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Page 1: Solar PV Technologies

Solar PV Technologies: A Few Key Issues

CONFIDENTIALADITYA BIRLA GROUP

Amitabh Verma, Ph.D

Vice President- Technology

Solar Power Business

Page 2: Solar PV Technologies

Outline

• Technology as profitability driver

• Importance of meteorological data

• Selection of modules for power plants

• Pros and cons of thin film modules

• Inverter choices for power plants

• Module layout options

• Concentration photovoltaic

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• Concentration photovoltaic

• Operation and Maintenance

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Page 3: Solar PV Technologies

Profitability Through Design

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Page 4: Solar PV Technologies

Comparison of Satellite and Ground Based Data

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MOS is Model Output Statistics which takes into account

ground based data and satellite data

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Page 5: Solar PV Technologies

How Predictable is Year-To-Year Radiation Data?

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Brightening Dimming Brightening

Very few weather stations in the world have 40-50 years radiation data

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Page 6: Solar PV Technologies

Measurement Uncertainty

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Page 7: Solar PV Technologies

3

4

5

6

7

8G

HI

(kW

h/m

2/d

ay

)

MNRE NASA Meteonorm

Global Horizontal Incidence (GHI) for Jodhpur

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0

1

2

Jan Feb Mar Apl May Jun Jul Aug Sep Oct Nov Dec

Months

� NASA data is based on Satellite Imaging

� Meteonorm is based on Satellite Imaging and weather station� MNRE is based on weather station� NASA was different than MNRE and Meteonorm in ANOVA analysis

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Page 8: Solar PV Technologies

20

25

30

35

40

Am

bie

nt

tem

p.

(oC

)

MNRE 24 h average MNRE day time average NASA 24 h average Meteonorm 24 h average

Ambient Temperature for Jodhpur

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0

5

10

15

20

Jan Feb Mar Apl May Jun Jul Aug Sep Oct Nov Dec

Am

bie

nt

tem

p.

(

Months

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Page 9: Solar PV Technologies

Variation of Plant Output with GHI and Ambient Temp.

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Page 10: Solar PV Technologies

1694

1678

1709

1620

1640

1660

1680

1700

1720E

ne

rgy

Ou

tpu

t (M

Wh

)

Plant Output per MWp Using Different Weather Data

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1593

1520

1540

1560

1580

1600

MNRE-24 h MNRE-Day Temp NASA Meteonorm

En

erg

y O

utp

ut

(MW

h)

Weather Data

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Page 11: Solar PV Technologies

18.5 18.3

17.2

18.7

26.4 26

23.4

26.9

20

25

30

IRR

(%

)

Project IRR (Pre-tax) Equity IRR (Pre-tax)

Project Return

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0

5

10

15

MNRE-24 h MNRE-Day Temp NASA Meteonorm

IRR

(%

)

Weather data

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Page 12: Solar PV Technologies

Uncertainty in Yield Calculation

Parameters % Uncertainties Remarks

Year-to-Year climate variability 4%

Solar resource estimation in the

horizontal plane5%

This is due to variation in irradiance and

temperature data

Radiation in the plane of array 3%

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Power rating of modules 3% Variability due to manufacturing

Losses due to dirt 2%

Other sources of error 5%The losses in inverter, cable and transformers

have uncertainty

Annual Uncertainty 8.4%

Monte Carlo Simulation has to be done to calculate the probabilistic generation value

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Page 13: Solar PV Technologies

Inverters

Grid

Schematic of MW Solar Park

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AC Panel

Inverters

Combiner box with string monitoring ,

DC switch and Surge Protector

AC Switch AC Ckt BreakerStep up

Transformer

Data Monitoring

Power Socket

Sensor

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Page 14: Solar PV Technologies

4.00%

5.00%

6.00%

7.00%

Total Loss Pareto

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Near

Shading

on

Global

IAM

Factor on

Global

Non-STC

Operatio

n

Soiling

DC Array

Variabilit

y

Module

Mismatc

h

DC Cable

Loss

Inverter

Efficiency

Inverter

Limitatio

n

Inverter

Cooling

Data

Acquisiti

on & Aux

MV

Transfor

mers

AC Cable

Loss

HV

Transfor

mer

Series1 1.60% 1.90% 6.10% 3.00% 2.00% 1.50% 1.00% 1.62% 0.09% 0.41% 0.12% 1.06% 1.00% 0.47%

0.00%

1.00%

2.00%

3.00%

Total loss to the tune of 22%

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Page 15: Solar PV Technologies

Effect of Temperature on the Output

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Page 16: Solar PV Technologies

Module Type Temp. Coeff.Module

Efficiency (%)Tolerance

Relative Module

Price

Mono-crystalline Silicon -0.41%/0C 14-20 3% 1.1

Multi-crystalline silicon -0.46%/0C 13-18 3% 1.0

Increasing

Area

Crystalline or Thin Film Module

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Cadmium Telluride Thin

Film-0.30%/0C 10-11 5% 0.90

Micromorph Silicon -0.25%/0 C 6-7 5% 0.75

Amorphous Silicon Thin

Film (Single Junction)-0.18%/0 C 5-6 5% 0.70

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Page 17: Solar PV Technologies

Cd-Te Module

Multi-crystalline Module

I-V Characteristic of Modules

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Mono-crystalline Module Amorphous Silicon Module

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Page 18: Solar PV Technologies

Visual Identification of Different Modules

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Mono-Crystalline Multi-Crystalline Amorphous Si Cadmium Telluride

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Page 19: Solar PV Technologies

Module Type

Module

Wattage

(Wp)

No. of

Modules

No. of

Modules in

series

No. of

Strings

Total Module

Area

Annual

Energy

(kWh)

Excess

Energy

Compared

to Multi-

crystalline Si

PR

SunPower 210 23184 18 1323 29627 8847762 0.88% 77.7

Mono-

Crystalline 210 23805 15 1587 39629 8806077 0.40% 77.4

5 MWp Plant Design with Different Modules

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Crystalline

silicon

210 23805 15 1587 39629 8806077 0.40% 77.4

Multi-

Crystalline

Silicon

21023805 23 1035 38025 8770840 0 77.1

Cd-Te 80 62946 9 6944 44997 8954308 2.1% 78.7

Micromorph

Silicon445 11235 3 3745 64264 9033976 3.0% 79.4

Location: Rajasthan and Central Inverter. All other parameters being same

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Page 20: Solar PV Technologies

� Degradation rate

� Reliability� Area available

� O&M cost

� Bankability� Installation cost

� BoS cost such as structure,

Module TypeDegradation

Rate (%/Year)Exposure Year

Mono-crystalline

Silicon0.30 8

Multi-Crystalline

Miscellaneous Considerations for Module Selection

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� BoS cost such as structure, cable and string monitor

� As per a study by Sandia lab

the module replacement ratefor crystalline module is 0.05%

and for thin films approx. 1%

Multi-Crystalline

Silicon0.5 9

Amorphous

Silicon0.7-1.4 7-12

Cd-Te 0.70 10

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Page 21: Solar PV Technologies

Around 65% of Non-Module Costs Scale with Module Efficiency

65%

35%100%

(Rs.40/Wp)

Halving efficiency

increases non-module costs by 65% and module costs must decrease correspondingly to

maintain competitiveness on a systems level

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systems level

Efficiency

dependent non-

module

costs

Efficiency

independent non-module

costs

Total non-

module cost

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Page 22: Solar PV Technologies

c-Si reference

module12.8%

Nominal module

efficiency (%)“Normalized” module

efficiency (%)Yield at

Rajasthan(kWh/kWp)

176212.8%

Thin Film Vs Crystalline Silicon

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Micromorph Si thin

film module 7.8% 1807 8.0%

Taking into account Rajasthan irradiation and

temperature statistics, the „normalized“ efficiency of a micromorph thin film module is 8% vs.

12.8.0% for a c-Si module

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Page 23: Solar PV Technologies

Entitlement of Thin Film Module Cost TakingCrystalline Silicon System Cost as Reference

Rs.120/Wp Rs.14/Wp

Rs.41.6/Wp

26x(12.8/8.0)

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Rs.64.4/Wp

Efficiency

dependent non-

module costs

Deduced thin

film Si module

price

Efficiency

independent

non-module

costs

Total systems

cost

Thin film module shall be20% cheaper than

Crystalline silicon moduleso as to meet the system

level cost.

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Page 24: Solar PV Technologies

Choice of Inverters

� Maximize efficiency and performance

� Maximize reliability and durability� Leverage scale of mass produced AC components� Easy to install� Special training not required for installation� Less risk/hazard

Inverter CTQs

+ A large number of power pointtrackers improve the yield

+ High DC system voltage range

+ Inverter integrated withmodule

+ Module level MPPT

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Central Inverter String Inverter Micro-inverter

and Three phase is now possible

in string inverters.

+ Reduced losses in both AC andDC cable and hence higher output

+ Dispense with junction box

+ Less skilled manpower needed

+ Inverters can be placed among the

modules+ No string monitor is needed

+ Module level MPPT

+ Module level monitoring

is possible

+ DC cabling not required+ More modular

-More expensive at present

- Bankability?

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Page 25: Solar PV Technologies

Central String

Less Inverters of High

Capacity

More Inverters of Less

capacity

For 1 MW:

2 No of 500kVA each

For 1 MW:

91 No of 11kVA each

++ Standard

composite Unit of

Inverter,

Transformer Station,

Switchgears as a

++ Separate Units

as Inverters, AC

Combiner Boxes,

Communication

Cables, Transformer

Comparison of Central and String for 1 MWp Plant

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Switchgears as a

package including

Communications

Cables, Transformer

Station, Switchgears

++ Easy

for Planning and

Installation

- - Complex

and a lot of

engineering reqd.

++ Easy

to Maintain due to less

components

++ Easy

to Maintain due to

higher reliability

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Page 26: Solar PV Technologies

Layout of Central Inverter Plant of 1 MWp

28 x SMA string-monitor

7 – 8 per Main Box

8 strings per combiner box8 contacts per string monitor,

Module Power: 180 Wp

26 modules per string

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Transformer 1000 MVA

Inverter 500 HE-11

Inverter 500 HE-11

SMA concrete

station 1000 MV

including 2 inverters

including transformer

TransferStation

2 x SMA DC main box2 per Inverter

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Page 27: Solar PV Technologies

Layout of String Inverter 1 MWp Plant

. . .

96 x SMC 11000TL

1 String is 20 modules

3 strings per inverter

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Transformer 1000 MVA

AC Combiners AC Combiners

AC Combiners for Phase

Balancing, Transformer

Station Transfer

Station

2 x SMA Web box

96 x SMC 11000TL

……………

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Page 28: Solar PV Technologies

Module Mounting Configuration

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Landscape Portrait

Which is Preferred?

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Page 29: Solar PV Technologies

Portrait layoutLandscape layout

Implications

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Shadow or Snow

Shadow or Snow

One string bypassed

Both strings bypassed

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Page 30: Solar PV Technologies

Concentration PV (CPV)

Salient Features of CPV� Concentration 500x� Dual axis tracking

� Uses direct radiation

� High efficiency III-V cells

Positives� Higher energy harvesting because of

• Tracking

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• Tracking

• Lower temp. coeff. (-0.16%/deg. C)

Negatives� Not a static system

� Reliability?

� Bankability� Cost

� Area efficiency

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Page 31: Solar PV Technologies

Frequency of Outages and Impact on Energy Loss

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Page 32: Solar PV Technologies

O & M Cost (Fixed Crystalline Si as Reference)

Relative CostRelative CostRelative CostRelative Cost

O&M Activity

Fixed Crystalline

Si as the benchmark

Cd-Te Amorphous Si

Single Axis

Tracked Crystalline Si

Schedule

maintenance 1 1.2 1.4 1.5

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maintenance and cleaning

1 1.2 1.4 1.5

Unscheduled

maintenance1 1 1 2.5

Inverter

Maintenance1 1 1 1

Civil structure

and ground maintenance

1 1.5 2 1.5

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Page 33: Solar PV Technologies

Summary

• Generation over life time, capital cost and O&M are critical for economic

viability of project

• Design of Solar Power Plant is key to profitability

• Solar installation has to last for 25 years and negligence in component

selection and design may hurt in future

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selection and design may hurt in future

• Meteorological data are not accurately known nor can be predicted

with high certainty. Probabilistic approach to yield calculation is more prudent.

• One size does not fit all or a single design is not optimally suited for all

locations. An optimum solution for each location has to be designed.

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Page 34: Solar PV Technologies

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