Research On Wearable Multi-Source Collaborative Ambient Energy Harvesting System

With the development of intelligent wearable devices,traditional batteries are difficult to meet the needs of long time standby and light size of intelligent wearable devices.With the development of ultra-low power consumption technology,converting the energy in the environment and human body into electrical energy to supplied to intelligent wearable devices has become one of the effective methods to solve the problem of traditional batteries.At present there are ambient energy such as vibration,solar and thermal energy.Unfortunately,vibration energy is mostly random and discontinuous,and solar energy is easily limited by illumination and time.Meanwhile,for thermal energy harvesting system,its output voltage is usually low,it is difficult to extract independently.Therefore,a single energy harvesting system has certain limitations.Based on this,a wearable multi-source collaborative energy harvesting system is studied in this paper.This paper presents a wearable multi-source energy harvester based on rotary frequency-up conversion technology.The harvester consists of a cylindrical matrix,a rotating eccentric mass,a photovoltaic cell,a piezoelectric cantilever beam,a thermoelectric generator and other necessary components.The rotating eccentric mass block oscillates with the low-frequency movement of the human body,and the piezoelectric cantilever beam is driven to vibrate by introducing magnetic force,thus the vibration energy is converted into electrical energy.photovoltaic cell is placed on top of a cylindrical matrix that converts solar energy into electricity.At the same time,thermoelectric generator is placed at the bottom of a cylindrical matrix and use the temperature difference between the body and the environment to convert heat into electricity.The structure parameters of the energy harvester were optimized,and the energy conversion performance of the energy harvester was tested on an experimental platform.The experimental results show that the maximum output power of the energy harvester is about 4.48m W and the power density is about 1.5*10^-4W/cm³,when the human movement frequency is 1HZ,the outdoor sunlight is sufficient and the ambient temperature is 0℃.A multi-source collaborative energy extraction interface circuit is designed in this paper to co-extract and store the energy harvested by energy harvester.The proposed circuit can stabilize the PV output voltage near the maximum power point（MPP）to achieve maximum power point tracking（MPPT）.The results of simulation and experiment show that the MPPT efficiency of PV is up to 83%,and the thermal energy extraction efficiency is up to 74%,The proposed circuit can efficiently extract three kinds of energy collaboratively.The design of wearable multi-source collaborative energy harvesting system was completed by combining the energy harvester and energy extraction interface circuit,which realized efficient harvesting,extraction and storage of environmental energy.Under certain environmental conditions,the whole system has about 3m W output power.