Is it possible to also involve a geology student? Maybe for the 3 watts to drive the relay station a geo-thermal solution may be applicable.

Clearly a battery based system with a solar panel and/or wind generator for recharging is possible.

I see from the web page for the centre that there is a stream at the bottom of the valley. Is the path of the comm link able to traverse the direction of the stream. You could harness a power source off the water flow in the stream.

Another last thing to consider is the achievable distance with the 802.3 comm link. You should check out this web page for a friend of mine where he has designed and made special antennas that have significantly increased the range of wireless ethernet. The Trevor Marshall Slotted Waveguide Antenna. And his designs are serious engineering efforts and not the amatuer crap done by others with Pringles cans and such.

Michael Karas