Our invention consists of two separate and discrete families of polymers, e.g. thermosetting Fiberglass Reinforced Plastics ("FRP") and thermoplastics. Both are used as the materials of construction to fabricate solar thermal collectors. These families have the same general configuration and are based upon the same principles. Both families are used in a form that some of the walls of the collector are translucent. Both families incorporate a passage through which the thermal fluid flows. Both families make use of dyes to absorb energy from the sun in the fluid and the collector walls. Each of the families makes use of improved collector configurations and designs and special operating approaches. Each family can serve different markets for different solar thermal collectors. In particular, FRP stands alone as an emerging new category of materials for a broad range of applications including everything from novel solar thermal collectors to exotic airplanes.