Energy

We have these major sources of energy available to us, in no particular order and not including fossil fuels that we currently rely on for the majority of our energy today:

• Solar: [1]  photovoltaics , solar thermal  (such as power tower, ocean thermal energy conversion  and solar updraft tower ). Prospective: solar power satellite  and stratospheric solar array
• Wind: land-based wind turbine, off-shore wind turbine. Prospective: jet-stream sky windmills 
• Ocean: wave, tidal, ocean currents
• Hydro-electric
• Nuclear: nuclear fission. Prospective: nuclear fusion  and accelerator-driven thorium-fuelled energy amplifier 
• Geothermal: shallow geothermal heat pumps, volcanic related geothermal, 'hot-dry-rock' geothermal . See also Future of Geothermal Power (in the United States) from MIT 
• Biomass: vegetable oil, compost methane, fermented crop waste, algae, sustainable wood, and clean burning of organic waste, animal dung and rubbish

The energy available from solar and geothermal alone far exceed our current and likely future energy requirements and could sustain humanity indefinitely. Also steadily increasing energy efficiency , due to improved system design and increasing cultural awareness should become a significant factor in our energy usage.

The issue currently is economics. The bottom line is that it is still cheaper to pump oil out of the ground and burn it to produce power than use other methods. However these other energy sources are sitting in right front of us waiting to be harnessed. It may be that open-source methods can by-pass the economics issue to enable plentiful, environmentally friendly power.