwide Consumption, 3TW - US consumption

• 120,000 TW provided by the sun

• 300 x 300 km2 at 10% = 3TW <2% of land mass Total PV ever produced, worldwide

Global LCD production in 2008

U.S. Newspaper production, per year

Photovoltaics

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There are several Major Reasons

• It costs too much. And it requires a lot of area (even

though it is a small fraction)

• Our Electrical grid can only handle ~20% input from intermittent sources

• There is no Sun at night so we need BIG batteries

There are several Major Reasons

• It costs too much. And it requires a lot of area (even

though it is a small fraction)

• Our Electrical grid can only handle ~20% input from intermittent sources

• They can be unsightly

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Flavors Of Solar Energy Generation

Luminescent Solar Concentrator

Solar Thermal - Heating

Solar Thermal - Geometric Collector

Steam Turbine Electricity

P Abs Carnot

Solar Electrical – PV

1 CCarnot

H

T

T

~

J. Kalowekamo and E. Baker, Solar Energy 83, 1224 (2009).

Cost

US Average 2010: 5¢/kW-hr

20% Most Expensive 2010: 12¢/kW-hr

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Present AVERAGE

Cost of Deploying

Solar Energy

is 20¢ to 40¢/kWh

Cost of a kWeh varies across the U.S.

TODAY SOLAR CAN COMPETE IN SOME OF THESE ELECTRICITY MARKETS

(without additional government incentives)

Aim to capture 10% of electrical generation with Solar PVs

14¢

US Average 2010: 5¢/kW-hr

20% Most Expensive 2010: 12¢/kW-hr

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Cost

1Kalowekamo, et al. Solar Energy 83 (2009) 1224-1231. 2Lushetsky, “The prospect for $1/Watt Electricity from Solar,” $1/W Workshop, August 10, 2010.

Costs (Cont.)

DOE, $1/Watt White Paper

DOE Targets

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Costs (Cont.)

DOE, $1/Watt White Paper

DOE Targets

Costs (Cont.)

DOE, $1/Watt White Paper

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What happens if we get to $1/W Equivalent?

Locations (by State) where Solar PV become price competitive

DOE White Paper: “$1/W Photovoltaic Systems”

Efficiency Comparison

18%

20%

29%

29%

31%

31%

63%

DOE White Paper: “$1/W Photovoltaic Systems”

Suntech,

First Solar

Heliatek

GaAs

http://www.solar-facts.com/panels/panel-manufacturers.php Long list of Manufacturers:

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0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.20

5

10

15

20

25

30

35

Effic

ien

cy (

%)

Band Gap (eV)

Approaching Shockley-Quiesser

GaAs 85% of SQ, Si 75% of SQ

Which is more widespread? Depends on Application

Green Prog. Photovolt.: Res. Appl, 2011. NREL, available online http://www.nrel.gov/ncpv/

(2012)

c-GaAs c-Si

c-InP

CIGS CIS

c-Ge CZTSSe

a-Si

CdTe c-GaInP

Organic

AM1.5G Isotropic

1% PL

Figures of Merit: kW/m2, $/kW-hr, kW/kg,

kW-hr/$-kg

Cost of Si

• High Temperature Processing: 1687K-2000K

• $1/g $20/m2 (Raw Material Cost), $200-$400/m2 (full device)

• Ultra High Purity Needed

a = 102 cm-1

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Cost of Organic Materials

• Abundant: ~100,000 tons of CuPc/year

• Low materials costs: ~$1/gm 17¢/m2 , $20-100/m2 (full device)

• Low Temperature Processing RT-500K

This is where Chemical Engineers Come in!

Copper Phthalocyanine

a = 105 cm-1

Operating Principles

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500 750 1000 1250 1500 1750 20000

1

2

3

4

5

0.0

0.5

1.0

1.5

2.0

Sola

r F

lux (

Photo

n/n

m3-s

)

Wavelength (nm)

Photo

pic

Lum

inosi

ty (

norm

.)

500 750 1000 1250 1500 1750 20000

1

2

3

4

5

0.0

0.5

1.0

1.5

2.0

Sola

r F

lux (

Photo

n/n

m3 -s

)

Wavelength (nm)

Photo

pic

Lum

inosi

ty (

norm

.)

VIS

Solar Flux

Absorption Spectra of PV Materials

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Processes in PV

A DS CC

p n i

Processes in Bilayer PV

A ED CT DS CC A ED CT DS A ED CT A ED A

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Processes in Organic Bilayer PV

Ideal Diode

Jph

0 exp 1p

SC

S P

RI qVJ J J

Area R R nkT

V

J

Current-Voltage Simplified Equation

OC SC

Power VI

Max Power V I FF

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Next Generation Concepts

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Third Generation Concepts • Primary Losses of Efficiency for Single-Junction

1) Incomplete Absorption, 2) Thermal Relaxation (Heating),

3) Carrier Recombination, 4) VOC must be < EG,

5) Shape of Photocurrent curve

Henry, C. JAP 51, 4494, 1980

Third Generation Concepts

• Concepts to go beyond Single Junction Limits

– Primarily to reduce thermal, voltage, or abs. losses: (Hot-carrier, Concentrator, Singlet Fiss., MEG, Tandem)

Up-Converter

Henry, C. JAP 51, 4494, 1980

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A Taste of The Research That We Do Here at MSU

e-

Windows – 55-80% Transmission1)

Can Do it with Molecules Excitons!

Absorb NIR, Transmit VIS

Need OPV with abs. peak outside VIS

- Sig. surface area with glass surfaces

- Glass 1/3 Module Cost

- Infrastructure – 1/2- 2/3 BOS Cost

Is there a way to do this with inorg. SC?

Transparent Solar Cells

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• 2/3 Solar Flux in NIR/IR Single Junction Limit (20%), 10-cell

Tandem (33%)

• Use Excitonic Materials to optimize Transparency and Efficiency

Transparent Solar Cells

Practical Demonstration

Lunt, R. et al. APL, 98, 113305 (2011).

Single Devices:

Monolithic Series Integration:

Large-Area Integration:

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Lets Talk PV Practicals!

PV Configuration

Grid-tied with battery

backup system.

Off-Grid DC system

(with/without inverter):

PVinsights.com

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Panel Assemblies

• How much voltage do we get

in each cell, panel?

• Why are they wired up this

way?

PV Education.Org

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Which way does the Current Flow?

Solar Charger

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Solar Charger

Why Do we Use

Two Batteries in

Series?!

Solar Charger

Can we do this?!

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Solar Charger

Can we do this?! Yes, Sometimes.

It depends on the Sun Intensity!

Solar Charger

Charging Battery

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Solar Charger

Charging iPod

Solar Charger

Battery Acts as Buffer!

We use it for Temporary Storage

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Solar Charger

If there is not a lot of light, we will not charge battery!

We will DISCHARGE BATTERY!

Solar Charger

Diode acts a one-way valve for the Current

Flow

Insert Diode ?

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How Long will it Take to Charge?

What will it depend on?

1) Area of Solar Cell

2) Amount of Sunlight

3) Solar Cell Efficiency

Lets do a calculation

4) Solar Cell Orientation

Determine Local Solar Insolation

NREL, PVWatts v1

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Units for Solar Calculation!

/W J s

63.6 10kW hr x J

2 241

kW hr W

m day m

Sun Intensity at High Noon average for US

(titled at 37° tilt):

21 1000

WSun

m

Average over year in Lansing

(including night) for flat panel:

2 23.83 160

kW hr W

m day m

Used in electricity billing!

Solar Insolation Units

Watts = Energy Flux

Max flux higher! (~760W/m2)

Ideal Diode

_OCMP

LOAD MP

MP SC

VVR

I I

OC SC

Power VI

Max Power V I FF

To get here: we need a load:

Load

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PV Configurations

Series Connection: Parallel Connection:

Combination:

Maximum Power Point Tracking

Current-Voltage Characteristics are Dependent on Light Intensity

Current-Voltage changes, changes Maximum Power Point

Added electronics to get most power out of Solar Cells – Add Cost

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Finger Spacing – Collecting Charges

PV Education.org

Degradation and Failure

Solar Cell Degradation (Corrosion, H20, O2)

Short-Circuited Cells

Open-Circuited Cells

Module Glass Breakage

Module Delamination

Hot-Spot Failures

By-Pass Diode Failure

Encapsulant Failure

PV Education.Org

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• There is enough solar energy to power USA, and entire World!

Quick Summary

• To do this we need:

– Better Grid

– Better Energy Storage

– Cheaper Solar Cells

• Inexpensive materials and processing

• Lightweight

• We Learned about practical aspects

- Types of Solar Energy

- Factors impacting efficiency, cost

- Configuration/Wiring

- Calculate charging time