Energy Sustainability in 20 years?

Would it be possible to get 100% of our energy needs from renewable resources such as wind, water, and the sun in just 20 years? In theory, yes, but for practical reasons it's not likely to happen that soon. With current technologies it would require almost 4 million wind turbines, nearly 90,000 concentrated solar and photovoltaic power plants, and rooftop photovoltaic systems on nearly every rooftop – 1.7 billion, to be exact. Other challenges include a projected critical shortage of certain materials that would be needed, including rare earth metals (found primarily in China), lithium for lithium-ion batteries (half of the world’s reserves are in Bolivia and Chile) and platinum for fuel cells. In addition, we’d have to shift to shift to electric vehicles for transportation.

Fortunately, the technologies for harnessing energy from renewable resources continue to improve each year. It may take some time and effort, but what choice do we have? At current rates of consumption, known reserves of the non-renewable energy resources (coal, oil, and gas) will run out in less than a century.

Reference: Jacobson, Mark Z. and Mark A. Delucchi. A Path to Sustainable Energy by 2030. Scientific American pp. 58-65, Nov. 2009.