In 1955, a tiny, toy-like creation called the “Sun mobile” was built using balsa wood and hobby shop tires. Its exterior was embellished with 12 selenium solar cells that produced less power than a horse. It was a proof of concept, though: even with just sunlight, a car can run. Over time, the dream evolved into a vintage buggy with solar panels on the roof. Then we saw a glorified bicycle, a retiree’s garage project, and a racecar that covered 51 miles per hour in the Mojave Desert. It is the dream of perpetual motion. It is a dream of travel that doesn’t harm the planet.
Of journeys that last as long as the sun. This dream has big problems. There are clouds. The night falls. A solar panel’s ability to convert light into energy is limited by the laws of physics. However, one start-up claims to have overcome those challenges. You can now own the dream for as little as $25,900, say the company’s founders. Aptera Motors, a California company whose name is derived from the ancient Greek word for “wingless,” is launching the first mass-produced solar car this year.
The vehicle is an ultra-aerodynamic, three-wheeled electric vehicle with 34 square feet of solar cells on top. These cells are so efficient that, on a clear day, they could provide enough energy to drive about 40 miles – about twice the distance an average American commutes. Aptera must undergo safety tests before it can begin distribution, which it hopes to do by the end of this year. Even then, it is not clear that consumers will want something that looks like a cross between a Batmobile and a Beetle.
As the founders prepare to launch their new product, the shadow of their first attempt, which ended in bankruptcy, hangs over them. Chris Anthony and Steve Fambro, Aptera’s creators, believe the world needs a car like theirs. The transportation sector is the largest source of planet-warming pollution in the U.S. Biden administration officials have made reducing vehicle emissions a priority, and several major automakers have committed to phasing out internal combustion engines. Having dreamed of driving in the sunshine for years, perhaps the time has finally come.
Solar panel power
It wasn’t Anthony and Fambro’s intention to build a vehicle that could run on solar power. Their goal was to build a car that was more fuel-efficient. According to Energy Department data, burning gasoline is not the most efficient way to travel; up to four-fifths of the energy produced by an internal combustion engine is lost in the form of heat, lost overcoming wind resistance, or consumed by fuel pumps and other components. The performance of all-electric vehicles is much better, but they’re not perfect.
Approximately 10 percent of the energy that goes into them is lost during the conversion of alternating current from the grid into direct current. Inefficiency in the drive system eats up another 20 percent of the car’s energy, and the car must still deal with wind resistance and friction, though regenerative braking systems can reduce some waste. The Aptera is designed to eliminate as much waste as possible. The car’s creators claim it is 13 times more efficient than a gas-powered pickup truck and four times more efficient than the average electric vehicle. The Aptera’s solar panels produce 90 percent of the power it needs to move, according to the company.
How to design for efficiency
Designed like a small, speedy aircraft, the vehicle’s body is curved at the nose, wide along the sides, and tapered toward the trunk. Reduces drag, or the force of air flowing against the motion of the vehicle.
Like the belly of a dolphin, the Aptera’s undercarriage swoops. The turbulent air between the vehicle and the ground reduces drag.
In addition, the engineers tested at least ten types of tires to find the one that has the least “rolling resistance” – the friction that comes from the wheels against the ground. They also designed the car with three tires instead of four to eliminate a point where energy can be lost.
The Aptera uses ultra-light carbon composites and fiberglass in order to reduce its energy consumption. The arched shape, which mimics the physics of an eggshell, makes it as strong as steel. Many of its parts can be printed on a 3D printer, reducing costs.
As the car is parked, heat is automatically removed, reducing the load on the air conditioner. Electronics use wires that offer the least resistance, ultra-efficient LEDs, and low-power displays, and sleep modes for the main screen when not in use.
In the end, this results in a very fuel-efficient vehicle. Aptera consumes just 100 watt hours of energy per mile, about as much as a desktop computer does in 30 minutes.
The Aptera can be recharged by plugging it into an outlet, just like a standard electric vehicle. At an ordinary charging station, the car can reach 150 miles in just 15 minutes due to its extreme efficiency. For an electric car to go farther than a few miles, however, a solar panel “the size of a semi-truck” would be required, Fambro says. Aptera can propel itself using only a few solar cells. It only works if you have a super-efficient vehicle, Fambro explained. Once he and Anthony realized just how far the sun alone could take them, “there was no alternative but to make it a solar vehicle.”
Impractical but inspirational
Sun mobile, the world’s first solar vehicle, made its debut at a General Motors trade show 65 years ago. Even its inventors were skeptical of its prospects. The magazine Popular Mechanics reported that GM officials believed their creation had no practical application for the automotive industry. Hans Tholstrup, a Danish explorer, found exactly what he was looking for in that challenge. Having felt guilty for his fossil-fuel guzzling exploits – flying around the world, driving a speedboat across Australia – he wanted to do something to benefit the planet.
In 1982, Tholstrup and racecar driver Larry Perkins debuted the “Quiet Achiever” – a boat-shaped, single-driver vehicle topped with a 90-square-foot solar array. The tiller was used as the steering system, and a bicycle’s wheels and brakes were used as the wheels and brakes. As they drove 2,560 miles across Australia, they ate orange slices to stay hydrated and camped along the roadside. At an average speed of 15 miles per hour, they drove 2,560 miles in 20 days.
Tom Snooks, the project’s coordinator, recalled Tholstrup’s comparison of the journey to the flight of the Kittyhawk: impractical but inspiring, and a sign of what’s to come. “If we can inspire just one other idea or think in the development of solar power,” Tholstrup said, “then the venture will have been worthwhile.” To inspire others to surpass his record, Tholstrup launched the “World Solar Challenge” in 1987. Solar races were soon being held across the globe, attracting both car manufacturers and high school students.
Tholstrup’s “bathtub on wheels” gave way to bullet shapes and three-wheeled cars with curved, winglike solar arrays. In 2013, the World Solar Challenge introduced a “cruiser class” competition to spur the development of more commercially viable vehicles. University of Michigan mechanical engineer Neil Dasgupta is the faculty adviser to the school’s highly decorated solar car team. And we’ve made tremendous progress.” The team’s 2017 vehicle, which placed second in the World Solar Challenge, weighed just 420 pounds and averaged almost 50 mph.
As a result of inefficiencies in solar panels, solar cars must be compact and sleek, said Dasgupta. The wavelengths that photovoltaic cells can convert into electricity are limited. Heat makes them less efficient. The best solar panels convert only about 23 percent of the sunlight they receive into energy. Simply plugging into a charging station will give you much more power more quickly. Total reliance on solar power also presents practical challenges. In other words, the car can’t be parked in a garage or under a tree. When the battery is full, any additional energy that hits the solar panels is lost.