[saurabhtandon]

This is definitely an interesting project. I liked the video projection and extending battery life to 2 days. Kudos to the team :)

However, could you have a clean power source? I mean there was water, wind and the barge was floating. Is there a way you could have recharged the batteries without the generator? I know the power requirements was high but just wondering. Small wind turbines may be (assuming cost was not an issue)?

[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.

[cnvogel]

Given the total effort spent, I think adding a canister of fuel every two days is absolutely reasonable.

The additional complexity of solar or a few turbines would have caused that project to probably consume much more resources than (just guessing) one large car tank filling over the whole runtime.

Also: the generator probably is way overpowered to just charge the battery, must small ones have 1-2kW or so. Its consumption likely is dominated by whatever it needs during idling. So, a way to probably cut consumption in half would have been to just use two times the number of batteries and charge half as often.

Update: Based on http://powerequipment.honda.com/generators/models/eu2000i (first random find, and, yes, it's a 120V model for the US, but I'm only interested in the petrol consumption) it's probably even less fuel: tank is 1 galon (3.8l), enough for 3.4 hours @ 1.6kW or 8.1h @ 400W. Naively splitting between idle and delivered-power consumption, we get 0.25l/h idle and additional 0.54 l/kWh. So taking the numbers from the article (400W full power load which would deplete the batteries in 2W), it can't be more than maybe three/four litres every two days.

[chrlilje]

That is a very good guess for the fuel consumption! We use a Honda Eu10i generator that have a fuel tank size of 2.1 liter.

We (I) fill the generator and start it, and let it charge the batteries until it runs out of gas. We start the generator every day now to avoid running the batteries too low.

Batteries are 6 x 6 V AGM arranged in 6+6||6+6||6+6.

We did consider windpower, but it would have been quite a bit more complicated for our tiny budget. And we would have to have a plan for both days with no wind and days with storm.

My dream solution would be a bigger battery bank, and a generator that can start automatically when the battery voltage drops under a certain level. Add a huge fuel tank and it would have been able to run unvisited for weeks.