spv planning guidelines

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POWER PLANTISSUE I : APR 2004

______________________________________________________________________

PLANNING & MAINTENANCEGUIDELINES FOR SPV

(SOLAR PHOTOVOLTAIC) POWERSUPPLY

GENERIC REQUIREMENTS

GR No. GL/SPV-05/01 APR 2004

(AFFIRMED- NOV 2007)

TECTELECOMMUNICATION ENGINEERING CENTRE

KHURSHIDLAL BHAWAN, JANPATH,NEW DELHI-110001

(INDIA)

---------------------------------------------------------------------------------------------------------------------

All rights reserved and no part of this publication may be reproduced,stored in any retrieval system, or transmitted, in any form or by any means,electronic, mechanical, photocopying, recording, scanning or otherwisewithout written permission from the Telecommunication EngineeringCentre, New Delhi.

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HISTORY SHEET

S.No. Name of the Generic

Requirements

No. of the Generic Requirements Remarks

1. Planning & MaintenanceGuidelines for SPV(Solar Photovoltaic ) PowerSupply

GL/SPV- 05/01 APR 2004 First issue

2. Planning & MaintenanceGuidelines for SPV(Solar Photovoltaic ) PowerSupply

GL/SPV- 05/01 APR 2004(AFFIRMED - NOV 2007 )

First issue

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CONTENTS :

Clause No. Requirements Page No.

PART 1 : Technical Requirements

1.0 Scope 1

1.1 Introduction 1

1.2 Brief Description of SPV Technology 1

1.3 SPV Power and its Application 5

1.4 SPV Power Supply 6

PART 2 : General Requirements ( Planning of SPV Systems)

2.0 Planning of SPV Power Supply 7

2.1 Planning for Stand Alone and Hybrid SPV Power Supply 72.2 Installation and Maintenance Practice 22

2.3 Maintenance Schedule & Guidelines 25

Annexure -I List of Recommended Tools and Test Instruments 27

Annexure- 2 Terminology (Terms used) 28

Annexure- 3 Abbreviations 29

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PART 1

TECHNICAL REQUIREMENTS

GL No. GL/SPV - 05/01 APR 2004

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PLG & MTC. GUIDELINES FOR SPV POWER SUPPLY GL/SPV-05/01 APR 2004

1.0 Scope :

This document covers the basic theory and concept of Solar Photo-Voltaic (SPV)Power technology. It also covers the necessary guidelines for planning of theSPV Power Systems for a given telecom equipment. These guidelines havedetailed the facts which shall be taken into consideration while selecting a SPVPower Systems for a given requirements. It has also given the guidelines forcalculating load for a given system. Sample calculation for deciding the load SPVPower and Batteries have also been incorporated in this document to elaboratethe guidelines for the user.

1.1 Introduction :

The last decade has seen the evolution in the field of telecom services. The latest

technologies have enabled to reach the telephone services to the remotest areas.

The most severe constraint to provide the services in these areas is the non-

availability or extremely poor reliability of Commercial AC mains required for

powering of the individual customer premises equipment. In such a scenario SPVpower supply offers a reliable solution.

Photovoltaic is referred to generation of voltage from light. Photovoltaic cells are

also called solar cells. These cells can work in the light irrespective of source.

Photovoltaic cell converts light energy in to electric energy.

Though the Photovoltaic cells can produce electric energy in the presence of light

but can not store it. As soon as the source of light is removed, they stop

generating electric energy. It is a known fact that full sunlight is available for a

very short duration in the day. It is therefore essential that there shall be some

device which can store the energy produced by SPV cells which can be utilisedwhenever required. The Lead acid storage batteries are mainly used for this

purpose. These batteries convert the electric energy generated by the SPV cells

into chemical energy and deliver back for the use by converting the chemical

energy back to electric energy when the load is connected across it.

1.2 Brief Description of SPV Technology :

1.2.1 Principle :

All the elements are made of atoms. Atoms in turn are made of positively

charged protons & neutral neutrons in the nucleus and negatively charge

electrons arranged in the shells or orbits around the nucleus. Except for noble

metals the outermost orbit is not full. Due to this reason the atoms tend to combine

with other atoms to attain stability.

Silicon is the most commonly used element for SPV application. The outer most

shell of a silicon atom has four electrons. These atoms share their electrons, in the

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outermost shell with the neighbouring atoms to achieve stability. Such highly

ordered structure is called crystal lattice. When all the atoms are silicon atoms, it is

called intrinsic lattice.

Light acts as a flux of discrete particles called photons. Photons carry momentum

but does not have any charge. When the light falls on the semiconductor siliconlattice, photons penetrate deep into it. Photons have enough energy to dislodge

electrons from the bond, when they colloid with them. Electron so released

becomes free to wander throughput the semiconductor as a conduction electron

and possesses a negatively charged usable energy. Thus the light energy is

converted into electric energy. Whenever an electron is knocked out from the

bond it leaves behind a bond with one electron less or missing. This incomplete

bond is called a hole. Electrons freed by knockout wander at random till they

come across a hole to fill. This way hole moves in the material.

In the absence of the external electric field the electrons freed and energised by

photons wander for some time and recombine with the wandering hole and thusenergy originally transferred to electron is lost in the semiconductor lattice itself as

heat. To produce the usable energy output shall sweep the free electrons out of

the material before they recombine with the free holes.

One way to achieve this is to add a small amount of some other element such as

boron or phosphorus etc., which create excess holes and electrons in the intrinsic

semiconductors. Such additive materials which alter the properties of the

semiconductor significantly are called dopants and the process placing them into

the semiconductors is called doping.

Boron has one electron less than silicon in its outer most shell & by combiningwith the neighbouring silicon atoms leaves one bond incomplete thus creating a

hole. As this Boron doped silicon containing holes has positive charge and is

called P-type silicon.

On the other hand phosphorous atom has one more electron in the outer most

shell than a silicon atoms and its combining with neighbouring silicon atoms

leaves one extra electron in the lattice. This phosphorus doped silicon has

negative charge and is called N-type silicon.

The quantity of these dopants is extremely small usually around one boron or

phosphorus atom for every 10,000,000 silicon atom.

P-type and N-type regions are created adjacent to each other. In this case some

free electrons in N-type region cross over to P-type region and fall into holes and

remain there permanently. This process of crossing over continues till every boron

site with hoes become negatively charged. On the other hand every phosphorus

site giving up electrons becomes positively charged. This way two equal but

opposite charged regions are created on each side of the p-type/n-type interface

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and thus create an electric field. In this region, the field is so oriented that it

pushes the electrons in the direction of n-type regions and holes in the direction of

P-type region. As any free moving charge entering the region entering zone of

influence is immediately swept out of this zone, this zone is called depletion zone

is named p-n junction.

The strength of this internal electric filed is quite strong. The thickness of this

depletion zone is about one micron and filed potential is about one volt. This

strong filed is just an electric broom which can sweep all the free electrons out of

the cell in one direction and cause an electric current.

When a light penetrates into the semiconductor the photons knockout the free

electrons give them a potential energy. The free moving electrons entering the

electric field of the p-n-junction are pushed across it and are forced out of the cell

to do a useful work.

In a SPV module a large number of such cells are connected in series. Theelectrons flow from one cell to next through a conductor. In the next cell they are

further struck by photons and acquire more potential energy and sweep out of the

cell and so on. Finally the electron leave the last cell of the module and flow

through the load.

For every electron that leaves the cell, there is another returning cell though load

to replace it. The wires/cables used for interconnection of module to battery,

Battery to load and load to module contains electrons. As soon as the electrons

leave the last cell of the module and enter the wire/cable, an electron at the other

end of the wire/cable enter the first cell of the module. Thus the SPV device can

not rundown. This way a SPV cell produces electric energy in response of lightenergy. SPV cell cannot store energy, it can only convert the light energy into

electric energy.

1.2.2 How the current flows in a module :

The current generated by one cell does not simply flow through all the cell

connected in series and ultimately to the load. The electrons liberated in one cell

flow through the internal junction and to the next cell where they fall into the holes

of the cell. Photons again knock them out and make flow the next and so on. It is

therefore essential that all the cells in the module are properly illuminated. To

achieve this, the mounting of modules shall be such that the shading of its cells isprevented. Each cell give rise to a potential difference of volt. Therefore

the number of cells in series in a module will depend on the voltage desired

for the particular application.

1.2.3 Current SPV ( Solar Photo-Voltaic ) Cell Technologies :

A. Silicon Cell Technologies : Silicon Cell technologies mainly are :

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a) Mono-crystalline (Czochralski or CZ) : The mono-crystalline cells or CZ

cells are the most commonly used cells in the world. In CZ technology the

purified chunks of silicon are melt in a crystal growing furnace and than

slowly solidified into a large cylindrical crystal. In this process the atoms of

silicon are so aligned that its electrical properties are optimised. Individualround wafers are sawed out from this cylindrical crystal. Silicon- cell

efficiency is in the range 14 to 15% & Module/Array efficiency is about 12 to

13 %.

b) Cast Polycrystalline Silicon Cell technology : In this technique the purified

silicon chunks are molten in a rectangular mould and than cooled slowly. In

this process the atoms are not aligned into a large single crystal as in case of

CZ technique. In this method small regions of single crystals crystallise to

each other creating poly-crystalline blocks of different grains and orientations.

In this method dangling (incomplete) atomic bonds are also created which

interfere with the flow of the current. Due to this reason the efficiency of thesecells is a bit lower than mono-crystalline cells. Cell efficiency of these cells is

about 10-12%, module efficiency is module/array efficiency is about 8 to 10%.

c) Ribbon Silicon technology : In the above two technologies, the Silicon

crystal ingots are sliced in to thin wafers of thick ness enough to make a cell

of thickness of about 0.4mm. Thinnest saw blades available are also of the

same thickness. Hence about half of the crystal ingots are wasted.

In the ribbon techniques the a ribbon is pulled sideways off the top of the

molten silicon or pulled through the die to get the ribbon silicon. The ribbons

are then broken to get rectangular wafers.

Though this technique may provide a cost effective solution but the surface of

the ribbon is uneven, which makes interconnection process very difficult.

d) Amorphous silicon cells : This technology has a large number of problems

due to which this technique is not still popular. Main drawbacks of the

technique are very low efficiency and fast degradation of the cells. This leads

to large size of the modules and life of these cells is much lower as compared

to other silicon cell technologies, hence makes unviable.

e) Thin Film Technologies : In these techniques the SPV Modules instead ofcells is made by depositing an extremely thin film of semiconductor on the

glass or metal substrate. The semiconductor layer in this technology is only a

few hundred atoms thick and entire module is formed as a unit. This

technology is still in the development stage and may provide an ideal future

prospect.

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B. Concentrator cell technology : This technique is very useful for large

power generating systems. In this technique the sun light is concentrated on

the cells which is 500 to 1000 time stronger than the direct sun light on the cell

surface. Through this techniques great saving of panel space is achieved.

This also is still at the laboratory stage.

C. Comparison of various technologies :

Technology Module

efficiency

Plus points Minus points

Mono-crystalline

Silicon cell

13-15% Oldest & well

understood.

Big panel size (approximately

one meter square per 100 watt)

Poly crystalline

Silicon cells

10-12% Low efficiency Panel size bigger than mono-

crystalline. & not popular in India

Ribbon silicon

Cells

10-12.5% Low cost & small

size

Lot of work still to be done.

Amorphous silicon

cells

7 8% Low cost Low efficiency and low life.

Thin film cells 3-10% Low cost,

high deposition

rate possible

Lot of development is required.

Concentrator

cells

N.A Good for central

power generation

Complex system & still not

economical.

From the above table it is clear that presently only mono-crystalline and poly-

crystalline silicon cell technologies are suitable for Telecom applications.

Mono-crystalline technology has an other added advantage, it has widest

spectral response from 350nm to 1100nm with its peak at 800nm. All the

other technologies have either a very narrow spectral response or have

higher response in the Infra Red band, which is not desirable. It is mentioned

here that as the wavelength increases, the energy possessed by the light

decreases. A standard spectrum has been defined as a spectrum from the

Sun that filters through 1.5 times the thickness of the atmosphere and is

referred as Air Mass 1.5. This is being taken as a standard reference for

specifying the output of an SPV device.

1.3 SPV Power and its Application :

SPV power provides the ideal solution for powering the Telecom equipment for

the following reasons :

- Does not require any fuel other than sunlight, which is available free in

abundance all over India ( 3.5 to 5 hours full sun per day).

- Non polluting, so no environmental issues.

- Minimum maintenance : SPV panels are self draining and self cleaning. There

are no moving parts, as such, no wear & tear and no routine maintenance.

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- Maximum reliability as there are no long transmission wires, no oil etc. makes

it very reliable system.

- Easily expandable, SPV panels can be added whenever required to enhance

its capacity.

1.4 SPV Power Supply :

1.4.1 SPV Power Supply Classification : From the application point of view, the

SPV Systems may broadly be classified as :

a) Stand alone SPV Power Supply

b) Hybrid SPV Power Supply

1.4.1.1 Stand Alone SPV Power Supply : Stand alone SPV systems are power

supplies purely based on SPV Power source (SPV panels) and battery. These

type of systems are useful where there is no commercial mains at all or the

access to commercial mains is not feasible & the load is not very high.

1.4.1.2 Hybrid Power supply : The SPV Power supply is easily manageable for day

loads up to 30 KWH. At places where AC commercial mains are available but are

erratic and available for a very short duration, a hybrid power supply using a

combination of AC commercial mains & SPV power source may be useful. As

SPV power requires a very high initial cost, such combination can be effectively

used to make a cost effective power supply while at the same time maintaining

the same level of reliability of the power supply. In Hybrid SPV Power supply the

charge controller is provided with a Float Charger (FC) which works on AC

commercial mains. All the protections and regulation requirements of the FC are

provided in the charge controller.

END OF PART - 1

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PART 2

GENERAL REQUIREMENTS

(PLANNING OF SPV SYSTEMS)

GL No. GL/SPV- 05/01 APR 2004

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2.0 Planning of SPV Power Systems :

2.1 Stand Alone and Hybrid Power supply : Planning of the SPV powersystems will be the most efficient if the following constituents of the SPV

power supply are planned properly for Stand Alone SPV Power Supply and Hybrid

Power supply :

a) Battery bank.

b) SPV Power Source

c) Charge Controller

d) Float Charger (in case of Hybrid Power supply)

e) Mounting Structure

f) Cables

g) Earthing

2.1.1 Planning for Stand Alone SPV Power Supply :

2.1.1.1 Battery Bank : The battery is an important constituent of the SPV Power Supply.

The battery stores all the energy generated by the SPV power source and delivers

to the load during the periods when the SPV power source is unable to supply

power to the load due to any reason.

2.1.1.1.1 Important factors for deciding the battery capacity : The following important

factors shall be considered while designing the battery for SPV application :

a) The capacity of the battery will depend on the daily load & days of autonomy.

b) The battery shall be capable of performing efficiently at slow rate of charge

(C/20 i.e. 0.05 X C) and slow rate of discharge (C/120 i.e. 0.0083 X C).

c) These batteries are exposed to hostile environmental conditions such as saline

atmosphere of the coastal areas and high altitudes. While selecting the battery

for SPV application, it shall be ensured that the battery is capable of workingin these environmental conditions without any degradation in performance.

d) These batteries are more exposed to high/low temperature. The necessary

corrective factor for the above fact may be taken into account while

calculating expected life, available capacity and permissible DOD(depth of

discharge). The following corrective factors may be used for the above

parameters :

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1. Every 10 degree rise in the average ambient temperature above 35 degree

Celsius reduces the life of the battery by half For example if the battery is

to work at an ambient temperature of 45 degree Celsius the expected life

of the battery may be taken as 700 DOD cycles up to 80% DOD instead of

1400 (specified for the battery designed at 35 degree Celsius up to 80%DOD).

2. The capacity of the battery increases or decreases @ 0.43% for every one

degree Celsius increase or decrease in temperature. This factor becomes

significant when the ambient temperature is Zero degree or lower as it will

reduce the capacity of the battery by more than 10%.

3. At sub-zero temperature the chemical reactions in the battery gets slower.

It is therefore not advisable to discharge the battery beyond 50% of its rated

capacity at these temperatures.

2.1.1.1.2 Basic considerations for calculating Battery capacity :

1. Battery shall be selected to cater the ultimate load(5 years projection included)

2. The Permissible DOD : i) Normally : Not beyond 80% of its rated capacity

ii) For sites where temperature goes : not beyond 50%below Zero degree Celsius

3. VRLA batteries shall deliver higher at slow rate of discharge :

- 120% of rated C/10 capacity in case of 1 and 2 days autonomy

- 130% of rated C/10 capacity in case of 3 days autonomy

- 150% of rated C/10 capacity in case of autonomy for 4 days and above

4. Average battery voltage during discharge is 1.9V/cell.

5. At places where the battery is to work around Zero Degree Celsius batterycapacity shall be increased @ 0.43% per degree Cesius below 27 degreeCelsius.

2.1.1.1.3 Battery capacity calculation :

The battery capacity may be calculated using the formula :

(Load per day) X (Autonomy in days)---------------------------------------------------------------------------------------------- .... (1)

(permissible DOD)X(battery capacity expected) X(*Temperature factor)

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Where :

- Load per day shall be ultimate load for calculating battery capacity

- Permissible DOD for Working temperature below Zero Degree Celsius

shall be taken as 50% in all other cases it shall be taken as 80%.

- Expected capacity for days of autonomy : :

1 & 2 days : 120% of the rated C/10 capacity

3 days : 130% of the rated C/10 capacity

4 days & above : 150% of the rated C/10 capacity.

*Temperature factor shall be considered only in case the battery is to

work at temperatures Zero or lower & calculated by the formula :

1 + (T-27)X 0.0043 Where T is the battery working temperature.

2.1.1.1.4 Sample calculations :

A. Load :As calculated in clause 2.1.1.1.4.1

B. Autonomy : say 3 days

C. Minimum Site Temperature : say 13 Degree C

D. Permissible DOD : 80%

E. Effective rate of discharge : (24 X3)/0.8 = C/90

F. Effective battery capacity at discharge rate C/90 : 130%

2.1.1.1.4.1 Load Calculations :

a) Equipment load (C-DOT RAX working on 48V) :

Present Ultimate

Say Continuous load : 2A 2A

Off Hook Current : 30mA (30 subs) 30mA(480 subs)

Anticipated traffic : 0.1 Erlang 0.1 Erlang

Load/day : Continuous 2*24 = 48AH 2*24 = 48AH

Off-hook (0.030*30/10)*24 (0.030*480/10)*24

= 2.16 Ah = 34.6 Ah

Total Equipment Load : 50.16AH 82.6Ah

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b) Lighting Load :

Number of lights : 4 6

Wattage of each light : 20W each 4 of 20W 2 of 15W

Duration of use : average 4 hour each average 4 hour each

Total load WH : 4X20X4 = 320WH (4X20+2X15)X4 = 440WH

AH : 320/(1.9 X 24)= 7AH 440/(1.9X24) = 9.7AH

c) Inverter Load (if used) :

Rating of the inverter : 48V/200VA

Conversion Efficiency : 90%

Inverter input PF : 0.9 absolute

No load current : 10%

Inverter use per day : 6 hoursInverter load WH : ((200/(0.9X0.9))X6)+(200X0.1X18) =1841WH

AH : 38.4AH

d) Any Other load such soldering bolts headlights etc. not covered above

Say : 200WH or 4.5AH

Total Load per day (ultimate) 82.6 + 9.7+38.4 + 4.54 = 135.54AH

say :136AH

2.1.1.1.4.2 Battery Capacity calculation :

Using the inputs from A to F above and putting them in the formula (1) of clause2.1.1.1.3 the battery capacity for the load as calculated in A shall be :

(136 X 3)/(0.8 X 1.3) = 392AH

On the basis availability Battery AH capacity 2 X 200AH may be selected.

2.1.1.2 SPV Power Source :

SPV Power Source (generator) is the most important part of the SPV Power supply.SPV power generator size & rating will depend on the load to be fed by it. Usablebasic building block of a SPV power source is a SPV power generator module.These modules, as per TEC GRs, are available in 12V/12W, 12V/50W and12V/75W ratings. These modules are connected in series to get the desire voltage.The arrangement is called a panel. These panels are connected in parallel to form

an array to get the desired power. SPV power engineering involves theestimation of load and designing of SPV power system sufficient to cater the loadin the most economical and efficient way. It may be done as follows :

2.1.1.2.1 Load and its Estimation :

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Load consists of equipment load, the lighting requirements & the load of

accessories which are essential for attending the telecom equipment.

a) Telecom Equipment : The equipment load now a day does not vary much,

the difference between the peak load & slack load is not more than 10 to

20%. Accumulative load over the 24 hours shall be taken as the daily loadfor calculating SPV Power Source. The best way to calculate the load is

to get the accumulative load for the day. If it is not feasible then take

the product of the optimum load multiplied by 24 as the equipment

load per day. Five years projection shall be considered for future load.

b) Lighting and other essential accessories requirements : As the SPV

power is very expansive and occupies a huge space, it is therefore essential

that all the electric appliances shall have the optimum efficiency. All the

lighting gadgets shall have a very low wattage for the required intensity of

light. Inverters if used shall have the best conversion efficiency, low

harmonics, very low inrush current and very good power factor. Forcalculating the lighting load, the number of lightings, their wattage & duration

for which these lightings shall be taken into account. For example, if in the

equipment room there are 6 bay lights which will only be used for attending

the faults, or taking routine tests etc. @ rate of 1 hour per light per day and

the wattage of these lightings is 12W DC, working at 12V. The load for

lighting is 6 X 12 = 72W. In case of other accessories such as soldering iron

head lights etc. the load per day shall be calculated in the same way.

c)Inverter load if used : In case the inverter is used for lighting, accessories

and some specific functions, the rating of the inverter shall be divided by the

efficiency and its true PF to get the load offered by the inverter.

d) Any other load not covered above.

The Load shall be sum of all the above loads.

Note : 5 years projection shall be taken into consideration for designing the

SPV system.

2.1.1.2.2 Designing of SPV Power Source :

The power delivered by an SPV power source will depend on its rating and someof the natural/environmental factors. Knowing the rating of the SPV system (power

source) only vis-a-vis load does not guarantee the deliverance full power of the

load. Some of the features of SPV technology & environmental factors which

drastically affect the performance of the power source are :

- IV Curve

- Voltage of the SPV power source

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- Irradiance or Light intensity

- Temperature of the cells

- Response of the light spectrum

- Orientation of the panel/array

- Full Sun hours or Insolation/day.

2.1.1.2.2.1 I-V Curve and Its Importance :

I-V Curve shows the relation between Current & Voltage. The suppliers of the SPV

power source shall provide the I-V Curve at standard condition of 1000W/m2 solar

intensity at 25 Degree Centigrade and A.M.(Air Mass (thickness of the

atmosphere)) of 1.5. By looking at the I-V Curve one can easily know about the

optimum power to be delivered by the SPV panel/array/source. In addition to the

power, I-V curve tells about the voltage and current at the peak power.

2.1.1.2.2.2 Voltage of the SPV power source :

The voltage of the SPV power source is an important factor that affects the battery

charging. The voltage of the SPV Cell/Module/Panel decreases with the rise of its

temperature, which increases or decreases @ 0.0024V/cell/degree Celsius. To

charge a battery fully the voltage of the power source shall be better than 2.5V/cell.

Considering this fact, the Voltage of the SPV panel at optimum power shall be such

that the voltage delivered by it at the battery terminals shall be about 2.25V/cell.

The SPV modules/panels are designed at temperature of 25 degree Celsius. The

SPV modules/panels are to deliver under the following conditions :

In plains of India, in summers the temperature of the SPV cells may be around

65 Celsius which will reduce the output of a 12V module/panel by 3 to 3.5V.

Voltage drop of the cable from panel to Charge controller may be about 2% of

the voltage at peak power (for 12V systems the voltage at peak power is 17V).

Another drop of 2V is expected due to blocking diodes and charge controller.

In the light of above facts the voltage of a SPV module/panel for 12V systems shall

be better than 17V (13.5+1+0.34+2). As one cell produces about 0.5V, it is

therefore essential that the SPV modules used in India shall have minimum

36 cell connected in series. For higher voltages these modules are

connected in series.

2.1.1.2.2.3 Irradiance or Light intensity :

This is one of the major factor which decides the power delivered by an SPV

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power source. The SPV modules or panels are designed at a standard irradiance

of 1000 watts per metre square at 25 Celsius and AM( air mass) 1.5, which is

called ONE SUN or peak irradiance . In actual field condition the same is not

always available. If the irradiance is lower or higher than the standard value,

current delivered by the SPV power source will decrease or increase but

there is no variation in the system voltage.

2.1.1.2.2.4 Temperature of the SPV cells :

With the increase in cell temperature the output voltage of the SPV cells

decreases @ 0.0024V/cell/degree Celsius. In Indian planes the cell temperature

in summer may be as high as 65 Celsius. Considering this fact it may be

ensured that all the SPV power source shall be formed by using SPV

modules(formed by 36 cells connected in series).

2.1.1.2.2.5 Response of the light spectrum :

The light spectrum is composed of the light waves of different frequencies. The

response of the SPV cell material/techniques is different for different light

frequencies. Mono-crystalline cells have the widest spectrum response

(350nm to 1100nm with peak at 800nm), in the current technologies being

used in low power telecom application. That is why the mono-crystalline

technology is extensively being used in the world.

2.1.1.2.2.6 Orientation of the Panels/array :

The maximum power will be achieved by a SPV power source, if it is oriented in

such a way that it always gets the optimum sun power. To achieve the maximumpower :

- The panel/array shall be oriented in such a way that it faces true South in

Northern hemisphere and true north in the Southern hemisphere & not the

magnetic south or north. The deviation of true north or south from magnetic

north or south is called magnetic declination, which can be known from

the magnetic declination map of the site. In case the local conditions and

wind velocity does allow the orientation as required, it may be done in

such a way that the optimum power is achieved while accommodating the

local constraints.

- The panel/array in the horizontal position does not deliver the optimum power.

To achieve the optimum power the SPV panels are tilted to the horizontal plane.

This tilt is different for different places. Normally an SPV power source may give

near optimum power at a tilt angle equal to the latitude of the place of

installation. In valleys of Kashmir and Leh it may be between 45 to 55 degree

depending on site.

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In case the magnetic declination maps & tilt information at the site is not easily

available, though not accurate but a simple method may be adopted as follows

:

Take a pyrometer and fix it on a board.

Finding the direction of true North/South : Place the pyrometer on the

horizontal plane, when the Sun is over head. Rotate it very slowly & read the

power. The maximum power gives the approximate direction of the true

north/south.

Finding the angle of tilt : Place the Pyrometer facing true north and lift it from

one side to find the tilt angle for optimum power. Continue lifting the pyrometer

till the optimum power is reached. This is the tilt angle of the site.

2.1.1.2.2.7 Full sun insolation hours or insolation/day :

Major part of India lies in the Zone where worst full Sun insolation is 4 to 4.5

hours per day. In a very small part of the country (areas around Rameshwaram &

a part of Andhra Pradesh) full sun insloation hours are more than 4.5 hours per

day. While in areas of Himalaya region it is less than 3 hours. While designing a

SPV System, always worst Sun Insolation of the place may be considered.

Sun insolation of the place may be available with weather office.

2.1.1.2.3 As the SPV Power source (generating system) occupy a huge space and also itsinitial cost is very high, it is therefore essential that the system shall be so designedthat :

- It occupies the minimum space- Full utilisation of the SPV power is achieved- Power of the SPV power supply is sufficient to take full care of the load and

battery.

2.1.1.2.3.1 The rating of the SPV Module shall be so chosen that the desired power isachieved with the minimum number of modules. The following factors shall beconsidered while designing a SPV power source at any site :

1) Availability of full Sun power at the site of installation. This may be procured from

weather office. In case it is not available the following criteria may be followed :

- In areas around Rameshwaram & part of Andhra Pradesh adjoining it, full

sun insloation hours shall be taken as 4.5 hours per day.

- In Himalaya region, for calculation purposes it shall be taken as 3.

- For rest of India it shall be taken as 4 hours/day.

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2) Load as Calculated in clause 2.1.1.1.4.1

3) Battery conversion efficiency : For VRLA batteries it shall be taken 90%.

4) Efficiency of the Charge Controller : It shall be taken as 85%.

5) The SPV power source supplies peak power at voltage 17V & above.

6) De-rating compensation for Temperature, ageing & other factors such as dust onthe top glass cover etc. shall be taken as 25%.

7) It shall be ensured that SPV power source is capable of charging the battery ata rate closer to C/20 rate of charge.

2.1.1.2.3.2 SPV Power supply Calculations : Considering all the factors, given in clause2.1.1.2.3.1 above, the SPV power supply rating shall be calculated using theformulas as given below :

a) Calculate SPV Power Supply as per load :

{ TPL 1.25 }For present load : { ----------------- X ------ } X 17 X NSM .. (2)

{ (BCE X CCE) 4 }

Where TPL - is total present load

BCE is battery conversion efficiency

CCE is charge controller efficiency

NSM is number of modules in series

{ TUL 1.25 }For Ultimate load : { ----------------- X ------ } X 17 X NSM .. (3)

{ (BCE X CCE) 4 }

Where TUL - is total ultimate load

BCE is battery conversion efficiency

CCE is charge controller efficiency

NSM is number of modules in series

b) Calculate SPV Power supply as battery charging requirements : Calculate

the rating of SPV power supply using the formulae as given below :

{ BBC X 0.05 }{ ----------------- X 1.25 } X 17 X NSM .. (4)

{ (BCE X CCE) }

Where : - The BBC(battery bank capacity) is the battery capacity as calculated

in clause 2.2.1.1.4.2

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- 0.05 is the battery charging current at C/20 rate of charge

- BCE is battery conversion efficiency

- CCE is charge controller efficiency

- NSM is number of modules in series

c) Compare the above two SPV power supply capacities.

- If the capacity calculated in (a) is higher than the capacity calculated in (b)the SPV Power supply capacity shall be (a)

- If the capacity (b) is higher than (a) the SPV Power supply capacity shall betaken as (b)

2.1.1.2.3.3 Sample Calculations :

Essential inputs required :Present Ultimate

Total Load (Equipment +Lighting :: Say : 104AH 139AH+Inverter if used + Any other load)

System Voltage :: Say : 48V 48V

Full Sun insolation for Site :: Say : 4 4

Battery Type & Capacity :: Say : VRLA 48V/400AH VRLA48V/400AH

Battery Conversion Efficiency :: Say : 90% 90%

Number of SPV panels in series :: Say : 4 4

Charge Controller Efficiency :: : 85% 85%

Autonomy : 3 days 3 days

The formula for calculation of rating of the SPV Generating System :

Calculate the SPV power supply capacity using formulae (2), (3) & (4) :

SPV Power Supply Rating :

Present (Using formula (2)) :

: {[{104/(0.9*.85)}*1.25]/4}*17*4 = 2890 Watts or 42.5A at 48V

Ultimate : Using formula (3) :

: {[{139/(0.9*.85)}*1.25]/4}*17*4 = 3861 Watts or 56.8A at 48V

As per Battery Capacity Using formula (4) :

: {[{(600 X 0.05)/(0.9*.85)}*1.25]}*17*4 = 3333 Watts or 49.0A at 48V

Where : 104Ah & 139 Ah are the load per day, 0.9 is battery conversion

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efficiency, 0.85 is the efficiency of the charge controller, 1.25 is de-ratingcompensation, 4 is full sun-insolation availability in India, 68(17(module voltage atpeak power)*4(number of parallels), 600 is the battery capacity as calculated inclause 2.2.1.4.2 & 0.05 is for C/20 rate of charging.

From the above the SPV power supply rating shall be :

- For present load : 3333 Watts(44 modules of 75 Watts or 68 modules of 50 Watts)

- For Ultimate Load 3861Watts( 52 modules of 75Watts or 80 modules of 50Watts)(8 modules of 75W or 12modules of 50W can be added as and when required at alater date).

2.1.1.3 Charge Controller : From the application point of view, the SPV Power supply

charge controller may broadly be classified as :

a) Stand alone SPV Power Supply Charge Controller

b) Hybrid SPV Power Supply Charge Controller

Stand Alone SPV Power Supply Charge Controller: Stand Alone SPV Power

Supply charge controller provides for the terminations for SPV Power, Load &

battery. It also provides for all the necessary protections against the damage to

load, battery & SPV power source. It also provides for the protection arrangement

against the lightning and surges.

Hybrid SPV Power Supply Charge Controller : The Hybrid SPV power supply

charge controller or composite Charge controller also provides for a Float

Charger(FC) which works on AC commercial mains. All the protections and

regulation requirements of the FC are also provided in the charge controller.

Charge Controller shall always be for the ultimate capacity. The Charge Controlleravailable in ratings as given below :

S. No. Name of System GR No. Rating of Charge Controller

1. SPV Power Supply for

Fixed Wireless Terminals

and Similar Systems

GR/SPV-

02/02 MAR

2004 or its

latest issue, if

any.

12V/12W & 12V/24W

2. SPV Power Supply for

Telecom Equipments

GR/SPV-03/02

JUN 2005 or

its latest issue,

if any.

i) SPV Power supply Requirement :Hybrid (With SMPS) or Standalone

(without SMPS)

ii) SPV Power supply Voltage rating :12V/48V.

S. No. Name of System GR No. Rating of Charge Controller

iii) Charge controller rating :a) 12V/500W Charge controller

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b) 12V/1000W Charge controllerc) 48V/5KW Charge controllerd) 48V/10KW Charge controller

iv) SMPS Rating :Capacity : 12V/37.5A or 12V/62.5A

or 48V/75A or 48V/150AFR/FC Module Rating : 12V/12.5Aor 48V/12.5A or 48V/25A

2.1.1.4 Mounting Structure :

Hot dip galvanized iron mounting structures complying the GRs GR/SPV-02/02MAR 2004 or its latest issue, if any or GR/SPV -03/02 JUN 2005 or its latest issue,if any may be used for mounting the modules/ panels/arrays. These mountingstructures are used to mount the SPV modules/panels/arrays on the roof top, onthe ground or on the poles/masts, at an angle of tilt with the horizontal inaccordance with the latitude of the place of installation as detailed in clause2.2.1.2.2.6. The following may be assured about the mounting structure :

a) The Mounting structure shall be so designed to withstand the wind speed of

200KM/hour. It may be ensured that the design has been certified by a

recognised Lab/Institution in this regard.

b) The mounting arrangement shall be suitable for column mounting or flat

surface, as per site requirement. The same may clearly indicted in the

ordering information.

c) Provision for directional and angular adjustment, as arrived at in clause2.2.1.2.2.6, to ensure the optimum utilisation of incident sunlight.

d) The design/drawings of the mounting structure may referred to at the time of

installation.

e) It may be ensured that the mounting structure designed can withstand the

ultimate weight of the panel/array at wind speed of 200KM/hour.

f) The mounting structure steel is as per IS 2062: 1992 and Galvanisation of the

mounting structure shall be in compliance of IS 4759 latest issue.

g) The exact mounting mechanism shall have to be decided and specified at thetime of ordering.

2.1.1.5 Wires/Cables :

Wires, cables are used for interconnection of :

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- Modules/panels within array

- Array & Charge Controller

- Charge Controller & Battery

- Charge controller & Loads Including Inverter (if used) & between load & inverter.

2.1.1.5.1 All these wires & cables are insulated wires/cables. The insulation material usedin these cables & wires may be either thermoplastic or rubber. Now a days maininsulating material is thermoplastic. Different thermoplastic are used fordifferent environmental conditions. While choosing a cable or wire it may beensured that the insulating material can withstand Indian conditions of :

- 90% humidity at a temperature of 45 degree Celsius

- Very high dry temperature of 75 Degree Celsius.

- Sub Zero temperature of colder regions.

- Fire retardant and rodent repellent.

2.1.1.5.2 Rating of the Cable/wire :

Two main factors which are to be considered while deciding the rating of thecable/wire are :

- The Ampere rating of the cable/wire

- The voltage drop for the required length

2.1.1.5.2.1 Cable Ampere rating :

Factors to be considered while calculating ampere rating for the system :

a) Cable for inter-modular connections & between SPV array & Chargecontroller :

- The cable selected shall be capable of with standing a continuous

temperature of 75 Degree Celsius.

- Isc (short Circuit Current) shall be taken as a current for choosing the cable.

- 25% factor shall be added for possible environmental factors such as Bright

clouds & ground reflection

- Another 25% shall be added to ensure that the cable is not stressed at its

rated value for all the times.

- The cables/wires are normally designed at 30 degree Celsius. At higher

temperature the current rating of the cables is decreased. Simple formula for

this which may be adopted is that every 5 degree increase in temperature

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the Ampere rating is reduced by 6 %.

Considering all the above facts the cable current rating shall be :

Isc of the system X1.25X1.25X(1-0.06(t-30)) = Isc X 1.56 X(0.06(t-30)).

Where t is the optimum temperature at which the cable may work.

In case where the maximum ambient temperature is below 30 degree Celsiust-30 shall be taken as zero.

2.1.1.5.2.2 Cable rating in accordance with permissible voltage drop :

The permissible voltage drop from the SPV Generator to the Charge controller shallnot be more than 2% of peak power voltage of the SPV power source (generatingsystem). In the light of this fact the cross-sectional area of the cable chosen besuch that the voltage drop introduced by it shall be with 2% of the system voltageat peak power. The relation between the area of cross-section of the cable,Ampere rating & Voltage loss factor are as given below :

Dia of the conductor(mm2)

Ampere rating of the cable(A)

Voltage Loss FactorVolts/Amp./metre

2.5 32 0.0028234.0 42 0.0017756.0 54 0.001117

10.0 73 0.000702316.0 98 0.000441625.0 129 0.000277835.0 158 0.0001747

50.0 198 0.000138570.0 245 0.000109995.0 292 0.0000871120.0 344 0.0000691150.0 391 0.000548

The cable may be chosen as given below :

Voltage loss factor = Voltage X 0.02/SPV Generating System Rating inAmps/Cable length.

Where 0.02 is factor for permissible voltage drop of 2%.

Corresponding Area cross section of the cable may selected.

Compare the area of cross section with the one calculated to find the Amp. Rating.Higher of the two may taken as the required cable.

2.1.1.6 Earthing Requirements :

Earthing is essential for the protection of the equipment & manpower. Two main

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grounds used in the power equipments are :

- System earth- Equipment earth

System earth is earth which is used to ground one leg of the circuit. For example

in AC circuits the Neutral is earthed while in DC supply +ve is earthed.

In case equipment earth all the non-current carrying metal parts are bondedtogether and connected to earth to prevent shock to the man power & also theprotection of the equipment in case of any accidental contact.

To prevent the damage due to lightning the one terminal of the lightning protectionarrangement is also earthed. The provision for lightning & surge protection of theSPV power source & Charge controller has been made in the GR for SPV Powersystems. It may be ensured that the lightning and surge protection arrangementhas been made in accordance with the provision of the respective GR.

In case the SPV Array can not be installed close to the equipment to be powered& a separate earth has been provided for SPV System It shall be ensured that allthe earths are bonded together to prevent the development of potential differencebetween ant two earths.

Earth resistance shall be as per telecom standards but shall not be morethan 5 ohms. It shall be ensured that all the earths are bonded together tomake them at the same potential.

The earthing conductor shall rated for the maximum short circuit current. & shallbe 1.56 times the of the short circuit current. The area of cross-section shall not beless than 1.6 mm in any case.

2.1.2 Planning for Hybrid Power supply :

The SPV Power supply is easily manageable for daily loads up to 30 KWH. At

places where AC commercial mains are available but are erratic and available for

a very short duration, a hybrid power supply using a combination of AC commercial

mains & SPV power source may be used. As SPV power requires a very high

initial cost, such combination can effectively used to achieve lesser capital cost

while maintaining the same level of power supply conditions.

In larger hybrid systems, composed of SPV Power source & conventional power

source such as AC mains, the system may be so designed that 50 to 75% of itload requirements are met by SPV system and remaining 25 to 50% are met by

AC mains.

The design and planning of such systems shall be made in such a way that the

balance between the load requirements and best economy is achieved.

Sizing of SPV power source : Size of SPV power source shall be calculated in

same way as in case of stand alone SPV system except that the load shall be

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taken as 50 to 75% as decided. Full Sun power/day shall be taken as an average

instead of minimum over the year.

Sizing of the battery : The battery capacity shall be calculated for 1 to 2 day

backup as decided. Rest of the calculations shall be done in the same way as

done for stand alone SPV power systems.

Sample calculations :

Suppose the battery capacity for a given load requirements is 600AH.

Sizing the Float Rectifier(FC) : FC rating shall be calculated using the formula :

FC Rating = (Battery AH capacity X 0.1 X FC rating factor)/permissible loading

factor

Where : 0.1 is the charging battery current at C/10 rate of chargeFC rating factor shall be taken as 1.2

Permissible loading factor in Telecom application is taken as 90%.

SMPS power supplies as per GR No. GR/SMP-01/05 JAN 2005 or any latest issue

may be used for the application.

2.2 Installation and Maintenance Practice :

2.2.1 General Safety Rules :

2.2.1.1 While working on SPV System :

- Become fully conversant with the system.

- Remove all the metallic jewellery around neck wrists & hands before working on

SPV Array.

- Have full knowledge about the use tools& test instruments.

- Never work on SPV power source alone.

- Know about the first aid practices.

- Work on the system with alert mind and steady hands.

- Work on the array before Sun rise or after Sun set. Or cover the array with someopaque cover or thick blanket to ensure it is not producing energy.

- Washing of the modules/panels of the array shall only be done before Sun rise or

sufficiently after Sun set to prevent thermo shock to the top glass cover of the

modules.

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2.2.1.2 While Working on batteries :

- Remove all metallic jewellery around neck wrists & hands before working on

batteries.

- Use acid proof protections for body, hands & eyes.

- Fresh water & Backing soda shall be easily assessable.

- Keep the open flames sparks away from battery.

- While working on battery disconnect it from charger & load.

- Cover the battery terminals with insulating covers.

- Battery shall be placed at proper ventilated place.

- Follow the manufacturers guidelines for installation & maintenance of battery.

- Use only proper tools while working on the battery. Tools shall be short and non-

working part or handle of the tool shall be either insulated or provided with

insulating to prevent accidental shorting of the terminals while working on it.

2.2.2 Installation of SPV Power supply :

2.2.2.1 Choosing the site for the installation of SPV Array and equipment :

Once the Size of the SPV array, battery & DG set along with rectifier unit ( in case

of Hybrid Systems) has been decided for the given load, the most important factor

remains to be decided is the site for equipment room and SPV array and the type

of the mounting structure to be used i.e. Ground, Roof top or pole mounting. The

following factors may be taken into account for deciding the above :

- The equipment room and SPV array may be as near as possible to avoid

voltage drop.

- SPV array is protected from intrusion of people and animals.

- SPV array is away from the birds colonies to avoid droppings.

- SPV array shall be away from the tall trees, buildings other potential shading

objects so as to ensure that no part of the array comes in the shadow zone

during the peak energy hours i.e between 9 AM and 3 PM. For this array

spacing from the objects may be calculated by the following formula :

Distance of the array from the object = Object Height X Spacing factor.

Spacing factor depends on the latitude of a site. A chart showing the relation

between the latitude of the site and spacing factor is as given below :

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SpacingFactor

Latitude (degrees)

SpacingFactor

Latitude (degrees)

Spacing Factor for No Array Shading

For example to find the location of the SPV array at a place ( latitude 30 degree N)so that a tree of height 2 meter does cast shadow in the SPV array during the fullSun insolation period shall be :

2 X 2 = 4 metre away from the tree.

Where : First 2 is the height of the tree & the second 2 is the spacing factor readfrom the graph above.

2.2.2.2 Installation of SPV array and other equipments :

For other equipment following the manufacturers Guidelines for installation ofcharge controller, inverter & DG set (if used) & battery. The cabling and wiring shallbe of proper rating as calculated & done in accordance with the suppliers flowchart.

Installation of SPV array, after deciding the location and orientation shall be doneas per the manufacturers guidelines.It shall be ensured that foundation for the mounting structure is in accordance withthe mounting structure requirements and capable to withstand the loading windspeed and other requirements as specified.

The work of installation of array shall be done either in the evening after Sunset orbefore Sunrise or the panels shall be covered with some opaque material so as toensure that no energy is produced during installation.

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All the cables & wires shall be of proper rating and as per environmentrequirements.

Note : The following may be verified before assembly of the SPV array :

- All the modules are of equal rating with in the specified tolerance.

- All the modules of 36 cells.

- Necessary By pass diodes have been provided.

- The SPV array shall not be directly mounted on the roof or floor as it elevates

the temperature of the panels by 10 to 20 Degree Celsius. A minimum spacing

of 30 cm may be ensured between the floor and array mounting.

2.3 Maintenance Schedule & Guidelines :

2.3.1 Fortnightly :

a. Check the charge controller for proper alarms indications & proper functioning

by operating Alarm Check Key.

b. For VRLA batteries check the voltages :

1. Between 13.00 and 14 hours on a bright sunny day for any mark

deviation in cell voltages (the indication of cell deterioration).

2. After 2 hours of discharge to know the charge condition of the battery

or any sign of deterioration.

3. For flooded batteries follow the battery maintenance guidelines issued

by the manufacturer.

4. Inspect the modules/panels of the array for any damage.

2.3.2 Bi-Monthly :

a. Check the wiring for physical damage & also for any sign of excessive heating.

b. Check all the junction Boxes for covers and sealing.

c. Check the nut-bolts of the mounting structure and array for proper torque &

tightening.

d. Inspect the modules/panels of the array for any damage.

e. Check the battery terminals for corrosion & proper torque clean and apply

anti-oxy-dent jelly if necessary

2.3.3 Six Monthly

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a. Check cells for decolouration or breakage.

b. Clean the modules/panels of the array for dust if required.

c. Check for all the connection and ensure that they are not loose.

d. Verify the array output for Voc, Vmp, Isc & Imp for any signs of deterioration.e. Check & Verify that the array does not comes under shadow during 9 to 15

hours.

END OF PART - 2

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ANNEXURE - 1

List of Recommended Tools and Test Instruments

S.No. Test Instrument

1. Voltmeter Digital (10A current capacity minimum)

2. External shunts as per load requirements.

3. DC Ammeter (preferably Clamp on)

4. AC Voltmeter and ammeter if AC is used.

5. Compass

6. Plumb-bob

7. Measuring Tape

8. Wrenches as per requirements9. Screwdrivers as per requirement.

10. Wire Stripping, cutting and crimping tools

11. Thermometers or thermister probs.

12. Light Intensity meter or Pyrometer

13. Soldering Iron with soldering of wire

14. Knife, hammer, chisel, saws as per requirements.

15. Hydrometer (if conventional Flooded battery is used)

END OF ANNEXURE - 1

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ANNEXURE - 2

Terminology (Terms used)

1. Short Circuit Current : The maximum current produced by a device under givenconditions of light and Temperature when a short is applied at its output terminals.Output Voltage & power in this condition approaches Zero.

2. Open Circuit Voltage : The maximum voltage from a device under given conditions of lightand temperature. This corresponds to maximum voltage potential but zero current flow.

3. Current at Peak or Maximum Power : The current that results in maximum powerunder the given conditions of light and temperature. It is used as the rated current of thedevice.

4. I-V Curve : The curve representing a snap-shot of all the potential combination of currentand voltage possible from a generating source in a given environmental conditions.

5. Voltage at Peak or maximum Power : The voltage that results in maximum poweroutput under the given conditions of light and temperature. It is used as the rated voltageof a device and is used to determine the number of cells or modules required to match theload voltage requirements.

6. Voltage De-rating : Loss of Output voltage of SPV Module or Panel due to increase intemperature over the specified ambient temperature.

7. Peak or Maximum Power : The maximum output power from a device under givenconditions of light and temperature. It is equal to the product of current and voltage atmaximum power.

8. SPV Cell : It is the basic Building Block of the Solar photo-voltaic system.

9. Module : It is collection of cells interconnected by a flat wire. It also includes encapsulationto protect the cells and interconnecting wires for corrosion and impact. Cells connected inseries determine the voltage of the modules.

10. Panel : It is collection of modules physically and electrically grouped on a commonstructure.

END OF ANNEXURE - 2

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ANNEXURE - 3Abbreviations

A or Amps Amperes

AC Alternating Current

AH Ampere HourAM Air Mass

BIS Bureau Of Indian Standards

BSNL Bharat Sanchar Nigam Limited

CACT Component Approval Centre of Telecommunication

DC Direct Current

Deg. Degree

deg. C Degrees Celsius

DG Diesel Generator

DOT Department of Telecommunication

emf Electro motive force

EMI Electro Magnetic Interference

FET Field Effect Transistor

gL/gG General line/General Gracia (slow action fuses)

GR Generic RequirementsIEC International Electrotechnical Commission.

IS Indian Standard

I-V Current vs Voltage

Isc Short Circuit Current

Imp Current at maximum power

Kg Kilo Grams

KHz Kilo Hertz

KW Kilo Watts

LED Light Emitting Diodes

LCD Liquid Crystal Device

MCB Miniaturised Circuit Breaker

MHz Meg Hertz

MOV Metal Oxide Varistor

MTBF Mean Time between FailuresMTNL Mahanagar Telephone Nigam Limited

ms mili seconds

nm Neon metre

PCB Printed Circuit Board

PF Power factor

PIV Peak Inverse Voltage

PTC Positive Temperature Co-efficient

QA Quality Assurance

QM Quality Manual

RFI Radio Frequency Interference

RTEC Regional Telecom. Engineering Centre

SMPS Switch Mode Power Supply

SPV Solar Photo voltaic

SS Self SupportingTEC Telecommunication Engineering Centre

V Volts

Voc Voltage Open Circuit

Vmp Voltage at Maximum Power

VRLA Valve Regulated Lead Acid

END OF ANNEXURE - 3

spv planning guidelines

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