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It is so annoying when people tell me their genius idea, putting solar panels on a Tesla. Why doesn’t Tesla already do this, they wonder? Because the amount of

• VBprogrammer 7y ago
  One way of helping people internalise this is to point out that 1ph is, to a first order approximation, 1kw. The same as many electric heaters. A typical solar panel is 100w in peak conditions. It's then easy to visualise what powering something with solar panels might entail if you can make a guess at the engine HP. Even a small ferry is likely 2000hp+.
  • jstsch 7y ago
    Yeah, that’s a good way of looking at it. Note that a typical modern solar panel is around 285-340 watt these days.
  • Faaak 7y ago
    > A typical solar panel is 100w in peak conditions That doesn't mean anything. A standard panel (1m×1.9m) has a peak power of 300W. What we must compare is the solar radiance times the efficiency of the panel, and multiplied by the surface, would give you your available power
    • VBprogrammer 7y ago
      And 1hp is actually 745.7w. It makes very little difference with regards to the big picture of whether something is feasible. Whether you tell someone the ferry is going to need 20,000 solar panels or 5000 it's still way more than reasonably be put onboard. The solar factor usually employed in the UK is about 0.1 to get from nameplate capacity to actual production (accounting for hours of darkness and suboptimal atmospheric conditions) so it would be reasonable to assume your 300w is actually more like 30w. At least some percentage of solar panels on our hypothetical solar power ferry are likely to be in shade or not pointing directly at the sun. Then you have various conversions and charging losses to get the power into a usable form.
      • Faaak 7y ago
        I was talking about the assertion, not about if it was feasible or not.
        • VBprogrammer 7y ago
          I was talking in broad strokes about how to encourage someone to have an intuition of the power requirements for such an endeavour. I was using easy round numbers not asserting exact numbers.
  • masklinn 7y ago
    Note that the solar panels are not necessarily the primary energy source, they can do trickle-charging, range extension and/or emergency recharge / supply (e.g. when you've run out). These are roughly the use cases lightyear one tends to cover, under a somewhat ideal 12km/h WLTP (that is in good sun the panels can charge 12km worth of WLTP range per hour, which can extend the range during a drive, recharge a parked car or let you drive at 10~12km/h when the batteries have run out).
• moksly 7y ago
  We have a few electric ferrys in Denmark, so it’s certainly possible, but they obviously aren’t charged by onboard solar or wind power.
  • billpg 7y ago
    Wind power ferries. I think they tried that in the days before electrical motors.
    • alanh 7y ago
      :D
  • SloopJon 7y ago
    There's an article in a recent issue of IEEE Spectrum about a plug-in hybrid ferry: https://spectrum.ieee.org/transportation/marine/happiness-is-a-hybridelectric-ferry https://spectrum.ieee.org/transportation/marine/happiness-is... It can cruise purely electric, although with just 100 kWh of battery capacity, the net result is a 30% reduction in diesel consumption.
  • aembleton 7y ago
    There's a good video on a Denmark to Sweden ferry that is fully electric: https://www.youtube.com/watch?v=rE_M1n-ClOA https://www.youtube.com/watch?v=rE_M1n-ClOA
• drawkbox 7y ago
  Why Teslas don’t—and can’t—have solar roofs [1] The top of an electric car has maybe 3–5 square meters of flat space. Solar panels, even at high noon, usually only produce about 200 watt-hours per square meter. The most efficient production electric vehicles today (probably the Hyundai Ioniq and the Tesla Mod 3) would only be able to travel 2–4 miles on that amount of electricity…in an hour. Most people could walk faster. Financially, the cost of the panels and electronics, R&D and assembly would never pay for itself in the life of the vehicle, compared to charging from the wall in your garage. While it might be nice to have for cars that sit there for a while or in the apocalypse. Right now it is better to use home solar panels or charging, as they have more surface area. Or maybe build parking structures with panels that can charge with more area. Maybe one day when they are small enough or can pull in sun into a smaller surface areas it will make sense. Solar panel cars would probably also really up insurance rates and add more safety work/R&D. [1] https://qz.com/1482588/why-teslas-dont-and-cant-have-solar-roofs/ https://qz.com/1482588/why-teslas-dont-and-cant-have-solar-r...
  • hrktb 7y ago
    Isn't it a case of the better killing the good ? From your excerpt is seems electric panels still give 2-4 miles of range per hour of charge. Even taking into account the added weight, it's a net positive so why dismiss the idea completely ?
    • nullymcnull 7y ago
      Read it again: > would only be able to travel 2–4 miles on that amount of electricity… in an hour. Most people could walk faster.
      • hrktb 7y ago
        I got it wrong the first time, then got it at the second take, thought I had it wrong again reading your comment and turned around again. The writing was weirdly misleading. > Solar panels, even at high noon, usually only produce about 200 watt-hours per square meter. > The most efficient production electric vehicles today (probably the Hyundai Ioniq and the Tesla Mod 3) would only be able to travel 2–4 miles on that amount of electricity…in an hour. Most people could walk faster. From what I get: - in the best conditions the panels could produce 200W in an hour - 200W would allow for 2-4miles on the most efficient cars The author's point seems to be that if the solar panel was the only source of energy the car would be slower that walking. It's different from seeing it as an additional source of electricity, just like regenerative braking is for instance.
• Cthulhu_ 7y ago
  Yeah, what Tesla is doing instead is investing heavily in the infrastructure - charging stations, batteries, and I don't know if they operate solar power fields but they also do solar panels and installation. So if anything, Tesla is doing a lot with solar panels already - just not on their cars for the aforementioned reasons.
• narrator 7y ago
  My favorite "genius idea" that comes up regularly is to have people running on treadmills and pedaling stationary bikes use the power they generate to power the gym or whatever. The amount of energy that treadmills and stationary bikes can generate from human power is absolutely trivial. Even given high electricity rates, it's worth about 3 cents an hour. The energy generated can barely power basic electronics on most self-powered exercise bikes.
  • biztos 7y ago
    Also, treadmills aren't powered by the people on them, but rather use a lot of electricity to move the tread (and usually a tiny bit more for the electronics).
    • narrator 7y ago
      They have self-powered treadmills. They're not very popular though: https://www.woodway.com/products/curve/ https://www.woodway.com/products/curve/
      • faceplanted 7y ago
        Yeah, they're really weird an uncomfortable until you get used to them, so people just see them as worse treadmills. All I really want is a stationary bike that powers a fan pointing at you to cool you down because I'm a sweaty bastard.
        • usrusr 7y ago
          That has been done many times. Products like Racermate Wind Load Simulator in the 1970ies, more recently the CycleOps Wind or the Lemond Revolution. In fact, all "trainer" devices where a regular bike is attached for indoor use are still colloquially called "turbos", in fierce defiance of Elon Musk's sudden love for semantic precision. They all suffered the same fate: when the hundreds of watts a well-trained athlete will produce during interval training is put into air movement, the noise is just unbearable. Much quieter setups are possible with more direct conversion to heat and even there, noise is still the dominant product metric.
• walrus01 7y ago
  To gain an understanding of what a near-useless idea it is to put solar panels on a tesla, go here: https://pvwatts.nrel.gov/ https://pvwatts.nrel.gov/ plug in a prototypical 1000W PV system at your latitude and longitude, as if it's on the roof of your house. That would be four 250W panels. Look at the kWH produced per month in mid summer, and again in mid winter. Using Seattle as an example, estimated production of 147kWh per month in mid summer, and 34kWh in the worst month of winter. Now look at how many kWh the capacity of a tesla battery (70 or 90 or 100kWh) is for a single full charge. 147, divide by 31 = 4.74kWh per day Those estimate figures for pvwatts are pretty rough, but they also calculate based on having near direct sunlight from sunrise to sunset, as if the PV panels are on the roof of a building or an unobstructed ground mount. Cars are frequently in the shade. Realistically, if you were to somehow magically cover a Tesla in 1000W of PV, and it was all flat-angled optimally to catch the sun, you might get 3kWh a day if you were really lucky. There is really no practical reason why the photovoltaics needs to be ON the car. Putting high efficiency pv cells on curving surface is expensive and hard. The PV can be on a roof mount covering your closest grocery store, home depot, car repair garage, public school, and so on, feeding the grid.
  • 0-_-0 7y ago
    If, on the other hand the solar panel would unfold during parking over the parking space (like spacecraft unfold their solar panels in orbit), you could get about 5 times more power... and you car would always be in the shade.
    • dwighttk 7y ago
      That sounds heavy
• H8crilA 7y ago
  This, unfortunately, extends to the rest of the world's energy usage: https://en.m.wikipedia.org/wiki/World_energy_consumption https://en.m.wikipedia.org/wiki/World_energy_consumption Don't buy any coastal property! Unless you're 70 and don't care about leaving anything behind. The sea water will come.
  • tim333 7y ago
    The Intergovernmental Panel on Climate Change's high end estimate is 90cm sea level rise by 2099. So if your costal property is at least 90cm above the water you might still think about it.
    • 9HZZRfNlpR 7y ago
      You can buy land high enough on the coast so your offsprings will get rich. Obvious you need free money to do that.
• akerro 7y ago
  >If the car is driven four days a week for a maximum of 50 kilometers a day, there’s no need to plug into an outlet, NEDO’s Yamazaki said. 50km is just as many kms as I commute to work during a week. Perfect prototype for me already. For longer trips I prefer motorcycle.
  • osobo 7y ago
    Unless you park in a garage, which a lot of people do.
    • kungtotte 7y ago
      And a lot of people don't. There's way more cars than there is garage space.
      • NicoJuicy 7y ago
        So everyone will park in the sun and not near trees or buildings. Garage is just one example where there is no sun.
        • kungtotte 7y ago
          Yes, and since this is a product specifically marketed to people who live in the area of the world where 100% of parking spaces is shaded it's obviously a bad idea. What if they instead sold it to people who usually park in non-shaded parking spaces? Would that work, do you think?
    • jameshart 7y ago
      Parking garage at my office park doesn’t even have open-air spaces on the top floor: the deck is covered with solar panels.
  • philipps 7y ago
    I wish more people would respond to this comment rather than debate the benefits of putting solar on a ferry. Is there data on the avg commute distance in different cities? 50km seems like a significant distance and could cover a large number of commuters.
• p1necone 7y ago
  What about a decent sized solar array + batteries at each ferry terminal, and relatively fast transfer to the ferry of however much power is needed for the trip.
• kalleboo 7y ago
  The Prius used to have an option for a solar panel roof before (the article mentions this) - and all the tiny panel was used for was to run the cabin fan to keep the cabin a bit cooler if you ended up parking in the sun. The difference with the cells in the article is they are 0.03mm thick so they don't weigh as much and can be curved around more car body parts.
• agumonkey 7y ago
  wait until Elon makes car solar tiles. Tesla Scales (c) me. It's true a car surface is ridiculous. Now on a van, bus or truck .. this could make for some nice juice.
• mtgx 7y ago
  By the looks of it, Toyota prefers to put a several thousand dollar solar panel gimmick on its cars instead of actually extending the range of its cars' batteries by the same amount. After all, Toyota has yet to accept that full EVs are the future, even begrudgingly, as others have. Toyota is currently betting on "hybrids".
• Amygaz 7y ago
  I am thinking that this is mostly marketing. Plus, installing PV on a car is not new. Half the top tier engineering department in the US have a setup for that, some are nearly 20 years old. But PV have come down in price, they’re still not very efficient, and the benefit will be marginal. I’d rather install PV on every parking lot instead, that way it is always connected to the grid. Unlike the car which is only connected when plugged in.
• finnthehuman 7y ago
  > It is so annoying when people tell me their genius idea, putting solar panels on a Tesla. Why? People are wrong about stuff all the time. Often more committed to worse ideas than this. What about this particular instance of them being wrong annoys you so?
  • labmachine 7y ago
    > What about this particular instance of them being wrong annoys you so? While I can't speak for the person to whom you're replying, I can tell you why it is annoying to me, and that is very simple. In this thread there are basically two kinds of posts: 1. Posts about the physics of why solar on cars is basically a bad idea (or at least a massive waste of money in the face of much better alternatives). 2. "Yes, but have you tried turning your head sideways and squinting at it like this [...]" For some reason, solar-on-cars brings out the #2 in many otherwise smart people, and it's extremely tiresome to constantly slap down the nonsense. Because, I think, they really, really, really want to believe it can work. > People are wrong about stuff all the time. Often more committed to worse ideas than this. Yes, but when you show them why those ideas can't work, using numbers and science, they abandon those ideas.
    • bradjohnson 7y ago
      > Yes, but when you show them why those ideas can't work, using numbers and science, they abandon those ideas. This is empirically not true: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.357.4138&rep=rep1&type=pdf http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.357...
  • raisedbyninjas 7y ago
    There is probably selection bias in the sort of person who would think it's a genius idea and an oversight by thousands of engineers for decades. Then account for the type of person that would make such a statement to a stranger. I'm guessing this set of people can be a bit annoying in general.
• maxsilver 7y ago
  > Because the amount of energy captured by such a minuscule surface area would barely recoup the inefficiencies of the added weight Is this actually true? Solar Panels don't have to power 100% (or even 20%) of the car to still be super useful on an EV. An EV with a solar array that generated just ~0.7kwh during 6 hours of daylight, would still be charging itself an extra ~20 miles of range per day while parked. That's significant enough to be worth it to me. And that range can add up (imagine being parked at the airport for 3 or 4 days, and having an extra 60+ miles of "free" range sitting on your car when you return) Alternatively, that electricity could power an AC outlet or an air conditioner for camping trips or remote work while parked or whatever. "Dog mode" could keep parked cars safely cooled without draining any range. My EV sits outside an office, in direct sunlight, nearly every business day. And it's battery covers 70% (but not all) of my daily commute. Even if solar panels aren't the most efficient use of that space, surely they're better than nothing, right? Every watt from that solar panel, is a watt I didn't have to pull off the grid, or an ounce of petrol I did not have to burn.
  • mattmaroon 7y ago
    You're not far off on the math for the most efficient cars, but I can't even get that much solar on top of a 23' camper, and that's with full sun and assuming I can park directionally. You're talking about 80 sq ft. Even taking into account these more efficient panels, you're looking at maybe 10 mi a day range added, best case. And that's assuming you're parking outside at all while at work. In suburbia you might be. Good luck in any big city. Overall I don't see how this is going to be economically efficient any time soon, even in the best use cases. It seems better to have fixed solar and a plug. But I hope I'm wrong.
    • aembleton 7y ago
      There's also the extra weight involved. If you used that extra weight for more batteries instead of solar panels, you might have even more range.
      • jfengel 7y ago
• dboreham 7y ago
  I've sailed on ferry type boats in Norway that were electric. However they were charged from the grid when docked via two 415V 3-phase connections at hundreds of Amps. Power from hydro, of course.
• bobloblaw45 7y ago
  Yeah there was a new building built in our city with wind turbines on top that everyone was impressed with because "They could generate their own power." The thing is that I remember hearing that the amount of energy wind turbines can generate depends on how big their blades are and these turbines looked really small. It took some digging but eventually I found an article that said the turbines will generate less than 5% of the buildings energy requirements at full speed. I mean that's not terrible, but then again they spend a lot of time not spinning at all let alone full speed...
• bobthepanda 7y ago
  Curious, but would the larger surface area of a bus or a truck be more suitable?
• Justsignedup 7y ago
  Slightly different motive though. If your car is hanging out all day at a parking spot, say in front of your office building, or just on the streets, it might actually charge a large battery enough to get you a chunk of the way through your trip. It could make plug-in hybrids the norm, even if you don't have a place to plug. For many people, their cars sit idle 80% of the day, if not more. Even if it charges enough for a quarter of the way to your house, that's a quarter more of not needing fuel. Right now I fill up my regular prius once a month. With this I can see that changing to once every 3-5 months. A potential of course, not saying this will work. That's the idea behind it. Not to power it as it drives.
• cr0sh 7y ago
  > BTW, if you take the ferry to Alcatraz, they will try to impress with you solar panels and a helical wind turbine on the ferry itself. I missed that the time I went to Alcatraz - but it was probably because it was a night tour...
• johnrgrace 7y ago
  Do you know WHY you put solar panels on top of a car? Because everyone has the genius idea of putting them there. It isn't about how well they work, it's that people will pay more to buy a car with them.
• epigramx 7y ago
  > Tesla is sexy I found them banal in most cases, at least including 3. Also they are technologically pieces of shit in terms of value for money since it's not worth giving at least $60,000 for a car that isn't even enough for very long trips without stopping to recharge.