Abstract: A solar energy collector of the kind which heats a fluid employs removable energy transfer tubes having an outer glass envelope and an evacuated space between the envelope and an inner metal tube. A manifold is provided to which is connected a number of inner elongate metal tubes having an open end over which are then arranged the energy transfer tubes. The inner metal tubes and the energy transfer tubes form an annular space which is provided with helical fluid flow channels to increase the thermal energy transfer from the radiant solar energy to the fluid. The energy transfer tubes are removable and are not installed on the operable system until the mechanical mounting and fluid connections are made at the operational location.