Heating Water with Wind or Hydro Power: Direct Conversion of Mechanical Energy to Heat Using Eddy Currents

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Date

2015-05

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The Ohio State University

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Abstract

On average in the United States, approximately 18% of total residential energy consumption is for heating water. Current methods for heating water, involving electrical resistive heaters and natural gas heaters, are inefficient and depend upon the burning of fossil fuels which release greenhouse gases. This proposal discusses a novel way to heat water, known as an eddy current water heater (ECWH), by directly converting the mechanical energy of a rotating disk (e.g. driven by a wind or water turbine), in a fixed magnetic field, into heat by using eddy currents. Electrical eddy currents are induced in any conductor moving in a magnetic field in accordance with Faraday’s law. If these eddy currents are not extracted from the disk, the currents will dissipate as heat. The goal of this research is to gain a better understanding of the physical relationships in a laboratory scale model to enable practical eddy current water heating systems to be developed. The relationships between the disc’s angular velocity, the permanent magnets field strength, and the resulting resistive torque are investigated using an eddy current dynamometer. Data were collected on these three variables in order to evaluate the accuracy of current theoretical models as well as to establish the relevant non-dimensional groupings to allow for scaling from a model to a prototype. A non-dimensional parameter of significance has been found, which can be used to scale the laboratory scale model to a prototype for residential use. Furthermore, it is shown that current theoretical models do not reliably predict power dissipation and resistive torque. Thus current theoretical models could be improved as they consider simpler disk to magnet geometries and lower speeds than may be required for a practical ECWH design. The results presented here underscore the need for further study of how eddy currents form and flow in a given ECWH design, specifically the skin effect and the paths of the eddy currents outside the magnet area.

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This thesis was awarded second place in the Engineering category at the Denman Forum

Keywords

Eddy Currents, Energy Conversion, Sustainability, Water, Wind Power, Energy Efficiency

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