摘要： A solar active envelope module with a high ?exibility degree is proposed in this paper. The transparent module controls the day-lighting of the room, improving the indoor environment, while absorbing the super?uous solar energy inside. That energy is used to increase the e?ciency of heating, ventilation, and the air-conditioning (HVAC) system of the building. This is carried out through a ?ne control of the absorptance of the envelope module. The active envelope module consists of three glazed chambers with advanced coatings and frames to assure a minimum thermal transmittance while allowing transparency. A ?uid containing heat-absorbing nanoparticles ?ows inside the central chamber and is heated up due to the impinging solar energy. Unlike other systems proposed in the past, which included transparency control systems based on complex ?lters and chemical processes, the absorption of the module is controlled by the variation of the thickness of the central chamber with a mechanical device. That is, varying the thickness of the central chamber, it allows controlling the absorptance of the whole system and, as a result, indoor day-lighting and thermal loads. Therefore, a new system is proposed that enables to: ? Dynamically control the thermal loads and solar day-lighting. ? Improve the thermal performance of building envelope and reduce the energy demand of the building. ? Increase the solar fraction of the heating and cooling, and reduce the thermal losses improving the e?ciency of the building. The solar active device proposed in this article is protected by a Spanish patent application (Fundaci ′on Tekniker, Fundaci ′on CENER-CIEMAT, 2014).