Optimisation of Balance of System (BOS) for Solar Projects

Balance of System (BOS) of a Solar Project has undergone a significant price reduction but continuous optimisation is making the trend continuing to go further down.

The presentation discusses on aspects around over-loading, cable optimisation, introduction of 1500 V systems and many other interesting optimisations.

1. Balance of Systems-Solar PV Project
GensolEngineering PvtLtd

2. Balance of Systems (BOS)
•Inverters
•Mounting & Racking Systems
•Electrical Equipment and Installation
•Cabling-AC & DC
•Transformers & Breakers
•Combiner Boxes
•Earthing
•Transmission Line, etc
•Civil Work & Development
•Inverter Rooms, CMCS
•Roads, Boundary, Drainage, Cleaning Systems, etc
•Land
•Miscellaneous
All components of a photovoltaic system other the photovoltaic
panels“
”

3. BOS Trends
-10.00
10.00
30.00
50.00
70.00
90.00
110.00
2010-112011-122012-132013-142014-152015-162016-17
Normalized Value
Normalized CERC PV Cost Curves
Project CostModule CostBOS Cost
0.00%
20.00%
40.00%
60.00%
80.00%
100.00%
2010-112011-122012-132013-142014-152015-162016-17
Module-BOS Cost Breakup
Module BOS
•Module cost curve has
outrun BOS cost curve
•BOS optimization from
2013-14
•Module:BOSat 65:35
•Module CARR~ 9%
•BOS CARR ~8%

4. Cost Breakup
Head Components Trend
Inverters
Mounting StructuresMMS, Fasteners,Installation
CivilWorks & DevelopmentRooms, Roads, Boundary, Drainage, Cleaning, etc
Electrical BOSCabling, Transformers,Breakers, Combiner Boxes, Earthing, etc
Land
MiscellaneousCCTV, Monitoring, etc
Module
65%
Inverters
4%
Mounting
Structures
7%
Civil Works &
Development
7%
Electrical BOS
10% Land
6%
Miscellaneous
1%
Solar Project Cost Breakup

5. BOS Reduction due to Module Efficiency
•Efficiency of average commercial wafer based silicon module has grown from
10% to 17% in last 10 years
•Best efficiency multi-crystalline module: 19.2%
Source: FraunhoferISE, 2016

6. BOS Reduction due to Module Efficiency
Impact of increase in module efficiency
Item Components Saving Trend
Scalable DC Cabling, Structures,SCBs,
Connectors, Land
Semi-ScalableRoads, Periphery, Drains, Lighting
Neutral AC BOS, Evacuation,etc
0.0%
2.0%
4.0%
6.0%
8.0%
10.0%
12.0%
14.0%
16.0%
18.0%
Efficiency DC Works StructureAss. Civil WorkLand
0.0% 0.0% 0.0% 0.0% 0.0%
8.3%
8.0% 7.7%
6.0%
7.7%
16.7%
14.1%
16.7%
11.1%
14.2%
% Cost Savings
Cost Savings-Efficiency Increase
300W 325W 350W
For every 5W increase
in module wattage
•project costs
decrease by 0.27%
•BOS costs reduce
by 0.8%

7. BOS Reduction due to Overloading (DC:AC)
Impact of increase in overloading (DC:AC)
Item Components Saving Trend
Neutral DC Cabling, Structures,SCBs, Connectors,
Land
Semi-ScalableRoads, Periphery, Drains, Lighting
Scalable AC BOS, Evacuation,etc

8. BOS Reduction due to Overloading (DC:AC)
1.00
0.96
0.94
0.92
0.91
0.90
1.000
0.984
0.979
0.972
0.968
0.962
0.84
0.86
0.88
0.90
0.92
0.94
0.96
0.98
1.00
1.02
0 10% 15% 20% 25% 30%
Normalization Factor
Overloading(%)
Effect of Overloading on Plant Costs
Normalized BOS Cost/WpNormalized Cost/Wp
1.000
1.083
1.125
1.167
1.209
1.251
1.00
1.10
1.15
1.20
1.25
1.30
1.000
1.050
1.100
1.150
1.200
1.250
1.300
0 10% 15% 20% 25% 30%
NORMALIZED GAIN
OVERLOADING(5)
Cost Benefit Analysis Of Overloading
Normalized Normaized Enegy Gain
For every 10% increase in
overloading
•project costs decrease
by 1.25%
•BOS costs reduce by
3.5%
Cost Benefit Analysis
•Till Generation gain
surpasses increase in
cost

9. DC Cabling & Combiner Boxes
DC side cabling costs have decreased by about 40% due to efficient
design in the last few years
Smart DC Block Sizing
55:45 65:35
75:25
55:35 65:35 75:25
Cost(%) 100% 115% 124%
Loss(%) 100% 113% 120%
Overall Cost(INR/Wp) 0.23 0.37
•Big Plant sizes allow DC block sizing optimization

10. DC Cabling & Combiner Boxes
String Fusing by Y-connectors-> Solar Cable & SCB Cost reduction by around
30%
String Monitoring removed, relying on inverter zone monitoring
Item Saving
Solar Cable 32%
SCB 26%
Overall 28%
Leap Frogging saves 25% cable cost in the case of tracker
With effective design optimization on the DC side, a reduction
of 1.1% and 3.6% on project cost and BOS can be achieved“
”

11. Inverters & Transformers
Inverters
•Inverter costs have reduced by more than 70% from 2010-11
•Driven by
oScale of Production (Inverter learning rates vary from 18-20%)
1
oTechnological advancements:
üMaterial (SiC, GaN)
üBlock Size
üVoltage Increase (1500V)
oLocalization
•Inverters are predicted to see price reductions of 8-9% per annum upto2020
2
Tranformers
•Have shown reduction in costs in recent years due to:
•Higher transformer capacities due to bigger block size
•Metal Prices
•Multi-winding transformer (5-winding, 7 winding) resulting in BOS optimization
Source: 1. FraunhoferISE, 2015
2 GreentechMedia, 2015.

12. Case Study: Impact of Block Size on BOS
Case: 65MW Plant with 5 nos. Of 10MW
and 1 no. of 15MW Block Feeder
Comparison for use of various Transformer winding options
(5 Nos. of 10MW Feeders & 1 No. of 15MW Feeder)
S.N o Parameter Case 1 Case 3
Inverter Room with 2 Inverters & 3
Wi ndi ng Transform er (1 N o.)
Inverter Room with 4 Inverters & 5
Wi ndi ng Transform er (1 N o.)
1 Desi gn Typ e 2.5MVA Block with 3-winding Xmer5MVA Block with 5-winding Xmer
3 No. of Inverter Transformers26 Nos. (2.5 MVA Capacity) 13 Nos. (5MVA Capacity)
4 No. of Aux. Transformers
26 Nos. (One Aux Trasf for each
Inverter room)
13 Nos. (One Aux Trasf for each
Inverter room)
5 No. of UPS
26 Nos. (One UPS for each Inverter
ro o m )
13 Nos. (One UPS for each Inverter
ro o m , b u t s i z e o f UP S wi ll be al m o st
twi ce co m p ared to C ase 1 )
6 No. of VCBs
58 Nos. VCB (630A) & 3Nos. VCB
(1600A)
32 Nos. VCB (630A) & 3Nos. VCB
(1600A)
7
DC P o wer cab l e (SMB to In verter
Cable)
45000 Mtrs (150 Sqmm) & 70000
Mtrs (185 Sqmm)
60000 Mtrs (150 Sqmm) & 90000
Mtrs (185Sqmm)
8 HT C ab l e
13650 Mtrs (3Cx120 Sqmm), 3560
Mtrs (3Cx240 Sqmm), 600 Mtrs
(3Cx300 sqmm)
3950 Mtrs (3Cx240Sqmm), 4320
Mtrs (3Cx300 sqmm)
9
Aux Power Cable (3Cx1.5 sqmm
Cu.)
22815 Mtrs 31900 Mtrs
10 Communication Cable (RS 485)18590 Mtrs 26050 Mtrs
11 Communication Cable (OFC) 31330 Mtrs 12560 Mtrs
12 HDP E P i p es 49950 Mtrs 38610 Mtrs
13
No. of PEB Inverter Rooms (Pre
En gi n eered Bu i l d i n g)
26 13
14
Size of each Inverter Room
(Approx)
8.5m x 6m 14.5m x 6m
15 Tran s fo rm er fo u n d ati o n26 Nos. 13 Nos.
16 CCTV
32 Nos. of HD PTZ type & 7 Nos. of
HD Fi xed typ e
19 Nos. of HD PTZ type & 7 Nos. of
HD Fi xed typ e
Item Savings
(INR/W)
1. Tranformers+Aux.+
UPS
0.06
2. Switchgear 0.25
3. Cables (Power + Aux.
+ Communication)
0.08
4. Civil Work 0.06
Saving of INR 0.45/W due to
Block Size Increase and use
of 5-winding Transformer
“
”

13. 1500V Inverter
Advantages
•Higher DC and AC voltage i.e. lesser current and lesser cabling
•Lesser current allows the increase in inverter block power, lesser BOS
•50% longer strings, implying lesser strings, and 33% lesser junction boxes
•Lesser monitoring, and economical installation
•IEC certifications are in place
•Higher yield
Disadvantages
•Component availability limited at present, thus driving BOS costs higher
•Higher inverter costs due to 1500V components

14. 1500V v/s 1000V
Comparison of 1500V v/s 1000V
Item Remarks Savings (%) Savings
(INR/Wp)
Saving
Trend
PV Modules0.5 USD cents higher for 1500V
-1.15% -0.34
DC Cables
QuantitySaving ~30%
Unit Cost considered 10% extra
for 1500V 22.22% 0.16
SCB
QuantitySaving ~32%
Unit Cost considered 25% extra
for 1500V 15.70% 0.05
AC Subsystem
InverterTrafo, LT Cable, Aux.
Trafo
11.44% 0.08
Inverter
25% higher cost
-25.00% -0.44
Civil & Labour
Inverter Pad for 1500V, Room
for 1000V. Installation Labour
work reduction by 10% assumed 31.08% 0.22
Overall
-0.83% -0.28

15. 1500V v/s 1000V
Comparison of 1500V v/s 1000V (Alternate Optimization)
•For same DC ohmiclosses, a 7.5MW block can be formed in 1500V when
compared to 5MW block
•Bigger block size would mean optimization can be carried on AC side
1500V
7.5MW
1000V
5 MW

16. Land
•The cost of land for solar projects has risen about 6-10 times as compared to
2010-11
•Not only expensive, but difficulties in acquisition
•As the cost of PV modules decrease, land use optimization by decreasing the
tilt, and increasing the power density (kW/sqm)
East-West Mounting
•For places closer to equator, i.e. latitude <10°, solar modules can be mounted
in east west fashion at low tilt angles (around 3°)
•High land utilization, with GCR>80% can be achieved
•Wider peak
•Lesser structure and foundation cost
•Lesser BOS cost
•Marginal drop in generation

17. East-West Mounting
-11.98%
-14.47%
-11.55%
-12.15%
-11.08%-10.98%-11.12%
-7.68%
-4.22%
-3.90%
-4.31%-4.26%
-3.70%-3.81%
-4.81%
-3.72%
-2.62%
-1.73%
30.1628.5926.8424.9723.7623.0722.3122.3621.3218.5217.3814.6614.2913.1411.879.9 9.368.36
GENERATION REDUCTION%
LATITUDE
East West Mounting v/s South Facing

18. Shift from Fixed to Seasonal –How numbers work
•20 X 315Wp modules in series = 6.3kWp = 1 Table
•1MWp = 160 Tables (approx.)
•A team of 3 persons will take 15 minutes to change tilt of 1 table
(on an average), hence, 32 tables per day.
•Five such teams i.e15 persons per day shall be able to change
tilt of 1MWp installation.
•At a labourrate of Rs. 350/-per day, it takes less than Rs. 6000
to change tilt of 1MWp installation.
•Assuming an increment of 3T / MWpbetween fixed and seasonal
tilt, additional capexcomes out to be Rs. 2.4Lacs approx.

19. Structure Trend -Seasonal Tilt -Y 2014 –60T
S.No Description Section Size
Length
(m)
Tot.
Quantity
Unit Weight
(kg/m)
Tot. Wt. (kg)
1) Column Post 130CU60x5 2.80 656 9.42 17302.66
2) Rafter 120CS50x18x3 3.375 656 5.74 12708.36
3) Purlin
130CS50x14x1.
5
4.97 1312 2.96 19301.09
4) Side Bracing-1 L-55x55x5 1.28 984 4.12 5189.222
5) Side Bracing-2 L-55x55x5 1.49 656 4.12 4027.053
6)Connection plate 0.265 656 1.04 682.24
6) Connection Cleat 0.167 2624 0.157 411.968
7) SQ. Washer 0.05 3936 0.0589 231.8304
Total Structural Steel Qty. (kg) 59854.42
Say 60 Ton

20. Structure Trend -Seasonal Tilt -Y 2015 –40T
odule ounting Structural Steel Qty.
Description
Sectional
Details
Quantity
/Table
Grade of
Steel
Finish
Length
(m)
Unit. Wt
(Kg/m)
Component
wt. (kg)
Quantity/
MW
Total Wt
(Kg)
Column 120CU50x3.15
5
350 MpaGAL
2.390 5.10
12.189 835 1017.82
Washer PlatePLT 50x50x5
10
250 MpaGAL
0.050 1.96
0.098 1670 163.87
Rafter 100CU50x2
5
350 MpaGAL
2.910 3.00
8.730 835 7289.55
Purlin (A) 70CS40x15x1.2
4
350 MpaGAL
3.460 1.61
5.576 668 3724.63
Purlin (B) 70CS40x15x1.2
4
350 MpaGAL
5.195 1.61
8.372 668 5592.32
Purlin (C) 70CS40x15x1.2
4
350 MpaGAL
3.460 1.61
5.576 668 3724.63
Side Bracing-140CU40x2
5
350 MpaGAL
1.270 1.75
2.223 835 1855.79
Side Bracing-240CU40x2
5
350 MpaGAL
1.470 1.75
2.573 835 2148.04
Connection
Plate-1 330x100x4
5
250 MpaGAL
0.3303.140
1.036 835 865.23
Connection
Plate-2 265x100x4
5
250 MpaGAL
0.2653.140
0.832 835 694.80
Connection angle L PLT 70x70x3
20
250 MpaGAL
0.110 3.23
0.355 3340 1185.23
Tie Rod 12mm dia
8
250 MpaGAL
0.9650.889
0.858 1336 1145.99
Total Weight Per MW
38567.89
Spare 3 %
1157.04
Say
40 Ton

21. Pre Fab rooms and Decking Sheets
•Pre fab rooms offer significant time advantages in execution timelines
hence bring generation gains and more efficient supplies
•Instances where Pre fab buildings are not considered, decking sheets with
concrete layer on top can offer same benefits. It provides both required
strength, insulationand quicker installation benefits

22. Wind Shielding of Outer most structures
•Recent designs leverage on the density of array yard and consider lower
values of k2 factor in design calculations of structures.
•Outer rows are designed with higher sections as they have more impact of
wind speeds, however inner rows are designed 10-15% lighter to leverage
the shielding that outer structure provides

23. The 0.8mm Galvalume! In Sub 30 T structures!
One name that has echoed in procurement teams lately.
It’s a fine play and tight walk on the line between Optimization and Under design
Galvalume suits fixed tilt structures and can be very good for optimization
Use of galvalume in seasonal tilt structures has seen many failures recently and
resulted in loss of PV modules & of course generation
Extra caution to be exercised while tilting galvalume based structures and must
be done only using proper jacks. Manual tilting is a strict no, if not particularly
addressed during Engineering

24. Cost Saving by Internal Transmission Line
Site specific: If land is not highly constrained, and HT cables are running along
northern boundary
Pros:
•Cheaper compared to HT cable (30-40% lesser at full load evacuation)
•Maintenance friendly, and lesser probability of fault
•Higher current carrying capacity. New age AAAC panther conductors can carry
25MW on single circuit, whereas typical 33kV cables will take around15MW
Cons:
•Land wastage around poles due to shadow
•Land wastage can be minimized by planning TL along boundary, and suitably
oriented to north direction

25. Future Trends
Main Drives of BOS Cost Reduction in future
•Best practices assimilation across the industry
•odule efficiency
•Technological developments
•Incremental design improvements, such as higher overloading, mounting
structure, block size, etc
•Localization including streamlined logistics
•Increase in market volume
•Automation in production, development and installation
Based on the above factors and historical trends, we foresee a BOS cost
reduction of 30%-35% by 2020

26. About Gensol
Gensol, found in 2007 is India’s leading Advisory and System Integrator for Solar
PV Power Projects. Gensol is a channel partner to MNRE and enjoys
empanelment with most major Lending Institutions in India.
2,500+ MW 12,000+ kW
Gensol has an advisory portfolio of
more than 2.5 GW with every 5
th
MW
in India developed with our expertise.
Being an MNRE Channel partner,
Gensol has executed more than 12
MW of Solar Rooftop Projects across
India.
Gensol is based out of Ahmedabad in
Gujarat but has operational solar
projects across 16 Indian States.
With a 130+ Employee Strength –
Gensol prides itself on having the
best technical talent in industry.
AWARDS
BusinessWorld–India’s largest
weekly business magazine awarded
Gensol with “Hottest Young
Entrepreneur” in 2009.
Economic Times –India’s largest
financial daily awarded Gensol in its
“Power of Ideas” series in 2010.
Gensol was the only non-UK based
firm to be nominated for Global
Consultancy of the Year at
BusinessGreenLeader Awards,
London in 2014.

27. Gensol Engineering Pvt Ltd | Gensol Consultants Pvt Ltd
Corporate Office
108, Pinnacle Business Park
OppRoyal Arcade, Prahladnagar
Ahmedabad,Gujarat
India -380015
Email: [email protected]
Website:www.gensol.in
Phone: [phone]
Fax: [phone]
Twitter:gensol_tweets
Gensol is one of the leading consultants and system integrators for Solar Power Plants. We boast of a portfolio of over
2500 MW of Solar Photovoltaic Plants. Gensol is also a channel partner to Ministry of New & Renewable Energy and
installs kW scale Solar Rooftop systems on a turnkey basis with more than 15 MW of cumulative installations across the
country.
The information contained herein is of a general nature and is not intended to address the circumstances of any particular
individual or entity. Although we endeavor to provide accurate and timely information, there can be no guarantee that such
information is accurate as of the date it is received or that it will continue to be accurate in the future. No one should act on
such information without appropriate professional advice after a thorough examination of the particular situation.