ABSTRACT

The present seminar deals with the explanation of the advantages & necessity of solar power in the present world through solar powered vehicles. Solar-powered vehicles (SPVs), such as cars, boats, bicycles, and even airplanes, use solar energy to either power an electric motor directly, and/or use solar energy to charge a battery, which powers the motor. They use an array of solar photovoltaic (PV) cells (or modules made of cells) that convert sunlight into electricity. The electricity either goes directly to an electric motor powering the vehicle, or to a special storage battery. The PV array can be built (integrated) onto the vehicle body itself, or fixed on a building or a vehicle shelter to charge an electric vehicle (EV) battery when it is parked. Other types of renewable energy sources, such as wind energy or hydropower, can also produce electricity cleanly to charge EV batteries.

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CONTENTS

CHAPTERS PAGE NO
1. INTRODUCTION 01
2. HISTORY 02
3. BASIC PRINCIPLES 03
3.1 When Light Hits the Cell 03
3.2. Silicon in Solar Cells 03
3.3. N-type Plus P-type Silicon 06
3.4. How Solar Cells Work 06
4. COMPONENTS USED TO PROVIDE SOLAR POWER 08
4.1. Solar Panels 08
4.2. Charge Controller 08
4.3. Battery 09
5. APPLICATIONS 12
6. ADVANTAGES 18
7. CONCLUSION 19
REFERENCES 20


CHAPTER 1
INTRODUCTION

In the present situation energy crisis is an important unsolvable problem so we must find out some other ways to trust all sources such as solar energy, hydro power, tidal power, wind power etc. Using solar power to produce electricity is not the same as using solar to produce heat. Solar thermal principles are applied to produce hot fluids or air. Photovoltaic principles are used to produce electricity. A solar panel (PV panel) is made of the natural element, silicon, which becomes charged electrically when subjected to sun light.

Solar panels are directed at solar south in the northern hemisphere and solar north in the southern hemisphere (these are slightly different than magnetic compass north-south directions) at an angle dictated by the geographic location and latitude of where they are to be installed. Typically, the angle of the solar array is set within a range of between site-latitude-plus 15 degrees and site-latitude-minus 15 degrees, depending on whether a slight winter or summer bias is desirable in the system. Many solar arrays are placed at an angle equal to the site latitude with no bias for seasonal periods.

This electrical charge is consolidated in the PV panel and directed to the output terminals to produce low voltage (Direct Current) - usually 6 to 24 volts. The most common output is intended for nominal 12 volts, with an effective output usually up to 17 volts. A 12 volt nominal output is the reference voltage, but the operating voltage can be 17 volts or higher much like your car alternator charges your 12 volt battery at well over 12 volts. So there's a difference between the reference voltage and the actual operating voltage.

CHAPTER 2
HISTORY

William Grylls Adams and his student, Richard Evans Day, discovered that an electrical current could be started in selenium solely by exposing it to light, they felt confident that they had discovered something completely new. Werner von Siemens, a contemporary whose reputation in the field of electricity ranked him alongside Thomas Edison, called the discovery "scientifically of the most far-reaching importance." This pioneering work portended quantum mechanics long before most chemists and physicist had accepted the reality of atoms. Although selenium solar cells failed to convert enough sunlight to power electrical equipment, they proved that a solid material could change light into electricity without heat or without moving parts.

In spring 1953, while researching silicon for its possible applications in electronics, Gerald Pearson, an empirical physicist at Bell Laboratories, inadvertently made a solar cell that was far more efficient than solar cells made from selenium. Two other Bell scientists - Daryl Chapin and Calvin Fuller - refined Pearson's discovery came up with the first solar cell capable of converting enough of the sun's energy into power to run everyday electrical equipment. Reporting the Bell discovery, The New York Times praised it as "the beginning of a new era, leading eventually to the realization of harnessing the almost limitless energy of the sun for the uses of civilization

During the first years after the discovery of the silicon solar cell, its prohibitive cost kept it out of the electrical power market. Desperate to find commercial outlets for solar cells, novelty items such as toys and radios run by solar cells were manufactured and sold as this advertisement illustrates Although technical progress of silicon solar cells continued at breakneck speed - doubling their efficiency in eighteen months - commercial success eluded the Bell solar cell. A one-watt cell cost almost $300 per watt in 1956 while a commercial power plant cost 50 cents a watt to build at that time. The only demand for silicon solar cells came from radio and toy manufacturers to power miniature ships in wading pools, propellers of model DC-4's, and beach radios
Hoffman Electronics, the leading manufacturer of silicon solar cells in the 1950s and 1960s, showed a variety of space satellites powered by the sun in a company brochure.

Despite solar cells' success in powering both American and Soviet satellites during the 1950s and early 1960s, many at NASA doubted the technology's ability to power its more ambitious space ventures. The agency viewed solar cells as merely a stopgap measure until nuclear power systems became available. But solar engineers proved the skeptics wrong. They met the increasing power demands by designing ever larger and more powerful solar cell arrays. Nuclear energy, in contrast, never powered more than a handful of satellites.

Hence, since the late 1960s, solar cells have become the accepted power source for the world's satellites. The increasing demand for solar cells in space opened an increasing and relatively large business for those manufacturing solar cells. Even more significantly, our past, present and future application of space would have been impossible if not for solar cells. The telecommunication revolution would never have gotten off the ground if not for solar powered satellites. Unbeknown to most, solar energy has played a crucial role in society's technological progress over the past forty years.

CHAPTER 3
BASIC PRINCIPLES

3.1 When Light Hits the Cell

When light, in the form of photons, hits our solar cell, its energy frees electron-hole pairs. Each photon with enough energy will normally free exactly one electron, and result in a free hole as well. If this happens close enough to the electric field, or if free electron and free hole happen to wander into its range of influence, the field will send the electron to the N side and the hole to the P side. This causes further disruption of electrical neutrality, and if we provide an external current path, electrons will flow through the path to their original side (the P side) to unite with holes that the electric field sent there, doing work for us along the way. The electron flow provides the current, and the cell's electric field causes a voltage. With both current and voltage, we have power, which is the product of the two.



Operation of a PV cell

3.2. Silicon in Solar Cells

A solar cell has silicon with impurities -- other atoms mixed in with the silicon atoms, changing the way things work a bit. We usually think of impurities as something undesirable, but in our case, our cell wouldn't work without them. These impurities are actually put there on purpose. Consider silicon with an atom of phosphorous here and there, maybe one for every million silicon atoms. Phosphorous has five electrons in its outer shell, not four. It still bonds with its silicon neighbor atoms, but in a sense, the phosphorous has one electron that doesn't have anyone to hold hands with. It doesn't form part of a bond, but there is a positive proton in the phosphorous nucleus holding it in place.

When energy is added to pure silicon, for example in the form of heat, it can cause a few electrons to break free of their bonds and leave their atoms. A hole is left behind in each case. These electrons then wander randomly around the crystalline lattice looking for another hole to fall into. These electrons are called free carriers, and can carry electrical current. There are so few of them in pure silicon, however, that they aren't very useful. Our impure silicon with phosphorous atoms mixed in is a different story. It turns out that it takes a lot less energy to knock loose one of our "extra" phosphorous electrons because they aren't tied up in a bond -- their neighbors aren't holding them back. As a result, most of these electrons do break free, and we have a lot more free carriers than we would have in pure silicon. The process of adding impurities on purpose is called doping, and when doped with phosphorous, the resulting silicon is called N-type ("n" for negative) because of the prevalence of free electrons. N-type doped silicon is a much better conductor than pure silicon is.

Actually, only part of our solar cell is N-type. The other part is doped with boron, which has only three electrons in its outer shell instead of four, to become P-type silicon. Instead of having free electrons, P-type silicon ("p" for positive) has free holes. Holes really are just the absence of electrons, so they carry the opposite (positive) charge. They move around just like electrons do.

3.3. N-type Plus P-type Silicon

The interesting part starts when you put N-type silicon together with P-type silicon. Remember that every PV cell has at least one electric field. Without an electric field, the cell wouldn't work, and this field forms when the N-type and P-type silicon are in contact. Suddenly, the free electrons in the N side, which have been looking all over for holes to fall into, see all the free holes on the P side, and there's a mad rush to fill them in.

Before now, our silicon was all electrically neutral. Our extra electrons were balanced out by the extra protons in the phosphorous. Our missing electrons (holes) were balanced out by the missing protons in the boron. When the holes and electrons mix at the junction between N-type and P-type silicon, however, that neutrality is disrupted. Do all the free electrons fill all the free holes? No. If they did, then the whole arrangement wouldn't be very useful. Right at the junction, however, they do mix and form a barrier, making it harder and harder for electrons on the N side to cross to the P side. Eventually, equilibrium is reached, and we have an electric field separating the two sides.

3.4. How Solar Cells Work

We probably seen calculators that have solar cells -- calculators that never need batteries, and in some cases don't even have an off button. As long as you have enough light, they seem to work forever. You may have seen larger solar panels -- on emergency road signs or call boxes, on buoys, even in parking lots to power lights. Although these larger panels aren't as common as solar powered calculators, they're out there, and not that hard to spot if you know where to look. There are solar cell arrays on satellites, where they are used to power the electrical systems.

You have probably also been hearing about the "solar revolution" for the last 20 years -- the idea that one day we will all use free electricity from the sun. This is a seductive promise: On a bright, sunny day, the sun shines approximately 1,000 watts of energy per square meter of the planet's surface, and if we could collect all of that energy we could easily power our homes and offices for free.


CHAPTER 4
COMPONENTS USED TO PROVIDE SOLAR POWER

The four primary components for producing electricity using solar power, which provides common 120 volt AC power for daily use are: Solar panels, charge controller, battery and inverter. Solar panels charge the battery, and the charge regulator insures proper charging of the battery. The battery provides DC voltage to the inverter, and the inverter converts the DC voltage to normal AC voltage. If 240 volts AC is needed, then either a transformer is added or two identical inverters are series-stacked to produce the 240 volts.

4.1. Solar Panels

The output of a solar panel is usually stated in watts, and the wattage is determined by multiplying the rated voltage by the rated amperage. The formula for wattage is VOLTS times AMPS equals WATTS. So for example, a 12 volt 60 watt solar panel measuring about 20 X 44 inches has a rated voltage of 17.1 and a rated 3.5 amperage.

4.2. Charge Controller

A charge controller monitors the battery's state-of-charge to insure that when the battery needs charge-current it gets it, and also insures the battery isn't over-charged. Connecting a solar panel to a battery without a regulator seriously risks damaging the battery and potentially causing a safety concern.



Charge controllers (or often called charge regulator) are rated based on the amount of amperage they can process from a solar array. If a controller is rated at 20 amps it means that you can connect up to 20 amps of solar panel output current to this one controller. The most advanced charge controllers utilize a charging principal referred to as Pulse-Width-Modulation (PWM) - which insures the most efficient battery charging and extends the life of the battery. Even more advanced controllers also include Maximum Power Point Tracking (MPPT) which maximizes the amount of current going into the battery from the solar array by lowering the panel's output voltage, which increases the charging amps to the battery - because if a panel can produce 60 watts with 17.2 volts and 3.5 amps, then if the voltage is lowered to say 14 volts then the amperage increases to 4.28 (14v X 4.28 amps = 60 watts) resulting in a 19% increase in charging amps for this example.

Many charge controllers also offer Low Voltage Disconnect (LVD) and Battery Temperature Compensation (BTC) as an optional feature. The LVD feature permits connecting loads to the LVD terminals which are then voltage sensitive. If the battery voltage drops too far the loads are disconnected - preventing potential damage to both the battery and the loads. BTC adjusts the charge rate based on the temperature of the battery since batteries are sensitive to temperature variations above and below about 75 F degrees.

4.3. Battery

The Deep Cycle batteries used are designed to be discharged and then re-charged hundreds or thousands of times. These batteries are rated in Amp Hours (ah) - usually at 20 hours and 100 hours. Simply stated, amp hours refers to the amount of current - in amps - which can be supplied by the battery over the period of hours. For example, a 350ah battery could supply 17.5 continuous amps over 20 hours or 35 continuous amps for 10 hours. To quickly express the total watts potentially available in a 6 volt 360ah battery; 360ah times the nominal 6 volts equals 2160 watts or 2.16kWh (kilowatt-hours). Like solar panels, batteries are wired in series and/or parallel to increase voltage to the desired level and increase amp hours.

The battery should have sufficient amp hour capacity to supply needed power during the longest expected period "no sun" or extremely cloudy conditions. A lead-acid battery should be sized at least 20% larger than this amount. If there is a source of back-up power, such as a standby generator along with a battery charger, the battery bank does not have to be sized for worst case weather conditions.

The size of the battery bank required will depend on the storage capacity required, the maximum discharge rate, the maximum charge rate, and the minimum temperature at which the batteries will be used. During planning, all of these factors are looked at, and the one requiring the largest capacity will dictate the battery size.

One of the biggest mistakes made by those just starting out is not understanding the relationship between amps and amp-hour requirements of 120 volt AC items versus the effects on their DC low voltage batteries. For example, say you have a 24 volt nominal system and an inverter powering a load of 3 amps, 120VAC, which has a duty cycle of 4 hours per day. You would have a 12 amp hour load (3A X 4 hrs=12 ah). However, in order to determine the true drain on your batteries you have to divide your nominal battery voltage (24v) into the voltage of the load (120v), which is 5, and then multiply this times your 120vac amp hours (5 x 12 ah). So in this case the calculation would be 60 amp hours drained from your batteries - not the 12 ah. Another simple way is to take the total watt-hours of your 120VAC device and divide by nominal system voltage. Using the above example; 3 amps x 120 volts x 4 hours = 1440 watt-hours divided by 24 DC volts = 60 amp hours.

Lead-acid batteries are the most common in PV systems because their initial cost is lower and because they are readily available nearly everywhere in the world. There are many different sizes and designs of lead-acid batteries, but the most important designation is that they are deep cycle batteries. Lead-acid batteries are available in both wet-cell (requires maintenance) and sealed no-maintenance versions. AGM and Gel-cell deep-cycle batteries are also popular because they are maintenance free and they last a lot longer.






CHAPTER 5
APPLICATIONS


IN VEHICLES





In automobiles the components used are
1) solar panel
2) charge controller
3) battery
4) traction motor



Solar panel
Solar panel consists of; many solar cells are connected in series to form a large Panel .it is placed on the top of the vehicles

Charge controller
Charge controller regulates the charging of battery. it acts as a stabiliser. It is too risk connecting battery to a solar panel without charge controller. It causes battery damage

Battery
Battery used in the solar powered vehicles are nickel hydrogen batteries. Efficient performance



Using an Inverter


An inverter is a device which changes DC power stored in a battery to standard 120/240 VAC electricity (also referred to as 110/220). Most solar power systems generate DC current which is stored in batteries. Nearly all lighting, appliances, motors, etc., are designed to use ac power, so it takes an inverter to make the switch from battery-stored DC to standard power (120 VAC, 60 Hz). In an inverter, direct current (DC) is switched back and forth to produce alternating current (AC). Then it is transformed, filtered, stepped, etc. to get it to an acceptable output waveform. The more processing, the cleaner and quieter the output, but the lower the efficiency of the conversion. The goal becomes to produce a waveform that is acceptable to all loads without sacrificing too much power into the conversion process.

Inverters come in two basic output designs - sine wave and modified sine wave. Most 120VAC devices can use the modified sine wave, but there are some notable exceptions. Devices such as laser printers which use triacs and/or silicon controlled rectifiers are damaged when provided mod-sine wave power. Motors and power supplies usually run warmer and less efficiently on mod-sine wave power. Some things, like fans, amplifiers, and cheap fluorescent lights, give off an audible buzz on modified sine wave power. However, modified sine wave inverters make the conversion from DC to AC very efficiently. They are relatively inexpensive, and many of the electrical devices we use every day work fine on them.

Sine wave inverters can virtually operate anything. Your utility company provides sine wave power, so a sine wave inverter is equal to or even better than utility supplied power. A sine wave inverter can "clean up" utility or generator supplied power because of its internal processing.

Inverters are made with various internal features and many permit external equipment interface. Common internal features are internal battery chargers which can rapidly charge batteries when an AC source such as a generator or utility power is connected to the inverter's INPUT terminals. Auto-transfer switching is also a common internal feature which enables switching from either one AC source to another and/or from utility power to inverter power for designated loads. Battery temperature compensation, internal relays to control loads, automatic remote generator starting/stopping and many other programmable features are available.



Most inverters produce 120VAC, but can be equipped with a step-up transformer to produce 120/240VAC. Some inverters can be series or parallel "stacked-interfaced" to produce 120/240VAC or to increase the available amperage.

IN SPACE VEHICLES


Electrical power is the most critical resource for the International Space Station (ISS) because it allows the crew to live comfortably, to safely operate the station, and to perform scientific experiments. So, whether it is used to power the life support system, run a furnace that makes crystals, manage a computerized data network, or operate a centrifuge, electricity is essential. Since the only readily available source of energy for spacecraft is sunlight, NASA Glenn Research Center has pioneered, and continues to develop, technologies to efficiently convert solar energy to electrical power. One method of harnessing this energy, called photovoltaics, uses purified silicon solar cells to directly convert light to electricity. Large numbers of cells are assembled in arrays to produce high power levels.

However, a spacecraft orbiting the Earth is not always in direct sunlight. Therefore, the ISS relies on nickel-hydrogen rechargeable batteries to provide continuous power during the "eclipse" part of the orbit. The batteries ensure that the station is never without power to sustain life-support systems and experiments. During the sunlit part of the orbit, the batteries are recharged. The process of collecting sunlight, converting it to electricity, and managing and distributing this electricity builds up excess heat that can damage spacecraft equipment. This heat must be eliminated for reliable operation of the Space Station in orbit. The ISS power system uses radiators to dissipate the heat away from the spacecraft. The radiators are shaded from sunlight and aligned toward the cold void of deep space.

The power management and distribution subsystem disburses power at 160 volts of direct current (abbreviated as "dc") around the station through a series of switches. These switches have built-in microprocessors that are controlled by software and are connected to a computer network running throughout the station. To meet operational requirements, dc-to-dc converter units step down and condition the voltage from 160 to 120 volts dc to form a secondary power system to service the loads. The converters also isolate the secondary system from the primary system and maintain uniform power quality throughout the station.

Array Design

The International Space Station's electrical power system (EPS) will use eight photovoltaic solar arrays to convert sunlight to electricity. Each of the eight solar arrays will be 112 ft long by 39 ft wide. With all eight arrays installed, the complete Space Station is large enough to cover a football field. Because the Space Station needs very high power levels, the solar arrays will require more than 250,000 silicon solar cells. NASA has developed a method of mounting the solar arrays on a "blanket" that can be folded like an accordion for delivery to space. Once in orbit, astronauts will deploy the blankets to their full size. Gimbals will be used to rotate the arrays so that they face the Sun to provide maximum power to the Space Station. The complete power system, consisting of U.S. and Russian hardware, will generate 110 kW (kilowatts) total power, about as much as 55 houses would typically use.

"Batteries Included"

The station is in an orbit with an altitude of 250 statute miles with an inclination of 51.6 degrees. As the station travels, the Earth will shadow the ISS solar arrays from the Sun for up to 36 minutes of each 92-minute orbit. To avoid an interruption in the power supply, NASA Glenn developed rechargeable nickel-hydrogen batteries that can store electrical energy gathered during the sunlit portion of the orbit and discharge electrical energy for use during the eclipse portion. Thirty-eight cells are packaged together in series with monitoring instrumentation (temperature and pressure) inside an enclosure called an orbital replacement unit or "ORU." The enclosure is designed to allow simple removal and replacement while in orbit. Since the ISS will never return to the ground, all repairs must be made in orbit. The batteries are not the only ORU's on the ISS; in fact, every item of ISS hardware that will require maintenance or replacement has been designed as an ORU. The batteries are expected to last 5 to 6 years


CHAPTER 6
ADVANTAGES

 Cheap when compared to other engine driven vehicles
 Cost of production is very low when compared to other vehicles
 Solar powered vehicles have more engine life than other vehicles
 Exhaust/pollution is zero when compared to petrol or diesel engines
 Cost of running is very low
 No need of refueling
 No need of extra maintenance such as engine oil chaging, coolant etc


CHAPTER 7
CONCLUSION

 Solar power can be used for many purposes such as solar powered vehicles, solar powered house hold equipments.etc
 In very remote locations it may be the only practical solution since reliable power can be provided virtually anywhere. In addition, more and more residential and commercial customers are realizing the benefits of utilizing solar power for electricity to offset their utility-supplied energy consumption, to provide back up power or to operate independent of the utility grid. Solar power can be a solution.


REFERENCES

1. solarvehicles.com
2. googlesearch.com
3. howstuffworks.com
4. http://space-power.grc.nasa.gov/ppo/projects/iss/