The Bridgestone World Solar Challenge is not your typical tire-melting, gas-torching car race. Instead of a throttle-cranked spin around a blacktop oval, it’s an eco-minded endurance test through the Australian Outback.
Over the course of four days, experimental franken-machines motor 2,000 miles from Darwin to Adelaide, primarily using solar power. Most of the vehicles don’t look like pointy Formula One racers. Designed to run on the rays of the sun, some of the vehicles resemble Mars-ready hovercrafts and others look like solar Pop Tarts with four wheels snapped on.
A few years ago, the automotive curiosities that won the World Solar Challenge were an occasional gee-whiz story that flashed through your Twitter feed. With the launch of street-legal solar-powered vehicles like the Lightyear One and Sonos Motors’ Sion, as well as established players like Toyota and Kia testing panel integrations, a new race to be the biggest solar car company in the world has begun.
Sunray-propelled sedans also have plenty of skeptics and detractors. Carnegie Mellon professor Jeremy Michalek, director of the university’s Vehicle Electrification Group, says solar panels are an expensive way to get miles. Electric warrior Elon Musk pooh-poohs the concept: “The least efficient place to put solar is on the car.”
Rethinking a car’s architecture
Arjo van der Ham was a junior electrical engineering student at Eindhoven University of Technology in the Netherlands when an acquaintance from the school’s speed-skating club, Lex Hoefsloot, asked to meet about joining a team he was assembling to enter a car in the World Solar Challenge. Van der Ham was focused on a master’s degree and wary of the project. But at the first meeting, fellow engineers started drawing diagrams for a proposed vehicle, and by the time the junior got home that night, he was hooked.
From the end of 2012 to the beginning of 2013, 20 students from the Dutch university designed and fabricated a vehicle so flat it almost looked like a space-age ice cream sandwich. At the October race, the Eindhoven team rolled in third, behind Wales and Germany. But in the cruiser class category, judges took into account design and practicality, and later declared Eindhoven the overall winner.
Hoefsloot spied an even bigger prize and founded Lightyear solar company with van der Ham as chief technology officer. Seven years later, the team has molded what the’ve learned into a prototype that looks less like an ice cream sandwich and more like the sleek front of a bullet train. It will likely cost about $165,000 once it hits the market at the end of 2021 (you can reserve one now by plunking down a refundable $4,000). A more affordable “Tesla Model 3”-style version will arrive a couple of years later. To get things rolling, Lightyear has raised $30 million, has 120 pre-orders, and showed off its demo car from CES in Las Vegas to the World Economic Forum in Davos, Switzerland.
So, what does the team behind the Lightyear One car team know about solar-powered motors that Musk doesn’t? “If Elon were to revisit that decision today and had the opportunity to build the architecture of his car from scratch today instead of 2004 [when Tesla’s early models were designed], he would come to a different conclusion,” says van der Ham. “The solar car works for Lightyear because we do the architecture from the ground up.“
Much of Lightyear’s most important innovation happens before it attaches solar panels and installs the batteries. The Lightyear One seats five people yet has a svelte curb weight of 2,500 pounds. A Prius tips the scales at 3,375 lbs. A Tesla Model 3 comes in between 3,500 and 4,100.
“You really, really, really have to look at the fundamentals first,” explains van der Ham about the weight advantage the Lightyear One has over other cars. “That’s where you’re going to make the biggest difference — in the architecture. Not in the details of the technology.”
Spotlighting New Tests and Old Gimmicks
Other companies, big and small, have been fiddling around with solar power for some time. From 2010 to 2015, Toyota offered a solar roof in America as part of an optional luxury package for the Prius that also included leather seats and remote-controlled air conditioning. About 95,000 U.S. customers purchased the optional package during those years. Since December 2019, the company has also sold 4,500 of the new Prius PHV in Japan and Europe, which has solar panels on the roof capable of generating 160 watts — enough to help with auxiliary power but not move the car for significant miles (that option isn’t currently available in the U.S.).
Toyota recently built a Prius prototype with highly efficient, Sharp-made solar battery cells that can generate 860 watts, potentially enough to power the car for 25-plus miles a day. The new version also expands the cell coverage from just the roof to the hood, rear hatch door, and trunk spoiler. While Toyota made a lot of hubbub about the tests, the review period extended through February 2020 with no firm plans for the more eco-friendly model to appear on the market. If the Japanese company moves forward with an electric vehicle or hybrid that has enough solar panels to power the car, its hybrid market share already gives it a huge advantage over any startup. Toyota arguably has the most experience of any car company in terms of marketing solar vehicles, even ones with limited capacity.
Kia/Hyundai sells optional solar roofs (for about $1,000) on its Sonata and Optima hybrid models in Korea. The company has plans to offer the upgrade in overseas markets, but reps won’t divulge specifics. At optimal conditions, the roofs give the vehicles about 800 more miles a year.
Van der Ham points to the Sonata’s solar roof as a token effort compared with the integration on the Lightyear One, which he promises will get 8,300 miles per year out of its solar cells, even in a foggy town like San Francisco. A good part of Lightyear’s advantage goes back to the weight of the body, which is constructed out of carbon-fiber composite and aluminum versus a more traditional car like the Sonata, which is steel (high-strength, relatively lightweight steel, but still).
Sono Motors
Germany’s Sono Motors is employing a lightweight aluminum frame to keep down the weight of its solar-powered Sion. If Lightyear is the sporty ride for eco-minded alphas, Sion is the affordable alternative for sensible, sun-worshipping betas. The boxy black hatchback has a sloping front and hatchback reminiscent of a Honda Fit and only comes in one color, black. That choice, like many of the features on the car, was decided by the community funding the project.
More than 10,000 people have pre-ordered the Sion by shelling out a refundable $550 toward the purchase price of $28,000. Delivery is slated for early 2022. That’s a lot of faith in founders who started the project when they were students and haven’t even built a formal prototype yet. The vehicle they’ve been touring around does little to mask where the solar panels are and even has a BMW steering column (to be replaced later with a proprietary one). Other decisions, like whether the production car will be front- or rear-wheel drive, have yet to be finalized. That open approach to development helped Sono recently crowdfunded $55 million to help build prototypes and get the car to market.
Sono promises that the solar power will propel the Sion for 10 miles a day, which may not seem like much, but that’s about what a typical German commuter drives in a day, says a company rep. The battery storage will be chargeable up to a 200- to 250-mile range. Other practical features include the ability to drop down the front and back seats to create 8 feet of cabin storage, as well as a section on the front bumper charging port where users can plug in household appliances (in case you need to blend a smoothie while you’re camping).
Building a solar car isn’t easy — or cheap
If it seems like the solar car world is missing American ingenuity, that isn’t completely true. Ford introduced the C-MAX Solar Energi Concept car at CES in 2014, but not much news has been heard since. The University of Michigan has one of the best solar car race teams in the world, having won several national competitions and placed third at the 2019 Bridgestone World Solar Challenge.
Professor Neil Dasgupta, faculty adviser for the Michigan race team, runs a research lab focused on solar power and batteries and says solar car companies will likely wrestle with several trade-offs.
For starters, building a solar car isn’t cheap. Of course, there are photovoltaic cells and batteries. Then there’s the carbon-fiber composite body that Lightyear and the University of Michigan are employing to bring down their cars’ weight. Every pound of carbon fiber composite costs quite a lot, explains Dasgupta. The good news is that the relatively lightweight material can be impressively safe.
“Race car drivers walk out of crashes going 100 miles an hour,” notes the professor. “Those cars are partially made out of carbon fiber composite. They can actually end up being safer than steel-based cars.” Many car manufacturers see the potential in making bodies of the material, but more research and development needs to be done to bring the cost down. A startup building solar cars with solar cells, extremely efficient batteries, and carbon-fiber composite bodies still has to be profitable.
“Whether or not they can get the manufacturing costs down to where it makes sense will dictate the success or failure of a startup company,” figures Dasgupta. Given current technology, he also doesn’t expect many sun-powered pickup trucks or SUVs anytime soon, since the extra space for panels usually isn’t enough to power a heavier vehicle for long distances. The solar roof offered on the new Fisker SUV, for example, only adds 1,000 miles per year to the car.
Sion is trying to keep costs down by utilizing some car parts already on the market. The company is also trying to limit excess energy usage during production by rethinking the automobile assembly line. For example, the body panels will be infused with color rather than painted to save energy and production costs.
Lessons learned
Van der Ham says one of the lessons he’s learned from watching Tesla grow is the importance of not trying to do too much in-house.
“We’re a partnership company,” he explains. “The entire idea behind Lightyear is to use existing stuff and infrastructure as much as possible.” The car’s solar panels are manufactured by California’s Sunpower, for example.
“We do some tricks to make the panels really efficient,” he says, including a design that ensures panels that are in shadow or covered by bird poop don’t slow down the overall charging speed.
The optimization of the panels, the battery, and body makes the Lightyear One twice as efficient as the Tesla Model S. In fact, the team analyzed the impact of putting their solar panels onto Elon Musk’s Model 3 and reckoned it would only add 3,000 miles a year versus 8,000 for the Lightyear One.
“In that sense, I agree with Elon’s comment,” says Van der Ham. “Putting a solar panel right now on the Model 3 doesn’t add that much.”
If you can’t wait a couple of years for a new solar car, check out a project by YouTubers Bryce & Courtney, who quit their jobs and converted a 1988 Dodge Ram Van into a camper with solar panels on the roof that they toured around the U.S. Don’t have $165,000 to spend on a new solar ride? Just bolt a couple of panels on the top of your current car for about $1,000.
