solar on the car roof
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It's a 330 volt battery, so you'd need enough 12 or 24 volt panels to string together in series to provide about 350 volts - It would probably be a tight squeeze to fit them on the roof of your garage, let alone on the roof of the car
Don
Don
NeilBlanchard
Well-known member
Right -- there are a couple of solar cars; but they are far more efficient than the i MiEV. There is one that is driving around the world right now on it's own power, called the SolarWorld GT built at Bochum University. The panels are very high efficiency (read: very expensive) and they provide a little over 800w, it weighs very little (under 1,000 pounds I think?) and the car has a Cd of just 0.14. It does seat two people, but with no creature comforts, and it can drive along at 30-60mph pretty much all day when the sun is out.
I think that more typical solar panels that you or I could get might power a couple of fans to help cool the inside of the car on a sunny day. To charge the car appreciably, it would take at least 2kW of panels, or so? That is about 8 or 10 panels that are ~3' x ~5 ' each.
I think that more typical solar panels that you or I could get might power a couple of fans to help cool the inside of the car on a sunny day. To charge the car appreciably, it would take at least 2kW of panels, or so? That is about 8 or 10 panels that are ~3' x ~5 ' each.
A DC-DC converter could step up the voltage from a smaller array of panels to charge the car via the CHAdeMO plug, but I imagine that such a circuit would be expensive to design. It would also be possible to charge a storage battery and then use that to charge the car via the inverter. There would be some conversion losses and an intermediate storage battery might also be necessary, but that would be easier than trying a direct charge of the battery.
Running the 12v systems of the car with a solar panel sounds more reasonable than trying to recharge the traction battery.
Running the 12v systems of the car with a solar panel sounds more reasonable than trying to recharge the traction battery.
Our car goes about 4 miles on a kilowatt hour of electricity - A little less if you park it in the sun and must run the A/C to remove the added heat from the car. It's *possible* to do all sorts of things, but the cost/benefit ratio makes many of them impractical
The Fisker Karma comes with a $5,000 solar roof and it can generate about half a kilowatt hour during an optimal day parked in the sun. This translates to about 4 to 5 miles of extra range per week (for that car) assuming it's parked in full sun for a week. In actuality though, instead of charging the battery pack with that power, much of it is used by a ventilation system which removes excess heat from inside the car. "Featuring the largest solar glass roof ever designed for a production vehicle, the Fisker Karma harnesses energy from the sun to extend the driving range for up to an additional 200 miles/322 km annually. Custom designed to be a wonder of both art and engineering, the roof visually conveys the Karma’s advanced technology and environmental purpose."
Some things are (evidently) a lot more practical on paper than they are in actuality. If you actually got ALL of that theoretical 200 miles per year (the sun isn't going to shine everyday) and you added it up over 20 years, that 4,000 miles worth of electicity would be worth less than $250 - Not a great return from your $5,000 roof
When you do the math on the range you could expect to gain from parking in the sun with whatever solar panels would fit on the tiny roof of our iMiEV, I think it would turn out that you would actually get more of a range gain if you parked it in the shade, since your A/C system is going to have to cool down the inside of the very hot car once you get in and start driving. It would probably be more cost effective to use 15 or 20 solar panels to make a carport roof, park the car under it and recharge while the car sits in the shade below. You could then use 5X or 6X as many panels as would actually fit on the roof of the car and then you'd begin to see some actual range gains . . . . and you wouldn't need to use the A/C as much
Don
The Fisker Karma comes with a $5,000 solar roof and it can generate about half a kilowatt hour during an optimal day parked in the sun. This translates to about 4 to 5 miles of extra range per week (for that car) assuming it's parked in full sun for a week. In actuality though, instead of charging the battery pack with that power, much of it is used by a ventilation system which removes excess heat from inside the car. "Featuring the largest solar glass roof ever designed for a production vehicle, the Fisker Karma harnesses energy from the sun to extend the driving range for up to an additional 200 miles/322 km annually. Custom designed to be a wonder of both art and engineering, the roof visually conveys the Karma’s advanced technology and environmental purpose."
Some things are (evidently) a lot more practical on paper than they are in actuality. If you actually got ALL of that theoretical 200 miles per year (the sun isn't going to shine everyday) and you added it up over 20 years, that 4,000 miles worth of electicity would be worth less than $250 - Not a great return from your $5,000 roof
When you do the math on the range you could expect to gain from parking in the sun with whatever solar panels would fit on the tiny roof of our iMiEV, I think it would turn out that you would actually get more of a range gain if you parked it in the shade, since your A/C system is going to have to cool down the inside of the very hot car once you get in and start driving. It would probably be more cost effective to use 15 or 20 solar panels to make a carport roof, park the car under it and recharge while the car sits in the shade below. You could then use 5X or 6X as many panels as would actually fit on the roof of the car and then you'd begin to see some actual range gains . . . . and you wouldn't need to use the A/C as much
Don
PV1
Well-known member
While cost effectiveness is important, I think what Moneythat is getting at is putting solar on the roof of the car to charge it while you're out and about. I had the same idea because most of the time, you can't find shade to park in. This would be helpful to extend your range if you can't find a plug. Have a few panels on the roof (with some aero work) charge a small LiFePO4 battery bank, and then using an inverter and charge the car with the level 1 cord. This would require more technical work and I think I touched on this before. I was thinking of doing this if I got an I and the apprenticeship I applied for. The parking lot has no shade and no plugs and round-trip range would push the car to its limits. Using this setup would allow the I to charge from the added battery and solar panels while it's sitting. While you're driving around, the solar is charging the added battery. This way, you plug your car in when you park, even if there is no plug available because the plug is in the trunk. The best part is the car is totally autonomous and emissions free, including the power generation. It's a great idea, but is it worth it? Depends, but the extra battery capacity would be nice at times, with a little solar coming in to charge this battery. I'll follow up with the math. Let me know of any circumstances where you would find a solar roof helpful.
Yes, PV1, please do that and share your results. Thanks.PV1 said:
It's a neat idea . . . . I really wish it was more practical
Not really trying to pop anyone's balloon, but if a roof larger than ours (the Fisker Karma) with a very high tech solar system can only manage 1/2 Kwh per day, then I really doubt there's much hope for bolting a few panels on the tiny roof of our car and getting any meaningful range extension. If you could match their 1/2 Kwh, that would only get you 2 or 3 extra miles at best and less than that if you were driving down tree-lined streets, or if it was cloudy or raining. I could well imagine that the 'harm' done to the aerodynamics could easily cost you what little you gained
True, you could carry around more batteries - In effect, the Leaf does this and the extra weight costs them a good bit of the range gained by having more Kwh's aboard . . . . their MPGe is lower than ours
If someone donates the parts you need for your experiment, I hope you go ahead with it and see what you can do, but if you have to spend several hundred dollars trying this, I suspect you'll eventually wind up feeling like you could have made better use of your money
If I needed extra range because my work was a bit farther away than the iMiEV's practical range, I would make some sort of arrangement whereby I could charge it somewhere while I was at work - Maybe make a deal with someone who lived nearby so I could park and charge at their place and walk the last block or two to work . . . . I can imagine all sorts of more practical scenarios than trying to add solar panels to the roof of my car. I have plenty of experience with them - I had two 120 watt 12 volt panels on my sailboat for 6 or 8 years which nearly kept up with my DC refrigeration system, so I'm well aware of what they can do . . . . and I'm also pretty familiar with how much 'real world' energy you can expect to gain. If you actually get 60% of the theoretical maximum from panels mounted on a movable vehicle which are not correctly aimed at the sun, you're doing very, very well and panels fixed to the roof of your car will seldom be positioned for maximum gain. I know it sounds like a good idea, but . . . . .
Don
Not really trying to pop anyone's balloon, but if a roof larger than ours (the Fisker Karma) with a very high tech solar system can only manage 1/2 Kwh per day, then I really doubt there's much hope for bolting a few panels on the tiny roof of our car and getting any meaningful range extension. If you could match their 1/2 Kwh, that would only get you 2 or 3 extra miles at best and less than that if you were driving down tree-lined streets, or if it was cloudy or raining. I could well imagine that the 'harm' done to the aerodynamics could easily cost you what little you gained
True, you could carry around more batteries - In effect, the Leaf does this and the extra weight costs them a good bit of the range gained by having more Kwh's aboard . . . . their MPGe is lower than ours
If someone donates the parts you need for your experiment, I hope you go ahead with it and see what you can do, but if you have to spend several hundred dollars trying this, I suspect you'll eventually wind up feeling like you could have made better use of your money
If I needed extra range because my work was a bit farther away than the iMiEV's practical range, I would make some sort of arrangement whereby I could charge it somewhere while I was at work - Maybe make a deal with someone who lived nearby so I could park and charge at their place and walk the last block or two to work . . . . I can imagine all sorts of more practical scenarios than trying to add solar panels to the roof of my car. I have plenty of experience with them - I had two 120 watt 12 volt panels on my sailboat for 6 or 8 years which nearly kept up with my DC refrigeration system, so I'm well aware of what they can do . . . . and I'm also pretty familiar with how much 'real world' energy you can expect to gain. If you actually get 60% of the theoretical maximum from panels mounted on a movable vehicle which are not correctly aimed at the sun, you're doing very, very well and panels fixed to the roof of your car will seldom be positioned for maximum gain. I know it sounds like a good idea, but . . . . .
Don
moneythat, leec, and PV1 - 
just for fun, a few years ago for an Earth Day demonstration I did something akin to what you're suggesting as I had four 130W solar panels lying around and I used six small battery chargers instead of the large onboard one. I've dug up a photo and old crude block diagram of the setup (the cardboard was covering the inverter and battery bank as it was a very hot day). I was only running a 72V system in the Sparrow at the time, and this setup actually topped-up that Sparrow's 4kWh battery pack that afternoon (wife hauled up the panels, batteries, etc. in her station wagon).
Hint: "do the math first" (and, while you're at it, a cost analysis) :roll:
just for fun, a few years ago for an Earth Day demonstration I did something akin to what you're suggesting as I had four 130W solar panels lying around and I used six small battery chargers instead of the large onboard one. I've dug up a photo and old crude block diagram of the setup (the cardboard was covering the inverter and battery bank as it was a very hot day). I was only running a 72V system in the Sparrow at the time, and this setup actually topped-up that Sparrow's 4kWh battery pack that afternoon (wife hauled up the panels, batteries, etc. in her station wagon).Hint: "do the math first"
(and, while you're at it, a cost analysis) :roll:
MLucas
Well-known member
Off topic, but...what a neat car! I love that paint job. What is that like to drive and do you still have it?
PV1
Well-known member
The batteries I found are 160 Ah LiFePO4 cells, and you would need 16 cells at $207.92 each. A 240 watt solar panel is $500, and the inverter is $500. This setup would give you 8,192 Wh of extra electricity, plus .5-1 kWh from the panel, totaling 8,592-9,192 Wh of extra electricity, giving you slightly more battery capacity than a LEAF. Although, this extra storage cannot be accessed by the car while in motion. The power can only be transferred to the car through the inverter, through the level 1 EVSE, and then to the onboard charger while you are parked. So, the question is, at the same price as a LEAF SV, would you attempt it? I probably would, because the i is easier to manage in heavy traffic because visibility is better. My circumstances at the moment is I drive 40 miles to work, 30 of it on the highway at 60-65 mph, sit for 10 hours in an unshaded parking lot, and drive home. There are no plugs that I can find, so having this setup would help, while also making a statement. Of course, you'd also need a wall charger for the second battery pack if you plan to use it everyday, like I would, so you can recharge the second pack overnight. You could also manage a window fan or something to keep your car cooler while parked, powered by the solar panel. And if anybody doesn't know, the LEAF SL does have a solar panel on it, but it is a little 5 watt panel on the back by the top brake light meant to maintain the 12 volt aux. battery, adding no range to the LEAF. Wasn't meant to.
So, doable? Yes. Practical? Most likely, unless you don't need the range extension or have a plug handy to charge from. Affordable? About the price difference between the LEAF and i. The LEAF and the i have about the same economy on the highway, with the i having the city advantage, so you'd probably get better range than the LEAF, given that you have enough time to deplete the secondary pack.
So, doable? Yes. Practical? Most likely, unless you don't need the range extension or have a plug handy to charge from. Affordable? About the price difference between the LEAF and i. The LEAF and the i have about the same economy on the highway, with the i having the city advantage, so you'd probably get better range than the LEAF, given that you have enough time to deplete the secondary pack.
PV1
Well-known member
What is the difference in range with an extra 200 lbs? (Tried to make that sound sincere) As for the solar panel, the frame could be modified to let the panel sit as low as possible, with skirting around it to smooth out airflow. But you're obviously paying an aerodynamic price. But in some people's situation, like mine, you can sacrifice a few miles one way for an extra 18-25 miles for the other way.
Instead of putting a solar panel on top of the car, how about making a windshield shade from Solarrolls? But this kind of strays away from the idea given the price and inefficiency of flexible solar panels.
Instead of putting a solar panel on top of the car, how about making a windshield shade from Solarrolls? But this kind of strays away from the idea given the price and inefficiency of flexible solar panels.
You're talking about spending $4500, giving up cargo space, adding weight, complexity and taking an aerodynamic hit for another 25 miles of range which can only be accessed if you leave the car parked for 10 hours, plus you're adding in the inefficiencies of recharging one battery pack from another battery pack via an inverter - Your definition of 'practical' is maybe just a little different from what might be considered the accepted norm
Have you checked with your employer to see if there might be any possible way to make some sort of charging arrangement there where you park? Can you park closer to the building so that a cord could be run to the car? Rather than go to all the trouble and expense of modifying the car, I would investigate to see if you could add a charging station at work somehow, assuming you cannot run a cord to the car - Maybe even going so far as to have a new power pole with a meter installed where you park. You're going to need it for the foreseeable future, aren't you?
Are there any other businesses or houses in the vicinity of the parking lot where you work? If you can't charge at work, then I would canvass the neighborhood to see if I could make arrangements with another business, or maybe park it at a private residence nearby where you could pay them to allow you to recharge while you're working. That $4500 could pay for at work charging for more than ten years - It might even be at no extra cost, considering you're going to have to recharge those LiFePo's at home anyway
Granted, you could make your ideas work, I'll give you that - Given enough money and ingenuity, you can make most anything work, but 'practical?' - I'd have to argue that a bit. I would certainly look for every other simpler solution to your problem before I spent the money trying this one
Don
Have you checked with your employer to see if there might be any possible way to make some sort of charging arrangement there where you park? Can you park closer to the building so that a cord could be run to the car? Rather than go to all the trouble and expense of modifying the car, I would investigate to see if you could add a charging station at work somehow, assuming you cannot run a cord to the car - Maybe even going so far as to have a new power pole with a meter installed where you park. You're going to need it for the foreseeable future, aren't you?
Are there any other businesses or houses in the vicinity of the parking lot where you work? If you can't charge at work, then I would canvass the neighborhood to see if I could make arrangements with another business, or maybe park it at a private residence nearby where you could pay them to allow you to recharge while you're working. That $4500 could pay for at work charging for more than ten years - It might even be at no extra cost, considering you're going to have to recharge those LiFePo's at home anyway
Granted, you could make your ideas work, I'll give you that - Given enough money and ingenuity, you can make most anything work, but 'practical?' - I'd have to argue that a bit. I would certainly look for every other simpler solution to your problem before I spent the money trying this one
Don
PV1 - I'm confused, as perhaps I missed your posting that you've actually bought your iMiE and are driving it. :?:
If you continue doing the math, you need to derate all your components: battery usable capacity, inverter and charger efficiencies, etc. And don't forget to add a very sophisticated and expensive BMS for those Lithiums, not to mention the packaging to keep the cells tightly compressed, and a decent cooling system for the inverter and battery pack. Total weight and locating and moving that weight around is another issue.
In any case, you're talking about converting our relatively light and nimble lovely little car into a top-heavy much less desirable vehicle, all at the possible gain of a few puny miles.
I fully agree agree with Don's comments. Since my Sparrow has a usable range of less than 25 miles (even though I could go 50 mile on a bet), i quickly learned where the power outlets are at the local stores, dentist's offices, schools, med center, etc. They're there, just need to look for them and be civil in either asking permission to use them (always explain the tiny $ consumed and offer to pay), or begging forgiveness... you need to have been in the Jazzercise class when a cop walks in demanding to know who owns that electric vehicle and asserts that electricity is being stolen from the city… while they're unnecessarily burning 12kW in incandescent overhead lighting in a room full of windows, but that's another story.
Off Topic: MLucas, the vehicle is a Corbin Sparrow - my biggest surprise was how stable it is at very high speeds.
If you continue doing the math, you need to derate all your components: battery usable capacity, inverter and charger efficiencies, etc. And don't forget to add a very sophisticated and expensive BMS for those Lithiums, not to mention the packaging to keep the cells tightly compressed, and a decent cooling system for the inverter and battery pack. Total weight and locating and moving that weight around is another issue.
In any case, you're talking about converting our relatively light and nimble lovely little car into a top-heavy much less desirable vehicle, all at the possible gain of a few puny miles.
I fully agree agree with Don's comments. Since my Sparrow has a usable range of less than 25 miles (even though I could go 50 mile on a bet), i quickly learned where the power outlets are at the local stores, dentist's offices, schools, med center, etc. They're there, just need to look for them and be civil in either asking permission to use them (always explain the tiny $ consumed and offer to pay), or begging forgiveness... you need to have been in the Jazzercise class when a cop walks in demanding to know who owns that electric vehicle and asserts that electricity is being stolen from the city… while they're unnecessarily burning 12kW in incandescent overhead lighting in a room full of windows, but that's another story.
Off Topic: MLucas, the vehicle is a Corbin Sparrow - my biggest surprise was how stable it is at very high speeds.
PV1
Well-known member
No, I don't have an i yet. Actually, discharging the second pack would take 8 hours, enough to give you 7.5 kWh, which at 3.5 mi/kWh, adds 26 miles of range. A round trip to work for me is 80 miles, which pushes the LEAF's range. So, say an i gives you 55 miles range on the highway, I use up 40 miles, leaving 15 miles, plus 26, gives me 41 miles. That's judging all 80 miles are on the highway, but only 60 are on the highway, plus about a mile crawling to get to the highway. So that leaves me with about 6 miles extra.
So it's not "practical" in a sense, but for no way to get a plug, it's not bad. It was asked if it could be done, and I provided an answer.
This setup is meant to take advantage of the sun beating on a parked car that is going to be sitting there for 10 hours, charging or not. This is the easiest way to use solar to charge the car when the infrastructure is unavailable. Another way to go is to hack the CHAdeMO port and charge the battery directly, but that opens up a whole other set of issues.
So it's not "practical" in a sense, but for no way to get a plug, it's not bad. It was asked if it could be done, and I provided an answer.
This setup is meant to take advantage of the sun beating on a parked car that is going to be sitting there for 10 hours, charging or not. This is the easiest way to use solar to charge the car when the infrastructure is unavailable. Another way to go is to hack the CHAdeMO port and charge the battery directly, but that opens up a whole other set of issues.
OK, so given the constraint that it's impossible to charge either at work or somewhere closeby , would you be allowed to build your own solar-powered charging station carport onsite and leave it there?
, would you be allowed to build your own solar-powered charging station carport onsite and leave it there?That would work . . . . at least until it rains all day one day and he's forced to walk home
I'm trying hard to 'picture' where he works and that there is no possible way to recharge conventionally within a block or two . . . . must be a pretty remote place
We have several 'solar worshippers' here (Joe and myself for two) who would like to do everything solar powered - Joe actually does, recharging at home using solar power. We'd all LOVE to drive 100% solar powered, recharging whenever and wherever we liked using only the sun . . . . and you could actually do that most of the time even at work, utilizing a 'solar carport' as Joe suggested, but you'd still need a plug as backup for not so sunny days. The impracticiality (there's that word again) of doing something meaningful with a solar panel actually mounted on the car would make most of us (no matter how much we love solar power) think twice about doing it
If you actually buy an iMiEV and decide to try any of this, please document your experiments and take plenty of pictures - I'm sure we'll all learn a lot from your efforts
Don
I'm trying hard to 'picture' where he works and that there is no possible way to recharge conventionally within a block or two . . . . must be a pretty remote place
We have several 'solar worshippers' here (Joe and myself for two) who would like to do everything solar powered - Joe actually does, recharging at home using solar power. We'd all LOVE to drive 100% solar powered, recharging whenever and wherever we liked using only the sun . . . . and you could actually do that most of the time even at work, utilizing a 'solar carport' as Joe suggested, but you'd still need a plug as backup for not so sunny days. The impracticiality (there's that word again) of doing something meaningful with a solar panel actually mounted on the car would make most of us (no matter how much we love solar power) think twice about doing it
If you actually buy an iMiEV and decide to try any of this, please document your experiments and take plenty of pictures - I'm sure we'll all learn a lot from your efforts
Don
jennrod12
Well-known member
Ya know, "a block or two" sounds pretty cool in your head, but you'd be surprised at actual distances involved. I work in Silicon Valley in a fairly dense area. I'm in a 1-mile long strip of individual buildings none of which have ANY outdoor outlets. Across the street is a freeway. I'd literally have to walk at least a mile to find any kind of charging, and since I'm surrounded by like buildings, I think it might be 2-3 miles before I found anything.
My company leases the building from a landlord, as with all the surrounding buildings. My company doesn't have the say in putting in outdoor outlets. There is a company about a mile away that is thinking of putting in charging stations (they own their own site), but I am sure they will be for THEIR employees, and even if they are not, those stations would quickly fill up. And I'd still be adding 15-20 minutes on each side of my commute walking to/from the car.
Just saying that you don't have to be in a remote place to not have access to charging.
Jenn
My company leases the building from a landlord, as with all the surrounding buildings. My company doesn't have the say in putting in outdoor outlets. There is a company about a mile away that is thinking of putting in charging stations (they own their own site), but I am sure they will be for THEIR employees, and even if they are not, those stations would quickly fill up. And I'd still be adding 15-20 minutes on each side of my commute walking to/from the car.
Just saying that you don't have to be in a remote place to not have access to charging.
Jenn
