Abstract: A solar energy collection system utilizing a fluid, e.g. ammonia, which dissociates endothermically and recombines exothermically and in which work output is obtained directly from the thermochemical fluid stream by expanding the fluid through turbines subsequent to the endothermic reaction. Undissociated fluid is introduced at an elevated temperature into an absorber-reaction vessel which is exposed to solar radiation and subsequently the dissociated fluid is conducted from the vessel to expansion turbines and through a counterflow heat exchanger to allow cooling. A second reaction chamber effects partial recombination of the dissociated products and a separator separates the undissociated and dissociated fluids with the undissociated fluid being returned via the heat exchanger where it is heated prior to entry to the absorber-reaction vessel .