[mixmax]

The obvious choice would be solar, except for the fact that at this time of year we only get around 6 hours of daylight in Copenhagen. Winter solstice was yesterday.

Wind might work, a windmill for boats might be able to give us the power needed. At least it would extend the battery time. Only problem with that is that they're quite expensive, and we didn't have much of a budget to begin with.

Maybe next year... There were so many things we'd like to have done, but didn't find the time and money for. One of them was an app or a dedicated webpage where you control the lights on the tree. Maybe even some kind of game where you play some game on the tree against other players.

Lots of possibilities, but limited time and money...

[walshemj]

One option if you have suitable waves would be to produce a hinged raft and have the flexing motion of the raft produce electricity via hydraulic motors like some wave power systems.

Is there enough tidal flow to use sub merged turbines and use the flow of the water past the moored raft?

Can you tell I used to work in a Hydrodynamics lab :-)

[mixmax]

interesting idea - and very much in the spirit of the project.

It's a pretty closed off harbour so there aren't really any waves, and there's almost no tide so not much flow past the raft either. Especially since it's moored in a sidechannel. So it probably won't work :-(

Kudos for the idea though.