Energy resources of the 21st century: problems and forecasts. Can renewable energy sources replace fossil fuels?

The state of the art and the major trends of development of world energy engineering are analyzed. It is concluded that throughout the 21st century the role of alternative sources will remain rather modest. Fossil fuel will still be the major source of energy until the end of the century. Because of depletion of accessible oil resources, the proportion of crude oil in the world energy balance will constantly decline, while the proportion of natural gas will grow. It is shown that energy production from any source, including alternative sources, cannot be environmentally benign if the scale of production is large. In the long term, humanity has no sources other than fusion energy, but transition to this source would not solve the problem of the planet's heat balance.