Abstract: This invention discloses a solar heat collector and system in which radiant heat energy is absorbed by an absorber plate and the heat is transferred by conduction to a circulating fluid. During normal operation, heat loss from the solar panel is reduced by covering the upper side of the absorber plate with an inflatable transparent cover, and also covering the rear side of the panel with an insulating material which can be an inflatable insulating bladder.The invention pertains more particularly to a solar heat collector which can be inactivated to avoid it attaining excessive temperatures by deflating the flexible transparent cover and allowing it to settle close to the absorber plate, thereby establishing increased heat transfer by conductive and convective processes from the absorber plate to the environment. The deflated cover permits sufficient heat rejection to prevent the plate from attaining excessive temperatures during its inactive or stagnant operating mode.