Solar car racing
Solar car racing refers to competitive races of electric vehicles which are powered by solar energy obtained from solar panels on the surface of the car (solar cars). The first solar car race was the Tour de Sol in 1985 which led to several similar races in Europe, US and Australia. Such challenges are often entered by universities to develop their students' engineering and technological skills, but many business corporations have entered competitions in the past. A small number of high school teams participate in solar car races designed exclusively for high school students.
Distance races
The two most notable solar car distance (overland) races are the World Solar Challenge and the American Solar Challenge. They are contested by a variety of university and corporate teams. Corporate teams participate in the races to give their design teams experience of working with both alternative energy sources and advanced materials. University teams participate in order to give their students experience in designing high technology cars and working with environmental and advanced materials technology. These races are often sponsored by government or educational agencies,[citation needed] and businesses such as Toyota[1] keen to promote renewable energy sources.
Support
The cars require intensive support teams similar in size to professional motor racing teams. This is especially the case with the World Solar Challenge where sections of the race run through very remote country. The solar car will travel escorted by a small caravan of support cars. In a long distance race each solar car will be preceded by a lead car that can identify problems or obstacles ahead of the race car. Behind the solar car there will be a mission control vehicle from which the race pace is controlled. Here tactical decisions are made based on information from the solar car and environmental information about the weather and terrain. Behind the mission control there might be one or more other vehicles carrying replacement drivers and maintenance support as well as supplies and camping equipment for the entire team.
World Solar Challenge
This race features a field of competitors from around the world who race to cross the
In 2013 the organisers of the event introduced the Cruiser Class to the World Solar Challenge, designed to encourage contestants to design a "practical" solar powered vehicle. This race requires that vehicles have four wheels and upright seating for passengers, and is judged on a number of factors including time, payload, passenger miles, and external energy use.
American Solar Challenge
The American Solar Challenge, previously known as the 'North American Solar Challenge' and 'Sunrayce', features mostly collegiate teams racing in timed intervals in the United States and Canada. The annual Formula Sun Grand Prix track race is used as a qualifier for ASC.
The American Solar Challenge was sponsored in part by several small sponsors. However, funding was cut near the end of 2005, and the NASC 2007 was cancelled. The North American solar racing community worked to find a solution, bringing in Toyota as a primary sponsor for a 2008 race.[4][5] Toyota has since dropped the sponsorship. The last North American Solar Challenge was run 2016, from Brecksville, OH to Hot Springs, SD. The race was won by the University of Michigan. Michigan has won the race the last 6 times it has been held.
The Solar Car Challenge (Highschool)
The Solar Car Challenge is an annual event that fosters education and innovation in renewable energy by engaging high school students in the design, engineering, and racing of solar-powered vehicles. Founded in 1989[6] by Dr. Lehman Marks, the challenge has grown to become a premier educational program, combining science, technology, engineering, and mathematics (STEM) principles with hands-on experience. Participants are tasked with building and racing solar cars, allowing them to apply theoretical knowledge to practical problems while promoting sustainable technology and teamwork.
Held over several days, the Solar Car Challenge typically includes a cross-country race or a track event, depending on the year. The event draws teams from across the United States and occasionally international participants, fostering a spirit of friendly competition and collaboration. Beyond the race itself, the Solar Car Challenge provides extensive educational resources, workshops, and mentorship to help students succeed. This competition not only highlights the potential of solar energy but also inspires the next generation of engineers, scientists, and environmentally-conscious citizens.
South African Solar Challenge
The
Carrera Solar Atacama
The Carrera Solar Atacama is the first solar-powered car race of its kind in Latin America; the race covers 2,600 km (1,600 mi) from Santiago to Arica in the north of Chile. The race's founder, La Ruta Solar, claims it is the most extreme of the vehicular races due to the high levels of solar radiation, up to 8.5 kWh/m2/day, encountered while traversing the Atacama Desert, as well as challenging participating teams to climb 3,500 m (11,500 ft) above sea level. After the 2018 race, La Ruta Solar organized its next edition for 2020, but it never came to be. In the end of 2019, the organization struggled with funding and decided to cancel the race. A few months later they declared bankruptcy.[7]
Other races
- [ESVC] Electric-Solar Vehicle Championship, INDIA A event for Junior level, Engineers and 3000 KM Solar Challenge for all India
- Formula-G, a yearly track race in Turkey.
- Bharat Solar Challenge, a yearly track race in India.
- Suzuka, a yearly track race in Japan.
- World Green Challenge (World Solarcar Rallye / World Solar Bicycle race), a yearly track race in Japan.
- 2004 Olympics.
- World Solar Rally in Taiwan.
Solar drag races
Solar drag races are another form of solar racing. Unlike long distance solar races, solar dragsters do not use any batteries or pre-charged
Model and educational solar races
Solar vehicle technology can be applied on a small scale, which makes it ideal for educational purposes in the STEM areas.[9] Some events are:
Model Solar Vehicle Challenge Victoria
The Victorian Model Solar Vehicle Challenge is an engineering competition undertaken by students across
Junior Solar Sprint
Junior Solar Sprint was created in the 1980s by the
Speed records
Fédération Internationale de l'Automobile (FIA)
The FIA recognise a land speed record for vehicles powered only by solar panels. The current record was set by the Solar Team Twente, of the University of Twente with their car SolUTra. The record of 37.757 km/h was set in 2005. The record takes place over a flying 1000m run, and is the average speed of 2 runs in opposite directions.
In July, 2014, a group of Australian students from the
Guinness world record
![](http://upload.wikimedia.org/wikipedia/commons/thumb/5/56/Solar_car_LSR.jpg/220px-Solar_car_LSR.jpg)
Miscellaneous records
Australian Transcontinental (Perth to Sydney) Speed Record
The Perth to Sydney Transcontinental record has held a certain allure in Solar Car Racing. Hans Tholstrup (the founder of the World Solar Challenge) first completed this journey in The Quiet Achiever in under 20 days in 1983. This vehicle is in the collection of the National Museum of Australia in Canberra.[13]
The record was beaten by Dick Smith and the Aurora Solar Vehicle Association racing in the Aurora Q1
The current record was set in 2007 by the UNSW Solar Racing Team with their car Sunswift III mk2
Vehicle design
Solar cars combine technology used in the
A usual design for today's successful vehicles is a small canopy in the middle of a curved wing-like array, entirely covered in cells, with 3 wheels. Before, the cockroach style with a smooth nose fairing into the panel was more successful. At lower speeds, with less powerful arrays, other configurations are viable and easier to construct, e.g. covering available surfaces of existing electric vehicles with solar cells or fastening solar canopies above them.
![](http://upload.wikimedia.org/wikipedia/commons/thumb/0/0a/Solar_Vehicles_-_Winnipeg.jpg/220px-Solar_Vehicles_-_Winnipeg.jpg)
Electrical system
The electrical system controls all of the power entering and leaving the system. The
Power electronics may be used to optimize the electrical system. The maximum power tracker adjusts the operating point of the
Some solar cars have complex data acquisition systems that monitor the whole electrical system, while basic cars show battery voltage and motor current. In order to judge the range available with varying solar production and motive consumption, an ampere-hour meter multiplies battery current and rate, thus providing the remaining vehicle range at each moment in the given conditions.
A wide variety of motor types have been used. The most efficient motors exceed 98% efficiency. These are brushless three-"phase" DC, electronically commutated, wheel motors, with a Halbach array configuration for the neodymium-iron-boron magnets, and Litz wire for the windings.[14] Cheaper alternatives are asynchronous AC or brushed DC motors.
![](http://upload.wikimedia.org/wikipedia/commons/thumb/b/b8/Test_chassis.jpg/220px-Test_chassis.jpg)
Mechanical systems
The mechanical systems are designed to keep friction and weight to a minimum while maintaining strength and stiffness. Designers normally use aluminium, titanium and composites to provide a structure that meets strength and stiffness requirements whilst being fairly light. Steel is used for some suspension parts on many cars.
Solar cars 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. Four-wheel vehicles are set up like normal cars or similarly to three-wheeled vehicles with the two rear wheels close together.
Solar cars have a wide range of
Solar cars are required to meet rigorous standards for brakes.
Steering systems for solar cars also vary. The major design factors for steering systems are efficiency, reliability and precision alignment to minimize tire wear and power loss. The popularity of solar car racing has led to some tire manufacturers designing tires for solar vehicles. This has increased overall safety and performance.
All the top teams now use
Testing is essential to demonstrating vehicle reliability prior to a race. It is easy to spend a hundred thousand dollars to gain a two-hour advantage, and equally easy to lose two hours due to reliability issues.
Solar array
The solar array consists of hundreds (or thousands) of photovoltaic
Designing a solar array is more than just stringing a bunch of cells together. A solar array acts like many very small batteries all hooked together in series. The total voltage produced is the sum of all cell voltages. The problem is that if a single cell is in shadow it acts like a diode, blocking the current for the entire string of cells. To design against this, array designers use by-pass diodes in parallel with smaller segments of the string of cells, allowing current around the non-functioning cell(s). Another consideration is that the battery itself can force current backward through the array unless there are blocking diodes put at the end of each panel.
The power produced by the solar array depends on the weather conditions, the position of the sun and the capacity of the array. At noon on a bright day, a good array can produce over 2 kilowatts (2.6 hp). A 6 m2 array of 20% cells will produce roughly 6 kW·h (22 kJ) of energy during a typical day on the WSC.
Some cars have employed free-standing or integrated
, consider wind energy to be solar energy, so their race regulations allow this practice.Aerodynamics
Aerodynamic drag is the main source of losses on a solar race car. The aerodynamic drag of a vehicle is the product of the frontal area and its Cd. For most solar cars the frontal area is 0.75 to 1.3 m2. While Cd as low as 0.10 have been reported, 0.13 is more typical. This needs a great deal of attention to detail.[16]
Mass
The vehicle's mass is also a significant factor. A light vehicle generates less
Rolling resistance
Rolling resistance can be minimized by using the right tires, inflated to the right pressure, correctly aligned, and by minimizing the weight of the vehicle.
Performance equation
The design of a solar car is governed by the following work equation:
which can be usefully simplified to the performance equation
for long-distance races, and values seen in practice.
Briefly, the left-hand side represents the energy input into the car (batteries and power from the sun) and the right-hand side is the energy needed to drive the car along the race route (overcoming rolling resistance, aerodynamic drag, going uphill and accelerating). Everything in this equation can be estimated except v. The parameters include:
![](http://upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Maizebluecatia.gif/300px-Maizebluecatia.gif)
Symbol | Description | Ford Australia | Aurora | Aurora | Aurora |
---|---|---|---|---|---|
Year | 1987 | 1993 | 1999 | 2007 | |
η | Motor, controller and drive train efficiency (decimal) | 0.82 | 0.80 | 0.97 | 0.97 |
ηb | Watt-hour battery efficiency (decimal) | 0.82 | 0.92 | 0.82 | 1.00 (LiPoly) |
E | Energy available in the batteries (joules) | 1.2e7 | 1.8e7 | 1.8e7 | 1.8e7 |
P | Estimated average power from the array (1) (watts) | 918 | 902 | 1050 | 972 |
x | Race route distance (meters) | 3e6 | 3.007e6 | 3.007e6 | 3.007e6 |
W | Weight of the vehicle including payload (newtons) | 2690 | 2950 | 3000 | 2400 |
Crr1 | First coefficient of rolling resistance (non-dimensional) | 0.0060 | 0.0050 | 0.0027 | 0.0027 |
Crr2 | Second coefficient of rolling resistance (newton-seconds per meter) | 0 | 0 | 0 | 0 |
N | Number of wheels on the vehicle (integer) | 4 | 3 | 3 | 3 |
ρ | Air density (kilograms per cubic meter) | 1.22 | 1.22 | 1.22 | 1.22 |
Cd | Coefficient of drag (non-dimensional) | 0.26 | 0.133 | 0.10 | 0.10 |
A | Frontal area (square meters) | 0.70 | 0.75 | 0.75 | 0.76 |
h | Total height that the vehicle will climb (meters) | 0 | 0 | 0 | 0 |
Na | Number of times the vehicle will accelerate in a race day (integer) | 4 | 4 | 4 | 4 |
g | Local acceleration due to gravity variable (meters per second squared) | 9.81 | 9.81 | 9.81 | 9.81 |
v | Calculated average velocity over the route (meters per second) | 16.8 | 20.3 | 27.2 | 27.1 |
Calculated average speed in km/h | 60.5 | 73.1 | 97.9 | 97.6 | |
Actual race speed km/h | 44.8 | 70.1 | 73 | 85 |
Note 1 For the WSC the average panel power can be approximated as (7/9)×nominal power.
Solving the long form of the equation for velocity results in a large equation (approximately 100 terms). Using the power equation as the arbiter, vehicle designers can compare various car designs and evaluate the comparative performance over a given route. Combined with CAE and systems modeling, the power equation can be a useful tool in solar car design.
Race route considerations
The directional orientation of a solar car race route affects the apparent position of the sun in the sky during a race day, which in turn affects the energy input to the vehicle.
- In a south-to-north race route alignment, for example, the sun would rise over the driver's right shoulder and finish over the left (due to the east-west apparent motion of the sun).
- In an east-west race route alignment, the sun would rise behind the vehicle, and appear to move in the direction of the vehicle's movement, setting in the front of the car.
- A hybrid route alignment includes significant sections of south-north and east-west routes together.
This is significant to designers, who seek to maximize energy input to a panel of solar cells (often called an "array" of cells) by designing the array to point directly toward the sun for as long as possible during the race day. Thus, a south-north race car designer might increase the car's total energy input by using solar cells on the sides of the vehicle where the sun will strike them (or by creating a convex array coaxial with the vehicle's movement). In contrast, an east-west race alignment might reduce the benefit from having cells on the side of the vehicle, and thus might encourage design of a flat array.
Because solar cars are often purpose-built, and because arrays do not usually move in relation to the rest of the vehicle (with notable exceptions), this race-route-driven, flat-panel versus convex design compromise is one of the most significant decisions that a solar car designer must make.
For example, the 1990 and 1993 Sunrayce USA events were won by vehicles with significantly convex arrays, corresponding to the south-north race alignments; by 1997, however, most cars in that event had flat arrays to match the change to an east-west route.
Race strategy
Energy consumption
Optimizing energy consumption is of prime importance in a solar car race. Therefore, it is useful to be able to continually monitor and optimize the vehicle's energy parameters. Given the variable conditions, most teams have race speed optimization programs that continuously update the team on how fast the vehicle should be traveling. Some teams employ telemetry that relays vehicle performance data to a following support vehicle, which can provide the vehicle's driver with an optimum strategy.
![](http://upload.wikimedia.org/wikipedia/commons/thumb/3/30/ASC_2003_elevation_plot.png/300px-ASC_2003_elevation_plot.png)
Race route
The race route itself will affect strategy, because the apparent position of the sun in the sky will vary depending on various factors which are specific to the vehicle's orientation (see "Race Route Considerations," above).
In addition, elevation changes over a race route can dramatically change the amount of power needed to travel the route. For example, the 2001 and 2003
Weather forecasting
A successful solar car racing team will need to have access to reliable weather forecasts in order to predict the power input to the vehicle from the sun during each race day.
![](http://upload.wikimedia.org/wikipedia/commons/thumb/d/d9/Christine_2008.png/300px-Christine_2008.png)
See also
- List of solar car teams
- Race the Sun
- South African Solar Challenge
- Tour de Sol
- Hunt-Winston School Solar Car Challenge
- The Quiet Achiever, the world's first solar-powered racecar
- American Solar Challenge
References
- ^ "Toyota Sponsors World's Longest Solar Car Race". Toyota.com. 2008-07-30. Archived from the original on 2011-09-27. Retrieved 2011-08-08.
- ^ "2015 Regulations | World Solar Challenge 2015". www.worldsolarchallenge.org. Archived from the original on 20 July 2014. Retrieved 13 January 2022.
- ^ "Solar Team Eindhoven wins Crunchie in San Francisco". www.tue.nl. Retrieved 22 April 2018.
- ^ "Official NASC2008 Announcement". Tech.groups.yahoo.com. Archived from the original on 2012-07-14. Retrieved 2011-08-08.
- ^ "Official NASC Website". Americansolarchallenge.org. 2010-06-15. Retrieved 2011-08-08.
- ^ https://www.solarcarchallenge.org/challenge/about.shtml
- ^ "Carrera Solar Atacama - Latin America´s first solar car race". www.carrerasolar.com. Retrieved 22 April 2018.
- ^ "Official Solar Drag Race Website". Users.applecapital.net. Archived from the original on 2011-07-23. Retrieved 2011-08-08.
- ^ "Model Solar Victoria". sites.google.com. Retrieved 2019-07-11.
- ^ "Model Solar Victoria". sites.google.com. Retrieved 2019-07-11.
- ^ Holly and Madani. "An Introduction to Building a Model Solar Car" (PDF).
- Phys.Org. January 7, 2011.
- ^ BP Solar Trek vehicle known as the 'Quiet Achiever', National Museum of Australia
- ^ "In-wheel motor for solar-powered electric vehicles: technical details (Publication - Technical)". Csiro.au. 2009-12-01. Retrieved 2011-08-08.
- ^ The Leading Edge, Tamai, Goro, Robert Bently, Inc., 1999, p. 137
- ISBN 0-7334-1527-X
- ^ Solar Vehicle Performance, Dr. Eric Slimko, December 1, 1991
External links
![](http://upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png)
- Howstuffworks.com: How solar cars work
- Solar Decathlon website.
- Solar cars in inventors.about.com
- World Solar Challenge website
- American Solar Challenge
- International Solar Car A - Z
- The Dell-Winston Solar Challenge
- South African Solar Challenge
- Carrera Solar Atacama
- https://web.archive.org/web/20080517201319/http://web.ew.usna.edu/~bruninga/APRS-SPHEV.html
- National Museum of Australia BP Solar Trek vehicle The Quiet Achiever
- Solar Racing News