I have 10 photovoltaic panels (120W) which I use to charge batteries, they obviously don't produce that much power but it does mean I can run the laptop and a few other things off them - I'm looking to convert an old UPS and some of the router (at home) PSU to run off it when I get around to it.
I've also got it hooked up to a small home made monitoring board and a Bluetooth Arduino which sends back voltage, current in/out, temp and light levels (though I've broke the sensor for this) which I then make cacti graphs out of ... it's all about the graphs man

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ChrisB.