Green Energy

Short:
Coal will become cleaner and greener, via better scrubbers, carbon capture and gasification. It is still the cheapest and most abundant energy source we have.
Cellulose ethanol is a lot more promising than corn ethanol which is is a big threat to biodiversity and the poor.
Reducing transmission loss would save us 20%.

Long:
Nuclear Fusion could be the answer.
Probably not hydrogen, as it is too expensive and too explosive.
I heard that 100 square miles of solar in space would be enough for all our needs, how to get the power back to us is the problem.

Energy

Short Range Trends:
Biofuels will destroy rain forest and raise food prices.
Peak oil will hit.
Nuclear will be back in fashion.

Long Range Trends:
Hydrogen could be the answer.
Solar is a big part of the answer.
Biofuels will be forgotten.
Ways to reduce transmission loss will be big.
Natural gas prices will rise faster than oil.