The Invisible Streetlight, from the 2008 IDSA Awards, is a very beautiful concept. There’s not much info but they do explain that it is solar powered and requires very little material to make because instead of using a support pole, the light has a flexible branch that is wrapped around the branch of a street-side city tree. I would have to assume that it will utilize LED lights with photovoltaic cells on the topside. Looking at the application in the picture I can see how a strong wind could displace it, but they could attach it directly to the trunk for a little more stability.
![Solar, Wind and Bicycle-Powered Christmas Tree in Peru [photos]](http://greenupgrader.com/wp-content/themes/loak_v1_gup/thumb.php?src=http://greenupgrader.com/wp-content/uploads/2009/12/lima-christmas-tree.jpg&h=100&w=100&zc=1&q=90)
Love the idea, but a better power source might be the natural electricity in trees. Scientists found electricity in trees and are working to store the millivolts of energy to produce enough power to run low-power sensors. Perhaps the same concept could act as the sole power source for these invisible streetlights or as a backup power source for a series of cloudy days.
See this story on Huffington Post:
http://www.huffingtonpost.com/2009/09/11/scientists-draw-electrici_n_283244.html