What we had read mostly as a fiction is right here in front of us. The Planetary Societyprepares itself to launch the first spaceship powered by Solar Sails hours from now.
The spaceship is going to be powered by a never-ending fuel: light. The spaceship will be thrust ahead by large number of photons striking the surfaces. As each photon carries energy, after every collision some amount of energy is used to propel the reflectors ahead. As you might have guessed the acceleration because of this energy is not going to be too large, it is around 1 millimeter per sec2 which is way to little as compared to rocket powered space ships, but the tremendous advantage of solar sails is the acceleration is constant. So over a period of time the spaceship will be accelerated to such great speeds that a rocket-powered spaceship can never achieve.