Seasonal and Tilt Angle Dependence of Soiling Loss Factor

170 Pages·2017·4.45 MB·English

Seasonal and Tilt Angle Dependence of Soiling Loss Factor and
Development of Artificial Soil Deposition Chamber Replicating Natural Dew Cycle
by

Shalaim Virkar

A Thesis Presented in Partial Fulfillment
of the Requirements for the Degree
Master of Science

Approved June 2017 by the
Graduate Supervisory Committee:

Govindasamy Tamizhmani, Chair
Devarajan Srinivasan
Joseph Kuitche

ARIZONA STATE UNIVERSITY
August 2017
ABSTRACT
This is a two-part thesis. Part 1 presents the seasonal and tilt angle dependence of soiling
loss factor of photovoltaic (PV) modules over two years for Mesa, Arizona (a desert
climatic condition). Part 2 presents the development of an indoor artificial soil deposition
chamber replicating natural dew cycle. Several environmental factors affect the
performance of PV systems including soiling. Soiling on PV modules results in a
decrease of sunlight reaching the solar cell, thereby reducing the current and power output.
Dust particles, air pollution particles, pollen, bird droppings and other industrial airborne
particles are some natural sources that cause soiling. The dust particles vary from one
location to the other in terms of particle size, color, and chemical composition. The
thickness and properties of the soil layer determine the optical path of light through the
soil/glass interface. Soil accumulation on the glass surface is also influenced by
environmental factors such as dew, wind speeds and rainfall. Studies have shown that soil
deposition is closely related to tilt angle and exposure period before a rain event. The first
part of this thesis analyzes the reduction in irradiance transmitted to a solar cell through
the air/soil/glass in comparison to a clean cell (air/glass interface). A time series
representation is used to compare seasonal soiling loss factors for two consecutive years
(2014-2016). The effect of tilt angle and rain events on these losses are extensively
analyzed.
Since soiling is a significant field issue, there is a growing need to address the problem,
and several companies have come up with solutions such as anti-soiling coatings,
automated cleaning systems etc. To test and validate the effectiveness of these anti-
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soiling coating technologies, various research institutes around the world are working
on the design and development of artificial indoor soiling chambers to replicate the natural
process in the field. The second part of this thesis work deals with the design and
development of an indoor artificial soiling chamber that replicates natural soil deposition
process in the field.

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To,
My parents for their unyielding belief, my sister and brother-in-law for their love and
constant support.

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ACKNOWLEDGMENTS
I would like to thank Dr. Govindsamy Tamizhmani and Dr. Joseph Kuitche for giving me
an opportunity to work at Photovoltaic Reliability Lab. Working at the lab has opened me
a plethora of opportunities in the photovoltaic industry. Dr. Mani has been a constant
source of motivation and inspiration. My sincere thanks to Dr. Devarajan Srinivasan for
agreeing to serve on my thesis committee. Special thanks are due to Sai Gomath who
helped me with the indoor soil deposition chamber. The culmination of this thesis can be
significantly attributed to his qualities of being an excellent team player. I would like to
thank Sai Tatapudi for his help and insight throughout the project. In addition, I would like
to thank Jose Cano for being extremely approachable and helpful with all my queries.

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TABLE OF CONTENTS
Page
LIST OF TABLES ............................................................................................................. ix
LIST OF FIGURES ........................................................................................................... xi
PART 1 ............................................................................................................................... 1
SEASONAL AND TILT ANGLE DEPENDENCE OF SOILING LOSS FACTOR ........ 1
CHAPTER
1.0 INTRODUCTION ............................................................................................ 1
1.1 Background ..................................................................................... 1
1.2 Scope of Work ................................................................................ 4
2.0 LITERATURE REVIEW ................................................................................. 5
3.0 METHODOLOGY ........................................................................................... 7
4.0 RESULTS AND DISCUSSIONS ................................................................... 10
5.0 CONCLUSIONS............................................................................................. 37
6.0 RECOMMENDATIONS ................................................................................ 40
PART 2 ............................................................................................................................. 41
DEVELOPMENT OF ARTIFICIAL SOIL DEPOSITION CHAMBER REPLICATING
NATURAL DEW CYCLE ............................................................................................... 41
CHAPTER
1. INTRODUCTION ............................................................................................ 41
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CHAPTER
Page
1.1 Problem Statement ........................................................................ 41
1.2 Objective ........................................................................................ 42
2. LITERATURE REVIEW ................................................................................. 43
3. METHODOLOGY ........................................................................................... 58
3.1 Arizona Road Dust (ISO 12103-1 A2 Fine Test Dust) ....................... 58
3.2 Construction of Monocrystalline Silicon Modules .......................... 59
3.3 Heating and Cooling – Peltier Elements .......................................... 60
3.5 Humidifier ......................................................................................... 62
3.7 Soil Dispensing Compartment ......................................................... 63
3.9 Humidity and Temperature Sensor .................................................. 64
3.10 H Bridge to Reverse Polarity ............................................................ 65
3.10 Thermally Conductive Adhesive ...................................................... 66
3.11 Mounting of 2 Thermoelectric Elements Assembly ......................... 68
3.12 Setup and Assembly .......................................................................... 69
3.12.1 Setup and Assembly – 2 Thermoelectric Element Method 69
3.12.2 Setup and Assembly – 4 Thermoelectric Element Method 69
3.13 Soil Density Measurement ............................................................. 70
3.14 Isc Measurement Using Solar Simulator ........................................ 71
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CHAPTER
Page
3.15 Validation and Testing ...................................................................... 72
3.16 Working and Initial Testing: ........................................................ 75
4 RESULTS AND DISCUSSION ........................................................................ 77
4.1 2 Thermoelectric Element Method (1 Chamber 2 Peltier)................ 77
4.1.1 Initial Testing and Characterization ........................................ 77
4.1.2 Process Parameter Optimization .............................................. 81
4.1.3 Optimization of Baking Time: ............................................. 82
4.1.4 Optimization of amount of Soil: .............................................. 85
4.1.5 Optimization of Humidity ......................................................... 89
4.1.6 Optimization of soil settling time ............................................ 91
4.1.7 Optimized Cycle for 1 Chamber (2 Thermoelectric Elements)
Method: ................................................................................................. 93
4.1.8 Discussion: .................................................................................. 93
4.2 4-Thermoelectric Elements Method: (1 Chamber 4 Peltiers) ............. 94
4.2.1 Initial testing and Characterization .......................................... 94
4.2.2 Optimization of Cooling time ................................................ 97
4.2.3 Optimization of Baking time .................................................. 107
4.2.4 Optimization of Humidity ....................................................... 111
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CHAPTER
Page
4.2.5 Optimization of Settling Time ............................................... 115
4.2.6 Optimized Cycle for 1 Chamber (4 Thermoelectric Elements)
Method: ............................................................................................... 116
4.2.7 Soil density measurements and Optical characterization for
optimized method: ............................................................................. 117
4.2.8 Soil Density and Uniformity Measurements ........................ 120
4.3 Design of Experiments ...................................................................... 124
4.4 Soiling Results with Collected Soil .................................................. 130
4.4.1 Arizona Collected Soil: ........................................................... 130
4.4.2 Denver Collected Soil ............................................................. 133
4.4.3 San Francisco Collected Soil: ................................................ 135
4.4.4 Soil deposition with under 2g of Arizona fine dust ............. 140
5 CONCLUSIONS.............................................................................................. 142
5.1 Future Recommendations: ................................................................ 145
REFERENCES ............................................................................................................... 146
APPENDIX
A SOIL CHARACTERIZATION AND COLLECTION................................... 149

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LIST OF TABLES

Table Page
1: Rain Days for Oct 2015 – Sept 2016 ............................................................................ 26
2 –Drought Periods ........................................................................................................... 26
3 – Summary of Drought Period Analysis ........................................................................ 27
4-Summary of Soiling Losses/Day for Zero Degree Tilt.................................................. 37
5- Rainfall for 2015 and 2016 ........................................................................................... 37
6-Comparison of Rain Days 2015 and 2016 ..................................................................... 37
7 – Comparison of Outdoor Soiling (0o tilt; Feb2-Apr7) for indoor AZ reference soil
deposition .......................................................................................................................... 38
8- Isc loss for 144cm2 Poly-Si mini module .................................................................... 48
2
9- Isc loss for 233cm Mono-Si single cell coupon ......................................................... 48
10-Composition of AZ dust (ISO 12103-1, A2 fine test dust nominal 0-80 micron size,
Powder Technology Inc., Burnsville, MN, USA). ........................................................... 59
11- Humidity Controller Specifications: ........................................................................... 64
12: Parameters for Initial Testing ..................................................................................... 78
13 – Isc values after each soiling cycle ............................................................................. 79
14 - Parameters kept Constant for cycle 1 Cooling Optimization .................................... 98
15 – Cycle 2 Optimization of Cooling Time .................................................................. 100
16 - Cycle 3 Optimization of Cooling Time ................................................................... 102
17 -Parameters kept constant for Optimization of Baking Cycle 1: ............................... 108
18- Parameters kept constant for Humidity Optimization Cycle 1 ................................. 111
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