Sustainable racing utilizing solar powRer

Sustainable racing utilizing solar powerSeminar presented by, CONTENTSENERGYRenewable energy is an alternative to fossil fuels

Solar technologies are extremely promising

It has increasing output efficiency and the capability to be used in a variety of locations

Solar photovoltaic (PV) systems are perfect for maximizing the energy production FUEL IN RACING CARSMajority are powered by internal combustion engines utilizing fossil-based fuelSome utilize electricity or hydrogen as energy carriersSuch vehicles include: low energy density electric vehicles competing under regulations set by Green power in the UK higher energy density vehicles including those in the recently started EV Cup.ADVANTAGESIt can utilize the kinetic energy lost while braking to charge batteries or super capacitorsIt can be later expended in acceleration or overcoming the non-conservative forces Non conservative forces-aerodynamic drag and rolling resistance This is been exploited in hybrid road cars as well as the KERS which used in Formula OneSUSTAINABLE RACINGSolar car racing-races ofelectric vehicles -powered bysolar energyObtained from solar panels on the surface of the car The two most notable solar car distance races are:THE WORLD SOLAR CHALLENGETHE NORTH AMERICAN SOLAR CHALLENGEContested by a variety of university, corporate teamsThese races are often sponsored by government or educational agencies, and businesses such as Toyota, to promote renewable energy sourcesWORLD SOLAR CHALLENGEMost significant and longest runningHeld every two yearsIt requires competitors to cross the Australian continent using only the power of the sun The World Solar Challenge is currently the pinnacle of solar car competition and ideal venue to demonstrate creative thinking and new transport technology.

SYSTEMS IN SOLAR CARElectrical system

controls the power entering and leaving the systembattery pack stores surplus solar energy produced when the vehicle is stationary or travelling slowly or downhilluse a range of batteries includinglead acid batteries, nickel-metal hydride batteries , nickel-cadmium batteries ,lithium ion batteries and lithium polymer batteries

Mechanical systems

designed to keep friction and weight to a minimum while maintaining strength and stiffnessnormally use aluminium, titanium and composites to provide a structure that meets strength and stiffness requirements while being fairly lightsteel is used for some suspension parts usually have three wheels, but some have four Three-wheelers usually have two front wheels and one rear wheel: the front wheels steer and the rear wheel follows.have a wide range of suspension because of varying bodies and chassis must meet rigorous standards for brakes: disc brakesare most commonly used due to their good braking ability and ability to adjust. mechanical and hydraulic brakes are both widely used.brake pads or shoes are typically designed to retract to minimize brake drag the major design factors for steering systems are efficiency, reliability and precision alignment to minimize tire wear and power loss. Solar array

consists of hundreds or thousands of photovoltaic solar cells converting sunlight into electricity in cars we often use polycrystalline silicon, mono crystalline silicon, or gallium arsenidecells are wired into strings while strings are often wired to form a panelpanels have voltages close to the nominal battery voltage cells are encapsulated to protect them from the weather and breakageacts like many very small batteries all hooked together in series. The total voltage produced is the sum of all cell voltagesAerodynamics

Aerodynamic drag is the main source of losses aerodynamic drag of a vehicle is the product of the frontal area and itsCdfor most solar cars the frontal area is 0.75 to 1.3 m2,Cdas low as 0.10 have been reported, 0.13 is more typical

Mass

vehicle's mass is a significant factor

light vehicle generates lessrolling resistance and will need smaller lighterbrakesand othersuspensioncomponents

this is thevirtuous circle when designing lightweight vehicles

Rolling resistance

Rolling resistance can be minimised by using right tiresinflated to the right pressure,correctly alignedminimising the weight of the vehicle.Performance equation

the design of a solar car is governed by certain work equation which can be usefully simplified to the performance equation: h{h b Ev/x+P}={WCrr1v+(1/2)rCdAv3}

left hand side represents the energy input into the car (batteries and power from the sun) right hand side is the energy needed to drive the car along the race route (overcoming rolling resistance, aerodynamic drag, going uphill and accelerating)

COMPUTER SIMULATION OF SOLAR CAR BODY DESIGN17SYMBOL DESCRIPTION FORD AUSTRALIA AURORA AURORA AURORAYEAR 1987 1993 1999 2007 Motor, controller and drive train efficiency (decimal) 0.82 0.80 0.97 0.97b Watt-hour battery efficiency (decimal) 0.82 0.92 0.82 1.00 E Energy available in the batteries (joules) 1.2e7 1.8e7 1.8e7 1.8e7P Estimated average power from the array (1) (watts) 918 902 1050 972xRace route distance (meters) 3e6 3.007e6 3.007e6 3.007e6W Weight of the vehicle including payload (newtons) 2690 2950 30002400Crr1 First coefficient of rolling resistance (non-dimensional) 0.0060 0.0050 0.0027 0.0027Crr2 Second coefficient of rolling resistance (newton-seconds per meter) 0 0 0 0N Number of wheels on the vehicle (integer) 4 3 3 3 Air density (kilograms per cubic meter) 1.22 1.22 1.22 1.22Cd Coefficient of drag (non-dimensional) 0.26 0.133 0.10 0.10A Frontal area (square meters) 0.70 0.75 0.75 0.76H Total height that the vehicle will climb (meters) 0 0 0 0Na Number of times the vehicle will accelerate in a race day (integer) 4 4 4 4G Local acceleration due to gravity variable (meters per second squared) 9.81 9.81 9.81 9.81V Calculated average velocity over the route (meters per second) 16.8 20.3 27.2 27.1Calculated average speed 60.5 73.1 97.9 97.6Actual race speed km/h 44.8 70.1 73 85

Energy consumption

optimizing energy consumption is of prime importanceso continues monitoring and optimisation is required for the vehicles energy parameters race speed optimization programs that continuously update the team on how fast the vehicle should be travelling, for this some teams employtelemetry that relays vehicle performance data

AURORA 101it represents a high end entrantmass minimization is done with much of the body structure being carbon fiber and the motor housing cast from magnesiumto minimize rolling resistance Michelin developed 16-inch, 185/60 dedicated tyres with low rolling resistance coefficients maximized the projected surface area exposed to the sun minimize the aerodynamic dragas speeds have increased, the shapes used including Aurora 101, have integrated the solar collection surfaces into the main body, leading to a lower aerodynamic drag but providing less solar collection.

About the race

the requirement to have a surface area exposed to the sun results in considerable wetted area, which generates skin friction dragto minimize this drag component the profile of the Aurora 101 is shaped to keep the state of the boundary layer laminar for the WSC the average solar density is~1000 W/m2 which varies during the daymost teams will have < 1.5 kW solar array output and energy management is extremely important as the leading cars may finish the event within minutes of each othersolar racing cars are examples of very high operational efficiency, requiring less than 10% of the energy used by a conventional passenger car to travel at highway speed. The Aurora 101 specifications Top speed > 150 km/hDaily range > 700 km at highway speedPower consumption @ 100 km/h < 1400 WPower consumption @ 150 km/h < 5500 WWeight < 140 kg including batteries4.1 m length, 1.8 m width and 1.1 m height6 m2 of monocrystalline silicon solar cells22 kg of Lithium polymer batteriesDrag coefficient x area, 0.106 m2Electric wheel motor efficiency @ 100 km/h > 97%Total drive train efficiency @ 100 km/h > 90%

FSAE ELECTRIC RACING

this class of racing arose out of the FSAE competition which traditionally used 600cc four stroke IC enginesit is the largest student- based competition in the world with teams competing at events in America, UK, Brazil, Italy, Germany, Australia and Japan, with more events plannedthe cars are designed for short, twisty circuitsaverage speeds of 40 t0 50 km/hr and maximum speeds of the order of 100 km/hrthe highest scoring event the Endurance Eventthe second highest driving event Autocross Eventthe first all-electric FSAE car was built by RMIT University in 2009this vehicle was followed by R10E

in the intervening time between R09E and R10E battery technology had improvedthis car used Dow Kokam Lithium Polymer batteriesDetails are given belowMax charged capacity = 13.4kWh (80Ah)Nominal voltage = 155.4V, peak power = 150kWNumber of cells = 84 (2x42), total mass = 82kgCharge time = 5-6 hoursAdvanced Elithion BMS (monitors temp and voltage during charge/discharge) and cell balancing

most recent vehicle R11E carbon- fiber tub with a small steel space-frame chassisreduced the overall weight of the car to 246 Kgenergy management is crucialsimulation of vehicle parameters for minimum lap times achieved by maximizing the longitudinal and lateral accelerations and decelerations around a circuit are done utilizing concepts such as G-G diagramsplanned regenerative braking and an electronic differential were not implemented due to the unexpected complexity.

CONCLUDING REMARKS

for the WSC the circuit is long and straight thus there is no need for regenerative braking, in contrast is a FSAE circuit short and tortuously twisty, resulting in cars being in a continual state of acceleration and deceleration.lending road vehicles to more easily benefit from regenerative brakes. Despite the great benefitsit poses formidable challenges; the energy transfer has to be done in very short timesso systems have to cope with high power densities that are rapidly reversingdue to mass transfer under the heavy braking most energy has to be scavenged from the front wheels so brakes-generators should be positioned hereso additional mass, complexity and lack of reliability REFERENCES

http://www.greenpower.co.ukhttp://www.evcup.com/http://www.formulastudent.de/uploads/media/FSE Rules 2010 v1.1.pdfhttp://rmit.net.au/browse;ID=2su62rct92on#_RMIT Energy Carewww.wikipedia.org