...
The actuator generates the electrical energy for required for operation (motor, sensors, radio communication) by means of a built-in thermoelectric generator (TEG) and therefore operates maintenance-free. The TEG harvests energy from the temperature difference between the heating flow temperature and the ambient temperature (usually room temperature), which it accumulates in the internal storage. The energy balance of the actuator is designed to allow operation through 366 days per year when used in typical hot water radiator systems and rooms heated in winter season. An additional energy source such as a primary battery or external power supply is not required. The internal energy storage device is charged upon delivery, so that sufficient energy is available for installation. An extended lack of hot water, for example because of down times or malfunctions, inevitably leads to the internal storage being discharged, which means that permanent and normal operation of the device can no longer be guaranteed.
...