Like the title says is it possible to build a generator which will make around 5 watts of power for an hour? or even 2.5 watts in 30 minutes without needing constant human interaction like a hand cranked generator? I have been looking at things like the grandfather clock mechanism, hanging a mass and letting gravity produce electricity by pulling it towards the ground and even liquid powered such as water flow through a dynamo. Is there some way that this can be done? For gravity power I have been using the potential energy equation where: potential energy = mass x gravity x height This is the equation I tried: pe= 20 x 9.81 x 1.5 which comes to 294 joules. Because I wanted to produce 5 watts in an hour I used the equation: watts= joules / seconds So: W = 294 / 60 which gives 4.9w This is basically 5 watts but I haven't taken into account the efficiency losses which I don't know how to calculate but if I say that the efficiency is 50% then according to the equation if I have the gearing correct I could make 9.8 watts in 30 minutes before efficiency losses. Are my equations correct? I want to say that this is not a homework question, this is just something that I am interested in building as my final project for my Design Technology class.