What I have seen previously is that the amount of energy you get from the solar cells that you could fit on the top of the car is really small compared to what it takes to charge the battery.
Since there is minimal benefit, and it's costly to include them and wire them to the battery, it hasn't been viewed as worthwhile.
Yeah this is what I’ve heard as well. Aging Wheels goes into it a bit in this review of a concept car, kinda neat - it has pedals like a bicycle but the energy they add is a tiny fraction of what the thing needs to move.
Edit: oops, I’m combining two of his vids in my head, this one is just solar not pedals.
it has pedals like a bicycle
Are you taking about the Aptera from the video you linked?
If so, the Aptera doesn't have pedals like a bicycle. It's a fully electric vehicle (or it will be if it reaches production).
For comparison, my rooftop solar array, with around 16 full-sized panels (~6kwp) produces just under 2 miles per hour in my electric car (around 3.3kwh/mi). Or in real life, takes about 2 fully sunny days to produce the power to charge the car.
What kind of ev are you driving? That's insanely high energy usage.
My EV gets about 6km per kwh (around 4 miles)
Spot on.
Rough summary of when it is energy and effort efficient: https://xkcd.com/1924/
A few of them have. The core issue is it doesn't add much range, while at the same time adding more cost, weight, and complexity. On a sunny summer day you can expect to get single digit kilometers added to the range, while on a cloudy winter day you won't get even a full kilometer added.
They do make some sense on hybrids, as they are lighter so the range increase is a bit more and people are less likely to charge a hybrid. But, they still suffer from not adding much range, while adding cost, weight, and complexity.
Edit: Auto Focus did a re-review of the Fisker Ocean, which has solar panels. Linked to the timestamp where he is talking about them.
Bear in mind also that the extra weight and possibly aerodynamic compromises actually reduce range. In some cases, particularly at night, in poor weather, and at high speed, the panels would be a net negative.
They would only be useful if your car sat around in the sun for long periods without access to a charger.
such as parked at work or in a summer traffic jam?
Parked at work it will probably have a building nearby that creates a shadow. In a traffic jam, assuming perfect sun conditions and no shade, a 100W panel will generate around about 500m (or yards) of range per hour. Meanwhile the AC will use about 700W to 1kW of power to prevent your face from melting.
Some tests on YouTube report a realistic addition of 1 mile per day using the car in a typical commute.
Depending on the car and the temperature, AC Is simply not an option (same for heat) in a traffic jam. I drove a 2019 Nissan Leaf (with 12/12 battery bars and normally 80-140 miles in range, depending on the season)for my 19 mile commute for a while, and had an awful time during subzero temperatures (~-20 Celsius) once. I went from fully charged on the work chargers to considering breaking out my reflective emergency blanket in three hour stop-and-go traffic so as not to kill my battery before home. I stopped to charge and it took much longer than usual, to the point that I just gave up and used my hand warmers and hoped on the way home.
I don’t blame the car for that, I was unprepared for the predictable consequences of cold temperatures on electric cars, but it was still super unpleasant.
Doesn’t provide enough power for the cost of the cells, plus having to clean and upkeep them. And the more material you cover them with (to protect them; solar cells are INCREDIBLY fragile), the less efficient they are. I was on a solar car team in college and the cells are so fragile that to clean them, we had to use new microfiber cloths every time. Any dust would scratch and ruin them (which made it quite tough when I drove across the outback in the thing). We kept our cells completely uncovered because we needed maximum efficiency - but even with a super light carbon fiber solar car that’s got very minimal tire contact patches, specialized tires from Bridgestone, and a very aerodynamic shape (plus no amenities like A/C), I think our car could sustain something like 10-15 km/h on a perfectly sunny day in the middle of the outback. It just doesn’t add enough on a huge, heavy EV
So a solar golf cart might be doable?
The Fisker Ocean has solar panels on its roof. It can add 4 or 5 miles a day if fully exposed to the sun.
Not enough to matter. It’s a gimmick.
If you don’t have an EV, you may think that EV owners are worried about range, and they’d welcome any increase. I have not found this to be true.
It’s more like having a car that starts every day with a full tank. You’re never going to burn through that in a single day. Pretty soon you don’t care about range, efficiency, or pay much attention to the battery meter. It only matters if you’re on a road trip, which for me is a couple times a year.
I would not want to give up a nice full-roof sunroof for a few extra miles a day.
The newest revision of the prius has an option for rooftop solar. The break even point is relatively long, in the 5-8 year time frame iirc. The energy generation isn't massive; at 185w it won't substantially extend the range something like 5 miles per day.
Modern EVs such as Teslas have a high power consumption, much higher than some PV panels on the roof could deliver. Thus, it would only increase the weight of the car while not significantly increasing their range.
In addition to weight, there's cost. They would have to be integrated into the design, not just normal, flat solar panels, so there's a significant cost increase. It's no problem on a delivery van, but anything curvy is probably prohibitively expensive to develop and produce.
Aptera is doing this with custom solar cells and they claim it'll provide up to 40 miles of range per day. https://aptera.us/
I was about to say that. The main reason why they can do it is that Aptera went great lengths to make their vehicle as light and efficient as possible so what little charge they get out of the panels will make a noticeable difference.
This is a stark contrast with the other EVs on the market that are just huge heavy bricks on wheels that compensate for their inefficiency with bigger and heavier batteries.
Because the aptera is ridiculously efficient and they cover way more than just the roof with the panels. I love the car, but it ain't something I would consider mass market.
Plus, this again assumes you park it in ideal sun conditions, sun directly overhead (for the panel inclination), no shade anywhere around etc. Famous "up to" values.
Everyone saying how little energy a solar panel will produce in optimum conditions.
I don't think anyone has mentioned how difficult it would be to get optimum conditions for any significant portion of the day.
If you think about the places you park, how many of them have uninterrupted line of sight to the entire arc of the sun? Right now my car is parked on the street but it's in the shadow of a building.
Even if you have the option to park directly in the sun, would you?
Being in a car that has been heating up for several hours of direct sun exposure is grueling. Switching on the AC to cool down to acceptable temperatures will probably drain more battery then was gained by the solar panel.
While most of the points are covered here, and it's likely true that the cost to add the panel and micro inverters is high, (I built a small two panel one battery off-grid system for about $4000 to power a chest freezer)... I have a counter point that I feel should be considered.
While it's true that it isn't going to extend driving range by much, my thought is that it is still worth it. Take these examples:
Drove to great wolf lodge in the summer, left car in parking lot for 3 days without charge. It lost several %.
Left car in an airport lot for a week lost even more power.
Drove to NorCal, left car at Airbnb driveway, had to find charging despite the car sitting in very bright sunshine for 4 days.
Car camping
Apartment complex parking (literally one of the main negatives about EVs)
All of these would benefit from trickle charging, even if it was just to prevent the drain of sitting.
Solar panels on cars are thought of the wrong way. The responses in this thread really demonstrate that.
It's true that they're kind of pointless on EVs, because they're never going to supply enough power to not need a proper charge, which makes the panels redundant.
Where they could be useful is hybrids, sold as something that makes the engine 10-20% more efficient.
I think they should put windmills on the roof. If you're going down the freeway that would charge the battery real quick! /s
Obligatory windmills do not work that way, also that's exactly how an alternator works.
But... That's exactly how a windmill works.
Windmills don't generate electrical energy. For that you need a wind turbine.
Windmills don't generate electrical energy
What if you used them to grind pizeoelectric materials like quartz? 😌
TLDR solar panels have a lot of inefficiencies, which makes them more of a detriment to mounting on standard commuter cars when you take into account the effects of the added weight.
I remember looking at the Prius and it had a solar roof option. I remember reading a MotorTrend article about it. They had to make a lot of assumptions like 12 hours of sun everyday no exceptions and just to break even from the cost of the roof option it would take 5+ years. So not really worth it. You’d be better off just paying for the electricity or putting solar on your house and charging with that.
Edit…words missing
the solar panel was just to run a 12V fan to keep the car cool in the sun. it didn't charge any batteries.
The title of the article I linked and its subtext is
“The 2023 Toyota Prius Prime Could Take 3 Weeks to Recharge—Without Plugging In
Or, put another way, you can get more than 1,000 miles of free range in a year.”
It most definitely charges the battery.
Once upon a time Audi had solar panels on the roofs of their car and it could only generate enough power to run the cabin fan to try to cool the car down while you were parked.
To give you an idea of the sheer amount of power that an EV requires to move its bulk, look at the sizes of their batteries vs home battery packs. An EV has battery packs of around 100kWH and that can get you a few hundred miles range at most. Now compare that to the requirements of a home battery. The average use for an entire home is about 30kWH per day, and most home batteries only recommend 10-15kWH.
Looking at that you start to see the massive difference in power usage required. To charge a small home battery like that you usually need multiple panels (10+). They just don’t have the space and power generation to offset the sheer amount of power EVs require.
Because it barely matters. Like putting an extra AA battery in the glove box.
Well now the question is why they don't put an extra AA battery in the glove box.
The math doesn't work out unless it's an ultra light car. Check Aging Wheels video on the Aptera for more. The first few minutes, he covers the technical stuff on car mounted pv.
Wouldn't it better to just build more solars to power the chargers? It scales independently.
In addition to the other points about efficiency, there is also the maintenance and added weight in a high location on the car that would impact stability and safety. Keeping that slab or solar cells from majing a crash worse would be a large undertaking for example.
Solar panels now are like tube tvs. If we make a breakthrough on paintable or extremely thin and flexible solar cells like we did with the leap to flatscreen tvs then it would be much more likely as the costs come down even if they still provided only a small charge.
For range it doesn't add much in most cases. But it also depends on how long between journeys you have. If you're traveling in a van and you are going to be stationary for a few weeks at a time then it can start to make sense, maybe with an extra fold out.
The first generation Hyundai Ioniq 5 had solar roof (at least some models).
The first gen ioniq 5 also had a very low payload capacity, with stories of families who couldn't legally be in the car at the same time without being over the capacity.
The reason, I'm told, is that supporting the solar roof reduced the payload capacity a lot.
Also, solar cells on a car doesn't make much sense like others have already said.
Assumption:
Someone crams a 300 watt solar panel onto the roof of their EV and manages to integrate it into the charging system so that it's pretty efficient to use that power.
Numbers:
One hour of good sunshine on the 300 watt panel = 300 watt-hours (Wh).
Average EV energy usage : 200Wh per kilometre these days. Maybe a little more, maybe a little less, depends on how and where you're driving.
Result:
One hour of perfect sunshine hitting the roof of your car equals 1.5 kilometres of extra range, or you can drive your car in a steady-state fashion at a 3-5 kilometres per hour because an EV is more efficient than the average usage at lower speeds.
Conclusion:
Probably better off increasing the storage capacity of the battery as a full day's sunshine will get you about 10 kilometres of range.
The new Prius Prime has an optional rooftop solar panel.
According to an article in Slash Gear you can get about 4 miles of range after 9 hours in the sun.
So it has the potential to marginally increase your range on the scale of a short commute under ideal circumstances, but it's not much apparently.
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