Modeling and testing of a milliwatt hydrokinetic turbine for pressure energy harvesting

Technologies such as telemetry and remote sensing systems are commonly used to gain information that is not easily obtainable by the researcher. The challenge, however, is that these systems do not have access to an external power supply once deployed in a desolate location. This limits their lifespan to the energy density of an on-board battery and creates a constraint on their sensing capabilities and data resolution. Often times the batteries are not rechargeable and need to be replaced, which is especially difficult and costly for marine telemetry systems, as they are typically encased in epoxy resin to withstand high pressures at depth. Such systems would benefit greatly from energy harvesting. In the marine environment, the great pressures that are experienced at depth provide a vast amount of potential energy that can be harvested. Marine animals equipped with telemetry tags are the perfect candidates as many species make frequent dives while foraging or migrating. This energy can be converted to mechanical and electrical energy with the use of a turbine, which is commonly used for small to large-scale energy production. However, turbines on the scale needed for this application is not readily available. There has been an increase in the research of millimeter-scale turbines for small power generation, but they are usually air or gas powered and few provide an in-depth analysis of the efficiencies of these systems. This thesis focuses on the development and testing of a millimeter-scale hydrokinetic turbine for harvesting energy for marine telemetry tags and like-systems. An analytical model is developed using common turbomachinery concepts and compared to experimental results of a turbine prototype to identify and quantify sources of loss. Each identified loss is thoroughly explained as it is applied to the model and suggested design improvements are discussed. The model is used to make predictions of turbine performance given a higher input pressure for assessment of the viability of this transduction method for the intended application. The model and design presented provides useful information for future exploration of miniature turbine technology for powering remote micro-systems and insight into pressure energy harvesting capabilities