Idea worth trying? Laptop + Solar panels

[ash.gti]

I don't know exactly how much power the most recent types of solar panels produce, but I was wondering if anyone else feels like it would be a feasible idea of making say a backpack with solar panels on it to charge a laptop?

I have seen things similar to this but the ones I have seen say you should not charge a laptop on them for one reason or another.

I know i'd love to have one if it could keep my laptop charged while in the sun, or charge it slowly while its off, or even prolong the battery life so I could get more than 2-3 hours out of it in the sun.

Personally, i like being able to take my laptop just about anywhere I can find a wireless connect and work outside. It a lot more refreshing than working in an office or a room.

What would be the most difficult part of setting something like this up? Regulating the amount of power a solar panel is producing? Or are there some other details I am not aware of. I only have a basic concept of how most hardware works. I mean I have built my own desktop in the past, and took some EE courses in college for my degree (Software) but I am far from understanding the technical details of setting something like this up.

[b.i.o]

I don't think that currently commercially produced solar panels could be both portable and powerful enough for this to work, unfortunately, but it seems like I'm always hearing about new/better solar panel technologies, so I think it's certainly something that could happen eventually.

[LittleChrist]

And because the sun varies its intensity, solar panels on their own can't put out a steady current needed to charge a laptop. You would need batteries for storage of extra power just in the event a cloud came by. This is where the weight and bulk come in. Sure, it might fit in the backpack, but a 50 lb. backpack that can't carry anything else hardly seems worth it.

[ash.gti]

http://www.voltaicsystems.com/bag_messenger.shtml

Has a few backpacks, and carrying cases that have solar panels on them
Theirs weighs 3.25 lbs (1,500 grams), they even include other adapters.

I guess, i was wondering more, how hard would it be to build one myself?

[tinyterror]

Your best bet for solar power would be to have solar panels charging your laptop battery over time. You would have to have a fairly significant solar installation to provide enough power for your laptop to run off of it directly.

I think the hardest part of this would be building the custom electronics and power converters. That being said, any electrical engineer with a bit of experience might be able to help you out. It all depends on the battery you are trying to charge and how sophisticated you want to make the rig. You might run into problems with overcharging unless you figure out a way to trickle charge or something.

[Little Richie]

I wouldnt count on running it mainly from the sun, my laptops power supply outputs 20V 4500mA an amazingly high amount of energy, atleast from the sun, with the technology in this age.

I like the 'over time charging idea' , build an easy charging station. Almost sounds like a sellable idea.

On a side note "I don't know exactly how much power the most recent types of solar panels produce"
just a nitpic but they convery energy not produce energy. The bottle-neck is the %efficiency, for now we are building them larger to acount for this, but larger is more material, is more $$.

[davean]

Good solar panels can get in the range of just below 30% but you have to also factor in angle, conditions, and latitude. That number is for crystalline cells though, you'd probably want amorphous cells because they can flex and just be woven onto the surface probably. Amorphous cells are much less efficient, the best research results I found quickly where 14.5%.

For the record, my laptop maxes out at 10Watts (its a 12.1" ultraportable). Of course, those of you lugging around a laptop weighting more then 1kg are insane.

Your real problem is that you need some good charging circuits to not blow up the batteries. Charging Li-ion cells isn't simple and it can be dangerous (those things can and will explode when charged improperly). Not having a steady power source apparently complicates this but charging circuits are not my area of expertise.

['; DROP DATABASE;--]

I've thought about this before, didn't look much into it, but I was thinking a solar panel that folds out from the back of screen, something like this: ☀ /|_ -> ☀ ¯|_ (Go crappy ASCII art. ) I have no idea how much power a cell the size of your average laptop screen puts out, though, and it might make the whole thing top-heavy. (The hinges would need to be strong enough to hold it up in position, which seems like it'd add weight.)

[jtniehof]

Ken Kifer's page on bike touring with a solar laptop might be useful, although several years old now.

[davean]

He is using NiCad batteries so most of it doesn't apply.

Notably Nickel based chemistries are a lot easier to charge (even if they don't cycle as well and they don't store as much power), they are also safer. Lots of solar things use them probably for this reason. Your laptop almost definitely does not.

[ian]

I wouldnt count on running it mainly from the sun, my laptops power supply outputs 20V 4500mA an amazingly high amount of energy, atleast from the sun, with the technology in this age.

I like the 'over time charging idea' , build an easy charging station. Almost sounds like a sellable idea.

On a side note "I don't know exactly how much power the most recent types of solar panels produce"
just a nitpic but they convery energy not produce energy. The bottle-neck is the %efficiency, for now we are building them larger to acount for this, but larger is more material, is more $$.

Re: your nitpick, it’s popular useage and perfectly acceptable. Unless you want to nitpick with everyone who has ever used the term ‘energy production’

[phillipsjk]

I use a solar-powered calculator for all my solar-powered computing needs.

I guess I'm suggesting that you should start by finding a computer that uses as little power as possible; yet, still meets your needs.

Unless you are doing a 'round the world bike or back-packing tour, you will probably find it simpler to just carry an extra battery. It is a lot more feasible if you are spending more time in the sun than computing.

[ash.gti]

Unless you are doing a 'round the world bike or back-packing tour, you will probably find it simpler to just carry an extra battery. It is a lot more feasible if you are spending more time in the sun than computing.

Well, when I posted this I was planning on a 7 day hike and was thinking of bringing a laptop for shits and giggles. Ended up just bringing a note pad and writing everything down for later.

Just kinda got me thinking about a solar powered laptop. I found a solar powered bag that can charge a laptop battery but I didn't really want to buy it by that point.

Weren't they trying to come up with a hand crank or something to charge the OOPC with?

[Carnildo]

The OLPC laptop (I've got one) can be charged in a day by four square feet of solar panels, or one to two square feet if you've got a good sun-facing site. Keep in mind that the OLPC laptop draws about a tenth as much power as a typical consumer-oriented laptop.

[Yannie]

It is a worth considering. If you may want to use your laptop to upload your photos, download music and videos or work on it for several hours each day, it is better to use a solar power. Most of computer users look to use solar out of necessity when there is no power available such as while on vacation or working in a remote location.

[ajd007]

Just a back of the envelope calculation here:
Solar constant is 1366 W/m^2, but only 1000W/m^2 reaches the surface after absorption and scattering in the atmosphere (using AM 1.5 spectrum)
Assuming a 15inch laptop (16:10 aspect ratio), this gives an area of .171 m^2
So total solar power reaching laptop is 171W
Assuming a commercial amorphous silicon solar cell (efficiency approx. 10%), only 17.1W is usable power.
This is not nearly enough power to match the 20V, 4500mA (=90W) cited earlier
Backpack solar cells are really only powerful enough to charge ipods, or other small accessories, not laptops
With a single-crystal silicon solar cell, you can do better, but its still not good enough.

Edit: Also wanted to mention that this power output is at peak noon with normal incidence of sunlight. It will only decrease as the angle of the sun increases or as you tilt the solar panel

[mosc]

I get the cool factor but a small portable solar panel that kicks out some power is both going to be cost prohibitive and also quite dirty to make. The power that comes out of it is clean, but at what cost? Carrying around an additional battery, for example, will add a small amount of weight and extend your laptop's usage time two fold. You can charge both batteries when you return home. If that's not enough, you could take yet another battery with you. The power that comes out of the wall is not the cleanest thing imaginable to make, but it's also not the dirtiest. Also, if you're really environmentally conscious, you could charge overnight when dirtier fuel sources are not required. Nuclear and Hydro power makes up a larger percentage of our power when the demand is less.

If you're going to be away from the electric grid for an extended period and want to use an electronic device, you're going to need a larger solar installation with it's own battery. You would then charge whatever off of the solar station's battery. Not the solar panels directly. Photovoltaic cells can have very wide swings in power from a trickle to a deluge from a cloud floating by. You definitely do not want a sensitive electronic device like a laptop hooked up directly to that. I'm sure the weight of said installation would be hundreds of spare laptop batteries

and ajd007, your math fails to account for clouds, pollution, partial tree cover, and a bazillion other things that far and away reduce the energy gathering capability of a solar panel.