Efficient solar powered wireless sensor solution

In this paper, two different solutions for efficient solar powered sensor networks are presented and compared. Some fundamental considerations on the interaction of the solar cell, the storage capacitors, the DC/DC converters and the wireless radio transmitter are reviewed. The challenges for implementing a direct DC/DC conversion for powering wireless sensor networks are addressed. The realised circuit guaranteed an autonomous start up and a continuous operation of the entire wireless radio transmitter network from an illumination level of above 400 lx. Alternatively, with improved energy storage capability and best possible harvesting of solar power, a two-step DC/DC conversion system was realised. The key component of the supply scheme is a custom designed, low power ASIC which controls the solar cell at the MPP (maximum power point) to guarantee the most efficient use of the available solar power. The realised low power ASIC consumed only 800 nA of DC current to fulfil its control task.