Concrete Recycling
This picture describes an idea for using the drop in the ocean to gather energy from discarded concrete. Landfills all over the U.S. are full of old concrete that has no use. It just sits there. By building a system on a chain that lowers the concrete one could gather the same energy as dropping the weight from an equal sized cliff. It would just take longer because the weight travels through the water at a top speed of 30 mph. you would also have to consider how much energy it would take to drag the weight over to the system. Eventually the fuel used to bring the concrete to the ocean would break even with the energy gained from lowering it and it is of no use to recycle it this way. I personally don't want to use this idea and leave it up to anyone who wants to try it.