Spaceships pushed by LIGHT – the future of space travel?

I really liked the video, but something bothers me: Theoreticaly the solar satellite would continuously accelerate indefinitely. But assuming it will be orbiting the earth, there will be times on which the solar panels are not perpendicular to the sun photon rays, so the acceleration would vary depending on the orientation. Moreover, if the satellite is moving 'towards' the sun, wouldn't the photons be stopping it?