Optimization, Design, and Demonstration of 1 kW Stirling Controller using Capacitor-based Power Factor Correction

Completed TRL 4 (started at 3, targeting 4)

Description

This project will develop a Pareto optimization design script to guide the minimization of the mass and loss of Stirling alternator and controller systems. This project will then design, construct, and demonstrate a 1 kW Stirling controller. The controller design developed in this work will incorporate newly developed polymer multi-layer capacitors which will reduce the required passive power factor correction volume by 50 times compared to the current mil-spec technology. A Phase I SBIR has recently been awarded to proposal Z1.03-5319 to begin the paper design of an alternative kilowatt-class Stirling controller. The SBIR team plans to utilize active power factor correction requiring an FPGA or custom control ASIC, and a separate controller for each Stirling. This proposed work will utilize passive power factor correction facilitating a simple, robust, analog control circuit and allowing the parallel control of multiple Stirlings convertors using a single controller. Comparison of this proposed work with the awarded SBIR will provide a beneficial comparison of the power density, operating efficiency, and development effort afforded by each approach.

The optimization strategy and hardware developed in this work will be part of the government’s reference design for the FSP project and will have a feasible path to NASA TRL 6 coinciding with the schedule of the FSP flight demonstration. The designs and hardware results generated will be available as reference material for FSP and DRPS flight hardware prime contractors. All electronic components, the circuit topology and thermal management (facilitating vacuum testing and operation) will have a path to flight.

Benefits

Sustainable space exploration requires a continuous source of electric power. Free-piston Stirling convertors are valuable tools for thermal to electric power conversion as they are capable of converting heat energy into electricity with 4 times higher efficiency than current thermoelectric RTG systems and have a higher power density than Brayton systems in the 1 to 10 kW power range. Stirling convertors require a controller to maintain stable operation, and recent Stirling alternator and controller designs developed in collaboration with NASA are focused on 80 W specifications for radioisotope systems and utilize complex, active power factor correction. Simplified strategies for power factor correction have been demonstrated (NTR "Stirling Convertor Analog Controller"), but additional work is needed to design the power-dense and efficient 1 kW Stirling electrical systems (Stirling alternator and controller) required for the Fission Surface Power (FSP) project.

Details

Technology area	Aerospace Power and Energy Storage > Power Generation and Energy Conversion > Dynamic Energy Conversion
Program	Center Innovation Fund: GRC CIF (GRC CIF)
Lead organization	Glenn Research Center, Cleveland, OH
Start date	2020-10-01
End date	2021-09-30

Project contacts

Listed on TechPort itself — the most direct way to ask about this specific project.

Christopher B Barth — christopher.b.barth@nasa.gov

How to get involved

This is early/mid-stage (TRL 4) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

None of these are guaranteed paths for this specific project — TechPort itself doesn't have an "apply" button. Reaching out to the contact(s) above with a specific question is usually the fastest way to find out what's actually open.