Ah yes, methane hydrate. *The current poster child for doomsday scenarios. *
There are sufficient quantities of it 'buried' at the continental shelves that if suddenly cuts loose, the greenhouse effect will kill us all... *or so the theory goes.
Incidentally, it won't burn underwater, but it's the high pressures that enable it to be semi-solid at the relatively high temperatures. *The rising temperature of the oceans is the motivation for the doomsday scenario above- at some point, the pressure is not going to counteract the temperature, and huge blobs of methane are going to boil to the surface. *The release of pressure will cause even more methane hydrate to vaporize, and entire deposits will 'blow up'. *Further conjectures have the sudden shift in pressures causing earthquakes and tsunamis.
I am very interested in alternative energy sources as well. *And claiming as my alma mater the school that set off the whole 'cold fusion' fiasco, i made a certain amount of curious inquiry into the phenomenon. *The main problem was that the two 'scientists' called what they observed 'cold fusion'. *It's an interesting, if rather esoteric phenomenon, and may actually produce excess energy (many other have tried to repeat the experiment, with rather low degrees of success). *However, there's no justification for calling it fusion of any kind.
When they believed they were getting energy production, they should have reported it as such, and not called their supposed discovery 'cold fusion'.
Anyway, i think you are writing off wind power too quickly. *It will never provide for all of our energy needs, but if judiciously (and without legal entanglement) engineered, a non-trivial percentage of the population could get their power locally. *That's the big pro of wind power: local production, which forgoes the need for lossy transportation of the power over long distances.
I attended a seminar on campus a few months ago about the success of a 'community' wind turbine out on the cape, and wind turbines have come a long way in the last few years. *
As with any source of energy, there's a tradeoff. *In this case, it's really, really hard to convince people to put up a tall windmill in 'their backyard'. *One of the observations in the presentation was that in certain european countries, where people are a little less obsessed about their view and a little more community-minded, community-owned wind turbines are common and provide a remarkable fraction of the power. *In contrast, in the USA there aren't many civic turbines, and putting one up becomes a legal nightmare.
I believe the problem with tidal generators is that the power is very 'dilute', if you'll excuse the expression. *Not only is the tide a phenomenon with a cycle measured in hours, but the amount of power to be garnered from any random square meter section of ocean is very small with each cycle. *How do you capture the energy when it is so spread out? *Add to this the tremenduous strength and corrosion-resistance required for any mechanism in turbulent ocean water, and i think the engineering challenges are quite significant.
Of course the tradeoff for tidal power is loss of coastline and loss of habitat.
One idea that has always appealed to me, but is not likely to happen any time soon, is using solar energy- but collecting it from orbit, where it's not subject to clouds or night. *The tradeoffs here are relatively minor, except for the initial cost and.... and this is the real problem... the issue of transportation. *Beaming it to earth as microwaves or any other waves has all sorts of worst-case scenario nightmares.
If we ever refine the manufacture of carbon nanotubes sufficiently to build the space elevator (another cool campus presentation from the founder of http://www.liftport.com/), we can pipe it down the elevator.
So, it's either wait for super-nanotubes, or i think we're going to have to wait for useable fusion generators before we have a completely suitable alternative energy. *If that doesn't happen soon, we may all have to tighten our belts a bit.