Kelly Trautz

Mobile Solar Power

The militarys need to reduce both fuel and battery resupply is a real-time requirement for increasing combat effectiveness and decreasing vulnerability. Mobile photovoltaics (PV) is a technology that can address these needs by leveraging emerging, flexible space PV technology. In this project, the development and production of a semirigid, lightweight, efficient solar blanket with the ability to mount on, or stow in, a backpack and recharge a high-capacity rechargeable lithium-ion battery was undertaken. The 19% efficient blanket consists of a 10 × 3 solar array of 20 cm2 and single-junction epitaxial lift-off solar cells, which have an efficiency of ∼22% under AM1.5G illumination. A power-conditioning module was also developed to interface the solar panel to the battery. Thirteen systems were outfitted during a Limited Objective Experiment-1 in February 2012, and based on the results, a second version of the system is in development.

High band gap solar cells for underwater Photovoltaic applications

The use of autonomous systems to provide situational awareness and long-term environment monitoring is increasing. Photovoltaics (PV) has been favored as a long-endurance power source for many of these applications. To date the use of PV has been limited to space and terrestrial (dry land) installations. The need for an extended power source also exists for underwater (UW) systems, which currently rely on surface PV arrays or batteries. In this paper we demonstrate that high band gap InGaP solar cells can provide useful power underwater.

Initial results from Primary Arc effects on solar cells at LEO (PASCAL) flight experiment

Repeated low power, or primary arcing, may adversely affect the performance of space solar cells. The cumulative effects of primary arcing on common solar cell performance parameters has been the subject of numerous ground studies in simulated plasma environments. The Primary Arc effects on Solar Cells At LEO (PASCAL) flight experiment is presently active aboard in the International Space Station (ISS) and characterizing such effects in-orbit for numerous state-of-the-art space solar cells with initial results presented herein.

High efficiency flexible solar panels

The militarys need to reduce both fuel and battery resupply is a real time requirement for increasing combat effectiveness and decreasing vulnerability. Mobile photovoltaics (PV) are a technology that can address these needs by leveraging emerging, flexible space photovoltaic technology. In this ongoing project, the development and production of a semi-rigid, lightweight, efficient solar blanket with the ability to mount on, or stow in, a backpack and recharge a warfighters battery was undertaken. The blanket consists of a 10 × 3 solar array of 20 cm2 epitaxial lift-off (ELO) solar cells. In the first two phases of the project, single-junction cells with an efficiency of ~21% under AM1.5G illumination were used. Several of these systems were outfitted during Limited Objective Experiments (LOE) in February 2012 and August 2012. In the third and most current phase of this project, the panels will be made from IMM triple-junction cells with an efficiency of 28-30% under AM1.5G illumination. The results of laboratory tests of the new prototypes, as well as a test plan and expected outcome for a field experiment are presented here.

Selected on-orbit data from the FTSCE II aboard the MISSE 7 testbed

The 2nd Forward Technology Solar Cell Experiment (FTSCE II) that flew as part of the 7th Materials on the International Space Station Experiments (MISSE 7) successfully flew on orbit for 18 months from 23 November 2009 to 20 May 2011. The Air Force Research Laboratory Space Vehicles Directorate in collaboration with the Naval Research Laboratory flew a myriad of experiments to evaluate advanced photovoltaic technologies. Such data is critical for technology development and future transition to operational use. Applications of the data include validating ground test protocols and assessing LEO environmental effects (atomic oxygen, ultraviolet radiation, thermal cycling, etc.). In addition to reducing risk to future spacecraft, research and development risks are reduced through early technology assessment for space operation. These experiments were comprised of triple-junction production as well as advanced inverted metamorphic (IMM) and other thin film III-V cells from multiple vendors. In addition to the III-V based devices an experiment was included to evaluate advanced amorphous silicon concepts. The methodology and analysis of the on-orbit data collected during the mission is presented here.

A Langmuir probe diagnostic for time-of-flight measurements of transient plasmas produced by high-energy laser ablation

We discuss here the development of a Langmuir probe (LP) diagnostic to examine high-density, high-temperature inhomogeneous plasmas such as those that can be created at the University of Rochesters Laboratory for Laser Energetics OMEGA facility. We have configured our diagnostic to examine the velocity of the plasma expanding from the target. We observe velocities of approximately 16-17 cm/μs, with individual LP currents displaying complex structures, perhaps due to the multiple atomic species and ionization states that exist.

Nuclear weapons effects testing of solar cells using the National Ignition Facility (NIF)

The response of triple junction InGaP2/GaAs/Ge, solar cells to a simulated nuclear weapons threat environment is being analyzed and tested. A series of experiments exposing solar cells to a pulse x-ray source were conducted at the newly opened National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) and the OMEGA Laser facility at the University of Rochester. The test samples were 2-cm × 2-cm solar cells mounted on solar array substrates using materials and techniques identical to flight solar arrays. The cell structural response is characterized through visual inspections for exposure-induced cracking. The cell electrical response is characterized through current vs. voltage measurements made under simulated Air Mass Zero As a result of this project, a methodology will be established through which a comprehensive analysis of the weapons response of new solar cell technologies can be performed.

Low energy proton implantation techniques for coverglass irradiation qualification

It is demonstrated that the two hydrogen concentration profiles and the associated effects on solar cell coverglass degradation created at equivalent atomic fluences of 7.4×10¹⁵ particles/cm² using 30 keV proton (H⁺) and 60 keV diatomic hydrogen ion (H<inf>2</inf>⁺) implantation on solar cell coverglass material are nearly identical. Both Monte Carlo simulation and experimental results support this contention to the level of acceptable experimental error, thereby enabling coverglass radiation testing to be performed using the latter, more cost effective option.

Flexible luminescent solar concentrators utilizing bio-derived tandem fluorophores

In this work we aim to investigate flexible luminescent solar concentrators (LSCs) for the purpose of portable power generation. We will focus on Surelight® PE-610, which is a tandem fluorophore consisting of R-Phycoerythrin and Rhodamine, as well as PbSe nanorods, as the luminescent species. The luminescent quantum yield, LQY, of PE-610 was measured as 53% in buffer solution, and 75% when deposited in a thin-film. Computational simulations show that a 25cm by 25cm LSC with a 0.1mm thick thin-film containing PbSe nanorods, a LQY of 70% and a substrate thickness of 3mm has an optical efficiency of 4.5±0.1%. An identical LSC with a 0.5mm thick substrate had an optical efficiency of 1.7±0.1% meaning substrate thickness is a key factor for flexible LSCs. A primary advantage of PE-610 as a LSC material is that it is bio-derived, and therefore cheap and abundant. The PbSe nanorods have the advantage of a broad absorption spectrum, though the LQY used is still speculative at this time.

Monte Carlo analysis of the NEO Beam electron beam facility

MCNPX Monte Carlo electron transport analyses are used to characterize the electron beam facility at NEO Beam.