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That's good information for the "typical panel which is about 20% efficient when directly facing the sun." I'd be much more interested in what is possible using the current state of the art equipment in good conditions. Can you provide that for us 3 prius mike?

 

Take your pick from this chart:

https://www.nrel.gov/pv/assets/pdfs/best-research-cell-efficiencies.pdf

 

That's not quite what I asked about. Usually, if you denigrate a design it's because the design has specific faults. If Mike knows of the specific faults that make that design flawed, the rest of us can "stand on the shoulders of giants who came before us" if he gives us a quick description of the failure so we can jump off from there.

 

That’s a trip down memory lane. I remember in the early internet days the only reasonable and affordable way to get panels was to buy derelict ARCO panels that were being tore down en masse at the time for salvage.

only a couple websites had cheap volumes of panels that were unbelievably expensive to ship.

 

The best available supposedly was lightyear one, which from their 2022 press release was approximately 5 square meters and had a peak of 1 kw. Note the body shaped panels were likely much more efficient than 20% but following the curves of the body lowered peak production. In ideal conditions they could provide 6kwh/day according to the company. I don't even know how they got that large area. These were very expensive, which led to the canceling production. The company is still in business but trying to sell panels to other auto manufacturers, and perhaps making a less expensive vehicle. I'm sure they are concentrating on lowering production costs, not increasing efficiency right now.

They do have foldable panels, so I suppose you could unfold when parked if your spot was big enough say 6 meters by 5 meters (or around 18'x15'). Still this is an expensive proposition unless you don't move your vehicle much.

In most cases a bigger battery is cheaper, depending on your travel plans.

 

That chart tells you the current 'state of the art' efficiencies of all the PV chemistries currently in use or development. From it, you can compute the minimum size of a proposed towed collection array.

 

I assume you want to cover your car with solar panels.

IMO, just a dumb idea. Put the panels on your roof where you can collect the maximum amount from them everyday for 25 or 30 years, not on a car where they will be shaded lots of the time, at the wrong angle lots of the time and possibly get totalled in a wreck and will certainly not last on a car for 25 or 30 years.
Once all the rooftops, parking lots, etc are covered then we can think about cars and maybe we will have cheaper solar panels with higher efficiency

Mike

 

^^ ++

PV panels mounted on a rooftop have a far higher utilization factor than any mounted on a car: better average pointing direction, less shading from trees or adjacent buildings, never any shading from a garage roof, no continual energy expenditure hauling them around, longer life expectancy, and almost never ceasing production just because the 'battery' they feed (i.e. the grid) is too full to accept any more charge.

Mobile PV for propulsion is not yet a good use of one's resources, when there is still plenty of much lower hanging fruit available.

Someday, mobile PV may make sense. But today, we get a lot more energy return by attaching that PV to a building or other fixed location, using it to charge a plug-in car battery when available, then having it continue harvesting energy to feed into 'the grid' all the rest of the time. A lot more return for the same buck.

 

While it makes sense and all to just put PV panels on the roof of one's house, a lot of us do not own a house and do not have permission to do so.

This is kind of like my ham radio setup. It is in my car, not on the building I live in, because although it would be much better to have it on the roof I cannot get permission from my land lord.

So if solar panels can't be put on my home, then the only option is on the car. Or just not do it, that's perhaps the only logical option.

PS. Seeing people who actually can get some sort of charge off a solar trailer out in the middle of nowhere may not be the most efficient and economic means of electric propulsion, but it is pretty cool IMO.

 

I do NOT want to COVER my car with solar panels, but I can see edge cases where It might be useful to generate enough power get to a charging station (or petrol for PHEV cars). California has the strangest regulations imaginable when it comes to home solar installs. The Net metering tarrifs are so convoluted that they actually punish the home owner based on the presumption that adding rooftop solar panels increases the burden on the grid and raises the prices that poorer people have to pay.

I don't yet have a solar installation at home. It would require an expensive roof rebuild and expensive battery banks that may never pay back in savings.

But for only $600 you can get a solar array added to the roof of a gen 5 Prius Prime at time of purchase. That charging system can provide enough power to handle daily charging to cover the short trips that average drivers make each weeks. That may be quite useful in the future if the Governor's plan to ban gas cars comes to fruition. A PHEV that can't be filled at a gas station is badly crippled.

And that's why I was more interested in what IS possible with car mounted power generation as opposed to what can't be done.

 

Does your state or utility have a "community solar" program? This is a way for renters to get into solar energy.

 

I would say for a car you are better off without any large solar. If you have a camper or van that is sitting idle in the sun for days, then it makes more sense. I know people that use small solar to charge their phones and batteries which also makes sense if you have a big enough battery buffer.

I doubt even california will ban gas stations in the next 20 years, so I would take that worry away. I think its idiotic to ban new gas car sales, but the state does many silly things.

The solar roof on the current prime I believe is 185 watts. If you parked it in great sun and didn't need to use much ac or heat you might get 4 miles of charge a day. Not a big investment and its kind of cool. The main thing it would be good for is to provide enough power to pre heat or cool your vehicle, it can also help keep your 12v battery from dieing early if the car is sitting out. The full solar roof just doesn't make economic sense but these small things can.

 

No, I can't find any info on it for my city. The county, which is a separate electric company, does offer it, although it says all options are already completely leased out.

While a great idea, one of the bragging points of solar is a person making their own energy. When solar comes from someone else's solar panel, its a good thing, but is still just a service you pay for like anything else.

Maybe I should get back into diesel cars and making my own biodiesel instead?

Just kidding. But still. Getting into an EV is tough, and all the great ideas always turn out to be not-so-great.

 

Taking a 185W PV unit, plugging it into NREL's PVWatts calculator to take into account seasonal solar angles and typical local clouds and weather, tilted at 0 degrees, and remove the AC inverter (rather, set DC/AC ratio to unity), leaving all other parameters at their defaults, I find it should collect solar energy worth about 1100 miles/year in Los Angeles, 700 miles/year in Seattle. (At 4 miles per kWh.)

Assuming it is never parked in a shadow.

But the entire month of December is worth only 50 miles in LA, or merely 14 miles in Seattle.

Those winter figures I listed above seem quite crippled to me. Far far less than average drivers.

But like Austin, I'm seeing no hint of banning gasoline sales, just banning sales and registration of new gas-powered cars starting 2035. You will still be able to buy gas for your Model Year 2034 gasser / hybrid / PHEV for the indefinite future. And sell it to someone else who can can still re-register and gas up and drive it.

 

Thanks for all the input folks. The first draft of Newsom's edict did not make provisions for allowing PHEVs on the road.

I was going to throe out some logs from my personal driving records, but the internet seems to be finicky and I can't reach the car via the Toyota app.

Just at an estimate based on a poor memory, I drive the car every other day for 2 to 10 miles. That's trips to the grocery store, the barber, car wash, etc. A quick look at the charging cycles would show that a car with 40 miles of range will do OK if it only needs to replenish the battery from a relatively small drain.

I plug it in to a level 2 charger each time I arrive home. It's charged within 2 hours and ready to go. This would work well with a 185 W panel and associated charge controller mounted to the car.

But twice a month I have to make 1000 mile trips, and that partially depletes the traction battery in the first 45 miles on the freeway. It's what makes it a good choice for my particular uses.

 

Many of these gas car bans allow the sales of new PHEVs to continue after the cutoff date. Some may even allow hybrids.

 

I had missed this PHEV allowance after the cutoff date, but now see it in CA's descriptions. Though don't yet see the minimum PHEV requirement to quality there.

It turns out that my own state's (WA) similar gas car ban also has a PHEV allowance, with a minimum 50 mile all-electric range. For now, I presume that means an EPA-rated 50 miles, so my 42-mile-rated RAV4 Prime isn't yet good enough, despite currently showing an estimated EV range of 56 miles. But it won't take much capacity increase to meet that requirement for model year 2035. I'm already gassing up this one much less frequently than the Prius needed, thanks to being able to do some many trips gas-free.

Zero-emission vehicles (ZEV) - Washington State Department of Ecology
Cars and Light-Trucks are Going Zero - Frequently Asked Questions | California Air Resources Board

Do note that the 185 W figure is a peak power under certain standardized conditions when pointing directly at the sun, not an average or steady power in typical conditions when the sun is off-axis or somewhat attenuated. It will never happen for a car parked on level ground in the Continental U.S., though southern Florida could come very close in summer.

As I posted earlier, don't expect that 185 W panel to produce more than 1100 solar-powered miles per year in the SoCal region, and even that presumes ideal shade-free parking.

 

Sure go ahead and get that even though it will probably not pay for itself...but you'll feel great that you go an extra mile or two or range. You have to park in the sun and unless it is for many hours per day it makes sense to park in the shade to protect the car and minimize the use of A/C when you get into a 125F car. During the winter it is different...but then the sun angle collects far less.

Mike

 

Although PV panels also increase in efficiency in the cold. But yes, even at 44 cents per KWh in Hawaii, it would be pretty hard to have it pay for itself.

This is why I would personally be interested in lugging around something that can deliver a level 2 rate of charge, even if it needs to be pulled on a large trailer, or better yet...

Take up the entire trunk space. Solar cells themselves are quite thin and light and you should be able to stack lots of them in the rear of an EV like a Leaf with the seats folded down.

That, or have a canopy of solar cells over the car up on bars that shades the whole car. It could be made to tilt when parked. Getting at least 1kW should be possible on a solar panel that's just as wide and long as a car. Make it fold into three and you have 3kW, enough to do some charging out in the middle of nowhere, or at home or work (of course taking up 3 parking spaces). And at the same time it will shade the car, great for lowering the need for A/C anywhere you go.

 

Payback around here is about 10 years.
Towing something around would probably never pay off