This book presents the results of a study of long-term perspectives for energy development of the world and its main regions, performed at the Siberian Energy Institute of the Russian Academy of Sciences (Energy Systems Institute since 1998). The methodological approach, the 10-regional Global Energy Model (GEM-10R) of the world energy system, energy demand forecasts, data on energy resources and energy technologies, and results of calculations based on mathematical models are described. Particular attention is given to determination of energy requirements and peculiarities of its technological structure that are caused by mankinds necessary transition to sustainable development. Economic and ecological consequences of constraints on greenhouse gas emissions and scales of nuclear energy production, as well as assistance of developed countries to developing ones are investigated. Problems of cheap oil, gas and uranium resources depletion, fuel price growth, synthetic fuel production and new energy technology implementation are analysed. The book is intended for specialists in energy and economics, as well as students and postgraduate students of technical high schools and universities. ac