Energy Harvesting and Smart Sensing Master’s Research
Microgrids are localized power grids capable of independent operation within the larger electrical network. These smart systems efficiently manage power by monitoring generation, consumption, and environmental conditions. While beneficial for cost savings, installation complexity has limited the adoption of residential microgrids. The next wave of microgrid components aims to simplify user experience through wireless, ambiently powered sensors and controls. Introducing energy harvesting technology, such as capturing light, heat, RF energy, and mechanical energy, into microgrid components further enhances efficiency.
Integrating energy harvesters into microgrid sensors, eliminates the need for power cables, streamlining deployment and reducing maintenance requirements for residential microgrid systems. My research aims to to minimize the labor and decision-making required of an end user who has decided to implement an energy harvesting sensor. I aim to show that these types of harvesting devices can be created using off-the-shelf components. In my research, I analyze the feasibility of using different types of energy harvesting to power various sensors and the benefits and drawbacks of available components.
Basic Microgrid Layout
Amount of Instantaneous Power Harvestable From Sources Available in Residential Spaces
My energy harvesting system works by slowly collecting a small amount of energy from a transducer and storing it in a super capacitor. My study focuses primarily on photovoltaic and thermoelectric harvesting due to the relatively high energy density that they provide; however, any energy source can be used provided that it overcomes the minimum sensitivity of the harvesting integrated circuit (IC). The harvesting IC contains a switching converter and voltage regulator to stabilize and boost the volatile voltage from the energy source. The harvesting IC trickle charges two capacitors, a small electrolytic capacitor that supplies bursts of energy to an RF transmission module and a large super capacitor that will power the entire system if the harvesting source becomes unavailable. The required capacitor sizes can be calculated based on the consumption of the loads, type of harvesting source, and transmission frequency to ensure continuous system operation. A low dropout regulator (LDO) provides continuous power to the sensor and an ultra-low-power microcontroller. The microcontroller reads the sensor data and charge status of the capacitors, optimizing the energy usage by minimizing the number of transmission bursts.
Harvester Operation Flow Diagram
The proof-of-concept system I developed is shown. I will continue to refine it, but it successfully harvests energy from photovoltaic and thermoelectric sources and transmits data from an occupancy or temperature sensor at regular intervals. The Zigbee communication protocol is used for transmission, making it easy to implement into existing microgrid and IoT systems. If you are interested in the math, documentation, or want to discuss anything else, please reach out, and I’d love to share more details.
Output Capacitor Expected Response
Energy Harvesting Module Made From Off-the-Shelf Components
Harvesting Module Circuit Diagram