PV-Basics - DUT
Transcript of PV-Basics - DUT
1
PV Installer for
South Africa
PV-Basics
2
Agenda
Introduction
• Trainer
• History of Photovoltaics
• Motivation
• Types of systems
Solar irradiation
• Solar energy
• Sun path, effects
• Measurement
Solar cells
• Design and function
• Cell types and production
Solar modules
• Production
• Electrical characteristics
• Quality / certificates
• By-pass diodes
Shading
• Basics
• Site survey
• Types of shading
• Shading analysis
3
Name
Organisation
Please tell us your name, your job, the experience you already have with PV
What do you expect to learn during this course
Introduction
Introduction of Trainer and Participants
4
One of the scientist in the Bell Laboratories was
Adolf Goetzberger, founder of the Fraunhofer
Institute of Solar Energy (ISE) and an Honorary
President of the DGS.
The first silicon solar
cell was developed
and built by Bell
Laboratories in
Murray Hill, USA in
1954 by Chapin,
Fuller and Pearson.
The first cell had an efficiency of 6%.
The efficiency was soon increased to
10%.
Soon after Bell Laboratories a Japanese
laboratory managed to build silicon cells
too. Introduction
The first silicon solar cells
5
The fourth satellite "Vanguard I" started its journey in
March 1958 as a solar powered mini satellite. With only
1,5 kg and 16 cm in diameter it was a flea compared to
Russian Sputnik - but a very persistent one.
“Vanguard I” survived for 6 years and beeped on 108 MHZ,
a frequency preferred for space applications.
The 6 modules consisted of one solar cell with an
efficiency of 10,4 % which supplied a mercury battery.
Early commercial use for small
radios, pocket calculators and toys
Introduction
First applications: outer space and small devices
6
1990 : 1 000 Dächer Programm (1 000 roof tops program)
70% of component and installation costs was subsidised
Energy that was fed into the grid was not paid, meters were wired to measure
own consumption
Yield was less important because subsidies were granted
This was also the start of the serial production of high quality components
Introduction
NEG1600
Subsidies in Germany for PV roof top systems
7
Since 2000: EEG “Erneuerbare Energien Gesetz” (German Renewable
Energy Act)
This offered a cost-covering feed-in tariff which was fixed for 20 years plus
the year of installation. Tariff depends on year of commissioning.
Started with €0,506 = R4,34 /kWh. Average energy cost for consumers at that
time €0,134 = R1,94. Therefore systems were designed for max. feed-in.
Utility scale parks became economically interesting.
Today's feed in tariff €0,1231 = R1,79 /kWh. The average energy cost today
€0,2869 = R4,16. i.e. own consumption is most important
Introduction
Subsidies in Germany for PV roof top systems
8
More than 100 countries developed renewable energy acts based on the
German EEG
Often grid companies and other public or private institutions object because
they fear the changes Introduction
German EEG as blueprint for other countries
9
Energy production
High voltage, medium voltage and low
voltage distribution
Energy sales
Municipalities buy energy from Eskom
Regional distribution
Energy sales
Regulatory authority e.g. for electricity tariffs,
grid access…
Introduction
SA: Production, distribution and sale of electricity
10
National Energy Act:
Defines basic goals
Integrated Energy Plan (IEP):
Political plan to achieve the goals defined in the National Energy Act
Electricity Regulation Act
Licensing of generation and the distribution of energy
NRS 097-2-1:2010 and NRS 097-2-3:2014
Grid interconnection of embedded generation. Specification issued by the
Standardisation Section of Eskom
SANS 10142
The wiring of premises, Low-voltage installations
The legal situation in South Africa is often not clear. Regulations and standards
for PV installations are incomplete.
e.g. In Cape Town the municipality assumes that for embedded generators below
1 MWp generating license from NERSA is not required, as long as the client
remains a net consumer of electricity (i.e. consumption is higher than generation) Introduction
Important Acts and Legal Regulations in SA
11 Introduction
12 Introduction
13 Introduction
14
1 € = 14,5 ZAR
Todays price in Germany 1 270 € = 18 500 ZAR
Introduction
15
Commercial: 14,000 - 18,000 ZAR
Residential: 25,000 - 30,000 ZAR
PV Moduls 55%
Inverter 15%
Mounting structure 5%
BOS, installation 25%
Prices for residential installations in South Africa are currently 35% higher than
prices in Germany. The cost of living in South Africa is at 53% compared to
Germany.
Introduction
Actual Price in South Africa (2016)
16
Grid-connected BIPV
Grid-connected roofs
PV power plants
Stand alone systems industrialised countries
Stand alone systems developing countries
Consumer electronics, communication
Ma
rke
t sh
are
[%
]
2002 2006 2008 Prognosis 2020
So
urc
e E
PIA
Introduction
Market share of different applications
17
Backup systems
Stand alone systems
Residential grid connected systems Utility scale PV parks
Introduction
(Future) PV Market in South Africa
18 Solar Photovoltaic Mounter
Solar Photovoltaic
Service Technician
Solar Photovoltaic Installer
Introduction
PV Education according QCTO Curriculum
19
Knowledge Modules
Workplace fundamentals
Tools, equipment and
materials
Electricity and electronics
Wire ways, wiring and
earthing
Electrical supply systems
and transformers
Protection systems and
lightning protection
Renewable energy
Components of PV
systems
Designing and installing
grid-connected and stand-
alone PV systems
Practical Skill Modules
Mitigate and respond to
hazards associated with
PV system installation and
maintenance
Working at heights
Use of tools, measuring
instruments and equipment
Design, construct and test
electrical and electronic
circuits
Plan and prepare for the
installation of a PV system
Install the mechanical
components of a PV system
Install the electrical
components of a PV system
and interconnect the system
Work Experience Modules
Structured planning and
communication
processes in the
workplace
Processes to plan and
prepare for installation
and commissioning of
PV systems
Processes to install
mechanical components
of PV systems
Processes to install
electrical components of
PV systems and to
commission the systems
Introduction
Solar Photovoltaic Installer QCTO Curriculum
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For the safe operation of a PV system and to gain
sufficient yield a high standard of quality is
essential for...
1. Components
2. Planning, sizing
3. Mechanical and electrical installation
4. Commissioning
5. Operation & maintenance, repairs
In the QCTO curriculum for the Solar Photovoltaic
Installer points 1 to 4 are covered.
Operation and Maintenance is only covered in the
QCTO curriculum for the Solar Photovoltaic
Service Technician. These are important topics for
the installers as well because for them it is
meaningful to maintain and repair the PV system
they planned, installed and commissioned
Introduction
QCTO PV Installer: what’s included, what’s missing
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Source: BMU 2009
World w
ide e
ne
rgy c
onsum
ption
Coal
Cru
de o
il
Natu
ral gas
Ura
niu
m
Win
d
Bio
mass
Wa
ter
Non renewable energies
outer cube: renewable
energy per year
inner cube: technically feasible / usable
amount of energy per year
solar irradiation on
the continents
Wave e
nerg
y
Tid
al e
ne
rgy
Geoth
erm
al
Introduction
Annual Solar Energy compared to other sources
22 Introduction
Carbon Dioxide (CO2) level in the air is at its highest in 650,000 years
Global temperature has risen by 1.7°C since 1880.
Nine of the ten warmest years were recorded after 2000
Arctic ice is melting, in 2012 the summer sea ice shrunk to it’s lowest extent
on record
Between 1995 and 2005 the Greenland ice losses doubled
Global average sea level has risen almost 18 cm in the last 100 years,
it is currently rising by about 3,4 mm per year
Climate Change
23
In the 2015-2016 rainy season
central South Africa had less
than half of the normal rainfall.
This poor rainy season
followed a below-average
2014-2015 season which led
to 2015 having the lowest
annual total rainfall on record
Most likely the shortages in
public drinking water supply
will become normal
Water consumption of power
plants differ a lot
Especially PV und Wind need
less water
Introduction
Climate Change Effects in South Africa
24
Simple systems can operate with a thermal
collector and PV without need of other energy
If waste heat or sufficient electricity (e.g. PV) is
available, Multi-Stage flashing (MSF) low
operating temperature desalination is an
efficient solution
Solar desalination is already competitive
Source: Vista
Source: dii-eumena.com
Introduction
Water Desalination
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PV-installations with or
without storage
small devices
DC-AC
system
Hybrid
installations
DC system
with wind
turbine
with
cogeneration
engine
with diesel
generator
Grid-tied systems
connected to
domestic grid
Off-grid systems
connected to public
grid
Introduction
Overview different types of PV Systems
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1. PV array
2. Combiner box
3. DC cabling
4. DC circuit breaker
5. Inverter
6. AC cabling
7. Electricity meter cabinet
with meter, distribution
and mains connection,
safety devices
Introduction
Full feed in or own
consumption (depends
on the feed in tariff)
In SA mainly for own
consumption because
of legal situation
(limited export may be
allowed)
Grid-tied PV System
27 Introduction
1. PV array
2. Combiner box
3. DC cabling
4. DC circuit breaker
5. Inverter
6. AC cabling
7. Electricity meter cabinet
with meter, distribution
and mains connection,
safety devices
8. Batteries and charge
controller
8 Same meter wiring for
own consumption with
or without storage
In SA also reverse
power blocking
instead of bidirectional
meter
Grid-tied PV System with storage
28 Introduction
8
1. PV array
2. Combiner box
3. DC cabling
4. DC circuit breaker
5. Inverter
6. AC cabling
7. Electricity cabinet with
safety devices
8. batteries and charge
controller
8 No meter necessary
Grid provider may
demand a declaration
that the system is not
grid connected
Standalone PV System
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Energy generation Energy consumption
Load • Application/Consumers
• DC/AC
• Hours
• Daily / weekly
• time of consumption
• during night
• seasonal changes
• supply security
Site inspection • Location
• Inclination
• Orientation
• Mounting situation (e.g.
shading...)
Irradiation and
temperature
System design System voltage
DC System
DC/AC System
Mini grid
Hybrid system
Basic design data for off-grid system
Performance and
consumption data
Balance between demand and supply
30 Introduction
Energy must feed into medium (MV) or high voltage (HV) grid and is
transported to the loads
Most often large central inverter
Possible feed in point must be considered
Utility Scale PV Plant
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Own consumption or full feed-in
Most often the existing feed-in point is suitable
Owner of the PV system is not necessarily the owner of the building
Introduction
Large Roof Top PV System
32
xx
Calculator
Introduction
Solar lamp
Solar charger
Examples for small Off-Grid Devices
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Rural areas: high cost for grid connection
Urban areas: for some particular installations
costs for small stand alone systems are lower
than for a grid connection
Higher flexibility for the place of installation
Introduction
Small Standalone PV Systems
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E-Mobility reduces noise
The smog problem in the cities can
be reduced
For many purposes E-freight-bikes
are the best economical and
ecological solution
In the future the necessity of
storage for supplementing the grid
may be provided by the internal
storage of E-cars Introduction
Mobility with PV (direct / indirect)
35 Introduction
Electification of Rural Areas
36
Agenda
Introduction
• Lecturer
• Photovoltaic history
• Motivation
• Types of systems
Solar irradiation
• Solar energy
• Sun path, effects
• Measurement
Solar cells
• Design and function
• Cell types and production
Solar modules
• Production
• Electrical characteristics
• Quality / certificates
• By-pass diodes
Shading
• Basics
• Site survey
• Types of shading
• Shading analysis
37 Irradiation
Solar constant E0: 1,367 W/m2
describes an average value of the irradiation outside the atmosphere
Orbit of the Earth
38 Irradiation
Air Mass (AM) and Sun’s Elevation Angle
(Space) (Space)
(Space) (Space)
Rome Cairo
Singapore Sydney
North South North South
North South North South
39 Irradiation
Components of Global Irradiation
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Surface Albedo Surface Albedo
grass (July, August) 0.25 tarmac 0.15
lawn 0.18 … 0.23 forest 0.05 … 0.18
dry grass 0.28 … 32 heather and sandy areas 0.10 … 0.25
untilled fields 0.26 water (S > 45°) 0.05
barren soil 0.17 water (S > 30°) 0.08
gravel 0.18 water (S > 20°) 0.12
concrete clean 0.30 water (S > 10°) 0.22
concrete eroded 0.20 fresh snow 0.80 … 0.90
cement clean 0.55 old snow 0.45 … 0.70
Albedo of various surfaces
Irradiation
Ground Reflexion - Albedo
41
Irradiance [W/m²] On cloudy days the irradiation is
mainly diffuse, i.e. lower energy yield
With clear skies the irradiation is
diffuse and direct with the highest
daily energy yield
The highest short time irradiation
occurs with a mostly clear sky with
only few bright clouds, daily energy
yield is reduced
Irradiation
Mainly diffuse irradiance Mainly direct irradiance
Influence of Clouds on Irradiation
42 Irradiation
Sunlight Spectrum
43
Shift to red increasing towards evening (Sunset) Irradiation
Sunlight Spectrum at different Elevation Angles
44 Irradiation
Sunlight Spectrum with Cloud Cover
45
No data
Irradiation
Average Global Annual Solar Irradiation in kW/m²
46 Irradiation
Annual Global Irradiation in Africa
47 Irradiation
Irradiation on Inclined Surface in South Africa
48 Irradiation
So
urc
e: M
ete
on
orm
7
Irradiation in winter (June) is still half of the irradiation as in summer
Irradiation is mainly direct
Temperature is always above 0°Celsius, wide range
Irradiation and Temperature in Johannesburg
49 Irradiation
Irradiation in summer is much higher than in Johannesburg
Irradiation in winter is far lower than in Johannesburg
Irradiation is mainly direct
Temperature is always above 0°Celsius, wide range
So
urc
e: M
ete
on
orm
7
Irradiation and Temperature in Cape Town
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αs Azimuth of the sun
α Azimuth of the array
γs Sun‘s elevation angle
β Inclination of the PV-array
PV-generator
South 0°
West 90° North 180°
East -90°
Irradiation
Angle Notation for PV
51
Northern hemisphere
Southern hemisphere
Irradiation
Sun path throughout the Year
52 Irradiation
Cape Town: Sun path diagram, rectangular
53 Irradiation
Cape Town: Sun path diagram, polar
54
A shunted solar cell almost operating at
short circuit
Measured current is proportional to
irradiation
Measurement error is reduced due to
low temperature coefficient of short
circuit current
Fast reaction on changes in irradiation
Similar spectral and low light behavior
if the same cell type is used
Also used for IV-curve measurements
Irradiation
Irradiation Sensors
55
Solar irradiation enters through two glass domes and heats a small black
plate (thermopile)
The thermocouples (thermopile sensor) underneath the plate generate a
voltage output signal proportional to the intensity of the irradiation
The spectral behaviour is almost constant
Also, the angle dependency is low
Pyranometers are slow, but very accurate (approx. +/- 0.8 %)
Irradiation
Pyranometer
56
Agenda
Introduction
• Lecturer
• Photovoltaic history
• Motivation
• Types of systems
Solar irradiation
• Solar energy
• Sun path, effects
• Measurement
Solar cells
• Design and function
• Cell types and production
Solar modules
• Production
• Electrical characteristics
• Quality / certificates
• By-pass diodes
Shading
• Basics
• Site survey
• Types of shading
• Shading analysis
57
Photo: Greek: light
Volt: Unit of electrical voltage (Alessandro Volta, Italian Physicist, 1745 –1827)
Solar Cells
Photovoltaics – Electricity from the Sun
58 Solar Cells
Extrinsic Conduction in n- and o-doped Silicon
59 Solar Cells
Space Charge Region at the p-n junction
60
1. Charge separation
2. Recombination
3. Unused photon energy
4. Reflection and shading by front contacts
Solar Cells
Structure and Function of a Solar Cell
61
cell types
crystalline silicon cells
cells with reverse
contact
monocrystalline cells
standard silicon
cells, p-doped
Power cells, n-
doped
cells with reverse
contact
spherical cells
hybrid HIT cell
thin film cells
crystalline silicon thinfilm,
micromorphous
amorphous silicon cells
copper indium diselenide
(CIS)
cadmium-telluride cells
(CdTe)
concentrating cell
polycrystalline cells
polycrystalline band
cells
(EFG, string ribbon,
dentric web)
Solar Cells
Cell Types
62
Efficiency: 15-19%
Form: round, semi quadratic,
quadratic
Size: d = 10, 12.5, 15.2 or 17.8
cm, mostly 15.2 x 15.2 cm² or
17.8 x 17.8 cm²
Thickness: 0.14 to 0.2 mm
Appearance: homogenous /
uniform
Colour: dark blue to black
Wafer + antireflection
coating + contacts Efficiency: 13-17%
Form: quadratic
Size in cm x cm: 12.5 x 12.5 ,
15 x 15 , 15.6 x 15.6 , 20 x 20
Thickness: 0.14 to 0.2 mm
Appearance: frost pattern or
homogenous
Colour: blue to dark blue
Mono- and Polycrystalline Silicon Cells
63 Solar Cells
silicon granules
polycrystalline
monocrystalline
polycrystalline
front and rear contacts add anti-reflex layer
phosphorus diffusion
block sawing
Czochralski process aligned
solidification
slicing
chamfering
Production of Crystalline Silicon Cells
64
On metallic or glas materials Copper-Indium-Diselenid (CIS)
Amorphous silicon
Cadmium-Telluride (CdTe)
Solar Cells
Thin Film Solar Cells
65 Solar Cells
66
Material Module efficiency
(Standard modules)
Area for 1 kWp
Monocrystalline rear
side contacts
20.4 % 5 m²
Monocrystalline 17% 6 to 7 m²
Polycrystalline rear
side contacts
16,6 % 6 to 7 m²
Polycrystalline 16 % 6 to 7 m²
CIS 14,5% 7 to 8 m²
CdTe 13,5 % 8 to 9 m²
Amorphous 7,5 % 13 to 15 m²
High efficiency means low area demand Rule of thumb:
1 kWp = approx. 10 m²
Solar Cells
Cell Technologies and Efficiency
67
The solar cell – a diode that becomes a current source when illuminated. I = IPh – ID
Equivalent circuit diagram (ideal model)
Solar Cells
Electrical Characteristics
68
PDPh IIII
P
S
P
D
R
IRV
R
VI
Solar Cells
Rs describes internal losses like the contact resistance.
More relevant for higher current at higher irradiation
Rp describes internal losses like recombination. More
relevant for lower current at lower irradiation
Standard Model (Single-Diode-Model)
69
STC: standard test conditions
Solar Cells
Characteristic Curves of a Silicon Solar Cell
70 Solar Cells
For the fill factor the nominal power is divided by a theoretical maximum power
given by the product of the short circuit current and the open circuit voltage
Cell failures often come with reduced fill factor. Therefore the fill factor can be seen
as a measure for quality
Parameter of a Solar Cell: Fill Factor
71
Parameter Symbol Unit Description
MPP-power PMPP Wp Peak power (maximum power point)
Efficiency η - / % Measure for the losses during the energy
conversion of the module, cell or system
Fill factor FF - / % Measure for the electrical quality
MPP-voltage VMPP V Voltage at MPP
Open-circuit
voltage
VOC V Voltage without load
MPP-current IMPP A Current at MPP
Short circuit
current
ISC A Current if both connections are linked
together
EA
IVFF
EA
IV
EA
P
P
Pefficiency SCOCMPPMPPMPP
sol
PV
Solar Cells
Parameter of PV-Modules
72
Condition Value Unit
Irradiation 800 W/m²
Air Temperature 20 °C
Wind Velocity 1 m/s
Mounting Open
back side
Solar Cells
Normal Operating Condition Temperature NOCT
The cell temperature measured under these given conditions is reported in
the data sheet as NOCT value
Low light conditions
For a given irradiation of 200 W/m² all electrical data are measured.
Sometimes a specific efficiency compared to STC is given
Behaviour beside STC Conditions
73
Vtotal = V1 + V2 + V3 + ... + Vn Itotal = I1 = I2 = I3 = constant
Solar Cells
Series Interconnection of Solar Cells
74
Itotal = I1 + I2 + I3 + ... + In Vtotal = V1 = V2 = V3 = constant
Solar Cells
Parallel Interconnection of Solar Cells
75
T = const.
Solar Cells
Irradiation Dependency of Voltage and Current
76
E = 1000 W/m²
UMPP Range module voltage V in V
mo
du
le c
urr
en
t I in
A
Solar Cells
Temperature Dependency of Voltage and Current
77
E = 1000 W/m²
Solar Cells
Temperature Dependency of Power
78 Solar Cells
Overview Temperature Dependencies
79
Good ventilation is important for cooling
Less efficiency and less energy yield with increasing temperature
Module temperature depends on type of mounting: less ventilation of
highly integrated modules
Temperature increase and yield losses
depending on the installation
Solar Cells
80
Agenda
Introduction
• Lecturer
• Photovoltaic history
• Motivation
• Types of systems
Solar irradiation
• Solar energy
• Sun path, effects
• Measurement
Solar cells
• Design and function
• Cell types and production
Solar modules
• Production
• Electrical characteristics
• Quality / certificates
• By-pass diodes
Shading
• Basics
• Site survey
• Types of shading
• Shading analysis
81
1.Cell Stringing
Automatic interconnection of
crystalline cells to substrings of
mostly 10 or 12 cells in series in
a stringer. Laying of 4 to 6
substrings for one module, in
total 60 or 72 cells. Today most
cells have 2 or 3 busbars. All
cells are in series, seldomly
strings in parallel.
Solar Modules
Module Production: Cell Interconnection
82
2. Laminating
= encapsulation between front glass and back film
material: EVA (Ethylene-Vinyl-Acetate) or other material
3. Framing: optional, but most modules are framed using hollow profiles
Aluminium frame
Glass
Sealing
EVA Cells
Tedlar film
Solar Modules
Today some manufacturer offer glass/glass instead of glass/tedlar.
Module Production: Encapsulation and Framing
83
IEC 61215 crystalline modules, respectively IEC 61646 thin film modules
visual inspection
performance under different conditions
(STC, NOCT and at T = 25°C and E = 200W/m2)
measurement of temperature coefficients
insulation test
outdoor exposure test
hot spot endurance test
thermal cycling test and UV test
humidity–freeze test
damp–heat test
robustness of terminations test
mechanical stress and twist tests
hail resistance test
Solar Modules
Cell and Module Certification
84
IEC 61730 respectively EN 61730 „Safety standards for PV-modules“
Basis for CE-label, includes protection class II test – Classification in three safety classes:
Class A: building applications (publicly accessible) for Systems > 50 V DC
voltage or 240 W, modules: protection class II tested
Class B: Power plant applications (no public accessibility), secured system,
protection class 0
Class C: low voltage applications < 50 V or 240 W, modules: protection class III
Protection class II assures
protection of people against electric shock for the entire lifetime of the modules
double or increased insulation
Solar Modules
Safety Certifications
85
Product warranty: for manufacturing and workmanship, no failures in the
specified properties and characteristics, 2 years by law, some manufacturers
offer more
Power guarantee: usually 90% of nominal power for 10 to 12 years and
80 % for 25 years
Attention: what does the power guarantee refer to, nominal power or
minimum specified power?
Example: with a power tolerance of +/- 10 % and measuring inaccuracy of
4 %, 80 % of Pmin are only 69,2 % (measurement) of Pnominal, that means real
72 to 66,5 %
The customer has the burden of proof, he has to prove the module is not
delivering enough power via acknowledged testing institute in Germany:
TÜV (up to €400 per module), Fraunhofer ISE (€200 per module)
Solar Modules
Warranties and Additional Guaranties
86 Solar Modules
87
Composition of PV Modules
Hazardous materials in PV systems
Lead (Solder)
Cadmium (Cd), bound in CdTe or CdS
Selenium (Se), bound in CIS
Crystalline silicon standard module, mass proportion [%]
glass frame EVA cells junction box back foil mass/power
62.7% 22.0% 7.5% 4.0% 1.2% 2.5% 103.6 kg/kWp
Thin film module (glass-glass module w/o back film), mass proportion [%]
glass frame EVA junction box chemical elements back foil mass/power
74.5% 20.4% 3.5% 1.1% 0.1% 0% 285.2 kg/kWp
Solar Modules
Hazardous Materials
88
Z36Z1 Z2 Z17 Z20Z19Z18 Z35
Z36Z1 Z2 Z17 Z20Z19Z18 Z35Wärme
Z36Z1 Z2 Z17 Z20Z19Z18 Z35
Solarzelle
Hot Spot
Heat
Solar cell
Solar Modules
Bypass Diodes
89
Two inner substrings are connected
to a bypass diode in the junction box
A module with four inner substrings
has two bypass diodes
Module
curr
ent in
A
Solar Modules
Shading and Bypass Diodes
90
Agenda
Introduction
• Lecturer
• Photovoltaic history
• Motivation
• Types of systems
Solar irradiation
• Solar energy
• Sun path, effects
• Measurement
Solar cells
• Design and function
• Cell types and production
Solar modules
• Production
• Electrical characteristics
• Quality / certificates
• By-pass diodes
Shading
• Basics
• Site survey
• Types of shading
• Shading analysis
91 Shading
Shading Impact on IV Curve
92
Module with three bypass
diodes
Shading
Shading and Bypass Diodes
93
Depends strongly on location and environment
Often bird droppings and foliage
In drier regions soiling due to dust is the main
loss factor
Soiling losses increase near traffic routes and
industrial plants
Higher pollution in regions with intensive
agriculture and on roofs of livestock farms
Self-cleaning depends on rainfall and
mounting situation Solar Asset Management GmbH
BSR
Shading
Temporary Shading: Pollution
94
Shading due to chimneys, dormers,
antennas, lightning protection, roof and
facade projections, ventilation pipes
Shading
Building Related Shading
95
Trees, foliage, neighbouring
buildings, aerial lines, fences
Shading
Site Related Shading
96
Verbund-Austrian Renewable Power GmbH
Shading
For open space installations unavoidable, also for tilted installations on flat
roofs
Depends also on the mounting situation
Proper planning can reduce yield losses
Mutual Shading
97
Documents for planning:
Site plan, orientation of the PV system
(also Google maps or Bing)
Construction plans of building, roof
inclination, usable area
Photos of building and surroundings
Tools for shading examination
Sketch-map
Compass, inclinometer, camera (apps
for mobile phone)
Tape measure
Shading analyser (app for mobile
phone)
Shading
Site Survey: Shading Examination
98
Determination of elevation and azimuth angle of objects
γ – elevation angle h1 – height of pv system
- azimuth angle h2 – height of shading object
d – distance between pv system and shading object
Shading
Determination of orientation of objects
Use of compass
Objects in a sun path diagram
Azimuth and orientation of characteristically points are transferred on the sun
path diagram
Geometric Shading Analysis
99
Digital camera combined with evaluation software
Viewing perspective converted by software
Horizon line created automatically, may be modified manually
and can be imported in common PV simulation software
PanoramaMaker and HorizOn: 360° panorama made from 16
single images, some apps may work similar
HoriCatcher: one picture of a spherical mirror, converted to a
panorama picture
SunEye: Camera integrated in a handheld computer,
calculation is performed at once.
All systems: sun path diagram can be transferred to a
simulation program
Shading
Shading Analyser
100
Area exploitation factor Shading angle
Distance
cos1
sinarctan
f
f
d
bf
sin
)180sin( bd
b = module width
d = module row distance
d1 = rack distance
h = tilt height
= tilt angle
= shading angle
Shading
Aim: Cost-effective optimization between area utilization, irradiation increase and
losses due to mutual shading
Area Exploitation Factor
101
dd
daa
s
sopti
108
An umbra may be avoided
with a distance of at least
108 times the diameter of
the shadow casting object
Shading
Umbra
Penumbra
In most cases on flat roof shading due to lightning
protection systems cannot be avoided. Nevertheless
it is important to avoid an umbra.
How to avoid an Umbra
102
Separation distance
s
Radius of the lightning
ball according to the
protection class
Shading angle 15°
Lightning rod
Protection angle
www.dehn.de
In South Africa: shading angle = sun elevation on June 21st = 32°
The rule of thumb to use the shading angle for determining the area exploitation factor will
cause higher losses in South Africa because of the high amount of direct sunlight, even in
winter
Area Exploitation Factor and Lightning Protection
103
Area exploitation factor f in %
Mod
ule
tilt β
Area exploitation factor f in %
Mod
ule
tilt β
Losses due to mutual shading and orientation in dependence of inclination
angle β and area exploitation factor f for Munich (Southern Germany)
Shading
Area Exploitation Factor vs. Shading Losses
104
Area exploitation factor f in %
Mod
ule
tilt β
Losses due to mutual shading and orientation in dependence of inclination
angle β and area exploitation factor f for Central Italy
Shading
Area Exploitation Factor vs. Shading Losses
105
Comparison of the shading
sensitivity of thin-film and
crystalline PV modules
Shading
Shading on Thin Film Modules
106
Shading of 4 modules – 7 bypass
diodes affected
Shading of 2 modules – 2 bypass
diodes are affected
Due to the optimised module arrangement, shading losses of 20 % may be
reduced to only 6%.
Due to the changing shading position throughout the year the effect on yield is
not easy to calculate
In many cases high effort for negligible yield improvement
Shading
Optimisation of Shaded Crystalline Modules
107
When there is no shading a
single maximum exists
If shaded an absolute maximum
and a lower local maximum
exists
The maximum with the highest
power can be either the one at
lower voltage or higher voltage
depending on the shading
situation (number of modules
affected, shading intensity)
The inverter will usually operate
in the first maximum available
For finding the real MPP
another tracking algorithm is
necessary and the inverter
needs a wide input voltage
range Shading
Voltage-power-curve of a PV generator for different shading situations
Yield behaviour operating in the global or local MPP under the
same shading situation
The real MPP in a shaded PV System
Po
we
r [K
W]
Voltage [V]
no shading
with shading
with shading
Po
we
r [K
W]
Time of day
Source: SMA global MPP
local MPP
Max. yield loss
108
Multi-MPPT inverter
Higher costs
Module inverters und power optimizer
Simple planning
Additional functions
Longevity still unclear
Higher costs
Danfoss
SolarEdge Shading
Optimisation using Module Orientated Solutions
109
Today often reduced distance
between rows to reduce the specific
land price (high area exploitation
factor)
Self shading effects are inevitable
Yield losses due to shading effects
depends on the string design
A linear connection reduces shading
losses, cable length might increase
Shading
String Layout for Elevated Systems
110
Similar behaviour of elevated flat roof systems and free standing systems
Each row but the first is shaded when the altitude of the sun is low
Solutions to reduce shading losses
Lower tilted module angle (less irradiation enhancement)
Higher distance between rows (less installed power on the same area)
Intelligent string layout
Shading
Shading Effects on Elevated Systems
111
Most important: recognition of appreciable shading
Detection of objects casting shadows
Correct assessment of losses due to shading
Adaption of system design in order to minimize losses due to shading
Optimised plant layout and module orientation to reduce number of
simultaneous shaded modules
Connection of simultaneous shaded modules to strings or even sub-
generators
Technical measures as global MPPT or module-orientated solutions
Shading
Reduction of Shading Losses
112
Thank you
DGS SolarSchool