I really like the idea of bringing this to schools! I agree it would be a really tangible way to expose kids to ideas about energy. It would be cool if they could compare the effort to create a (measured) amount of energy to energy used to power everyday class room activities.
Great idea. I think your inspirations (pop up shops, food trucks) demonstrate a really relevant way to connect with the public. I agree that to make an greater impact the cube should be some how interactive. I wonder if you can incorporate a civic hacking/public space hacking element to your idea. I like the idea of pairing with local artist but perhaps you can take the experience to a deeper level that adds to the meaning of the space where the cube exists. I love this projec as an example: http://snip.ly/vJea#http://nextcity.org/daily/entry/hacking-public-space-designers-parking-day