BOOKLET ON - rdso.indianrailways.gov.in

ii

BOOKLET ON

FACTORS AFFECTING EFFICIENCY

OF SOLAR PLANTS

AND

WAYS TO IMPROVE

iii

QUALITY POLICY “We at RDSO, Lucknow are committed to maintain and update transparent standards of services to develop safe, modern and cost effective railway technology complying with statutory and regulatory requirements, through excellence in research, designs and standards by setting quality objectives, commitment to satisfy applicable requirements and continual improvements of the quality management system to cater to growing needs, demand and expectations of passenger and freight traffic on the railways through periodic review of quality management systems to achieve continual improvement and customer appreciation. It is communicated and applied within the organization and making it available to all the relevant interested parties.”

DISCLAIMER It is clarified that the information given in this booklet does not supersede any

existing provisions of Indian Standards (IS) on the subject, related matters,

and other existing provisions laid down by the Railway Board, RDSO. This is

not a statuary document and instructions given are for the purpose of

guidance only. If at any point contradiction is observed, then Indian

Standards, regulations issued by Government bodies, Railway Board/RDSO

guidelines shall be referred.

iv

FOREWORD

Limited resources and growing demand of energy poses a clear need for energy generation from alternative and renewable sources of energy. The earth is blessed with enormous amount of solar energy and it is an in-exhaustive, reliable & non-polluting source of power. Indian Railways has been continuously installing solar panels on rooftops of its various

stations and service buildings for meeting its non-traction power requirements. More than

1000 stations have been covered with solar panels on rooftop and more are in pipeline.

For powering traction network, 1.7 MW pilot solar project through solar power has been

commissioned in Bina, Madhya Pradesh in June 2020.

It is very essential to ensure optimal system performance by continuous monitoring, periodical maintenance and evaluation of output parameters. Effective operation and maintenance ensure smooth functioning, production of more energy and reliability of the system. CAMTECH, Gwalior has prepared this handbook on “Factors Affecting Efficiency of Solar Plants and Ways to Improve” which consist brief information on commercial models, factors affecting the solar power generation, ways to improve & maintenance techniques etc. It also focuses on new developments in panel cleaning. I am sure that this booklet will be useful for electrical engineers and maintenance staff

engaged in solar power generation for updating their knowledge on various efficiency

factors and maintenance techniques, improving the reliability and efficiency of solar

installations.

Jitendra Singh Principal Executive Director

v

PREFACE Concerns over global climate change, local air pollution & resource scarcity make the alternative and renewable sources of energy attractive worldwide. Solar energy is one of the best resource of renewable energy as it is inexhaustible, pollution free and accessible to all at free of cost.

Indian Railways being one of the largest electricity consumers of the country, has the responsibility to take initiative to reduce its dependence on diesel, major part of which is being imported and is a burden on economy. Indian Railways has set goal to be the first 100 percent green railway network in the world by year 2030 through deploying solar projects in their premises, including stations, parking spaces, and different buildings and workshops.

The capital investment in installing solar plants is high but the operational and maintenance cost is very low. There are so many factors which affect the output of the solar plants, these factors may be improved by proper installation, periodically cleaning and monitoring. CAMTECH has prepared this handbook on “Factors Affecting Efficiency of Solar Plants and Ways to Improve” with the objective to disseminate specific information on the subject. This book contains commercial models of solar power plant installations, brief information regarding its working, and maintenance techniques. It also contains factors affecting the power generation in solar plant including new developments in panel cleaning. Important extracts from model Power Purchase Agreement (PPA) are also included in this booklet. Technological up-gradation & learning is a continuous process. Please feel free to write

to us for any addition/ modification in this booklet. We shall highly appreciate your

contribution in this direction.

Himanshu Maheshwari

Dy. Director /Electrical

vi

CONTENT FOREWORD ................................................................................................................... iv

PREFACE ........................................................................................................................ v

CONTENT....................................................................................................................... vi

LIST OF FIGURES ....................................................................................................... viii

ISSUE OF CORRECTION SLIP ...................................................................................... x

ABBREVIATIONS .......................................................................................................... xi

CHAPTER 1 ..................................................................................................................... 1

VISION OF MINISTRY OF RAILWAYS FOR SOLAR PLANT .......................................... 1

1.1 INTRODUCTION .............................................................................................. 1

CHAPTER 2 ..................................................................................................................... 2

MODELS OF SOLAR POWER PLANT ............................................................................ 2

2.1 ON THE BASIS OF BUSINESS AND FINANCING MODEL ............................. 2

Capital Expenditure (CAPEX) Model ................................................................ 2

Operational Expense (or OPEX) Model ............................................................ 2

2.2 ON THE BASIS OF GRID CONNECTIVITY ..................................................... 3

On Grid Solar System ....................................................................................... 3

Off Grid Solar System ....................................................................................... 5

CHAPTER 3 ..................................................................................................................... 7

SOLAR POWER PLANT INSTALLED IN INDIAN RAILWAYS ......................................... 7

3.1 ROOFTOP SOLAR PLANTS ............................................................................ 7

3.2 LAND-BASED SOLAR PLANTS ....................................................................... 8

CHAPTER 4 ................................................................................................................... 10

GENERAL CONFIGURATION OF SOLAR ARRAY AND FACTORS AFFECTING POWER GENERATION IN SOLAR PV PLANTS............................................ 10

4.1 GENERAL CONFIGURATION OF SOLAR ARRAY ........................................ 10

4.2 FACTORS AFFECTING THE POWER GENERATION EFFICIENCY OF SOLAR PV PLANTS ....................................................................................... 10

Soiling ............................................................................................................. 10

Shading .......................................................................................................... 13

Other Factors Affecting Efficiency of Solar Power Plant. ................................ 19

CHAPTER 5 ................................................................................................................... 24

vii

MAINTENANCE AND PERFORMANCE MONITORING ................................................ 25

5.1 MAINTENANCE .............................................................................................. 25

Preventive Maintenance ................................................................................. 25

Corrective Maintenance .................................................................................. 28

DC Earth Fault Identification in a Multi-string PV Plant ................................... 28

Spare Parts ..................................................................................................... 31

5.1.5 New Development in Module Cleaning ........................................................... 31

5.2 PERFORMANCE MONITORING .................................................................... 34

Key Performance Indicators (KPI) of Solar Plant ............................................ 34

CHAPTER 6 ................................................................................................................... 38

MODEL POWER PURCHASE AGREEMENT (MPPA) .................................................. 38

6.1 IMPORTANT PROVISIONS OF PPA ............................................................. 38

Railway Grants Permission to SPD ................................................................. 38

Addition Facility to be Provided by SPD .......................................................... 38

Capacity Utilization Factor (CUF) Guarantee .................................................. 39

Shortfall in Generation .................................................................................... 39

Generation Factor ........................................................................................... 40

REFERENCES .............................................................................................................. 41

CONTACT US ............................................................................................................... 42

viii

LIST OF FIGURES Figure 1: Basic Business Model of CAPEX type Solar PV plant in IR .............................................. 2

Figure 2: Basic Business Model of OPEX type Solar PV plant in IR ................................................ 3

Figure 3: Simple on Grid Solar System ............................................................................................ 3

Figure 4: Energy generation & consumption in Net metering ........................................................... 4

Figure 5: Simple on Grid Solar System ............................................................................................ 5

Figure 6: On The Basis Of Load Solar Plant Installed In Indian Railways ........................................ 7

Figure 7: Example of Solar Array Configuration ............................................................................. 10

Figure 8: In General Output Generation Comparison of Daily-cleaned Panel and Uncleaned Panel. ........................................................................................................................................ 11

Figure 9: Soiling Ratio Data by Dust IQ ......................................................................................... 12

Figure 10: (a) un-shaded module (b) Non-functioning of Bypass diode & output power ..................... 13

Figure 11: (a) Shading in starting one set of cells (b) Functioning of one Bypass diode & output power 14

Figure 12: (a) Shading in starting two set of cells (b) Functioning of two Bypass diode & output power 14

Figure 13: (a) Shading in all set of cells (b) Functioning of all three Bypass diode & output power ....... 15

Figure 14: (a) Shading in starting one set of cells, (b) Functioning of one Bypass diode & output power ........................................................................................................................................ 15

Figure 15: (a) Shading in starting two set of cells (b) Functioning of two Bypass diode & output power 16

Figure 16: (a) Shading in last two set of cells (b) Functioning of two Bypass diode & output power ..... 16

Figure 17: (a) Shading in last one set of cells (b) Functioning of one Bypass diode & output power ... 17

Figure 18: Two Shaded Cells in a Module belonging to (a) same set (b) different set ..................... 17

Figure 19: Change in IV & PV Curve Due to Two Shaded Cells in a Module belonging to (a) same set (b) different set .......................................................................................................... 18

Figure 20: Formation of hotspot in a module .................................................................................... 18

Figure 21: Use of Bypass Diode in a Module ................................................................................... 19

Figure 22: Tilt Angle of Solar Panel ................................................................................................. 19

Figure 23: Importance of Azimuth Angle .......................................................................................... 20

Figure 24: Change in IV Characteristic Due to Change in Solar Irradiation ..................................... 21

Figure 25: Change in IV Characteristic Due to Change in Temperature .......................................... 21

Figure 26: Leakage of Charges within Module ................................................................................. 22

Figure 27: Paths of Leakage current in a module ............................................................................ 22

Figure 28: EL (Electroluminescence) Image of Solar Module Before and After PID Test ................ 23

Figure 29: Change in IV Characteristic during PID Test................................................................... 23

Figure 30: Linear Performance Warranty of Solar Module ............................................................... 24

Figure 31: Measurement of VOC & ISC .............................................................................................. 27

Figure 32: IV Characteristic of Module ............................................................................................. 27

ix

Figure 33: Thermographic Image of Solar Module ........................................................................... 28

Figure 34: DC earth fault between cable of Module M3 & M4 of String-1 ........................................ 29

Figure 35: DC earth fault between cable of string-1 and inverter (in DC cable trench) .................... 30

Figure 36: Pressurized Water Cleaning System .............................................................................. 32

Figure 37: Robotic Cleaning and Effect on Power Generation ......................................................... 34

Figure 38: Air Spectrum ................................................................................................................... 35

Figure 39: Current Voltage (IV) curve of a solar cell. ....................................................................... 36

Figure 40: Change in IV Curve Due to Change in External & internal Parameters .......................... 37

x

ISSUE OF CORRECTION SLIP

The correction slips to be issued in future for this handbook will be numbered as follows:

CAMTECH/ E/EP-03/2021-22/Solar Maintenance/1.0/C.S. # XX date---

Where “XX” is the serial number of the concerned correction slip

(starting from 01 onwards).

CORRECTION SLIPS ISSUED

Sr. No. Date of Issue Page no. & Item no. modified Remarks

xi

ABBREVIATIONS

ABBREVIATION FULL FORM

AC Alternating Current

ACDB Alternating Current Distribution Board

AM Mass of the air

DC Direct Current

CERC Central Electricity Regulation commission

SERC State Electricity Regulation commission

CAPEX Capital Expenditure

CUF Capacity Utilization

DCDB Direct Current Distribution Board

DISCOM Distribution Company

EL Electroluminescence

EPC Engineering, Procurement and Construction

EVA Ethylene Vinyl Acetate

FiT Feed-In-Tariff

IR Indian Railways

IV Current Voltage

KPI Key performance indicators

kWh or kWhr Kilowatt Hours

KWp Peak Kilowatt

LC Level Crossing

LED Light Emitting Diode

MPPA Model Power purchase agreement

MPP Maximum Peak Power

MW Megawatt

xii

O&M Operation and Maintenance

OPEX Operational Expense

PH Potential of Hydrogen

PID Potential Induced Degradation

PPA Power purchase agreement

PR Performance Ratio

PV Photovoltaic

REMCL Railway Energy Management Company Ltd

RESCO Renewable Energy Services Company

SAPS Stand-alone Power System

SPD Solar Power Developer

SR Soiling Ratio

SSY Solar Specific Yield

STC Standard Test Conditions

CAMTECH/E/2021-22/EP-03/Solar Maintenance/1.0

Booklet on Factors Affecting Efficiency of Solar Plants & Ways to Improve 1

CHAPTER 1

VISION OF MINISTRY OF RAILWAYS FOR SOLAR PLANT

1.1 INTRODUCTION

Indian Railways, known as for one of the largest electricity consumer of the country, is expanding their routes and trains very fast every year, so the power demand is also increasing at massive speed, which is expected to put tremendous pressure on the country’s’ power supply.

This considerable consumption will also add to higher power costs in future. Thus, the IR is setting a goal to reduce the operational expenses & be the first 100 percent green railway network that means net Zero Carbon emission network in the world by year 2030.

Working towards this goal, IR is making efforts to reduce its dependence on fossil fuels and is increase the penetration of renewable energy sources.

One significant pillar of the plan is to achieve 100 per cent electrification of the IR network by December 2023.

The second pillar is using solar power to meet its electricity needs and having an environment-compliant infrastructure through deploying solar projects in their premises, including stations, parking spaces, and different buildings and workshops.

Ministry of Railways & RITES Ltd. form a company named Railway Energy Management Company Ltd (REMCL) as a Joint Venture with an aim to increase the renewable energy resources (wind and solar) through Exploring the opportunities, planning, tendering / bid processing and implementation of renewable energy projects on behalf of Indian Railways. As a result, solar power is now gaining significant traction in the railway infrastructure, which includes the rooftop, land based as well as the other utility-scale segments.


2 Booklet on Factors Affecting Efficiency of Solar Plants & Ways to Improve

CHAPTER 2

MODELS OF SOLAR POWER PLANT

2.1 ON THE BASIS OF BUSINESS AND FINANCING MODEL

Capital Expenditure (CAPEX) Model

In early days of the Solar Mission, installations were driven and funded primarily by the consumer. In this model, consumer may generally hire a solar EPC company who provide turnkey installation of entire solar power system and hand over assets to consumers. Annual operation and maintenance (O&M) of plant may be done by EPC company as per mutual agreement or do by Consumer itself. Indian railway has also installed many solar power plants through this model.

Figure 1: Basic Business Model of CAPEX type Solar PV plant in IR

Operational Expense (or OPEX) Model

The alternative model, involving a third-party specialist organization (called a Renewable Energy Services Company, or RESCO), involves installation on an operational expense (or OPEX) basis. OPEX projects are gaining ground in the recent years. Most mature markets are primarily driven by financed installations supported by RESCO companies.

The Consumer will effectively buy electricity from two sources: daytime power (in case of a solar system) from the RESCO, and remaining daytime & night-time power from the DISCOM. Further, in accordance with the agreement between the RESCO and Consumer, the RESCO is responsible for all O&M service through the life of the contract, later the responsibility for O&M may be shifted to the Consumer. Consumer does not have to pay for capital expenditure, and has to do nothing with O&M but pay the RESCO for units of electricity consumed from the Renewable Energy based on power purchase agreement at mutually agreed price.



Figure 2: Basic Business Model of OPEX type Solar PV plant in IR

2.2 ON THE BASIS OF GRID CONNECTIVITY

On Grid Solar System

On-grid, also known as a grid-tie or grid-feed solar system, is the most used option. These systems do not need batteries and use either solar inverters connected to the public electricity grid (DISCOM). Any excess solar power that one generates is exported to the grid. In exchange, a consumer is paid a feed-in-tariff (FiT) or given equivalent credits based on net metering. When the solar system is not operating or one is using more electricity than the system is producing like in hot weather conditions, one can redeem the credits by importing or consuming electricity from the grid. An on-grid system can power all appliances including water pump, motor, lights, etc. These are the most cost-effective and simplest systems to install and are more widely used by homes and businesses.

Figure 3: Simple on Grid Solar System



2.2.1.1 Major components of on grid rooftop solar system

Solar PV Modules/Solar Panels

The Solar PV modules/Solar Panels convert solar energy to DC (direct current) electrical energy. They are available in different technologies such as crystalline silicon, thin film silicon, etc. Crystalline Silicon Solar PV panels are most commonly used in solar rooftop system. Multiple panels are connected together to form arrays as per the desired capacity of the system.

Inverter

Inverter converts DC output of Solar PV panels into AC power. Inverter also synchronizes with the grid so that generated power from the module can be injected into the grid.

Module mounting structure

The module mounting structure, is the support structure that holds the Solar PV panels in place for full system life and is exposed to all weather conditions. These are normally fixed at particular angle and orientation in case of solar rooftop system.

Net Meter

Meter is used to record the generation or consumption of electricity. Net-Meter is used to keep track of the electricity that solar PV system injects to utility grid and the electricity that is drawn from the utility grid.

Balance of System

These consist of cables, switchboards, junction boxes, earthing system, circuit breaker, fuses, lightning protection system etc.

2.2.1.2 Concept of net metering

Figure 4: Energy generation & consumption in Net metering



(i) Case-I

In case generation of power from Renewable Energy based Power Project equals the power requirement of the Net metering consumer, there is no export or import of power from the grid. Hence, net billing units for this type of consumers will be zero.

(ii) Case-II

In case generation of power from Renewable Energy based Power Project is greater than the power requirement of the Net metering consumer, additional power generated can be supplied to the grid and settled against future surplus within the settlement period, as per the Regulations.

(iii) Case-III

In case generation of power from Renewable Energy based Power Project is less than the power requirement of the Net metering consumer, additional power required can be imported from the grid and settled at the prevailing DISCOM rate.

Off Grid Solar System

Off-grid, also known as a stand-alone power system (SAPS), is more for personal use as it is not connected to the grid and requires battery storage. This system can provide power for critical loads even when there is a power outage. These solar systems need to be designed to generate enough power throughout the year and have enough battery capacity to meet the requirements, even in peak winter when there is generally much less sunlight. Off-grid systems are also much more expensive due to the high cost of batteries.

Figure 5: Simple on Grid Solar System



2.2.2.1 Major components of Off grid solar system

Most of the components used in this system are same as in the On Grid solar system such as PV Panel, Inverter, cables, switchboards, junction boxes, earthing system, circuit breaker, fuses and lightning protection system. Apart from these following components are also used:

Charge Controller

A charge controller determines how much current should be injected into the batteries for its optimum performance. As it determines the efficiency of the entire solar system as well as the operating life of the batteries, it is a critical component. The charge controller protects the battery bank from overcharging.

Battery Bank

There may be periods when there is no sunlight. Evenings, nights and cloudy days are examples of such situations beyond our control. In order to provide electricity during these periods, excess energy, during day, is stored in these battery banks and is used to power loads whenever required.



CHAPTER 3

SOLAR POWER PLANT INSTALLED IN INDIAN RAILWAYS

Figure 6: On The Basis Of Load Solar Plant Installed In Indian Railways

3.1 ROOFTOP SOLAR PLANTS

In order to harness the untapped potential of solar rooftop at railways buildings, stations, hospitals etc. Indian Railways has been continuously installing solar panels on rooftops of its various stations and service buildings so as on Railway coaches for meeting its non-traction and traction power requirements respectively. More than 1000 stations have been covered with solar panels on rooftop and more are in pipeline. Some of the examples of such type of solar power plants are given below: a) 3MW Solar power plant on Roof Top of Howrah Railway station

b) Solar Panels on roof top of Railway Coaches (Science Express)



3.2 LAND-BASED SOLAR PLANTS

Indian Railways has a potential of generation of huge solar power by utilising its vacant land parcels to set up land-based solar plants for its traction and non-traction power requirement. IR start setting up land-based solar plants on vacant. Some of the example of such type of solar power plants are given below: a) 3 MW Solar Land Based Project at Modern Coach Factory, Raebareli

b) 1.7 MW Bina Solar Plant Solar Project on land along Railway track

c) 2 MW solar project at Diwana, Haryana on land along the railway track



d) 1HP Solar Pump Provided at Sri Dungargarh in Bikaner Division (North Western Railway)

e) Solar Water Heater at Running Room, Jaipur (North Western Railway)

f) Hybrid system for lighting at LC Gate at Bhachau station (Western Railway)

g) Solar based streetlight in Railway colony



CHAPTER 4

GENERAL CONFIGURATION OF SOLAR ARRAY AND FACTORS AFFECTING POWER GENERATION IN SOLAR PV PLANTS

4.1 GENERAL CONFIGURATION OF SOLAR ARRAY

Figure 7: Example of Solar Array Configuration

4.2 FACTORS AFFECTING THE POWER GENERATION EFFICIENCY OF SOLAR PV PLANTS

Soiling

Losses due to soiling (dust or snow and bird droppings etc.) on the modules for long periods depend on the environmental conditions, rainfall frequency, and cleaning strategy as planned in the Maintenance. As this loss can have an important impact on the performance ratio, it is essential to monitor and quantify the soiling loss.



Some of the example of comparison of power generation between cleaned and uncleaned PV:

a. Panel having bird droppings and cleaned panel

There is clear difference in power generation between cleaned and uncleaned PV panel.

b. Panels of same rating, panel-1 cleaned daily while panel-2 cleaned after some days

Figure 8: In General Output Generation Comparison of Daily-cleaned Panel and Uncleaned Panel.

4.2.1.1 Device to measure the soiling on panel

Most common cause of less generation in PV panel is soiling which is a slow process. So it is very important to get the data of soiling rate at the particular location to plan the effective cleaning so that maximum output can be generated.

To ensure optimal economic plan for cleaning of solar PV modules vis-a-vis cleaning cost

vs soiling loss is very important and for calculating this effectively by using new development in solar technology is measurement of soiling on PV modules.

Example of such device for measurement of soiling is DustIQ, which works on the Optical

Soiling Measurement principle, which allows it to work independently of the fluctuating sun that means it can measure the soiling in day time as well as in night time.

DustIQ measure and store the data of soiling accumulation on panel with the help of two photo diode and one LED provided in it as shown below.



When a DustIQ is completely clean the sensors are not measuring zero reflection of the pulsed blue LED light. There is some reflection from the glass. With soiling added there will more reflection and the increase is translated into transmission loss.

Stored data of soiling measurement in device can be downloaded to get the graphical view.

Example of data collected by vertically placed device (DustIQ)

Figure 9: Soiling Ratio Data by Dust IQ

From the graph it is very clear that top sensor is much cleaner than the bottom sensor. A reason could be that the top sensor is cleaned by dew run off and that the soiling ends up on the bottom sensor.

Soiling ratio values need to be divided by 10 to get soiling ratio (%) in percentage of above figure (9).

4.2.1.2 Soiling Ration

Soiling Ratio (SR) is defined as the ratio in short circuit current (Isc), or maximum power, (Pmax), between a soiled and a cleaned PV panel.

For a completely clean panel the SR is 100 % and for a soiled panel it is closer to 0 %.



4.2.1.3 Transmission Loss

Transmission loss is the loss of transmission of solar irradiation to the solar module. Dust deposited on module reduces the light transmission, and hence the incident solar irradiation decrease. Current is highly dependent on the incident light. Hence, the reduction of current so the power is obvious from dust-covered PV panels. Reduced incident radiation may slow down the temperature enhancement of the PV panels thus, the open-circuit voltage is not much affected.

𝑇𝑟𝑎𝑛𝑠𝑚𝑖𝑠𝑠𝑖𝑜𝑛 𝐿𝑜𝑠𝑠 (%) = 100 – 𝑆𝑜𝑖𝑙𝑖𝑛𝑔 𝑟𝑎𝑡𝑖𝑜 (%)

Shading

Shading occur due to mountains, buildings, or any cause on rows or column of cells in a module permanently or temporary, reduces the output power significantly.

This may loss cause a hotspot in cell and may damage the module.

Some of the examples of shading

4.2.2.1 Effect of shading on generation of PV panel

When an entire panel is under shadows or in the shade, it simply stops generating power. However, if panel is under partial shading then the power generation depend on the orientation of panel and shadow area.

4.2.2.1.1 Power Generation in unshaded PV panel

Figure 10: (a) un-shaded module (b) Non-functioning of Bypass diode & output power



4.2.2.1.2 Effect of partial shading on orientation of panel

If permanent shading present on module all day and location of modules cannot be changed so orientation of modules are very important because sun continuously move throughout the day and shading changes the position on module. Due to shading power generation will definitely effected but generation may be improved by placing module in different orientation.

For Example there is same panel placed in portrait and landscape position to changing

shading throughout the day with power output are given below:

(i) Shading on PV panel placed in portrait orientation

a) Case-I: Shadow covers the surface area of one or more cell of starting one set of columns only (bypass diode BP-1 connected between them), then the output will reduce by 1/3rd of total power output of un-shading module.

Figure 11: (a) Shading in starting one set of cells (b) Functioning of one Bypass diode & output power

b) Case-II: Shadow covers the surface area of one or more cell of starting two set of columns only (bypass diodes BP-1 & BP-2 connected between them), then the output will reduce by 2/3rd of total power output of un-shading module.

Figure 12: (a) Shading in starting two set of cells (b) Functioning of two Bypass diode & output power



c) Case-III: Shadow covers the surface area of one or more cell of all three set of columns (bypass diodes BP-1, BP-2 & BP-3 connected between them), then the output will reduce to Zero.

Figure 13: (a) Shading in all set of cells (b) Functioning of all three Bypass diode & output power

(ii) Shading on PV panel placed in landscaped orientation

a) Case-I: Shadow covers the surface area of one or more cell of starting one set of columns only (bypass diode BP-1 connected between them), then the output will reduce by 1/3rd of total power output of un-shading module.

Figure 14: (a) Shading in starting one set of cells, (b) Functioning of one Bypass diode & output power



b) Case-II: Shadow covers the surface area of one or more cell of starting two set of

columns only (bypass diodes BP-1 & BP-2 connected between them), then the output will

reduce by 2/3rd of total power output of un-shading module.

Figure 15: (a) Shading in starting two set of cells (b) Functioning of two Bypass diode & output power

c) Case-III: Shadow covers the surface area of one or more cell of last two set of columns only (bypass diodes BP-2 & BP-3 connected between them), then the output will reduce by 2/3rd of total power output of un-shading module.

Figure 16: (a) Shading in last two set of cells (b) Functioning of two Bypass diode & output power



d) Case-IV: Shadow covers the surface area of one or more cells of last set of columns (bypass diode connected between them), then the output will reduce by 1/3rd of total power output of un-shading module.

Figure 17: (a) Shading in last one set of cells (b) Functioning of one Bypass diode & output power

With help of above both the situations one thing is very clear that just changing the orientation of same module on same location may improve the power generation.

Here we see that in landscape orientation, module generates more power because there is no shading on all three sets of cell throughout the day.

Another example of Impact of Partial Shading on a Series of Strings (Module)

• Panel Model: Kyocera KC70

• Panel Layout: 2 Sets of series connected cells (18 Cells in each set) & One bypass diode per set

• Two Shaded Cells belonging to (a) same set (b) different set.

Figure 18: Two Shaded Cells in a Module belonging to (a) same set (b) different set



Figure 19: Change in IV & PV Curve Due to Two Shaded Cells in a Module belonging to

(a) same set (b) different set

The presence of Bypass diodes in the structure of a solar panel, creates a separate way for the current from the strings with 'un-shaded' cells to pass, thus avoiding the passing of excess current through the part of the panel that is under shade. Large amount of output can be experiences even with a bypass diode.

4.2.2.1.3 Formation of Hotspot in a Module

Hotspot formation refers to a localized heating condition within a PV module, which may occur due to mismatch in solar cells, partial shading or internal cell defects.

Figure 20: Formation of hotspot in a module

This mainly happens when the terminal of module are connected and the power generated

from unshaded cell dissipated across the shaded cell & cell operates in the reverse bias

condition. These hotspots not only lead to long-term degradation but can also pose a

serious safety threat to PV systems.



Bypass diodes are often used for mitigation of hotspots, however in certain situations where

shading is not very high, hot spot can still occur.

Figure 21: Use of Bypass Diode in a Module

In the light of the above point, it can be concluded that infrared thermography is extremely crucial in capturing the module thermal profile and can potentially indicate the faults within the modules or hotspots.

Other Factors Affecting Efficiency of Solar Power Plant.

4.2.3.1 Incident angle

This is the angle between the line that points to the sun and the line that is normal to the surface of the panel.

Solar panels are most efficient when pointing perpendicular to the sun light. The incident angle loss accounts for radiation reflected from the front glass in the case of the light striking when it is not perpendicular.

Figure 22: Tilt Angle of Solar Panel

4.2.3.2 Position of PV panel

It is also very important that the PV should be always placed in a position so that maximum period during the whole day solar irradiation may be collected. To get the maximum sun time



PV panel should be placed in south facing direction because sun rise in east side and moving towards south and sun down in west side.

If the panel facing the different direction other than south then the PV panel don’t generates the power whole day.

For Example

a) Panel facing south

b) Panel facing South-west

Figure 23: Importance of Azimuth Angle

In fig. (b), PV panel receive solar irradiation at 11:00 Hrs while in fig. (a) PV panel receive solar irradiation at 6:00 AM, so one thing is very clear that sun time in a day is 05 hrs more in the case of south facing PV panel so the output.



4.2.3.3 Low irradiance

The conversion efficiency of a PV module generally reduces at low light intensities. This causes a loss in the output of a module compared with the STC (1,000W/m2). This “low irradiance loss” depends on the characteristics of the module and the intensity of the incident radiation.

Figure 24: Change in IV Characteristic Due to Change in Solar Irradiation

This graph of IV-characteristic is clearly shows that the output power will reduced with reduction in irradiance. Pyranometer and Pyrheliometer

An instrument used for measurement of solar irradiance on a horizontal plane.

4.2.3.4 Module temperature

The IV-characteristics of a PV module are determined at STC of 25˚C. For every degree rise

in Celsius temperature above this standard, crystalline silicon modules reduce in efficiency

and vice versa.

Figure 25: Change in IV Characteristic Due to Change in Temperature



PV cell is made of a semiconductor and have the negative temperature coefficient for voltage

& power and positive temperature coefficient for current. That means its voltage & power

increases with fall in temperature or decreases with rise in temperature and current increases

with rise in temperature or decreases with fall in temperature w.r.t. ambient temperature.

4.2.3.5 Potential induced degradation (PID)

Some of the generated charges are leaked within the module between semiconductor material and module elements (eg. Glass, EVA, Frame) and these charges are discharged to earth through aluminum frame.

This is due to high potential difference between cell and frame (at earth potential). Whenever a conductive path is form between cell and frame through Encapsulation, glass, back sheet, a leakage current will flow from cell to earth. This is known as PID.

Figure 26: Leakage of Charges within Module

Figure 27: Paths of Leakage current in a module



4.2.3.5.1 Effect of PID in IV Characteristic of Solar Module

(a) PV Cell Before PID Test (b) PV Cell After PID Test

Figure 28: EL (Electroluminescence) Image of Solar Module Before and After PID Test

Figure 29: Change in IV Characteristic during PID Test

From the above fig, it can be seen that the Maximum Peak Power (MPP) point decreased largely as compared to Voc & Isc. PID effect the peak power output the most and very less effect on Voc & Isc.

4.2.3.6 Degradation

The performance of a PV module decreases with time. Panels slowly decline in output over the years as micro-cracks develop in the silicon solar cells and electrical connections deteriorate due to Thermal cycling, Dynamic Mechanical Load, Humidity and other environmental conditions.



Generally, A solar panel’s performance warranty will typically guarantee 90% production at 10 years and 80% at 25 years considered by the manufacturers.

Figure 30: Linear Performance Warranty of Solar Module

Apart from above mentioned factors affects the power generation efficiency there are

some other factors that also decrease the efficiency which are downtime of plant,

AC&DC cable losses, Grid availability etc.



CHAPTER 5

MAINTENANCE AND PERFORMANCE MONITORING

5.1 MAINTENANCE Maintenance ensures the smooth functioning of solar plant as well as enables the solar power plant to produce the maximum amount of energy throughout its operational life. Maintenance of solar plant, in case of CAPEX model will be done by the Consumer itself. While in

the case of OPEX model O&M of plant throughout the contract period is done the RESCO as per

Power purchase agreement (PPA).

It may be further divided into two parts

(i) Preventive maintenance

(ii) Corrective maintenance

Preventive Maintenance

Preventive maintenance is generally carried out at regular intervals and planned in advance accordance with the manufacturer’s recommendations, and as required by equipment warranties.

Some of the general preventive maintenance tasks are

5.1.1.1 Module cleaning

Module cleaning is a simple but important task. In the event of module cleaning, consideration should be given to the following:

Environmental and human factors (for instance, autumn fall debris and soiling from local agricultural and industrial activities).

Weather patterns: cleaning during rainy periods is less likely to be required.

Dust carried from deserts by wind.

Solid particle in coastal areas.

Dust caused by vehicular traffic.

If the system efficiency is found to be below the expected level, then the cleanliness of the modules should be checked and cleaning conducted as necessary.

5.1.1.2 Inverter servicing

Generally, inverter faults are the most common cause of system downtime in Solar PV power plants. Therefore, the preventive maintenance of inverters should be treated as a centrally important part of the maintenance strategy. The maintenance requirements of inverters vary with size, type and manufacturer. The specific requirements of any particular inverter should be confirmed by the manufacturer and used as the basis for planning the maintenance. Regular preventative maintenance for an inverter should, as a minimum, include:

Visual inspections.

Cleaning/replacing cooling fan filters.



Removal of dust from electronic components.

Tightening of any loose connections.

Any additional analysis and diagnostics recommended by the manufacturer.

5.1.1.3 Junction or string combiner box

All junction boxes or string combiner boxes should be checked periodically for water ingress, dirt or dust accumulation and integrity of the connections within the boxes. Loose connections could affect the overall performance of the PV plant. Any accumulation of water, dirt or dust could cause corrosion or short circuit within the junction box.

5.1.1.4 Structural integrity

The module mounting assembly, cable conduits and any other structures built for the solar PV power plant should be checked periodically for mechanical integrity and signs of corrosion. This will include an inspection of support structure foundations for evidence of erosion from water run-off.

5.1.1.5 Hot spots in junctions/ connections

Potential faults across the PV plant can often be detected through thermography. This technique helps identify weak and loose connections in junction boxes and inverter connections, which is a common problem in hot climates where large variations between day and night temperatures can cause contacts to loosen. Thermography may also detect hot spots within inverter components and on modules that are not performing as expected. A trained specialist should conduct thermography using a thermographic camera at least on an annual basis.

5.1.1.6 Balance of plant

The remaining systems within a solar PV power plant, including the monitoring and security systems, auxiliary power supplies, and communication systems, should be checked and serviced regularly. Communications systems within and externally connected to the PV plant should be checked for signal strength and connection.

5.1.1.7 Vegetation control

Vegetation control and grounds keeping are important scheduled tasks for solar PV power plants. Vegetation (for example, long grass, trees or shrubs) has the potential to shade the modules and reduce performance. Prudent grounds keeping can also reduce the risk of soiling on the modules from leaves, pollen or dust.

5.1.1.8 Important parameters to be measured during maintenance

Measurement of Open circuit Voltage (Voc),

Short circuit current (Isc),

Current Voltage (IV) - curves of each module

5.1.1.8.1 Measurement of open circuit voltage (Voc)

Measure the Voc of individual module to check the generated voltage matches with other modules connected in series and compare with rated voltage of module.

This is measured by connecting leads of DC multimeter with (+) ve and (-) ve output terminal of module.



5.1.1.8.2 Measurement of short circuit current (Isc)

Measure the Isc of individual module to check the generated current matches with other modules connected in series and compare with rated current of module.

This is measured by DC tong tester by connecting the (+) ve and (-) ve output terminal together of module and placing it in tong tester loop or by connecting an ammeter in series.

Figure 31: Measurement of VOC & ISC

5.1.1.8.3 Measurement of current-voltage (IV) curve

This curve gives the actual performance of a module and by comparing the curve with ideal IV-curve of module is can be easily say that module is performing good or required attention for identification of less power generation.

IV-curve is traced by IV tracer available in market by just connecting the device to terminal of module. It test the module from rated Voc to rated Isc.

Figure 32: IV Characteristic of Module

5.1.1.9 Thermography

Hot spot cannot be visible by normal eyes, so thermography to be done to hotspot in solar module. Observation of thermographic images helps to identify the probable causes of hotspot and by the immediate corrective action we can avoid the failure of PV system.

Short circuit current test (ISC) should not be done on String of Modules because of high current may damage the modules. This test is to be done on Individual module only.



Thermographic images can also show some examples of possible findings

Fig: a) The temperatures in the lowest Fig: b) Cell string is too hot, hot spot, bypass cell row is caused by dirt deposit. diode activated.

Figure 33: Thermographic Image of Solar Module

Corrective Maintenance

Corrective maintenance is carried out in response to failures. As such, the key parameters when considering corrective maintenance are diagnosis, speed of response and repair time. Most common corrective maintenance requirements include: Tightening cable connections that have loosened. Replacing blown fuses. Repairing lightning damage. Repairing equipment damaged by intruders or during module cleaning. Rectifying Data Acquisition system faults. Repairing mounting structure faults. Rectifying tracking system faults if installed.

DC Earth Fault Identification in a Multi-string PV Plant DC cables available in solar system are sometimes get earthed due to insulation failure. These result in loss of generation and safety hazards. Many inverters give the status or indication for DC faults, so to identify the location of earth fault between the modules or between string & inverter can be done by a very simple method of DC circuit theory using Multimeter.

For example suppose 07 modules with Vmp=35 V connected in series to form a string (Voc=245V) and output of string connected to inverter. Also, consider that 03 strings are connected to inverter.

The optimum frequency of Preventive maintenance can be determined by

assessing the costs and benefits of conducting the procedure.



Case (a): DC earth fault exists between Module M3 & M4 of String-1

Figure 34: DC earth fault between cable of Module M3 & M4 of String-1

Step-1: Open the output leads of strings connected to inverter

Step-2: Set the Multimeter on DC setting for measurement of string voltages

Step-3: Measure Voc of all individual strings

Step-4: Measure the Voltage between (+) ve or (-ve) terminal of string and system earth.

(i) If the measured value of Voltage of string is continuously dropping then it means that DC cable of this string is healthy.

(ii) If the measured value of Voltage is fixed on a value then it means there is earth fault in DC cable of this string.



Step-5: Compare the measured voltage between (+) / (-) ve terminal of faulty string and system earth with Voc of that strings.

(i) In Case (a), Voltage measured between (+) ve terminal of faulty string and system earth will be approx. 4/7 of Voc of that string and Voltage measured between (-) ve terminal of faulty string and system earth will be approx. 3/7 of Voc of that string. The result clearly indicates that the fault in DC cable is between 3rd and 4th module.

Case (b): DC earth fault exists between string-1 and inverter (in DC cable trench).

Figure 35: DC earth fault between cable of string-1 and inverter (in DC cable trench)



Step-1: Open the output leads of strings connected to inverter

Step-2: Set the Multimeter on DC setting for measurement of string voltages

Step-3: Measure Voc of all individual strings

Step-4: Measure the Voltage between (+) ve or (-ve) terminal of string and system earth.

(iii) If the measured value of Voltage of string is continuously dropping then it means that DC cable of this string is healthy.

(iv) If the measured value of Voltage is fixed on a value then it means there is earth fault in DC cable of this string.

Step-5: Compare the measured voltage between (+) / (-) ve terminal of faulty string and system earth with Voc of that strings.

In case (b), Voltage measured between (-) ve terminal of faulty string and system earth will be equal to Voc of that string and Voltage measured between (+) ve terminal of faulty string and system earth will be 0. The result shows that the fault is in the (+) side DC cable between the string and inverter.

Spare Parts

Adequate number of spare parts may be held based on previous experience of failures for reducing the down time of solar plant there by reducing opportunity loss for generation. The spares can be planned based on size of plant, local availability of replacement part, commonly failed parts.

5.1.5 New Development in Module Cleaning

5.1.4.1 Pressurised water cleaning

Water cleans dust and dirt and other particles deposited on the module surface very effectively.

To clean the module just pouring water on top of module by mug or bucket is not good practice due to wastage of large amount of water. So to save the water and clean the module efficiently & effectively, spraying or pressurised water to be used. Following points to be keep in mind for water cleaning

Hard water for cleaning should be avoided.

PH of water should be neutral or neither to acidic nor to alkaline i.e. nearby 7.

Module should be cleaned in low solar irradiation.

Temperature of water should not be too high or too low as compared to panel.

Pressure of water at nozzle should be too high so that micro-cracks may be developed in module over the time.

Don’t wash backside of module.

Authorized cleaning agent as advised by manufactures may be used

Domestic detergents and soaps should be avoided.



Some example of pressurized water cleaning

Fig: a) Manual water cleaning with pipe Fig: b) Water sprayer mounted to moving

with hose nozzle machine with compressor

Fig: c) Self-cleaning with High Pressure Sprinkler Cleaning System

Fig: d) Solar cleaning system using water solar pump hose nozzle for large PV plant

Figure 36: Pressurized Water Cleaning System



Fig: d) Shows the system consists of water Solar Pump and a device. There is water spraying nozzles on the top of every panel that will spray high pressure water on the panel in order to clean it. The device has a microcontroller unit which is programmed such that, the whole water pressure, created by Solar Pump, is applied to each and every water spraying section individually. So high-pressure water is sprayed to every solar panels row one by one in order to clean every panels in solar power plant. The device also consist a timer, which enable system on/off automatically to this system. Disadvantage:

(i) This cleaning method preliminary requires demineralized water (neutral PH) for cleaning. This would be a real challenge in water deficit places such as Rajasthan, Northern Gujarat etc. means water is not abundantly available everywhere & the lack of water makes it difficult to clean the modules.

(ii) Another problem with water cleaning is that sometimes dust particles deposited to edges of panel & this cause creation of the hotspot in that area of modules and further it may damage the module if not cleaned properly.

(iii) Cleaning with water increases the risk of electric shock.

5.1.4.2 Pressurized air cleaning

Sometimes due to unavailability of water, the developer may source water from local water bodies, which could lead to crisis (especially during summers). For such reasons, the pressurized air cleaning method could be of utmost importance.

In this automated and water-less self-cleaning system a slippery coating is provided over the panels, so dust does not allow dust to stick and an air compressors installed helps in blowing away the dust. The entire process is done without water or human interventions automatically, and that too multiple times in a day.

5.1.4.3 Robotic cleaning

Utilizing autonomous robots is one of the promising ways to efficiently clean PV panels. Several robotic technologies have entered the market that provides a cost-effective method to clean solar panels as compared to manual cleaning.

Robotic is effective method to clean module faster with uniform cleaning in a large solar PV plant.

Example of robotic cleaning as given below

Fig: a) Robotic cleaning Fig: b) Robotic cleaning



Fig:c) Robotic cleaning Fig:d) Comparison of generation of module due to robotic cleaning and manual cleaning for same solar irradiation.

Figure 37: Robotic Cleaning and Effect on Power Generation

5.2 PERFORMANCE MONITORING

The most practical indicators of the performance of the solar PV system can be obtained from the remote monitoring and data logging software supplied by inverter manufacturers. The data logging software will record daily, monthly, and annual output which can be used for comparison of the actual system performance against the expected system performance.

Key Performance Indicators (KPI) of Solar Plant

KPIs plays important role in efficient planning of operation and maintenance to meet desired requirements and to increase the economic life of your plant. So to track the performance of solar PV plant following KPI should be checked at regular interval as required:

I. Capacity Utilization Factor (CUF)

II. Performance Ratio (PR)

III. Solar Specific Yield (SSY) of Inverter

IV. Characteristic of Solar Module 5.2.1.1 Capacity utilization factor (CUF)

CUF is the ratio between the actual energy production of the solar power plant to the potential output at Standard Test Conditions (STC)*. It is expressed as a percentage and usually measured over a year. CUF mainly influenced by the solar irradiation across the country and CUF may be considered different for different locations. The CUF does not consider on-site environmental and degradation factors, grid availability, etc., hence, a separate degradation factor is multiplied to get the expected CUF in that year.

CUF(%) =𝐸 (𝑘𝑊ℎ)

𝑃(𝑘𝑊𝑝) × 24ℎ𝑟𝑠 × 365 𝑑𝑎𝑦𝑠 × 100

Where,

CUF = Capacity Utilization Factor over a Year.

E = Plant energy production or Plant energy metered over a Year (kWh)

P = Plant Peak Installed Capacity (kWp)

In India, mostly used KPI for PV plant performance is CUF



* Standard Test Conditions (STC) are the standard for the conditions under which a solar panel are tested. By using a fixed set of conditions, all solar panels can be more accurately compared and rated against each other. There are three standard test conditions, which are: 1. Temperature of the cell – 25°C. The temperature of the solar cell itself, not the temperature of the surrounding. 2. Solar Irradiance – 1000 Watts per square meter. This refers to the amount of light energy falling on a given area at a given time. 3. Air Spectrum – 1.5.

This number is somewhat misleading as it refers to the amount of light that has to pass through Earth’s atmosphere before it can hit Earth’s surface, and has to do mostly with the angle of the sun relative to a reference point on the earth. This number is minimized when the sun is directly above as the light has to travel a minimum distance straight down (as in case of X), and increases as the sun goes farther from the reference point (as in case of Y) and has to go at an angle to hit the same spot. When the Sun is at its zenith, the optical air mass is unity and the spectrum is called the air mass 1 (AM1) spectrum. When the Sun is at an angle with the zenith, the air mass is given by

𝐴𝑀 =1

cos 𝜃 ; Where θ = Sun angle with Zenith

Figure 38: Air Spectrum 5.2.1.2 Performance ratio (PR)

The Performance Ratio is a measure of the quality of a solar PV plant performance during its operation. The idea is to track actual performance and compare with the theoretical performance calculated during the design phase.

𝑃𝑅 =𝐴𝑐𝑡𝑢𝑎𝑙 𝑃𝑙𝑎𝑛𝑡 𝑜𝑢𝑡𝑝𝑢𝑡 (𝑘𝑊ℎ)

𝑁𝑜𝑚𝑖𝑛𝑎𝑙 𝑃𝑙𝑎𝑛𝑡 𝑜𝑢𝑡𝑝𝑢𝑡 (𝑘𝑊ℎ)



The Nominal plant output is calculated by;

𝑁𝑜𝑚𝑖𝑛𝑎𝑙 𝑃𝑙𝑎𝑛𝑡 𝑜𝑢𝑡𝑝𝑢𝑡

= 𝑆𝑜𝑙𝑎𝑟 𝑖𝑟𝑟𝑎𝑑𝑖𝑎𝑡𝑖𝑜𝑛 (𝑘𝑊ℎ

𝑠𝑞. 𝑚) × 𝑠𝑜𝑙𝑎𝑟 𝑚𝑜𝑑𝑢𝑙𝑒 𝑎𝑟𝑒𝑎 (𝑠𝑞. 𝑚)

× 𝑚𝑜𝑑𝑢𝑙𝑒 𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑦 (%)

5.2.1.3 Solar specific yield (SSY) of inverter

To improve the performance of every solar inverter, it is essential to quantify & monitor the productivity in terms of Solar Specific Yield.

𝑆𝑆𝑌 = 𝐺𝑒𝑛𝑒𝑟𝑎𝑡𝑖𝑜𝑛 (𝑘𝑊ℎ)

𝐶𝑎𝑝𝑎𝑐𝑖𝑡𝑦 (𝑘𝑊𝑝)

Specific Yield refers to how much energy (KWh) will be produced for every KWp of

installed capacity over a period. A good plant/ solar inverter may have SSY ≥ 5 i.e. 05 units per kWp capacity per day.

This may differ from location to location based on solar irradiation level all over India.

5.2.1.4 Current-voltage (IV) characteristic of PV module

The I-V curve provides a quick and effective means of accessing the true performance of solar PV modules or strings. In a correctly performing PV system the shape of the curve should follow the normal profile and the measured values of Isc, Impp, Voc, Vmpp and Pmax should be as expected for the environmental conditions at the time of measurement. I-V curve tracing can be carried out to create an operational I-V curve to confirm that the actual power output is close to the predicted value of the new system. If there is a discrepancy, analysis of the I-V curve shape can be used to help identify the root cause for the under-performance and remedial measures can be implemented. IV curve is very sensitive to environmental conditions such as solar Irradiation, temperature for more details see para factor affecting power generation above.

Figure 39: Current Voltage (IV) Curve of a Solar Cell.



Some of example of change in IV curve due to change in external & internal parameters of solar module

Fig: a) IV-curve due to shading or damaged cell

effect Fig: b) IV-curve due to increase of series

resister

Fig: c) IV-curve due to degradation or soiling effect

Figure 40: Change in IV Curve Due to Change in External & internal Parameters



CHAPTER 6

MODEL POWER PURCHASE AGREEMENT (MPPA) REMCL is a joint venture of Ministry of railways and RITES for planning, tendering / bid processing and implementation of renewable energy (Solar and Wind) projects on behalf of Indian Railways.

REMCL issued a model PPA on behalf of Railways for guidance and implementation of Renewable projects. Some of the important extracts from PPA for information is given below.

Disclaimer: This chapter contains important extracts from model PPA issued by REMCL and may differ in actual signed PPA document.

6.1 IMPORTANT PROVISIONS OF PPA

Railway Grants Permission to SPD

Railways grants, obliges and entitles the Solar Power Developer (SPD)

(a) Right of Way, access and permission to construct and operate the solar rooftop project at the identified Site for the purpose of Agreement.

(b) Finance and construct, Operate, manage and maintain the project.

(c) Demand an appropriate Tariff from Railways for supplying electricity.

(d) Perform and fulfil all of the SPD’s responsibilities

(e) Bear and pay all costs, expenses and charges in connection with or incidental to the performance of the obligations of the SPD under this Agreement.

(f) Neither assign, transfer or sublet or create any lien or Encumbrance on this agreement, or on the whole or any part of the Project nor transfer, lease or part possession thereof, save and except as expressly permitted by this Agreement.

Addition Facility to be Provided by SPD

The SPD shall, at its own cost and expense, in addition to and not in derogation of its obligations elsewhere set out in PPA

(i) Make its own arrangement for, take reasonable measures, and shall be solely responsible for security of the Facility Installations, including commercially reasonable monitoring of the Site’s alarms, if any.

(ii) Procure that all facilities and amenities within the solar rooftop power system are operated and maintained in accordance with good industry practice.

(iii) Railways will only issues directions to shut down the plant in case of the occurrence of a state of Emergency (a state of emergency may be defined as a situation where the safe working of the internal grid of the Railways/ grid sanctity of the distribution grid is or is likely to be compromised due to conditions beyond the control of the Railways).

(iv) Undertake regular operation and maintenance of the Facility and the Interconnection Facilities as per the specifications and requirements laid down by the Central Electricity Authority and respective SERCs.



(v) Facilitate the execution of the Net Metering agreement of Railways with the utility.

(vi) Railways to provide water to the SPD for the cleaning of the solar modules and other O&M functions. In case of water scarcity, the SPD has to be informed in advance of the same and will have to arrange water, as per its requirements. The Raw Water connection point may be provided by Railways at site as available, SPD obtains water by providing and laying pipes etc. from nearest water connection point made available. The Railways will have the right to charge the SPD reasonable charges for the water connection and the supply of water which may be provided to the SPD.

Capacity Utilization Factor (CUF) Guarantee

In India, the grid operator requires the asset Owner to meet the Capacity Utilization Factor (CUF) delivery guarantee, as agreed in the PPA, and considering the annual de-gradation factor. If the CUF guarantee is not met, the Asset Owner has to pay penalties to the grid operator. CUF guarantee is essential for the grid operator to plan their energy requirements, and plan the finances accordingly. This is the reason why in India, including CUF guarantees in the O&M contract between the Asset Owner and the O&M Contractor has seen an increasing trend with contracted CUF being between 17-24% and a decreasing trend in annual CUF degradation of between 0.75%-1.2% currently.

The Minimum CUF which the solar power provider will have to provide during first year of operations will not be the lower than 16% or the Normative CUF provided by the State Tariff Order whichever is higher.

Shortfall in Generation

If for any contract year, it is found that the SPD has not been able to generate minimum energy as outlined in the Minimum CUF, on account of reasons solely attributed to the SPD, such shortfall in performance shall make SPD liable to pay a compensation equivalent to the higher of the following:

(i) Shortfall in generation vis a vis Minimum CUF multiplied by Tariff agreed in this agreement.

(ii) The penalty accruing to Railways for not being able to meet its Renewable Purchase Obligation/cost incurred for buying the shortfall in RE through RECs and the cost incurred by Railways for procuring an equivalent amount of energy from the distribution utility.

6.1.4.1 Causes of shortfall in generation

(i) Railways repairs the Premises’ roof for any reason directly related to damage, if any, caused by the System/ SPD, and such repair requires the partial or complete temporary disassembly or movement of the System.

(ii) Any act or omission of SPD or its employees, Affiliates, agents or subcontractors results in a disruption or outage in System production, and such events not attributable to Railways.

Then in either case (i), (ii) above, SPD will

(i) Pay the Railways for all work required by Railways repair of roof.

(ii) Not be eligible for deemed generation and



(iii) This period will be not be counted during accounting for calculation of CUF and evaluation of whether the system met the Normative CUF.

6.1.4.2 Calculation of quantum of deemed generation

(i) During Deemed Commissioning Period, Minimum CUF shall be applied to the nominal installed capacity of the Unit under Deemed Commissioning.

(ii) For the period after Commissioning, such period during which Railways failed to off take

Electricity shall be divided into blocks of 15 minutes each and paid in blocks of 15 minutes. No deemed generation will be available for the first 15 minute block. The Electricity generated by the SPD during the same period of each 15 minutes block on the same date of the preceding year shall be taken as Deemed Generation, provided that if such situation occurs before expiry of one year after the Commercial Operation Date, Deemed Generation shall be based on the generation of Electricity in the same block of each 15 minutes on the immediately preceding day when there was no failure to off take on the part of Railways. If in the first year of the operation, Deemed Generation shall be based on the generation of Electricity in the same block of each 15 minutes for last 15 days for which the energy generation were monitored.

Generation Factor

The Normative CUF, which the solar power developer will have to provide during first year of operations shall not be the less than [16%] of Installed capacity or the Normative CUF provided by the State Electricity Regulatory Commission of Installed Capacity whichever is higher. The maximum degradation in generation allowed over the first ten years of operation is 10%, over life of the project is 20% of the Installed Capacity.



REFERENCES

1. Best Practice Guidelines for Solar Photovoltaic Power Plants (India edition) by Solar Power Europe.

2. A Project Developer’s Guide on “Utility-Scale Solar Photovoltaic Power Plants” by International Finance Corporation.

3. Solar Energy Fundamentals, Technology and Systems by Delft University of Technology.

4. Technical Data by Manufacture of Solar Module.

5. Report on Green Railways by Indian Railways.

6. Report on Assessment of Solar Plant by UNDP (United Nations Development Programme).

7. Model PPA Issued by REMCL.

8. Booklet on Maintenance Management of Solar Installations by Al Akhawayn University.

9. Data Collected from Website of Indian Railways Green Energy Initiatives (http://www.irgreenri.gov.in).

https://www.undp.org/

http://www.irgreenri.gov.in/



CONTACT US

CAMTECH is continuing its efforts in the documentation and up-gradation of information

on maintenance practices of electrical assets. Over the years a large number of

publications on electrical assets have been prepared in the form of handbooks, pockets

books, pamphlets and video films, etc. These publications have been uploaded on the

internet as well as rail net.

For downloading these publications please do following: 1. On internet visit: www.rdso.indianrailways.gov.in

Go to Directorates CAMTECH Other important links Publications for download Electrical Engineering

2. On Railnet visit RDSO website at 10.100.2.19 Go to Directorates CAMTECH Publications for download Electrical Engineering

For any further information regarding publications please contact:

Dy. Director (Elect.) BSNL : 0751- 2470740 (O)

Rly. : 03747202

SSE/Electrical : 8957022145 (CUG)

E-mail : [email protected]

Fax : 0751- 2470841

Write at : Dy. Director (Electrical)

Indian Railways, Centre for Advanced Maintenance Technology In front of Hotel Adityaz, Airport Road, Maharajpura, Gwalior, Pin code – 474 005

http://www.rdso.indianrailways.gov.in/



Government of India - Ministry of Railways

INDIAN RAILWAYS

CENTRE FOR ADVANCED MAINTENANCE TECHNOLOGY Maharajpura, Gwalior, M.P. 474 005

BOOKLET ON - rdso.indianrailways.gov.in

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Transcript of BOOKLET ON - rdso.indianrailways.gov.in