Again, it's hard to explain so I'll do my best. Most machines in the world are very inefficient. They use more engery than they return. For example if you were to take a hydroelectric power plant and use the engery generated from the power plant to then pump the water back into the reservior you would use nearly twice as much energy lifting the water back into the reservior as you would create from the water tumbling through the turbine. Or, if you were to use the electricity generated by those wind mills you see all voer the place now to power themselves without any wind they would not have the power to spin their own blades.
Example:
A water driven generator can generate enough power for the average home when given enough water pressure and constant flow. When the water in question is naturally occuring, meaning that the the flow of water happens naturally, this machine is considered very efficient since it uses the kinetic energy from gravity to generate this electricity. It also however creates a byproduct of heat, showing that it is not 100% efficient and requires a continuous supply of water to continue to work. If the generator were forced to use the water over and over again using a pump that fed 100% of the energy created by the hydro power generator, the pump would pump less and less until it stopped because of the efficiency lost in the process of changing the kinetic energy to electricity. The ONLY way it could be considered 100 percent efficient would be to have it in a vacuum which would remove the friction form the equation and allow 100 percent of the energy produced to be returned to complete the cycle.
example 2:
We have unused kinetic energy from falling water. Sadly the extremely small volume of water would produce very little energy at all. It would in theory possibly provide a very small trickle charge to a battery, however it would cost more to purchase the unit than it would return for quite some time. This is because it requires a lot of head pressure to actually spin the blades of the turbine. The most efficient one I have heard of uses 4gpm through a 1/4" nozzle at the bare minimum and 250gpm maximum. Gravity fed overflows returning to a sump cannot produce the pressure to make the unit begin to charge. There would have to be a high pressure pump like the ones used for strip mining or sand blasting or a much higher volume of water in a longer drop from a guaranteed source.. ie naturally occuring springs.
