Jason Godesky at Anthropik offers "The World's Biggest Machine is Breaking Down":

Many of the so-called "alternatives" to fossil fuels rely on the electrical grid. We have seen the problems that nuclear and photovoltaics will face even delivering on their production promises, but even if they were to somehow solve those problems, there is still the problem of the grid itself. Most of the energy sources offered are simply means of generating electricity; this is applied to necessities like transportation through innovations like hydrogen batteries or electric cars. Even so, the electricity itself must be transported from the nuclear power plant, PV cell, or other means by which it is produced, to the car it will power, or the home it will heat, or whatever other task the energy is needed for.

That transportation is provided by the electrical power grid. Sometimes called "the world's biggest machine" by engineers, most of the energy "alternatives" proposed will require it to not only continue supplying us with the energy we use now (and the energy we'd need for economic growth anyway), but additionally to also carry the energy load we will need to replace our fossil fuel usage. This will be an impossible feat, since the current load alone is already breaking down "the world's biggest machine" under the weight of its own complexity.

A few other goodies under the fold as well...