Adding flexible solar panels to an electric car

A friend who converted an ICE car to electric told me that adding (after market) solar to the roof of an electric car (like a prius, leaf or tesla) is not a good idea...

As I am very much new to this, I thought I'd ask here - as from the posts I've read, a lot of people posting here really know a lot!

So, is there any issue with adding after market flexible solar (like on the sono sion?) to an EV? other than the cost, and what it will look like?

Just so you know, I live in Honolulu, in a condo (so no roof access). I park in the sun. I don't drive much, but absolutely need a car. If I can get 5 to 15 miles of range / day from solar panels on the car roof, that would be great! I realize I'll have to plug in sometimes, I just don't want to be tied to the charging stations like some of my condo dwelling friends.

Thank you!

Main reasons why is a silly idea:
A 380w roof solar panel costs 150-200 bucks and "pays itself" in 3 years of electricity. Is mounted with perfect angle and direction to get as much sun as possible without obstructions.

A flexible 100w panel costs 400 bucks and a car will rarely be on the sun, buildings /trees etc block sun light and flexi panels would degrade in 2 or 3 years on a car, never getting a return on investment.

A big van can fit about 1kw of panels on their roof, which generate about 2-3 kwh average a day(due to their less than optimal roof angle) depending on where you live if you park on the sun everyday. That energy is not even enough to drive 10 miles.

Hope it clears why it's a silly idea to put solar on evs

To get 15 miles range a day, you would need 2kw of solar panels. That's like an area of 12ft x 12ft residential panels

If you really want to charge ev with solar, is cheaper/more efficient to spend 5000 on solar at home and charge at home than spending 20000 putting solar on the car itself.

x4dow said:

Main reasons why is a silly idea:
A 380w roof solar panel costs 150-200 bucks and "pays itself" in 3 years of electricity. Is mounted with perfect angle and direction to get as much sun as possible without obstructions.

A flexible 100w panel costs 400 bucks and a car will rarely be on the sun, buildings /trees etc block sun light and flexi panels would degrade in 2 or 3 years on a car, never getting a return on investment.

A big van can fit about 1kw of panels on their roof, which generate about 2-3 kwh average a day(due to their less than optimal roof angle) depending on where you live if you park on the sun everyday. That energy is not even enough to drive 10 miles.

Hope it clears why it's a silly idea to put solar on evs

To get 15 miles range a day, you would need 2kw of solar panels. That's like an area of 12ft x 12ft residential panels

Click to expand...

Thanks. Again, my options are limited.

Solar electric vehicle said:

Thanks. Again, my options are limited.

Click to expand...

... so how is sono sion claiming their pv on car will generate 15 to 20 miles / day?

x4dow said:

If you really want to charge ev with solar, is cheaper/more efficient to spend 5000 on solar at home and charge at home than spending 20000 putting solar on the car itself.

Click to expand...

I'm guessing you did not read the part where I say that since I live in a condo, I have no access to roof.

He lives in Honolulu. The angle is optimal.
A roof rack with extensions so it spans front to rear bumper of the car, then you're talking. With rigid panels, maybe 4x 300W for 1200W, making 5kWh to 6kWh/day. That's 8 HP for an hour, might get 30 miles out of that. (so long as you park where there isn't any shade.)

Solar electric vehicle said:

... so how is sono sion claiming their pv on car will generate 15 to 20 miles / day?

Click to expand...

Sono sion looks like they're utilizing every square inch of the car that they can for PV. You're hoping to put 1 panel on a car and it do the same? They're also only claiming that in certain parts of the world and at certain times of the year, not in Alaska in December

A neighborhood electric car (golf cart) with panels on top could be quite practical in a suitable location.

Lt.Dan said:

Sono sion looks like they're utilizing every square inch of the car that they can for PV. You're hoping to put 1 panel on a car and it do the same? They're also only claiming that in certain parts of the world and at certain times of the year, not in Alaska in December

Click to expand...

no, I was not hoping to get the same results with far fewer panels.
1. I know panels will mean car can be plugged in less. And I realize there are many factors - size of vehicle, amount of panels, where car is parked, driving patterns, and more.
2. My actual question was are there any issues - wiring, charging while in use - no one has mentioned any, so I assume there are none.

The island of Oahu is small - and sunny - so actual driving distances are often much less than on the U.S. mainland. And a lot of people here live in condos or apartments (no roof access). While adding panels to a car there might produce a negligible benefit, here, it could be a game changer. Imagine if instead of having to charge your EV every 4 days, you could charge once every 8 days? or, based on my driving patterns, charging 1 time / month rather than weekly?

Anyway, thanks for all the helpful comments.

Hedges said:

He lives in Honolulu. The angle is optimal.
A roof rack with extensions so it spans front to rear bumper of the car, then you're talking. With rigid panels, maybe 4x 300W for 1200W, making 5kWh to 6kWh/day. That's 8 HP for an hour, might get 30 miles out of that. (so long as you park where there isn't any shade.)

Click to expand...

would love to see how you fit 4x300w panels (170x100cm each) into a car. you cant even fit that in some RV's

x4dow said:

would love to see how you fit 4x300w panels (170x100cm each) into a car. you cant even fit that in some RV's

Click to expand...

170 cm across, 5.6'
4 x 100 cm long, 13'

"A roof rack with extensions so it spans front to rear bumper of the car"

It may look silly, but it will work.
Neighbor has had something like that for 20 years. His is actually one on the hood, couple more sloped over the roof.

Hedges said:

170 cm across, 5.6'
4 x 100 cm long, 13'

"A roof rack with extensions so it spans front to rear bumper of the car"

It may look silly, but it will work.
Neighbor has had something like that for 20 years. His is actually one on the hood, couple more sloped over the roof.

Click to expand...

If the car is parked in your land, yes.
In the public road? Leggaly? No

x4dow said:

If the car is parked in your land, yes.
In the public road? Leggaly? No

Click to expand...

Legally?
What law? What land?

Only problem I know of is some HOA having rules regarding roof racks; they object to commercial vehicles.

If your Tesla uses 300 watt hours to go 1 mile, as the model S is supposed to, the only way you’ll get production to make any difference is like @Hedges said and add extensions. I’ve had bad luck with winds, so these extensions would need to be wind worthy.

There’s plenty of flexble panels out there for less than $400 per 100 watts. I picked up Renogy 175 watt flexible panels at $285 delivered to my door. Because of the less than optimal angle, these panels have produced perhaps 100 watts max.

I would expect to get 500 wh of power out of that 175 watt solar panel, which for the 300 wh per mile, my 175 watt panel would get you 1.4 or so miles. IMO, that’s why you don’t see them on the roof. From my limited experience in Hawaii, out on the coast you’d be closer to that output, but inland, I remember much more clouds.

So, I guess if I parked outside all day, I could drive to my Walmart and back, less than a mile away, and the panel would push that energy back in. If Walmart didn’t have what I needed, I’d drive another 1/4 mile to the supermarket and be in the hole for the trip.

That doesn’t even cover the charge controller portion, which I think would be a lot harder than hooking your typical SCC to the battery.

It’s an awesome idea. If it could have been done, suppliers would have exploited it by now.

Randomly picking Denver Colorado, in the summer the insolation for a flat mounted panel is 6.70 and 2.18 for winter. So, say the use case is you drive 15 miles to and from work, the car charges while parked in the parking lot with 3x175 watt panels normally kept in the frunk. Say you work long hours (e.g., dawn to dusk) and mount the panels over your car downtown with no shadows while you work and car consumes 300 watt-hours/mile. How many miles would you get not including conversion and round-trip losses?

Theory

Practice
Zero... downtown someone would steal the panels. ?

11.725 miles?
Double that with Hypermiling.
Not like he's going to go much faster than 20 to 30 mph in Honolulu
23 miles doesn't sound so bad, now does it?


I said 30 miles with 4x 300W panels mounted on extended roof rack. That would ruin the beautiful sculpted shape of a Tesla.
But they would look right at home on its predecessor, which Tom Hanks proudly displays:




(Putting the motor in a Lotus resulted in a much larger following)

Every watt is a plus in my book extending range provided the weight doesn't outweigh the mileage gain. Seems like the sun facing surfaces could all be light-weight ETFE encased cells. For example, Tom's Rav4 is 181″ L x 73" W. Taking off 2' for the windshield and back, and 4" of width off for curves, that's a surface area of 13'x5.75'= 74 sqft. Quality panels are around 18.8 W/sqft, so it would have ~1.4 kW array (16 W/sqft for ETFE, so 1.2 kW).

Not taking into account the amount of damage such flexi panels would take on a moving car. Chips. Getting covered in crap, mud, etc