An inflatable solar energy collector. The device uses two elongated and pressure-stabilized air chambers with a trough-shaped reflecting surface in between. The curvature of the reflecting surface is adjusted by adjusting the differential pressure between the two air chambers. The device can be configured to provide a focal point outside the air chambers or inside the air chambers. For the version using the external focal point an external energy receiver is appropriately positioned. For the version using the internal focal point, the receiver is mounted inside one of the air chambers.