September 15th, 2020 by Jennifer Sensiba
With home/rooftop solar, a growing number of EV drivers are doing most of their driving on home-generated solar power. Solar panels mounted on vehicles themselves, on the other hand, have been the subject of well-deserved skepticism. But is this skepticism still well deserved in 2020?
While directly powering a vehicle’s electric motor with on-vehicle panels is still pretty far out of the question (outside of very impractical experimental cars), using relatively low-power solar cells to charge a battery shows a lot more promise. Universities and companies with fairly deep pockets have been experimenting with battery-solar vehicles for decades, with some fairly good progress recently.
For example, Toyota has a Prius Prime prototype that adds 27 miles of driving range per day in good conditions, while Sono Motors estimates its cars can add 19 miles of range per day with typical German solar conditions. 15-30 miles of range isn’t enough for onboard solar to be a car’s only power source, but it can cover most of the average driver’s needs while leaving the rest to grid charging or home solar.
On the other hand, on-vehicle solar panels have to make financial sense to car buyers. Sure, a vehicle with the best commercially available panels (ex. Sono Motors), or even expensive experimental panels (ex. Toyota’s prototype) can do amazing things, but if the panels cost too much, they negate most of the advantage one can gain from charging with them. The price can’t exceed the benefits if we are to expect mass adoption.
One way we can gauge a technology’s cost is how accessible it is for the DIY crowd. If people without deep corporate or governmental pockets can successfully use a technology, it’s probably something an automaker can offer even cheaper. DIY experimenters don’t have the advantage of mass production, bulk purchasing from suppliers, and an array of experts to help implement the solution. With those advantages, the cost per mile of added daily range can be lower.
Last year, I wrote about Sam Elliot’s solar Nissan LEAF. With its degraded battery pack, his recently-purchased used LEAF could get him to work, but couldn’t quite get him home. His workplace doesn’t offer EV charging, so he had to find another way to add a few more miles, leading to his solar charging project. His recent video update tells us about his expanded slide-out solar panels, improved…
In the above video, we learn about how Sam’s setup has improved over time. He’s been adding additional panels, including some that slide out for more surface area while parked. While more cells on more panels helps raise the number of miles added, Sam still struggles with the inability to directly charge the LEAF’s pack, instead relying on a somewhat complicated system of extra batteries, an inverter, a timer, and an EVSE. It works, but it’s probably a lot more trouble than most people would want in a solar car.
He interviews James, whose electronics skills helped him put that solar power directly into a Chevy Volt’s battery pack. It required a custom circuit board and several connections under the hood, but it didn’t require opening up the battery pack, so it’s probably the best approach so far to add solar to cars that weren’t built that way. On his site, he gives detailed stats for the last several days of driving. While gaining around 1 kWh per day (around 4 miles for a Volt) is far from impressive compared to home solar and automaker efforts, it’s only using two solar panels to do this. Custom panels covering most of the vehicle would give results a lot closer to what we’re seeing with Sono or Toyota above.
Between what both the automakers and these two DIY tinkerers have done, we are starting to see how this all could end up working in the mass market. Obviously, surface area is going to be important for any solar-battery car. More area means more range added, so most of the car’s surface is going to need to be covered for flush-mounted installs. While parked, though, vehicles could do what Sam’s LEAF and the Solarrolla/Route del Sol van do: fold out more and more panels to get closer to the kind of power you can get from a home rooftop setup. Even Elon Musk seems warm to the idea:
Will be an option to add solar power that generates 15 miles per day, possibly more. Would love this to be self-powered. Adding fold out solar wings would generate 30 to 40 miles per day. Avg miles per day in US is 30.
— Elon Musk (@elonmusk) November 22, 2019
While still probably not up to what most drivers would want in a solar vehicle, the technology is advancing rapidly and isn’t going to be worthy of skepticism forever.
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