1. Photovoltaic modules Session 6
DAMON FYSON

2. Photovoltaic modules Session 6
PV cells can be arranged in a series configuration to form a module (panel)
Modules (panels) can then be connected in parallel-series configurations to form series string and parallel arrays.
 When connecting cells or modules in series, they must have the same voltage rating to produce an additive voltage output, and similarly, modules must have the same current rating when connected in parallel to produce larger currents.
DAMON FYSON

3. A number of PV panels in series is termed a string
Photovoltaic modules
Session 6
A number of PV panels in series is termed a string
A number of strings in parallel is termed an array
DAMON FYSON

4. Photovoltaic modules Session 6 DAMON FYSON
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DAMON FYSON

5. Photovoltaic modules Session 6 DAMON FYSON
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DAMON FYSON

6. Photovoltaic modules Session 6 DAMON FYSON
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DAMON FYSON

7. Photovoltaic modules
Session 6
DAMON FYSON

8. Photovoltaic modules
Session 6
DAMON FYSON

9. Photovoltaic modules
Session 6
Mismatch losses are caused by the interconnection of solar cells or modules which do not have identical properties
Output determined by the solar cell with the lowest output.
example, when one solar cell is shaded remainder in the module are not, the power being generated by the "good" solar cells can be dissipated by the lower performance cell rather than powering the load.
The comparison of an ideal and a non-ideal solar cell. For mismatch, the greatest difference is when the cell is driven into reverse voltage bias
Source
DAMON FYSON

10. Theory of I-V Characterization
Photovoltaic modules
Session 6
Theory of I-V Characterization
PV cells can be modeled as a current source in parallel with a diode.  When there is no light present to generate any current, the PV cell behaves like a diode.  As the intensity of incident light increases, current is generated by the PV cell, as illustrated in Figure 1
DAMON FYSON

11. Photovoltaic modules Session 6 I-V Curves for Modules
For a module or array of PV cells, the shape of the I-V curve does not change. However, it is scaled based on the number of cells connected in series and in parallel.  When n is the number of cells connected in series and m is the number of cells connected in parallel and ISC and VOC are values for individual cells, the I-V curve shown in Figure 10 is produced.
DAMON FYSON

12. Photovoltaic modules Session 6 DAMON FYSON
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DAMON FYSON

13. Panels in series (string) Vt = V1+V2….
Photovoltaic modules
Session 6
strings in parallel
It = I1 +I2……
Panels in series (string)
Vt = V1+V2….
DAMON FYSON

14. Understanding cell connection
Photovoltaic modules
Session 6
Understanding cell connection
Current (A)
The PV module is the basic unit in a complete PV system
Understanding how the module is designed and assembled provides key understanding to designing a system
Towards this end consider the following IV characteristics of a single cell 4
Voltage (V) 0.6
DAMON FYSON

15. Photovoltaic modules Session 6 Current (A)
With three cells connected in series the combined characteristics are shown
Connecting the cells in series maintains the same current, only the voltage of each cell is added together 4
Voltage (V)
The combined IV characteristics of three identical cells connected in series
DAMON FYSON

16. Current (A) Current (A)
Photovoltaic modules
Session 6
Current (A) Current (A) C
If two cells with different characteristics (dissilimar) are wired together in series, the result is shown in following figures
Series connected dissimilar cells produce an added voltage output, but series current is equal to the lowest value of the two
Voltage (V) A B Voltage (V) A B
The individual IV characteristics of two dissimilar cells
Current (A) C D
Voltage (V) A+B
The combined IV characteristics of the two dissimilar cells connected in series
DAMON FYSON

17. Fill Factor Photovoltaic modules Session 6 (slide ½) DAMON FYSON
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DAMON FYSON

18. Photovoltaic modules Session 6 DAMON FYSON
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DAMON FYSON

19. Commercial Modules Photovoltaic modules Session 6
Solar module manufacture was 39MWs in 1994 increased to 1900MWs in 1994
PV module production capacity increased by nearly 70% over the course of 2010, reaching nearly 30 GW by the end of the year according to IMS Research
source : superhydrophobic-pv-array
Some Common standards applied to PV modules
IEC Crystalline Silicon Terrestrial photovoltaic (PV ) modules
IEC Crystalline Thin-film Terrestrial photovoltaic modules
DAMON FYSON

20. Five common solar panel defects
Photovoltaic modules
Session 6
Five common solar panel defects
The following defects are common when testing solar panels:
Scratches on frame / glass
Excessive or uneven glue marks / Glue marks on glass
Gap between frame and glass due to poor sealing
Lower output than stated in data sheet (we require positive tolerance on each solar panel)
Lower FF than stated in requirements
DAMON FYSON

21. Standard PV Panel testing parameters:
Photovoltaic modules
Session 6
Standard PV Panel testing parameters:
With the use of the flash test, the following parameters are tested.
1. VOC (V), open-circuit voltage, The voltage output of the module is measured with the module disconnected from any load.
2. VMP (V), voltage at maximum power point, the voltage at which the module puts out the most power
3. ISC (A), the short-circuit current, Circuit Current (Isc)” and is the amount of current that the pv module supplies into a dead short.
4. Imp (A), Current at maximum power point (Imp)” and is the number of Amperes delivered by the module at its maximum power point.
5. Pm (W), Maximum Power and Maximum Power Point, power is equal to Amperes times Volts (P=IE, or Watts=Amperes X Volts). Every module has a specific point on its power curve where the product of Amps times Volts yields the greatest Wattage. This is the Maximum Power Point, the flash test takes data over the entire range of voltage and current. This way the wattage for each Current and Voltage data point can be calculated. By doing this we can find the Maximum Power Point in the sea of Current versus Voltage data.
6. FF (%), Fill Factor, the Fill Factor is defined as the maximum power produced (at MPP) divided by the product of Isc and Voc. One can see that the Fill Factor will always be less than 1.
DAMON FYSON

22. Photovoltaic modules
Session 6
DAMON FYSON

23. 2011 Global Top Ten Solar Cell Manufacturer
Photovoltaic modules
Session 6
2011 Global Top Ten Solar Cell Manufacturer
Company
Capacity (MW)
Country
Suntech
2,400
China
JA Solar
2,100
Trina
1,900
Yingli
1,700
Motech Solar
1,500
Taiwan
Gintech
Canadian Solar
1,300
Neo Solar Power
Hanwha Solar One
1,100
JinkoSolar
Source
EnergyTrend
[3]
DAMON FYSON

24. 2011 Global Top Ten Solar Module
Photovoltaic modules
Session 6
2011 Global Top Ten Solar Module
Company
Capacity (MW)
Country
Suntech
2,400
China
LDK
2,500
Canadian Solar
2,000
Trina
1,900
Yingli
1,700
Hanwha Solarone
1,500
SolarWorld
1,400
Germany
Jinko
1,100
Sunneeg
1,000
Sunpower
USA
Source
EnergyTrend
[4]
DAMON FYSON

25. Photovoltaic modules Session 6 DAMON FYSON
                                                                                                                                
Although yearly ranking is as listed above, quarterly ranking can indicate that which company can sustain particular conditions such as sever price adjustment, Government Feed-
Photovoltaic modules
Session 6
DAMON FYSON

26. Example of specification on a typical module 188 Watt
Photovoltaic modules
Session 6
Example of specification on a typical module
188 Watt
monocrystalline panel
Source:
DAMON FYSON

27. Continue Example of specification on a typical module
Photovoltaic modules
Session 6
Continue Example of specification on a typical module
188 Watt
monocrystalline panel
Source:
DAMON FYSON

28. String inverter with one string
Photovoltaic modules
Session 6
String inverter with one string
String inverter
grid
The PV array is connected as one string and then connected to one inverter
DAMON FYSON

29. Several strings connected in parallel
Photovoltaic modules
Session 6
Central inverter
grid
Several strings connected in parallel
DAMON FYSON

30. The output of a single module Vmp = 17V Imp= 4A
Photovoltaic modules
Session 6
The output of a single module Vmp = 17V Imp= 4A
What will be the array output
DAMON FYSON

31. The output of a single module Vmp = 17V Imp= 4A
Photovoltaic modules
Session 6
The output of a single module Vmp = 17V Imp= 4A
What will be the array output
DAMON FYSON

32. Photovoltaic modules Session 6 DAMON FYSON
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DAMON FYSON

33. Electrical Protection
Photovoltaic modules
Session 6
Electrical Protection
The PV module far right will not pass current
Because the cells in the module are connected in series and a cell is damaged(or some cells shaded) the current from the whole modules is reduced, and hence the string or array
If one cell is damaged the rest of the array can force current through it
This phenomenon is known as a Hot –spot, the cell may cause the whole array to go open circuit
The following slides shown how a diode may minimize the problem
DAMON FYSON

34. + _ Photovoltaic modules Session 6 BYPASS DIODES
The module will produce less power
One or more of the cells is defective
One of more of the cells is shaded
An operating module will cause a reverse voltage to appear across the defective or shaded cell
The diode provides an alternative path for a current when a reverse voltage is present + _
DAMON FYSON

35. Hot-Spot Heating and Bypass Diodes
Photovoltaic modules
Session 6
Hot-Spot Heating and Bypass Diodes
Dissipation of power in poor cells leads to breakdown in localized regions of the cell p-n junction. An enormous power dissipation can occur in a small area, leading to local overheating, or "hot spots", which in turn leads to destructive effects, such as cell or glass cracking or melting of solder
Renewable/supporting%20meterial/PVDevices/pvcdrom/Ch06/Hotspot.Htm
DAMON FYSON

36. Photovoltaic modules Session 6 DAMON FYSON
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DAMON FYSON

37. Photovoltaic modules
Session 6
DAMON FYSON

38. Photovoltaic modules Session 6 DAMON FYSON
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DAMON FYSON

39. Photovoltaic modules Session 6 DAMON FYSON
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DAMON FYSON

40. Photovoltaic modules
Session 6
DAMON FYSON

41. Photovoltaic modules Session 6 DAMON FYSON
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DAMON FYSON

42. Example of Non-Uniform Soiling
Photovoltaic modules
Session 6
Example of Non-Uniform Soiling
DAMON FYSON

43. Photovoltaic modules Session 6 DAMON FYSON
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DAMON FYSON

44. The next 3 slides show what may happen with blocking diodes
Photovoltaic modules
Session 6
The next 3 slides show what may happen with blocking diodes
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DAMON FYSON

45. Photovoltaic modules Session 6 DAMON FYSON
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DAMON FYSON

46. Bypass diodes fit a potential catastrophic event.
Photovoltaic modules
Session 6
Bypass diodes fit a potential catastrophic event.
source:
DAMON FYSON

47. Photovoltaic modules Session 6
Bypass diodes allow current to pass around shaded cells and thereby reduce the voltage losses through the module. When a module becomes shaded its bypass diode becomes “forward biased” and begins to conduct current through itself. All the current greater than the shaded cell’s new short circuit current is “bypassed” through the diode, thus reducing drastically the amount of local heating at the shaded area.
Source:
DAMON FYSON

48. Photovoltaic modules Session 6
bypass diodes are integrated into the solar cell structure during cell fabrication. The main conclusion is that the present integral bypass diode approach automatically protects against thermal instability in both small and large arrays without the need for any other protective measures.
Source:
DAMON FYSON

49. Source: Paul Hernday so
Photovoltaic modules
Session 6
Source: Paul Hernday so
DAMON FYSON

50. Photovoltaic modules
Session 6
DAMON FYSON

51. Bypass diodes do cause other problems
Photovoltaic modules
Session 6
Bypass diodes do cause other problems
source:
DAMON FYSON

52. Photovoltaic modules Session 6 DAMON FYSON
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DAMON FYSON

53. Photovoltaic modules Session 6
One potential problem arises from an open-circuit in one of the series strings. The current from the parallel connected string (often called a "block") will then have a lower current than the remaining blocks in the module. This is electrically identical to the case of one shaded solar cell in series with several good cells, and the power from the entire block of solar cells is lost. The figure below shows this effect.
Potential mismatch effects in larger PV arrays. Although all modules may be identical and the array does not experience any shading, mismatch and hot spot effects may still occur
sorce:
DAMON FYSON

54. Photovoltaic modules Session 6
The current may now flow through the by-pass diodes associated with each module, but must also pass through the one string of by-pass diodes. These by-pass diodes then become even hotter, further reducing their resistance and increasing the current flow. If the diodes are not rated to handle the current from the parallel combination of modules, they will burn out and allows damage to the PV modules to occur.
Bypass diodes in paralleled modules. There are typically two bypass diodes in each 36 cell module.
Source:
DAMON FYSON

55. Photovoltaic modules Session 6
In addition to the use of by-pass diodes to prevent mismatch losses, an additional diode, called a blocking diode, may be used to minimize mismatch losses.
With parallel connected modules, each string to be connected in parallel should have its own blocking diode. This not only reduces the required current carrying capability of the blocking diode, but also prevents current flowing from one parallel string into a lower-current string and therefore helps to minimise mismatch losses arising in parallel connected arrays.
Impact of blocking diodes in parallel connected modules
DAMON FYSON

56. Junction box with integrated bypass diodes
Photovoltaic modules
Session 6
If an inactive cell (e.g. due to shading) is fed current by the other, active cells, it converts this energy into heat. The worst case scenario is that a hot spot builds up in the inactive cell that can destroy the module. To avoid this, bypass diodes are used that duct the current past the cell string containing the inactive cell.
Junction box with integrated bypass diodes
Source:
DAMON FYSON

57. Source: pv_verband 2009 Photovoltaic modules Session 6
Minimising power loss
Without a bypass diode, a single shaded cell would reduce power production of the entire series connection to a minimum. Thanks to the bypass diode, the total power yield only decreases by the lost yield of the bypassed cell string. Shading with and without bypass diode
Source:
DAMON FYSON

58. Source: pv_verband 2009 Photovoltaic modules Session 6
DAMON FYSON

59. Source: pv_verband 2009 Photovoltaic modules Session 6
AS/NZS 5033:2005
1.4.4 Bypass diode
A diode that is connected in parallel with a PV module, or a group of PV cells within a PV module, and prevents the PV module or group of cells from being reverse biased
(see Figures 1.1 and 1.2).
DAMON FYSON

60. (b) Have a current rating of at least 1.25 × ISC MOD.
Source: pv_verband 2009
Photovoltaic modules
Session 6
AS/NZS 5033:2005
2.2 BYPASS DIODES
Bypass diodes may be used to prevent PV modules from being reverse biased and consequent hot spots occurring. If bypass diodes are added by the installer, they shall comply with all the following requirements:
(a) Have a voltage rating of at least 2 × VOC MOD of the protected module.
(b) Have a current rating of at least 1.25 × ISC MOD.
(c) Be installed so no live parts are exposed.
(d) Be protected from degradation due to environmental factors.
DAMON FYSON

61. (a) Have a voltage rating of at least 2 × VOC ARRAY.
Source: pv_verband 2009
Photovoltaic modules
Session 6
AS/NZS 5033:2005
2.3 BLOCKING DIODES
Blocking diodes may be used but they are not a substitute for fault current protection. One of their purposes is to prevent reverse currents from battery systems leaking into a PV array at night, when this protection is not an integral part of the battery charge controller.
If used, blocking diodes shall comply with all the following requirements:
(a) Have a voltage rating of at least 2 × VOC ARRAY.
(b) Have a current rating of at least 1.3 times the short circuit current at STC of the
circuit that they are intended to protect. That is—
(i) 1.25 × ISC MOD for PV strings;
(ii) 1.25 × ISC S-ARRAY for PV sub-arrays; or
(iii) 1.25 × ISC ARRAY for PV arrays.
(c) Be installed so no live parts are exposed.
(d) Be protected from degradation due to environmental factors.
DAMON FYSON

62. The shape of modules are restricted to rectanglar
Photovoltaic modules
Session 6
The shape of modules are restricted to rectanglar
DAMON FYSON

63. PV Panel Warranties and guarantees
Photovoltaic modules
Session 6
PV Panel Warranties and guarantees
Australian Standards
Accredited installer to provide proof that panels meet Australian standards.
The Clean Energy Council has a frequently updated list of all solar panel and inverter models that meet Australian standards..
Solar PV systems must also comply with The CEC Design and Installation Guidelines.
Warranties and guarantees
Solar PV panels generally come with a performance warranty that can last up to 25 years and a guarantee lasting five to ten years. Additionally, panel material warranties and workmanship guarantees generally span 5-10 years.
DAMON FYSON

64. Warranties and guarantees cont……………..
Photovoltaic modules
Session 6
Warranties and guarantees cont……………..
It is important to know who is providing the warranty – the manufacturer or the importer. In the absence of a manufacturer, the importer is responsible for the warranty. However, if the importer changes their business name or sells their business, their warranty obligations towards the customer cease.
Installer must state who is providing the warranty.
A system manual that provides operation, maintenance and safety information should be provided by your installer. This must also include a system energy output (kWh) estimate. It is important for you to provide written confirmation of statements including performance claims, guarantees and warranties.
DAMON FYSON

65. Great web site for pv understanding
Source: pv_verband 2009
Photovoltaic modules
Session 6
Great source
Great web site for pv understanding
DAMON FYSON