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.
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.