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, and businesses such as Toyota 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 Australian continent. The 30th Anniversary race of the World Solar Challenge was held in October 2017. Major regulation changes were released in June 2006 for this race to increase safety, to build a new generation of solar car, which with little modification could be the basis for a practical proposition for sustainable transport and intended to slow down cars in the main event, which could easily exceed the speed limit (110 km/h) in previous years.
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. The Dutch TU Eindhoven solar racing team were the inaugural Cruiser Class winner with their vehicle "Stella".
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. 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 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 South African Solar Challenge is a biennial, two-week solar-powered car race through the length and breadth of South Africa. The first challenge in 2008 proved that this event can attract the interest of the public, and that it has the necessary international backing from the FIA. Late in September, all entrants will take off from Pretoria and make their way to Cape Town, then drive along the coast to Durban, before climbing the escarpment on their way back to the finish line in Pretoria 11 days later. The event has (in both 2008 and 2010) been endorsed by International Solarcar Federation (ISF), Fédération Internationale de l'Automobile (FIA), World Wildlife Fund (WWF) making it the first Solar Race to receive endorsement from these 3 organizations. The last race took place in 2016. Sasol confirmed their support of the South Africa Solar Challenge, by taking naming rights to the event, so that for the duration of their sponsorship, the event was known as the Sasol Solar Challenge, South Africa.
Carrera Solar Atacama.
The Carrera Solar Atacama is the first solar-powered car race of its kind in Latin America; the race covers 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 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.
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 energy storage devices. Racers go head-to-head over a straight quarter kilometer distance. Currently, a solar drag race is held each year on the Saturday closest to the summer solstice in Wenatchee, Washington, USA. The world record for this event is 29.5 seconds set by the South Whidbey High School team on June 23, 2007.
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. Some events are:
Model Solar Vehicle Challenge Victoria.
The Victorian Model Solar Vehicle Challenge is an engineering competition undertaken by students across Victoria, year 1 to Year 12. Students design and construct their own vehicle, be it a car or boat. This event is currently held at ScienceWorks (Melbourne) in October each year. The first event was held in 1986. The goal of the challenge is to provide students with an experience of what it is like to work in STEM and to understand what can be achieved with renewable technology.
Junior Solar Sprint.
Junior Solar Sprint was created in the 1980s by the National Renewable Energy Laboratory (NREL) to teach younger children about the importance and challenges of using renewable energy. The project also teaches students how the engineering process is applied, and how solar panels, transmission, and aerodynamics can be used in practice.
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 UNSW Sunswift solar racing team at the University of New South Wales broke a world record in their solar car, for the fastest electric car weighing less than and capable of travelling on a single battery charge. This particular record was overseen by the Confederation of Australian Motorsport on behalf of the FIA and is not exclusive to solar-powered cars but to any electric car, and so during the attempt, the solar panels were disconnected from the electrical systems. The previous record of - which had been set in 1988 - was broken by the team with an average speed of over the distance.
Guinness world record.
Guinness World Records recognize a land speed record for vehicles powered only by solar panels. This record is currently held by the University of New South Wales with the car Sunswift IV. Its battery was removed so the vehicle was powered only by its solar panels. The record of was set on 7 January 2011 at the naval air base in Nowra, breaking the record previously held by the General Motors car Sunraycer of . The record takes place over a flying stretch, and is the average of two runs in opposite directions.
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.
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 aerospace, bicycle, alternative energy and automotive industries. Unlike most race cars, solar cars are designed with severe energy constraints imposed by the race regulations. These rules limit the energy used to only that collected from solar radiation, albeit starting with a fully charged battery pack. Some vehicle classes also allow human power input. As a result, optimizing the design to account for aerodynamic drag, vehicle weight, rolling resistance and electrical efficiency are paramount.
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.
Electrical system.
The electrical system controls all of the power entering and leaving the system. The battery pack stores surplus solar energy produced when the vehicle is stationary or travelling slowly or downhill. Solar cars use a range of batteries including lead-acid batteries, nickel-metal hydride batteries (NiMH), nickel-cadmium batteries (NiCd), lithium ion batteries and lithium polymer batteries.
Power electronics may be used to optimize the electrical system. The maximum power tracker adjusts the operating point of the solar array to the voltage that produces the most power for the given conditions, e.g. temperature. The battery manager protects the batteries from overcharging. The motor controller controls the desired motor power. Many controllers allow regenerative braking, i.e. power is fed back into the battery during deceleration.
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