The system works by having a pair of tubes that contain a cup each. When the cup is at the top of the tube, a valve opens allowing water to fill the cup. As water fills the cup, it gets heavier and starts to move down the tube. Once at the bottom of the tube a valve opens to drain the water, thus the cup is now lighter and can be pulled up by its partner cup that would be filled with water. The pair of cups moving up and down alternatively via a chain can now power a generator by meshing a sprocket to the chain.
An interesting feature of this design is that you can line up more pairs so you have a row of them and it would improve the output you can get.
Another possible configuration to "stack" the system is to have the pairs where one is upstream of the other thus requiring only one water channel
In this step the 2nd and 3rd pictures show the starting position of each cycle, half way through the cycle the condition is just mirrored where the left side cup is at the top and the right side cup is at the bottom
Here are the screenshots of the design in made in Solidworks
(I really wanted to put in an animation of it working and spent many hours/days getting it to work but my laptop just cant handle it and crashes too much to get any usable animation. but i will try and get one in later)
Please vote for me in the CAD contest if you like this concept, I hope to get some of the parts printed so I can actually test out the device as my access to tools and materials to fabricate this is very limited and quite insufficient.
As pointed out by Kiteman, frictional lose will be an issue, thus maybe the tube can be switched to a pair of guide rails since the tube is only there to guide the cup to the valve mechanisms. As for friction in the chain i guess we just need good lubrication