Speak to Murray Pearson from the University of Waikato.
Their network CRC-Net (Connecting Remote Communities) uses a solar powered node on Pirongia mountain/hill/bump (Hamilton).
I believe 50watts will not be enough, you need to be able to go through a dark winter week without losing power.
I know they used a lot of deep cycle batteries and ower powered them with solar panels but as far as I know, it has been up almost permanently.

for more info, go to www.crc.net.nz
After having a look there myself it looks like they have more than just the one solar site in operation. I spent a day with them all last year but due to weather we never got to go to the solar powered site.

I hope this helps....

-John