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.
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.
That's a big "if", though. Photovoltaic paint is currently around half as efficient as commercial solar panels.
https://www.walmart.com/ip/Solar-Sun-Powered-Power-Window-Fa...
What I would love to see is a Tesla that can act as a powerwall and power your house when the grid fails. Some people hack them to do that but it doesn't look simple or without risk.
Not only is this a backup for a rare outage but it makes you money by charging when power is cheap and selling back when expensive. Occasionally the price of power goes negative and you are paid to charge.
https://electricinsights.co.uk/ is good for exploring the energy data and pricing.
A solar panel to make it net neutral energy to keep cool would still be nice.
Basically, mount your panel, and install a block diode if it doesn't already have one, then run the wires (positive and negative) to your battery to keep it charged.
Then, all you need to do is hook up a switch to your blower motor inside the vehicle, along with a simple speed controller (for this, it's best to use a cheap 12 vdc PWM controller - don't try to use the "low speed" resistor if your car uses a resistor pack, as it might not keep it cool enough) - so you can turn it off and on, and control the speed of the fan - while the car is parked and "off" (no-key).
Park it in the sun (of course), set the vent controls to allow air in from the outside (hopefully it stays this way when the car shuts down - if not, you'll have to figure out a way around that), crack your windows slightly (1/4-1/2 inch), then shut off the car. Flip the switch and set the speed control for the fan to something "low" - the fan should run, but not at hurricane speed.
Then get out and close/lock the doors. Air will be drawn in from the cooler outside, blown into the cabin, and exhausted out the windows.
The battery will stay charged from the solar panel.
If you are concerned about the battery being run down when the sun sets, then:
1. You can optionally use a separate battery to the fan, with a blocking diode to keep the fan from using energy from the car's battery.
2. Or you can add a thermostat to detect and only run when the sun is beating down hot (this could be in addition to the PWM control - so the fan doesn't run all the time, only when the cabin gets too hot).
3. Add a photoelectric switch to disconnect the fan from the battery, when the sun goes down.
4. A simple way would be by just wiring a standard Bosch SPST automotive relay (the coil) in series with the panel, and the fan across the contacts - when the sun goes down, the relay would open up, and shut off the fan.
Note that this car ventilation mod does not require an Arduino, so you might not become popular or upvoted on the tubes, but your car might be cooler in the summer...
Assuming 0.7kwh in 6 hours of daylight, that means the solar cells are outputting ~115W. It's hard to estimate exactly how much power is needed to cool a Prius, but 115W seems far less than sufficient. Traditional car air conditioners run directly off of mechanical power from the engine for efficiency. Home window air conditioners typically draw 1000W-1800W. A Tesla user reports [1] that the Tesla electric AC takes 2.4kW when starting up and then switches to a steady state of ~600W. Looks like [2] the Prius climate fans on medium take up 100W without the AC even being on. Coming at this another way, using this online calculator if we plug in 250 cubic ft for an estimate of the Prius internal air volume, assume high-quality insulation, and a 25°F temperature drop, this online calculator says that requires 1500 BTUs or 450Watts. [3]
That said, solar panels would still help somewhat! I also like the idea of exposing more people to solar and increasing general awareness around energy consumption (and how energy-hungry ACs are). Hope they do make it market in some form.
[1] https://teslamotorsclub.com/tmc/threads/how-many-watts-does-...
[2] https://priuschat.com/threads/power-consumption.14026/
[3] https://www.calculator.net/btu-calculator.html?roomwidth=6.2...
An EV uses ~250wh/mile. This varies a bit for some, but none of them are going to come close to 20 miles in .7kwh. Maybe 3-4 at most.
The ability to use something like this when left parked at an airport would be nice, though. Though I suspect that readily available 120V outlets is actually a cheaper option in the long run, relative to deploying panels on every car.
That seems like a very realistic/feasible figure. (Lightyear One's claims their prototype car can pull almost 2kw per hour (7.5 miles of charge per hour), which at 6 hours, earns you 12kWh per sunlight-day)
It’s not “.7kW per hour”.
Watts is a measure of power, it’s already Joules/second.
You just want “.7kW”.
For 6 hours, you still won’t get 4kWh, because you need to adjust for less than ideal angle, and less than full sun days.
But if you got 3kWh on a good day, that’s still 10-12 miles of additional range.
Car environments tend to be worse than that due to the angle and likely regular proximity of even mild shading. Its certainly enough to eliminate vampire drain, which is helpful at times, but I don't see how it will add an appreciable amount of mileage otherwise.
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-r...
On a car it also acts as a range extender and emergency backup (if you're out of battery and the car is engineered for, you can crawl along at the charge rate or wait a bit for a better charge). It's not great, but being to "walk" with your car might save your ass.
And if the car is designed around this idea (à la lightyear one), you can increase things further (the LY1 folks advertise a solar charge rate of up to 7.5mi/h WLTP with no A/C).
Solar panels in a remote location need to be converted from DC to AC for transmission, then transmitted long distances with associated losses, then converted to DC again to charge the car, stored in batteries in the car with associated losses. A solar roof could actually be a net gain assuming the energy is used while the car is in motion, and it’s used near the equator so no tilt required.
Sure, the government or the electricity company could just install car chargers and put a solar plant to power that in some rural area. But if I want something now then buying a car is much simpler than lobbying for that.
If Tesla offered a "Solar Panel Kit" that made their cars even a few percent more efficient it would sell like hot cakes.
Pulling 600 W/m^2 from a PV panel may be theoretically possible, but the world record efficiency for a PV device is still less than 50%. To get above 40% efficiency you need to use very expensive multijunction devices and solar concentrators (i.e. not going to work on a car).
As solar panels have gotten cheaper installation costs have become more important which has pushed up panel efficiency. Cheap but good panels are up to ~23% efficiency where they where ~18% fairly recently. What’s interesting is these trends seem to be continuing with serious research into various affordable multi junction cells going on.
If you get the plugin Prius, you can already not pay for gas at all with short commutes. And it cost almost half of Tesla Model 3.
The better way is parking it in a garage of small to large size, that has solar on the roof, with a much bigger surface area, that you could plug into.
Another bad part is that since solar is still in heavy innovation phases, you'd need to be able to swap out panels for replacement and newer tech so there would need to be standards there or else it becomes highly cost prohibitive. It would add so much to testing that it would add layers of cost. This would also limit design options and weight.
Even when efficient, you still want to park your car in or under a cover/garage. That is the best place to put the panels because noone wants a hot car.
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 ?
Say I use my car for the daily commute and I'm some 10 miles away from office. I work 8 hours in the office in daytime, and leave my car in the parking. For when I'm going back home, my battery would be topped up.
I'd need to recharge my car much less, once a month maybe.
Also, say you can do 300 miles with a full charge. Depending on how fast you go, you'll do those 300 miles in 5 to 10 hours. So on average, a the solar aid would give you some additional 15 to 30 miles, ie 5%-10%. Which sounds nice to me.
All with the current technology. Obviously there are tradeoffs, in R&D, price and weight.
But it seems like worth pursing, log-term.
You just gloss over the most important part of the question right there. At a charging rate that low, even a small amount of added weight may completely destroy the plausibility of this idea.
> would only be able to travel 2–4 miles on that amount of electricity… in an hour. Most people could walk faster.
> 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.
Sorry, but that's wrong. They meant 2-4 miles per 1 kWh, not per 200 Wh.
Very good EVs get about 4-4.5 miles / kWh at optimal speed (usually between 25 and 35 mi/hr). So, best case, 200 Wh is good for about 1 mile, assuming you can deliver the 200 Wh over a period of 2 minutes.
However, 200 W can't push the car at 1 mi/hr because of "vampire" losses: Power for accessories and vehicle systems (like power-assisted steering, power-assisted friction brakes, the ABS controller, the airbag monitor, etc). 200 W of power isn't just slower than walking: In a normal-sized car, you will literally go 0 mi/hr.
More importantly, 200 W/m^2 is the best-case scenario at noon, in the tropics, on a cloudless day, with no shadows, using expensive, high-efficiency panels aimed squarely at the sun. As soon as any of those qualifiers is not met, power drops precipitously.
In particular, the atmosphere absorbs a large amount of light: In space, solar insolation is about 1300 W/m^2. At earth's surface in the tropics, solar insolation is about 1000 W/m^2 at noon. At higher latitudes, or other times of the day, solar insolation is lower.
A good rule of thumb is that (for Europe and North America) the total insolation over a full day is about 5000 Wh/m^2. So, a solar panel on a sun-following mount is limited to about 1000 Wh/m^2/day, again assuming no clouds. For a fixed solar panel, such as on the hood of a car, you'll get about half of that: 500 Wh/m^2/day. Remember, you need 1000 Wh to go 4-5 miles.
That "4-5" implies a lot of accuracy, but I would have thought that the distance you can travel on 1000 Wh would vary by orders of magnitude depending on the speed, terrain and road surface.
However, if you are moving a 1 tonne vehicle up a 5% gradient then you won't do more than 4.5 miles on 1000 Wh, if I've calculated that correctly.
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.
What you gain in additional charge will offset the AC power draw you need to cool down your car after you parked it in the sun for a full day.
A more effective solution would be to have a carport with a solar panel roof (10~15m2) that way you have shade, affordable panels, and an actual charge capacity of about 50km. It doesn't move with the car, but since we are talking about work commute your car will probably be parked at the same location for 5 days/week during peak sun output.
Mind you that the panels used on the Toyota prototype are still very expensive. At current prices they probably don't make economic sense.
Right. Or from a pure economics point of view, put the solar panels literally anywhere else in the world other than on top of the moving vehicle that is sensitive to aerodynamics, weight and structural integrity. Deal with the small transmission losses from the grid. Rely on charging stations at home, work or other businesses. The last part is the only piece that isn't reliable at the moment, but is only getting more so.
Can someone explain this to me a bit? How one manages to not only promote such an obvious flawed idea to implement, but actually inspore others to copy them?
Are there any lesson to learn from that for projects that actually work?
I'd count on even less than that. Industrial solar farms average a capacity factor of around 20-25%, dropping as low as 10%. And that's with farms built for maximizing sunlight. A car is likely to do far worse, especially when you consider imperfect conditions, and how frequently people park indoors. If it's a tossup between protecting my car from the elements, and getting a few miles a day of charge, I'm going to choose the former.
80 miles (128km) a day is a pretty harsh commute I used to do, the vast vast majority are doing significantly less than this.
Among other things this means you can meaningfully charge the Prius's battery from the solar hitting it on a daily basis, even though it would take weeks to fully charge a Tesla.
If this was a planned economy I would agree and vote in the next party meeting to put chargers in every parking lot and power them with transparent PV over the parking spaces.
But since I live in a capitalist country I can't make other people invest tens of thousands of dollars just because it makes more sense than putting solar panels on my car. I mean, in some cases I still can, but there's a significant market for the people that can't effect such a change and have to make due with the less efficient solar powered car.
Garage is just one example where there is no sun.
What if they instead sold it to people who usually park in non-shaded parking spaces? Would that work, do you think?
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.
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.
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?
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.
This is empirically not true: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.357...
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.
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+.
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
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.
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).
You're going to be generating that energy while working out anyway and it has to go somewhere. I think the biggest benefit is being able to direct where that energy dissipates. You can either put those 90 watts into the air as heat through friction, or put it into electricity through some dynamo. The second choice will make it so the place doesn't heat up as quickly.
Do they really tell you how much energy they are harvesting as electricity or do they just tell you how much energy they are dissipating as heat?
Because it is very common for sports equipment to measure/estimate the power applied by the athlete, in watts, all without the slightest trace of harvesting implied.
> Over an 8-hour work shift, an average, healthy, well-fed and motivated manual laborer may sustain an output of around 75 watts of work.
That's before conversion & transmission losses (especially as the converter will need to handle wildly varying inputs)
And even if we ignore these, according to 10.1109/MSPEC.2011.5910449:
> Let’s assume that the average piece of exercise equipment is in use 5 hours a day, 365 days a year. If each patron generates 100 watts while using it, that machine creates some 183 kilowatt-hours of electricity a year. Commercial power costs about 10 cents per kilowatt-hour on average in the United States, so the electricity produced in a year from one machine is worth about US $18 dollars.
Same for these solar panels on a car, too. Solar panels aren't the nicest things to manufacture right now. Putting them on a platform this poor is silly when you could put them somewhere more effective. If they were dirt cheap and harmless to create, opportunity costs might be less of an issue, but even today, they aren't dirt cheap and the aren't harmless to manufacture. They should be used effectively, not for show or feelings.
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.
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.
I worked it out and even if I pedal 8 hours / day and somehow convince the wife to join we're only producing 2kWh / day. Our house's power usage is ~11 kWh/day in the winter (worse in summer due to AC)...it's hopeless.
Phones and tablets need 10 watts or less. A notebook somewhere between 25 to 50 watts if it is running at 100% CPU. Why would an exercise machine with a similar screen size need more than that? Even a total beginner can generate far more than 50 watts.
That's... not even wrong?
The "extra energy needs" is 2400kcal, olive oil is 884kcal/100g, that's 270g of olive oil, about 300ml.
That's pounding down half a standard bottle every day, and at least a buck or two. Aside from getting cheap as hell olive oils, you seem to use ladles for spoons.
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.
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.
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.
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.
I missed that the time I went to Alcatraz - but it was probably because it was a night tour...
It's true a car surface is ridiculous. Now on a van, bus or truck .. this could make for some nice juice.
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. But pay attention, and they admit it doesn’t do anything more than power the loudspeaker. The boat runs on diesel. Because of course it does. If a few panels could power a ferry, we'd have gotten off oil long ago!