I'm sorta curious about that, too, Carol. But whatever. Anyway, here goes:

Two I can think of, off-hand.

I once read an article about the possibilities of placing large turbines underwater in the various currents around the earth, such as the Gulf Stream, to provide electricity. This would be the same principle as wind power. As far as I know, nothing has ever been done along that line. Main objection (similar to objection to wind farms re:   migrating birds) is that it might interfere with whales and fish migration, but with a little ingenuity, this could certainly be dealt with.

Another is a system that would work especially well on the moon, to provide electrical power for a moon base, but it would also work effectively in desert areas on earth. It's based on the fact that ground will absorb the sun's heat during the day, and radiate it at night. A system of pipes containing a fluid is buried in a large patch of ground (it could by acres or square miles, depending). Then, a large sheet of insulating material set on rails, covering half the area containing the pipes. During the day, the patch of ground beneath the sheet is shielded from the sun, so it grows cooler. At night, the sheet is rolled (the purpose of the rails) over the adjacent half containing the pipes. The following day, the sheet is returned to its original position, and so on, alternating day and night. The result of this is that the patch that is covered during the day grows colder while the patch with is covered at night (preventing it from radiating its heat away) grows hotter. This causes the fluid in the pipes to circulate like crazy, and it can by used to drive turbines. After the system is installed, the cost of maintenance would be minimal.

[Maybe I should keep this idea, come up with while figuring out some details for a science fiction story I never got around to writing, a deep, dark secret. I am reminded of Arthur C. Clarke's brief article entitled "How I Lost a Million Dollars in my Spare Time," in which he describes how some years before, he wrote an article about how three satellites set in geosynchronous orbit could provide communications links to the entire world. He didn't patent the idea because he didn't think it would happen for another century or so. Shortly thereafter, the first Telestar was launched. But wotthehell, I'm a generous guy. I'll give it to the world for nothing.]

But seriously, folks, I advocate that we place a large funnel over the Capitol Building in Washington, D. C. (the White House as well, and perhaps over state capitol buildings and city halls) to capture the vast quantities of hot air and pipe it throughout the country to provide heat for residential housing.

Don Firth