Design Of Household Electrical Wire Energy Harvester Based On Electromagnetism

The extensive application of wireless sensor network put higher request on the store ability of batteries. Nowadays, majorities of the sensors are charged by the self-contained batteries which may be ran down some day, the maintenance of the battery and the labor cost will surely increase the total cost of the system. With the rapid development of energy harvesting technologies, the capacity of the batteries can be enlarged, and it is economical, eco-friendly and easy to use.This dissertation shortly discussed the fundamental rules of electromagnetism and transformers first, then an energy harvesting device dedicated to household power transmission lines was designed based on the aforementioned rules. The radial field distribution around the transmission line was derived from the Biot-Savart Law and Ampere's Rule. With an available toroidal core, the multi-relationship between the load power,load current, core cross area and the induced voltage were studied quantitatively while some basic parameters were calculated, The results demonstrated that the device could work properly under an current as large as 93 A. A voltage drop of 30 mV was got by the semi-automous rectifier circuit. A power density of 1.44mW/cm3 was reached when the load current was 10 A, and it can fully satisfied the power requirements of some low power device. To validate the accuracy of the theoretical deduction, an experiment was made, the open voltage and short circuit current were tested and recorded under certain condition. A power transfer efficiency of nearly 86% was got when compared the experimental data with the simulated result, then the data was fitted properly.This dissertation simulated and processed the data in MATLAB. The results showed that when the secondary turn was 500, the distance between the power line and the magnetic path was 8 millimeter, an induced voltage of 1.4V could be got, with a boost-up circuit, the expected voltage range could be reached. The magnetic field strength was far less than saturation flux density of the core when operating in load current of 10 A which mean that the device can operate reliably, the total amount of power harvested is 25 milliwatt and it can fully satisfied the requirement of the wireless sensor.