Description: Nirvana Energy Systems (NES) has pioneered and is commercializing an innovative ThermoAcoustic Power Stick (TAPS) partially based on technology developed by Xerox Palo Alto Research Center (PARC) and NASA. NES has demonstrated and is building a 1kWe TAPS for use in remote power applications where reliability for 20+ years is of paramount importance. The novel TAPS technology has no hot moving parts and incorporates well proven, reliable linear motors and alternators in an engine based on the Stirling cycle. NES has designed, optimized, built and tested all sub-systems for reliability, ease of manufacturing and cost reduction over currently available Stirling engines. The 1kWe TAPS formed the starting design for scaling down to a ~300 W tunable power thermoacoustic device. The system is insensitive to radioisotope heat degradation, capable of 10+ years continuous operation, inexpensive to manufacture using well established methods, and yields greater than 25% thermal to electrical efficiency all while being designed for a specific power greater than 30 W/kg. The NES Thermoacoustic Radioisotope Generator (TRG) represents the ultimate in remote power devices and is the next step toward reliable dynamic power conversion for space. The technical objectives of the NES TRG Phase II effort are to produce a prototype TRG convertor, build a test cell, and validate the designed system performance with a minimum of 500 hours of steady state operation. During this 18 month effort, the TRG design will undergo any final modifications based on NASA review. Test support hardware will be selected and designed. The prototype and test cell will be manufactured to exact specifications. A risk assessment will be conducted for the convertor. Subsystem and materials coupon tests will be conducted. The TRG system will be assembled and tested for a minimum of 500 hours.

Benefits: The primary goal of the proposed project is to develop a thermal-to-electrical power conversion system that achieves 100-500 W of net electrical output, has >25% efficiency, and durability for life greater than 10 years in response to the SBIR S3.01 call from NASA. Due to the significant manufacturing and assembly cost reductions afforded by the TAPS architecture over traditional Free Piston Stirling (FPS) systems, the TAPS solution could be used as a direct replacement over traditional thermoelectric or other Stirling based systems in space missions. Furthermore, the TAPS technology enables architectures that are difficult, or impossible, with other systems. Specifically, TAPS can easily be utilized for a combined power and cooling duplex, and some preliminary designs have been created. Such systems would enable a sustained presence in extreme planetary environments such as the surface of Venus. This can be achieved using radioisotope heating for long term missions or chemical heating for shorter duration missions.

Nirvana Energy Systems is currently working to commercialize the NASA technology through an exclusive patent license granted for the Alpha-STREAM technology that the TAPS technology is partially based on. The NES TAPS technology could be easily adapted to home use where high efficiencies are possible and the unit would function as a micro-Combined Heating and Power system. In an installation such as this, the TAPS unit could be natural gas fed where to achieve overall high system efficiencies the unit would utilize excess heat to provide heated water for potable needs or for hydroponic heating. Excess electrical energy production would be sent to the grid. Similar to application for home power generation, other applications include commercial businesses, military uses (manned/unmanned vehicles and domesticated areas), and the transportation industry. In particular, these industries desire higher electrical outputs and the validity of the TAPS architecture afforded by this Phase I effort would offer strong evidence in the scale-ability of the technology. Moreover, the reverse cycle of the TAPS system can be used for cooling in many cases, including as a refrigerant free domestic cooling system.