Thermoelectric Device Fabrication Using Thermal Spray and Laser Micromachining
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Mahder Tewolde, Gaosheng Fu, David J. Hwang, Lei Zuo, Sanjay Sampath, and Jon P. Longtin (Submitted July 9, 2015; in revised form October 20, 2015) Thermoelectric generators (TEGs) are solid-state devices that convert heat directly into electricity. They are used in many engineering applications such as vehicle and industrial waste-heat recovery systems to provide electrical power, improve operating efficiency and reduce costs. State-of-art TEG manufacturing is based on prefabricated materials and a labor-intensive process involving soldering, epoxy bonding, and mechanical clamping for assembly. This reduces their durability and raises costs. Additive manufacturing technologies, such as thermal spray, present opportunities to overcome these challenges. In this work, TEGs have been fabricated for the first time using thermal spray technology and laser micromachining. The TEGs are fabricated directly onto engineering component surfaces. First, current fabrication techniques of TEGs are presented. Next, the steps required to fabricate a thermal spray-based TEG module, including the formation of the metallic interconnect layers and the thermoelectric legs are presented. A technique for bridging the air gap between two adjacent thermoelectric elements for the top layer using a sacrificial filler material is also demonstrated. A flat 50.8 mm 3 50.8 mm TEG module is fabricated using this method and its performance is experimentally characterized and found to be in agreement with expected values of open-circuit voltage based on the materials used.
Keywords
additive manufacturing (AM), laser micromachining, thermal spray, thermoelectric generators (TEGs), thermoelectric power generation, wasteheat energy harvesting
1. Introduction Thermoelectric devices offer unique power generation solutions for waste-heat energy harvesting. They are small, quiet, and have no moving parts, which makes them well suited for a variety of engineering applications, including electricity production from vehicle waste-heat to improve fuel economy in vehicles (Ref 1-3), and industrial wasteheat recovery to power wireless sensors and networks to communicate with and collect data from engineering systems (Ref 4-6). Commercially available TEGs, however, are flat, inflexible and are available in only limited range of sizes. Efforts to incorporate them onto components with curved surfaces such as exhaust pipes, pump housings, steam lines, mixing containers, reaction chambers, etc., require custom-built heat exchangers. This adds cost and is labor-intensive, in addition to presenting challenges Mahder Tewolde, Gaosheng Fu, David J. Hwang, and Jon P. Longtin, Department of Mechanical Engineering, Center for Thermal Spray Research, Stony Brook University, Stony Brook, NY 11794; Sanjay Sampath, Department of Materials Science and Engineering, Center for Thermal Spray Research, Stony Brook University, Stony Brook, NY 11794; and Lei Zuo, Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA 24061. Contact e-mail: Jon.Longtin@ stonybrook.edu.
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