Low Temperature Waste Heat to Electric Energy using Micro-Stirling Clusters – MISTIC

A Stirling engine was built at the SYMME laboratory. This centimeter scale machine presents the same features as for the future micro-engine: multiphase Stirling, membranes, low temperature operation.
The developed models can then be compared and validated using the experimental measurements from the instrumented macro-engine.

A design tool based on an equivalent electric network analogy has been proposed and validated with respects to experimental results.
For millimeter scale hybrid membranes, tests are in progress. They aim at checking the dedicated fluid/structure models as well as developing and improving their assembly and filling process.
The immersion assembly approach of two half structures is successfully demonstrated. The critical effect of the sealing and tension has been pointed out for planar kapton® thin film membrane without planar spring.

Because of the dimension of the anticipated micro-engine, the addition of a full instrumentation is not realistic and may kill the machine itself. Though, instrumentation is a key factor for understanding and optimization for thermal machines. As a conclusion, a millimeter scale Stirling purposefully designed for instrumentation will be built. Its architecture is relevant regarding the micro-engine for which the obtained results would be extended.

F. Formosa, A. Badel, J. Lottin, “Equivalent electrical network model approach applied to a double acting low temperature differential Stirling engine” Energy Conversion and Management, submitted 05/28/2013

The project aims at developing enabling technology for waste heat recovery in industrial processes. Their overall efficiency could be improved by converting the waste heat into electricity. The chosen plan consists of implementing clusters of miniature thermodynamic Stirling machines.

The core technology is a multiphase piezoelectric smart membrane Stirling engine. It is fabricated using mass production: MEMS machining, assembling and thin film technology. Expected performances allow large fraction of electric energy to be extracted from the low temperature waste heat. The relevance of Stirling cycle for a microminiaturized generator has been demonstrated and basic underlying technologies for its fabrication are available through the project partners’ facilities and capacities.

This 42 months work program aims at demonstrating operation and defining opportunity of waste heat recovery using MIcro-STIrling Clusters (MISTIC). The activities will be centered on the development of micro-Stirling generators test prototypes and will include theoretical and experimental analysis of thermal, structural, and fluidic behavior. The partners of the project: SYMME lab. of the Université de Savoie, FEMTO-ST and the international CNRS/UMI-LN2 lab. have demonstrated the required skills and knowledge to complete the work and achieve the objectives. The project will also benefit from the expertise of department of Mechanical Engineering of McGill University especially for MEMS process, modeling and characterization.

Requiring a multidisciplinary strategy, the tasks specifically include: 1) The development of thermal isolation frames for micro-devices; 2) The development and characterization of smart membrane structures; 3) The Stirling regenerator optimization; 4) The demonstration of the operation of multiphase micro-Stirling generator; 5) The analysis and selection of industrial applications opportunities.
Thus, this project will result in important advances in applied thermal and Power MEMS and heat transfer modeling and optimization.