Comment box Scope: summary, information Tone: neutral Opinion: yes Sarcasm/humor: none Sometimes we talk about solar panels on cars on this website, and the conclusion is generally that it's a...
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Sometimes we talk about solar panels on cars on this website, and the conclusion is generally that it's a novelty that doesn't work on regular cars.
But apparently, a new company has made an expandable solar panel roof rack array (compatible with a variety of EV models) that can provide a small but non-zero amount of range, completely off-grid.
LA-based startup DartSolar said its electric vehicle roof rack attachment adds 10 to 20 miles of additional range per day.
The roof rack adds 360 W of solar capacity when stowed for driving and can expand to 1000 W in a folded-out 1 kW array. The low-profile solar rack stands 1.5 inches tall and can expand in 15 seconds.
The unit is currently priced at $2,950. DartSolar said with a ten-year lifespan the product has an expected payback period of two years and a 5x return on investment.
If the payback time is really only 2 years, this is a great product. And it could get even better. Future technology:
“With advancements in tandem solar cell technology by companies like Kaneka Corporation and Oxford PV, DartSolar is currently designing a 3,000-watt solar roof rack capable of providing 30 to 40 miles of charge per day,” said DartSolar.
93% of car trips are under 30 miles, so a range of 10-20 miles is pretty useful. The rack seems to generate some solar power while driving, but you can physically expand it while parked to generate more.
Main use-cases:
In general, people who drive cars in the sun, and especially people who park their cars outside at home or at work. For example, if you work at an office park or shopping mall or construction site (etc), your car is probably sitting in the sun in the middle of a big, open parking lot for 8 hours a day, whether or not you park it in a garage at home (it's darker then anyway).
People driving to remote areas with some sun, such as going camping for a few days. The car is just sitting there. This way they have to plan less and range anxiety is less of a problem. Also the car interior would presumably not get so hot. Win-win.
People in cities who park outside but don't have consistent home charging access. For example, a residential rowhome neighborhood with street parking in Boston or Philadelphia. In a city, cars are parked for longer than average, and trips are shorter than average, so this could actually reduce reliance on public chargers by a significant amount.
In all cases, the solar panels aren't enough to completely remove the need for using public chargers, but it could help a lot, specifically for people who don't have easy access to home charging.
If you park in a garage 100% of the time, this is less useful except for camping. But in that case you aren't as much of the target market because, if you park in a garage, you have better access to EV charging on average.
Interested to see how this kind of product does in the market. It is available for pre-order currently, with delivery scheduled for 2025.
Agreed on pretty much everything you’ve said about the use case, but I am pretty dubious of their payback claims. Quick back of the envelope using $0.17/kWh (roughly the US average) would be...
Agreed on pretty much everything you’ve said about the use case, but I am pretty dubious of their payback claims.
Quick back of the envelope using $0.17/kWh (roughly the US average) would be $2/day of value at a very unrealistically optimistic 100% of the fully folded out power rating for 12 hours. Unless I’ve missed something crucial, that’s an upper limit of $1,460 of value in two years - and in reality you wouldn’t hit that even in lab conditions, let alone in actual use.
Even if you’re in the most expensive power market in the US I don’t think it’d be possible to get a two year payback in real use.
All that’s to say I still like the idea, and I hope it proves to be viable - but I don’t buy their financial claims as possible, let alone realistic. And that makes me more concerned about the truth of the rest of what they’re saying.
[Edit] Actually, I guess if they’re using commercial fast charging costs as the baseline rather than home charging that might get you to a two year payoff with very optimistic but still just barely plausible assumptions. Maybe. I’d still say it’d be pretty disingenuous comparing a solar trickle charger to a high price fast charger, but it’s the only way I can see their numbers working.
Comment box Scope: comment response, personal reaction Tone: neutral Opinion: yes Sarcasm/humor: none Good comment! I'm guessing they are making that comparison based on commercial fast charging...
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Good comment!
I'm guessing they are making that comparison based on commercial fast charging costs. Perhaps that is misleading, but maybe not, because their target audience is at least partially people who don't have access to home charging anyway.
So if the choice for EV ownership is to charge at commercial fast charging stations, or buy this solar roof rack, the roof rack might make sense as the baseline. I would prefer they were more transparent though.
I guess we'll see if it really works next year, when the panels ship. Unlike some other solar-powered car tech, a roof rack is relatively mechanically simple, so I don't see why it would be severely delayed.
I don’t think this is realistic for people without home charging. If even their higher end promised future product can get you about 30 miles of range after a full day of charging that’s barely...
I don’t think this is realistic for people without home charging. If even their higher end promised future product can get you about 30 miles of range after a full day of charging that’s barely any range. And that’s assuming you’re keeping the panels clean of dust and debris and pollen. You’d need to be someone who doesn’t use their car very much, less than daily, at which point you probably don’t want to buy $3k worth of extra kit. You’d be better served with a zipcar type of car sharing service or have some sort of battery trailer that you charge at home and then carry/wheel out to plug into your car instead.
Where this may find popularity is with off-roaders/overlanders who make a bit of a fetish out of being over-prepared. Though even then, 30 miles (less if you’re on unpaved roads and weighed down with cargo) means you’re basically spending multiple days camping to get enough charge to go anywhere. If you’re doing that, then again you might as well have a really big solar array that can sprawl over more area so you can get more charge out of your daylight hours. There’s no reason to be constrained by engineering considerations around being roof mounted and aerodynamic.
It could also be useful for micromobility type vehicles (think golf carts and e-bikes) since their battery packs are a lot smaller and, if it’s a shared service, you can have them deployed out there for longer with less charging downtime. But the design would be different if you were mounting it in the back of a bike or golf cart.
The product has a lifespan of 10 years (and realistically it'll probably last longer than that as long as it's well built), I think if it's able to pay back it's cost at all in its lifespan it's...
The product has a lifespan of 10 years (and realistically it'll probably last longer than that as long as it's well built), I think if it's able to pay back it's cost at all in its lifespan it's definitely worth it. Being able to add meaningful range to your car without needing to plug it in is a huge boon for a large portion of people in the US who want an EV but don't have a reliable way to charge it.
Even if this just reduces the frequency of needing to charge, it's worth the price for a lot of people.
Yeah, I can see value in the product even if it never actually pays for itself - if it works at all, which it seems like it probably should, I could see myself potentially spending that much just...
Yeah, I can see value in the product even if it never actually pays for itself - if it works at all, which it seems like it probably should, I could see myself potentially spending that much just to guarantee I always had a little bit of range and reduce how often I'd need to wait around for charging spaces if I lived somewhere with a lot of sun and not a lot of infrastructure.
I definitely still find the payback claims a bit offputting: I think that accounting for realistic use patterns and prices rather than the "is this even physically possible?" I was doing above you'd be looking at ~5 years to break even compared to using only commercial chargers, ~10 if using a combination of commercial and residential, and no realistic breakeven within the product's lifespan if primarily charging at home.
But that's potentially still fine! I'd see it as a convenience cost with any potential payback as a significant bonus, I just wish companies were a bit more honest about that kind of thing.
In other news, solar automotive paint is on its way. There have been giant leaps in perovskite-based solar power collection, and the claim is 20% efficiency, potentially 100% of driving needs for...
In other news, solar automotive paint is on its way. There have been giant leaps in perovskite-based solar power collection, and the claim is 20% efficiency, potentially 100% of driving needs for 30 km/day under ideal conditions.
I can't see hauling around the weight of extra collectors if this succeeds, though it's probably going to be a while before it's available outside the luxury car market.
Comment box Scope: comment response, personal reaction Tone: neutral Opinion: yes Sarcasm/humor: none Wow. I did not know that was physically possible. I would believe a claim of 20% efficiency,...
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Wow. I did not know that was physically possible.
I would believe a claim of 20% efficiency, and this would cover more surface area than roof panels. If this 1kW roof rack has a theoretical/ideal range of 10-20 miles, I think a 30 km/19 mi range is within the realm of possibility under similarly ideal conditions.
I'm guessing that this paste mixture is more expensive than typical production methods. But that is really interesting.
Every so often someone re-has this idea and the maths still never really works. If you have a bunch of cash to spend on solar panels it almost always makes more sense to put them on your house,...
Every so often someone re-has this idea and the maths still never really works. If you have a bunch of cash to spend on solar panels it almost always makes more sense to put them on your house, not your car. 1KW of charging is pretty useless for my relatively small batteried car, it would take almost 30 hours to get a full charge at that speed. That's about five miles per hour (aside: that mph is a meaningful unit to measure EV charging rate pleases me a great deal), which is only in ideal conditions and it is unlikely that ideal is possible for very long at all. The angle of the array is going to be suboptimal almost all of the time, for one thing, and that sort of thing makes quite a difference. So 3mph is probably more likely in summer and even less at other times.
Meanwhile a roof mounted array running at a better angle and utilising a larger area can be selling power back to the grid which I can later spend on charging my car. Or if I'm home I can dump a few kW into the car directly.
I don't believe a car mounted 3kW array will ever exist in any kind of actually feasible way. That's a LOT of area to balance on a very small roof. Certainly it wouldn't be something that could be deployed in a car park, not without taking up a bunch of additional spaces.
Aside from the few relatively niche use cases already mentioned elsewhere, I don't see this taking off particularly.
Comment box Scope: comment response, personal analysis Tone: neutral Opinion: yes Sarcasm/humor: none The target market for this sort of thing is people who don't have a house suitable for solar...
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If you have a bunch of cash to spend on solar panels it almost always makes more sense to put them on your house, not your car
The target market for this sort of thing is people who don't have a house suitable for solar panels:
Property renters who park their automobile outside at any time
Property owners who don't have an accessible roof (condos/apartments)
Property owners whose roof cannot really support solar panels (slate maybe, or any too-steep angle)
Property owners whose roof is shaded by large trees, hills, or buildings
Property owners who do have a roof, but can't necessarily charge their car from their house (urban rowhomes)
I would call camping a niche, but renters make up 32% of the population (US). That's not a niche, that's a major market segment. According to Statista, property owners in rowhomes, condos, and apartments make up something like 15% of homes purchased (I'm eyeballing that graph). So that is about 45-50% of the population in the US. 92% of US households have at least one car, and even if we pessimistically pretend that the average renter profile matches the car ownership rate of Washington DC (66%), that is still about 31% of the population. I'm not sure there exists reliable data on how many car owners park in garages, but a lot of garage owners don't park there anyway (18-87% don't, apparently). If we just call that 50% then we are still talking about a 15-17% market segment of all residents/car owners respectively, which is meaningful. (For reference, EVs as a whole make up a similar market share of total vehicles sold, and I would call EVs a significant part of the market.)
Now, the current market that could be captured by this tech is fairly low, but mostly only because EVs are too expensive to begin with, and not too many people have them. It would be like 3% of the population, which is not nothing, but certainly not revolutionary. But in some ways it seems like a chicken/egg situation. It's reasonable to think that more people would be tempted to get EVs if the cars could charge themselves at least part of the way, because that removes friction for those adopters.
So 3mph is probably more likely in summer and even less at other times.
I don't think the purpose of this is necessarily to get a full charge, but I agree with you that any figures they're presenting are rosy. I think this could work very nicely for someone in Phoenix who mainly drives short distances to the grocery store or other amenities, but not to other cities. For example, a retired person, or a student/working-age person who lives 5-10 miles from school/work.
A lot of people don't drive daily. In the city I live, I often see cars parked in the same spot for a week at a time or more (sometimes a month... or more). They're not abandoned, people just overestimate how much they need a car so it's idle a lot. That gives more time for charging and makes the use-case more valid.
For people who drive longer distances regularly, or live in places that aren't so sunny, it is less appealing. I bet someone who works in San Francisco and needs the car to get to the office 2 days a week could still get value out of this. But someone who lives in Buffalo, NY and drives 30 miles every day, IDK, doubtful.
I don't believe a car mounted 3kW array will ever exist in any kind of actually feasible way. That's a LOT of area to balance on a very small roof.
The efficiency of solar cells is increasingly rapidly, which seems to be what the company making this is counting on. We will probably be seeing a lot more perovskite panels in the near future (that material is on probably the best and fastest trajectory). I actually think that perovskites are more suitable for vehicles than homes because their many weakness is a shorter lifespan, which a car also has. But they are becoming more durable either way.
I don't think the exact roof rack in this article will dominate the market, but a better one could. If they can produce a 1kW array with current panels, I don't think it's unreasonable to think that a 2kW or 3kW panel could exist with some sort of multi-junction perovskite chemistry. The theoretical efficiency limit of such a panel is about 86.8%, which is considerably higher than the typical efficiency of a cell these days (maybe 20-25%). I'm not sure what the efficiency of the panels used in this roof rack is, but I'm guessing it's about average.
A 2kW or 3kW rack might require slightly greater surface area. From the images in the article, they could manage that given average vehicle length. Possibly array options with even more panels could be introduced for people who have more space.
There is definitely a hard limit for vehicles though. At a certain point you would have to start thinking about buying a more lightweight or inherently fuel-efficient car for panels to be increasingly effective.
You are talking about me. I park within a block of my unit but don't park in a driveway or garage and dont have charging capacity at home. I don't work at an organization with parking for...
You are talking about me. I park within a block of my unit but don't park in a driveway or garage and dont have charging capacity at home.
I don't work at an organization with parking for employees.
I live where there is quite a bit of sun most days.
Being able to generate emergency charge using time and sun might help me overcome my resistance to buying an EV.
I've been hoping something like this would come along. I just wish that it was more rounded to fit the top of my car, though I do understand the shape. I love that I can charge my car for free...
I've been hoping something like this would come along. I just wish that it was more rounded to fit the top of my car, though I do understand the shape. I love that I can charge my car for free while I'm at work and gain back the miles I drove to the office.
I’m wondering about how much having something on the roof increases wind resistance. If it increases range, I guess the increased power makes up for it, but under what conditions? At highway...
I’m wondering about how much having something on the roof increases wind resistance. If it increases range, I guess the increased power makes up for it, but under what conditions? At highway speeds, wind resistance is a lot more.
Comment box Scope: comment response, information, personal reaction to information Tone: neutral Opinion: yes Sarcasm/humor: none I had the same question. According to the company's website, it...
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I had the same question. According to the company's website, it has "1-to-2% drag loss as measured in 72 degrees, 40 psi tires, at sea level." It's only like four inches high, so this makes sense.
For comparison, a rooftop carrier could reduce fuel economy by more like 25%.
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Sometimes we talk about solar panels on cars on this website, and the conclusion is generally that it's a novelty that doesn't work on regular cars.
But apparently, a new company has made an expandable solar panel roof rack array (compatible with a variety of EV models) that can provide a small but non-zero amount of range, completely off-grid.
If the payback time is really only 2 years, this is a great product. And it could get even better. Future technology:
93% of car trips are under 30 miles, so a range of 10-20 miles is pretty useful. The rack seems to generate some solar power while driving, but you can physically expand it while parked to generate more.
Main use-cases:
In all cases, the solar panels aren't enough to completely remove the need for using public chargers, but it could help a lot, specifically for people who don't have easy access to home charging.
If you park in a garage 100% of the time, this is less useful except for camping. But in that case you aren't as much of the target market because, if you park in a garage, you have better access to EV charging on average.
Interested to see how this kind of product does in the market. It is available for pre-order currently, with delivery scheduled for 2025.
Agreed on pretty much everything you’ve said about the use case, but I am pretty dubious of their payback claims.
Quick back of the envelope using $0.17/kWh (roughly the US average) would be $2/day of value at a very unrealistically optimistic 100% of the fully folded out power rating for 12 hours. Unless I’ve missed something crucial, that’s an upper limit of $1,460 of value in two years - and in reality you wouldn’t hit that even in lab conditions, let alone in actual use.
Even if you’re in the most expensive power market in the US I don’t think it’d be possible to get a two year payback in real use.
All that’s to say I still like the idea, and I hope it proves to be viable - but I don’t buy their financial claims as possible, let alone realistic. And that makes me more concerned about the truth of the rest of what they’re saying.
[Edit] Actually, I guess if they’re using commercial fast charging costs as the baseline rather than home charging that might get you to a two year payoff with very optimistic but still just barely plausible assumptions. Maybe. I’d still say it’d be pretty disingenuous comparing a solar trickle charger to a high price fast charger, but it’s the only way I can see their numbers working.
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Good comment!
I'm guessing they are making that comparison based on commercial fast charging costs. Perhaps that is misleading, but maybe not, because their target audience is at least partially people who don't have access to home charging anyway.
So if the choice for EV ownership is to charge at commercial fast charging stations, or buy this solar roof rack, the roof rack might make sense as the baseline. I would prefer they were more transparent though.
I guess we'll see if it really works next year, when the panels ship. Unlike some other solar-powered car tech, a roof rack is relatively mechanically simple, so I don't see why it would be severely delayed.
I don’t think this is realistic for people without home charging. If even their higher end promised future product can get you about 30 miles of range after a full day of charging that’s barely any range. And that’s assuming you’re keeping the panels clean of dust and debris and pollen. You’d need to be someone who doesn’t use their car very much, less than daily, at which point you probably don’t want to buy $3k worth of extra kit. You’d be better served with a zipcar type of car sharing service or have some sort of battery trailer that you charge at home and then carry/wheel out to plug into your car instead.
Where this may find popularity is with off-roaders/overlanders who make a bit of a fetish out of being over-prepared. Though even then, 30 miles (less if you’re on unpaved roads and weighed down with cargo) means you’re basically spending multiple days camping to get enough charge to go anywhere. If you’re doing that, then again you might as well have a really big solar array that can sprawl over more area so you can get more charge out of your daylight hours. There’s no reason to be constrained by engineering considerations around being roof mounted and aerodynamic.
It could also be useful for micromobility type vehicles (think golf carts and e-bikes) since their battery packs are a lot smaller and, if it’s a shared service, you can have them deployed out there for longer with less charging downtime. But the design would be different if you were mounting it in the back of a bike or golf cart.
The product has a lifespan of 10 years (and realistically it'll probably last longer than that as long as it's well built), I think if it's able to pay back it's cost at all in its lifespan it's definitely worth it. Being able to add meaningful range to your car without needing to plug it in is a huge boon for a large portion of people in the US who want an EV but don't have a reliable way to charge it.
Even if this just reduces the frequency of needing to charge, it's worth the price for a lot of people.
Yeah, I can see value in the product even if it never actually pays for itself - if it works at all, which it seems like it probably should, I could see myself potentially spending that much just to guarantee I always had a little bit of range and reduce how often I'd need to wait around for charging spaces if I lived somewhere with a lot of sun and not a lot of infrastructure.
I definitely still find the payback claims a bit offputting: I think that accounting for realistic use patterns and prices rather than the "is this even physically possible?" I was doing above you'd be looking at ~5 years to break even compared to using only commercial chargers, ~10 if using a combination of commercial and residential, and no realistic breakeven within the product's lifespan if primarily charging at home.
But that's potentially still fine! I'd see it as a convenience cost with any potential payback as a significant bonus, I just wish companies were a bit more honest about that kind of thing.
In other news, solar automotive paint is on its way. There have been giant leaps in perovskite-based solar power collection, and the claim is 20% efficiency, potentially 100% of driving needs for 30 km/day under ideal conditions.
I can't see hauling around the weight of extra collectors if this succeeds, though it's probably going to be a while before it's available outside the luxury car market.
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Wow. I did not know that was physically possible.
I would believe a claim of 20% efficiency, and this would cover more surface area than roof panels. If this 1kW roof rack has a theoretical/ideal range of 10-20 miles, I think a 30 km/19 mi range is within the realm of possibility under similarly ideal conditions.
I'm guessing that this paste mixture is more expensive than typical production methods. But that is really interesting.
Perovskite-based solar cells are getting scary good in the lab.
Every so often someone re-has this idea and the maths still never really works. If you have a bunch of cash to spend on solar panels it almost always makes more sense to put them on your house, not your car. 1KW of charging is pretty useless for my relatively small batteried car, it would take almost 30 hours to get a full charge at that speed. That's about five miles per hour (aside: that mph is a meaningful unit to measure EV charging rate pleases me a great deal), which is only in ideal conditions and it is unlikely that ideal is possible for very long at all. The angle of the array is going to be suboptimal almost all of the time, for one thing, and that sort of thing makes quite a difference. So 3mph is probably more likely in summer and even less at other times.
Meanwhile a roof mounted array running at a better angle and utilising a larger area can be selling power back to the grid which I can later spend on charging my car. Or if I'm home I can dump a few kW into the car directly.
I don't believe a car mounted 3kW array will ever exist in any kind of actually feasible way. That's a LOT of area to balance on a very small roof. Certainly it wouldn't be something that could be deployed in a car park, not without taking up a bunch of additional spaces.
Aside from the few relatively niche use cases already mentioned elsewhere, I don't see this taking off particularly.
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The target market for this sort of thing is people who don't have a house suitable for solar panels:
I would call camping a niche, but renters make up 32% of the population (US). That's not a niche, that's a major market segment. According to Statista, property owners in rowhomes, condos, and apartments make up something like 15% of homes purchased (I'm eyeballing that graph). So that is about 45-50% of the population in the US. 92% of US households have at least one car, and even if we pessimistically pretend that the average renter profile matches the car ownership rate of Washington DC (66%), that is still about 31% of the population. I'm not sure there exists reliable data on how many car owners park in garages, but a lot of garage owners don't park there anyway (18-87% don't, apparently). If we just call that 50% then we are still talking about a 15-17% market segment of all residents/car owners respectively, which is meaningful. (For reference, EVs as a whole make up a similar market share of total vehicles sold, and I would call EVs a significant part of the market.)
Now, the current market that could be captured by this tech is fairly low, but mostly only because EVs are too expensive to begin with, and not too many people have them. It would be like 3% of the population, which is not nothing, but certainly not revolutionary. But in some ways it seems like a chicken/egg situation. It's reasonable to think that more people would be tempted to get EVs if the cars could charge themselves at least part of the way, because that removes friction for those adopters.
I don't think the purpose of this is necessarily to get a full charge, but I agree with you that any figures they're presenting are rosy. I think this could work very nicely for someone in Phoenix who mainly drives short distances to the grocery store or other amenities, but not to other cities. For example, a retired person, or a student/working-age person who lives 5-10 miles from school/work.
A lot of people don't drive daily. In the city I live, I often see cars parked in the same spot for a week at a time or more (sometimes a month... or more). They're not abandoned, people just overestimate how much they need a car so it's idle a lot. That gives more time for charging and makes the use-case more valid.
For people who drive longer distances regularly, or live in places that aren't so sunny, it is less appealing. I bet someone who works in San Francisco and needs the car to get to the office 2 days a week could still get value out of this. But someone who lives in Buffalo, NY and drives 30 miles every day, IDK, doubtful.
The efficiency of solar cells is increasingly rapidly, which seems to be what the company making this is counting on. We will probably be seeing a lot more perovskite panels in the near future (that material is on probably the best and fastest trajectory). I actually think that perovskites are more suitable for vehicles than homes because their many weakness is a shorter lifespan, which a car also has. But they are becoming more durable either way.
I don't think the exact roof rack in this article will dominate the market, but a better one could. If they can produce a 1kW array with current panels, I don't think it's unreasonable to think that a 2kW or 3kW panel could exist with some sort of multi-junction perovskite chemistry. The theoretical efficiency limit of such a panel is about 86.8%, which is considerably higher than the typical efficiency of a cell these days (maybe 20-25%). I'm not sure what the efficiency of the panels used in this roof rack is, but I'm guessing it's about average.
A 2kW or 3kW rack might require slightly greater surface area. From the images in the article, they could manage that given average vehicle length. Possibly array options with even more panels could be introduced for people who have more space.
There is definitely a hard limit for vehicles though. At a certain point you would have to start thinking about buying a more lightweight or inherently fuel-efficient car for panels to be increasingly effective.
You are talking about me. I park within a block of my unit but don't park in a driveway or garage and dont have charging capacity at home.
I don't work at an organization with parking for employees.
I live where there is quite a bit of sun most days.
Being able to generate emergency charge using time and sun might help me overcome my resistance to buying an EV.
@mat
I've been hoping something like this would come along. I just wish that it was more rounded to fit the top of my car, though I do understand the shape. I love that I can charge my car for free while I'm at work and gain back the miles I drove to the office.
I’m wondering about how much having something on the roof increases wind resistance. If it increases range, I guess the increased power makes up for it, but under what conditions? At highway speeds, wind resistance is a lot more.
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I had the same question. According to the company's website, it has "1-to-2% drag loss as measured in 72 degrees, 40 psi tires, at sea level." It's only like four inches high, so this makes sense.
For comparison, a rooftop carrier could reduce fuel economy by more like 25%.