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Toward a Sustainable Global Energy Supply Infrastructure : Net Energy Balance and Density Considerations / Ioannis N. Kessides and David C. Wade, Washington DC : World Bank, Jan. 2011, 30 p. (Policy Research Working Paper ; 5539.)http://www-wds.worldbank.org/external/default/WDSContentServer/WDSP/IB/2011/01/18/000158349_20110118143248/Rendered/PDF/WPS5539.pdfThis paper complements previous work on the economics of different  energy resources by examining the growth potential of alternative  electricity supply infrastructures as constrained by innate physical  limits. Coal-fired generation meets the criteria of longevity (abundance  of energy source) and scalability (effective capability to expand to  the multi-terawatt level) which are critical for a sustainable energy  supply chain, but it carries a very heavy carbon footprint. Renewables  and nuclear power meet both the longevity and climate friendliness  criteria. However, they vary in terms of their ability to deliver net  energy at a scale needed for meeting a huge global energy demand. The  low density of renewable resources for electricity generation and the  current intermittency of many renewables limit their ability to achieve  high rates of growth. And a significant global increase in nuclear power  deployment could engender serious risks related to proliferation,  safety, and waste disposal. Unlike renewable sources of energy, nuclear  power is an unforgiving technology because human lapses and errors can  have ecological and social impacts that are catastrophic and  irreversible. The transition to a low carbon economy is likely to prove  much more challenging than some optimists have claimed. (© WB)