I've been doing a little bit of research lately on new residential wind turbines. There's a lot of new stuff out there, that does not require a thirty foot tower to capture a breeze. No, it may not create enough power to supply a three bedroom home, but may be enough to keep the batteries charged in a small trailer, with very little wind. The neat thing about wind and solar
as a combo is the wind is often strong when the sun is not....
Sam's club has a same/similar unit to the one Chester posted, for far less, that could (possibly) be adapted to portable use. You might also want to look at Missouri Wind's website. Odd looking, but claim to begin power generation at 3.5 miles an hour, at a price under $500.
New vertical and/or helix wind turbines are being developed, and marketed, much more rapidly than a few years ago. Vertical and helix turbines generally are much more expensive, initially, but require less wind, are bi-directional, lower mounting pole, or rooftop install, and, in many cases, are actually quite beautiful. Rather sculptural in appearance, they also present a more "solid mass", causing fewer problems for birds and bats.
Cruising sailboats have employed battery
chargers from windpower for decades. But, the type typically used may or may not be practical for a travel trailer. You'll want to look at something you can adapt to a quick setup/stow for campiing.
The biggest complaints I've encountered in checking references on various systems is actual vs. potential energy production. Second (tie) biggest is maintenance, and manufacturer support. You'll need to go into this with eyes wide open, and skeptical. Small windpower systems are not as common as small solar
systems, by far.
There are a number of websites where you can check (by zipcode) average windspeeds without an expensive wind study, helpful in a residential application, and in deciding if it's worth it to deploy your camping setup.
Just my two cents.
edited for spelling