PV Gap

Heidi Said:

What exactly does my car solar panel charge?

We Answered:

uh that would be a "yes" to your question. All it does is trickle charge the battery. I take it you leave it on your dash to block out the sun like a normal screen.

Its a good thing to have, but your battery wont last forever. You will still have to swap out a new battery every few years; for example if the battery is a five year battery, get a new one after about four years. Give or take a few months, its better to have a margin of safety, than to be stuck out in the middle of nowhere just because you have a dead battery.

Wanda Said:

How many watts does my solar panel need to be if I am running lights only at night?

We Answered:

Here is the math.

3W/ft * 64 ft = 192W
4hr * 192W = 768Whr <--- energy needed per day

768Whr / 12v = 64Ahr
64Ahr * 200%(d-rate) = 128Ahr <--- Your battery needs to be a minimum 128 Amp - Hour to opperate without damaging itself.

At Boise, Idaho — Latitude: 43.6 we get 5 sun hours per day average
If your latitude is less than that, your sun hours will likely be greater.

768Whr / 5hr = 153.6W ~ 160W panel required.

I highly recommend that you get a charge controller in addition to this panel, as it will protect your batteries and enable charging during low light conditions. Some even come with automatic light timers and or motion sensors:
http://www.aurorapower.net/products/list…

For more information on solar electric components and layout visit: http://www.aurorapower.net/alternative-e…

Hope that helps!

Ruth Said:

What kind of solar panel would be sufficient to run my computer off the grid 24hrs a day?

We Answered:

In round figures, let's say you've got a 500 watt power supply in your computer. That seems pretty average. Now maybe most of the time your computer isn't using all 500 watts, but that's how much your power supply can deliver when it needs to, so we should design a solar system that can accomodate that much as well, so that it's not the weak link in the system.

You need 500 watts over 24 hours, or about 12 kilowatt hours per day. Of course, your solar cell isn't going to work for that part of the day when the sun is down, so you have to be charging a battery + driving the computer while the sun is up. To keep the figures round, let's say you get sun for half the day. Then your solar system has to provide 12 kilowatt hours in only 12 hours. Basically, you are going to need a bare minimum of 1000 watts worth of solar cells.

A sample solar cell (URL below) is 11.5" x 14.75" and provides 11 watts. That would be one watt for every 15 square inches of solar cell. So you need 15000 square inches of solar cell to get your 1000 watts. That would be approximately 10' x 10'.

Of course, the 11 watt rating is probably only what you get under ideal circumstances (like the sun shining directly at the cell, under conditions of no smog and no clouds, etc.). Circumstances are rarely ideal. So you probably want to add a large fudge factor to make up for it. Maybe double the size of your solar cell to 10' x 20'.

Now maybe you live in northern Alaska, for example, where you hardly get any sunlight at all during the winter, but the sun is up all day in the summer. That probably wouldn't change your solar cell much, but you would require a much larger bank of batteries to last throughout the winter.

You can see that there are a lot of factors to weigh. Maybe if you're going to spend a fortune building a solar system, you could shell out a little more for an extremely power-efficient computer.