Abstract: Utilization of solar energy by the production of steam within a cavity created between the surface of a sheet of water and a floating pontoon, the heat collected by a solar energy collector, placed on top of the pontoon, being transferred to the water itself by means of a heat exchanger, the solar energy collector being formed of a number of fixed transparent solid pieces each one comprising a black absorbing surface into which the sun's rays, refracted by the upper external surface and reflected inwards by the lateral surfaces, are concentrated.