04 eisenberg b solar

Naftali Eisenberg, Lev Kreinin, Ninel Bordin, Asher Karsenty, Avishai Drori

Konstanz, Apr. 2012

OUTDOOR BIFACIAL MODULE CHARACTERIZATION:

ENERGY GENERATION AND GAIN

Outline

1. INTRODUCTION

2. EXPERIMENTAL

2

2. EXPERIMENTAL

3. TEST RESULTS

4. CONCLUSIONS

THE BEAUTY OF BIFACIAL SOLAR MODULE IS IN THE

COLLECTION OF ADDITIONAL ENERGY BY THE CELL BACK

1. INTRODUCTION

3

FACTORS AFFECTING THE BACK CONTRIBUTION

1. ILLUMINATION CONDITIONS

1. INTRODUCTION

4

• Sun elevation

• Diffused/global radiation ratio

• Albedo of underlying surface

2. MODULE AND SYSTEM PARAMETERS

• Back/front efficiency

1. INTRODUCTION

FACTORS AFFECTING THE BACK CONTRIBUTION

5

• Back/front efficiency

• Module inclination (tilt)

• Distance between rows

• Stand alone/field system

• Module elevation above underlying surface

• Distance between modules in the row

1. INTRODUCTION

ROOFTOP TEST FIELD IN JERUSALEM

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TEST SYSTEM

Panel 1

and Mount

Panel 2

and Mount

Global

Irradiance

pyranometer

Diffuse

Irradiance

pyranometer

Wind

speed

sensor

Panel

temperature

sensors

Reference cells,

Pyranometers

Meteorological station

1. INTRODUCTION

pyranometer pyranometer sensor sensorsPyranometers

Data Logger

Laptop >>> Database >> Website

Multiplexer

IV

Tracers

Input Irradiance

Profile

Measurement

Sensor Array

• Module orientation in a fixed position: south, tilt: 300. The distances between

rows (S-N) and between modules (E-W) were 150 and 20 cm. Elevation of the

module lower edge was 70 cm.

• The albedo was ~50 %

• I-V characteristics of a bifacial and a mono-facial modules inside the "field“ were

monitored simultaneously as well the module temperature and direct and

1. INTRODUCTION

8

monitored simultaneously as well the module temperature and direct and

diffused radiation.

• All the Energy data were normalized by nominal front power Pmax

of the given module, i.e. we measured : kWh (module) / kWp (front)

BIFACIAL MODULE GAIN OVER MONOFACIAL:

G = { kWh/ kWp, front} bifacial - { kWh/ kWp, front} monofacial

ANALYSIS OF FRONT SIDE MODULE PARAMETERS WHICH

COULD AFFECT THE COMPARATIVE ENERGY GENERATION

2. EXPERIMENTAL

1. How to cover the back side for perfect front characterization

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2. EXPERIMENTAL

2. Front illumination is not a discriminating factor in our test site



10

a) b)

Front power as a function of irradiance for a mono-facial (a) and a bifacial (b) module

2. EXPERIMENTAL

3. Incident angle is not a discriminating factor in our site



11Angular dependence of short circuit current for mono-facial and bifacial modules

3. TEST RESULTS

SIMULTANEOUS MONITORING OF MONO AND BIFACIAL MODULES

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Daily energy gain of a bifacial vs. a mono-facial module

3. TEST RESULTS

SIMULTANEOUS MONITORING OF MONO AND BIFACIAL MODULES

13Monthly energy gain of a bifacial vs. a mono-facial module

3. TEST RESULTS

HOURLY DEPENDANCE OF ENERGY OUTPUT FOR MONO

AND BIFACIAL MODULES IN A FIELD

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Monitoring for sunny day 01.05.2011 with

diffused/global radiation ratio 11 %

3. TEST RESULTS

HOURLY DEPENDANCE OF ENERGY OUTPUT FOR MONO

AND BIFACIAL MODULES IN A FIELD

15

Monitoring for cloudy day 17.09.2010 with

diffused/global radiation ratio 88 %

3. TEST RESULTS

NON UNIFORMITY OF BACK IRRADIANCE VS. PANEL ELEVATION

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Back side irradiance for a 30o tilted module (30.05.10)

•Albedo 0.55•Global Irradiation 1006 W/m2

•Diffuse Irradiation 111 W/m2

Elevation 58 cm

Elevation 108 cm

Elevation 8 cm

3. TEST RESULTS

NON UNIFORMITY OF BACK IRRADIANCE VS. PANEL ELEVATION

17Back side irradiance E (min, max) and max power gain vs. module elevation

3. TEST RESULTS

EFFECT OF DIFFUSED/GLOBAL RADIATION RATIO

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Daily energy gain of a bifacial vs. a mono-facial module as a function of

diffuse to global radiation ratio for two seasonal sun positions

Berlin-Dahlem, Tilt=30°, NS=2.32m. BIFACIALITY 70 %

Annual Bifacial Gain and Equivalent Cell Efficiency

for various Field Designs

ROOFTOP TEST FIELD IN GEILENKIRCHEN

3. TEST RESULTS

• Bifacial modules vs.

monofacial reference modules.

• Inverter - x2 1.5kW units, per

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System monitored by Fraunhofer/ISE

• Inverter - x2 1.5kW units, per

string

• Az = 145 deg

• Ground reflectance - 78%

• Tilt=15°

• Height = 30 cm

• NS= 2.5m


3. TEST RESULTS

21


3. TEST RESULTS

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4. CONCLUSIONS

THE ENERGY GAIN IN USING BIFACIAL MODULES IS HIGLY

DEPENDANT ON :

• DIFFUSE TO GLOBAL RADIATION RATIO,

• SEASONAL AND TIME-OF-DAY SUN POSITION

• ALBEDO OF UNDERLYING SURFACE

• MODULE ELEVATION AND TILT, DISTANCE BETWEEN MODULES

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TYPICAL ANNUAL GAIN MEASURED IN GERMANY

WAS ABOVE 23 %.

A BIFACIAL MODULE WITH FRONT POWER OF 250 W

WILL GENERATE ENERGY AS A STANDARD MODULE OF 307 W

04 eisenberg b solar

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