15 n.ferretti ok

1 N. Ferretti, Investorentag PI-Berlin, 30.10.20131 N. Ferretti, BifiPV Workshop, 26.05.2014

Nicoletta Ferretti, Giulia Mancini, Juliane Berghold, Paul Grunow (PI-Berlin)[email protected], Tel.: +49 30 8145264-119

PI Photovoltaik-Institut Berlin AG, Wrangelstraße 100, 10997 Berlin

Power measurements of bifacial

modules

mailto:[email protected]


Content

• The output power of bifacial modules in the field depends on the albedo Difficulty for energy yield predictions.

• STC measurement of bifacial module outdoor and in the lab taking albedo impact into account

Measurements at different and defined backgrounds.

• Outdoor power logging of a bifacial and a standard module as reference.

• Comparison of specific energy yields with respect to Pmax of bifacial module.

• Conclusions and outlook.


Bifacial modules

The output power depends on the albedo (reflection ratio from the ground) Difficulty for energy yield predictions.

No standards for I-V curve measurement at STC of bifacial modulesBifacial modules can not be compared and economically evaluated.


Field Installation

Field installation in Germany, Albedo 64%, Sanyo HIT-DNKHE1: 70% back-to-front efficiency, Sanyo data sheet 04/2010

Sanyo bifacial: 24% more energy yield compared to own standard module.

Need to define Pmax evaluation for energy yield prediction and for economical

evaluation of the bifacial modules.


Outdoor STC: Pmax vs. background

Pmax measured at the flasher by covering the not measured side by a black foil:Pmax Front=236 W

Pmax Back= 189 W

Bifaciality=79%

Pmax is changing depending on the background

Height=55 cmAngle= 30°Area background: 7m x 5m


Indoor STC

Background for bifacial modules(2.6 m x 3.4 m )

Background Albedo Ground

Grey 25% GrassSilver 33% SandWhite 58% Snow

Albedo measured with a cell at the flasher

[Pasan manual SS3b] No-reflecting walls

Bifacial module


STC comparison Outdoor/flasher

BackgroundPmax Outdoor

(W)Pmax Flasher

(W)Deviation

(%)

WHITE 282.9 285.1 -0.8

SILBER 274.3 271.3 1.1

GREY 265.0 268.6 -1.3

Reference 251.6 251.9 -0.1

Repeatability bifacial outdoor=0.9%Repeatability Reference outdoor=0.5%Uncertainty Pmax Flasher =2.9%

A standard module is also tested both outdoor and at the flasher as reference.


Bifacial modules measurements at flasher

Producer Pmax front (W)

Bifaciality (%)

a1 287.6 54.6a2 285.1 53.0a3 284.2 52.7b1 255.4 91.6b2 255.8 91.4b3 255.8 91.5b4 255.0 91.6

c1 246.9 76.5

c2 247.2 76.9

c3 79.90 79.1

The Pmax deviation measured with defined albedo (white/grey background) is not directly related to the evaluated bifaciality.

Single side measurents covering the not illuminated side with a black foil.

Pmax measurements with background

[Nsolar project results]


Outdoor power logging

Height=30 cmAngle= 25°Area white background: 7m x 5m

Outdoor power logging performed for both the reference and the bifacial module Specific yields comparison to evaluate if for bifacial modules Pmax measured at a defined albedo is suitable for energy yield predictions.

Reference module installed with same conditions.


Specific Yield comparison

DaysSpec. Yield Bif. vs.

Spec. Yield Ref. (%)

11-18 Dec -5.26-13 Jan -1.81-21 Feb -1.3

3-7 Mar -2.5

26 Jan

Snow+1.6

4 Feb Direct Irrad.,

max 800 W/m²+0.9

Specific Yield (KWh/KWp) comparison of bifacial module with reference module.Bifacial Pmax with white background = 285 W

Diffuse Irrad. > Direct Irrad. (except 4 Feb.)


Irradiance December and January

DaysBif. vs.

Ref. (%)

11-18

Dec-5.2

6-13

Jan-1.8

Specific yield comparison


Irradiance February and March

DaysBif. vs.

Ref. (%)

1-21

Feb-1.3

3-7

Mar-2.5

Specific yield comparison


Conclusions and outlook

• Measurement of a bifacial module at STC outdoor under different albedos (up to +20% on Pmax).

• Pmax value measured outdoor reproduced at the flasher at defined backgrounds.

• Comparison of specific yields of a standard module with the bifacialgood match when considering the Pmax value measured with background.

• Next step: Comparison of measured energy yield with simulation results.

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