Solar energy collector system with cylindro-parabolic mirror

In a process for keeping under control the operation of a solar energy collector of the kind having heat-receiving tubes which are thermally expansible along the longitudinal axis thereof, and solar heat transfer accessories associated with said tubes and comprising (i) cylindro-parabolical concave mirrors rotatable substantially about the focal axis thereof to train said mirrors towards the sun under normal working conditions, said mirrors concentrating heat radiations of the sun on said tubes which extend substantially along said focal axis thereof, and (ii) means for circulating heat absorbing fluid through said tubes to carry away therefrom the absorbed heat, the improvement comprises the steps of detecting excessive longitudinal expansion of said tubes due to overheating thereof, and applying the thus detected excessive longitudinal expansion to check said overheating by action upon said solar heat transfer accessories either by reducing the amount of heat input provided from said mirrors or by increasing heat output carried by said circulated fluid.