[en] The authors propose a synthesis of works performed by the Prospective 2100 association on the issue of energy. They comment the strongly increasing energy demand which is related to demographic growth and urbanization, the evolution of energy supply at an always increasing cost, and the needed evolution of the energy mix. They notice that electricity demand increases faster than the global energy demand. They discuss the evolution of solar and wind energy (challenge of energy storage), the development of the industrial sector of electricity production and distribution, and the impacts of political choices on energy sectors. They discuss the possible evolutions of the energy sector which are based either on the improvements of existing technologies, or on the emergence of new technologies on the market. They outline the various environmental, economic and geopolitical constraints, state that they expect a great energy transition during the 21. century, discuss the objectives defined for 2050 in terms of reduction of greenhouse gas emissions, and draw perspectives for the second half of the century

[en] Central-station electric power for spacecraft has been explored conceptually for over two decades as a solution to the economic delivery of high power levels over long periods of time. However, all spacecraft designs to date have been based on the use of onboard supplies-solar, nuclear, and chemical-because the total space power demand has not yet reached the levels at which dedicated space power depots would be economically viable. Nevertheless, the growth in projected power demand for the next several decades could warrant the use of such dedicated space-based powerplants. This paper examines and assesses the various technological options for space power generation and transmission and the system considerations associated with the space-based central-power-station concept. (author)