I recently came across a September 18 article by the “future technology” editor at The Wall Street Journal, “Solar-Powered Cars and Trucks Are Almost Here” (sorry, behind paywall, but your local library may have free access). The author was positively gushing about companies such as Aptera Motors (California), which will “soon” be selling all-solar-powered cars. On a full daylight charge, they can do a few tens of miles, then it’s time to park in the Sun for that totally guilt-free “fill up.”

Figure 1 The Aptera solar-powered three-wheel “car” can go between 15 and 40 miles on a full all-solar charge. Source: Aptera Motors

The article focused on the benefits and innovations, such as how Aptera claims to have developed solar panels that withstand road hazards, including rocks kicked up at high speed, and similar advances.

The solar exposure-versus-distance numbers are very modest, to be polite. While people living in a sunny environment could add up to 40 miles (64 km) of range a day in summer months, from panels alone, that drops to around 15 miles (24 km) a day in northern climates in winter. Aptera says its front-wheel-drive version goes from 0 to 60 mph (96 km/hour) in 6 seconds, and has a top speed of 101 mph (163 km/hr).

The article also mentions that Aptera is planning to sell its ruggedized panels to Telo Trucks, a San Carlos (Calif) maker of a 500-horsepower mini-electric truck estimated to ship next year, which uses solar panels to extend its range by 15 to 30 supplemental miles per day.

Then I closed my eyes and thought, “Wait, haven’t I heard this story before?” Sure enough, I looked through my notes and saw that I had commented on Aptera’s efforts and those of others back in a 2021 blog, “Are solar-powered cars the ultimate electric vehicles?” Perhaps it’s no surprise, but the timeline then was also “coming soon.”

The laws of physics conspire to make this a very tough project. This sort of ambitious project requires advances across multiple disciplines. There are the materials for the vehicle itself, batteries, rugged solar panels, battery-management electronics — it’s a long list. These are closely tied to key ratios beginning with power and energy to weight.

Did I mention it’s a three-wheel vehicle (with all the stability issues that brings), seats two people, and is technically classified as a motorcycle despite its fully enclosed cabin? Or that it has to meet vehicle safety mandates and regulations? Will drivers likely need power-draining air conditioning unless they drive open-air, especially as the vehicle needs to be parked in the sun by definition?

I don’t intend to disparage the technological work, innovation, and hard work (and money) they have put into the project. Nonetheless, no matter how you look at it, it’s a lot of effort and retail price (estimated to be around $40,000) for a modest 15 to 40 miles of range. That’s a lot of dollar pain for very modest environmental gain, if any.

Is the all-electric vehicle analogous to the flying car? Given today’s technology and that of the foreseeable future, I think the path of a truly viable all-solar car (at any price) is similar to that other recurrent dream: the flying car. Many social observers say that the hybrid vehicle (different meaning of “hybrid” here, of course) was brought into popular culture in 1962 by the TV show The Jetsons – but there had been articles in magazines such as Popular Science even before that date.

Figure 2 The flying car that is often discussed was likely inspired by the 1962 animated series “The Jetsons.” Source: Thejetsons.fandom.com

Roughly every ten years since then, the dream resurfaces and there’s a wave of articles in the general media about all the new flying cars under development and road/air test, and how actual showroom models are “just around the corner.” However, it seems like we are always approaching but not making the turn around that corner; Terrafugia’s massive publicity wave, followed by subsequent bankruptcy, is just one example.

The problem for flying cars, however attractive the concept may be, is that the priority needs and constraints for a ground vehicle, such as a car, are not aligned with those of an aircraft; in fact, they often contradict each other.

It’s difficult enough in any vehicle-engineering design to find a suitable balance among tradeoffs and constraints – after all, that’s what engineering is about. For the flying car, however, it is not so much about finding the balance point as it is about reconciling dramatically opposing issues. In addition, both classes of vehicles are subject to many regulatory mandates related to safety, and those add significant complexity.

Sometimes, it’s nearly impossible to “square the circle” and come up with a viable and acceptable solution to opposing requirements. Literally, “to square the circle” refers to the geometry challenge of constructing a square with the same area as a given circle but using only a compass and straightedge, a problem posed by the ancient Greeks and which was proven impossible in 1882. Metaphorically, the phrase means to attempt or solve something that seems impossible, such as combining two fundamentally different or incompatible things.

What’s the future for these all-solar “cars”? Unlike talking heads, pundits, and journalists, I’ll admit that I have no idea. They may never happen, they may become an expensive “toy” for some, or they may capture a small but measurable market share. Once prototypes are out on the street getting some serious road mileage, further innovations and updates may make them more attractive and perhaps less costly—again, I don’t know (nor does anyone).

Given the uncertainties associated with solar-powered and flying cars, why do they get so much attention? That’s an easy question to answer: they are fun and fairly easy to write about and the coverage gets attention. After all, they are more exciting to present and likely to attract more attention than silicon-carbide MOSFETs.

What’s your sense of the reality of solar-powered cars? Are they a dream with too many real-world limitations? Will they be a meaningful contribution to environmental issues, or an expensive virtue-signaling project—assuming they make it out of the garage and become highway-rated, street-legal vehicles?

Bill Schweber is an EE who has written three textbooks, hundreds of technical articles, opinion columns, and product features.

Related Content

• Are solar-powered cars the ultimate electric vehicles?
• Keep solar panels clean from dust, fungus
• Home solar-supply topologies illustrate tradeoff realities
• Solar-Driven TEG Advances via Fabrication, Not Materials

References

• Smithsonian Magazine, “Recapping ‘The Jetsons’: Episode 03 – The Space Car”
• Popular Science, “The Flying Car Gets Real”(2008)
• Aircraft Owners and Pilots Association, “AOPA Terrafugia pulls US plug on Transition flying car” (2021)

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