The refining of the structural materials for windmills, or
the silicon for solar cells, are both "dirty" processes
which demand lots of coal (unless nuclear is substituted as
the source of energy for refining.
That's not true. You can use electricity from windmills or silicon to refine the materials needed to make more windmills (or solar cells). The only thing you need coal for is to convert iron ore to steel, but you need this with a nuclear reactor too, and nuclear reactors use much more steel than windmills do, per KW of capacity.
Furthermore, the energy payback time for a wind turbine is the lowest of any conventional energy source. It takes about 3 months for a wind tower to produce enough energy to manufacture another tower. It takes about 6 months or a year for a fossil fuel, and about 2 years for a nuclear plant. Wind towers will probably last much longer than conventional plants; 100 years versus 20 to 50 years. (The turbine engines and blades will last ~20 years, but the tower consumes most of the construction energy.)
Solar cells are much worse. Some do not pay back at all. Others take about half the total useful lifetime of the cell to pay back. Solar cells should be thought of as batteries rather than a source of energy. However, it is the silicon that is energy intensive, and it is mostly scrap silicon from the computer chip business, so it would be thrown away otherwise. You might compare this to burning waste from computer chip factories (except that it produces no pollution, of course). If solar production expanded there would not be enough scrap silicon.
These energy sources also
create huge secondary environmental problems because of the
tonnage of discarded ore and coal emissions - all the more
so because these end-processes, wind and solar, are of
relatively low energy density.
Wind has high energy density. A large modern wind turbine generates up to 10 MW, as much as a large helicopter engine, or twice as much as a modern railroad locomotive. Comparing the "footprint" of the wind tower, this is the highest energy density of any energy source. Comparing the 3-dimensional mass of tower or the number of tons of concrete gives a different answer, but this not relevant. Measured in useful land, the footprint of offshore wind turbines is zero. All of the electricity and all of the automobiles in Europe could easily be powered by offshore wind in the North Sea. Wind in the U.S. could easily generate more energy than all of the oil fields in the Middle East now do, even with today's technology, and much more with ultra-high towers. The mid-east oil fields are not at peak capacity, with no reserve, and they will soon begin a rapid decline, whereas U.S. wind resources will last as long as the sun shines.
Has anyone ever calculated the environmental burden to the
ecology caused by the tons of steel required for a windmill?
Yes. This has been done extensively. Mark Mills and others have misrepresented these calculations, especially by claiming that wind turbines kill birds. Actually, thermal generators (coal and nuclear) kill millions of birds, whereas nobody has ever seen a modern, tall, slow wind turbine kill a single bird. Birds are evolved to avoid things like turbines and trees waving in the wind. They did not do well with 1970s vintage wind turbines with low, rapidly turning blades, but they have no difficulty avoiding the big ones.
Aircraft of all sorts also kill millions of birds, and birds sometimes destroy aircraft. See: http://www.birdstrike.org/
- Jed
