Submitted 5 months ago by Blubber28@lemmy.world to [deleted]
Honestly it seems like a no-brainer to me to put a solar panel on the roof of electric cars to increase their action radius, so I figured there’s probably one or more good reasons why they don’t.
Also, I acknowledge that a quick google could answer the question, but with the current state of google I don’t want to read AI bullshit. I want an actual answer, and I bet there will be some engineers eager to explain the issues.
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 sunny 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.
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?
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?
A 9v battery powered skateboard is viable if you pick the right combination of weight, speed, and distance. Doesn’t mean it’s going to change the world.
On the other hand: most cars are not moved 23h a day. They just stand around.
A lightweight solar panel could be a worthwhile range extender in at least some climates.
On the other hand: most trips are made to the exact same place, why move solar panels around when you could just leave them in place (especially if the car isn’t moving for 23hr)?
On the other hand: most cars are not moved 23h a day. They just stand around.
Ot doesn’t take much shade to have a signifigant reduction in the output of a solar panel.
Unless you are parking in an open field with no trees or tall buildings around your power generation will be signifigantly reduced.
Not that the amount of power generated by a panel the size of a car roof is not all that much, even under ideal conditions.
I’ve seen some prototype solar panels that roll up like a carpet for easy storage. Keep it in the trunk, lay it out when you’re gonna be parked somewhere for a while.
And more weight means less range.
Having solar cells uncovered by glass is baffling
Yeah, it’s certainly a good thing it doesn’t hail in the outback lmao
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.
For an extra miles a day… if you park in the full sun all day every day. Garage? 0. Driveway? Probably shadow half a day.
if i park in the shade, and therefore don’t have to turn on the ac as soon as I get in, I think that would be about the same, savings wise.
Right. Unless you live in US and have relatives you regularly visit in a different city in the same state only 400km away.
I mean I still don’t care about solar panels on my roof and I’m much happier with a moon roof on my PHEV. Nearly 80km of electric range means I’m driving an electric car 99% of the time and have convenience of 5 minute fill ups when I go further.
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 increasing the 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. 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.
To put this in perspective… The Aptera claims it with charge at 13mph on level 1 charging. This means if you plug it in the a regular wall socket, you’ll get 13 miles of range per hour.
The full solar package(~2000 dollar add on) get 40 miles of range, per day, under ideal sunlight exposure. That’s roughly a little under 4mph of charging. With a purpose built solar setup, which covers the rear window and even puts solar panels on the dashboard.
The Tesla model 3 gets something like 4-5mph charging on level 1. The full solar package from Aptera might be able to add about 8-10 miles per day in ideal conditions.
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.
I’ve been following them for a while now and hope they can make it into production. Their focus on efficiency and repairability is quite exciting!
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 vaguely remember reading something about a Prius with solar panel on the roof. It was enough to run a small fan to keep the interior a little cooler
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.
Another really good point.
… a different way of looking at it is that it’s just way more practical to put solar panels in other places, like on the rooves of buildings.
Additionally, there seems to be an assumption amongst middle class suburbanites that everyone should just have roof top solar. Of course, the vast majority of humans to not have any roof space, because they live in an apartment.
I would also point out that my spell checker seems to think that the plural of roof is spelt “roofs” but I’m sure it ought to be “rooves” in the same way the plural of hoof as in part of a horse is hooves.
Being in a car that has been heating up for several hours of direct sun exposure is grueling.
Ahh, beach days with mum. I remember the warm sand, cool late water, and the layers of flesh burned off my young legs when we got into the car. Those days, we got our exercise writhing in place to avoid the worst of the burns until the car got moving enough to cool the seats down. Thankfully seat belts were optional, then.
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.
the question then becomes how much weight are you adding/energy are you consuming by having to carry the weight. I honestly don’t know and considering how heavy batteries are it is likely not that significant, but if you are only getting a few % charge a day then anything eating into that is going to hurt.
I still see some merit in a more utility style vehicle where you do expect to take it out camping, but for a daily commuter I think most people would prefer the sunroof to the trickle charging.
Also as an apartment dweller… I just wish they’d make normal wall outlets more available. Not everyone needs a proper fast charger but only having a few inconveniently located ones to fight for also sucks. But if more spots could just plug in and slow charge that would be a huge improvement
You seem to know what you’re talking about and I want to piggyback off this question to ask why they don’t harvest energy from the brakes or the wheels spinning. I always heard braking once could power a home for a day or something. And I assume if you put a passive spinning wheel power generator on each of the four wheels, you’d also produce a lot of energy. Are all of these things too heavy to have any benefit? Plus the wind passing the car as it drives…it just feels like there are a lot of missed opportunities for new energy production as the car moves that aren’t taken advantage of. What’s holding these ideas back?
Electric cars do charge when braking. Obviously the energy recuperated is less then waht was needed to drive that fast in the first place. Using driving wind would just increase the energy needed to drive that speed and would be net negative.
All newer cars do this. It’s called regenerative braking.
Most electric cars have regenerative braking. It’s not magic though, it takes more energy to speed the car back up than it recovers. Regenerative braking just makes stopping less bad for range. Sure you can go down a mountain and gain a lot of power, but not enough to go back up the mountain.
What car do you have? I worried about this for my Model 3 back in 2021, when it had some vampire drain. But if you don’t open the app on your phone, the car goes into deep sleep and it can be parek for weeks without a single 1% loss.
The problem is that this isn’t really even trickle charging. Customers would absolutely complain and say it’s not working because it couldn’t charge the battery more than 1-2% in an entire day of sun. EV batteries are 60kWh+ yet getting more than 2kWh/sq meter daily from residential panels is hard for much of the US. Add to that the:
One solution to the apartment street parking problem is adding charging ports to streetlights (they do this in Europe). But for most of US apartments there’s already dedicated parking space so also space for chargers. The unruly size of new vehicles is a much bigger problem in my mind, if there were actual motivation to fix this problem in government it would already be solved through some tax credits.
Replying to my own comment because I just stumbled upon uncle Rich doing exactly this on a cheap chinese EV truck.
It’s kind of a fun take on the crappy truck too. youtube link
the solar panel was just to run a 12V fan to keep the car cool in the sun. it didn’t charge any batteries.
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.
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 and equipment.
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.
Then you can use your glovebox battery to jump your main battery when you leave the light on!
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.
That does indeed make sense, thank you (and many others) for the answers!
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.
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.
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 wstt-hours (Wh).
Average EV energy usage : 200Wh per kilometre these days.
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 few kilometres per hour.
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.
Look at the Fisker Ocean, it adds almost no range or energy, and leaves horrible and distracting shadows on the passengers. Youat as well ask why you can’t charge a car with a D battery.
The Dutch have been working on this for ages : lightyear.one
I don’t remember what car it was but an ex’s car had this. It was only really used for keeping the car from getting way too hot while it was off in the summer.
If the solar panels could be efficient enough to run the air conditioning, I’m sold lol
My Prius has this. It literally just runs a small fan in the summer to keep the interior/batteries cool.
There are some, but as mentioned several times, the traditional car is too heavy for solar panels to be effective. There are some vehicles that are essentially enclosed motorcycles like the Aptera where it can be effectively used, though. Aptera can use solar panels effectively because even at their largest battery capacity, it’s still significantly lighter than an EV sedan.
The amount of power you could pull from a single square metre of solar on the roof wouldn’t increase your range meaningfully.
What it would do, is that you could possibly keep your starter-battery from going dead-flat if you left your car alone for a 1/2 month, in the summer ( snow would cover it, obviously ), & since bringing a lead-acid battery to dead-flat permanently-damages it, this would prevent costly problems for the car-owners.
( this happened to a friend with a Prius: had to replace the battery, and the damned thing was inside the rear wheel-well??? in a little compartment.
Origami-engineering’s … simultaneously incredible & stupidly-frustrating )
I’ve held for years that they should be doing it to keep the starter-battery trickle-charging, but … why make the customers have fewer costly/frustrating problems?
on the roof doesn’t make much sense. What I did see the CSIRO testing was a portable solar array that you could roll up and store in the boot. IIRC they drove a Tesla across a large swath of Australia stopping and only charing on the portable array as needed
I had similar ideas using a VAWT, mount it on. A speaker tripod, set it up to catch the evening and morning turn over. Maybe catch a trickle charge.
They have them on some international models of Hyundai electric cars. It’s not nearly enough to power the car or charge the battery, though. It’s more to just slow the battery down while it powers low-power things and look cool (it’s part of the trim package).
Even on ideal conditions (close to the Equator, no clouds) like in Northeast Brazil, you only get 5.5 to 6.0 kWh/m^2 of Solar energy, which means the roof of a small car, with 1 m^2 of solar panels, would only generate that amount of electricity if they were 100% efficient. That’s just 10% of the battery capacity of a small EV, like a BYD Dolphin.
My point is, even if solar panels doubled their efficiency, they would still only capture about half the energy of the Sun (currently, the best panels are at 24% efficiency), which means only about 2.5 to 3.0 kWh per day.
Solar cells on a car have no real use. You would have to leave the car out in the sun for weeks to months to charge it up just once.
Seems worth offering as an option. If you can get 10-20 kms out of the solar panel in decent time it might be enough of an emergency precaution to give people who live outside of cities less reason to poopoo EVs
There’s two problems with this:
Panels are not free. They cost money to install, weight to move around, and prevent you from a mega-sunroof that most EVs have.
Second, if you think one inconvenient charge per month will make people outside of cities and disparage (for whom EV already offer the most advantages) change their opinion, I think you will be disappointed. Most of them formed their opinion by “but I don’t wanna!”, not by any logical thinking.
More like 5-10km, and then only on a sunny day in the sun, which would make the car uninhabitable due to the heat.
Better put a few square meters on the roof and use those instead of the 2-3m² you can place on a car at suboptimal angles and with the requirement to park in the baking sun.
Thanks for posting the question! Whole point of the community.
I think we’ll see more of this in the future as they continue to make progress on inexpensive “solar paints” and the like. It’s not a bad idea, it’s just that the tech level doesn’t show much bang for the buck…yet.
forgrytaboutit@lemmy.world 5 months ago
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.
whodatdair@lemmy.blahaj.zone 5 months ago
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.
youtu.be/DDmeqLEB9c0
NABDad@lemmy.world 5 months ago
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).
Bigfish@lemmynsfw.com 5 months ago
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.
BlameThePeacock@lemmy.ca 5 months ago
What kind of ev are you driving? That’s insanely high energy usage.
My EV gets about 6km per kwh (around 4 miles)
Deestan@lemmy.world 5 months ago
Spot on.
Rough summary of when it is energy and effort efficient: xkcd.com/1924/