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

20

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

21

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

25

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

26

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


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


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

29

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

31

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

33

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

34

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


Solar irradiation

• Solar energy


• Measurement

Solar cells



Solar modules

• Production



• By-pass diodes

Shading

• Basics

• Site survey



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

40

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

50

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


• Motivation


Solar irradiation

• Solar energy


• Measurement

Solar cells



Solar modules

• Production



• By-pass diodes

Shading

• Basics

• Site survey



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


• Motivation


Solar irradiation

• Solar energy


• Measurement

Solar cells



Solar modules

• Production



• By-pass diodes

Shading

• Basics

• Site survey



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


• Motivation


Solar irradiation

• Solar energy


• Measurement

Solar cells



Solar modules

• Production



• By-pass diodes

Shading

• Basics

• Site survey



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


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


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

PV-Basics - DUT

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