Stefan Winter, PTB German member of IEC TC82-WG2

12.10.2016

Standards for PV metrology IEC 60904 and IEC 61853

Overview

o Demand for high accuracy solar cell calibrations

o Standard Test Conditions

o DSR Method

o The new PTB setup: Advantages and disadvantages

o International Comparisons => WPVS

Magnitude of Solar Energy

• Sun radiation onto earth corresponds to 120,000 TW • Total human energy need today: 13 TW

Solar energy is the only kind of energy that can solve the earth‘s energy problems!

Sources: G.W. Crabtree and N.S. Lewis, Physics Today, March 2007 ; and Prof. Eicke Weber, ISE

Land requirements for PV

Source: G.W. Crabtree and N.S. Lewis, Physics Today, March 2007 sowie Prof. Eicke Weber, ISE

You need 6 areas of 340x340 km² (1800 kW/J) with actual available solar modules (15 % eff.) to get 20 TW

Energetic amortization of PV systems

• Study for the German Federal Ministry of Economics, Technology and Labor:

• Including solar modules, mounting system, frames, cabels, inverter, auxiliary energy, operating supplies

• Briem et al, Study „Lebenszyklusanalysen ausgewählter zukünftiger Stromerzeugungstechniken“ made by Institut für Energiewirtschaft und Rationelle Energieanwendung an der Universität Stuttgart, Deutsches Zentrum für Luft- und Raumfahrt, Institut für Technische Thermodynamik, Stuttgart, Forschungsstelle für Energiewirtschaft e. V., München and the „Lehrstuhl für Energiesysteme und Energiewirtschaft“

• Published by the VDI-Verlag in 2004 (Page 133, Tab. 7-15)

Energetic Amortisation time in years

sc-Si system 2,2 pc-Si system 2,3 a-Si system 3,2 CIS System 2,1

Future trends

Economic Impact of Measurement Uncertainty for Photovoltaics

Source of data: EPIA (European Photovoltaic Industry Association) and for 2015 according to IHS market research institute

• Financial uncertainty = Global annual installation × Price × Uncertainty • 2012: Financial uncertainty = 30 GW/year × 1.7 €/W × 1 % = 500 M€/year

⇒ A measurement uncertainty of 1% leads to a financial uncertainty of 500 M€/year ⇒ High demand for high accuracy solar cell calibrations

Solar parks are financed from banks, who add the financial uncertainty arising from measurement uncertainty to the total amount to be financed. A low uncertainty leads to competitive advantage.

Source of data: www.solarwirtschaft.de/preisindex

2006

2007

2008

2009

2010

2011

2012

0

1

2

3

4

5

Syst

em p

rices

for e

nd c

usto

mer

s in

Eur

o / W

att

Prices in Euro/Watt

2006

2007

2008

2009

2010

2011

2012

2013

2014

2015

*0

10

20

30

40

50

Year

ly wo

rldwi

de n

ewly

inst

alle

d PV

Pow

er /

GW

New PV installations

Metrological Integration

Calibration- laboratories

PV - Industry

Calibr.-Costs in Euro 3000 - 4800

Uncertainty (k=2) > 0,5 %

400 - 900 > 1,5 %

The pure measurement time for the calibration of one solar cell is about 24 hours.

IEC 60904-2

PV calibration chain

PV-Module

ΙSTC

STCΙ

0,1%

< 0,01%

0,5%

Cryogenicradiometer

Standard Detector

Reference solar cell

Laser Current and Voltage Measurement

DSR Facility

Source

Detector

Facility

Monochromatic + Bias radiation

IV-CharacteristicsSolar simulator

Legende:

λ, Ε

Φ, P

λ

Εs (λ),

Φs (λ)

Ε

Oerlikon

Standard Test Conditions

• Reference solar spectrum AM1,5

• Irradiance ESTC = 1000 W/m²

• Cell-Temperature (25°C)

• Angular distribution important, but not defined

The calibration procedure must take into account these STC according to IEC 60904-3.

EMRP Project PhotoClass

From Standard Test Condition to Climate Zones From Peak-Power to Energy rating

Definition of new Standards (IEC 61853 series) Task of PTB: • Metrological background • Building up measurement capabilities for new measurement tasks

Metrological background

,NormPhotocurrent: ( ) d( )E sI λ λλ λ= ⋅∫

Reference solar spectrum AM1.5 according to IEC 60904-3:2008

Spectral responsivity of different solar cells

200 400 600 800 1000 1200 1400 1600 1800Wavelength / nm

2468 135Photon energy / eV

0,0

0,2

0,4

0,6

0,8

Abso

lute

spec

tral r

espo

nsiv

ity, s

/ AW

-1

η = 100% c-Si

GaInAs

CdTePoly-Si

CIS

a-Si GaInP

Ge Component Cell

400 600 800 1000 1200Wavelength, λ / nm

0

500

1000

1500

2000

2500

Spec

tral i

rradi

ance

Eλ /

mW

m-2

nm

-1

AM1.5 (IEC 60904-3:2008)

Solar cell

Bias radiation E b

Modulated monochromatic radiation, measured with Ref.-PD

∆E(λ)

Ib + ∆Isc(λ, Eb)

DC-Multimeter + Lock-In-Amplifier

DSR-Method Differential Spectral Responsivity

0 20 40 60Time t

ms0

2

4

6

8

10

Irrad

iance

E

: Monochromatic + bias radiation: Bias radiation

IEC 60904-4

x,y,z-Table

Monochromator

Optics (Lenses, Apertures, Monitor phodiode)

Biasradiator

Φ-θ-Goniometer

Pulse-to-CW Convertor

(Fiber)

Chopper

Climate Chamber

Lasersystem (Ti:Saphir Laser, OPO, SHG, THG, FHG)

Electronic

Compact Array Spectroradiometer

Design of the new Laser-DSR Facility

Calibration objects Reference solar cells

200 400 600 800 1000 1200 1400 1600 1800Wavelength / nm

2468 135Photon energy / eV

0,0

0,2

0,4

0,6

0,8Ab

solu

te sp

ectra

l res

pons

ivity

, s /

AW-1

η = 100% c-Si

GaInAs

CdTePoly-Si

CIS

a-Si GaInP

Ge Component Cell

Component solar cells

Industry solar cells

Determination of the Electrical Power using IEC 60904-4

0 200 400 600Voltage V

mV

-150

-100

-50

0

50Cu

rrent

I / m

A

-40-20

0204060

Elec

trica

l Pow

er P

/ m

W

Energy-generation

Energy-consumption

Isc

VOV

0 200 400 600Voltage V

mV

-150

-100

-50

0

50Cu

rrent

I / m

A

-40-20

0204060

Elec

trica

l Pow

er P

/ m

W

Energy-generation

Energy-consumption

IMPP

VMPP

PMPP =Pelektrisch

Isc

VOV

Maximum-Power-Point

0 200 400 600Voltage V

mV

-150

-100

-50

0

50Cu

rrent

I / m

A

-40-20

0204060

Elec

trica

l Pow

er P

/ m

W

Energy-generation

Energy-consumption

IMPP

VMPP

PMPP =Pelektrisch

Isc

VOV

Maximum-Power-Point

IUP ⋅=

Realisation und maintainance of the „World Photovoltaic Scale“

NREL

PTB

TIPS

AIST

Conclusion and Outlook

o PV is a 50 billion/year market

o DSR method takes the IEC 60904-3 into account and is explained in IEC 60904-4

o PTB ensures the traceability of reference solar cells

o PTB has developed the next-generation of the DSR facility with world-wide lowest measurement uncertainty: LASER-DSR

o It is a multipurpose spectral comparison facility. s = s(λ, E, fChopper, T, x, y, z, ϕ, θ)

o One application: Energy rating

o Future development: Calibration of reference modules