Why are paddle wheel electric generating setups not used on all our rivers and streams in the USA?

Question

These are non polluting, continuous, cheap, do not need dams, and produce their power in each locale thus reducing transmission costs. They could be fitted with exercise equipment for people's health needs which could add to the power production as well.

Answer 1

without a dam, the power generation would be so low that the return on investment would not be very attractive.

Answer 2

If you put a paddlewheel in a stream and have nothing else connected to the shaft, the paddlewheel will turn fairly easily.

However, when you attach a generator to the other end of the shaft, it now takes a significant amount of force to turn the paddlewheel. In order to get that force, the water needs to be directed such that the flow will concentrate on the paddlewheel and there must be sufficient change in height (or "head") between the inlet and outlet in order to provide that force on the paddles.

Even then, the transfer of energy from the water to the generator is quite inefficient, so you're better of redesigning the paddlewheel into a turbine whose blades do a better job of extracting the energy from the water.

And you have to make sure that the paddlewheels don't harm any of the wildlife in the water, and that the plant or animal life in the water doesn't cling to the blades and slow or stop the wheel from turning.

Not only that, but the water flow needs to be fairly constant, or you end up with hours or days or weeks where the paddlewheel produces no electric energy. Typically it requires a dam that will "store" the water flow until it's needed for the generator. And then, all the downstream users of the water will likely complain about insufficient supply.

So by the time you end up with all the engineering and environmental concerns addressed, you end up with relatively little energy out of a significant cost of installation. That's why all the commercial hydroelectric plants are only on the major water supplies; enough energy is available to get a reasonable return on the investment.

Of course, as the costs for traditional sources continue to rise, the economic balance will shift and perhaps smaller sources may become justifiable; however, the balance even now heavily favors traditional sources.

Answer 3

You can't use a paddle wheel without a dam to control the water flow.

Look at all the mills in the 1800s when water powered mills and factories were very common, as that was the only source of power. Visit one of the preserved sites in New England. They all involved extensive dams and canals.

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