Solar Cell Calibration and Measurement Techniques


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NASA Technical Memorandum

113155

Solar Cell Calibration and

Measurement

Techniques

Sheila Lewis

Bailey, Dave Brinker, Research Center

Cleveland, Ohio

and Henry

Curtis

Phillip Jenkins Essential Research, Inc. Cleveland, Ohio
Dave Scheiman NYMA, Inc. Brook Park, Ohio

Prepared for the

32nd Intersociety

Energy Conversion

cosponsored

by AIChE, ANS, SAE,

Honolulu, Hawaii, July 27--August

Engineering AIAA, ASME,
1, 1997

Conference and IEEE

National Aeronautics

and

Space Administration

Lewis Research Center

November 1997

IECEC-97534

NASA Center for Aerospace Information

800 Elkridge Landing Road

Linthicum Heights, Price Code: A02

MD 21090-2934

Available from

National

Technical Information Service
5287 Port Royal Road Springfield, VA 22100
Price Code: A02

SOLAR

CELL CALIBRATION

AND MEASUREMENT

TECHNIQUES

Sheila Bailey, Dave Brinker, Henry Curtis NASA Lewis Research Center

MS 302-1

Phone:

Cleveland, Ohio 44135

216-433-2228;

Fax: 216-433-6106

Phone:

Phillip Jenkins Essential Research, Inc.

NASA Lewis Research Center

MS 302-1

Cleveland, Ohio 44135

216-433-2233;

Fax: 216-433-6106

Phone:

Dave Scheiman

NYMA

NASA Lewis Research Center

MS 302-1

Cleveland, Ohio 44135

216-433-6756;

Fax: 216-433-6106

ABSTRACT

The increasing complexity of space solar cells and the

increasing international markets for both cells and arrays has

resulted in workshops jointly sponsored by NASDA, ESA and

NASA. These workshops are designed to obtain international

agreement on standardized values for the AMO spectrum and

constant, recommend laboratory measurement

practices and

establish a set of protocols for international

comparison

of

laboratory measurements.

A working draft of an ISO standard,

WD15387, "Requirements

for Measurement and Calibration

Procedures for Space Solar Cells" was discussed with a focus on the scope of the document, a definition of primary standard

cell, and required error analysis for all measurement

techniques. Working groups addressed

Zero (AM0)

solar constant

and

the issues of Air Mass

spectrum,

laboratory

measurement techniques,

and the international

round robin

methodology. A summary is presented of the current state of each area and the formulation of the ISO document.

INTRODUCTION

The expanding choice of space solar cells from worldwide

vendors has focused attention

on the need for

internationally recognized standard value of the Air Mass Zero

(AMO) solar constant and spectral intensity distribution and

the primary set of standards and protocols to establish

equitable world.

comparisons To achieve

of laboratory measurements around the

this universality

of calibration

and

laboratory measurements

NASA Lewis Research Center's

Photovoltaic Branch initiated a series of workshops jointly

sponsored

by the National

Aeronautics

and Space

Administration (NASA), the European Space Agency (ESA),

and the National Space Development

Agency of Japan

(NASDA). The First International Workshop on Space Solar

Cell Calibration and Measurement Techniques took place in Honolulu, Hawaii in December of 1994 and was attended by

thirty-four participants from Japan, the United States and

Europe representing not only the space agencies but industry

as well (Brinker et al, 1995). The Second Workshop took

place in Madrid, Spain in September of 1995 with twenty-five

participants,

expanding to include

China.

The Third

Workshop occurred at Tsukuba, Japan in November of 1996

with thirty-five participants.

There were three established

working groups: A. AM0 Solar Constant and Spectrum; B.

Laboratory Measurements Techniques; C. International round

Robin Methodology.

The current draft of the International

Organization for Standardization

(ISO) standard, WD 15387

was presented by Mr. Kiyota of SHARP Corporation.

Dr.

Cuquel

of CNES presented

the CNES balloon flight

calibration system

and Mr. Scheiman of NASA Lewis

Research Center (LeRC) presented the JPL balloon flight calibration method and the LeRC aircraft calibration method.

Dr. Bucher of the Fraunhofer Institute discussed the Institute

fur Solare Energiesysteme

(ISE) Photovoltaic (PV) Charts.

ISO 15387

Terrestrial solar cell standards

are governed by the

International Electrotechnical

Commission (IEC), specifically

the technical committee number 82:

Solar Photovoltaic

Energy System. However, it was decided that space solar cell standards would fall under the auspices of ISO technical

committee number 20: Aircraft and Space Vehicle, sub

committee number 14: Space Systems and Operation.

Japan

proposed ISO standardization of space solar cell calibration at

a meeting in 1994 and submitted the first working draft in

1996 with input from the International Workshop participants and other interested parties. The ISO and IEC standards can

be compared in the topics which are addressed by each set of

standards: requirements measurement principles

for reference solar cells (IEC 904-2), for space solar cells with reference to

the extraterrestrial

solar spectral irradiance data (IEC 903-3),

computation of spectral mismatch error introduced in the

testing of the sol ar cells (IEC 904-7), guidance for the spectral

measurement

of a solar cell (IEC 904-8), solar simulator

performance requirements (IEC 904-9), calibration methods

NASA TM-113155

1

forprimarryeferencseolarcell (IEC82-101m), ethodosf spectrdailstributiomneasuremfoerntthelightsourc(eASTM andJISstandardsm), easuremoefnct urrent-volta(Ig-Ve ) characterist(iIcEsC904-1)p, rocedurfeosr temperatuarned irradiancceorrectiontos measureI-dV characteristoicfs crystallinseiliconsolacr ells(IEC891).Thescopeof the ISOdocumeisnrtestrictetodsingle-junctciorynstallinsepace solacr ells.TheAM0standasrdolarcellwouldrecordthe typeof calibratiosnpectrum(extraterrestriaJl:PLhighaltitudbealloon(36.6km),CNEShigh-altitubdaelloo(n36.6 km),spacsehuttloer spacsetation(500km);direcst unlight: NASALewishigh-altituadiercraf(t15.4km);groundlevel sunlight:globasl unlighdt,irectnormasl unlighst;ynthetic sunlights: olasr imulatoorrdifferentisapl ectrraelspon(sife applicableT).hecalibratiorensultws ill berepeatabwleithin astandadrdeviatioonf + 1% . The solar constant, which is

slightly variable, is accepted to be 1367 Wm 2 + 7 Wm- 2 .

The standard temperature test condition is 25 + I°C. The

following data are recorded: identification number, type solar

spectrum, cell manufacturer,

material type, type of cell

package, calibration organization, site and date of calibration,

method of calibration,

radiometer

or standard lamp

characteristics

(where applicable) , AM0 standard solar cell

identification

(for simulator calibration,

where applicable),

simulator characteristics,

type of temperature sensor, relative

spectral response,

temperature

coefficient

of short-circuit

current, calibration value (AW-_m2), and claimed accuracy

(with a description of error analysis).

The final version of the

working draft ISO 15387 will be discussed at the 4th

International Workshop in October of 1997 at NASA Lewis

Research Center.

WORKING

GROUP:

AMO SOLAR CONSTANT

&

SPECTRUM

The values identified

above were accepted

for cell

temperature, spectrum, and solar constant corresponding to the

most recent cavity measurement in space. It was agreed to

solicit "a letter of agreement"

from all space calibration

agencies in order to reach common reporting conditions; to

collect reports of the calibration procedures and a detailed

error analysis of all procedures.

The following institutions

agreed to use the standard measurement

conditions (pending

completion of current contracts 25°C): NASA, JPL, NASDA,

specifying 28°C rather than ESA, CNES, CAST, DRA,

NREL, Japanese Space Solar Cell Calibration Committee,

INTA-Spasotab,

HIREC, WYMA, Space

Essential Research, Hughes, TecStar.

System

Loral,

WORKING GROUP: LABORATORY

MEASUREMENTS

TECHNIQUES

Single light source simulators,

commonly

used in

laboratories

and by commercial

vendors, are accurate for

single junction gallium arsenide (GaAs) and silicon (Si) solar

cells within an experimental error of approximately

1%. The

spikes of the Xenon light source of the X25 Spectrolab Single Source Simulator, for example, (see Fig. 1) can become a

significant source of error for multi-junction

cells unless

carefully filtered. Recently, a filtered dual source simulator

has become available (see Fig. 2) which provides a closer

matched AM0 spectrum. The spectral response of a GaAs/Ge

single junction cell can be seen in Fig. 3 and a

GalnP/GaAs/Ge

dual junction cell can be seen in Fig. 4. It

should be noted that both spectrally tunable solar simulators

and subcell standards for multi-junction cells will be required to obtain + 1% accuracy. A dual beam pulse solar simulator
for module and array testing would be difficult to develop, the more probable option would be a suitably filtered design. A color filter bias light method has been used and verified with
three junction devices (Bucher et al, 1995). A proposal has been submitted to NASA from the Photovoltaic and Space Environments Branch at NASA Lewis and the Ohio Aerospace Institute to utilize the international space station as a solar cell calibration and measurement facility.

WORKING GROUP:

INTERNATIONAL

ROUND ROBIN

METHODOLOGY

The first international round robin of solar cell calibration

was established

following the 1st International

Workshop.

There were 12 samples (4 each from NASA, ESA, and

NASDA) which would be measured by NASA, ESA, NASDA

and the Chinese Academy of Space Technology (CAST) and

then reflown at NASA. These samples were silicon cells,

GaAs cells, and high efficiency silicon cells. The first round

robin is complete.

These cells will now be cycled through

other organizations,

e.g. DRA, JPL, NREL, ISE, etc.

Measurement data will be reported at the 26th IEEE-PVSC in October of 1997.

A second round robin of Si and GaAs solar ceils was

proposed with NASA, JPL, and CNES providing the cells, 2 ceils each; 1 Si and 1 GaAs. They would be measured at

NASA Lewis then sent to CNES and JPL.

These

extraterrestrial for publication

measurements

are anticipated

at the 2nd World Conference

to be available on Photovoltaic

Energy Conversion in July of 1998. After the extraterrestrial

measurements

the cells would be measured by NASA and

DRA in a solar simulator, CAST by direct sunlight, and ESA-

Spasolab by global sunlight with ISE to be determined.

It was

agreed to begin a round robin of GalnP/GaAs/Ge

dual junction

cells, not to compare results, but to assess measurement

techniques for multi-junction cells.

CONCLUSION

The three International Workshops held since 1994 have

involved eight countries,

government

organizations

and

corporations.

They have provided a forum for discussion

regarding the ISO 15387 standards, achieved agreement on the

standardized values of the AMO solar constant and spectral

intensity distribution, established a set of protocols for making

interlaboratory

comparison measurements,

initiated

round

robin cell calibration series, and addressed the complicated

issue of multi-junction

solar cell measurements.

The 4th

International Workshop on Space Solar Cells will NASA Lewis Research Center, October 6th - 9th, further information contact Dave Brinker (Phone: 2236, Fax: 216-433-6106, [email protected]

be held at 1997. For
216-433-

REFERENCES

Brinker, D.J., Curtis, H.B., Flood, DJ., Jenkins, P.,

Scheiman, D.A., "A Summary of the International Workshops

on Space

Solar Cell Calibration

and Measurement

Techniques", Space Photovoltaic Research and Technology

Proceedings,186-190,

(1995).

Bucher, K. and Kunzelmann, "The FhG-ISE PV Charts:

Assessment Photovoltaic 2357, (1995).

of PV Device Solar Energy

Performance",

13th European

Conference Proceedings,

2352-

NASA TM-113155

2

300

E

¢..
&..

20(

-

E

O O
t,"-

Spectrum
Ji, ;_"_r,M__%-,',°

spec,,ox,-a__, ,

100-
tn O3

/ !! ,-

0
2OO

_"

I

400

I

t

600

I

I

800

Wavelength

(nm)

tJ

I

I

1000

'_ ,
_,

I ,i

a

1200

FIG. 1 AIR MASS 0 AND 1.5 SPECTRUM AND SPECTROLAB X-25L SPECTRUM

1800 1600 1400

4OO 200

NASA TM-! 13155

FIG. 2 TS SPACE SYSTEMS MULTIPLE SOURCE SIMULATOR

FIG. 3 SPECTRAL RESPONSE OF A GaAs/Ge SOLAR CELL

NASA TM-113155

FIG. 4 SPECTRAL RESPONSE OF A Galn/GaAs/Ge

SOLAR CELL

4

REPORT DOCUMENTATION

PAGE

FormApproved
OMB No. 0704-0188

Public reporting burden for this collection

of information

is estimated

to average 1 hour

gethenng collection

and maintaining of information,

the data needed, and completing

including suggestions

for reducing

and reviewing the collection this burden, to Washington

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end to the Office of Management

1. AGENCY USE ONLY (Leave blank)

2. REPORT DATE

November 1997

4. TITLE AND SUBTITLE

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including the time for reviewing

instructions,

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Send

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regarding this burden estimate or any other aspect of this

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and Budget, Paperwork

Reduction

Project (0704-0188),

Washington,

DC 20503.

3. REPORTTYPE AND DATESCOVERED

Technical Memorandum

5. FUNDING NUMBERS

Solar Cell Calibration and Measurement

Techniques

6. AUTHOR(S) Shells Bailey, Dave Brinker,

Henry Curtis, Phillip Jenkins,

and Dave Scheiman

WU-632-1A-1A

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

National .Aeronautics and Space lewis Research Center Cleveland, Ohio 44135-3191

Administration

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Washington, DC 20546-0001

Administration

8. PERFORMING

ORGANIZATION

REPORT

NUMBER

E - 10905

10. SPONSORING/MONITORING

AGENCY

REPORT

NUMBER

NASA TM-113155 IECEC-97534

11. SUPPLEMENTARY NOTES

Prepared for the 32rid Intersociety Energy Conversion Engineering Conference cosponsored by AIChE, ANS, SAE, AIAA,

ASME, and IEEE, Honolulu, Hawaii, July 27--August

1, 1997. Sheila Bailey, Dave Brinker, and Henry Curtis, NASA Lewis

Research Center; Phillip Jenkins, Essential Research, Inc., Cleveland, Ohio 44135 (work funded by NASA Contract NAS3-

27243); Dave Scheiman, NYMA, Inc., 2001 Aerospace Parkway, Brook Park, Ohio 44142 (work funded by NASA Contract

NAS3-27186).

Responsible person, Sheila Bailey, organization code 5410, (216) 433-2228.

12a. DISTRIBUTION/AVAiLABiLITY STATEMENT

12b. DISTRIBUTION CODE

Unclassified - Unlimited Subject Categories: 33 and 20

Distribution:

Nonstandard

This publication is available from the NASA Center for AeroSpace Information, (301) 621-0390

13. ABSTRACT

(Maximum

200 words)

The increasing complexity

of space solar cells and the increasing international

markets for both cells and arrays has

resulted in workshops jointly sponsored by NASDA, ESA and NASA. These workshops are designed to obtain interna-

tional agreement on standardized

values for the AMO spectrum and constant, recommend

laboratory measurement

prac-

tices and establish a set of protocols for international

comparison

of laboratory measurements.

A working draft of an ISO

standard, WD15387, "Requirements

for Measurement

and Calibration Procedures for Space Solar Cells" was discussed

with a focus on the scope of the document, a definition of primary standard cell, and required error analysis for all mea-

surerrient techniques.

Working groups addressed the issues of Air Mass Zero (AM0) solar constant and spectrum, labora-

tory measurement

techniques, and the international

round robin methodology.

A summary is presented of the current state

of each area and the formulation of the ISO document.

14. SUBJECT TERMS Solar cell

17. SECURITY CLASSIFICATION OF REPORT Unclassified
NSN 7540-01-280-5500

18. SECURITY CLASSIFICATION OF THIS PAGE
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19. SECURITYCLASSIFICATION OF ABSTRACT
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OF PAGES

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Solar Cell Calibration and Measurement Techniques