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Solar cells are one common choice to power energy-autonomous wireless sensor nodes (WSNs). There are different approaches to improve their service and reliability via solar energy prediction algorithms, to allow the WSN to “know” about the future energy income All these algorithms require information on the energy income of the sensor node obtained e.g., via separate measurements of light intensity or via monitoring the current flow to the WSNs energy storage. Here, we present a method to determine the energy income via temporarily switching the PV cell’s input current to a capacitor for determining the energy income by the accumulated charge. The data are compared to measurements with a pyranometer. This system provides advantages with respect to the consideration of the multiple different losses in the WSNs power management.

Abstract. In our last year's PowerMEMS contribution we presented a proof-of-concept of a variable reluctance harvester for the application in a railroad surveillance system. It was shown that intermittently closing a magnetic circuit could supply power output in the range of mW's. The test setup used showed unwanted energy pickup from the electro motor used. In this paper we present thorough measurements of the reluctance circuit with a compressed air motor to exclude the effects of the above mentioned magnetic stray fields. The effects of eddy currents and moment of inertia on the output power, the optimal coil position on the stators, and effects of different magnetic field strengths are studied. The gap width is set to a fixed value of 14 mm, representing a realistic scenario.

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