The sun-powered car first caught the public’s attention back in the late 1980s. General Motors brought its solar-powered Sunraycer to the first World Solar Challenge in 1987 and went all out when it came to marketing its invention.
Still taking place, the World Solar Challenge has been the pinnacle of solar car experimentation since that original event took place 35 years ago. The biennial race crosses a 3,000 kilometres route running south through the centre of Australia.
But since the debut of the Sunraycer, very little about road-worthy vehicles powered by the sun rather than a wall outlet has been heard. While universities and research companies have spent several decades working on the vehicles, only a few can accommodate a passenger along with their driver. These cars are still completely custom, tiny, flyweights that can flip over in a strong wind.
Overcoming these challenges are key to making a solar car a reality, and, to understand why that is, requires a look at the efficiency of gasoline, battery-electric vehicles and the state of solar power cells.
According to Natural Resources Canada, a litre of gasoline contains the equivalent of 8.9 kilowatt hours of electricity. Accounting for the less than 40 per cent efficiency of gas engines, that leaves around 3.5 kilowatt hours of energy available to move your car.
The most efficient electric vehicles on sale today need about 16 kilowatt hours of electricity to move 100 kilometres, based on Natural Resources Canada figures. That is the equivalent of around 4.6 litres of gasoline. But, what about solar vehicles?
Mitchell Oastler, Yanshen Zhou and Jens Dekker are members of the University of Waterloo’s solar car team, Midnight Sun. The student-run team of around 75 competes at events like the American Solar Challenge. Started in 1988, it’s one of the oldest solar car teams in the world.
"We build solar cars from the ground up," said Zhou. “(With) our solar array input, we can get around 1,150 watts – 1.5 kilowatt hours. Thanks to no power steering, limited climate control and no charger for its small battery pack, the car can drive around 400 kilometres in eight hours."
The vehicles built for these challenges are also limited in the type and size of solar cell arrays they can use because of their costs. The price for just four-square metres of array is $45,000, said Oastler.
Automakers, including Hyundai, have already toyed with the idea of adding solar panels to hybrid and electric cars. The Sonata hybrid’s solar cell roof has a capacity of just 0.2 kilowatt hours, meaning a full day of sun might add three to four kilometres to the car’s range.
Current solar panels have an efficiency of around 20 per cent, but even at 100 per cent, they would only capture no more than one kilowatt hour of energy per square meter, which is the estimated power of the sun at sea level.
“I don't think it’s really that feasible to have an entirely solar-powered car for the consumer,” Waterloo’s Oastler said. “In terms of an SUV, or to carry your family to soccer practice, I don't think that’s really what we’re looking at.” He said a solar-powered car might be possible as a compact commuter runabout when panels become cheaper.
Still, a few startups think they’ve cracked the code to producing solar vehicles. Companies such as Aptera Motors, Lightyear and Sono Motors are all looking to make an impact. Each advertise the long range capabilities for their veihcles – 1,600 killometres for Aptera, 1,000 for Lightyear and 305 for Sono – but it isn't the sun giving them that range.
The Aptera looks very much like a competition solar vehicle, with seating for two and riding on three wheels. Not yet in production, it will have just 0.7 kilowatt hours of solar cells, enough for a claimed 60 kilometres per day of range. It is a battery of up to 100 kilowatt hours that provides its total driving range. The others two companies are similar.
The Sono Motors Sion, made by a German startup, claims an average of 112 kilometres of range is generated per week through its solar panel. The idea isn’t solar driving, but “self-sufficiency on short distances,” the company said. An additional 54-kilowatt-hour battery gives the vehicle its 305 kilometres of total range. Sono’s also plans is to use panels to power HVAC and refrigeration systems on commercial vehicles.
Lightyear calls its model the world's first solar car. It can add up to 70 kilometres of range in a day with its panels. The 60-kilowatt-hour battery pack handles the rest. The car is available to order now in Europe, from $341,000 (U.S.).
While a smaller battery is necessary for solar cars to handle clouds, trees and other shady situation, larger battery packs mean these vehicles are more akin to slowly self-charging EVs. While the current technology allows for driving short distances a few times a week using solar power, consumers might want to wait for scientists and solar research groups, like the University of Waterloo team, to improve the arrays and their abilities before purchasing.
Until then, large-scale solar arrays that feed into the electricity grid to power your home charger are the closest you'll get to a solar car.