I like my gadgets and use them a lot on river trips. So far, I've had some success with a few items and not much with others.
IMHO, The Goal Zero Nomad 7 solar charger is a piece of junk so stay away from that. It just doesn't have the capacity to charge normal devices. Their larger capacity units might work better, but the 7w one is worthless. You can get a Anker 21 watt charger for half the price that does a better job. Look on Amazon, I think the Anker 21 is $50.
I had the Goal Zero on a couple of trips last year and half the time, even in full sun, it couldn't charge my phone reliably. I was given a Goal Zero battery power bank, and it couldn't charge that reliably either despite them being designed to work together. I was much more impressed with a cheap 10,000mah power bank I got at Micro Center. Goal Zero just isn't that great a product but has managed to get itself into most outdoor retail stores so its out there a lot. Overpriced and under performing IMHO. For what its worth, someone on my Grand trip last year had the Anker one I talked about above and seemed to have better success.
The other thing about Solar in general is that most of them aren't waterproof. Some say its ok to use in the rain, but if its raining you aren't getting much sun to charge with. Since they aren't really designed to get wet, you'll be taking it in and out of dry storage every time you hit a rapid.
I think this article is a good one for this subject...
Essentially, it details the fact that as of now, buying a couple of high capacity power banks is more economical then any portable power generation source available today. For a 5-7 day trip, a couple of those will do you a ton better even for heavy users like myself. You can get 3-4 charges out of a decent sized (10,000mah or higher) power bank, so grabbing a few of them at around $25-40 a pop is a good way to go. They generally charge about as fast as plugging into the wall at home too, which cannot be said for Solar Chargers.
The economics do start to go away for longer trips. I use my phone for music and taking pictures, a bluetooth battery powered speaker, stuff like GoPro's and waterproof point and shoots, and a tablet for reading and entertainment at camp. I think I'd need a minimum of 6-7 and probably upwards of ten power banks to handle that kind of use. So, I'm not sure what my plan is for this one. I've been thinking about making my own super high capacity power bank out of lithium cells in an Ammo can, but I might go the route of getting a better solar charger too.
I'm rambling on a bit so I'll leave it there. I can go into the DIY battery bank plan a bit more if you guys want, but it involves more lengthy explanation. The way I'm leaning is to get a single battery module(or maybe two) from a Nissan Leaf and adapt it for use as a power bank.