I would like to know why it's an either or solution. Why are wind turbine towers not covered with small solar panels?
Why is it, even though they are often very tall towers, they do not use materials for construction, or in addition to construction, that do not take advantage of electrical current induced due to thermal differences across the material? Etc.

Until PV solar panels improve in efficiency, they aren't viable in the UK. In the UK, current numbers are that a solar panel of today's readily-available technology will not recoup its cost, nor its environmental impact (which is considerable), within its lifespan. In Death Valley, things are rather different, of course. :-)

But even then, you're faced with the issue of area covered. Wind turbine towers are tall and thin, of course, which presents a fairly small area for covering with solar panels, and a vertical surface makes a poor sun-catcher anyway. So it really ain't going to work that well. When solar panels get high-efficiency then maybe, but currently-available stuff just won't cut it.

And as for the 1 microvolt extra - I assume that was a joke, dude? It'd take 11 million 100m-lengths of wire to run one 11W power-saving fluorescent lightbulb. That's the distance to the Moon and back 14 times. That's a lot of wire, mate! :-)

Temperature differences would work if there was a significant difference. But there isn't. Best case, the dry adiabatic lapse rate (rate at which temperature drops with altitude) is 9.8 degC/km. So over a 100m pylon, that's 0.98 degC, which isn't a right lot. A quick search on Wikipedia about thermoelectrics suggests you'd get 40 microwatts from a 5 degC temperature gradient, hence 8 microwatts from a 1 degC temperature gradient. It's an improvement on the long wire though - only 275,000 towers needed to run one 11W fluorescent lightbulb.

Re the steam from power generation, cooling towers are used to preserve the water - but the heat is indeed wasted. That's the idea behind CHP (Combined Heat and Power) schemes which are rather popular in the Third World. They haven't really been picked up in the West though, because (a) it's generally too hard to get the hot water to homes efficiently and reliably, and (b) most places don't need much heating for six months of the year. I believe they're moderately popular in places like Alaska though, where there's a year-round need for significant amounts of heating, and individual towns often make their own arrangements for power instead of relying on the national grid.

Graham.