While it at first sounds simple to say "put solar panels on shelter roofs", the devil is in the details. First, the shelter would need to receive direct sunlight for many hours daily, perhaps difficult to find routinely in the "green tunnel". Second, the roof would need to oriented to best catch the sun during the weeks leading up to and following the summer solstice (I imagine a south-southeast facing planar surface at around 20 degrees off of horizontal would be ideal, depending on latitude, of course). Third, some sort of battery storage would need to be present. Fourth, vandalism, by "hikers" and by locals, not to mention outright theft, would likely render such installations useless in very short order.
Aside from the aesthetic debate, which I am firmly on the side of "no freaking way do I want to see that", it seems the real-world practicalities and the likelihood of successful implementation are zero.
AO