Research Of Energy Harvester For Microbial Fuel Cells

Coupled with the contamination of the environment and consumption of fossilenergy, biomass energy has received great attention. Microbial fuel cell is a kind ofnew energy based on domestic wastewater, which can dispose sewage water, andgenerate electrical energy at the same time. The reaction conditions of microbial fuelcell are gentle and fuels are abundant in daily life. However, the output power ofmicrobial fuel cell is lower than1mW, open circuit voltage is about0.7V. Harvestingenergy from feeble electricity is a great challenge. Stacked cells in serials couldimprove the output voltage generally, but voltage reversal will appear in microbialfuel cell when in serials, namely, the polarity of cell has changed, causing the voltagedecline rapidly. Thus, power management system for micro power and solvingvoltage reversal are of great significance.This paper employs charge pump to harvest electrical energy from microbial fuelcell, and stored in super capacitor to be the start up voltage for boost circuit. S882Zcharge pump could operate at0.3V input voltage. The high capacity and longoperating life of super capacitors lead to be perfect energy storage element. When thevoltage of super capacitor reaches the set threshold, capacitor starts to discharge via aswitch turns on. Then the voltage is boosted for the electrical device. When thevoltage drops to a certain value, switch turns off, capacitor begins to charge again.The operation of the designed system is automatic and periodic.With regard to voltage reversal when cells stacked in serials, this paper uses amethod that turn cells in serials into connecting capacitor in serials. At the beginning,microbial fuel cell charge super capacitor respectively, then stacking energy storagecapacitors in serials when the voltage reaches a set threshold. Capacitors discharge to be the power for the load. Fuel cells have not been connected in serials directly, so asto prevent the appearance of voltage reversal.At the load end, this paper designs a wireless sensor system. The systememploys DTH11temperature and humidity sensor and nRF24L01wireless module.STC89C52is the micro controller, and using CH340T to realize USB turn to serialport. When the power management system output5V and3.3V, micro controller andsensor starts to work, detect the parameters in the environment. The data are sent bymeans of nRF24L01, receiving terminal receive data and transmit to computer. Thepaper also designs serial port software based on virtual instrument, realizing thecommunication between micro controller and computer, including data display andstorage.As can be seen from experimental results, microbial fuel cells have stable output,the designed circuit implements energy harvesting from micro power, and drivingwireless sensor finally. This demonstrates that microbial fuel cell in the benthicdeposit could be the power source for remote sensing system.