Updated: Jun 19
Solar-based technologies are finding applications in virtually all aspects of life, providing alternative energy solutions and widening the range of options available to us. We've covered solar air-conditioners, solar car chargers, solar generators, solar water pumps, solar laptop chargers, solar water heaters, solar freezers, solar streetlights, solar window blinds, etc.
Solar energy has been largely underrated, at least, until recently, but it should go without saying, for instance, that without solar panels, there will be satellites and without satellites, there will not be much or any of the Internet and Radio-waves-based communication of the present day. Since the 1950's, the solar industry has created new possibilities. The results of one of such attempts, the solar car, has been varied. Belonging to the category of 'solar vehicles', a solar car is a vehicle powered by direct sunlight. This is achieved with the help of solar cells contained in solar panels installed on the vehicles that convert the sun's energy directly into electric energy.
A Brief History
The idea of a solar car was first presented to the public when on August 31, 1955, William G. Cobb demonstrated his 15-inch-long Sunmobile at the General Motors Powerama auto show held in Chicago, Illinois.
The Sunmobile worked by the help of12 solar cells built into the roof, hood and bonnet of the Sunmobile. The solar panels produced an electric current that turned a tiny electric motor that turned the vehicle’s driveshaft, which was connected to its rear axle by a pulley.
Solar Race Cars
Mr. Cobb's dream of a green car that does not do any damage to the planet and runs forever or at least, as far as the sun shines, became a vintage buggy with a solar panel on its roof before disappearing for a while. By the late 1980s, Mr. Cobb's dream morphed and lived on in the form of a sport mostly among universities' engineering students--solar car racing.
The first solar car race was the Tour de Sol in 1985. It was followed by several similar races in Europe, US and Australia, entered mostly by universities to develop their students' engineering and technological skills. Business corporations have also entered competitions in the past. There are annual solar car racing events in the United States, Australia and even South Africa. Like the professional racing sport, solar car races have routes, support teams, challenges--and record holders.
A Nomenclature Problem
It was not until this year that the first solar cars meant for the public road entered the market. Yet, the term 'solar car' used in the strict sense, as a car that is powered by solar panels and whose battery is charged by the solar panels, is somewhat of a misnomer. For the best definition, solar cars are adaptations of electric vehicles. More or less. The solar panels on the cars provide only a slight charge while the car still largely depends on incorporated lithium-ion batteries for majority of its power, which will still be charged at EV charge points.
This Is Why We Can't Have Nice Things--Like Solar-Powered Cars
Technically, 'solar-powered cars', that is cars that will be fully or at least, mostly powered by solar panels are still a dream because per the small efficiency rating of panels made from even the most sophisticated solar panel technology, only a fraction of the amount of solar panels that will power a mechanical engine can be installed on a typical car. For instance, the average automobile engine is rated at about 15kW. It will require some 40 to 60 of the solar panels available in the market to generate that amount of power. A truly solar-powered car will be dependent mostly on advances in solar panel technologies that will increase the productivity of panels per installation space.
APTERA: Designing for Greater Efficiency
Efficiency is a measure of how well a solar panel performs its duty. Solar panels lose much of their productivity to excess heat, blocking of the sun by busbars, deficiencies arising from the nature of materials used in designing them, etc. Petrol vehicles are just 12% to 30% efficient. Most of the energy is lost in the engine, as much as 72%, primarily as heat with 25% more power lost to the tyres through wind resistance, rolling resistance and braking. Electric vehicles have efficiency rates of between 73% to 90%. About 10% of the energy is lost in converting alternating current from the electrical grid into direct current for the battery. More inefficiencies in the drive system take away another 20%. This is in addition to more losses in wind resistance and friction.
To use what they had in solar panels to make what they wanted, Aptera came up with a design they say can prevent those those wastages and thus, increase efficiency. According to Aptera creators the ultralight bodywork, uber-slick aero, and tires with very low rolling resistance design will reduce aerodynamic drag to the barest minimum and thus make their car 13X more efficient than a gas-powered pickup truck and 4X more efficient than the average electric vehicle. They say that at least 90% of the power produced by the Aptera’s solar panels will go toward moving the car.
The innovative design comes with a staggering claim that the car would be a 'never charge' car, at least 'for most daily use'. To be sure, it will still incorporate a 100kWh battery pack which would provide the bulk of power for the car engine. Under ideal environmental conditions, the solar cells will contribute up to 41 miles per day. Considering that most drivers drive less than 30 miles per day, this contribution from the solar panels without the need for charging will make the cars 'solar-powered' in a definite sence.
Well, the Aptera's three-wheeler has been a success, if not for its solar cells but for its efficiency. Aptera's reputation lies with its high efficiency rather than as a solar-car. It is presently the most efficient vehicle being offered for public use. Nonetheless, taking atmospheric conditions, poor panel positioning, shading by dirt and other things beside aerodynamics into consideration, it is still a tiny two-seater. (Aptera Motors says it will begin designing a full-sized 6-passenger vehicle in the second half of 2020. Aptera seems to have abandoned plans to go in this direction.)
The first vehicle that integrated solar panels was Audi's 80 Coupé supplied with solar panels from solar roofs or vehicle-integrated photovoltaics (VIPVs) Webasto in 1989. Manufacturers are moving away from solar-powered vehicles in the direction of VIPVs. Audi says it will offer customers opportunity to incorporate solar panels into their EVs. Since 2020, Hyundai has been offering its hybrid vehicles with solar panels. In 2019, Toyota teamed up with Sharp and Japanese research institute NEDO to demonstrate a version of Toyota’s popular Prius, integrated with 34%-efficient triple junction III/V cells. In January 2022, Mercedes announced its Vision EQXX. Slated for release in 2024, the Vision EQXX incorporates rooftop solar panels. But like much of solar roofs available in the automobile industry, they will not be integrated into the car’s electric drive train. Instead, they will provide charging to batteries that will power auxiliary functions like the climate-control system, infotainment and other auxiliaries.
Like the Aptera, these VIPVs are designed for greater efficiency even though not with the same high-end attraction as the Aptera. Yet, even with these successes, the fate of 'solar cars' will be decided by the coming of solar panels with high conversion rates. At the present, the solar industry is rising to the challenge.
Regardless, cars wholly or mostly powered by embedded solar cells will remain a dream for the much of the foreseeable future. Even when there are solar panels that can convert 100% of the sunlight that falls on them to electricity, a new challenge would be weather conditions. The rise of VIPVs suggest that the industry is moving in the direction of solar-powered cars and will arrive there eventually. In the mean time, it is fair to be satisfied with EVs integrated with solar panels or VIPVs. For now.