Nice examples of what 1 square metre can give you.

However, what if it were 1 square metre of tidal range estuary, what would the energy possible be there? The potential energy of a 2-3 metre tidal range wouldn't be insignificant.

Equally, what about 1 square metre of wave prone shore?

Both have the major advantage that they aren't currently used as cropland.

Along the same line, after reading about the Air New Zealand trial running of a Boing 747 on biofuel
http://www.inthenews.co.uk/news/autocodes/countries/new-zealand/boeing-747-fly-on-bio-fuel-$1141111.htm

I did some rough calculations based on a fuel consumption rate of 3378 gal/hour and an optimistic production rate of 150 gallons of jet fuel per acre of soybeans. A single round trip flight from LA to New Zealand and back would use more than a square mile of soybeans. Maybe better, we could ALL start eating a lot more French fries.