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Can a car cary enough solar panels / Can solar panels carry enough to charge an electric car?

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  • Can a car cary enough solar panels / Can solar panels carry enough to charge an electric car?

    Okay so this has been bothering my mind lately. I am a lover of electric cars and solar panels. I think of them going together like peanut butter and jelly. I constantly think of charging electric cars with solar panels.

    But more importantly, is it a reality? Is it possible today, let's say you have a 10 kwH solar system and you leave it collecting energy for about 8-9 hours, and this on a typical day, so even though it's 10 kwH I expect to collect around 3 to 4 kwH on a typical cloudy day, and then when you come back home, you charge your electric car until the inverters run out of juice it had been supplied from the sun throughout the day.

    So basically, you let your solar panels collect energy when you're at work and then when you come back home, the inverters charge your car until it runs out of juice.

    Is this practically possible today, or no? Oh and to be region specific, let's say around the Midwestern United States.
    Last edited by Mike90250; 09-19-2016, 04:25 PM. Reason: Re-worded subject for clarity

  • #2
    Only in a grid tie situation. Without batteries to store the electricity for night time use you would have nothing to charge the car. The solar would do nothing.
    NABCEP certified Technical Sales Professional

    [URL="http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design"]http://www.solarpaneltalk.com/showth...Battery-Design[/URL]

    [URL]http://www.calculator.net/voltage-drop-calculator.html[/URL] (Voltage drop Calculator among others)

    [URL="http://www.gaisma.com"]www.gaisma.com[/URL]

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    • #3
      Sure if you have means to store the electricity like batteries. However would be extremely foolish to do so. Batteries are extremely expensive and need constant replacement. Battery cost alone, not anything else included wil end up costing you many times more than buying from the POCO. Essentially you win dup paying 5 to 10 morees for power vs buying it. It also makes you a heavy polluter, and waste a lot of resources that could be saved and used later..
      MSEE, PE

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      • #4
        I JUSt want to charge the car

        Originally posted by Sunking View Post
        Sure if you have means to store the electricity like batteries. However would be extremely foolish to do so. Batteries are extremely expensive and need constant replacement. Battery cost alone, not anything else included wil end up costing you many times more than buying from the POCO. Essentially you win dup paying 5 to 10 morees for power vs buying it. It also makes you a heavy polluter, and waste a lot of resources that could be saved and used later..
        What if I JUST want to charge the car? I don't drive much. I have a SparkEV Chevy; cute little car. Takes about four or five hours to charge plugged in to 240v.

        Every time I ask about plugging the car into the roof of the garage, people want to tell me about storage batteries and The Grid. I just want to charge the car, the same way I used to keep my Diesel semi trucks' starter batteries trickle-charged back in the day with a modest-sized blanket that went over the great big truck battery boxes. The cute little car already has gigantic expensive storage batteries and an inverter (?) and I already have a J1772 cable to go from 240 to the car.

        I feel like the kid in the Emperor's New Clothes story because it seems like such a dumbass question -- why can't I buy a panel for the roof of the garage that I can just plug the car into?

        (we don't use enough electricity to merit investing in PV, with the grid and all that, like fifty bucks a month ; we already have a great solar thermal setup that's been running for 30 years; and I see some factory-seconds panels at a manufacturer not very far from the house here. The electric car, though, that's interesting; you don't need to get a permit and you don't need the tie-in electronics, right?)
        Last edited by Richard808; 10-27-2015, 11:46 PM. Reason: some info about the setup

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        • #5
          Originally posted by Richard808 View Post
          What if I JUST want to charge the car?
          That idea comes up a lot.
          "What if I JUST want to charge my car?"
          "What if I JUST want to run my air conditioner?"
          Unfortunately those are the two biggest users of power out there.
          I feel like the kid in the Emperor's New Clothes story because it seems like such a dumbass question -- why can't I buy a panel for the roof of the garage that I can just plug the car into?
          Because the car's battery pack needs ~400 volts and your panel's voltage will vary with temperature and load. You could design a buck/boost that would convert whatever voltage the solar array is generating into voltage the battery wants (and deals with the many problems of charging a lithium ion battery) but it is MUCH simpler to use a solar array, convert your 250-500 volts DC to 240VAC, then convert the 240VAC to the 400VDC the car wants; all the parts are already there, designed and working. (And if the array is generating too much it doesn't get wasted - and if it's not generating enough the extra power comes from the grid.)
          (we don't use enough electricity to merit investing in PV
          If grid tied solar won't be economical for you, then a direct to battery system certainly won't be.
          The electric car, though, that's interesting; you don't need to get a permit and you don't need the tie-in electronics, right?)
          You need custom electronics instead and months (if not years) of design and testing - plus which if you damage your battery it will be a very expensive lesson. Permit fees are the cheapest part of any solar power system; I wouldn't make that a concern.

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          • #6
            Spark EV has an 18 kWh battery. A L2 charge is 3.3 kW, which at 240 V is 13.75 A.

            To get 3.3 kW peak power from an array, you'll need something like 4000 W of solar panels. That is 14 * 285 W panels. At $1 / W for panels, you are already $4000 into this, and you don't even have an inverter yet, or a way to regulate the panel voltage. Have I gone far enough?
            CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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            • #7
              You have experience with a battery maintainer panel, not a battery charging panel. The scale of what you are thinking about goes far beyond that application in terms of cost, area, maintenance, etc.
              It also assumes, of course, that you only want to charge the car for a few hours before and after solar noon.
              As long as you recognize the limitations of what you want to do AND that each kWh of power that you get from solar will likely cost you more than the same power from POCO, then we can keep on exploring.
              But the amount of power that you will need is comparable to what would be produced by a small (maybe 3kW) grid tie system. If you cannot afford grid tie you certainly cannot afford the alternatives.
              SunnyBoy 3000 US, 18 BP Solar 175B panels.

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              • #8
                Thanks for the well engineered response

                Originally posted by sensij View Post
                Spark EV has an 18 kWh battery. A L2 charge is 3.3 kW, which at 240 V is 13.75 A.

                To get 3.3 kW peak power from an array, you'll need something like 4000 W of solar panels. That is 14 * 285 W panels. At $1 / W for panels, you are already $4000 into this, and you don't even have an inverter yet, or a way to regulate the panel voltage. Have I gone far enough?
                I see. So it's possible = 14 panels; it's just expensive = $4000. I'll keep an eye on it; when the panels get a lot cheaper AND/OR more efficient, I'll revisit the topic. (Chevy SparkEV cars can now use DC charging, I believe.) Let me go see how many of those factory seconds there were in that pile; they were cosmetic blems. (The Efficiency thing is more interesting; some young quantum whizkid at Grinnell or someplace like that is gonna come up with a PV cell tomorrow that's right up there with photosynthesis, you wait and see.)

                OTOH I might just do it for the principle of the thing, ie for the fun of it. And thanks for the cogent response; indeed, thanks very much. Much appreciated.

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                • #9
                  It certainly is possible. I know there are a lot of Volt owners who have solar, and even a couple who are off-grid.
                  You need a good sized array to get the power required though.

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                  • #10
                    Originally posted by Richard808 View Post
                    I'll keep an eye on it; when the panels get a lot cheaper AND/OR more efficient, I'll revisit the topic.
                    They're not likely to get much cheaper. They are currently at under $1/watt if you hunt around a little, and a larger and larger percentage of that isn't for the cell, it's for the encapsulant, aluminum frame, glass, junction box, labor etc.
                    (The Efficiency thing is more interesting; some young quantum whizkid at Grinnell or someplace like that is gonna come up with a PV cell tomorrow that's right up there with photosynthesis, you wait and see.)
                    Photosynthesis tops out at around 2% efficiency; modern (good) panels are up around 18%.

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                    • #11
                      Originally posted by jflorey2 View Post
                      They're not likely to get much cheaper. They are currently at under $1/watt if you hunt around a little, and a larger and larger percentage of that isn't for the cell, it's for the encapsulant, aluminum frame, glass, junction box, labor etc.

                      Photosynthesis tops out at around 2% efficiency; modern (good) panels are up around 18%.
                      And the thermodynamic limit using currently practical and available methods, and commonly/currently available materials is a bit better than 30% or so. Some room for improvement over the current max. of ~ 21-22 % or so is possible and likely, but most of the low hanging fruit of increases in efficiency have probably already been picked.

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                      • #12
                        Originally posted by sensij View Post
                        Spark EV has an 18 kWh battery. A L2 charge is 3.3 kW, which at 240 V is 13.75 A.

                        To get 3.3 kW peak power from an array, you'll need something like 4000 W of solar panels. That is 14 * 285 W panels. At $1 / W for panels, you are already $4000 into this, and you don't even have an inverter yet, or a way to regulate the panel voltage. Have I gone far enough?
                        Remember this system still needs batteries to hold the power until you get back at night. Or you need to put these panels at work so you can charge during the day. Or keep them at home if you work at night. Or are a vampire

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                        • #13
                          Originally posted by inetdog View Post
                          You have experience with a battery maintainer panel, not a battery charging panel. The scale of what you are thinking about goes far beyond that application in terms of cost, area, maintenance, etc.
                          It also assumes, of course, that you only want to charge the car for a few hours before and after solar noon.
                          As long as you recognize the limitations of what you want to do AND that each kWh of power that you get from solar will likely cost you more than the same power from POCO, then we can keep on exploring.
                          But the amount of power that you will need is comparable to what would be produced by a small (maybe 3kW) grid tie system. If you cannot afford grid tie you certainly cannot afford the alternatives.
                          LIke Gene Hackman said in The Unforgiven: "Afford's got nothin' to do with it." I pay my bills and nobody deserves more nor less than that from me.

                          The distinction between maintaining and charging gets a little blurry with these cars. They're not the same as gas and Diesel; with your gas rig you run the tank down to near the bottom and then you fuel up; what you find when you get one of these all-electric models is that you go out for a run, and even if it's just around the block, you plug it in and top it off every time you get back to the yard. "Fueling" becomes more of a chore, like a regular task, than a cataclysmic event, some big deal, you drive to a gas station or stop at one on the way; hey, I still remember gas lines in 1973. That took HOURS.

                          I got some good soundly-engineered advice on this very thread that pegs the cost of what I'm thinking of doing at four or five thousand dollars. That's very doable; and there's absolutely no doubt that the next guy who lives in this house is going to be raising kids and the whole nine yards and using a lot of electricity like I used to and that family will make good use of my solar roof supports and who knows, maybe even my solar panels, and will wire it all to the grid and it will all be good. Plan for success. Meantime, I think I'm going to go ahead and plug in just my car to the roof.

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                          • #14
                            Originally posted by jflorey2 View Post
                            Photosynthesis tops out at around 2% efficiency; modern (good) panels are up around 18%.
                            I'm a long way above my paygrade on the biophysics and material science being tossed around in that sentence; but it sounds to me -- and its just my opinion --- that what's going on there is apples and oranges.

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                            • #15
                              Originally posted by Richard808 View Post

                              I got some good soundly-engineered advice on this very thread that pegs the cost of what I'm thinking of doing at four or five thousand dollars.
                              Please don't take my response as "soundly engineered". It is just a starting point. You will be over $10k, approaching $20k by the time you account for everything to make it work.

                              Also, DC charging doesn't help, even if the protocol to initiate it was public and EVSE's existed to do it. DC charge voltage on the spark is 400 V, with solar panels typically producing 25-30 V each, you are looking at maybe 16 panels in series just to get to the required voltage. The DC fast charge power is 50 kW... forget doing that with solar.
                              CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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