Solar power source?

Discussion in 'MacBook Pro' started by JDN, Apr 15, 2007.

  1. JDN macrumors 6502a

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    #1
    I know, or at least im 99.9% sure, that there is no such device but i thought it was worth a try.

    I there some kind solar power generator that could power the MBP? Not necessarily charge the battery, but just keep the MBP ticking over.

    I was thinking there might be something that has a socket for the plane power cord but i can't seem to find anything.

    Anyone seen anything? Or know if it's even possible?
     
  2. balamw Moderator

    balamw

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  3. PkennethV macrumors 6502a

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    #3
    Actually, I think I've seen that on Discovery Channel a year or so ago. I don't remember the name though. It was foldable but still really durable (you can step on it and it won't crack). There is hope if finding it...
     
  4. djellison macrumors 68020

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    #4
    At £846 - very cool though it looks - I think I'd just carry a few spare batteries :)

    Doug
     
  5. wongulous macrumors 6502a

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    #5
    Get an array in your home and use that to charge some extra batteries. It'll pay for itself in as little as 8-10 years, depending on your climate. :) Not to mention it'll help your carbon footprint, and possibly even make you money if your local utilities support energy buyback (usually after surveying the setup, they'll buy energy back from you at a premium rate!).
     
  6. JDN thread starter macrumors 6502a

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  7. balamw Moderator

    balamw

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    #7
    It's also about twice the size of your MBP, even if you have a 17" :p. (In terms of a diagonal measurement it's abut 25".)

    At 12W it'll take a while just to charge/top off you battery.

    B
     
  8. pederg macrumors member

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  9. balamw Moderator

    balamw

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    #9
  10. phidauex macrumors member

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    #10
    Solar really isn't practical outside of two major areas:

    1. Remote locations
    2. "Always on" grid-connected systems

    Here is the problem... The energy contained within solar radiation is approximately 1000W/m^2 at the surface of the earth. Of course, weather, altitude, time of day, etc, all affect that. But 1000W/m^2 is a pretty good rule of thumb, and is the value used when a module is 'rated' to a certain wattage.

    Silicon crystal photovoltaic modules are around 15% efficient. Which doesn't sound good, except that the theoretical maximum efficiency for a silicon crystal cell is 30%. There are nearly no power sources that are already at half their theoretical maximum efficiency.

    That means around 150W/m^2 of capturable power. A Macbook Pro needs 85W at full tilt. That means you would need about .6 square meters of module just to fully power the Macbook Pro, at noon, in direct sunlight. That is about a 2' x 3' module. That is a lot to carry around. Module prices are about 3.80$US per watt, wholesale. That means the wholesale cost of an 85W module is almost 350$, BEFORE inverters, control circuitry, etc.

    Now, if you are in a remote location where you just can't get power, then you'd just have to suck it up, and pay for the solar modules. But if your concern is offsetting the power used by your computer, it makes more sense to have solar on your home, and charge from it.

    If you carry a solar module around, and use it a few hours a day, then it will take a very long time for the module to generate as much energy as it took to build. This isn't good, environmentally speaking. It needs to pay itself back, not just in cost, but in energy, to be good for the environment.

    A grid-tied solar system on a home generates power all the time. If it is making more than your house is using, then that power goes out into the grid, and powers your neighbor's homes. The power company credits you for this generated power. In this case, the module is going to pay back its energy cost much faster.

    This is why solar cars haven't ever caught on. They actually aren't a good use of solar. It is better to have solar on the home, and use it to charge electric cars. That way when you park in a parking garage, you aren't wasting valuable solar modules.

    So anyway... I guess what I'm saying is, it will be very expensive to really power a Macbook (even without charging, you still need at least 60W to run the thing), and if your goal is environmentalism, as opposed to continuous running in remote locations (that you are willing to pay a great premium for), you should get a solar system for your home, and then buy a few extra batteries. You'd actually pay less in the long run, and generate more power.

    -Sam
     
  11. phidauex macrumors member

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    #11
    Note about the solar backback. As cool as that is, it generates about 4 watts. Which isn't going to do your macbook any good at all. That is about 12V/330mA at full tilt, which isn't enough enough to charge most cell phones.

    -Sam
     
  12. djellison macrumors 68020

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    #12
    Yeah - the problem is the only product one can charge with the sort of arrays that could be considered portable is also the sort of product that has a battery life of a week or more (i.e. my mobile which I only have to charge twice a month). There's scope for things like MP3 players to take advantage - but arrays are simply not efficient enough, not cheap enough (and thus too expensive and too large) to be usefull in charging something like a laptop.

    Doug
     
  13. Scarlet Fever macrumors 68040

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    #13
    this kind of solar cell may solve all of the problems you posed. and its a Melbourne invention as well :D
     
  14. RedTomato macrumors 68040

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    #14
    Lots of interesting information in this thread.

    I've also thought about solar panels for my laptop. I think the posters who talk about the MBP needing 85 watts (or 12 watts - there seems to be some confusion) at peak power usage are missing the point.

    I see 3 roles for laptop solar panels with current tech, in decreasing order of power need:

    1 - Keeping the laptop running at LOWEST power i.e. darkened screen (hint - use the invert screen / high contrast settings to make it more visible), reduced processor speed, black wallpaper, setting MS Word to white on black background etc.

    How many watts does an iBook take at a minimum? A 12'' PB? An ultralight laptop?

    2 - Extending battery life. If running on lowest settings with a panel extends or even doubles battery life, that would be worth it for some people.

    3 - Trickle charging the battery. If the panel is not enough to maintain or even significantly extend the battery life, can it be used to recharge the battery while the laptop is turned off? A day of charging for 2 hours of battery life would be worth it for some people.

    Do laptop batteries have a minimum voltage / wattage to start the charging process? If this is quite low, then you can trade a small size cheaper solar panel for a longer recharge time.

    - Bonus extra - Is it possible to use some form of hand generated power to run a laptop?

    At various festivals, I've used laptops that ran off stationary cycles connected to inverters connected to car batteries connected to other electronic wizardary - typically 10 mins on the cycle got you 15 to 20 mins on the laptop. Use computer, keep fit :)

    It was a lot of hardware to cart around and set up. Possibly with an ultralight laptop, a hand dynamo might be enough to do some topping up. I have a cheap hand powered torch (£5) where 3 mins of winding gives me about 20 mins of strong light, and also another cheap rubbishy hand powered mobile phone charger (also £5) that recharges my smartphone (only a little bit) after a few minutes of winding.

    Better quality handpowered dynamo tech might actually be up to doing something with a small laptop.

    Comments?
     
  15. balamw Moderator

    balamw

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    #15
    The point is that a 12W - 23W typical portable panel can't keep up with the demand of a typical powered laptop, but they can trickle charge the battery when it is off. Maybe once we get LED backlights and flash HDDs you might be able to do something useful/practical with solar power for personal portable computers, but not today with an MBP.

    What I've often considered is an external solar battery charger that can trickle charge a spare battery/batteries which could be swapped in as needed, but most laptop manufacturers have moved away from being able to charge the battery outside the notebook which is most likely due to safety reasons (exploding batteries and all)...

    That said, a quick calculation shows that the MBP might not be too far off the mark in real life, even though this moght not be the case for other boxes. If it lasts for 3 h on a 60 Wh battery the average power consumption is only 20W, so it's not completely out of the realm of possibility, particularly if the backlight and HDD issues are addressed.

    B
     

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