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Zurich, Switzerland

Wojtas N.,ETH Zurich | Ruthemann L.,ETH Zurich | Glatz W.,greenTEG | Hierold C.,ETH Zurich
Renewable Energy | Year: 2013

There is a significant push to increase the output power of thermoelectric generators (TEGs) in order to make them more competitive energy harvesters. The thermal coupling of TEGs has a major impact on the effective temperature gradient across the generator and therefore the power output achieved. The application of micro fluidic heat transfer systems (μHTS) can significantly reduce the thermal contact resistance and thus enhance the TEG's performance. This paper reports on the characterization and optimization of a μTEG integrated with a two layer μHTS. The main advantage of the presented system is the combination of very low heat transfer resistances with small pumping powers in a compact volume. The influence of the most relevant system parameters, i.e. microchannel width, applied flow rate and the μTEG thickness on the system's net output performance are investigated. The dimensions of the μHTS/μTEG system can be optimized for specific temperature application ranges, and the maximum net power can be tracked by adjusting the heat transfer resistance during operation. A system net output power of 126mW/cm2 was achieved with a module ZT of 0.1 at a fluid flow rate of 0.07l/min and an applied temperature difference of 95K.It was concluded that for systems with good thermal coupling, the thermoelectric material optimization should focus more on the power factor than on the figure of merit ZT itself, since the influence of the thermal resistance of the TE material is negligible. © 2013 Elsevier Ltd. Source

Wojtas N.,ETH Zurich | Grab M.,ETH Zurich | Glatz W.,greenTEG | Hierold C.,ETH Zurich
Journal of Electronic Materials | Year: 2013

This study presents modeling and experimental results of micro thermoelectric generators (μTEGs) integrated into a multilayer micro heat exchange system. The multilayer configuration benefits from low heat transfer resistances at small fluid flow rates and at the same time from low required pumping powers. The compact stacked power device allows for high net output power per volume, and therefore a reduction in size, weight, and cost compared with conventional large-scale heat exchangers. The influence of the boundary conditions and the system design parameters on the net output power of the micro heat exchange system was investigated by simulation. The theoretical results showed a major impact of the microchannel dimensions and the μTEG thickness on the overall output performance of the system. By adapting the applied fluid flow rate, the system's net power output can be maximized for varying operating temperatures. Experimental measurements of the cross-flow micro heat exchange system were in good agreement with the performed simulations. A net μTEG output power of 62.9 mW/cm2 was measured for a double-layer system at an applied water inlet temperature difference of 60 K with a Bi 2Te3 μTEG (ZT of 0.12), resulting in a net volumetric efficiency factor of 37.2 W/m3/K2. © 2013 TMS. Source

greenTEG | Date: 2013-12-23

A heat flow sensor (WFS) and use thereof, which heat flow sensor should have the lowest possible invasiveness and nevertheless is robust enough to satisfy the requirements of individual applications. For this purpose, the heat flow sensor includes an active sensor element, which is provided with a highly thermally conductive heat-conducting element (

greenTEG | Date: 2010-10-25

Scientific and monitoring apparatus, namely, heat exchanger, heat flux sensor, thermoelectric converter; apparatus and instruments for conducting, transforming, regulating or controlling electricity, namely, electronic devices for generating electrical power from heat or water, thermoelectric heat pump and heat flux sensor, in International Class 9. Treatment of materials, namely, metal coating, deposition of semiconductor material by electrochemical deposition, in International Class 40. Scientific and technological services and research and design relating thereto; consultancy in connection with technology; industrial analysis and research services in International Class 42.

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