Flat plate collectors are the most common type of solar collector and consist of an absorber plate, transparent cover, heat transport fluid, and insulation. Integral collector storage employs oversized piping or channels within the collector to increase thermal storage capacity without an external tank. Evacuated tube collectors use heat pipes or direct flow of liquid through glass tubes to transfer heat to a fluid in an insulated manifold. Solar air collectors directly heat air for applications like space heating using glazed or unglazed absorber plates.