The Research Of Energy Harvester For Microbial Fuel Cells Based On Optimum Output Power

In our energy-intensive society, greater attention has been paid to any energy-abundant substance. The diminishing fossil fuels and a large amount of environmental pollution have been stimulating the exploration for renewable and pollution-free alternatives. Bioelectrochemical systems(BESs) are treated as an emerging technology due to waste treatment, electricity generation, bioremediation and so on. Up to now, major investigable BESs have been implemented at laboratory scale such as MFCs devices. MFCs have so many advantages such as abundant fuels, clean product, gentle reaction condition, promising prospect. Usually, the output of simple MFC is very low. The output power of an individual microbial fuel cell is lower than 1mW, and the open circuit voltage is about 0.7V. In the real applications, an individual microbial fuel cell cannot drive electrical devices directly. When many MFCs cascade, the weaker MFCs will produce voltage reversal. The voltage reversal will reduce the total output of many MFCs cascaded. In this literature, designing power management system for micro power and solving voltage reversal are of great significance.In this literature, the electrical characteristics of MFCs are researched. The most proper PH of MFCs should be selected. Thendesigndynamically control circuits for microbial fuel fells in series connection to solve the problem of voltage reversal. A dynamically-control evaluating system(DCES) has been designed to evaluate the performance of MFCs as a power source. So the designed circuits can choose the proper super capacitor to store the energy. Thecharge pump to harvest electrical energy from microbial fuel cells should be also designed, and the energy can be stored in super capacitors. The output of the charge pump can be the start up voltage for boost circuit. The input voltage of 0.3Vcan drive S882 Z charge pump. This paper usessuper capacitors as energy storage element, because it has high capacity and long operating life. Super capacitor begins to discharge through a switch,when the voltage of super capacitor reaches the set threshold. Then the voltage is boosted for the electrical device. It also design a feedback circuit to connect the output of the boosted circuit to VM of the charge pump. The charge pump can stay sleep state to save energy. This paper uses a dynamically control circuit that can connect MFCs in series when voltage of MFCs are all positive, disconnect MFCs when voltage of some MFCs are negative. Thus it can remove voltage reversal.The designed dynamically control circuits can remove voltage reversal efficiently. The designed dynamically-control evaluating system can also choose the proper capacitor. The energy harvesting circuits can collect energy and the feedback circuit also improves the efficiency of operations.