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

6

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

9

2. EXPERIMENTAL

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

ANALYSIS OF FRONT SIDE MODULE PARAMETERS WHICH

COULD AFFECT THE COMPARATIVE ENERGY GENERATION

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

ANALYSIS OF FRONT SIDE MODULE PARAMETERS WHICH

COULD AFFECT THE COMPARATIVE ENERGY GENERATION

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

3. TEST RESULTS

SIMULTANEOUS MONITORING OF MONO AND BIFACIAL MODULES

12

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

14

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

16

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

18

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

20

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

ROOFTOP TEST FIELD IN GEILENKIRCHEN

3. TEST RESULTS

21

ROOFTOP TEST FIELD IN GEILENKIRCHEN

3. TEST RESULTS

22

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

23

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

24