Solar Vehicles: 112115062-ts Harika 112115063-v Chetan Naveen

SOLAR VEHICLES 112115062- Ts Harika

112115063-V Chetan naveen

Introduction • The face of the automotive industry is being reshaped by concerns over oil supplies, international policy and fuel costs. A wide variety of hybrid technologies are now available including discussion of hydrogen possibilities. The solar powered car, one of the oldest alternative energy vehicles, has many applications to the emerging electric vehicle market. • Automotive consumers are growing increasingly more interested in highly fuel efficient vehicles, environmentalists are concerned over vehicle emissions, and politicians are fighting to ease foreign relations and maintain international oil trade. The effects of the combustion engine automobile are diverse and widespread. Research in ethanol, hydrogen, biodiesel and electric vehicles aims to improve energy efficiencies while decreasing pollution and dependency on foreign oil.

• The first solar car invented was a tiny 15-inch vehicle created by William G. Cobb of General Motors. Called the Sunmobile, Cobb showcased the first solar car at the Chicago Powerama convention on August 31, 1955. The solar car was made up 12 selenium photovoltaic cells and a small Pooley electric motor turning a pulley which in turn rotated the rear wheel shaft. The first solar car in history was obviously too small to drive.

History

• Now, let's jump to 1962 when the first solar car that a person could drive was demonstrated to the public. The International Rectifier Company converted a vintage model 1912 Baker electric car to run on photovoltaic energy in 1958, but they didn't show it until 4 years later. Around 10,640 individual solar cells were mounted to the rooftop of the Baker to help propel it. • In 1977, Alabama University professor Ed Passereni built the Bluebird solar car, which was a prototype full scale vehicle. The Bluebird was supposed to move from power created by the photovoltaic cells only without the use of a battery. The Bluebird was exhibited in the Knoxville, TN 1982 World's Fair. • Between 1977 and 1980 (the exact dates are not known for sure), at Tokyo Denki University, professor Masaharu Fujita first created a solar bicycle, then a 4-wheel solar car. The car was actually two solar bicycles put together.

History • At the engineering department at Tel Aviv University in Israel, Arye Braunstein and his colleagues created a solar car in 1980. The solar car had a solar panel on the hood and on the roof of the Citicar comprised of 432 cells creating 400 watts of peak power. The solar car used 8 batteries of 6 volts each to store the photovoltaic energy. • In 1981 Hans Tholstrup and Larry Perkins built a solar powered racecar. In 1982, the pair became the first to cross a continent in a solar car, from Perth to Sydney, Australia. Tholstrup is the creator of the World Solar Challenge in Australia. • In 1984, Greg Johanson and Joel Davidson invented the Sunrunner solar race car. The Sunrunner set the official Guinness world record in Bellflower, California of 24.7 mph. In the Mojave Desert of California and final top speed of 41 mph was officially recorded for a "Solely Solar Powered Vehicle" (did not use a battery). The 1986 Guinness Book of World Records publicized these official records. • The GM Sunraycer in 1987 completed a 1,866 mile trip with an average speed of 42 mph. Since this time there have been many solar cars invented at universities for competitions such as the Shell Eco Marathon. There is also a commercially available solar car called the Venturi Astrolab. Time will only tell how far the solar car makes it with today's and tomorrow's technology.

The first solar car invented, a tiny 15inch vehicle created by William G. Cobb of General Motors. Called as the Sunmobile

Solar Plane

It’s the first solar-powered plane to make a cross-country trip across the United States. Now Solar Impulse is attempting to fly across the entire globe. The plane, which was equipped with 12,000 solar cells and four electrically-powered propellers, was the first aircraft running on renewable energy that was able to fly non-stop for 24 hours. It carried batteries that were charged during the day, so the plane would be able to fly at night.

Solar Shuttle

Built in 2000, the Hamburg Solarshuttle is the world’s biggest Solarferry, carrying up to 120 passengers. The boat's solar generator eliminates the production of 10,040 lbs of CO2, 23.3 lbs of NOX and 54.8 lbs of SO4 per year compared to a conventional diesel powered vessel of similar size.

Solar Tricycle

With a maximum speed of 20kmph travels 40-45km at a stretch after charging for about 3.5-4hrs.

Solar Bus

The world’s first solar cell-equipped public bus introduced in Okayama City. It is a hybrid diesel-electric vehicle whose rooftop solar cells generate 798 watts, powering the interior LED lights. In the absence of sun, solar power stored in a battery will keep the lights on for nine hours.

Solar Train

The train rooftops have been fitted with custom-built curved solar panels to charge the onboard batteries, which also draw on a regenerative braking system said to recapture around 25 percent of energy the train uses to accelerate. The batteries can also be charged at the platform thanks to a large rooftop solar array on the storage shed. One diesel engine is left onboard as a backup.

Components of a solar car

• • • • • • • •

SOLAR ARRAY POWER TRACKERS ELECTRIC MOTOR SPEED CONTROLLER CHASSIS SUSPENSION SYSTEM BATTERY WHEEL

Solar cell • A solar cell converts solar energy to electrical energy. Photons in sunlight provide the energy that moves electrons from one layer of a semiconducting metallic wafer to another. The movement of the electrons creates a current. Solar cells are devices which convert solar energy directly into electricity. The most common solar cells function by the photovoltaic effect. Photo- means light and -voltaic means electrical current or electricity.

Solar Array • A solar array can be defined as solar panels arranged in a group to capture maximum amount of sun light to convert it into usable electricity. The idea of Solar Array came into being when it was conceived that the power produced by a solar panels singly was not sufficient for domestic or commercial purpose. Many such solar modules are linked together to form a Solar Array. • The power produced by the solar array varies depending on the weather, the sun's position in the sky, and the solar array itself. On a bright, sunny day at noon, a good solar car solar array will produce well over 1000 watts (1.3 hp) of power. The power from the array is used either to power the electric motor or stored in the battery pack for later use

Working of an solar array • A solar cell is an electronic device which catches the sunlight and turns it into the electricity directly. These cells are of the same size as the palm of an adult ( blue-black and octagonal).the solar cells (photovoltaic cells) are usually bundled together to create a big unit of solar modules and is called as solar panels. Solar cells have germanium PN junction diode and silicon with a glass window on the top surface layer of P-type. The top surface layer of P-type material is thin so that the incident light photon may quickly reach the PN junction. • Sunlight may generally consist of photons, and these photons have a different amount of energy corresponding to various wavelengths of light. When these photons in sunlight hit the solar cells, they are either reflected or absorbed. If the photon gets absorbed, its energy gets transferred to an electron in the cells' atom. Then the electron escapes from its normal position, thus causing a hole. Due to these holes and electrons, there is a production of current. • The process is known as the photovoltaic effect. The current generated is collected by wiring the individual solar panels together.

Types of Solar Array • Horizontal. This most common arrangement gives most overall power during most of the day in low latitudes or higher latitude summers and offers little interaction with the wind. Horizontal arrays can be integrated or be in the form of a free canopy. • Vertical. This arrangement is sometimes found in free standing or integrated sails to harness wind energy . Useful solar power is limited to mornings, evenings, or winters and when the vehicle is pointing in the right direction. • Adjustable. Free solar arrays can often be tilted around the axis of travel in order to increase power when the sun is low and well to the side. An alternative is to tilt the whole vehicle when parked. Two-axis adjustment is only found on marine vehicles, where the aerodynamic resistance is of less importance than with road vehicles. • Integrated. Some vehicles cover every available surface with solar cells. Some of the cells will be at an optimal angle whereas others will be shaded. • Trailer. Solar trailers are especially useful for retrofitting existing vehicles with little stability, e.g. bicycles. Some trailers also include the batteries and others also the drive motor. • Remote. By mounting the solar array at a stationary location instead of the vehicle, power can be maximised and resistance minimized. The virtual grid-connection however involves more electrical losses than with true solar vehicles and the battery must be larger.

Power Trackers • Power trackers condition the electricity coming from the solar array to maximize the power and deliver it either to the batteries for storage or to the motor controller for propulsion. When the solar array is charging the batteries, the power trackers help to protect the batteries from being damaged by overcharging. The number of power trackers used in a solar car varies with each team's design. Power trackers can be very lightweight and commonly reach efficiencies above 95%.

Electric Motor • An electric motor is the basic and the most important part of a solar car. It should work with optimal power and the efficiency should be high. An electric motor is a device using electrical energy to produce mechanical energy, nearly always by the interaction of magnetic fields and current-carrying conductors.

Speed Controller • The purpose of a motor speed controller is to take a signal representing the demanded speed, and to drive a motor at that speed. The controller may or may not actually measure the speed of the motor

• It controls the speed by controlling the power flow as shown in the adjacent representation

Chassis • The primary challenge in developing an effective solar car chassis is to maximize the strength and safety, but minimize the weight. However, safety is a primary concern and the chassis must meet stringent strength and safety requirements. Different Body Shapes • Unified aero body and panel • Fixed or tilting, flat panels with a separate driver cab • Catamaran shape • uniquely designed shape Different Chassis structures • Tubular metal spaceframe • Carbon fiber composite monocoque • Some use aluminium and steel spaceframes

Suspension system • Besides enhancing driver comfort, the suspension can potentially enhance the responsiveness or stability of the solar car. • The majority of solar cars utilize a short-long arm style suspension, also known as double wishbone for the front wheels. • The rear wheels often also employ the double wishbone style suspension for four wheeled solar cars, while three wheeled cars usually employ a derivative of the trailing arm style suspension.

• Most solar cars use suspension components machined from billet aluminum.

Points to consider when designing a solar car • The car should be designed in order to maximize the area exposed to sun light in order to achieve maximum power. • The car shape should be so-called an aerodynamic shape in order to achieve minimum wind resistance, or the so-called drag force. • The car should be as light as possible, because the power expected from the solar cells is not that much. In addition, most of this power will be utilized to overcome friction and drag.

Aerodynamics and Drag • A body immersed in a flowing fluid is acted on by both pressure and viscous forces from the flow. The sum of the forces (pressure, viscous, or both) that acts normal to the free-stream direction is the lift, and the sum of that acts parallel to the free-stream direction is defined as the drag. These definitions are perhaps one of the famous conclusions of the famous Bernoulli’s equation, which is one of the fundamental laws governing the motion of fluids. It relates an increase in flow velocity to a decrease in pressure and vice versa. Bernoulli's principle is used in aerodynamics to explain the lift of an airplane wing in flight. A wing is so designed that air flows more rapidly over its upper surface than its lower one, leading to a decrease in pressure on the top surface as compared to the bottom. The resulting pressure difference provides the lift that sustains the aircraft in flight. The velocity of a wind that strikes the bluff surface of a building is close to zero near its wall. According to Bernoulli's principle, this would lead to a rise in pressure relative to the pressure away from the building, resulting in wind forces that the structures must be designed to withstand. • Another important aspect of aerodynamics is the drag, or resistance, acting on solid bodies moving through air. The drag forces exerted by the air flowing over the airplane, for example, must be overcome by the thrust force developed by either the jet engine or the propellers. These drag forces can be significantly reduced by streamlining the body. For bodies that are not fully streamlined, the drag force increases approximately with the square of the speed as they move rapidly through the air. The power required, for example, to drive an automobile steadily at medium or high speeds is primarily absorbed in overcoming air resistance.

Aerodynamics and Drag • The following examples illustrate the importance of considering drag when designing a car • FDRAG = (1/2)* 𝑐 𝑑 *𝐴𝐶𝑟𝑜𝑠𝑠 *ρ*𝑣 2 Where 𝑐 𝑑 is the coefficient of drag of the vehicle, 𝐴𝐶𝑟𝑜𝑠𝑠 is it’s frontal area in square feet ,ρ is a constant that accounts for the air mass density and V is the vehicle’s speed. To minimize drag for any given 𝑐 𝑑 , the coefficient of drag, and 𝐴𝐶𝑟𝑜𝑠𝑠 , it’s frontal area must be minimized.

Aerodynamics and Drag • The drag force becomes increasingly noticeable at speeds of above 40 km/h due to it being proportional to the square of the speed. Because batteries provide only 1% as much power per weight as gasoline, optimizing for either high-speed or long-range performance goals, requires that one keeps this critical performance factor foremost in mind. As it is noticeable from the adjacent figure the more streamlined the shape of the car the lower is 𝑐 𝑑 . It is estimated that for conventional car designs, the body’s rear area contributes more than 33% of 𝑐 𝑑 by itself, followed by the wheel wells at 2%, the underbody area at 14%, the front body area at 12%, projections(minors, drip rails, window recesses etc.) at 7%, and engine compartment and skin friction at 6% each.

Different designs generally used in solar cars • The design required is selected considering the factors mentioned in the previous slides and also the type and efficiency of the solar panels being used and the other restrictions and conditions under which the vehicle is being built

Batteries • The batteries store energy from the solar array and make them available for the motor’s use. Batteries that are commonly used in solar cars are Lead-acid batteries, Li-ion batteries, Ni-MH batteries, Ni-Cd batteries, Flooded-cell batteries and Gel-cell batteries.

TILTING PANEL

• The suns rays may not fall on the solar panels directly, as the sun moves from east to west according to the time. Hence tilting panels are used so that by tilting the solar panels, we can allow the suns rays to fall directly on the panels.

Advantages of a solar vehicle • • • •

A solar car has zero harmful emissions hence it is eco-friendly. It uses renewable source of energy which can never be exhausted. They work silently hence no noise pollution. As the life span of solar modules is more than 30 years the life span of a solar car is also more when compared to a regular car. • The fuel used is sunlight which is unlimited and free of cost.

Disadvantages of a solar vehicle • • • •

A solar car provides less speed. It is expensive. Maintenance cost of a solar car is high. Due to their light weight body and small size they are considered to be dangerous in case an accident happens. • Performance of a solar car will be affected in unfriendly weather conditions, like on a cloudy day or when night falls.

Applications of a solar car • Solar cars are used in industries where small vehicles are used to perform light weight conveys work from one place to another. • These vehicles are primarily manufactured for racing competitions and engineering exercises. • It is used as day to day transportation device. • They are used in places where, fuel based vehicles are banned due to production of pollution and noise. • They are often used and sponsored by government agencies.

CO2 Emissions

Pounds of CO2 per passenger mile: • Gas cars: 0.9 pounds per passenger mile • Electric Vehicles: 0.5 pounds per passenger mile • Public Transportation (Buses and Trains): 0.2pounds per passenger mile