OK, I know that solar panels are not going to get you very far in an electric car. But I found this article about the Prius. There’s a blank in the dash, and I never knew what it was intended for. It turns out that except in the North American versions, there is a button that allows you to run solely on electric power at speeds below 30 mph, and when there are three or more bars on the battery level indicator (on the MFD). How well this works in Europe, I don’t know; but the article says that performing the modification may result in shorter NiMH battery life, and may ‘irreversibly damage the HV ECU (Hybrid Computer) of your car and require expensive replacement.’
It got me to thinking: Assume that a hybrid vehicle maker includes an EV Mode that is engineered such that it will not shorten battery life, and that their computer can handle it. Assume further, that this option can be retrofitted without negative effects. If you do a lot of city driving, or if you spend a lot of times stuck in stop-and-go traffic on the freeway, this might improve your fuel mileage. Obviously, the engine will be needed to keep the battery charged. Why not go ahead and put a solar charging system on the car? If you live in a sunny place like L.A. or wherever, your car is going to be soaking up sun for eight hours while you’re in the office. Why not make use of it?
Note that I am not talking about ‘solar cars’. I’m talking about hybrid vehicles that have a passive supplemental system. I’m imagining a hybrid car with the solar system, a plug-in option, and an EV mode. Sort of an ‘every little bit helps’ style of thing.
EDIT: And of course, I messed up the title by saying ‘electric cars’ instead of ‘hybrid cars’. :smack:
The Prius has a solar panel roof. It runs a cooling fan to keep the car cooler when sitting in the hot Sun. That should give you an idea of the power available for charging.
You didn’t spend the Extra $2000 for it. I think that’s the replacement cost. Not sure what the option cost is.
When I go camping there are a lot of people with solar cells. They manage to charge a few phones with them and maybe top off a car battery. I’m guessing the Prius one could charge a conventional battery if left on all day.
At this point, the panels just don’t generate enough watts per meter to generate an appreciable amount of power on the roof of a car. An average 1x2 meter solar panel makes 250-300 watts/hr at most, and probably far less on a car roof. The rating on a Leaf is about 30 kWh/100 miles so that means absolute best case you’re looking at getting about a mile per hour of charging. And that’s for a dedicated electric-- I imagine it’ll be even less for a Prius.
I think the biggest thing is that a car roof is an unideal place for mounting solar panels and, if you’re going to shell out the big cash for solar panels that make an appreciable amount of power, you’ll get far better results setting them up in a fixed array at home.
Several hundred watts peak power is nothing to sneeze at. I think if you covered the roof, the trunk, and the hood with panels, it would be better than nothing. 1 mile of driving range per hour could be enough to get you out of a jam in some situations.
Moreover, at a minimum you could use it to help run your A/C or the heating if you want to take a nap in your car some time, or to keep your car’s batteries from depleting if you leave the car parked for a few days somewhere without a plug.
Ambient energy supplementation wouldn’t hurt, except for the initial expense. Maybe some little wind turbines on the front, kinetic thermal or pneumatic generators in the tires, and bicycle pedal generators for passengers, a thermal reuptake endocrine system throughout, and a thousand other little energy generating and recycling systems. Clean energy has thousands of options beyond solar. The initial cost of developing and equipping would probably take the wind out of most cars sails. Solar alone doesn’t have the powah yet for more than something like emergency resupply.
If you put a wind turbine on a car, it adds to the power required to push the car forward. The energy you generate is added to the drag of the car, plus a commission for efficiency losses. You are better off improving the streamlining. You are better off shaving a few more pounds off the weight to reduce inertia and rolling resistance. If you can figure a way to recapture the heat loss as electricity without adding significantly to the mass of the vehicle, good for you! There are plenty of fixed-base applications screaming for a cheap efficient heat-to-electricity system with cheaper and more reliable heat sources.
The laws of thermodynamics mean you can’t easily get ahead, you can’t even break even.
I know you’re talking about best case - but 1 mile per hour of charging, although it doesn’t sound much could be enough for a significant portion of some commuting needs -
My daily commute is somewhere between 17 and 20 km - and we easily get 10 hours of sunshine here a day -
In such a scenario, the “solar charging” would be enough for 50% of my commuting needs…
No, you only get the “best case” power generation around noon. There’s no way you’ll get 10 hours of it in one day. Also, I think that estimate used figures for a fixed solar panel tilted towards the south. A car roof is flat, so you’ll never reach that figure. I doubt you’ll ever get more than 2 miles worth of power during a workday, even on a clear summer day.
Two free miles per day is pretty good. If you could average that well including bad days, you’d have a winner. (700+ free miles a year!)
(Clouds alone don’t necessarily eliminate all solar power, the cells still make some electricity on most days.)
Well, the point I was sort of trying to make earlier is that you get a whole lot more “free miles” by leaving the panels a home in a southward-facing array than you would driving around with them.
The only real advantage to having the panels on the car would be for extending the range. The 1 mile per hour charge rate might be useful in emergencies, but having an emergency backup that only works in absolute perfect conditions isn’t all that useful. Plus the $1k+ you’d be spending on the panels will buy a lot of tows or visits from AAA’s new emergency charge truck, either of which would be faster than waiting around for your car to charge.
Oh, agreed. But for the low-mileage user, the free ones add up. And on longer trips, they’d extend your range a little bit. More as the technology improves.
You could get gains from wind turbines, as long as you’re using the ambient winds (that is, movement of air relative to the ground), rather than the “wind” due to your car’s own motion. But then, while you’re on the road, it would probably be more efficient to use that wind via a sail. If you can already imagine why sails on cars are not usually practical, you can extend that to see why wind turbines on cars are likewise impractical.
I think the advantage in the Prius is not extended miles from the solar panel but the savings in energy used for cooling the interior on a hot day. Probably a much cheaper way of doing it would be to install a windshield washer nozzle for the roof of the car and let a timer spray it during sunny days to absorb the heat. Could make one for $30. If they were really thinking they would build shades into each door like they have for sunroofs to block out the light.
I believe I read it cost $2000 to replace the cells on a Prius. So that’s 33 years to break even. Might be a cheaper option on the car so that would lower the time frame. It might actually save more energy in the form of hp lost to air conditioning since it’s function is to cool the car if it’s sitting out in the sun.
