– Why do electric cars not have solar panels on rooftop so they could be charged while driving/parked

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– Why do electric cars not have solar panels on rooftop so they could be charged while driving/parked

In: Engineering

27 Answers

Anonymous 0 Comments

In addition to all of the answers about problems with efficiency and such, another reason this isn’t typically done is that it’s ugly. People often care about the appearance of their vehicles, and solar panels on the roof tend to be more of an eyesore and will turn many people away, especially considering how minimal the benefit is.

Anonymous 0 Comments

Solar panels really don’t put out a lot of electricity.

Let’s take the Tesla Model 3 for example. Solar panels the size of its roof+hood only put out about 150 watts.

The Model 3’s smallest available battery option is 54 kilowatt-hours.

The mathematics of that mean that it would take 360 hours of perfect sunlight to charge the battery from empty to full. Or from another perspective, if you had 10 hours of perfect sunlight, it wouldn’t quite give you even 3% charge.

Anonymous 0 Comments

The quick answer – it isn’t an efficient use of power.

Solar panels are fairly inefficient, so the size of panel that can be installed on the roof of an electric car won’t generate enough power to add an appreciable mileage to the battery, while adding extra weight to the vehicle (which will shorten its range).

Lighter weight panels are being used in a few vehicles to power the lighter duty systems though – while they can’t generate enough power to run the motors they can help power things like the low voltage systems powering the AC or entertainment systems, allowing more use of those without impacting overall mileage.

Anonymous 0 Comments

tl;dr: Rule of thumb: You need about 6.5 m² per kW of solar power give or take. A car has not even 10 m². The extra infrastructure in the car adds to the weight and ruins the little extra mileage.

Maximum solar power at high noon at the equator, above the atmosphere is 1367 W/m².

Assume a car is a 2*5m flat surface, we’d end up with 10m² of possible solar panel area, ignoring the windshield.

Ignoring the filtration and damping by the atmosphere, we’d get a maximum power of 13.67 kW per car, which equals about 18.5 horsepowers. This isn’t sufficient to keep a car driving, but definetely a respectable amount of power to charge the batteries and maybe double it’s range while driving.

Anyway, we were still dreaming of a world where’s always high noon everywhere (90° angle of sunlight), clear blue sky, a world without an atmosphere where all the juicy 1367 Watts per m² reach the surface instead of the maybe 800-900 Watts in reality. Also we entirely ignored the fact that solar panels aren’t 100% efficient, which in reality is 20% at best, and that those solar panels ned to be perfectly clean because their efficiency is squarely dependent on the area.

If at all, we’d get a maximum of about 1.5 kW out of a solar car which isn’t even enough to power a lawn mower, and even if we did it, the extra complexity (charge pump, capacitors, cabling, glass cover etc.) would eat it all up by its weight and the mileage is ruined.

Anonymous 0 Comments

Solar works best when it’s correctly angled to the sun according to your latitude. Right off the bat, you’re losing significant generation capacity just by having it at a random angle to the sun by virtue of it following the body of your car. Next, even if it was perfectly oriented, the square footage that your average vehicle offers means that you wouldn’t be able to have enough solar to generate enough electricity to do much more than run the AC for a while, something that you’re probably going to want to do after leaving your car in the sun all day. Next, what happens if you park in a garage? Or under a tree for shade?

Most people are going to be far better off covering your house roof with solar and just plugging your car into it when you are home.

That’s not to say that there’s no point to solar on a vehicle. If the car is efficient enough, like the upcoming Aptera electric car (which takes efficiency to such an extreme that it can go 1000 miles on the same battery that a Tesla can only go 300 miles on). In this case, solar does make sense because due to that efficiency it can gain ~30 miles, or the average American commute, each day it sits in the sun. So, under the right conditions, that car could legitimately never need to be plugged in.

Another reason solar on a vehicle could make sense is if you’re leaving it for many days at a time not plugged in. All electric cars have some degree of phantom power drain as the car uses a tiny bit of power even when parked. That drain is usually less than a percent of your battery per day but over time it can add up. If you park at an airport or head out to the bush to camp for a month or more your car could be down 10 to 20 percent by the time you come back. (Winter is a different story). So solar in this case could probably cover that phantom drain.

Anonymous 0 Comments

There are, a few brands that sell cars with an option for a solar roof. In some markets, Hyundai’s new Ioniq 5 has a solar roof option, for example.

In practice, there’s limited area and solar panels are only so efficient. Solar roofs add cost and complexity, but don’t generate much power (compared to the energy demand for the car). Hyundai says that parked outside on a sunny day, the solar roof for the Ioniq 5 can produce enough power to add up to 6 km of range to the car (a bit less than 1 kWh).

Because it costs more, and it provides marginal benefit (even on a nice clear sunny day), it’s assumed that most people probably wouldn’t buy it. This is probably correct; the glass roof seems like a more popular option.

Anonymous 0 Comments

There’s not a lot of surface area on a car compared to the amount of energy it uses. It might be worthwhile if your daily commute is only a couple miles, but to go farther you’d still need to plug it in.

On the other hand, you can put a lot more solar panels on the roof of your house or workplace.

Anonymous 0 Comments

They do make some with solar panels on it but, as far as I am aware, the functionality of those panels is for smaller tasks like cooling the car down before the driver gets back in..

Anonymous 0 Comments

I dunno, probably not able to take in enough power to move the car very far. We could probably use solar panels to power other things like LED lights, fans, etc. though.

What would be cool, in my opinion, is if someday we were able to get wireless charging type tech in or under the roads, and have cars charge their batteries while driving on such roads.

Anonymous 0 Comments

More expensive, as well as likely to get damaged and become even more expensive. All that for probably not even enough power to be noticeable.