1. PV SITE DESIGN FOR MAXIMUM
ENERGY PRODUCTION –
CASE STUDIES
Lior Handelsman - VP Product Strategy &
Business Development, Founder
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2. Part 1: Introduction
1. Introduction
2. Product selection
3. Design considerations
4. Energy loss elimination
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3. What is the Best Design ?
 What module to choose?
 What type of inverter to choose?
 How to best connect modules to inverters?
 What are the best string lengths?
 What size wiring to use?
 How much wiring?
 How to avoid energy losses?
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4. Part 2: Product selection
1. Introduction
2. Product selection
3. Design considerations
4. Energy loss elimination
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5. Component Selection – Selecting PV module
 Technology
 Cost
 Power mismatch
 Availability
 Bankability
 Product and Power warranty
 Degradation over time
©2010 SolarEdge
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6. Component Selection – Selecting PV module
Technical Data
Basic parameters (@25deg)
 Pmpp: 190 Wdc
 Pptc: 168.8 Wdc
 Voc: 32.8 Vdc
 Vmp: 26.7 Vdc
 Isc: 8.05 Vdc
 Imp: 7.12 Vdc
Temperature coefficients
 Pmp_t: ‐0.49 % / ⁰C
 Voc_t: ‐0.34 % / ⁰C
 Vmp_t: ‐0.47 % / ⁰C
 Isc_t: 0.06 % / ⁰C
 Imp_t: 0.02 % / ⁰C
American Technical Publishers, 2007 ©2010 SolarEdge
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7. Component Selection – Selecting Inverter
Central inverter or String inverter?
Advantages of String Inverters:
 Higher yields in fields with high mismatch
 Negligible loss during failure in large fields
 Simple maintenance and replacement
 Outdoor installation - protection class IP65
Advantages of Centralized Inverters:
 Higher inverter efficiency
 Less wire losses through high voltage DC cabling
 Simpler AC cabling
 Lower cost per Wp
©2010 SolarEdge
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8. Case 1: Utility Scale Solar Plant
Waldpolenz, Germany (40MW)
©2010 SolarEdge
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9. Large Scale Planning - Considerations
 String Inverter vs. Centralized Inverter
 Tradeoff between space and cost
 If space is not a constraint, use lower-cost/ lower capacity
thin-film modules to reduce costs
 Cable loss and BoS reduction
 For Centralized inverters, use combiner boxes to combine
multiple DC string cables to thicker ones. Combiner boxes
reduce wiring costs and power losses, simplify installation and
contribute to improved safety of the PV array. However –
combiner boxes increase total system cost
©2010 SolarEdge
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10. Large Scale Planning - Centralized Inverter (1/2)
• 10.87MW field (~145,000 modules)
• Graphical layout represents a 1.9MW section: 26,880 x First Solar 75w modules,
connected to a 1.9 MW inverter
20kV Transformer per
Inverter
Each DC cabinet:
14-16 clusters
Each 1.9MW Inverter: Each cluster:
16 DC cabinets (=224 clusters x 120 modules) 12 strings x 10 modules
©2010 SolarEdge
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11. Large Scale Planning - Centralized Inverter (2/2)
©2010 SolarEdge
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12. Large Scale Planning - String Inverter
Each string
connected to
7.8kW inverter
Each string: 1 Transformer per
104 modules 1MW field
©2010 SolarEdge
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13. Case 2: Commercial Site with Limited Space
 A 100kW roof has been simulated using PVsyst
 Panel rows have been placed distanced apart to minimize inter-row shading
 The roof space is 2,000 sqm
 Kyocera KD210GH-2P modules x 210w x 480 = 100.8 kW
 48 modules per row, 10 rows, 9 m between rows
©2010 SolarEdge
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14. System Design
100kW system
Inverters 1 X 100kW
Modules per string 24
Strings per inverter 20
©2010 SolarEdge
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15. PVsyst Energy Calculation – 100kW system
©2010 SolarEdge
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16. Case 2: Commercial Site with Limited Space
Alternative Design
 On the same roof we reduce the distance between module rows to double the
power capacity, while increasing inter-row shading
 PVsyst design and energy calculation
 Kyocera KD210GH-2P modules x 210 x 960 = 201kW
 48 modules per row, 20 rows, 4.5 m between rows
©2010 SolarEdge
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17. System Design
100kW system 200kW system
Inverters 1 X 100kW 1 X 200kW
Modules per string 24 20
Strings per inverter 20 48
©2010 SolarEdge
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18. Site Layout +
injection point
A B
 Combiner Boxes: 2
(24 strings per box)
. . .  Wiring:
. . . — String-combiner
. . . box, total: 4640m
(DC)
— Combiner boxes-
inverter: 50m (DC)
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©2010 SolarEdge

19. PVsyst Energy Calculation – 200kW Partially Shaded
©2010 SolarEdge
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20. Comparative Analysis
100kW system 200kW system
Peak power 100.8 kWp 201.6 kWp
Combiner boxes 1 2
Wiring 2,000m (DC) 4,000m (DC)
Shading loss 1.5% 11.4%
Annual AC energy 175 MWh 306 MWh
AC energy / sqm 87.5 kWh/m2 153 kWh/m2
System cost* €300,000 €590,000
IRR 12.4% 10.5%
LCOE (€cent/kWh) 12.62 14.06
* Estimation ©2010 SolarEdge
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21. Part 3: Design considerations
1. Introduction
2. Product selection
3. Design considerations
4. Energy loss elimination
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22. How to Best Combine the Modules and Inverter?
Inverter Sizing
 Consider module orientation – panels will not always be at peak
 Maximize array performance NOT maximize inverter loading
 Don’t over power the inverter !
In Israel - rated DC power should be about +3-7% of rated AC power
Going above this you will have:
 Frequent inverter power limiting
 Reduced energy yields during high irradiance
©2010 SolarEdge
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23. How to Best Combine the Modules and Inverter?
Inverter Sizing – Cont.
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6
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0
1,000
1,050
1,200
1,250
1,300
1,100
1,150
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550
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650
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Irradiance (W/m 2 )
Energy (%) Occurrence (%)
©2010 SolarEdge
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24. How to Best Combine the Modules and Inverter?
String Sizing
 What is the coldest ambient Temperature? (-8)
 Calculate the maximum voltage from the module (Voc_max)
 Voc max = Voc * ( 1+((Tamb_min – Tstc) * Voc_t)
 Voc_max=32.8Vdc+(32.8Vdc *(‐8⁰C‐25⁰C)*‐0.34%/⁰C))=36.48 Vdc
- Design the maximum string length to the coldest temperature
 Inverter Vmax=550VDC
 Maximum string length = 550VDC/36.48VDC=15 modules
©2010 SolarEdge
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25. How to Best Combine the Modules and Inverter?
String Sizing
 What is the hottest ambient Temperature? (45deg)
 Cell temperature can be 25-30deg above this!
 Calculate the minimum MPP voltage of the module (Vmp_min)
 Vmp min = Vmp * ( 1+((p_ p ((Tamb – Tstc +ΔT) * Vmp_t))
 Vmp_min=26.7Vdc+(26.7*((32⁰C‐25⁰C+30⁰C)*‐0.47%/⁰C))=22.06
- Design the minimum string length to the hottest temperature
 Inverter Vmax=250VDC
 Maximum string length = 250VDC/22.06VDC=12 modules
©2010 SolarEdge
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26. Logical Layout of PV Field
XXX panels
YYY panels in string
ZZZ inverters
Total of RRR kW
AC distribution box
Medium voltage transformer
©2010 SolarEdge
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27. Wire Dimensioning Recommendations:
 Rule of thumb - No more than 2% wire losses
 Choose correct wire as a function of current and length
 Max. voltage drop DC - cables (STC) : ∆UDC ≤ 1%
 Too much DC voltage drop will put inverter out of MPPT in
hot days
 Max. voltage drop AC - cables (Pn) : ∆UAC ≤ 1%
 Too Much AC voltage drop and the inverter will have frequent
AC overvoltage disconnections
©2010 SolarEdge
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28. Part 4: Energy loss elimination
1. Introduction
2. Product selection
3. Design considerations
4. Energy loss elimination
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29. Inherent Problems in Traditional Systems
Energy Loss System Drawbacks
 Module mismatch (3-5% loss)  No module level monitoring
 Partial Shading (2-25% loss)  Limited roof utilization
 Undervoltage/Overvoltage (0-15%)  Safety Hazards
 Dynamic MPPT loss (3-10% loss)  Theft
SolarEdge solution overcomes all energy losses
providing up to 25% more energy while solving
the other system drawbacks at a comparable
price to traditional inverters
©2010 SolarEdge
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30. SolarEdge System Overview
 Module level optimization  Module level monitoring
 Fixed voltage - ideal installation  Enhanced safety solution
©2010 SolarEdge
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31. Distributed DC Architecture – Flexible Design
 No string sizing
 Parallel Strings can be of unequal length
The Result:
 Easy to Design
 Long strings  less home-runs  reduced wiring
 Installation never passes 550VDC
 Not temperature dependent
©2010 SolarEdge
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32. Distributed DC Architecture – Fixed String Voltage
Fixed inverter input voltage - at optimal inverter input
 Strings of different lengths
 Modules on multiple roof facets
 Modules with different power ratings
 Modules of different technologies
The Result:
 Maximum roof utilization
 Easily scalable
 10%-20% savings on wiring and BoS components
 15% saving in labor
©2010 SolarEdge
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33. Back to case 2:
System Design – 200kW field, SolarEdge Layout
100kW system 200kW system 200kW
SolarEdge
Inverters 1 X 100kW 1 X 200kW 17 x SE12k
Modules per string 24 20 56 / 57
Strings per inverter 20 48 1
©2010 SolarEdge
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34. SolarEdge Site Layout panel board +
injection point
 Wiring:
— String-inverter,
total: 485m (DC)
— Inverters-
. . .
. . transformer: 835m
.
. . . (AC)
©2010 SolarEdge
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35. PVsyst Energy Calculation – 200kW SolarEdge layout
©2010 SolarEdge
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36. Comparative Analysis
100kW system 200kW system 200kW SolarEdge
Peak power 100.8 kWp 201.6 kWp 201.6 kWp
Combiner boxes 1 2 0
Wiring 2,000m (DC) 4,000m (DC) 330m(DC)+679m(AC)
Shading loss 1.5% 11.4% 5.2%
Annual AC energy 175 MWh 306 MWh 341 MWh
(+11.4% gain over
200kW traditional system)
AC energy / sqm 87.5 kWh/m2 153 kWh/m2 170.5 kWh/m2
System cost €300,000 €590,000 €615,000
IRR 12.4% 10.5% 12.6%
LCOE (€cent/kWh) 12.62 14.06 11.93
©2010 SolarEdge
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37. Comparative Analysis – System Cost Breakdown
 Cost of 200kW and 200kW SolarEdge system components, relative to 100kW system
components (100%)*
0% 50% 100% 150% 200% 250%
Inverter cost
Electrical BoS cost
Cables, fuses, combiner boxes
100kW system
Monitoring Included 200kW system
12-year warranty 200kW SolarEdge
Included
Other system costs
Modules, racking
Total system cost
* Estimation ©2010 SolarEdge
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38. Comparative Analysis
100kW system 200kW system 200kW SolarEdge
Peak power 100.8 kWp 201.6 kWp 201.6 kWp
Combiner boxes 1 2 0
Wiring 2,000m (DC) 4,000m (DC) 330m(DC)+679m(AC)
Shading loss 1.5% 11.4% 5.2%
Annual AC energy 175 MWh 306 MWh 341 MWh
(+11.4% gain over
200kW traditional system)
AC energy / sqm 87.5 kWh/m2 153 kWh/m2 170.5 kWh/m2
System cost* €300,000 €590,000 €615,000
IRR 12.4% 10.5% 12.6%
LCOE (€cent/kWh) 12.62 14.06 11.93
* Estimation ©2010 SolarEdge
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39. Case 3: Distributed DC Architecture – Enabler
 Installation on 4 roof facets enables 15kW capacity
 Different types of panels connected in a string enable full roof
utilization
Design and
installation by
Solgal Energy
©2010 SolarEdge
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40. 3 Types of Modules, 3 Long Strings, 4 Orientations
 25 Suntech 280W modules
 34 Suntech 210W modules
 4 Suntech 185W modules
 PowerBox per module
 3 single phase SE5000 SolarEdge inverters
 2 strings of 20 modules and 1 string of 23 modules
©2010 SolarEdge
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41. Full Roof Utilization Proves to be Cost Efficient
 The larger the system, the lower the cost per kWp
 Efficiency decreases in non-south-facing facets
South East West North System total System average
KWp 4.3 3.8 2.9 3.9 14.9
KWh/KWp /day KWh/day KWh/KWp/day
January 2.82 2.26 1.50 0.98 28.9 1.9
February 3.38 2.88 2.11 1.54 37.6 2.5
March 4.15 3.76 3.06 2.49 50.7 3.4
April 4.77 4.59 4.07 3.64 64.0 4.3
May 5.33 5.40 5.10 4.79 76.9 5.2
June 5.70 5.92 5.76 5.54 85.3 5.7
July 5.67 5.82 5.58 5.31 83.4 5.6
August 5.63 5.53 5.01 4.55 77.5 5.2
September 5.33 4.90 4.05 3.40 66.5 4.5
October 4.52 3.87 2.89 2.15 50.9 3.4
November 3.53 2.86 1.90 1.24 36.4 2.4
December 2.76 2.17 1.38 0.86 27.5 1.8
Year average 4.47 4.16 3.53 3.04 57.1 3.8
Year total 1630 1520 1290 1110 20853 1400
As % of maximum potential 99% 92% 78% 67% 85%
(1650 KWh/KWp/year)
 With total system efficiency of 85% of complete-south system, the ratio
between system cost and system throughput remains attractive
 Average production – >5kWh / kWp per day 41
©2010 SolarEdge

42. Module Level Monitoring – Physical System Layout
String 3, panels 1-20:
Facet West West East East
Model 210w 280w 280w 210w
©2010 SolarEdge
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43. Module Level Monitoring – Power Curves
280w West 280w East
210w West 210w East
280w East
280w West
210w East
210w West
©2010 SolarEdge
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44. Module Level Monitoring – Accurate Fault Detection
2.1.5
 Module 2.1.5 (red
curve) is partially
shaded by the bottom
right corner of the
opposite module, as
shown in the power
curves
©2010 SolarEdge
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45. Module Level Monitoring – Accurate Fault Detection
* Before module
re-mounting
2.1.5
 Underperformance of
module 2.1.5 was
automatically alerted
by the system, and the
module was
remounted to avoid
the shading as shown
in the power curves
©2010 SolarEdge
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46. Thank you
Websites:
Email: info@solaredge.com www.solaredge.com
Twitter: www.twitter.com/SolarEdgePV www.solaredge.de
Blog: www.solaredge.com/blog www.solaredge.jp
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