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The thing that we must keep in mind with any form of "alternate" energy is the big picture of energy payback. If it takes more energy overall to make an alternate energy source than it will create in its lifetime, we should not do it. Quoting financial payback periods is not relevant in the equation.
eg. Energy payback:
To create a solar cell we need to take into account how much energy is needed to mine the sand, purify it to create the silicon, mining of the metals to make the conductors, the metal frames, the protective glass, the backing material that the cells sit on, the glues and other materials, the cost of transport of all this stuff etc. Also add in the cost of keeping them clean and running efficiently. ONLY if the equation produces a net energy profit should we implement it on a larger scale.
Financial payback:
The financial payback may be 10 years for something like this, but that is only because these sources (cells, wind turbines, wave technology platforms etc) are manufactured using (often non renewable) power on an industrial scale, which is purchased at a much lower price. So if a solar panel was to cost $1000 today, but the cost of the energy to produce it where to be purchased cheaper and so the SAME panel could now retail for $800, the financial payback would now be 8 years. The energy payback would still be the same and, in the big scheme, this is the only part of the equation that will determine if the impact on the environment is lessened.
We would be foolish to burn up huge quantities of fossil fuels just to create solar cells to replace the fossil fuels for electricity generation, if the cells then "died" before they produced the amount of energy it took to make them. This does not mean we can't continue into research to find better alternatives, even at a net energy debt, but we must be careful not to implement a solution on a mass scale until we know the answer to this equation.
The other problem is that no-one seems to want any of these solutions in their backyard. When was the last time we saw in the paper that a comunity has welcomed a couple of hundred wind generators along their coast or mountain ridge? Unfortunately, they are best suited for locations that also have "great views". They do not perform well at the bottom of a valley stuck down below the tree line!
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