Solar Lighting Systems Module - Ministry of New and Renewable

Transcription

Solar Lighting Systems Module
Trainers Textbook
Study materials in Renewable Energy Areas
for ITI students
Ministry of New and Renewable Energy
Government of India
Content Development, Editing, Design and Layout
New Concept Information Systems Pvt. Ltd
E-mail: [email protected]
www.newconceptinfo.com
Study materials in
Renewable Energy Areas
for ITI students
Trainers Textbook
Module: Solar Lighting Systems
Ministry of New and Renewable Energy
Government of India
Study materials in Renewable Energy
Areas for ITI students
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Contents
Unit 1: Solar energy and Photovoltaic
1.1 Solar Energy
1.1.1 Energy from the Sun
1.2 Applications of solar energy technology
1.3 Photovoltaic Basics
1.4 Difference between Photovoltaic effect and Photoelectric effect
1.5 Working of Photovoltaic cell
1.5.1 Lights and the PV Cell
1.5.2 Direct and Diffuse Light
1.5.3 Insolation
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Unit 2: Solar Cell Materials and Structures
2.1 PV Devices
2.2 Solar Cell Materials
2.2.1 Crystallinity
2.2.2 Absorption
2.2.3 Band gap
2.2.4 Complexity of Manufacturing
2.3 Solar Cell Structures
2.3.1 Homojunction Device
2.3.2 Heterojunction Device
2.3.3 Multijunction Devices
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Unit 3: Solar Chargers, Batteries and Inverters
Introduction
3.1 What is a solar charge controller?
3.1.1 Blocking Reverse Current
3.1.2 Preventing Overcharge
3.1.3 Control Set Points v/s Temperature
3.1.4 Control Set Points v/s Battery Type
3.1.5 Low Voltage Disconnect (LVD)
3.1.6 Overload Protection
3.1.7 Displays and Metering
3.1.8 Charge Controller Types
3.2 What is Equalization?
3.3 What is Pulse Width Modulation (PWM)?
3.4 Inverters and Storage Battery
3.4.1 Sine Waves
3.5 Ampere Hour
3.6 Cell & Batteries:
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3.7 Breadboard
3.7.1 Typical specifications
3.7.2 Bus and terminal strips
3.7.3 Terminal strips
3.7.4 Bus strips
3.7.5 Diagram
3.7.6 Terminal Strip
3.7.7 Bus Strip
3.8 Series Parallel Connection of Solar Panel and the Effect of Shading:
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Unit 4: PV Devices in India
4.1 Introduction
4.1.1 Standard Capacity/Ratings and Specifications
4.2 Compact Fluorescent Lamps
4.2.1 How They Work
4.2.2 Types of Compact Fluorescent Lamps
4.3 Specifications for Solar Photovoltaic Systems (CFL Based)
4.3.1 Solar Home Lighting Systems
4.3.2 Solar Street Lighting System
4.4 Specifications for LED based solar lighting systems
4.4.1 White LED Based Solar Home Lighting Systems
4.4.2 White LED Based Solar Lantern System
4.4.3 White LED Based Solar Street Lighting Systems
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Unit 5: Maintenance and Troubleshooting
5.1 Routine Maintenance
5.1.1 Battery maintenance
5.1.2 Cleaning (once a month)
5.1.3 Checking and Topping up Electrolyte level (monthly)
5.1.4 Checking the state of Charge
5.1.5 Equalising Charge
5.1.6 Module Maintenance
5.1.7 Checking Connections
5.1.8 Wiring and control
5.1.9 Inspecting wiring, fuses, indicator lamps and switches (annual)
5.1.10 Lamps and Other Loads
5.2 Troubleshooting
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Unit 6: Practicals
6.1 Tilt angle
6.2 Latitude
6.2.1 Optimum Tilt for winter
6.3 Square Wave
6.4 Sine wave
6.5 Schematic Diagram
6.6 Inspection of batteries
6.6.1 Safety
6.6.2 Battery Testing
6.3.3 Battery Capacity
6.7 Table showing the cable selection
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Trainers textbook for
Solar Lighting Systems
Unit 1: Solar energy and Photovoltaic
Time: 1 hour
Method: Presentation
1.1 Solar Energy
Solar energy is energy from the Sun in the form of radiated heat and light. It drives
the climate and weather and supports life on Earth. Solar energy technologies make
controlled use of this energy resource.
Solar power is a synonym of solar energy or refers specifically to the conversion of
sunlight into electricity by photovoltaic cells, concentrating solar thermal devices or
various experimental technologies.
1.1.1 Energy from the Sun
About half the incoming solar energy is absorbed by water and land; the rest is reradiated
back into space.
Earth continuously receives 340 Wm-2 of incoming solar radiation (insolation) at the upper
atmosphere. Approximately 30% is reflected back to space while the rest is absorbed by
the atmosphere, oceans and land masses. After passing through the atmosphere, the
insolation spectrum is split between the visible and infrared ranges with a small part in
the ultraviolet.
The absorption of solar energy by atmospheric convection (sensible heat transport) and
evaporation and condensation of water vapor (latent heat transport) powers the water
cycle and drives the winds. Sunlight absorbed by the oceans and land masses keeps the
surface at an average temperature of 14 °C. The conversion of solar energy into chemical
energy via photosynthesis produces food, wood and the biomass from which fossil fuels
are derived.
Solar radiation, along with secondary solar resources such as wind and wave power,
hydroelectricity and biomass, account for over 99.9% of the available flow of renewable
energy on Earth. The flows and stores of solar energy in the environment are vast in
comparison to human energy needs.

The total solar energy absorbed by Earth's atmosphere, oceans and land masses is
approximately 3850 zettajoules (ZJ) per year.
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Global wind energy at 80 m is estimated at 2.25 ZJ per year.
Photosynthesis captures approximately 3 ZJ per year in biomass.
Worldwide electricity consumption was approximately 0.0567 ZJ in 2005.
Worldwide energy consumption was 0.487 ZJ in 2005.
# 1 zettajoule = 1021 joules.
1.2 Applications of solar energy technology
Solar energy technologies use solar radiation for practical ends. Solar technologies
such as photo-voltaics and water heaters increase the supply of energy and may be
characterized as supply side technologies. Technologies such as passive design and
shading devices reduce the need for alternate resources and may be characterized as
demand side. Optimizing the performance of solar technologies is often a matter of
controlling the resource rather than simply maximizing its collection.
1.3 Photovoltaic Basics
What do we mean by photovoltaics? First used in about 1890, the word has two parts:
photo, derived from the Greek word for light, and volt, relating to the electricity pioneer
Alessandro Volta. So, photovoltaics could literally be translated as light-electricity. And
that's what photovoltaic (PV) materials and devices do — they convert light energy
into electrical energy (Photoelectric Effect), as discovered by renowned physicist Albert
Einstein.
Commonly known as solar cells, individual PV cells are electricity-producing devices
made of semiconductor materials. PV cells come in many sizes and shapes — from
smaller than a postage stamp to several inches across. They are often connected together
to form PV modules that may be up to several feet long and a few feet wide. Modules, in
turn, can be combined and connected to form PV arrays of different sizes and power
output.
The size of an array depends on several factors, such as the amount of sunlight available
in a particular location and the needs of the consumer. The modules of the array make up
the major part of a PV system, which can also include electrical connections, mounting
hardware, power-conditioning equipment, and batteries that store solar energy for use
when the sun isn't shining.
Simple PV systems provide power for many small consumer items, such as calculators and
wristwatches. More complicated systems provide power for communications satellites,
water pumps, and the lights, appliances, and machines in some people's homes and
workplaces. Many road and traffic signs along highways are now powered by PV. In many
cases, PV power is the least expensive form of electricity for performing these tasks.
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1.4 Difference between Photovoltaic effect and Photoelectric effect
The photovoltaic effect involves the creation of a voltage (or a corresponding electric
current) in a material upon exposure to electro-magnetic radiation. Though the process
is directly related to the photoelectric effect, the two processes are different and should
be distinguished.
In the photoelectric effect electrons are ejected from a materials surface upon exposure
to radiation of sufficient energy. The photovoltaic effect is different in that the generated
electrons are transferred from one material to another resulting in the buildup of a
voltage between two electrodes.
In most photovoltaic applications the radiation is sunlight and for this reason the devices
making use of the photovoltaic effect to convert solar energy into electrical energy are
known as solar cells. In the case of a p-n junction solar cell, illumination of the material
results in the creation of an electric current as excited electrons and the remaining holes
are swept in different directions by the built in electric field of the depletion region.
1.5 Working of Photovoltaic cell
The energy of the absorbed light is transferred to electrons in the atoms of the PV cell.
With their newfound energy, these electrons
escape from their normal positions in the
atoms of the semiconductor PV material and
become part of the electrical flow, or current,
in an electrical circuit. A special electrical
property of the PV cell—what we call a "builtin electric field"—provides the force, or
voltage, needed to drive the current through
an external "load," such as a light bulb.
To induce the built-in electric field within
a PV cell, two layers of somewhat differing
semiconductor materials are placed in
contact with one another. One layer is an "ntype" semiconductor with an abundance of
electrons, which have a negative electrical
charge. The other layer is a "p-type"
semiconductor with an abundance of "holes,"
which have a positive electrical charge.
Although both materials are electrically neutral, n-type silicon has excess electrons and
p-type silicon has excess holes. Sandwiching these together creates a p/n junction at
their interface, thereby creating an electric field.
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When n- and p-type silicon come in contact with each other, excess electrons move from
the n-type side to the p-type side. The result is a buildup of positive charge along the ntype side of the interface and a buildup of negative charge along the p-type side.
How do we make the p-type ("positive") and n-type ("negative") silicon materials that
will eventually become the photovoltaic (PV) cells that produce solar electricity? Most
commonly, we add an element to the silicon that either has an extra electron or lacks an
electron. This process of adding another element is called doping.
1.5.1 Lights and the PV Cell
We've looked at how to construct a solar cell using crystalline silicon. And we've used
this basic type of cell to explain the photoelectric effect, which is the phenomenon
operating at the heart of a solar cell. Here, we want to take a look at sunlight, the energy
source actually used by solar cells. A brief discussion of several terms will help us better
understand aspects of light's interaction with solar cells.
1.5.2 Direct and Diffuse Light
As we have noted, the Earth's atmosphere
and cloud cover absorb, reflect, and scatter
some of the solar radiation entering the
atmosphere. Nonetheless, an enormous
amount of the sun's energy reaches the
Earth's surface and can therefore be used
to produce PV electricity. Some of this
radiation is direct and some is diffuse, and
the distinction is important because some
PV systems (flat-plate systems) can use both
forms of light, but concentrator systems can only use direct light.
Flat-plate collectors, which typically contain a large number of solar cells mounted on a
rigid, flat surface, can make use of both direct sunlight and the diffuse sunlight reflected
from clouds, the ground, and nearby objects.
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Direct light consists of radiation that comes straight from the sun, without reflecting
off the clouds, dust, the ground, or other objects. Scientists also talk about directnormal radiation, referring to the portion of sunlight that comes directly from the
sun and strikes the plane of a PV module at a 90-degree angle.
Diffuse light is sunlight that is reflected off clouds, the ground, or other objects. It
obviously takes a longer path than a direct light ray to reach a module. Diffuse light
cannot be focused by the optics of a concentrator PV system.
Global radiation refers to the total radiation that strikes a horizontal surface.
Global sunlight is composed of direct-normal and diffuses components of sunlight.
Additionally, diffuse and direct-normal sunlight generally have different energy
spectra or distributions of color.
1.5.3 Insolation
The actual amount of sunlight falling on a specific geographical location is known as
insolation—or "incident solar radiation."
When sunlight reaches the Earth, it is distributed unevenly in different regions. Not
surprisingly, the areas near the Equator receive more solar radiation than anywhere else
on the Earth. Sunlight varies with the seasons, as the rotational axis of the Earth shifts to
lengthen and shorten days with the changing seasons
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Unit 2: Solar Cell Materials and
Structures
Time: 2 hours
Method: Demonstration of the devices, presentation
2.1 PV Devices
Photovoltaic devices can be made from various types of semiconductor materials,
deposited or arranged in various structures, to produce solar cells that have optimal
performance.
In this section, we first review the three main types of materials used for solar cells.
The first type is silicon, which can be used in various forms, including single-crystalline,
multicrystalline, and amorphous.
The second type is polycrystalline thin films, with specific discussion of copper indium
di selenide (CIS) cadmium telluride (CdTe), and thin-film silicon.
The third type of material is single-crystalline thin film, focusing especially on cells made
with gallium arsenide.
We then discuss the various ways that these materials are arranged to make complete solar
devices. The four basic structures we describe include homojunction, heterojunction,
and multijunction devices.
2.2 Solar Cell Materials
Solar cells can be made from a wide range of semiconductor materials. In the following
sections, we will discuss:
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Silicon (Si)—including single-crystalline Si, multicrystalline Si, and amorphous Si
Polycrystalline thin films—including copper indium diselenide (CIS), cadmium
telluride (CdTe), and thin-film silicon
Single-crystalline thin films—including high-efficiency material such as gallium
arsenide (GaAs)
First, though, we provide an overview of aspects that relate to all materials. The aspects
we will cover are crystallinity, absorption, bandgap, and complexity of manufacturing.
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2.2.1 Crystallinity
The crystallinity of a material indicates how perfectly ordered the atoms are in the
crystal structure. Silicon, as well as other solar cell semiconductor materials, can come
in various forms: single-crystalline, multicrystalline, polycrystalline, or amorphous. In a
single-crystal material, the atoms making up the framework of the crystal are repeated
in a very regular, orderly manner from layer to layer. In contrast, in a material composed
of numerous smaller crystals, the orderly arrangement is disrupted moving from one
crystal to another.
2.2.2 Absorption
The absorption coefficient of a material indicates how far light having a specific
wavelength (or energy) can penetrate the material before being absorbed. A small
absorption coefficient means that light is not readily absorbed by the material. Again,
the absorption coefficient of a solar cell depends on two factors: the material making
up the cell, and the wavelength or energy of the light being absorbed. Solar cell material
has an abrupt edge in its absorption coefficient. The reason is that light whose energy is
below the material's band gap cannot free an electron. And so, it isn't absorbed.
2.2.3 Band gap
The band gap of a semiconductor material is an amount of energy. Specifically, it's the
minimum energy needed to move an electron from its bound state within an atom to a free
state. This free state is where the electron can be involved in conduction. The lower energy
level of a semiconductor is called the "valence band." And the higher energy level where an
electron is free to roam is called the "conduction band." The bandgap (often symbolized
by Eg) is the energy difference between the conduction band and valence band.
2.2.4 Complexity of Manufacturing
The most important parts of a solar cell are the semiconductor layers, because this is
where electrons are freed and the electric current is created—it's the active layer "where
the action is," so to speak. Several different semiconductor materials are used to make the
layers in different types of solar cells, and each material has its benefits and drawbacks.
The cost and complexity of
manufacturing may vary across
these
materials
and
device
structures based on many factors,
including deposition in a vacuum
environment, amount and type of
material utilized, number of steps
involved, need to move cells into
different deposition chambers or
processing processes, and others.
Sunlight
Antireflection coating
Transparent adhesive
Cover glass
n-Type semiconductor
p-Type semiconductor
Front Contact
Current
Substrate
Back contact
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A typical solar cell consists of a glass or plastic cover or other encapsulants, an antireflective
layer, a front contact to allow electrons to enter a circuit, a back contact to allow them
to complete the circuit, and the semiconductor layers where the electrons begin and
complete their journey.
2.3 Solar Cell Structures
2.3.1 Homojunction Device
Crystalline silicon is the primary example of this kind of cell. A single material—crystalline
silicon—is altered so that one side is p-type, dominated by positive holes, and the other
side is n-type, dominated by negative electrons. The p/n junction is located so that the
maximum amount of light is absorbed near it. The free electrons and holes generated
by light deep in the silicon diffuse to the p/n junction, and then separate to produce a
current if the silicon is of sufficient high quality.
2.3.2 Heterojunction Device
An example of this type of device structure is a CIS cell, where the junction is formed
by contacting two different semiconductors—CdS and CuInSe2. This structure is often
chosen for producing cells made of thin-film materials that absorb light much better than
silicon. The top and bottom layers in a heterojunction device have different roles. The top
layer, or "window" layer, is a material with a high bandgap selected for its transparency
to light. The window allows almost all incident light to reach the bottom layer, which is a
material with low bandgap that readily absorbs light. This light then generates electrons
and holes very near the junction, which helps to effectively separate the electrons and
holes before they can recombine.
2.3.3 Multijunction Devices
This structure, also called a cascade or tandem cell, can
achieve higher total conversion efficiency by capturing a larger
portion of the solar spectrum. In the typical multijunction cell,
individual cells with different band gaps are stacked on top of
one another. The individual cells are stacked in such a way that
sunlight falls first on the material having the largest bandgap.
Photons not absorbed in the first cell are transmitted to the
second cell, which then absorbs the higher-energy portion
of the remaining solar radiation while remaining transparent
to the lower-energy photons. These selective absorption
processes continue through to the final cell, which has the
smallest bandgap.
A multijunction device is a stack of individual single-junction
cells in descending order of band gap (Eg). The top cell
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Eg1 > Eg2 > Eg3
Cell 1 (Eg1)
Cell 2 (Eg2)
Cell 3 (Eg3)
captures the high-energy photons and
passes the rest of the photons on to be
absorbed by lower-bandgap cells.
A multijunction cell can be made in
two different ways. In the mechanical
stack approach, two individual solar
cells are made independently, one
with a high bandgap and one with a
lower bandgap. Then the two cells are
mechanically stacked, one on top of
the other. In the monolithic approach,
one complete solar cell is made first,
and then the layers for the second cell
are grown or deposited directly on the
first.
Antireflection
coating
Au grid
n-AllnP2
n-GalnP2
Top cell
p-GalnP2
p+-GalAs
n+-GalAs
Tunnel diode
n-AlGalAs
n-GalAs
Bottom cell
p-GaAs
p+-GaAs
Substrate
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Unit 3: Solar Chargers, Batteries and
Inverters
Time: 1 hour
Method: Demonstration, presentation
Introduction
A standard solar lighting system consists of following components:
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Charge controller
Photo-voltaic module
Battery
Inverter
Light output
3.1 What is a solar charge controller?
A charge controller, or charge regulator is similar to the voltage regulator in your car. It
regulates the voltage and current coming from the solar panels going to the battery. Most
"12 volt" panels put out about 16 to 20 volts, so if there is no regulation the batteries will
be damaged from overcharging. Most batteries need around 14 to 14.5 volts to get fully
charged.
Solar charge controllers are an essential element to any solar electric panel system. At a
most basic level charge controllers prevent batteries from being overcharged and prevent
the batteries from discharging through the solar panel array at night.
The basic functions of a controller are quite simple. Charge Controllers block reverse
current and prevent battery overcharge. Some controllers also prevent battery overdischarge, protect from electrical overload, and/or display battery status and the flow of
power. Let's examine each function individually.
3.1.1 Blocking Reverse Current
Photovoltaic panels work by pumping current through your battery in one direction.
At night, the panels may pass a bit of current in the reverse direction, causing a slight
discharge from the battery. (Our term "battery" represents either a single battery or bank
of batteries.) The potential loss is minor, but it is easy to prevent.
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In most controllers, charge current passes through a semiconductor (a transistor) which
acts like a valve to control the current. It is called a "semiconductor" because it passes
current only in one direction. It prevents reverse current without any extra effort or cost.
In some controllers, an electromagnetic coil opens and closes a mechanical switch. This
is called a relay. (You can hear it click on and off.) The relay switches off at night, to block
reverse current.
If you are using a PV array only to trickle-charge a battery (a very small array relative to the
size of the battery), then you may not need a charge controller. This is a rare application.
An example is a tiny maintenance module that prevents battery discharge in a parked
vehicle but will not support significant loads. You can install a simple diode in that case,
to block reverse current. A diode used for this purpose is called a "blocking diode."
3.1.2 Preventing Overcharge
When a battery reaches full charge, it can no longer store incoming energy. If energy
continues to be applied at the full rate, the battery voltage gets too high. Water separates
into hydrogen and oxygen and bubbles out rapidly. (It looks like it's boiling so we
sometimes call it that, although it's not actually hot.) There is excessive loss of water,
and a chance that the gasses can ignite and cause a small explosion. The battery will also
degrade rapidly and may possibly overheat. Excessive voltage can also stress your loads
(lights, appliances, etc.) or cause your inverter to shut off.
Preventing overcharge is simply a matter of reducing the flow of energy to the battery
when the battery reaches a specific voltage. When the voltage drops due to lower sun
intensity or an increase in electrical usage, the controller again allows the maximum
possible charge. This is called "voltage regulating." It is the most essential function of
all Charge Controllers. The controller "looks at" the voltage, and regulates the battery
charging in response.
Some controllers regulate the flow of energy to the battery by switching the current fully
on or fully off. This is called "on/off control." Others reduce the current gradually. This is
called "Pulse Width Modulation" (PWM). Both methods work well when set properly for
your type of battery.
A PWM Type Solar Charge Controllers holds the voltage more constant. If it has twostage regulation, it will first hold the voltage to a safe maximum for the battery to reach
full charge. Then, it will drop the voltage lower, to sustain a "finish" or "trickle" charge.
Two-stage regulating is important for a system that may experience many days or weeks
of excess energy (or little use of energy). It maintains a full charge but minimizes water
loss and stress.
The voltages at which the controller changes the charge rate are called set points. When
determining the ideal set points, there is some compromise between charging quickly
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before the sun goes down, and mildly overcharging the battery. The determination of
set points depends on the anticipated patterns of usage, the type of battery, and to
some extent, the experience and philosophy of the system designer or operator. Some
controllers have adjustable set points, while others do not.
3.1.3 Control Set Points v/s Temperature
The ideal set points for charge control vary with a battery's temperature. Some controllers
have a feature called "temperature compensation." When the controller senses a low
battery temperature, it will raise the set points. Otherwise when the battery is cold, it will
reduce the charge too soon. If your batteries are exposed to temperature swings greater
than about 30Â° F (17Â° C), compensation is essential.
Some controllers have a temperature sensor built in. Such a controller must be mounted
in a place where the temperature is close to that of the batteries. Better controllers have
a remote temperature probe, on a small cable. The probe should be attached directly to
a battery in order to report its temperature to the controller.
An alternative to automatic temperature compensation is to manually adjust the set
points (if possible) according to the seasons. It may be sufficient to do this only twice a
year, in spring and fall.
3.1.4 Control Set Points v/s Battery Type
The ideal set points for charge controlling depend on the design of the battery. The vast
majority of RE systems use deep-cycle lead-acid batteries of either the flooded type or the
sealed type. Flooded batteries are filled with liquid. These are the standard, economical
deep cycle batteries.
Sealed batteries use saturated pads between the plates. They are also called "valveregulated" or "absorbed glass mat," or simply "maintenance-free." They need to be
regulated to a slightly lower voltage than flooded batteries or they will dry out and be
ruined. Some controllers have a means to select the type of battery. Never use a controller
that is not intended for your type of battery.
Typical set points for 12 V lead-acid batteries at 77Â° F (25Â° C)
(These are typical, presented here only for example.)
High limit (flooded battery): 14.4 V
High limit (sealed battery): 14.0 V
Resume full charge: 13.0 V
Low voltage disconnect: 10.8 V
Reconnect: 12.5 V
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Temperature compensation for 12V battery: -.03 V per Â° C deviation from standard
25Â° C
3.1.5 Low Voltage Disconnect (LVD)
The deep-cycle batteries used in renewable energy systems are designed to be discharged
by about 80 percent. If they are discharged 100 percent, they are immediately damaged.
Imagine a pot of water boiling on your kitchen stove. The moment it runs dry, the pot
overheats. If you wait until the steaming stops, it is already too late!
Similarly, if you wait until your lights look dim, some battery damage will have already
occurred. Every time this happens, both the capacity and the life of the battery will be
reduced by a small amount. If the battery sits in this over discharged state for days or
weeks at a time, it can be ruined quickly.
The only way to prevent over-discharge when all else fails, is to disconnect loads
(appliances, lights, etc.), and then to reconnect them only when the voltage has recovered
due to some substantial charging. When over discharge is approaching, a 12 volt battery
drops below 11 volts (a 24 V battery drops below 22 V).
A low voltage disconnect circuit will disconnect loads at that set point. It will reconnect the
loads only when the battery voltage has substantially recovered due to the accumulation
of some charge. A typical LVD reset point is 13 volts (26 V on a 24 V system).
All modern inverters have LVD built in. The inverter will turn off to protect itself and your
loads as well as your battery. Normally, an inverter is connected directly to the batteries,
not through the charge controller, because its current draw can be very high, and because
it does not require external LVD.
3.1.6 Overload Protection
A circuit is overloaded when the current flowing in it is higher than it can safely handle.
This can cause overheating and can even be a fire hazard. Overload can be caused by a
fault (short circuit) in the wiring, or by a faulty appliance (like a frozen water pump). Some
Charge Controllers have overload protection built in, usually with a push-button reset.
Built-in overload protection can be useful, but most systems require additional protection
in the form of fuses or circuit breakers. If you have a circuit with a wire size for which the
safe carrying capacity (ampacity) is less than the overload limit of the controller, then
you must protect that circuit with a fuse or breaker of a suitably lower amp rating.
3.1.7 Displays and Metering
Charge controllers include a variety of possible displays, ranging from a single red light
to digital displays of voltage and current. These indicators are important and useful.
Imagine driving across the country with no instrument panel in your car! A display
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system can indicate the flow of power into and out of the system, the approximate state
of charge of your battery, and when various limits are reached.
3.1.8 Charge Controller Types
Charge controls come in all shapes, sizes, features, and price ranges. They range from
the small 4.5 amp control, up to the 60 to 80 amp MPPT programmable controllers with
computer interface. Often, if currents over 60 amps are required, two or more 40 to 80 amp
units are wired in parallel. The most common controls used for all battery based systems
are in the 4 to 60 amp range, but some of the new MPPT controls go up to 80 amps.
Charge controllers come in 3 general types (with some overlap):
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Simple 1 or 2 stage controls which rely on relays or shunt transistors to control the
voltage in one or two steps. These essentially just short or disconnect the solar panel
when a certain voltage is reached. For all practical purposes these are dinosaurs, but
you still see a few on old systems. Their only real claim to fame is their reliability they have so few components, there is not much to break.
3-stage and/or PWM: These are pretty much the industry standard now, but you will
occasionally still see some of the older shunt/relay types around, such as in the very
cheap systems offered by discounters and mass marketers.
Maximum power point tracking (MPPT). These are the ultimate in controllers,
with prices to match - but with efficiencies in the 94% to 98% range, they can save
considerable money on larger systems since they provide 15 to 30% more power to
the battery.
3.2 What is Equalization?
Equalization does somewhat what the name implies - it attempts to equalize - or make
all cells in the battery or battery bank of exactly equal charge. Essentially it is a period of
overcharge, usually in the 15 to 15.5 volt range. If you have some cells in the string lower
than others, it will bring them all up to full capacity. In flooded batteries, it also serves
the important function of stirring up the liquid in the batteries by causing gas bubbles.
Of course, in an RV or boat, this does not usually do much for you unless you have been
parked for months, as normal movement will accomplish the same thing. Also, in systems
with small panels you may not get enough current to really do much bubbling.
3.3 What is Pulse Width Modulation (PWM)?
Quite a few charge controls have a "PWM" mode. PWM stands for Pulse Width Modulation.
PWM is often used as one method of float charging. Instead of a steady output from the
controller, it sends out a series of short charging pulses to the battery - a very rapid "onoff" switch. The controller constantly checks the state of the battery to determine how
fast to send pulses, and how long (wide) the pulses will be. In a fully charged battery
18
with no load, it may just "tick" every few seconds and send a short pulse to the battery.
In a discharged battery, the pulses would be very long and almost continuous, or the
controller may go into "full on" mode. The controller checks the state of charge on the
battery between pulses and adjusts itself each time.
Power Tools
Compressors
Computers
Pumps
Appliances
Light
Expend
CHARGER
An inverter is a device that converts
battery power (DC) into alternating
current (AC) of a higher voltage. This
means that most inverters are installed
and used in conjunction with a battery
bank of some sort - a common set up
in off grid solar installations.
INVERTER
3.4 Inverters and Storage Battery
Generator
Power Grid
Shore Power
Solar Wind
Hydro
Replenish
Batteries are the heart of an inverterpowered electrical system, storing
power for use on demand. The most
Power Holding Battery Bank
(Size determines how much you can run for how long.)
basic way to draw electrical power
from a battery is direct current (DC) at
the nominal voltage of the battery. For example, your car radio uses 12 volts DC (12V
DC), the same voltage as your car battery.
A solar inverter is a piece of the solar energy puzzle. Its purpose is to change the direct
current (DC) electricity that is generated from a photovoltaic panel into an alternating
current (AC) that can be used by in-home appliances and the community electricity grid.
Because all photovoltaic panels produce electricity in DC, an inverter is required for all
solar power systems to make the electricity usable.
The solar inverter is often one of the most expensive parts in an alternative energy system.
Because of this, many people fall into the trap of underestimating the structure's needs
for a solar inverter and purchase one that handles a smaller capacity than necessary in
order to save money. One of the recommendations to avoid making this mistake and
keep the up-front costs of a solar energy system down is to initially purchase fewer solar
cells and add more later rather than skimping on the inverter.
One of the biggest issues of a solar power system is efficiency. The cost of building and
installing a system is often expensive, and those who are willing to make the financial
investment in solar energy want to be sure to get their money's worth. Not only do the
solar cells need to convert the sun's energy to electricity efficiently, but the solar inverter
has a responsibility in efficiency as well.
To explain how solar inverters work, we must start from the basics. The sun shines down
onto photovoltaic PV cells. These cells are made of semiconductor layers of crystalline
silicon or gallium arsenide, and they are arranged into panels.
19
The semiconductor layers are a
combination of both positive and
negative layers, and they are connected
through a junction.
Grid Tie
Inverter
Load
Center
Basically, as the sun shines down, the
semiconductor material absorbs the
Utility
light, transferring the light’s energy
Grid
to the PV cell. This energy knocks
Solar
Utility
electrons loose, and they move
Array
Meter
from one layer to the other, thereby
producing an electric current. This is
a direct current (DC). The energy created is then generally either stored in a battery bank
for later use or sent directly to an inverter, depending on the set up and type of system.
For regular consumer use, and alternating current (AC) is needed –230 volt AC powered
home appliances require AC electricity. This is where an inverter comes in. The inverter
takes the direct current and, in simplified terms, runs it through a transformer. It is almost
as though the inverter is tricking the transformer into thinking it is getting AC by forcing the
DC to act in a way similar to AC – the inverter runs the DC through two or more transistors
that are rapidly turned on and off and feeding two different sides of the transformer.
3.4.1 Sine Waves
The DC electricity produced in the PV cells does not have a wave form, but is rather a
direct line (hence its name, direct current.) Basically, to become AC, it must become a
sine wave (on an x-y graph, the sine wave rises from 0 to a positive point, then back down
through zero to a negative point and back up to 0. This known as one cycle or a hertz – a
regular sine wave has 60 hertz per second [the sine wave continues to repeat itself 60
cycles per second.])
The alternating current used by a city electric grid is a true sine wave. It runs smoothly up
and down in an arced, wave-like motion. Of course, an inverter that produces a pure sine
wave often costs more than other inverters – only higher quality solar inverters produce
true sine waves.
A modified sine wave, on the other hand, rises up to the positive point and down to the
negative point in steps – it looks like a stepped square wave. While many appliances will
run on this type of sine wave, they may not run as well (e.g. while computers and TV’s will
run, certain bread makers, microwaves, washer and dryers, etc. may have problems with
the modified sine wave.) Also, items with motors will end up using more power when
using a modified sine wave versus a true sine wave.
Note that the effectiveness of modified sine wave inverters (also known as quasi-sine
wave inverters and modified square wave inverters) can vary between different inverters
20
and can vary depending on the load. The least effective modified sine wave inverters are
only useful for very basic appliances like toasters and appliances that use only a heating
element.
Solar photovoltaic modules generate direct current (DC) electricity (they take the sun’s
energy and convert it into DC electricity). However, the vast majority of electric current
used in households is alternating current (AC). This is why an inverter is necessary: it
inverts DC into AC.
Direct current is an electric current that has a constant direction and a constant
magnitude. An example of a source of direct current is batteries. With direct current, it is
difficult to raise the voltage high enough for energy transfer and then lower it so that it is
once again safe for domestic use. This makes it difficult to use for long-distance power
transmission.
Alternating current, on the other hand, reverses direction and has a varying magnitude.
By using transformers, it is easy to raise and also lower the voltage of alternating current.
This means it can be kept at lower levels for both industrial and domestic use, but raised
to high levels for transmission.
3.5 Ampere Hour
An ampere-hour or amp-hour (symbol Ah, A·h, A h) is a unit of electric charge, with
sub-units milliampere-hour (mAh) and milliampere second (mAs). One ampere-hour
is equal to 3,600 coulombs (ampere-seconds), the electric charge transferred by a steady
current of one ampere for one hour.
The ampere-hour is frequently used in measurements of electrochemical systems such
as electroplating and electrical batteries.
The commonly seen milliampere-hour (mAh or mA·h) is one-thousandth of an amperehour (i.e., 3.6 coulombs), and is a technical term for how much electrical charge a
particular battery will hold. Small batteries, such as those in laptops and digital cameras,
are often rated in milliampere-hours. As an example, digital camera batteries with higher
mAh values theoretically last longer without requiring a recharge, allowing one to take
more photographs before having to replace the batteries.
A milliampere second (mAs or mA·s) is a unit of measure used in X-ray diagnostic imaging
and radiation therapy. This quantity is proportional to the total X-ray energy produced by
a given X-ray tube operated at a particular voltage. The same total dose can be delivered
in different time periods depending on the X-ray tube current.
The Faraday constant is the charge on one mole of electrons and is approximately equal
to 26.8 ampere-hours, and is used in electrochemical calculations.
21
3.6 Cell & Batteries:
An electrical battery is a combination of
one or more electrochemical cells, used
to convert stored chemical energy into
electrical energy. Since the invention of the
first Voltaic pile in 1800 by Alessandro Volta,
the battery has become a common power
source for many household and industrial
applications, and is now a multi-billion
dollar industry.
A battery is a device that converts chemical
energy directly to electrical energy. It consists
of a number of voltaic cells; each voltaic
cell consists of two half cells connected in
series by a conductive electrolyte containing anions and cations. One half-cell includes
electrolyte and the electrode to which anions (negatively-charged ions) migrate, i.e. the
anode or negative electrode; the other half-cell includes electrolyte and the electrode to
which cations (positively-charged ions) migrate, i.e. the cathode or positive electrode.
In the redox reaction that powers the battery, reduction (addition of electrons) occurs
to cations at the cathode, while oxidation (removal of electrons) occurs to anions at the
anode. The electrodes do not touch each other but are electrically connected by the
electrolyte. Many cells use two half-cells with different electrolytes. In that case each
half-cell is enclosed in a container, and a separator that is porous to ions but not the bulk
of the electrolytes prevents mixing.
Each half cell has an electromotive force (or emf ), determined by its ability to drive
electric current from the interior to the exterior of the cell. The net emf of the cell is the
difference between the emfs of its half-cells, as first recognized by Volta. In other words, if
the electrodes have emfs, the net emf is the difference between the reduction potentials
of the half-reactions.
The electrical driving force or across the terminals of a cell is known as the terminal
voltage (difference) and is measured in volts. The terminal voltage of a cell that is neither
charging nor discharging is called the open-circuit voltage and equals the emf of the
cell. Because of internal resistance, the terminal voltage of a cell that is discharging is
smaller in magnitude than the open-circuit voltage and the terminal voltage of a cell
that is charging exceeds the open-circuit voltage. An ideal cell has negligible internal
resistance, so it would maintain a constant terminal voltage of until exhausted, then
dropping to zero. If such a cell maintained 1.5 volts and stored a charge of one Coulomb
then on complete discharge it would perform 1.5 Joule of work. In actual cells, the internal
resistance increases under discharge, and the open circuit voltage also decreases under
22
discharge. If the voltage and resistance are plotted against time, the resulting graphs
typically are a curve; the shape of the curve varies according to the chemistry and internal
arrangement employed.
As stated above, the voltage developed across a cell's terminals depends on the energy
release of the chemical reactions of its electrodes and electrolyte. Alkaline and carbonzinc cells have different chemistries but approximately the same emf of 1.5 volts; likewise
NiCd and NiMH cells have different chemistries, but approximately the same emf of 1.2
volts. On the other hand the high electrochemical potential changes in the reactions of
lithium compounds give lithium cells emfs of 3 volts or more.
3.7 Breadboard
A breadboard (protoboard) is a construction base
for a one-of-a-kind electronic circuit, a prototype.
In modern times the term is commonly used to refer
to a particular type of breadboard, the solderless
breadboard (plug board).
Because the solderless breadboard does not require
soldering, it is reusable, and thus can be used for
temporary prototypes and experimenting with circuit
design more easily. Other, often historic, breadboard
types don't have this property. This is also in contrast
to stripboard (veroboard) and similar prototyping
printed circuit boards, which are used to build more
permanent soldered prototypes or one-offs, and cannot
easily be reused. A variety of electronic systems may be
prototyped by using breadboards, from small analog
and digital circuits to complete central processing
units (CPUs).
3.7.1 Typical specifications
A modern solderless breadboard consists of a perforated block of plastic with numerous
tin plated phosphor bronze or nickel silver alloy spring clips under the perforations. The
spacing between the clips (lead pitch) is typically 0.1" (2.54 mm). Integrated circuits
(ICs) in dual in-line packages (DIPs) can be inserted to straddle the centerline of the
block. Interconnecting wires and the leads of discrete components (such as capacitors,
resistors, inductors, etc.) can be inserted into the remaining free holes to complete the
circuit. Where ICs are not used, discrete components and connecting wires may use any
of the holes. Typically the spring clips are rated for 1 Ampere at 5 Volts and 0.333 Amperes
at 15 Volts (5 Watts).
23
3.7.2 Bus and terminal strips
Logical 4-bits adder where sums are linked to LEDs
on a typical breadboard
Example breadboard drawing. Two bus strips and
one terminal strip in one block. 25 consecutive
terminals in a bus strip connected (indicated by
gaps in the red and blue lines). Four binding posts
depicted at the top.
Close-up of a solderless breadboard. (An IC straddling
the centerline is probed with an oscilloscope.)
Solderless breadboards are available from several
different manufacturers, but most of them share
a similar layout. The layout of a typical solderless
breadboard is made up from two types of areas,
called strips. Strips consist of interconnected
electrical terminals.
3.7.3 Terminal strips
This is the main area, which is used to hold most of the electronic components.
In the middle of a terminal strip of a breadboard, one typically finds a notch running
in parallel to the long side. The notch is to mark the centerline of the terminal strip and
provides limited airflow (cooling) to DIP ICs straddling the centerline. The clips on the
right and left of the notch are each connected in a radial way; typically five clips (i.e.,
beneath five holes) in a row on each side of the notch are electrically connected. The five
clip columns on the left of the notch are often marked as A, B, C, D, and E, while the ones
on the right are marked F, G, H, I and J. When a "skinny" Dual Inline Pin package (DIP)
integrated circuit (such as a typical DIP-14 or DIP-16, which have a 0.3 inch separation
between the pin rows) is plugged into a breadboard, the pins of one side of the chip are
supposed to go into column E while the pins of the other side go into column F on the
other side of the notch.
3.7.4 Bus strips
This is used to provide power to the electronic components.
A bus strip usually contains two columns, one for ground, and one for a supply voltage.
But some breadboards only provide a single-column power distributions bus strip on
each long side. Typically the column intended for a supply voltage is marked in red,
while the column for ground is marked in blue or black. Some manufacturers connect
all terminals in a column. Others just connect groups of e.g. 25 consecutive terminals
24
in a column. The latter design provides a circuit designer with some more control over
crosstalk (inductively coupled noise) on the power supply bus. Often the groups in a bus
strip are indicated by gaps in the color marking.
Bus strips typically run down one or both sides of a terminal strip or between terminal
strips. On large breadboards additional bus strips can often be found on the top and
bottom of terminal strips.
Some manufacturers provide separate bus and terminal strips. Others just provide
breadboard blocks which contain both in one block. Often breadboard strips or blocks
of one brand can be clipped together to make a larger breadboard.
In a more robust and slightly easier to handle variant, one or more breadboard strips
are mounted on a sheet of metal. Typically, that backing sheet also holds a number of
binding posts. These posts provide a clean way to connect an external power supply.
Several images in this article show such solderless breadboards.
3.7.5 Diagram
A "full size" terminal breadboard strip typically consists of around 56 to 65 rows of
connectors, each row containing the above mentioned two sets of connected clips (A to
E and F to J). "Small size" strips typically come with around 30 rows.
3.7.6 Terminal Strip
ABCDE FGHIJ
1 o-o-o-o-o v o-o-o-o-o
2 o-o-o-o-o o-o-o-o-o
~
~
63 o-o-o-o-o ^ o-o-o-o-o
3.7.7 Bus Strip
VG
oo
||
oo
||
oo
||
oo
25
||
oo
||
||
oo
||
oo
||
oo
||
oo
||
oo
||
||
~
~
oo
||
oo
3.8 Series Parallel Connection of Solar Panel and the Effect of
Shading:
In electrical circuits series and parallel are two basic
ways of wiring components. The naming comes after
the method of attaching components, i.e. one after
the other, or next to each other. As a demonstration,
we have shown both series and parallel connections
of the panels.
A
Solar
Panel
Solar
Panel
V
Solar
Panel
Solar
Panel
Series
A
A
Solar
Panel
Solar
Panel
V
Solar
Panel
Solar
Panel
Solar
Panel
Solar
Panel
Solar
Panel
V
Solar
Panel
Parallel
26
Two in series & two in parallel
Unit 4: PV Devices in India
Time: 3 hours
Method: Demonstration, presentation
4.1 Introduction
PV modules in India
PV modules are usually made from strings of crystalline silicon solar cells. These cells are
made of extremely thin silicon wafers (about 300 µm) and hence are extremely fragile.
To protect the cells from damage, a string of cells is hermetically sealed between a layer
of toughened glass and layers of ethyl vinyl acetate (EVA). An insulating tedlar sheet is
placed beneath the EVA layers to give further protection to the cell string. An outer frame
is attached to give strength to the module and to enable easy mounting on structures.
A terminal box is attached to the back of a module; here, the two ends (positive and
negative) of the solar string are welded or soldered to the terminals. This entire assembly
constitutes a PV module. When the PV module is in use, the terminals are connected
either directly to a load, or to another module to form an array. Single PV modules
of capacities ranging from 3 Wattpeak (Wp) to 240 Wattpeak (Wp) can provide power
for different loads. For large power applications, a PV array consisting of a number of
modules connected in parallel and/or series is used.
4.1.1 Standard Capacity/Ratings and Specifications
The wattage output of a PV module is rated in terms of wattpeak (Wp) units. The peak
watt output power from a module is defined as the maximum power output that the
module could deliver under standard test conditions (STC). The STC conditions used in
a laboratory are



1000 watts per square metre solar radiation intensity
Air-mass 1.5 reference spectral distribution
25 °C ambient temperature.
SPV modules of various capacities are available, and are being used for a variety of
applications. Theoretically, a PV module of any capacity (voltage and current) rating can
be fabricated. However, the standard capacities available in the country range from 3
Wattpeak (Wp) to 240 Wattpeak (Wp). The voltage output of a PV module depends on
the number of solar cells connected in series inside the module. In India, a crystalline
silicon module generally contains 36 solar cells connected in series. The module provides
27
a usable direct current (DC) voltage of about 16.5 V, which is normally used to charge a
12-V battery.
In an SPV system, the components other than the PV module are collectively known as
‘balance of system’ (BoS), which includes batteries for storage of electricity, electronic
charge controller, inverter, etc. These batteries are charged during the daytime using the
DC power generated by the SPV module. The battery/battery bank supplies power to
loads during the night or non-sunny hours. An inverter is required to convert the DC
power from the PV module or battery to AC power for operating the load. Some loads
such as DC pumps do not require an inverter or even a battery bank.
4.2 Compact Fluorescent Lamps
Compact fluorescent lamps (CFLs) combine the energy efficiency of fluorescent
lighting with the convenience and popularity of incandescent fixtures. CFLs can replace
incandescents that are roughly 3–4 times their wattage, saving up to 75% of the initial
lighting energy. Although CFLs cost 3–10 times more than comparable incandescent
bulbs, they last 6–15 times as long (6,000–15,000 hours). See How CFLs Compare with
Incandescents for more information.
4.2.1 How They Work
CFLs work much like standard fluorescent lamps. They consist of two parts: a gas-filled tube,
and magnetic or electronic ballast. The gas in the tube glows with ultraviolet light when
electricity from the ballast flows through it. This in turn excites a white phosphor coating on
the inside of the tube, which emits visible light throughout the surface of the tube.
CFLs with magnetic ballasts flicker slightly when they start. They are also heavier than
those with electronic ballasts. This may make them too heavy for some light fixtures.
Electronic ballasts are more expensive, but light immediately (especially at low
temperatures). They are also more efficient than magnetic ballasts. The tubes will last
about 10,000 hours and the ballast about 50,000 hours. Most currently available CFLs
have electronic ballasts.
CFLs are designed to operate within a specific temperature range. Temperatures below
the range cause reduced output. Most are for indoor use, but there are models available
for outdoor use. You can find a CFL's temperature range on most lamp packages. You
should install outdoor CFLs in enclosed fixtures to minimize the adverse effects of colder
temperatures.
CFLs are most cost effective and efficient in areas where lights are on for long periods
of time. You'll experience a slower payback in areas where lights are turned on for short
periods of time, such as in closets and pantries. Because CFLs do not need to be changed
often, they are ideal for hard-to-reach areas.
28
4.2.2 Types of Compact Fluorescent Lamps
CFLs are available in a variety of styles or shapes. Some have two, four, or six tubes.
Others have circular or spiral-shaped tubes. The size or total surface area of the tube(s)
determines how much light it produces.
Some CFLs have the tubes and ballast permanently connected. Other CFLs have
separate tubes and ballasts. This allows you to change the tubes without changing the
ballast. There are also types enclosed in a glass globe. These look somewhat similar to
conventional incandescent light bulbs, except they're larger.
Sub-CFLs fit most fixtures designed for
incandescent lamps. Although most CFLs fit into
existing 3-way light sockets, only a few special
CFL models can be dimmed.
Compact fluorescent lamps (CFLs) come in a
variety of sizes and shapes including (a) twintube integral, (b and c) triple-tube integral, (d)
integral model with casing that reduces glare,
(e) modular circline and ballast, and (f ) modular
quad-tube and ballast. CFLs can be installed
in regular incandescent fixtures, and they
consume less than one-third as much electricity
as incandescent lamps do.
Compact Fluorescent Lamps
d
a
b
e
c
f
4.3 Specifications for Solar Photovoltaic Systems
(CFL Based)
# The following specifications have been issued by Ministry of New and Renewable
Energy.
4.3.1 Solar Home Lighting Systems
I. Definition
A solar home lighting system aims at providing solar electricity for operating lights
and/or fan or energizing a DC operated portable TV set for specified hours of operation
per day.
II. Models
MODEL – 1 (1 Light Point)
Component Specifications
PV Module 1X 18 W under STC
Lamps 1X CFL (9W /11W)
Battery 1X 12V, 20 AH Tubular plate Lead Acid or VRLA Gel Type
29
Other components: control electronics, module mounting hardware, and battery box,
inter-connecting wires / cables, switches, Operation, instruction and maintenance
manual.
MODEL - 2 (2 Lights)
PV Module 1X 37 W under STC
Lamps 2X CFLs (9W /11W)
Battery 1X 12V, 40 AH Tubular plate Lead Acid or VRLA Gel Type
manual.
MODEL - 3 (2 lights and 1 fan)
PV Module(s) 2X 37 W or 1 X 74 W under STC
Lamps 2X CFLs (9W /11W)
Fan 1X DC Fan (with wattage less than 20 W)
Battery 1X 12V, 75 AH Tubular Plate Lead Acid or VRLA GEL Type
manual.
MODEL - 4 (4 lights)
PV Module(s) 2X 37 W or 1 X 74 W under STC
Lamps 4 X CFLs (9W /11W)
Battery 1X 12V, 75 AH Tubular Plate Lead Acid or VRLA Gel Type
manual.
Notes:
i)
ii)
30
All models will have a socket to provide power for a 12V DC TV set which can be
purchased separately.
A small white LED may be provided as an optional feature, with an independent
switch.
III. DUTY CYCLE
The system should be designed under average daily insolation of 5.5 kWh/ sq.m. on a
horizontal surface.
MODELS AVERAGE HOURS OF OPERATION / DAY
Model 1: 1 Light, (3-4 Hours)
Model 2: 2 Lights, (3-4 Hours)
Model 3: 2 Lights, (2-3 hours), 1 Fan (2-3 hours)
Model 4: 4 Lights, (3-4 Hours)
IV. LAMPS
(i) The lamps will be of compact fluorescent (CFL) type, 4 - Pin type, with ratings of 9W
or 11W with a suitable pre-heating circuit.
(ii) The light output from the lamps should be around 550 +/- 5 % lumens (for 9 W CFL)
and 850 +/- 5 % lumens (for 11 W CFL). Also please see (iii) of VI given below.
(iii) The lamps should be housed in an assembly suitable for indoor use, with a reflector
on its back. While fixing the assembly, the lamp should be held in a base up
configuration.
V. BATTERY
(i) The battery will be of flooded electrolyte, positive tubular plate type, low maintenance
lead acid or gel type VRLA.
(ii) The battery will have a minimum rating of 12V, 20 or 40 or 75 Ah (at C/10) discharge
rate depending on Model.
(iii) 75 % of the rated capacity of the battery should be between fully charged & load cut
off conditions.
VI. ELECTRONICS
(i) The inverter should be of quasi sine wave/sine wave type; with frequency in the
range of 20 - 30 KHz. Half-wave operation is not acceptable.
(ii) The total electronic efficiency should be not less than 80 %.
(iii) No blackening or reduction in the lumen output by more than 10% should be
observed after 1000 ON/OFF cycles (two minutes ON followed by four minutes OFF
is one cycle).
(iv) The idle current consumption should not be more than 10 mA
VII. PV MODULE (S)
(a) The PV module (s) shall contain mono/ multi crystalline silicon solar cells. It is
preferable to have certificate for the supplied PV module as per IEC 61215(revised)
specifications or equivalent National or International Standards. In case if the
supplied PV module is not a regular PV module of the manufacturer and does not have
certificate as per IEC 61215(revised) specifications ,then the manufacturer should
have the required certification for at least one of their regular modules. Further, the
manufacturer should certify that the supplied module is also manufactured using
same material design and process similar to that of certified PV module.
31
(b) The power output of the module(s) under STC should be a minimum of 18 W or 37
W or 74 W. In case of Model 4 & 5 either two modules of 37 W each or one module of
74 W should be used.
(c) The operating voltage corresponding to the power output mentioned above should
be 16.4 V.
(d) The open circuit voltage of the PV modules under STC should be at least 21.0 Volts.
(e) The terminal box on the module should have a provision for opening for replacing
the cable, if required.
(f) A strip containing the following details should be laminated inside the module so as
to be clearly visible from the front side:
g) Name of the Manufacturer or distinctive Logo
h) Model or Type No.
i) Serial No.
j) Year of make
VIII. DC FAN
The wattage of the fan should not be more than 20 Watts and it should operate at 12V
DC.
IX. ELECTRONIC PROTECTIONS
(i) Adequate protection is to be incorporated under no load conditions, e.g. when the
lamps are removed and the system is switched ON.
(ii) The system should have protection against battery overcharge and deep discharge
conditions.
(iii) Fuses should be provided to protect against short circuit conditions.
(iv) A blocking diode should be provided as part of the electronics, to prevent reverse
flow of current through the PV module(s), in case such a diode is not provided with
the PV module(s).
(v) Full protection against open circuit, accidental short circuit and reverse polarity
should be provided.
(vi) Electronics should operate at 12 V and should have temperature compensation for
proper charging of the battery throughout the year.
X. MECHANICAL COMPONENTS
(i) Metallic frame structure (with corrosion resistance paint) to be fixed on the roof of
the house to hold the SPV module(s). The frame structure should have provision to
adjust its angle of inclination to the horizontal between 0 and 45, so that it can be
installed at the specified tilt angle.
(ii) A vented metallic/ plastic box with acid proof corrosion resistance paint for housing
the storage battery indoors should be provided.
XI OTHER FEATURES
(i) The system should be provided with 2 LED indicators: a green light to indicate
charging in progress and a red LED to indicate deep discharge condition of the battery.
The green LED should glow only when the battery is actually being charged.
32
(ii) There will be a Name Plate on the system which will give:
(a) Name of the Manufacturer or Distinctive Logo.
(b) Serial Number.
(iii) Components and parts used in solar home systems should conform to the latest BIS
specifications, wherever such specifications are available and applicable.
(iv) PV module(s) will be warranted for a minimum period of 15 years from the date
of supply and the solar home system (including the battery) will be warranted for
a period of two years from the date of supply. The Warranty Card to be supplied
with the system must contain the details of the system supplied, as given in the
Annexure-12. The manufacturers can also provide additional information about the
system and conditions of warranty as necessary.
4.3.2 Solar Street Lighting System
I. DEFINITION
A stand alone solar photovoltaic street lighting system comprises a compact fluorescent
lamp, lead acid battery, PV module(s), control electronics, inter-connecting wires/cables,
module mounting hardware, battery box, Operation, instruction and maintenance
manual.
II. DUTY CYCLE
The system should be designed to automatically switch ON at dusk, operate throughout
the night and automatically switch OFF at the down, under average daily insolation of
5.5 kWh/ sq.m. on a horizontal surface.
III. LAMP
(i) The lamp will be of compact fluorescent (CFL) of 11W, 4 - Pin type with adequate
pre-heating circuit.
(ii) The light output from the lamp should be around 850 +/- 5 % lumens. Also please
see (iii) of V given below.
(iii) The lamp should be housed in a weather proof assembly suitable for outdoor use,
with a reflector on its back. While fixing the assembly, the lamp should be held in a
base up configuration.
IV. BATTERY
(i) Flooded electrolyte type, positive tubular plate, low maintenance lead acid or gel
type VRLA
(ii) The battery will have a minimum rating of 12V, 75 Ah (at C/10) discharge rate.
(iii) 75 % of the rated capacity of the battery should be between fully charged & load cut
off conditions.
V. ELECTRONICS
(i) The inverter should be of quasi sine wave/ sine wave type, with frequency in the
range of 20 - 30 KHz. Half-wave operation is not acceptable.
(ii) The total electronic efficiency should be not less than 80 %.
33
(iii) No blackening or reduction in the lumen output by more than 10% should be
observed after 1000 ON/OFF cycles (two minutes ON followed by four minutes OFF
is one cycle).
(iv) The idle current consumption should not be more than 10 mA.
(v) The PV module itself will be used to sense the ambient light level for switching ON
and OFF the lamp.
VI. PV MODULE (S)
(i) The PV module (s) shall contain mono/ multi crystalline silicon solar cells. It is
preferable to have certificate for the supplied PV module as per IEC 61215(revised)
specifications or equivalent National or International Standards. In case if the
supplied PV module is not a regular PV module of the manufacturer and does not have
certificate as per IEC 61215(revised) specifications ,then the manufacturer should
have the required certification for at least one of their regular modules. Further, the
manufacturer should certify that the supplied module is also manufactured using
same material design and process similar to that of certified PV module
(ii) The power output of the module(s) under STC should be a minimum of 74 W. Either
two modules of minimum 37 W output each or one module of 74 W output should
be used.
(iii) The operating voltage corresponding to the power output mentioned above should
be 16.4 V.
(iv) The open circuit voltage of the PV modules under STC should be at least 21.0 Volts.
(v) The terminal box on the module should have a provision for opening for replacing
(vi) A strip containing the following details should be laminated inside the module so as
a) Name of the Manufacturer or distinctive Logo
b) Model or Type No.
c) Serial No.
d) Year of make
VII. ELECTRONIC PROTECTIONS
(i) Adequate protection is to be incorporated under no load conditions e.g. when the
lamp is removed and the system is switched ON.
(ii) The system should have protection against battery overcharge and deep discharge
conditions.
(iii) Fuses should be provided to protect against short circuit conditions.
(iv) A blocking diode should be provided as part of the electronics, to prevent reverse
the solar module(s).
(v) Full protection against open circuit, accidental short circuit and reverse polarity
should be provided.
(vi) Electronics should operate at 12 V and should have temperature compensation for
proper charging of the battery throughout the year.
34
VIII MECHANICAL HARDWARE
(i) A metallic frame structure (with corrosion resistance paint) to be fixed on the pole
to hold the SPV module(s). The frame structure should have provision to adjust its
angle of inclination to the horizontal between 0 and 45, so that the module(s) can be
oriented at the specified tilt angle.
(ii) The pole should be made of mild steel pipe with a height of 4 metres above the ground
level, after grouting and final installation. The pole should have the provision to
hold the weather proof lamp housing. It should be painted with a corrosion resistant
paint.
(iii) A vented, acid proof and corrosion resistant painted metallic box for outdoor use
should be provided for housing the battery.
IX. OTHER FEATURES
(ii) There will be a Name Plate on the system, which will give:
(b) Serial Number.
(iii) Components and parts used in the solar street lighting systems should conform to the
latest BIS specifications, wherever such specifications are available and applicable.
(iv) The PV module(s) will be warranted for a minimum period of 15 years from the date
of supply and the street lighting system (including the battery) will be warranted for
a period of two years from the date of supply.
The Warranty Card to be supplied with the system must contain the details of the
system. The manufacturers can also provide additional information about the
system and conditions of warranty as necessary.
(v) Necessary lengths of wires/cables and fuses should be provided
(vi) An Operation, Instruction and Maintenance Manual, in English and the local
language, should be provided with the solar street lighting system.
The following minimum details must be provided in the Manual:
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
(j)
(h)
About Photovoltaic
About solar home system - its components and expected performance
About PV module.
About CFL.
About battery.
Clear instructions about mounting of PV module(s).
About electronics.
About charging and significance of indicators.
DO's and DONT's,
Clear instructions on regular maintenance and trouble shooting of solar home system.
Name and address of the person or service center to be contacted in case of failure
or complaint.
35
4.4 Specifications for LED based solar lighting systems
4.4.1 White LED Based Solar Home Lighting Systems
DEFINITION
Light Emitting Diode (LED) is a device which emits light when an electric current passes
through it. A LED based solar home lighting system aims at providing solar electricity for
operating LED lights and / or other small DC loads for specified hours of operation per
day.
The broad performance specifications of a Light Emitting Diode (LED) light source based
solar home lighting system are given below.
BROAD PERFORMANCE PARAMETERS
Light Source: White Light Emitting Diode (W-LED)
Light Out put: White colour, minimum 15 lux when measured from a height of about 2.5
metre and illuminated over an area of at least 2.5 metre diameter. Higher light output will
be referred. Soothing to eyes
Negative
electrode
n doped
silicon
Mounting of light: Wall or ceiling
Electronics: Min 80% total efficiency
Average duty cycle: 4 hours a day
Autonomy: 3 days (Minimum 12 operating
hours per permissible discharge)
Positive
electrode
Boundary
layer
p doped
silicon
There will be two models of home lighting systems. The Model-I will have one WLED
light source and the Model-II will have two light sources. Each light source providing
above stated light output of 15 lux. The requirement of PV module and battery will be as
per the following details.
MODELS
Model I
PV Module: 8 Wp under STC, measured at 16.4 V as Vload
Module Voc minimum of 21 V
Battery Sealed maintenance free, 12 V- 7 AH @ C/20, Max DoD 75%
Model II
PV Module: 12 Wp under STC, measured at 16.4 V as Vload
36
Battery: Lead acid flooded or VRLA, 12 V- 20 AH @ C/10, Max DoD 75%
Other Details
DUTY CYCLE
The LED solar home lighting system should be designed to operate for average 4 hours a
day, under average daily insolation of 5.5 kWh /sq.m. on a horizontal surface.
LIGHT SOURCE
(i) The light source will be of white LED type. Single lamp or multiple lamps can be
used. View angles of a minimum of 1200 and above will be referred. The luminous
performance of LEDs used should not be less than 55 lumen/watt. The colour
temperature of white LEDs used in the system should be in the range of 5500o K
– 6500o K. Use of LEDs which emit ultraviolet light is not permitted.
(ii) The light output from the white LED light source should be constant through out the
duty cycle.
(iii) The lamps should be housed in an assembly suitable for indoor use.
(iv) The make, model number, country of origin and technical characteristics of white
LEDs used in the lighting system must be furnished to the test centers and to
the buyers. In absence of this data the solar lantern may not be tested by the test
center.
BATTERY
(i) Battery should conform to latest BIS standards or international standards. A copy of
the test certificate for the battery (including its make, country of origin and model
number) used in the system should be provided to the test center.
(ii) At least 75 % of the rated capacity of the battery should be between fully charged &
load cut off conditions.
ELECTRONICS
(i) The total electronic efficiency should be at least 80 %.
(ii) Electronics should operate at 12 V and should have temperature compensation for
proper charging of the battery through out the year.
(iii) The light output should remain constant with variations in the battery voltages.
(iv) Necessary lengths of wires / cables, switches suitable for DC use and fuses should be
provided.
PV MODULE
(a) The PV module based on crystalline (single or multi) silicon solar cells or thin films
may be used. In all cases a test report is required from authorized test center. The
PV module must be manufactured by a company, which has obtained a valid test
certificate for module qualification as per prevailing IEC 62125 or BIS standards for
any of the modules manufactured by that company. A copy of the IEC certificate
must be submitted to the test agency at the time of submission of the samples for
testing, failing which the sample may not be tested.
37
(b) The power out put of the PV module must be reported under standard test
conditions (STC) at 16.4 Volt loading voltage. I_V curve of the sample module should
be submitted to the test center at the time of system qualification testing.
(c) The open circuit voltage of the PV modules under STC should be at least 21.0 Volts.
(d) The terminal box on the module should have a provision for opening for replacing
(e) A strip containing the following details should be laminated inside the module
so
as to be clearly visible from the front side:
c) Serial No.
d) Year of make
QUALITY AND WARRANTY
(i) Components and parts used in White LED based solar home lighting systems should
conform to the latest BIS / international specifications, wherever such specifications
are available and applicable. A copy of the test report / certificate stating conformity
of BIS / international standards must be submitted to the test centre.
(ii) The PV module will be warranted for a minimum period of 15 years from the
date of supply and the White LED solar home system (excluding the battery) will
be warranted for a period of at least 5 years from the date of supply. The sealed
maintenance free battery should be warranted for a period of at least two year. The
lead acid flooded type battery or VRLA battery should be warranted for a period of 5
years.
4.4.2 White LED Based Solar Lantern System
DEFINITION
Light Emitting Diode (LED) is a device which emits
light when an electric current passes through it. A Solar
lantern) is a lighting system consisting of a lamp, battery
and electronics, all placed in a suitable housing, made
of metal, plastic or fiber glass, and a PV module. The
battery is charged by electricity generated through the
PV module. The lantern is basically a portable lighting
device suitable for either indoor or outdoor lighting,
covering a full range of 360 degrees. A LED based solar
lantern system aims at providing solar electricity for
operating LED lights for specified hours of operation per day.
The broad performance specifications of a white Light Emitting Diode (LED) light source
based solar lantern system are given below.
Light Source: White Light Emitting Diode (W-LED), dispersed, soothing to eyes
38
Light Out put: Minimum level of illuminance from WLED lantern
S.No
Distance
When detector is in
horizontal to center
point of bottom of light
source
When detector is at
right angle to the center
point of bottom of light
source
1
1 feet
32 Lux
105 Lux
2
2 feet
6.5 Lux
32 Lux
3
3 feet
3 Lux
16 Lux
4
4 feet
2 Lux
9.5 Lux
5
5 feet
1.5 Lux
6.5 Lux
Mounting of light: Top or base mounted
PV Module: between 2.5 to 5 Wp under STC
Battery: Lead acid Sealed maintenance free or Ni MH or Lithium Ion, with a capacity
upto - 7 AH, at voltages up to 12 V @ C/20, Max DoD 75% or equivalent capacity
Average duty cycle: 4 hours a day
Autonomy: Minimum of 3 days (Minimum 14 operating hours per permissible
discharge)
It should be possible to charge the WLED solar lanterns through a central charging station
also. For central charging the battery capacity may be for a maximum of 8 hours and the
design battery voltage may be specified.
Other Details
DUTY CYCLE
The LED solar lantern system should be designed to operate for average 4 hours a day,
under average daily insolation of 5.5 kWh /sq.m. on a horizontal surface.
LIGHT SOURCE
The light source will be of white LED type. Single lamp or multiple lamps can be used.
Wider view angles preferred. The luminous performance of LEDs used should not be
less than 55 lumen/watt. White colour, higher light output will be preferred. The colour
temperature of white LEDs used in the system should be in the range of 5500o K – 6500o
K. Use of LEDs which emit ultraviolet light is not permitted.

The light output from the white LED light source should be constant though out the
ty cycle.
39


The lamps should be housed in an assembly suitable for indoor and outdoor use.
The make, model number, country of origin and technical characteristics of white
LEDs used in the lighting system must be furnished to the test centers and to
the buyers. In absence of this data the solar lantern may not be tested by the test
center.
BATTERY
(i) Sealed maintenance free battery. Battery should conform to latest BIS standards or
international standards. A copy of the test certificate for the battery (including its
make, country of origin and model number) used in the system should be provided
to the test center and buyer.
ELECTRONICS
(ii) Electronics should operate at 4.5/6/12 V and should have temperature compensation
for proper charging of the battery through out the year.
(iv) The light output should remain constant with variations in the battery voltages.
(v) Necessary lengths of wires / cables, switches suitable for DC use and fuses should be
provided.
PV MODULE

The PV modules based on crystalline silicon solar cells or thin films may be used. In
all cases a test report is required from authorized test center.

The power out put of the PV module must be reported under standard test conditions
(STC) at loading voltage. I_V curve of the sample module should be submitted to the
test center at the time of system qualification testing.

The open circuit voltage of the PV modules under STC should be at least ….. Volts.

The terminal box on the module should have a provision for opening for replacing

A strip containing the following details should be laminated inside the module so as
c) Serial No.
d) Year of make
ELECTRONIC PROTECTIONS

Adequate protection is to be incorporated under no load conditions, e.g. when the
lamps are removed and the system is switched ON.

The system should have protection against battery overcharge and deep discharge
conditions. The numerical values of the cut off limits must be specified, while
submitting the samples for the testing purposes.

Fuses should be provided to protect against short circuit conditions.
40


A blocking diode should be provided as part of the electronics, to prevent reverse
the PV module.
Full protection against open circuit, accidental short circuit and reverse polarity
should be provided.
OTHER FEATURES
(ii) There will be a Name Plate on the system body which will give:
 Name of the Manufacturer or Distinctive Logo.
 Model Number
 Serial Number
 Year of manufacture
(ii) Components and parts used in White LED solar home lighting systems should
of BIS / international standards must be submitted to the test centre.
(iii) The PV module will be warranted for a minimum period of 15 years from the date
of supply and the White LED solar lantern system (excluding the battery) will be
warranted for a period of at least 5 years from the date of supply. The battery should
be warranted for a period of at least two years.
4.4.3 White LED Based Solar Street Lighting Systems
DEFINITION
Light Emitting Diode (LED) is a device which emits light
when an electric current passes through it. An LED based
solar street lighting system aims at providing solar electricity
for operating LED lights for specified hours of operation
per day.
The broad performance specifications of a White Light
Emitting Diode (LED) light source based solar street lighting
system are given below.
Light Source: White Light Emitting Diode (W-LED)
Light Out put: White colour, minimum 15 lux when measured from a height of about 4
metre and illuminated over an area of at least 4 metre diameter. Higher light output will
be preferred.
41
Mounting of light: Minimum 4 metre pole Mounted
PV Module: 40 Wp under STC, measured at 16.4 V - Vload
Battery: Tubular Lead acid, 12 V- 40 AH @ C/10, Max DoD 75%
Average duty cycle: Dusk to dawn
Autonomy: 3 days (Minimum 42 operating hours per permissible discharge)
Other Details
DUTY CYCLE
The LED solar street lighting system should be designed to operate for dust to dawn,
under average daily insolation of 5.5 kWh /sq.m. on a horizontal surface.
LIGHT SOURCE
1. The light source will be of white LED type. Single lamp or multiple lamps can be
used. Wider view angles of a minimum of 120o and above preferred. The luminous
performance of LEDs used should not be less than 55 lumen/watt. The colour
temperature of white LEDs used in the system should be in the range of 5500o K
– 6500o K. Use of LEDs which emit ultraviolet light is not permitted.
2. The light output from the white LED light source should be constant through out the
duty cycle.
3. The lamps should be housed in an assembly suitable for outdoor use.
4. The make, model number, country of origin and technical characteristics of white
LEDs used in the lighting system must be furnished to the test centers and to the
buyers. In absence of this data the solar lantern may not be tested by the test center.
BATTERY
(i) Tubular Lead acid battery. Battery should conform to latest BIS standards or
international standards. A copy of the test certificate for the battery (including its
make, country of origin and model number) used in the system should be provided
to the test centre.
ELECTRONICS
(ii) Electronics should operate at 12 V and should have temperature compensation for
proper charging of the battery through out the year.
(iii) The light output should remain constant with variations in the battery voltages.
(iv) Necessary lengths of wires / cables, switches suitable for DC use and fuses should be
provided.
42
PV MODULE
1. The PV modules based on crystalline silicon (single or multi) solar cells or thin
films may be used. In all cases a test report is required from authorized test center.
The module must be manufactured by a company, which has obtained a valid test
certificate for module qualification as per prevailing IEC or BIS standards for any of
the modules manufactured by that company. A copy of the IEC certificate must be
submitted to the test agency at the time of submission of the samples for testing of
the system, failing which the sample may not be tested.
2. The power out put of the PV module must be reported under standard test
conditions (STC) at 16.4 Volt loading voltage. I_V curve of the sample module should
be submitted to the test center at the time of system qualification testing.
3. The open circuit voltage of the PV modules under STC should be at least 21.0 Volts.
4. The terminal box on the module should have a provision for opening for replacing
5. A strip containing the following details should be laminated inside the module so as
c) Serial No.
d) Year of make
ELECTRONIC PROTECTIONS
1. The system should have protection against battery overcharge and deep discharge
conditions. The numerical values of the cut off limits must be specified, while
submitting the samples for the testing purposes.
2. Fuses should be provided to protect against short circuit conditions.
3. A blocking diode should be provided as part of the electronics, to prevent reverse
the PV module.
4. Full protection against open circuit, accidental short circuit and reverse polarity
should be provided.
MECHANICAL COMPONENTS
(i) Metallic frame structure (with corrosion resistance paint) to be fixed on the roof of
the house to hold the SPV module. The frame structure should have provision to
adjust its angle of inclination to the horizontal between 0 and 45, so that it can be
installed at the specified tilt angle.
(ii) It should be possible to mount the light source on a metallic arm attached to the
pole. The metallic arm for holding the light assembly should be extended at least 1.5
metres from the pole and set at a suitable angle to maximize uniform illumination
of desired level over the specified area.
(Iii) A vented metallic / plastic box with acid proof corrosion resistance paint for housing
the storage battery outdoors should be provided.
43
OTHER FEATURES
(ii) There will be a Name Plate on the system body which will give:
(b) Model Number
(c) Serial Number
(d) Year of manufacture
(i) Components and parts used in White LED solar street lighting systems should
of BIS /international standards must be submitted to the test centre.
(ii) The PV module will be warranted for a minimum period of 15 years from the date
of supply and the complete White LED solar street lighting system (including the
battery) will be warranted for a period of at least 5 years from the date of supply.
(iii) The original manufacturers of white LED based solar home lighting system are
required to provide to the test center a detailed report on the tests performance
by them and the actually measured values of PV module, electronics, LEDs and
battery and other related parameters, as per MNRE specifications. Mere mention of
compliance to MNRE specifications is not acceptable and such samples may not be
tested by the Test center. The test center will refer to the measured values provided
by the manufacturer in the test report issued by the test center.
44
Unit 5: Maintenance and Troubleshooting
Time: 1 hour
Method: demonstration, presentation
5.1 Routine Maintenance
A solar electric system that is properly maintained requires very little maintenance. In fact
the work involved in maintaining a solar electric system is much less than that required
to maintain a diesel or petrol powered generator. The best maintenance practice is to
make regular inspections of the equipment (especially the batteries and modules), to
make sure that things are kept clean and all electrical contacts are tight.
5.1.1 Battery maintenance
Batteries require regular and careful maintenance. For a longer life batteries should:



Be cleaned monthly
Have their electrolyte level checked
Be kept in a high state of charge
5.1.2 Cleaning (once a month)
Carry the battery outside when cleaning to avoid spilling of acid. Keep water nearby to
rinse spills.






Turn off or disconnect the solar charge
Disconnect the battery from the leads and remove the terminals from the posts.
Clean the top and outside of the battery with water (do not allow water to enter
the cells)
Clean the terminals and the posts until they are shiny. If the terminals are corroded
(i.e. they are covered with a white power) clean them carefully with a solution of
baking powder and water. If the terminals are badly corroded then replace them.
Replace the cleaned terminals and tighten the bolts. Apply petroleum jelly or grease
to the connected terminals.
If unable to open the tight bolts, place wet cloth over it for 2-3 hours and then
open it.
45
5.1.3 Checking and Topping up Electrolyte level (monthly)


Remove caps of each of the cells one at a time and check the level of electrolyte. Acid
level should be within two centimeters of the top battery. If you can look inside the
battery, check the plates to see their condition
If the electrolyte level is down, add ionized distilled water till it is about two
centimeters below the top of the battery.
DO NOT ADD RAINWATER COLLECTED IN METAL CONTAINERS
DO NOT ADD ACID, TAP WATER OR TONICS TO THE BATTERY
5.1.4 Checking the state of Charge


BE CAREFUL NOT TO USE LOW CHARGED BATTERIES
If the battery is in the state of low charge, reduce the use of load and allow the battery
to be charged by a module
With large systems (schools, hospitals) keep records of the battery, state of charge,
age and performance. This allows users to judge more easily whether a battery needs
replacement.
5.1.5 Equalising Charge
An equalizing charge is a hard charge from a grid or generator powered battery charger
that takes a battery a bit above its normal full state. It causes bubbling which mixes up
the acid inside the battery, it also helps remove accumulated sulphate from the battery
during the cloudiest months of the year.
5.1.6 Module Maintenance
Modules require minimum maintenance as they do not have any moving parts. Keeping
the glass surface clean is the most important task. Dust and shade will reduce the electric
output. Clean the module with water and if necessary a mild soap. Do not allow a plant
or a tree to shade the panel
5.1.7 Checking Connections
Inspect the junction box on the back of each panel
to make sure that the wiring is tight. Make sure those
wires have not been chewed by rats and that there
are no insects etc, living in the junction boxes
ELECTRONIC CHARGE CONTROLLER
5.1.8 Wiring and control
If the wiring is installed properly, there should be no wiring problems for the life of
the system. However, it is useful to check the wiring of the system at least once a year,
especially in places where it might be damaged by animals, tampered with or accidently
pulled.
46
5.1.9 Inspecting wiring, fuses, indicator lamps and switches
(annual)






Check the tightness of al connector strips. Make sure that no bare wire is visible
Inspect system wire runs for breaks, cracks in the insulation or places it has been
chewed up. This is especially important for old or exposed wire
Inspect junction boxes to make sure that they have not become homes for insects. If
they are in an exposed location, make sure that they are watertight.
Check the switch. It should not spark while turning ON or OFF.
Check the indicator lamps on the control. The solar charge comes ON when the sun
is up. If it is not On, check to see if the batteries are being charged. Check whether
other LED indicators are working.
Check the grounding wires to make sure that they are all intact.
5.1.10 Lamps and Other Loads




5.2


On a daily basis one should operate the loads as efficiently as possible. Maintenance
of loads includes turning off lights and appliances when not in use.
Clean lamps, reflectors and fixtures once every few months. Dust and dirt will reduce
lamp output by as much as 20%
Check for blackening of tubes in fluorescent fixtures and replace them
Replace burnt out bulbs
Troubleshooting
Troubleshooting means facing problems as they occur. Although if the equipment is
properly installed, systems are unlikely to fail, some problems that need attending
to may arise.
The battery is the most likely source of problem in a small solar electric system
Basic problems:






What was the weather like in the days preceding the problem? Has the weather
been cloudy? Is it likely that the load has been using more energy than the modules
generate? If the latter is the case, then the problem may be due to the misuse of the
system or due to failure of a component
Is the system new? Do the users know about daily maintenance?
What is the condition, type and age of the battery? Can it still hold a charge? If it is
old and corroded change it.
Whether the battery box is properly ventilated and preventing the battery from high
temperature?
Locate all the fuses in the system and see if they have blown. Check and see what
caused the fuse to blow (i.e. short circuit, overload) before replacing it.
Are all the wires connected securely? Are they corroded? Is there any place where a
wire is likely to have broken?
47

Are the modules shaded or dusty?
Lamps or appliances do
not work
One or more lamp or
appliance fails to come On
when connected
48
Lamps
Switch is off
Bad tube or globe
Bad ballast inverter
Bad connection in wire
Tubes or globes have very
short lifetimes
Lamps
Turn switch on
Replace with new
Replace inverter
Repair connection
Check if system voltage is
too high or low
Appliances
Switch is OFF
Bad connection in wire
Bad socket
Broken appliance
Appliances
Turn switch On
Repair
Replace socket
Try appliance where there
is good power supply,
repair or replace
Blown Fuse
When the fuse is removed
the wire inside is broken
Short circuit along were in
module
Fuse too small
Lighting/power surge
Repair short circuit
Use fuse 20% larger than
combined power of load
Replace fuse
Battery Charge is low
“Battery low” indicator
comes on
Low voltage disconnect
turns off load
Battery state of charge is
constantly below 1.5 V
There is no solar charge
Battery acid I low
Bad connection to control
terminal
Defective battery or cell
Loose or corroded battery
terminal
Dusty modules
Blown fuse
Overuse of system
Battery will not accept
charge
Voltage drop between
module and battery high
Defective controller
Check and fix connection
Add dist water to cells
Check for broken wire or
loose contact
Clean and tighten battery
terminals
Clean
Blown fuse section above
Leave appliances Off for a
week to recharging
Find out age and history of
battery
Check voltage drop replace
cable wire if required
Check operation of charge
controller and repair if
required
No Solar Charge
Solar charge indicator does
not light up during day
There is no current from
wires to module
Short circuit along wires to
module
Loose connection in wires
connecting battery to
terminal
Blown fuse
Dust or damage to module
Locate and repair short
circuits
Repair loose connections
Blown fuse section above
Clean module with water
and soft cloth
Check PV module is
facing south and angle
of inclination is equal to
latitude.
Ensure the module is in
shadow free location
49
Unit 6: Practicals
6.1 Tilt angle
To get the most from solar panels, you need to point
them in the direction that captures the most sun.
But there are a number of variables in figuring out
the best direction. This page is designed to help
you find the best placement for your solar panels
in your situation.
This advice applies to any type of panel that gets
energy from the sun; photovoltaic, solar hot water,
etc. We assume that the panel is fixed, or has a tilt
that can be adjusted seasonally. (Panels that track
the movement of the sun throughout the day can
receive 10% (in winter) to 40% (in summer) more
energy than fixed panels. This page doesn't discuss
tracking panels.)
Solar panels should always face true south. (If
you are in the southern hemisphere, they should
face north.) The question is, “At what angle from
horizontal should the panels be tilted?” Books and
articles on solar energy often give the advice that
the tilt should be equal to your latitude, plus 15
degrees in winter or minus 15 degrees in summer.
It turns out that you can do better than this - about
4% better.
Angle of
latitude
Winter
Angle of
latitude
Summer
Solar panels should face due north, Sydney angle of
latitude is 34°.
6.2 Latitude
Latitude, usually denoted by the Greek letter phi
(φ) gives the location of a place on Earth (or other
planetary body) north or south of the equator.
Lines of Latitude are the imaginary horizontal lines
shown running east-to-west (or west to east) on
maps (particularly so in the Mercator projection)
that run either north or south of the equator.
50
Pole star
30 deg
Pole star = 30 deg
elevation.
Your
latitide = 30 deg
Technically, latitude is an angular measurement
in degrees (marked with °) ranging from 0° at the
equator (low latitude) to 90° at the poles (90° N or
+90° for the North Pole and 90° S or −90° for the
South Pole). The latitude is approximately the angle
between straight up at the surface (the zenith) and
the sun at an equinox. The complementary angle of
latitude is called the colatitude.
North Pole
90°N
60°N
60°N
30°N
30°N
90°
30°
0°
90°
0°Equator
60°
30°S
30°S
60°S
60°S
6.2.1 Optimum Tilt for winter
90°S
South Pole
The winter season has the least sun, so you want to make the most of it. To calculate the
best angle of tilt in the winter, take your latitude, multiply by 0.9, and add 29 degrees. The
result is the angle from the horizontal at which the panel should be tilted. This table gives
the angle for some latitudes:
Latitude
Angle
25° (Key West, Taipei)
30° (Houston, Cairo)
35° (Albuquerque, Tokyo)
40° (Denver, Madrid)
45° (Minneapolis, Milano)
50° (Winnipeg, Prague)
% of optimum
51.5°
85%
56°
86%
60.5°
88%
65°
89%
69.5°
91%
74°
93%
These angles are about 10° steeper than what is commonly recommended. The reason
is that in the winter, most of the solar energy comes at midday, so the panel should be
pointed almost directly at the sun at noon.
The third column of the table shows how well this orientation will do compared with the
best possible tracker that always keeps the panel pointed directly at the sun.
6.3 Square Wave
A square wave is a kind of non-sinusoidal
waveform, most typically encountered
in electronics and signal processing. An
ideal square wave alternates regularly and
instantaneously between two levels. Square
waves are universally encountered in digital
switching circuits and are naturally generated
by binary (two-level) logic devices. They are
used as timing references or "clock signals",
because their fast transitions are suitable
for triggering synchronous logic circuits at
Volts
a
–a
51
precisely determined intervals. However, as the frequency-domain graph shows, square
waves contain a wide range of harmonics; these can generate electromagnetic radiation
or pulses of current that interfere with other nearby circuits, causing noise or errors.
To avoid this problem in very sensitive circuits such as precision analog-to-digital
converters, sine waves are used instead of square waves as timing references.
6.4 Sine wave
Practically everything in reality oscillates.
All electromagnetic energy, including
visible light, microwaves, radio waves,
and x-rays, can be represented by a
sine wave. At the lowest level, even
matter oscillates like a wave, but for
macroscopic objects, these oscillations
are so minimal are to be impossible to
measure. Sound waves can be represented as sine waves, and the up-and-down waves
on an oscilloscope may be the most widely known representation of a sine wave. The
study of sine waves and related functions is the most basic kind of higher (post-algebra)
mathematics.
Besides appearing in sound waves, light waves, and ocean waves, the sine wave is also
very important in electronics, as the intensity of an alternating current can be modeled
by a sine wave. The current of a direct current full-wave rectification system, used to
convert AC into DC, can be modeled using an absolute value sine wave, where the wave
is similar to a normal sine wave because the value always stays above the x-axis, with
twice as many peaks as a normal sine wave function. Along with the sine wave is its
cousin, the cosine wave, which is exactly the same except displaced to the right by half
a cycle.
In 1822, French mathematician Joseph Fourier
discovered that any wave could be modeled as
a combination of different types of sine waves.
Solar Irradiance
Module
6.5 Schematic Diagram
Charge
Controller
Inverter
Battery
AC Loads
DC Loads
52
6.6 Inspection of batteries
6.6.1 Safety
We must think safety when we are working around and with batteries. Remove all jewelry.
After all you don't want to melt your watchband while you are wearing the watch. The
hydrogen gas that batteries make when charging is very explosive. We have seen several
instances of batteries blowing up and drenching everything in sulfuric acid. That is no
fun, and would have been a good time to use those safety goggles that are hanging on
the wall. Heck, just break out your disco outfit. Polyester is not affected by Sulfuric Acid,
but anything with cotton will be eaten up. If you do not feel the need to make a fashion
statement, just wear junk clothes, after all Polyester is still out of style. When doing
electrical work on vehicles it is best to disconnect the ground cable. Just remember you
are messing with corrosive acid, explosive gases and 100's amps of electrical current.
6.6.2 Battery Testing
Battery Testing can be done in more than one way. The most accurate method is
measurement of specific gravity and battery voltage. To measure specific gravity buy a
temperature compensating hydrometer, to measure voltage use a digital D.C. Voltmeter.
A quality load tester may be a good purchase if you need to test sealed batteries.
For any of these methods, you must first fully charge the battery and then remove the
surface charge. If the battery has been sitting at least several hours (I prefer at least 12
hours) you may begin testing. To remove surface charge the battery must be discharged
for several minutes. Using a headlight (high beam) will do the trick. After turning off the
light you are ready to test the battery.
State of Charge
Specific Gravity
Voltage
12V
6V
100%
1.265
12.7
6.3
*75%
1.225
12.4
6.2
50%
1.190
12.2
6.1
25%
1.155
12.0
6.0
Discharged
1.120
11.9
6.0
Sulfation of Batteries starts when specific gravity falls below 1.225 or voltage measures less
than 12.4 for a 12v battery, or 6.2 for a 6 volt battery. Sulfation hardens on the battery plates
reducing and eventually destroying the ability of the battery to generate Volts and Amps.
Load testing is yet another way of testing a battery. Load test removes amps from a
battery much like starting an engine would. A load tester can be purchased at most auto
parts stores. Some battery companies label their battery with the amp load for testing.
This number is usually 1/2 of the CCA rating. For instance, a 500CCA battery would load
53
test at 250 amps for 15 seconds. A load test can only be performed if the battery is near
or at full charge.
The results of your testing should be as follows:
Hydrometer readings should not vary more than .05 differences between cells. Digital
Voltmeters should read as the voltage is shown in this document. The sealed AGM and
Gel-Cell battery voltage (full charged) will be slightly higher in the 12.8 to 12.9 ranges.
If you have voltage readings in the 10.5 volts range on a charged battery that typically
indicates a shorted cell.
If you have a maintenance free wet cell, the only ways to test are voltmeter and load test.
Any of the maintenance free type batteries that have a built in hydrometer (black/green
window) will tell you the condition of 1 cell of 6. You may get a good reading from 1 cell
but have a problem with other cells in the battery.
When in doubt about battery testing, call the battery manufacturer. Many batteries sold
today have a toll free number to call for help.
6.3.3 Battery Capacity
"Battery capacity" is a measure (Amp-hr) of the charge stored by the battery, and is
determined by the mass of active material contained in the battery. The battery capacity
represents the maximum amount of energy that can be extracted from the battery under
certain specified conditions.
Solar Lighting System
Load X Hrs = Watt Hrs
Load
4
8
16
32
Use=Hrs/Day
12
12
12
12
Battery Size
Watt Hrs Per Day/DC Sys Volt=Avg AH/Day
Avg AH Per Day/Discharge Limit=Battery AH
Autonomy Discharge
Watt hrs
DC sys
Avg AH
per day
per day
days
limit
volt
32
12
2.67
1
0.5
48
12
4.00
1
0.5
64
12
5.33
1
0.5
96
12
8.00
1
0.5
128
12
10.67
1
0.5
192
12
16.00
1
0.5
256
12
21.33
1
0.5
384
12
32.00
1
0.5
54
Watt Hrs
48
96
192
384
Battery
AH
5.33
8.00
10.67
16.00
21.33
32.00
42.67
64.00
Battery
available
7 Ah
14 AH
14 AH
18 AH
26 AH
40 AH
48 AH
64 AH
6.7 Table showing the cable selection
System Voltagel 48V
Voltage Drop: 5.00%
0.245
0.194
Temperature (oC): 75
R
3.14
1.98
1.24
0.778
0.491
0.308
0.154
0.122
0.0967
0.0766
0.0608
0.0515
Amps
#14
#12
#10
#8
#6
#4
#1
#1/0
#2/0
#3/0
#4/0
250MCM
1.00
382.17
606.06 967.74 1542.42 2443.99 3896.10 4897.96 6185.57 7792.21 9836.07 12409.51 15665.80 19736.84 23300.97
2.00
191.08
303.03 483.87
771.21 1222.00 1948.05 2448.98 3092.78 3896.10 4918.03
6204.76
7832.90
9868.42 11650.49
4.00
95.54
151.52 241.94
385.60
611.00
974.03 1224.49 1546.39 1948.05 2459.02
3102.38
3916.45
4934.21
5825.24
6.00
63.69
101.01 161.29
257.07
407.33
649.35
816.33 1030.93 1298.70 1639.34
2068.25
2610.97
3289.47
3883.50
8.00
47.77
75.76 120.97
192.80
305.50
487.01
612.24
773.20
974.03 1229.51
1551.19
1958.22
2467.11
2912.62
10.00
38.22
60.61
96.77
154.24
244.40
389.61
489.80
618.56
779.22
983.61
1240.95
1566.58
1973.68
2330.10
12.00
31.85
50.51
80.65
128.53
203.67
324.68
408.16
515.46
649.35
819.67
1034.13
1305.48
1644.74
1941.75
14.00
27.30
43.29
69.12
110.17
174.57
278.29
349.85
441.83
556.59
702.58
886.39
1118.99
1409.77
1664.36
16.00
23.89
37.88
60.48
96.40
152.75
243.51
306.12
386.60
487.01
614.75
775.59
979.11
1233.55
1456.31
18.00
21.23
33.67
53.76
85.69
135.78
216.45
272.11
343.64
432.90
546.45
689.42
870.32
1096.49
1294.50
20.00
19.11
30.30
48.39
77.12
122.20
194.81
244.90
309.28
389.61
491.80
620.48
783.29
986.84
1165.00
25.00
15.29
24.24
38.71
61.70
97.76
155.84
195.92
247.42
311.69
393.44
496.38
626.63
789.47
932.04
30.00
12.74
20.20
32.26
51.41
81.47
129.87
163.27
206.19
259.74
327.87
413.65
522.19
657.89
776.70
35.00
10.92
17.32
27.65
44.07
69.83
111.32
139.94
176.73
222.63
281.03
354.56
447.59
563.91
665.74
40.00
9.55
15.15
24.19
38.56
61.10
97.40
122.45
154.64
194.81
245.90
310.24
391.64
493.42
582.52
45.00
8.49
13.47
21.51
34.28
54.31
86.58
108.84
137.46
173.16
218.58
275.77
348.13
438.60
517.80
50.00
7.64
12.12
19.35
30.85
48.88
77.92
97.96
123.71
155.84
196.72
248.19
313.32
394.74
466.02
55.00
6.95
11.02
17.60
28.04
44.44
70.84
89.05
112.46
141.68
178.84
225.63
284.83
358.85
423.65
60.00
6.37
10.10
16.13
25.71
40.73
64.94
81.63
103.09
129.87
163.93
206.83
261.10
328.95
388.35
65.00
5.88
9.32
14.89
23.73
37.60
59.94
75.35
95.16
119.88
151.32
190.92
241.01
303.64
358.48
70.00
5.46
8.66
13.82
22.03
34.91
55.66
69.97
88.37
111.32
140.52
177.28
223.80
281.95
332.87
75.00
5.10
8.08
12.90
20.57
32.59
51.95
65.31
82.47
103.90
131.15
165.46
208.88
263.16
310.68
80.00
4.78
7.58
12.10
19.28
30.55
48.70
61.22
77.32
97.40
122.95
155.12
195.82
246.71
291.26
85.00
4.50
7.13
11.39
18.15
28.75
45.84
57.62
72.77
91.67
115.72
145.99
184.30
232.20
274.13
90.00
4.25
6.73
10.75
17.14
27.16
43.29
54.42
68.73
86.58
109.29
137.88
174.06
219.30
258.90
95.00
4.02
6.38
10.19
16.24
25.73
41.01
51.56
65.11
82.02
103.54
130.63
164.90
207.76
245.27
100.00
3.82
6.06
9.68
15.42
24.44
38.96
48.98
64.86
77.92
98.36
124.10
156.66
197.37
233.01
125.00
3.06
4.85
7.74
12.34
19.55
31.17
39.18
49.48
62.34
78.69
99.28
125.33
157.89
186.41
150.00
2.55
4.04
6.45
10.28
16.29
25.97
32.65
41.24
51.95
65.57
82.73
104.44
131.58
155.34
175.00
2.18
3.46
5.53
8.81
13.97
22.26
27.99
35.35
44.53
56.21
70.91
89.52
112.78
133.15
200.00
1.91
3.03
4.84
7.71
12.22
19.48
24.49
30.93
38.96
49.18
62.05
78.33
98.68
116.50
225.00
1.70
2.69
4.30
6.86
10.86
17.32
21.77
27.49
34.63
43.72
55.15
69.63
87.72
103.56
250.00
1.53
2.42
3.87
6.17
9.78
15.58
19.59
24.74
31.17
39.34
49.64
62.66
78.95
93.20
275.00
1.39
2.20
3.52
5.61
8.89
14.17
17.81
22.49
28.34
35.77
45.13
56.97
71.77
84.73
300.00
1.27
2.02
3.23
5.14
8.15
12.99
16.33
20.62
25.97
32.79
41.37
52.22
65.79
77.67
400.00
0.96
1.52
2.42
3.86
6.11
9.74
12.24
15.46
19.48
24.59
31.02
39.16
49.34
58.25
Wire Gauge
#3
#2
55
System Voltagel 24V
R
3.14
1.98
Voltage Drop: 4.00%
1.24
0.778
0.491
0.308
0.245
0.194
Temperature (oC): 75
0.154
0.122
0.0967
0.0766
0.0608
0.0515
#1
#1/0
#2/0
#3/0
#4/0
250MCM
Wire Gauge
56
Amps
#14
#12
#10
1.00
152.87
242.42 387.10
616.97
977.60 1558.44 1959.18 2474.23 3116.88 3934.43
4963.81
6266.32
7894.74
9320.39
2.00
76.43
121.21 193.55
308.48
488.80
779.22
979.59 1237.11 1558.44 1967.21
2481.90
3133.16
3947.37
4660.19
4.00
38.22
60.61
96.77
154.24
244.40
389.61
489.80
618.56
779.22
983.61
1240.95
1566.58
1973.68
2330.10
6.00
25.48
40.40
64.52
102.83
162.93
259.74
326.53
412.37
519.48
655.74
827.30
1044.39
1315.79
1553.40
8.00
19.11
30.30
48.39
77.12
122.20
194.81
244.90
309.28
389.61
491.80
620.48
783.29
986.84
1165.05
10.00
15.29
24.24
38.71
61.70
97.76
155.84
195.92
247.42
311.69
393.44
496.38
626.63
789.47
932.04
12.00
12.74
20.20
32.26
51.41
81.47
129.87
163.27
206.19
259.74
327.87
413.65
522.19
657.89
776.70
14.00
10.92
17.32
27.65
44.07
69.83
111.32
139.94
176.73
222.63
281.03
354.56
447.59
563.91
665.74
16.00
9.55
15.15
24.19
38.56
61.10
97.40
122.45
154.64
194.81
245.90
310.24
391.64
493.42
582.52
18.00
8.49
13.47
21.51
34.28
54.31
86.58
108.84
137.46
173.16
218.58
275.77
348.13
438.60
517.80
20.00
7.64
12.12
19.35
30.85
48.88
77.92
97.96
123.71
155.84
196.72
248.19
313.32
394.74
466.02
25.00
6.11
9.70
15.48
24.68
39.10
62.34
78.37
98.97
124.68
157.38
198.55
250.65
315.79
372.82
30.00
5.10
8.08
12.90
20.57
32.59
51.95
65.31
82.47
103.90
131.15
165.46
208.88
263.16
310.68
35.00
4.37
6.93
11.06
17.63
27.93
44.53
55.98
70.69
89.05
112.41
141.82
179.04
255.56
266.30
40.00
3.82
6.06
9.68
15.42
24.44
38.96
48.98
61.86
77.92
98.36
124.10
156.66
197.37
233.01
45.00
3.40
5.39
8.60
13.71
21.72
34.63
43.54
54.98
69.26
87.43
110.31
139.25
175.44
207.12
50.00
3.06
4.85
7.74
12.34
19.55
31.17
39.18
49.48
62.34
78.69
99.28
125.33
157.89
186.41
55.00
2.78
4.41
7.04
11.22
17.77
28.34
35.62
44.99
56.67
71.54
90.25
113.93
143.54
169.46
60.00
2.55
4.04
6.45
10.28
16.29
25.97
32.65
41.24
51.95
65.57
82.73
104.44
131.58
155.34
65.00
2.35
3.73
5.96
9.49
15.04
23.98
30.14
38.07
47.95
60.53
76.37
96.40
121.46
143.39
70.00
2.18
3.46
5.53
8.81
13.97
22.26
27.99
35.35
44.53
56.21
70.91
89.52
112.78
133.15
75.00
2.04
3.23
5.16
8.23
13.03
20.78
26.12
32.99
41.56
52.46
66.18
83.55
105.26
124.27
80.00
1.91
3.03
4.84
7.71
12.22
19.48
24.49
30.93
38.96
49.18
62.05
78.33
98.68
116.50
85.00
1.80
2.85
4.55
7.26
11.50
18.33
23.05
29.11
36.67
46.29
58.40
73.72
92.88
109.65
90.00
1.70
2.69
4.30
6.86
10.86
17.32
21.77
27.49
34.63
43.72
55.15
69.63
87.72
103.56
95.00
1.61
2.55
4.07
6.49
10.29
16.40
20.62
26.04
32.81
41.42
52.25
65.96
83.10
98.11
100.00
1.53
2.42
3.87
6.17
9.78
15.58
19.59
24.74
31.17
39.34
49.64
62.66
78.95
93.20
125.00
1.22
1.94
3.10
4.94
7.82
12.47
15.67
19.79
24.94
31.48
39.71
50.13
63.16
74.56
150.00
1.02
1.62
2.58
4.11
6.52
10.36
13.06
16.49
20.78
26.23
33.09
41.78
52.63
62.14
175.00
0.87
1.39
2.21
3.53
5.59
8.91
11.20
14.14
17.81
22.48
28.36
35.81
45.11
53.26
200.00
0.76
1.21
1.94
3.08
4.89
7.79
9.80
12.37
15.58
19.67
24.82
31.33
39.47
46.60
225.00
0.68
1.08
1.72
2.74
4.34
6.93
8.71
11.00
13.85
17.49
22.06
27.85
35.09
41.41
250.00
0.61
0.97
1.55
2.47
3.91
6.23
7.84
9.90
12.47
15.74
19.86
25.07
31.58
37.28
275.00
0.56
0.88
1.41
2.24
3.55
5.67
7.12
9.00
11.33
14.31
18.05
22.79
28.71
33.89
300.00
0.51
0.81
1.29
2.06
3.26
5.19
6.53
8.25
10.39
13.11
16.55
20.89
26.32
31.07
400.00
0.38
0.61
0.97
1.54
2.44
3.90
4.90
6.19
7.79
9.84
12.41
15.67
19.74
23.30
#8
#6
#4
#3
#2

Solar Lighting Systems Module - Ministry of New and Renewable

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