A collector for heat energy from a solar or other source is in the form of a body of given thickness. The body is composed of a packed plurality of particles of coal, and each of those particles is selected to have a maximum size of between approximately one-fourth and one-half of the given thickness of the body. Substantially permeated throughout the particles is an elastomeric binder. It forms a continuous coating over the surface of the body and cohesively rigidifies the particles together, so that the body is at least substantially self supporting. A major surface of the body is exposed directly to solar radiation as a result of which heat energy is absorbed within the body. Subsequently, that heat energy is re-radiated or otherwise conveyed out passively into an adjacent space or interactively with a fluid moved across a surface of the body or through the interior of the body.