Most "alternative" sources of energy wouldn't amount to a hill of beans. Back in the Carter Adminstration, a pile of money was spent on "alternative" energy with not a lot to show for it.
We have, in this country, proven reserves that have been made off limits by legislation and moratorium. And we also have huge petroleum reserves tied up in oil shales and "heavy oil." Before another planet would ever become a source for this planet, we would utilize the existing terrestrial sources.