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CHAPTER-1
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CHAPTER-1
INTRODUCTION
This project reveals the comfort conditions achieved by the device for the human body. In
summer (hot) and humid conditions feel uncomfortable because of hot weather and heavy humidity.
So it is necessary to maintain thermal comfort conditions. Thermal comfort is determined by the
room’s temperature, humidity and air speed. Radiant heat (hot surfaces) or radiant heat loss (cold
surfaces) are also important factors for thermal comfort. Relative humidity (RH) is a measure of the
moisture in the air, compared to the potential saturation level. Warmer air can hold more moisture.
When you approach 100% humidity, the air moisture condenses – this is called the dew point. The
temperature in a building is based on the outside temperature and sun loading plus whatever heating
or cooling is added by the HVAC or other heating and cooling sources. Room occupants also add
heat to the room since the normal body temperature is much higher than the room temperature. Need
of such a source which is abundantly available in nature, which does not impose any bad effects on
earth. There is only one thing which can come up with these all problems is solar energy.
The use of solar energy for cooling can be either to provide refrigeration for food
preservation or to provide comfort cooling. There is less experience with solar cooling than solar
heating. Several solar heated buildings have been designed, built, operated for extended periods but
only a few short time experiments have been reported on solar cooling. However, research work is
expected to close the gap between the two within few years.
Solar air conditioning systems have used two basic approaches in an attempt to capture the sun’s
energy for cooling thermal and photovoltaic. The photovoltaic systems use photovoltaic panels to
convert solar radiation directly into DC electricity. Photovoltaic systems have two major
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advantageous attributes. First, they can use conventional electrically driven air-conditioning
equipment, which is widely available and inexpensive. Second, they can use the utility grid for
backup power during dark or cloudy periods.
Unfortunately other attributes: the high cost of manufacturing, the low conversion efficiencies, and
the need for a continual stream of photons to produce power, create three major disadvantages. First
electricity from solar cells is very expensive because of the high cost of the solar panels. Second the
space needed for powering the air conditioning units is large. And third the panels provide no energy
storage, which creates a need for use of grid-based electricity at night and on cloudy days. In fact,
the peak output from the solar panels occurs around solar noon, while peak air-conditioning loads
occurs several hours later, resulting in a significant mismatch between supply of needed power and
demand. This mismatch greatly reduces the value of the system in reducing peak power demand to
the utility. Recently deregulated markets are demonstrating that these demands are much more
expensive to meet than had been previously apparent.
For off-grid locations, the only viable energy storage system to match the provision of power to
times when demand is high (later in afternoon and at night) is batteries. Batteries have a high first
cost, require periodic replacement, and normally use toxic and/or corrosive materials. These
problems have prevented the use of photovoltaic systems in other than a few high-cost
demonstration systems.
Thermally driven systems are another approach; they use heat from the sun to drive an air
conditioner. Typical approaches from the past used a high-temperature flat-plate collector to supply
heat to an absorption system. Systems with concentrating collectors and steam turbines have also
been proposed. Natural gas or other fuel is used for backup heat.
While thermal systems have the advantage of eliminating the need for expensive photovoltaic
panels, the existing systems have attributes that produce major disadvantages. As used in the past,
thermal systems are based on single-effect absorption chillers or other cooling systems that are
designed to use natural gas, steam or other high-temperature heat source. They require a very high
collector temperature to drive the cooling system. The high collector temperature and relatively poor
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efficiency, greatly increases collector size and cost. In addition, there is no economically viable way
of storing solar energy with this approach. The result of these problems is that thermal systems have
been very expensive and have relied primarily on natural gas or other fuel for their thermal energy.
For this reason they have seen very little use.
1.1 Present Problem:
The producing of electricity is ultimately responsible for hot and humid conditions i.e.
global warming. As in below shown chart it is clear that major quantity of electricity is produced by
coal (fossil fuel).
Fossil fuels also contain radioactive materials, mainly uranium and thorium, which are released into
the atmosphere, which contribute to smog and acid rain, emit carbon dioxide, which may contribute
to climate change. Longer power cut durations in villages and high cost of cooling products.
Figure 1.1: Production of electricity from different source
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1.2 Proposed Solution:
Need of such a source which is abundantly available in nature, which does not impose any
bad effects on earth. There is only one thing which can come up with these all problems is solar
energy.
Objective the Project:
● To make aware of non-conventional energy sources to reduce environmental pollutions.
● To provide solution for power cut problems in villages
● To replace existing costlier and high energy consumption
CHAPTER-2
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CHAPTER-2
LITERATURE REVIEW
Kant and Mullick (2003) have studied on thermal comfort in aroom with exposed roof using
evaporative cooling system. Hourly values of temperature and humidity are computed and compared
with the values that are obtained during unexposed condition. The levels of thermal sensation, which
could be obtained with a direct evaporative cooler, are computed.
El-Dessouky et al (2000) have developed For better human comfort, cooling of living or
work environment is vital in tropical climates. Researches carried out till date in evaporative air
cooling process focus mainly on reducing the dry bulb temperature of theincoming air. Theoretical
efficiency of 100% can be realized when dry bulb temperature of the room is equal to wet bulb
temperature of the outside ambient air; cooling efficiency is defined as the ratio between drop in dry
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bulb temperature across the cooler and the difference between inlet DBT and inlet WBT. Many
researchers have worked on improving cooling efficiency to the maximum possible extent.
Gomez et al (2005) have developed a ceramic solar cooling system which acts as a semi-indirect
cooler. The water cooled in a cooling tower is passed through the annulus passage of the ceramic
tube. The out side air is passed through the central region. Chilled water evaporates by seeping
through pores.
Jain (2007) has developed and tested a two-stage evaporative cooler. Such a cooler could provide
necessary comfort even though outside humidity is higher. The two-stage cooler is found to provide
20 % better cooling when compared to single stage cooler.
CHAPTER-3
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CHAPTER-3
SOLAR ENERGY
Solar energy is radiant light and heat from the Sun harnessed using a range of
ever-evolving technologies such as solar heating, photovoltaics, solar thermal energy, solar
architecture and artificial photosynthesis.It is an important source of renewable energy and its
technologies are broadly characterized as either passive solar or active solar depending on the
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way they capture and distribute solar energy or convert it into solar power. Active solar
techniques include the use of photovoltaic systems, concentrated solar power and solar water
heating to harness the energy. Passive solar techniques include orienting a building to the
Sun, selecting materials with favorable thermal mass or light dispersing properties, and
designing spaces that naturally circulate air.
The large magnitude of solar energy available makes it a highly appealing source of
electricity. The United Nations Development Programme in its 2000 World Energy
Assessment found that the annual potential of solar energy was 1,575–49,837 exajoules (EJ).
This is several times larger than the total world energy consumption, which was 559.8 EJ in
2012.In 2011, the International Energy Agency said that "the development of affordable,
inexhaustible and clean solar energy technologies will have huge longer-term benefits. It will
increase countries’ energy security through reliance on an indigenous, inexhaustible and
mostly import-independent resource, enhance sustainability, reduce pollution, lower the costs
of mitigating global warming, and keep fossil fuel prices lower than otherwise. These
advantages are global. Hence the additional costs of the incentives for early deployment
should be considered learning investments; they must be wisely spent and need to be widely
shared".
The Earth receives 174,000 terawatts (TW) of incoming solar radiation (insolation) at
the upper atmosphere. Approximately 30% is reflected back to space while the rest is
absorbed by clouds, oceans and land masses. The spectrum of solar light at the Earth's
surface is mostly spread across the visible and near-infrared ranges with a small part in the
near-ultraviolet. Most people around the world live in areas with isolation levels of 150 to
300 watts per square meter or 3.5 to 7.0 kWh/m 2 per day.
Solar radiation is absorbed by the Earth's land surface, oceans – which cover about
71% of the globe – and atmosphere. Warm air containing evaporated water from the oceans rises, causing atmospheric circulation or convection. When the air reaches a high altitude,
where the temperature is low, water vapor condenses into clouds, which rain onto the Earth's
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surface, completing the water cycle. The latent heat of water condensation amplifies
convection, producing atmospheric phenomena such as wind, cyclones and anti-cyclones.
Sunlight absorbed by the oceans and land masses keeps the surface at an average temperature
of 14 °C. By photosynthesis green plants convert solar energy into chemically stored energy,
which produces food, wood and the biomass from which fossil fuels are derived.
The total solar energy absorbed by Earth's atmosphere, oceans and land masses is
approximately 3,850,000 exajoules (EJ) per year. In 2002, this was more energy in one hour
than the world used in one year. Photosynthesis captures approximately 3,000 EJ per year in
biomass. The amount of solar energy reaching the surface of the planet is so vast that in one
year it is about twice as much as will ever be obtained from all of the Earth's non-renewable
resources of coal, oil, natural gas, and mined uranium combined the potential solar energy
that could be used by humans differs from the amount of solar energy present near the
surface of the planet because factors such as geography, time variation, cloud cover, and the
land available to humans limits the amount of solar energy that we can acquire.
Geography affects solar energy potential because areas that are closer to the equator
have a greater amount of solar radiation. However, the use of photo voltaics that can follow
the position of the sun can significantly increase the solar energy potential in areas that are
farther from the equator. Time variation affects the potential of solar energy because during
the nighttime there is little solar radiation on the surface of the Earth for solar panels to
absorb. This limits the amount of energy that solar panels can absorb in one day. Cloud cover
can affect the potential of solar panels because clouds block incoming light from the sun and
reduce the light available for solar cells.In addition, land availability has a large effect on the
available solar energy because solar panels can only be set up on land that is unowned and
suitable for solar panels. Roofs have been found to be a suitable place for solar cells, as many
people have discovered that they can collect energy directly from their homes this way. Other
areas that are suitable for solar cells are lands that are unowned by businesses where solar
plants can be established..
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Active solar techniques use photo voltaic, concentrated solar power, solar
thermal collectors, pumps, and fans to convert sunlight into useful outputs. Passive solar
techniques include selecting materials with favorable thermal properties, designing spaces
that naturally circulate air, and referencing the position of a building to the Sun. Active solar
technologies increase the supply of energy and are considered supply side technologies,
while passive solar technologies reduce the need for alternate resources and are generally
considered demand side technologies.
FIGURE: 3.1 how to get solar energy to battery and load
Solar technologies are broadly characterized as either passive or active depending on the way they
capture, convert and distribute sunlight and enable solar energy to be harnessed at different levels
around the world, mostly depending on distance from the equator. Although solar energy refers
primarily to the use of solar radiation for practical ends, all renewable energies, other than
geothermal and tidal, derive their energy from the Sun in a direct or indirect way
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Figure: 3.2 solar energy utilization
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CHAPTER-4
CHAPTER-4
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WORKING OF THE PROJECT
Working Methodology:
This project mainly consists of two sections:
4.1 Solar Energy Conversion:
Solar energy conversion is done by using battery, inverter and charge controller. As sun light
falls on solar panel, which converts into electrical energy by photoelectric effect. This electrical
energy stored in battery in the form of chemical energy. Charge controller is employed in between
solar panel and battery which prevents overcharging Figure 2: Solar energy conversion process and
may protect against overvoltage, which can reduce battery performance or lifespan, and may pose a safety risk.
The stored energy directly can use for DC loads or else need to be converted AC (alternate
current) bythe help of inverter. Figure 2: Solar energy conversion process
4.2 Cool air generation by centrifugal fan:
The converted energy is used to run the centrifugal fan. This fan covered with cooling pads,
through which water is passed at a specific rate. As the fan sucks the hot air through cooling pads,
heat transfer occur between air and water thus generated cool air enters into the room. Figure 3:
Process of cool air generation by centrifugal fan.
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Fig 4.1 Air cooler
4.3 Working Model of the Project:
Solar powered air cooler. This concept is driven by solar energy. Components involved in
this concept are solar panel, battery, charge controller, battery, inverter, blower, ceramic slabs and
cooling pads. Solar panel is employed to convert sun light into electrical energy by means of
photovoltaic effect. The generated electrical energy is supplied to the battery for storage purpose
through charge controller which prevents from power fluctuations. As AC blower is used for cooler,
so need to convert DC load from the battery to AC load by the help of inverter. Inverter converts DC
load to AC. Load, now AC power can be supplied to the blower. This blower is surrounded by
cooling pads through which continuous water supply is provided. When the blower is switched on,
blower sucks atmospheric air into the cabin through the cooling pads, mean time heat transfer occur
Between water and air, so the cool air enters into the room thus providing required thermal comfort
conditions.
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Fig no: 4.2 working of the solar powered air cooler
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CHAPTER-5
CHAPTER-5
COMPONENTS USED
5.1 Solar panel
Solar chargers convert light energy into DC current. They are generally portable, but can also be fixed mount. Fixed mount solar chargers are also known as solar panels. Solar panels are often
connected to the electrical grid, where as portable solar chargers as used off-the-grid (i.e. cars, boats,
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or RVs).Although portable solar chargers obtain energy from the sun only, they still can (depending
on the technology) be used in low light (i.e. cloudy) applications.
Portable solar charger are typically used for trickle charging, although some solar charger
(depending on the wattage), can completely recharge batteries.Solar panels (arrays of photovoltaic
cells) make use of renewable energy from the sun, and are a clean and environmentally sound means
of collecting solar energy.
Fig no: 5.1 Solar panel
5.2 Crystalline Silicon Solar Panels
The creation of solar panels typically involves cutting crystalline silicon into tiny disks less
than a centimeter thick. These thin, wafer-like disks are then carefully polished and treated to repair
and gloss any damage from the slicing process. After polishing, dopants (materials added to alter an
electrical charge in a semiconductor or photovoltaic solar cell) and metal conductors are spread
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across each disk. The conductors are aligned in a thin, grid-like matrix on the top of the solar panel,
and are spread in a flat, thin sheet on the side facing the earth.
To protect the solar panels after processing, a thin layer of cover glass is then bonded to the top of
the photovoltaic cell. After the bonding of protective glass, the nearly-finished panel is attached to a
substrate by expensive, thermally conductive cement. The thermally conductive property of the
cement keep the solar panel from becoming overheated; any leftover energy that the solar panel is
unable to convert to electricity would otherwise overheat the unit and reduce the efficiency of the
solar cells. Despite these protective measures against the tendency of solar panels to overheat, it is
vital that when installing a solar panel, additional steps should be taken to ensure the solar panel is
kept cool. Elevating the solar panel above ground, to let the airflow underneath, will cool the device.
5.3Amorphous Silicon Solar Panels
Amorphous silicon solar panels are a powerful that differ in output, structure and
manufacture than traditional photovoltaic’s which use crystalline silicon. Amorphous silicon solar
cells, or A-si cells, are developed in a continuous roll-to-roll process by vapor-depositing silicon
alloys in multiple layers, with each extremely thin layer specializing in the absorption of different
parts of the solar spectrum. The result is record-breaking efficiency and reduced materials cost (A-si
solar cells are typically thinner than their crystalline counterparts).
5.4 How does the solar panel works
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The solar cells on the calculators and satellites are also called photovoltaic (PV) cells, which
as the name implies (photo meaning "light" and voltaic meaning "electricity"), convert sunlight
directly into electricity. A module is a group of cells connected electrically and packaged into a
frame (more commonly known as a solar panel), which can then be grouped into larger solar arrays.
Photovoltaic cells are made of special materials called semiconductors such as silicon, which
is currently used most commonly. Basically, when light strikes the cell, a certain portion of it is
absorbed within the semiconductor material. This means that the energy of the absorbed light is
transferred to the semiconductor. The energy knocks electrons loose, allowing them to flow freely.
PV cells also all have one or more electric field that acts to force electrons freed by light absorption
to flow in a certain direction. This flow of electrons is a current and by placing metal contacts on the
top and bottom of the PV cell, the current can be drawn off for external use such as to power a
calculator. This current, together with the cell's voltage (which is a result of its built-in electric field
or fields), defines the power (or wattage) that the solar cell can produce.
5.5Battery:
An electrical battery is one or more electrochemical cells that convert stored chemical
energy into electrical energy. The invention of the first battery (or "voltaic pile") was in 1800 by
Alessandro Volta. Nowadays, batteries have become a common power source for many household
and industrial applications. According to a 2005 estimate, the worldwide battery industry generates
US$48 billion in sales each year, with 6% annual growth.There are two types of batteries: primary
batteries (disposable batteries), which are designed to be used once and discarded and secondary
batteries (rechargeable batteries), which are designed to be recharged and used multiple times.
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Fig no: 5.2 Battery
Miniature cells are used to power devices such as hearing aids and wristwatches whereas larger
batteries provide standby power for telephone exchanges or computer data centers.
The solar energy is converted to electrical energy by photo-voltaic cells. This energy is stored in
batteries during day time for utilizing the same during night time. This project deals with a
controlled charging mechanism which over charge, deep discharge and under voltage of the battery.
In this project a solar panel is used to charge a battery. Indications are also provide by
a Red LED off for fully charged battery while a set of red LEDs on to indicate under charged,
overloaded and deep discharge condition. Charge controller also uses MOSFET as power
semiconductor switch to ensure cut off the load in low battery or overload condition. A transistor is
used to bypass the solar energy to a dummy load
While the battery gets fully charged. This protects the battery from getting over charged.
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The requirement and use of electrical energy is increasing rapidly with technology development and
population growth. By using renewable and non-renewable sources, electrical energy is generated.
Multiple advantages of solar energy are the key factors behind the usage of solar charge
controller for various purposes in industrial applications. Solar charge controller is used for storing
the electrical power in batteries which is generated with the help of solar panels and further it can be
fed into loads.
A solar charge controller is basically a current or a voltage controller to charge the
battery and to protect the cells from overcharging. It directs the current and voltage comes from the
solar panels to charge the battery. Generally, 12V panels are put out in the approximate value of 16
to 20V, so in the overcharging condition the electric cells will be damaged if no regulation is
provided. For getting completely charged, electric storage devices require14 to 14.5V. The solar
charge controller circuits are available in all features, sizes and costs ranges from 4.5A to
60-80A.Here in this article we are going to discuss about solar charge controller using comparators
and as advancement to that solar charge controller circuit with microcontroller is also explained.
5.6COOLER FAN
Typical applications include climate control and personal thermal comfort (e.g., an
electric table or floor fan), vehicle and machinery cooling systems, ventilation, fume
extraction, winnowing (e.g., separating chaff of cereal grains), removing dust (e.g. in a vacuum
cleaner), drying (usually in combination with heat) and to provide draft for a fire. While fans are
often used to cool people, they do not actually cool air (if anything, electric fans warm it slightly due
to the warming of their motors), but work by evaporative cooling of sweat and increased
heat convection into the surrounding air due to the airflow from the fans. Thus, fans may become
ineffective at cooling the body if the surrounding air is near body temperature and contains high
humidity.
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Processors in most early x86-based computers, up to some of the early 486s, did not
need active ventilation. Power supplies needed forced cooling, and power supply fans also circulated
cooling air through the rest of the PC with the ATX standard. The byproduct of increased heat
generation is that the fan(s) need to move increasing amounts air and thus need to be more powerful.
Since they must move more air through the same area of space, fans will become more noisy.
Fans installed in a PC case can produce noise levels of up to 70 dB. Since fan noise
increases with the fifth power of the fan rotation speed, reducing rotations per minute (RPM) by a
small amount potentially means a large reduction in fan noise. This must be done cautiously, as
excessive reduction in speed may cause components to overheat and be damaged. If done properly
fan noise can be drastically reduced.
The common cooling fans used in computers use standardized connectors with two to four pins. The
first two pins are always used to deliver power to the fan motor, while the rest can be optional,
depending on fan design and type:
Power – nominally +12 V, though it may be variable depending on fan type and desired fan rotation
speed
Sense output from fan – outputs a signal that pulses twice for each rotation of the fan as a pulse train,
with the signal frequency proportional to the fan speed Control input – a pulse-width
modulation (PWM) input signal, which gives the ability to adjust the rotation speed on the fly
without changing the input voltage delivered to the cooling fan.The color of the wires connected to
these pins varies depending on the number of connectors, but the role of each pin is standardized and
guaranteed to be the same on any system. Cooling fans equipped with either two- or three-pin
connectors are usually designed to accept a wide range of input voltages, which directly affects the
rotation speed of the blades.
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FIGURE: 5.3 cooler fan
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5.7Electric motors
Electric motors are used to efficiently convert electrical energy into mechanical energy.
Magnetism is the basis of their principles of operation. They use permanent magnets,
electromagnets, and exploit the magnetic properties of materials in order to create these amazing
machines.
There are several types of electric motors available today. The following outline gives an
overview of several popular ones. There are two main classes of motors: AC and DC. AC motors
require an alternating current or voltage source (like the power coming out of the wall outlets in your
house) to make them work. DC motors require a direct current or voltage source (like the voltage
coming out of batteries) to make them work. Universal motors can work on either type of power. Not
only is the construction of the motors different, but the means used to control the speed and torque
created by each of these motors also varies, although the principles of power conversion are common
to both.
Motors are used just about everywhere. In our house, there is a motor in the furnace for the
blower, for the intake air, in the sump well, dehumidifier, in the kitchen in the exhaust hood above
the stove, microwave fan, refrigerator compressor and cooling fan, can opener, garbage disposer,
dish washer pump, clocks, computer fans, ceiling fans, and many more items. In industry, motors are
used to move, lift, rotate, accelerate, brake, lower and spin material in order to coat, paint, punch,
plate, make or form steel, film, paper, tissue, aluminum, plastic and other raw materials. They range in power ratings from less than 1/100 hp to over 100,000 hp. The rotate as slowly as 0.001 rpm to
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over 100,000 rpm. They range in physical size from as small as the head of a pin to the size of a
locomotive engine.
5.7.1 AC Motors
An AC motor is an electric motor that is driven by an alternating current. It consists of two
basic parts, an outside stationary stator having coils supplied with alternating current to produce a
rotating magnetic field, and an inside rotor attached to the output shaft that is given a torque by the
rotating field.
There are two types of AC motors, depending on the type of rotor used. The first is the
synchronous motor, which rotates exactly at the supply frequency or a sub multiple of the supply
frequency. The magnetic field on the rotor is either generated by current delivered through slip rings
or by a permanent magnet. The second type is the induction motor, which runs slightly slower than
the supply frequency. The magnetic field on the rotor of this motor is created by an induced current.
5.7.2 Types of Motors
5.7.2.1 Split Phase
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The split phase motor is mostly used for "medium starting" applications. It has start and run
windings, both are energized when the motor is started. When the motor reaches about 75% of its
rated full load speed, the starting winding is disconnected by an automatic switch.
Uses: This motor is used where stops and starts are somewhat frequent. Common applications of
split phase motors include: fans, blowers, office machines and tools such as small saws or drill
presses where the load is applied after the motor has obtained its operating speed.
5.7.2.2 Capacitor Start
This motor has a capacitor in series with a starting winding and provides more than double
the starting torque with one third less starting current than the split phase motor. Because of this
improved starting ability, the capacitor start motor is used for loads which are hard to start. It has
good efficiency and requires starting currents of approximately five times full load current. The
capacitor and starting windings are disconnected from the circuit by an automatic switch when the
motor reaches about 75% of its rated full load speed.
Uses: Common uses include: compressors, pumps, machine tools, air conditioners, conveyors,
blowers, fans and other hard to start applications.
5.7.2.3 Phase, Voltage & Rotation
Whether or not you can use a motor will likely depend on these factors.
5.7.2.4 Single Phase
Ordinary household wiring is single phase, alternating current. Each cycle peaks and dips as
shown. To run a three phase motor a phase converter must be used, usually this is not practical, it is
often less expensive to change the motor on a machine to a single phase style.
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Fig 5.5 block diagram
The speed of the AC motor is determined primarily by the frequency of the AC supply and the
number of poles in the stator winding, according to the relation:
Ns = 120F / p
Where
N s = Synchronous speed, in revolutions per minute
F = AC power frequency p = Number of poles per phase windin
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6.1 Solar Power Charge Controller Circuit using Comparators
The solar charge controller project is designed to store electrical energy in batteries
which is obtained by converting the solar energy into electrical energy with the help of
photo-voltaic cells during the daytime and to utilize this stored solar energy during night
time. For monitoring the voltage and load current of solar panels a set of op-amps are used
as comparators as shown in the block diagram.
Fig: 6.1 Solar Power Charge Controllers
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Different types of light emitting diodes are used to indicate the following conditions:
under voltage, overload and deep discharge conditions. To cut off the load in overload and
low battery conditions MOSFET is used as a power semiconductor switch. If the battery is
fully charged, then the solar energy is transferred to the dummy load with the help of a
transistor. This project can be further developed by using microcontroller.
6.2 PV PANEL
In a photovoltaic cell, light excites electrons to move from one layer to another
throughsemi-conductive silicon materials. This produces an electric current.Solar cells called
photovoltaics made from thin slices of crystalline silicon, gallium arsenide, or other
semiconductor materials convert solar radiation directly into electricity. Cells with conversion
efficiencies greater than 30 percent are now available. By connecting large numbers of these
cells into modules, the cost of photovoltaic electricity has been reduced to 20 to 30 cents
per kilowatt-hour. Americans currently pay 6 to 7 cents per kilowatt-hour for conventionally
generated electricity.
The simplest solar cells provide small amounts of power for watches and calculators. More
complex systems can provide electricity to houses and electric grids. Usually though, solar
cells provide low power to remote, unattended devices such as buoys, weather and
communication satellites, and equipment aboard spacecraft.
6.3 CHARGE CONTROLLER
A charge controller, charge regulator or battery regulator limits the rate at which electric
current is added to or drawn from electric batteries. It prevents overcharging and may prevent
against overvoltage, which can reduce battery performance or lifespan, and may pose a safety
risk. It may also prevent completely draining ("deep discharging") a battery, or perform
controlled discharges, depending on the battery technology, to protect battery life. The terms
"charge controller" or "charge regulator" may refer to either a stand-alone device,
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or to control circuitry integrated within a battery pack,battery-powered device, or battery
recharger.
A series charge controller sor series regulator disables further current flow into
batteries when they are full. A shunt charge controller or shunt regulator diverts excess
electricity to an auxiliary or "shunt" load, such as an electric water heater, when batteries are
full.
6.4 INVERTER
Power inverter, or inverter, is an electronic device or circuitry that changes direct
current (DC) to alternating current (AC).
The input voltage, output voltage and frequency, and overall power handling depend on the design of
the specific device or circuitry. The inverter does not produce any power; the power is provided by
the DC source.
A power inverter can be entirely electronic or may be a combination of mechanical effects
(such as a rotary apparatus) and electronic circuitry. Static inverters do not use moving parts in the
conversion process.
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Fig no: 6.2 Inverter
6.5 Input and output
Input voltage
A typical power inverter device or circuit requires a relatively stable DC power
source capable of supplying enough current for the intended power demands of the system. The
input voltage depends on the design and purpose of the inverter. Examples include:
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● 12 VDC, for smaller consumer and commercial inverters that typically run from a rechargeable
12 V lead acid battery.
● 24 and 48 VDC, which are common standards for home energy systems.
● 200 to 400 VDC, when power is from photovoltaic solar panels.
● 300 to 450 VDC, when power is from electric vehicle battery packs in vehicle-to-grid systems.
● Hundreds of thousands of volts, where the inverter is part of a high voltage direct current power
transmission system.
6.6 Output waveform
An inverter can produce a square wave, modified sine wave, pulsed sine wave, pulse width
modulated wave (PWM) or sine wave depending on circuit design. The two dominant
commercialized waveform types of inverters as of 2007 are modified sine wave and sine wave.
There are two basic designs for producing household plug-in voltage from a lower-voltage
DC source, the first of which uses a switching boost converter to produce a higher-voltage DC and
then converts to AC. The second method converts DC to AC at battery level and uses
a line-frequency transformer to create the output voltage.
Fig 6.3 Square wave
6.6.1 Square wave
This is one of the simplest waveforms an inverter design can produce and is best suited to
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low-sensitivity applications such as lighting and heating. Square wave output can produce
"humming" when connected to audio equipment and is generally unsuitable for sensitive electronics.
Fig 6.4 Sine wave
6.6.2 Sine wave
A power inverter device which produces a multiple step sinusoidal AC waveform is referred
to as a sine wave inverter. To more clearly distinguish the inverters with outputs of much less
distortion than the "modified sine wave" (three step) inverter designs, the manufacturers often use
the phrase pure sine wave inverter. Almost all consumer grade inverters that are sold as a "pure sine
wave inverter" do not produce a smooth sine wave output at all, just a less choppy output than the
square wave (one step) and modified sine wave (three step) inverters. In this sense, the phrases "Pure
sine wave" or "sine wave inverter" are misleading to the consumer. However, this is not critical for
most electronics as they deal with the output quite well. Where power inverter devices substitute for
standard line power, a sine wave output is desirable because many electrical products are engineered
to work best with a sine wave AC power source. The standard electric utility power attempts to
provide a power source that is a good approximation of a sine wave.
Sine wave inverters with more than three steps in the wave output are more complex and have
significantly higher cost than a modified sine wave, with only three steps, or square wave (one step)
types of the same power handling. Switch-mode power supply (SMPS) devices, such as personal
computers or DVD players, function on quality modified sine wave power. AC motors directly
operated on non-sinusoidal power may produce extra heat, may have different speed-torque
characteristics, or may produce more audible noise than when running on sinusoidal power.
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6.6.3 Modified sine wave
A "modified sine wave" inverter has a non-square waveform that is a useful rough
approximation of a sine wave for power translation purposes. Most inexpensive consumer power
inverters produce a modified sine wave rather than a pure sine wave.
The waveform in commercially available modified-sine-wave inverters is a square wave with
a pause before the polarity reversal, which only needs to cycle back and forth through a
three-position switch that outputs forward, off, and reverse output at the pre-determined frequency.
Switching states are developed for positive, negative and zero voltages as per the patterns given in
the switching Table 2. The peak voltage to RMS voltage ratio does not maintain the same
relationship as for a sine wave. The DC bus voltage may be actively regulated, or the "on" and "off"
times can be modified to maintain the same RMS value output up to the DC bus voltage to
compensate for DC bus voltage variations.
The ratio of on to off time can be adjusted to vary the RMS voltage while maintaining a
constant frequency with a technique called Pulse Width Modulation (PWM). The generated gate
pulses are given to each switch in accordance with the developed pattern to obtain the desired
output. Harmonic spectrum in the output depends on the width of the pulses and the modulation
frequency. When operating induction motors, voltage harmonics are usually not of concern;
however, harmonic distortion in the current waveform introduces additional heating and can produce
pulsating torques. Numerous items of electric equipment will operate quite well on modified sine
wave power inverter devices, especially loads that are resistive in nature such as traditional
incandescent light bulbs.
However, the load may operate less efficiently owing to the harmonics associated with a
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modified sine wave and produce a humming noise during operation. This also affects the efficiency
of the system as a whole, since the manufacturer's nominal conversion efficiency does not account
for harmonics. Therefore, pure sine wave inverters may provide significantly higher efficiency than
modified sine wave inverters.
Most AC motors will run on MSW inverters with an efficiency reduction of about 20%
owing to the harmonic content. However, they may be quite noisy. A series LC filter tuned to the
fundamental frequency may help. A common modified sine wave inverter topology found in
consumer power inverters is as follows:
An onboard microcontroller rapidly switches on and off power MOSFETs at high frequency
like ~50 kHz. The MOSFETs directly pull from a low voltage DC source (such as a battery). This
signal then goes through step-up transformers (generally many smaller transformers are placed in parallel to reduce the overall size of the inverter) to produce a higher voltage signal. The output of
the step-up transformers then gets filtered by capacitors to produce a high voltage DC supply.
Finally, this DC supply is pulsed with additional power MOSFETs by the microcontroller to produce
the final modified sine wave signal.
6.6.4 Other waveforms
By definition there is no restriction on the type of AC waveform an inverter might produce
that would find use in a specific or special application.
Output frequency
The AC output frequency of a power inverter device is usually the same as standard power
line frequency, 50 or 60 hertz. If the output of the device or circuit is to be further conditioned (for
example stepped up) then the frequency may be much higher for good transformer efficiency.
Output voltage
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The AC output voltage of a power inverter is often regulated to be the same as the grid line
voltage, typically 120 or 240 VAC, even when there are changes in the load that the inverter is
driving. This allows the inverter to power numerous devices designed for standard line power.
Some inverters also allow selectable or continuously variable output voltages.
Output power
A power inverter will often have an overall power rating expressed in watts or kilowatts. This
describes the power that will be available to the device the inverter is driving and, indirectly, the
power that will be needed from the DC source.
Smaller popular consumer and commercial devices designed to mimic line power typically range
from 150 to 3000 watts. Not all inverter applications are solely or primarily concerned with power
delivery; in some cases the frequency and or waveform properties are used by the follow-on circuit
or device.
Batteries
The runtime of an inverter is dependent on the battery power and the amount of power being
drawn from the inverter at a given time. As the amount of equipment using the inverter increases, the
runtime will decrease. In order to prolong the runtime of an inverter, additional batteries can be
added to the inverter When attempting to add more batteries to an inverter, there are two basic
options for installation: Series Configuration and Parallel Configuration.
Series configuration
If the goal is to increase the overall voltage of the inverter, one can daisy chain batteries in
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a Series Configuration. In a Series Configuration, if a single battery dies, the other batteries will not
be able to power the load.
Parallel configuration
Increase capacity and prolong the runtime of the inverter, batteries can be connected in
parallel. This increases the overall Ampere-hour (Ah) rating of the battery set. If a single battery is
discharged though, the other batteries will then discharge through it. This can lead to rapid discharge
of the entire pack, or even an over-current and possible fire. To avoid this, large paralleled batteries
may be connected via diodes or intelligent monitoring with automatic switching to isolate an
under-voltage battery from the others.
Applications
DC power source usage
Inverter designed to provide 115 VAC from the 12 VDC source provided in an automobile. The unit
shown provides up to 1.2 amperes of alternating current, or enough to power two sixty watt light
bulbs. An inverter converts the DC electricity from sources such as batteries or fuel cells to AC
electricity. The electricity can be at any required voltage; in particular it can operate AC equipment
designed for mains operation, or rectified to produce DC at any desired voltage. Uninterruptible
power supplies an uninterruptible power supply (UPS) uses batteries and an inverter to supply AC
power when mains power is not available. When mains power is restored, a rectifier supplies DC
power to recharge the batteries.
Electric motor speed control
Inverter circuits designed to produce a variable output voltage range are often used within
motor speed controllers. The DC power for the inverter section can be derived from a normal AC
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wall outlet or some other source. Control and feedback circuitry is used to adjust the final output of
the inverter section which will ultimately determine the speed of the motor operating under its
mechanical load.
Motor speed control needs are numerous and include things like: industrial motor driven equipment,
electric vehicles, rail transport systems, and power tools. (See related: variable-frequency drive )
Switching states are developed for positive, negative and zero voltages as per the patterns given in
the switching Table 1.The generated gate pulses are given to each switch in accordance with the
developed pattern and thus the output is obtained.
Power grid
Grid-tied inverters are designed to feed into the electric power distribution system. They
transfer synchronously with the line and have as little harmonic content as possible. They also need a
means of detecting the presence of utility power for safety reasons, so as not to continue to
dangerously feed power to the grid during a power outage.
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Fig 6.5 Internal view of Solar Inverter
Internal view of a solar inverter. Note the many large capacitors (blue cylinders), used to store
energy briefly and improve the output waveform.
6.7 Solar inverter:
A solar inverter is a balance of system (BOS) component of a photovoltaic system and can be
used for both, grid-connected and off-grid systems. Solar inverters have special functions adapted for
use with photovoltaic arrays, including maximum power point
tracking andanti-islanding protection. Solar micro-inverters differ from conventional converters, as
an individual micro-converter is attached to each solar panel. This can improve the overall efficiency
of the system. The output from several micro inverters is then combined and often fed to the electrical grid.
6.8 Induction heating
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Inverters convert low frequency main AC power to higher frequency for use in induction
heating. To do this, AC power is first rectified to provide DC power.
The inverter then changes the DC power to high frequency AC power. Due to the reduction
in the number of DC sources employed, the structure becomes more reliable and the output voltage has higher resolution due to an increase in the number of steps so that the reference sinusoidal
voltage can be better achieved.
This configuration has recently become very popular in AC power supply and adjustable
speed drive applications. This new inverter can avoid extra clamping diodes or voltage balancing
capacitors.
Results and Discussion
The output of the project is Comfort thermal conditions achieved in the living room. That is
room temperature up to 25o C and relative humidity of 60%.
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CHAPTER-7
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CHAPTER-7
CALCULATIONS
● Hence selected Fan Specification: 230v, 50Hz, 35W
So to run 40W fan on for 1 hour will take
40*1=40Wh from the battery (Battery capacity is measured in Amp hours)
● 10Ah, 12v battery the watt hours is given by
P=V*I
V=12v and I=40Ah
P= 40*12=480Wh
So, the 40W centrifugal fan runs for
480/40=12h
This means the battery could supply 40W fan for 12 hours
● To calculate the energy it can supply to the battery, multiply watts by the hours exposed to
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sunlight, then multiply the result by 0.85(This factor allows for natural system losses)
For the solar 10W panel in 6 hours sunshine, 10*6*0.85 = 57Wh
For 1 hour, 10*1*0.85 = 8.5Wh
So the solar panel of 10W and battery of 40Ah are selected (Office purpose)
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CHAPTER-8
CHAPTER-8
ADVANTAGES AND LIMITATION
ADVANTAGES
● The demand for cooler is likely to increase because worldwide temperature increases. While
using soaring demand in energy, count on costs in order to continually advance.
● Any a lot more feasible, long-term solution lies in harnessing solar energy to cool our own
atmosphere through any solar air cooler solar panel array. Whenever you think about the
idea, the days when you need air-cooling most are generally those days when the solar
reaches its best.
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● The solar air cooler can work precisely. Solar air cooler makes use of the solar panel that
soaks up and traps heat from the sun within the form of thermal power simply by warming
normal water.
● This power can be delivered to the solar air cooler along with heats up the solution causing it
to steam. Since it cools it creates a cooling effect that's taken into an additional water loop
● Solar air conditioning provides a great package involving benefits. Installation expenses can
be reduced through tax credits, deductions and also refunds. .
● In humid regions, desiccant dehumidification can reduce electricity demand considerably by
providing a drier, more comfortable, and clean indoor environment with a lower energy bill.
Desiccant systems allow more fresh air into buildings, thus improving indoor air quality
without using more energy.
● Desiccant systems also displace chlorofluorocarbon-based cooling equipment, the emissions
from which contribute to the depletion of the Earth's ozone layer.
● Desiccant dehumidification technology provides a method of drying air before it enters a
conditioned space. When combined with conventional vapour compression systems,
desiccant dehumidification systems are a cost-effective means of supplying cool, dry, filtered
air.
LIMITATIONS
● In cloudy conditions solar collector cannot work properly as sun rays are not uniform.
● Slow working process as less moving parts.
● Process totally dependent on supply of suns radiation.
● Less efficient due to intermittent supply of suns radiation.
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CONCLUSION
Comparing the cost of this product with the existing products in the market is solar product
appeals better and affordable by common people.
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This solar product perfectly suits for villages, schools and offices and thus an alternate to the
power cut problems. It comprises of many attractive features such as usage of solar energy, cooler
and cooling cabin at lower cost. It is eco friendly and natural, electricity savers.
Durability of the product is more thus minimizing the cost. No electricity is used so this
product saves the energy and saves environment from getting polluted.
FUTURES SCOPE
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Where Power Energy not available in that areas Solar Energy is adopted to meet the needs.
Solar Energy is alternative to conventional Energy due to more advantages like eco-friendly, reduce
the green house effects no pollutant and low cost.
It is cost effective as the whole cost of the project becomes very less and cheap as compared
to other traditional electric air conditioner and it is less bulky too.
However, more further scope to air cooler by using solar energy in remoted areas we
recommend to society to use solar energy
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REFERENCES
1. Farhan a. khmamas, 2012, “Improving the environmental cooling for air-coolers by
using the indirect-cooling method” ARPN journal of engineering and applied
sciences, vol. 5, No. 2, page No. 66-73.
2. A S Alosaimy, 2013 “Application of Evaporative Air Coolers Coupled With Solar
Water Heater for Dehumidification of Indoor Air” International Journal of
Mechanical & Mechatronics Engineering, Vol:13 No:01 page no. 60- 68.
3. “Basic Photovoltaic Principles and Methods” SERI/SP- 290-1448 Solar Information
Module 6213 Published February 1982 page. No. 9-15.
4. Arora and Domkundwar, A text book “The course on power plant engineering”.
5. B. Srinivas Reddy, K Hemachandra Reddy, “Thermal engineering data hand book”.