The steep economic growth in emerging countries (China, India, Russia, Brazil) leads to a rise in the world demand of energy; in the short run, the predictable result is the a rise of prices, but in the long run, the basic problem is the limited amount of energetic resources that the planet can offer. Discovering new fields of oil, gas or coal may hardly postpone only with a few decades the deadline for the depletion of these resources, but it is obvious that it is not a solution for one hundred years from now on. Even if we ignore market constraints, this limitation is inevitable, so the necessity of discovering alternative sources seems the only valid approach.