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In this study, we identify and survey energy harvesting technologies for small electrically powered unmanned systems designed for long-term (>1 day) time-on-station missions. An environmental energy harvesting scheme will provide long-term, energy additions to the on-board energy source. We have identified four technologies that cover a broad array of available energy sources: solar, kinetic (wind) flow, autophagous structure-power (both combustible and metal air-battery systems) and electromagnetic (EM) energy scavenging. We present existing conceptual designs, critical system components, performance, constraints and state-of-readiness for each technology. We have concluded that the solar and autophagous technologies are relatively matured for small-scale applications and are capable of moderate power output levels (>1 W). We have identified key components and possible multifunctionalities in each technology. The kinetic flow and EM energy scavenging technologies will require more in-depth study before they can be considered for implementation. We have also realized that all of the harvesting systems require design and integration of various electrical, mechanical and chemical components, which will require modeling and optimization using hybrid mechatronics-circuit simulation tools. This study provides a starting point for detailed investigation into the proposed technologies for unmanned system applications under current development.

The Hawk pulsed power generator is used in plasma opening tch (POS) experiments in the 1-1s conduction time regime to study g conduction time switch physics. Experiments reported here lude modiflmg the POS electrode geometry, injecting plasma into e-beam diode, using gas gun plasma sources (with H2, He, and Ar ,es), and using a helical cathode center conductor in the switch ion to increase the total insulating magnetic field. Tapering the hode center conductor over the 8 cm POS length from 10 cm to, ically, a 2.5 cm diam produced peak load powers of 0.7 TW with kJ delivered to the diode--20% energy efficiency--with carbonrted flashboards as the plasma source. Performance (voltage, Mer generated) with a straight 10 cm diam cathode deteriorated en the POS anode outer conductor just downstream of the switch s extended toward the load at the same radius as the switch. Load Mer was up to 70% higher with a plasma-filled diode (PFD) used in ljunction with the POS for short POS conduction times (400 ns and j). Use of a helical center conductor resulted in dramatically;faded switch performance for >350 ns conduction times. Switch formance with gas guns was generally comparable to that with ihboards in a given switcMoad configuration and was independent ;he gas (H2, He, and Ar) used.