Energy Harvesting in Wireless Sensor Networks

Sammanfattning: Over the past few years, the interest of remote wireless sensor networks has increased with the growth of Internet of Things technology. The wireless sensor network applications vary from tracking animal movement to controlling small electrical devices. Wireless sensors deployed in remote areas where the grid is unavailable are normally powered by batteries, inducing a limited lifespan for the sensor. This thesis work presents a solution to implement solar energy harvesting to a wireless sensor network. By gathering energy from the environment and using it in conjunction with an energy storage, the lifetime of a sensor node can be extended while at the same time reducing maintenance costs. To make sensor nodes in a network energy efficient, an adaptive controller of the nodes energy consumption can be used. A network consisting of a client node and a server node was created. The client node was powered by a small solar cell in conjunction with a capacitor. A linear-quadratic tracking algorithm was implemented to adaptively change the transmission rate for a node based on its current and previous battery level and the energy harvesting model. The implementation was done using only integers. To evaluate the system for extended run-times, the battery level was simulated using MATLAB. The system was simulated for different weather conditions. The simulation results show that the system is viable for both cloudy and sunny weather conditions. The integer linear-quadratic algorithm responds to change very abruptly in comparison to a floating point-version.