The EnOcean EMDC sensor is a self-powered BLE device that monitors the environment for human movement and measures the light level via a dedicated illumination sensor. It has an in-built solar cell and internal energy storage which enables it to operate for up to 4 days in total darkness when fully charged.
To gain full charge the solar cell of the sensor requires exposure to a minimum of 200 lux for a continuous period of 6 hours.
In most applications the sensor can be charged based on the available light in the environment. The best light source is natural daylight, but any artificial light emitted in the visible spectrum can be used (regardless of whether this is LED, incandescent, fluorescent or other).
There is also the option to add a CR2032 battery to act as a backup in situations where there may be infrequent bright light, consistent low light, or total darkness.