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This Is Why Solar Cars Are Still Far From Reality

For people who love cars and the technical elements surrounding them, the Engineering Explained YouTube channel is a stronghold. Jason Fenske’s latest video tried to teach why we can’t talk about solar-powered electric cars just yet by checking all the numbers involved with solar charging. By the end of the video, he also verified the claims of one of the few companies that claim it will sell a solar car: Aptera.
Lightyear One 1 photo
To start at the very beginning, Fenske shows how much energy the sun provides to Earth. At any given moment, we are getting 1.36 kW/m². The engineer multiplied that for Earth’s surface area and concluded that the planet receives 173 trillion kW. When you consider mankind spends 190 trillion kW per year, it would take only one hour of sunlight to supply that.

The issue is that things are not so simple. First of all, because not all of that energy actually hits our surface: 22% is reflected, and 23% is absorbed by the atmosphere. We still have 55% of that solar power to use, but then the hindrance comes to our technology.

Single-junction solar panels – the most common ones – have an average conversion efficiency of 33.7%. The Earth also is not flat, which makes the sun rays hitting any place vary as the day goes by. Putting all those factors together, you get only 250 W of the original 1.36 kW in the best-case scenario. In the worst one when you still have sunlight, the amount of energy drops to 62.5 W.

Suppose a Tesla Model 3 had solar panels all over its top surface, and it got the best solar exposure. In that hypothetical situation, Fenske calculated it would get only 1.5 kW in 24 hours. With its 75 kWh battery pack, it would need 50 hours to fully charge.

If the solar Model 3 had to work with the worst number, it would get only 375 W in 24 hours – or 0.375 kW, if you prefer. Charging would then demand 200 hours or 8.3 days. That sums up why no conventional cars are cropping solar energy with their own bodies.

For that to work, the vehicle would need a large surface, and it would need to be highly energy-efficient. That’s what Aptera pledges its electric trike will be. It also promises that the Never Charge system – a standard solar charging strategy – can give up to 43 miles of range per day solely on solar power.

Fenske checked if Aptera’s numbers were correct, and there’s nothing wrong with them. Now that the endorsement for the theory is there, the engineer wants to see what the company can deliver for real, and he is not alone. Make sure to watch the entire video below.

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