Steve has started the preparation of his new Adventure: The Solar UMPC. Well, I can't see you Steve preparing this adventure and not trying to help you.
Here is what I would get if I was the one thinking about living in a Camping Tent.
1- I would get a Portable Backup Power Source like this one from Xantrex. This 600 Watt Power Source is capable of lighting a 50W lamp for around 2.5 to 3 hours. But here is the trick that will help you a lot.
2- I would buy to keep the Portable Backup Power Source charged this two items: A Solar Battery Charger and a Charger Controller.
The idea behind these 3 devices is to have power enough to power the UMPC and a few other things, the solar panel will take of charging the battery from the Portable Power Source while you are using it. I think that it the Powersource by itself was able to power a 50W lamp for around 3 hours having the Solar Panel connected all time could increase the number of hours at least 2 times. What do you think Steve?