Solar Powered Web Server

As you have probably noted from past entries I like to run my own servers.  I’m not running a big enterprise here, so they don’t have to be extremely reliable (though they have been very reliable).  Mostly, I like the control that I have, and the flexibility.

But I find myself running into a few brick walls here.  Mainly, electricity.  Now, it’s relatively cheap, particularly if I run a server at school where I don’t pay for electricity.  But, there’s also the wastefulness factor.  Global climate change or not, I’m not a fan of the idea of wasting energy.  Or at least grid produced energy that could result in carbon emissions.

Alright, if I really wanted to reduce my footprint I suppose I could walk a lot more instead of drive, maybe get a more efficient car, you get the idea.  But there are a lot of servers running out there, and someday it would be nice to be able to keep them all going with an alternative source of power.  Or maybe keep them going out in a remote location, or during a prolonged blackout.

Hence, my idea for a solar powered Web server project.  I have some of the parts for this project already, so but I’d still need to make a few more purchases.  The big thing is design, and here are my thoughts: If I can get some kind of embedded, single-board computer that draws say 3 watts at most and runs 24/7, that is 72 watt-hours per day.  (Just in case anyone is unsure, to get watt-hours you multiply watts by hours.  So 3 watts for 24 hours is 72 watt-hours.)  I will bump that figure up to say 90 watt-hours a day, just to compensate for losses in the battery.  After all, we do want to be able to serve Web pages at night, right?  So 90 watt-hours per day is not too bad.  Supposing that, in sunny Buffalo, NY we get an average of 3.5 sun hours per day, you would need about 25 watts of solar.

My solar arsenal right now consists of one 32 watt panel mounted on the side of my house, plus another 32 watt I have not yet installed, as well as a 21 watt flexible panel and a couple smaller ones.  (There’s also a big 100 watt panel in the garage, but that’s a different story for another day.)  So I have more than enough to make this work in terms of producing power; in theory one 32 watt panel should be enough, but having a second one in case of shade or low light from clouds would be good.

Now, we want some battery backup as well, as I mentioned before.  To do this we probably want to be able to run the server for say two days without sun.  (This isn’t mission critical.)  So, 90 watt-hours at 12 volts is 7 amp hours (90/12), so for two days that’s 14 amp hours.  Not too unreasonable; I have a 18 amp hour gel cell battery that should be able to handle that, without drawing it all the way down (which is bad for the battery).  Although I may consider getting a bigger battery.

Now, this will be a simple server, probably not something I’d install the standard LAMP stack on.  My main thought for this would be that it would also log data from the system via shunts and some analog-to-digital converters, and then present the data in a nice looking Web page.  Maybe if I felt like it some day I could even add some AJAX stuff to it, but whatever.

So this would really be proof of concept.  It would also be great for backup power; if there was a bad power failure I could of course turn the server off and use the power for other things, like charging cell phones and running lights and a ham radio.  So it would be a good thing to have.  I will soon be looking around for a nice single board computer to use as the server, and then maybe a better battery and solar panel location.  With a little luck I will be able to pull something together.  Stay tuned.