This post is really for future Peace Corps Liberia volunteers, although others interested in solar / survival may find this information useful as well
(Update 5/6/14: I’ve mounted my panel on my roof so it plugs into my house! Check it out here!)
A couple months ago in my Bringing Tech to Liberia post, I mentioned that I’ve been using a solar system to charge all my electronics here rather than going to local charge stations. Since that post, I’ve been getting a lot of questions recently from incoming volunteers regarding solar systems, and so I thought I’d finally sit down and write down my thoughts and experience on the matter.
Having a solar system is not necessary to keep your electronics charged at most sites. Charge stations, friends with generators, etc., can usually provide all your power needs. That said, I’ve found that having my own way to charge my devices has been incredibly convenient. I don’t have to worry about bad generators destroying my things, I don’t have to go to a far off area to find someone with a generator, I don’t have to show people the devices I’m charging… The list goes on. Plus, I recently calculated that the money I save by not going to a charge station every other day will pay for my solar system (about $75) by the end of my service. (I’ll show you my solar system in my next post)
The hardest part about owning a solar system in Liberia is not getting it stolen. There’s a couple ways to avoid this:
1) Use a system that has a panel separate from the rest of the system. You can put that panel on your roof or porch, and leave everything else inside. Ideally, you could even chain up the panel. If someone steals the panel, that’s all they get… they wont have your device, or the rest of the solar system (charge controller, battery, etc.)
2) If the whole system must be outside to charge, have it charge a battery instead of your device. (Many systems, like this one, have internal batteries; if you already have one without a battery, you could still get something like this). When the battery in your system finishes charging during the day, you can connect the battery to your device at night and charge it then.
3) A big system is less likely to be stolen, since it draws attention and your community will notice. Attach a larger frame to your system with bolts. While you’re at it, use a chain and lock it to something solid.
4) Never EVER leave any part of your system out during the night. Don’t even think about it, no matter how well you think you’ve installed / locked it to your roof or whatever. Bring everything inside at night, period.
Unfortunately, most people making solar devices these days aren’t concerned with security. Everyone these days wants things that are “compact” and “integrated”. In my mindset now, “compact” means “easy to steal and conceal” and “integrated” means “when you’ve stolen it you’ve got everything“. Ideally, what we actually want is something “tubby” and “modular”. So that study light or radio you’ve got with a solar charger integrated on it? Forget sun charging them, they’ll go missing quick. (Unless you’re lucky enough to get a house with an enclosed porch or something).
On a side note, it makes me laugh now when I see a study light or some other thing with an integrated solar charger being marketed as being a savior for school children in the developing world, because I can’t help but wonder how the kids will charge the thing without it being stolen. They’d have to babysit the thing ALL day to get a measly four hours or so of light in the evening. That’s just not going to happen. If I was that kid and given a study light, I’d sell it as soon as I could and buy some rice to eat instead. And then I’d steal my friend’s light and sell it too. Not that I’m cynical or anything.
A quick word on laptops: Laptops take a lot of power, and so you’d need a pretty big panel (at LEAST a 10W) to really do anything useful. You also need a system that’s capable of getting the right voltage for your laptop. If you’re interested, check out this article on solar charging laptops.
If you’re like me, most of you are just interested in charging phones, tablets, kindles, cameras, and anything else that can be charged over USB. (So that’s the mindset I’ll be writing from here). It’s surprising how many things can be charged over USB these days. Be sure to keep that in mind as you buy things. (When I was packing for Liberia, I actually sent back a camera I bought online because when it arrived I discovered it couldn’t be charged over USB).
Ok, that’s enough introduction, let’s down to business. (and defeat the huns).
When choosing your system, there are four attributes you should consider: panel power, battery capacity, durability, and “steal-ability”:
The bigger your panel, the more power it can pump out. The more power you can pump out, the faster your devices will charge. If your panel is too small, it might take many days in the sun for your device to be fully charged.
Power is measured in Watts. A small panel, maybe the size of your open hand, might measure in around 1.25 watts. A 10 watt panel will be much bigger, about the size of a laptop screen.
Let me try to give these numbers some meaning, without going into any electronics or math. I’m making some gross oversimplifications here, but it should be good enough to get an idea of what to expect.
If you have a tablet (that regularly takes 4 hours to charge), it will take
4 hours with a 10W panel
8 hours with a 5W panel
16 hours with a 2.5W panel
32 hours with a 1.25W panel
For a smartphone (that regularly takes 2 hours to charge), it will take:
2 hours with a 10W panel (but you could charge 2 at once!)
2 hours with a 5W panel
4 hours with a 2.5W panel
8 hours with a 1.25W panel
For a dumb phone (that regularly takes 2 hours to charge), it will take:
2 hours with a 10W panel (but you could charge 4 at once!)
2 hours with a 5W panel (but you could charge 2 at once!)
2 hours with a 2.5W panel
4 hours with a 1.25W panel
Keep in mind these are all gross approximations, theoretical values, assume direct sunlight, etc. I highly recommend getting a system with a panel that’s 2.5W or above. The even higher wattages are especially useful in rainy season, when you might only get a couple hours of sun in a day.
(Voltaic Systems made a nice chart of panel sizes and runtimes for popular tablets. Check it out here. Unfortunately I wasn’t able to find a comparable table like this for phones…) http://www.voltaicsystems.com/solar-tablet-charger.shtml#general1
Many solar systems have a battery. In fact, if there’s no battery in the system, I don’t recommend buying it. By charging this battery during the day, you can then use the power you’ve stored up to charge your devices at night. This way, you don’t have to have your device connected to the solar system while it’s in the sun.
If you have a larger panel, having a battery also means that any leftover energy not going to your device while its charging is saved. If you’ve got a 10W panel, for example, and you’re just charging one dumb phone with it, you’ve got a bunch of energy left over that the panel is producing that goes to waste if there’s no battery in the system.
Many systems will allow you to charge the internal battery even if there is no sun — just plug it into the wall. This can be very handy during rainy season while there’s no sun. (And have a friend with a generator).
The capacity of the internal batteries you find in these solar systems is usually given in milliamp-hours: mAh.
To fully charge a device, you need about:
8000mAh for a tablet
1600mAh for a smart phone
800mAh for a dumb phone
So, if your solar system had a 4000mAh battery that was charged to capacity, that system could then charge your tablet 0.5 times, smart phone 2.5 times, or your dumb phone 8 times*.
*You can only compare battery capacities like this when they’re all running at the same voltage. In this case, we’re looking at USB systems, so everything is at 5V. But if you have a system that uses a 12V battery (like mine), it’s different and takes extra calculations. Message me if you want more info on this.
(And if you’re using a battery from Voltaic Systems, you can look at their battery comparison chart for tablets here. I want’t able to find a chart like this for phones…) http://www.voltaicsystems.com/solar-tablet-charger.shtml#general3
Liberia has harsh conditions. It’s either really wet or really dusty. You need to get something that’ll handle everything. ’nuff said.
As I said before, when you choose your system, consider how you’ll protect it. Things that are “portable” aren’t such a good idea, since they’re usually mounted onto fabric (nix the solar backpack idea). You want something you can bolt down or chain up.
I’ll say it again: a modular system allows you to mount the panel separate from everything else, which is the way you want to go.
And again: don’t get a system without a battery… you don’t want to have to leave your device outside in order to charge it.
That’s all for now; in my next post I’ll look at some actual systems and show you what I recommend.