A 50 μW Microbial Fuel Cell Isolated Energy Harvesting Interface Based on Air Coupled Inductors

摘要

Microbial fuel cells (MFCs) are emerging energy harvesters that are promising for the autonomous supply of remote sensors on the seabed. The low voltage delivered by the MFC's, a few 100 mV, imposes an electrical interface to boost the latter to the sensor's needs. The flyback in discontinuousconduction mode appears to be the best candidate since it allows the maximum power delivered by the MFC to be extracted, the sensor to be electrically isolated from the source and the voltage to be boosted that required by the energy buffering. Our previous work highlighted the significantimpact of the magnetic core loss due to hysteresis and magnetic saturation even at μ -scale energy transfer. In this paper, we propose to remove the magnetic core to suppress these losses. The low density harvested power (100 μ W for 10th cm~(2) electrodes) and low-sizeconstraint i.e., 1 m~(2) scale in seabed remote sensors applications allows us to use 0.5 m~(2) air-core inductance by plugging in a 20-cm~(2) MFC, delivering a maximum power of 90 μ W at 0.3 V. The proposed air-core coupled inductor based flyback achieved60% efficiency experimentally from end to end peak. These results are 10% lower than those achieved with a magnetic core. This decrease is due to the increase in the losses generated in the active components. However, the experimental results are in good agreement with simulations in whicha model of the coreless coupled inductances, extracted from characterizations, is used. Finally, potential improvements linked to custom designed components due to progress in active components such as transistors and diodes are also discussed. A thorough analysis led us to think that in thefuture, the coreless solution may surpass its magnetic counterpart, and hence become a viable alternative.