Abstract
It is well known that maximum attainable power is generated at a certain operating point from renewable energy resources. As can be seen in the microbial fuel cells (MFCs) and thermoelectric generators (TEGs), a linear output voltage current characteristic will form a convex output power pattern, where the maximum power operating point (MPP) can be analytically derived. Although operation at the MPP has been widely used from the instantaneous power standpoint, it would not be an optimal operating point in terms of energy extraction if the energy resource has a finite amount of initial energy and follows a quadratic loss model. In this paper, an optimal operating point that simultaneously optimized the harvested power level and conversion efficiency to maximize the energy extraction from an MFC with a finite initial energy was developed. At the proposed optimal operating point, an MFC generated less power, but internal loss was considerably less compared to that of the MPP, which entailed harvesting more energy from the initial energy in the reactor. The proposed energy harvesting scheme can achieve much higher electricity generation efficiency from an MFC that contains a finite amount of energy.