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  • Offgrid project on eBike.

    I just want to present my project and ask a first question to get started on this website.

    Last year I heard about this 7000 km race for solar bicycle
    https://www.thesuntrip.com/presentat...esentation-en/

    I was impress by the quantity of energy this one was getting in a day
    https://www.thesuntrip.com/bilan-ene...-la-libellule/
    Between 1.1 and 3.1 kWh
    My current eBike battery is big at 0.78 kWh

    So now, I want to built one
    but i need help
    I have little knowledge but a great willingness to learn.

    Starting with solar panel, like everybody I need powerful and efficient.
    But for my project, light is also very important
    From what I have learn, I need a mono crystallin panel

    Question 1
    Is that right ?


    Thank you




  • #2
    Originally posted by VeloSolaire View Post
    Starting with solar panel, like everybody I need powerful and efficient.
    But for my project, light is also very important
    From what I have learn, I need a mono crystallin panel
    Well what you are going to need to know is Energy Density or Watts / Kg. Efficiency is secondary. Example Sun Power makes the most efficient panels at roughly 21%. That only makes them the smallest square area, but not the highest Energy Density. A SP X21-335 is 335 watts and weighs 18.6 Kg which gives it an energy density of 335 watts / 18.6 Kg = 18 w/Kg. Now compare that to say a Thin Film Product like SoloPower SP3L is 10 to 12% efficient and a 190 watt panel weighs 5.2 Kg giving it an Energy Density of 190 watts / 5.2 Kg = 36 w/Kg or twice the power. But there is a catch, the Thin Film will be twice as large in area.

    So the answer to your question is NO, mono is the heaviest but most efficient. You cannot have both.

    MSEE, PE

    Comment


    • #3
      Thank you. Now I have to add another criteria, size.

      I found this one,
      https://www.alibaba.com/product-deta...152717072.html
      i don't know what type of panel but for 100 watts, it weight 1.5 kg.
      So around 66 W/Kg
      is there some component missing in this one for being so light ?

      Comment


      • #4
        Originally posted by VeloSolaire View Post
        Thank you. Now I have to add another criteria, size.

        I found this one,
        https://www.alibaba.com/product-deta...152717072.html
        i don't know what type of panel but for 100 watts, it weight 1.5 kg.
        So around 66 W/Kg
        is there some component missing in this one for being so light ?
        Yeah, a frame, glass, and junction box with diodes. Like I said you cannot have your cake and eat it to. Efficient panels (size) is going to be heavy. Light weight panels will less efficient and larger. You cannot have it both ways.

        A 100 watt, 20% efficient, monocrystalline solar panel is roughly 1/2 meter square in area,, expensive and fairly heavy. A 100 watt, 10% efficient Thin Film panel will be around 1 square meter and half the weight of mono.
        Last edited by Sunking; 04-09-2017, 11:06 PM.
        MSEE, PE

        Comment


        • #5
          Originally posted by VeloSolaire View Post
          So now, I want to built one
          but i need help
          I have little knowledge but a great willingness to learn.

          Starting with solar panel, like everybody I need powerful and efficient.
          But for my project, light is also very important
          From what I have learn, I need a mono crystallin panel

          Question 1
          Is that right ?
          Depends on what you want to spend. If you have financial backing you should consider cells like the Alta cells; they are very lightweight, flexible and over 30% efficient. They are also $50 a watt. If not, you will likely use something like the HQST-100 (commercial) panel. Heavier and less efficient, but cheap ($1.50 a watt) and flexible.

          Comment


          • #6
            Originally posted by jflorey2 View Post
            you should consider cells like the Alta cells
            ...
            If not, you will likely use something like the HQST-100
            Thank you
            Wow!!! The Alta could be perfect for another project which need maximum 4 watts
            The HQST-100 seems great for my solar Bike. Different weight are giving in the web page but it should be around 50 wH/Kg
            Dimension are about the same as others I saw. So it is looking good !


            I guess being too flexible might be a problem for efficiency because not all cell would be at same angle ?
            I will put something underneath to keep it flat.


            Comment


            • #7
              Look for semi flexible panels that uses 5" sun power cells and have a semi rigid backing out of plastic . People uses them on boats.

              Comment


              • #8
                Originally posted by VeloSolaire View Post
                Thank you
                Wow!!! The Alta could be perfect for another project which need maximum 4 watts
                Real foolish @ $200. It would take 12,500 days (34 years) to generate $200 worth of power. Something tells me you wil not be alive or care 34 years from now. Panels wil not last that long anyway.
                MSEE, PE

                Comment


                • #9
                  Originally posted by Sunking View Post
                  Real foolish @ $200.
                  My laptop power input is USB-C. On average it use between 1 and 2 watts. On peak it use around 4 watts (mesure with intel power Gadget)
                  it would be nice to go out and not worry about battery and in the worse case scenario, it would just be fun to try.
                  i wrote the company but so far no answer.

                  Comment


                  • #10
                    For $200 you can buy a 50 to 75 watt solar panel, charge controller, and a decent 12 volt 40 AH ah battery.
                    MSEE, PE

                    Comment


                    • #11
                      OK, I found many SunPower C60 flexible solar panel under 4 pounds but some are rated 12 volts and some are rated 18 volts. I guess if one is higher voltage(Tension) it mean the Amp will be lower. I am planing on 4 100 watts panel with Genasun controller that can take 8 A input, so 100 watts/18 volts = 5.5 A , I should be ok. the 100/12V = 8.3 and in the Spec page of the Genasun, it says it will handle 9 A. My question, Is it safe to think that my 100 watts & 18V or 100 & 12V panel will never produce more than 100 Watts and never more than the V spec ?

                      Comment


                      • #12
                        12v would be the nominal rating of the panel. 18v would be the VMP rating of the panel. They are both intended to charge a 12v battery.

                        WWW

                        Comment


                        • #13
                          Surprised nobody has asked this yet, Am I missing something here? Have you figured how much power you will accumulate with this say, 100 watt panel, for example. What exactly is this going to run? An electric motor? You might get enough energy from this 100 watt panel to travel how far, a quarter mile?
                          2.2kw Suntech mono, Classic 200, NEW Trace SW4024

                          Comment


                          • #14
                            Originally posted by littleharbor View Post
                            Surprised nobody has asked this yet, Am I missing something here? Have you figured how much power you will accumulate with this say, 100 watt panel, for example. What exactly is this going to run? An electric motor? You might get enough energy from this 100 watt panel to travel how far, a quarter mile?
                            My guess is that the electric bike battery will (may) just get some additional charging from the solar panel.

                            IMO the extra drag from the panel may easily negate whatever extra charge the battery gets but it is the OP's experiment and they may be on to something that is productive or at least fun.

                            Comment


                            • #15
                              Originally posted by littleharbor View Post
                              Surprised nobody has asked this yet, Am I missing something here? Have you figured how much power you will accumulate with this say, 100 watt panel, for example. What exactly is this going to run? An electric motor? You might get enough energy from this 100 watt panel to travel how far, a quarter mile?
                              Typical human bikers put out about 100 watts and they've ridden across the US. A few years back someone rode across the US with a 240 watt, 10 pound panel and a Specialized E-bike.

                              Comment

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