Design and Implementation of Hybrid Energy Harvesting System for Medical Wearable Sensor Nodes

Abstract

One of the solutions used for supplying low-power medical applications is the photovoltaic energy harvesting system (PEHS). In this thesis, the proposed PEHS is composed of a photovoltaic panel, a DC-DC boost converter, a fixed resistive load, and an analog control algorithm. This algorithm is designed based on the output load current. It is implemented using the multisim tool. This algorithm is simple, low cost, and low power consumption because it measures only the output current parameter and does not need multipliers. The power consumption of the proposed load is approximately 39.24 mW. Therefore, the expected working duration of the load is 20.9 hours under continuously operation of the light for 4 hours. Finally, the simulation results illustrate the transient characteristics of the proposed PV system. In this thesis, an autonomous wearable sensor node is developed for long-term continuous healthcare monitoring. This node is used to monitor the body temperature and heart rate of a human through a mobile application. Thus, it includes a temperature sensor, a heart pulse sensor, a low-power microcontroller, and a Bluetooth low energy (BLE) module. The power supply of the node is a lithium-ion rechargeable battery, but this battery has a limited lifetime. Therefore, a photovoltaic energy harvesting system (PEHS) is proposed to prolong the battery lifetime of the sensor node. This PV energy harvesting system is practically tested outdoor under lighting intensity of 1000 W/m2. Experimentally, the overall power consumption of the node is 4.97 mW and its lifetime about 246 hours in active-sleep mode. The experimental results demonstrate long-term and sustainable operation for the sensor node.