The same collectors can be used for both heating and lighting. Insulation serves to both prevent heat loss in the winter and heat gain in the summer. Storage elements can be used by both heating and cooling elements. And daylighting reduces the need for interior lights, removing a heat source from the interior and thereby improving the cooling. The difference arises in that in active systems, the heat is then pumped to the load.
Collectors transmit the light to an absorbing material.
The collectors generally have a glaze, which is transparent to the light, but which prevents contact between the ambient air and the absorber. The absorbing material also has a glaze, which readily absorbs the incident visible light, but not infrared light. This damps re-radiation of the heat, minimizing thermal loss. The heat of the absorber is removed by a heat transfer fluid. This fluid is then actively pumped through the system to transfer the heat to a storage element or directly to the load.