Lecture 1 Overview: Sun, Earth, and the Solar Cell/uploads/Lecture01-S… · Overview: Sun, Earth, and the Solar Cell M. A. Alam [email protected] Electrical and Computer Engineering

Lecture 1Overview: Sun, Earth, and the Solar Cell

M. A. Alam

[email protected]

Electrical and Computer Engineering

Purdue University

West Lafayette, IN USA

Theory and Practice of Solar Cells: A Cell to System Perspective

1

M. A. Alam, PV Lecture Notes

33

Outline

1) Introduction: A short history of solar energy

2) The story of the sun and sunlight

3) Earth’s atmosphere determine sunlight on ground

4) Solar cells are extremely inefficient

5) Levelized cost of electricity as a savior

6) ConclusionsM. A. Alam, PV Lecture Notes

44

Solar resources and potential

Solar energy can meet world energy demand

1000-fold extra!

Source: OECD Observer No. 258/59 December 2006

𝐴 = 510 × 1012 𝑚2

𝑃 = 103 𝑊/𝑚2

𝐷 = 0.1 − 0.3𝑃𝑇~ 50 − 150 𝑃𝑊

𝑊 = 7.7 × 109

𝑃 = 2.5 × 103 𝑊𝑃𝑇~ 2 𝑇𝑊


55

Even a small-state like Indiana..

Source: Nate

Lewis

(Caltech)


A brief history

Great benefits for telephone users and for all mankind will come

From this forward step in harnessing the limitless power of the sun.

-- Bell Telephone Laboratories, 1954.

Use in Telstar in 1962 and other satellites thereafter Increasing terrestrial deployment all over the world

6

77

Off-grid application …

On/off grid

Scalability

Siting

Speed of installation

Peak profile vs. demand


88

Types of Solar Energy Converter

Photo: Brightsource Energy,

http://ecotechdaily.com/wp-content/uploads/2008/04/brightsource2_620px.jpgPhoto: Stirling Energy Systems,

www.wapa.gov/ES/pubs/esb/1998/98Aug/Graphics/Pg5b.jpg

Source: TGW, http://openlearn.open.ac.uk/file.php/1697/220880-1f1.29.jpgPhoto: Ausra, Inc.,

www.instablogsimages.com/images/2007/09/21/ausra-solar-farm_5810.jpg

9

Top ten corporate users


1010

Outline



3) Earth’s atmosphere dictates sunlight on ground



6) Conclusions


1111

Actors: Sun, Earth, Solar cell, and bank

Sun Temp. 5777 K

Distance: 1.496𝑥1011 𝑚Earth Radius: 4000 miles

Temperature: 300K

Irradiance ... 1000 W/𝑚2

PV Max. Efficiency = 1/3

Bank interest – 4-5%


1212

Sun is a nuclear reactor


1313

The extraterrestrial solar intensity is easily calculated

𝑟𝑠 𝑑

0 0.5 1 1.5 2

x 1012

100

101

102

103

104

105

Ear

th

Satu

rn

Mar

s

Jupiter

d (m)

𝐼 0𝑑

(W/m

2)

𝐼𝑠 = 𝜎 𝑇𝑠4

𝜎 = 5.67 × 10−8W

m2K4𝐼0(𝑑) = 𝐼𝑠

𝑟𝑠𝑑

2

1414

Measuring sun’s temperature without a thermometer

𝐼0 𝑑 = 𝜎𝑇𝑠4 = 𝐼𝑠

𝑟𝑠𝑑

2

𝜃 = 2 𝑟𝑠/𝑑

𝜎 is known from SB relation

𝐼𝑠 is known from balloon experiment𝑟𝑠 d

Measure 𝜃 by angle-ratio

𝑑 is known by Newton’s law

𝑟𝑠 is determined.


Temperature of the Sun

𝜎 = 5.67 ∗ 10−8𝑊

𝑚2𝐾4(SB constant)

𝐼0(𝑟𝑝) = 1367𝑊/𝑚2 (solar constant)

𝑟𝑝 = 1.496 × 1011 𝑚 (earth to sun radius)

𝑟𝑠 = 6.963 × 108 (radius of sun)

𝑇𝑠 =𝐼0 𝑟𝑝 × 4𝜋𝑟𝑝

2

𝜎 4𝜋 𝑟𝑠2

14

= 5775.8 𝐾


15

1616

Outline



3) Earth’s atmosphere and sunlight on ground



6) ConclusionsM. A. Alam, PV Lecture Notes

Only a fraction of sunlight arrives at the

ground (and that is a very good thing!)

𝑇𝑝 = 𝑇𝑠𝑟𝑠2𝑑

1 − 𝛼

𝜖

𝛼 = albedo of the planet𝜖 = emissivity of the planetd = planet − earth distance

𝑃𝑎𝑏𝑠 = 1 − 𝛼 𝑃𝑝𝑙𝑎𝑛𝑒𝑡𝑃𝑒𝑚𝑖𝑡 = 𝜖 𝜎 𝑇𝑝

4 × 4 𝜋 𝑟𝑝2

𝑃𝑒𝑚𝑖𝑡 = 𝑃𝑎𝑏𝑠

1382.62 × 1 − 𝛼= 987W/m2

17

0

100

200

300

400

1300

1350

1400

1450

J F M A M J J A S ON DMonth

ly

(kW

-hr/m2)

𝐼 0(W

/m2)

Extra-

terrestrial

Monthly GHI

21 June21 Dec.

3 Jan.21 March

23 Sep.3 July

Solstice

23.45°

𝐼0(𝑑𝑛) = 𝐼0 (𝑑)(1 + Δ cos 2𝜋 𝑑𝑛 /𝐷)

Δ = 2(𝑅max– 𝑅min)/𝑑

Sunlight varies with seasons

18

1919

Sunlight depends on latitude

http://www.ez2c.de/ml/solar_land_area/


http://www.ez2c.de/ml/solar_land_area/

N

S

JulySep.

Nov.𝜃𝑍

𝛾𝑆

W

ES

N

Solar intensity changes with day, season, and latitudes

𝐼𝐷𝑁𝐼 = 𝐼0 𝑑𝑛 𝑇(𝜃𝑍 𝑡 )

𝐴𝑀(𝑡) = 1/ cos 𝜃𝑍(𝑡)

𝑇 𝜃𝑍 𝑡 = 𝑐1𝜏𝐴𝑀 𝑡 𝑐2

𝑐1 ∼ 1, 𝑐2 ∼ 0.67

𝜏 ≡ 1 − 𝛼

20

Direct normal irradiance (DNI)

Direct and diffused light

21

𝐼𝐺𝑁𝐼 = 𝐼𝐷𝑁𝐼 cos(𝜃𝑍) + 𝐼𝐷𝐻𝐼 𝑘𝑡 = 𝐼𝐺𝐻𝐼/𝐼0cos(𝜃𝑧)

Diffused horizontal irradiance

Global horizontal irradiance

4 8 12 16 200

0.2

0.4

0.6

0.8

1

4 8 12 16 200

0.2

0.4

0.6

0.8

1

(a)

Time (h) Time (h)

Inso

lation (

kW

/m2)

GH

I (k

W/m

2)

Cloudy day

Clear

day

DHI

DNI

GHI

(b)

PV intensity is easily determined

Washington DC (June 15, 2014, clear; June 19, 2014 cloudy)

22

Atmosphere and solar spectrum

𝐹𝐵𝐵 =𝐸2

4𝜋2ℏ2𝑐21

𝑒 Τ𝐸 𝑘𝐵𝑇𝑠 − 1𝐸𝑝𝑒𝑎𝑘 ∼ 2.8 𝑘𝐵 𝑇𝑠𝐸𝑎𝑣𝑔 ∼ 2.7 𝑘𝐵 𝑇𝑠

23

0 500 1000 1500 20000

0.5

1

1.5

2

2.5

0 500 1000 1500 20000

0.2

0.4

0.6

0.8

1

0 500 1000 1500 20000

0.5

1

1.5

2

2.5Mars Earth

𝜆 (nm) 𝜆 (nm) 𝜆 (nm)

𝐼(W

/m2/n

m)

𝐼(W

/m2/n

m)

𝐼(W

/m2/n

m)Extraterrestrial

Surface

(30° zenith)

AM0

AM1.5D

AM1.5G

AM0

BB (5777K)

(a) (b) (c)

Standard olar spectrum and air-mass (AM)

𝐹𝐵𝐵 =𝐸2

4𝜋2ℏ2𝑐21

𝑒 Τ𝐸 𝑘𝐵𝑇𝑠 − 1

𝐸𝑝𝑒𝑎𝑘 ∼ 2.8 𝑘𝐵 𝑇𝑠𝐸𝑎𝑣𝑔 ∼ 2.7 𝑘𝐵 𝑇𝑠

Global (G) includes diffused light, but direct (D) does not.

24

2525

Outline



3) Earth’s atmosphere and sunlight on ground


5) Levelized cost of electricity

6) Conclusions



26

Photoelectric effect and solar cells

UVelectron

metal

Sunlightelectron

p-n junction

load

Why PV spectrum matters

27

𝐸𝑐

𝐸𝑣

Only 33% efficient

Lost in cell-to-module transition

M. A. Alam, PV Lecture Notes 28

An Inefficient Machine!

29

𝜂𝐴 ∼ 1/2

𝜂𝑁 = 2/𝜋

𝜂𝑆𝑄 = 1/3

𝜂 = 𝜂𝑁 × 𝜂𝑆𝑄 × 𝜂𝑀 × 𝜂𝐴=2

𝜋×1

3×5

6×1

2∼

1

10

𝜂𝑀 = 4/5


Collection of

independent

2-level PV

nm

p-n junction solar cellCell

ModulePanel

Rooftop

PVSolar farm

nm-𝜇m cm-m km

Fabrication,

Device physics,

Manufacturing

Reliability, LCOE

Course outline: A multiscale problem


30

A magnificent multiscale problem:Atom-to-farm perspective

31

Length

Time

s

ns

year

decade

nm cm m km

Material

Storage

50 100 150 200

5

10

15

20

25

30

35

40

45

50 -1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

DeviceProcess

Reliability

Solar Farm

Module

Mm

17 orders

15 orders

An atom-to-system approach for PV research. M. A. Alam, PV Lecture Notes

3232

Outline



3) Atmosphere dictates sunlight on ground



6) Conclusions


3333

Solar energy is not free

LCOE =Cost

Energy produced

Energy produced = Insolation x efficiency x lifetime

Cost = cost of converter + maintenance + interest


… with drop cost of energy produced

Acwa Power

5.84 cents!

Taqnia

5 cents!


34

Resources (http://nanohub.org/groups/pv)


35

ADEPT 1D

PV Analyzer

PV Panel SimOPV Lab

http://nanohub.org/groups/pv

Conclusions

Photovoltaics is an important source of

renewable energy

The combination of sun, earth, PV

technology, and financing determine the

trajectory of the industry.

The spectacular drop in cost has fueled the

growth of the PV industry.

Our goal is the end-to-end understanding

of PV technology.


36

Self-test questions

What is the peak and average energy of the solar

spectrum? What is the energy flux density on the

surface of the sun?

What fraction of the sky (in solid angles) does the sun

cover?

What wavelengths of light are absorbed by

atomospheric oxygen?

What is the difference between AM0 vs. extraterrestrial

spectrum?

Calculate the DNI intensity on June 15 for at time when

the Azimuth angle is 50 degrees?


37

Documents

Lecture 1 Overview: Sun, Earth, and the Solar Cell/uploads/Lecture01-S… · Overview: Sun, Earth, and the Solar Cell M. A. Alam [email protected] Electrical and Computer Engineering