explain why magnets are so dominant?
I would say that this is because magnets are easy to manipulate mechanically, and any movement of a magnetical field entails a movement in an electric field.
Most of the energy generation methods used on a large scale involve a change of energy from one form (chemical, mass, kinetic) to kinetic; e.g. Chemical energy in coal is released as heat which is then converted to kinetic energy in steam.
Magnets seem to me to be the only to convert large amounts of kinetic energy into an electric current.
Gigantic water falls (Hoover dam for example) also make a lot of power by turning generator. And these are certainly the best since the power source is free and the pollutants are near zero.
Wind turbines are inefficient, expensive and not overly impressive at this time.
I question both statements. While the running of HEP stations does not require much energy input or pollutant output, the construction of a "gigantic water fall" involves "gigantic" amounts of concrete. Hoover dam, being your example, contains some 2,480,000 m3 of concrete. As concrete sets a chemical reaction takes place, emitting heat and carbon dioxide.
The carbon dioxide CO2 produced for the manufacture of one tonne of structural concrete (using ~14% cement) is estimated at 410 kg/m3
http://en.wikipedia.org/wiki/Enviro...e#Carbon_dioxide_emissions_and_climate_change
Hence the total amount of carbon dioxide emitted from the Hoover dam during construction could be in the region of 1,016,800 tons. I'm not saying HEP is an environmental disaster (quite the contrary) but don't be ignorant of it's impacts!
"Wind turbines are inefficient, expensive and not overly impressive at this time."
Typical commercial turbine: 2 MW in size and cost roughly $3-$4 million installed, which would be expected to
run for about 120 000 hours. That's ~240,000,000 KWh, so roughly $0.016 per KWh. But I fear this is an under estimate, as NO wind turbine constantly runs at rated power, or anywhere near it!
http://en.wikipedia.org/wiki/Cost_of_electricity_by_source
Suggests $/KWh for wind is $0.097, so I was out by a factor of about 6
Any way to the point... Natural gas is cheapest per unit energy, then HEP, then wind. So wind is not overly expensive.
Wind cannot be >56% efficient due to Betz' law, which basically uses the idea that the more efficient your wind turbine the slower the air after your turbine, which in turn slows the air before the turbine (which in turn lowers your power output). Read up on it, it's a great proof!
