This PDF file contains the front matter associated with SPIE Proceedings Volume 9115, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

Japan Atomic Energy Agency (JAEA) together with Japan Aerospace Exploration Agency (JAXA) has developed an insitu evaluation technique for understanding radiation response of space solar cells, by which the electrical characteristics of solar cells can be measured under AM0 light illumination during proton/electron irradiation experiments (Simultaneous method). Using the simultaneous method, we revealed the radiation degradation of multi-junction solar cells such as InGaP/GaAs/Ge triple junction (3J) solar cells. A modeling of the radiation degradation of 3J solar cells based on the Non-Ionizing Energy Loss (NIEL) concept was established. Flexible multi-junction solar cells are under development for space applications.

A tantalum tungsten solid solution alloy, Ta 3% W, based 2D photonic crystal (PhC) was designed and fabricated for high-temperature energy conversion applications. Ta 3% W presents advantages compared to the non-alloys as it combines the better high-temperature thermomechanical properties of W with the more compliant material properties of Ta, allowing for a direct system integration path of the PhC as selective emitter/absorber into a spectrum of energy conversion systems. Indeed metallic PhCs are promising as high performance selective thermal emitters for thermophotovoltaics (TPV), solar thermal, and solar TPV applications due to the ability to tune their spectral properties and achieve highly selective emission. A 2D PhC was designed to have high spectral selectivity matched to the bandgap of a TPV cell using numerical simulations and fabricated using standard semiconductor processes. The emittance of the Ta 3% WPhC was obtained from near-normal reectance measurements at room temperature before and after annealing at 1200 °C for 24h in vacuum with a protective coating of 40 nm HfO₂, showing high selectivity in agreement with simulations. SEM images of the cross section of the PhC prepared by FIB confirm the structural stability of the PhC after anneal, i.e. the coating effectively prevented structural degradation due to surface diffusion. The mechanical and thermal stability of the substrate was characterized as well as the optical properties of the fabricated PhC. To evaluate the performance of the selective emitters, the spectral selectivity and useful emitted power density are calculated as a function of operating temperature. At 1200 °C, the useful emitted irradiance is selectively increased by a factor of 3 using the selective emitter as compared to the non-structured surface. All in all, this paper demonstrates the suitability of 2D PhCs fabricated on polycrystalline Ta-W substrates with an HfO₂ coating for TPV applications.

To improve the thermal-to-electrical conversion efficiency of waste exhaust heat at temperatures in the vicinity of 750°C, RTI has combined two different high-performance materials to form a high ZT, hybrid thermoelectric (TE) device. Recently-developed enhanced “TAGS-85”, or e-TAGS, was employed as the p-leg, while the n leg was comprised of improved half-Heusler (HH) material. This hybrid material pair provides a high ZT, lead-free TE material solution for exhaust gas heat recovery for use in vehicle or industrial platforms. The improved HH material employs two novel techniques to reduce thermal conductivity: (1) high-energy milling, and (2) addition of coherent inclusions. Single n-/pcouples were produced that achieved a 9.2% efficiency with a power output of 205mW for T_hot = 559°C and ΔT = 523K. This is a significant efficiency improvement at a lower hot side temperature with the hybrid e-TAGS/HH single couple over the performance of a conventional, all HH couple. By optimizing the cross sectional areas of the pellets for equal heat flow, the resulting asymmetric couple achieved 10.5% efficiency with a maximum power output of 317 mW at T_hot = 537°C and ΔT = 497°C. A 49-couple hybrid module using other advanced HH materials paired with e-TAGS and operated with T_hot up to 600°C reached a maximum efficiency of 10%. The improved module efficiency is believed to be due to both improved materials and optimized cross-sectional area ratios between the n- and p- elements.

There is going on a flurry of research activity in the development of effcient energy harvesters from all branches of energy conversion. The need for developing self-powered wireless sensors and actuators to be employed in unmanned combat vehicles also seems to grow steadily. These vehicles are inducted into perilous war zones for silent watch missions. Energy management is sometimes carried out using misson-aware energy expenditure strategies. Also, when there is a requirement for constant monitoring of events, the sensors and the subsystems of combat vehicles require energy harvesters that can operate over a discrete set of spot frequencies. This paper attempts to review some of the recent techniques and the energy harvesting devices based on electromagnetic and electromechanical principles. In particular, we shall discuss the design and performance of a MEMS-harvester that exhibits multiple resonances. Frequency response of a simulated electromagnetic harvester is plotted. It has three dominant peaks at three different resonant frequencies. Variation in the load power in the normalized units as a function of load is found, which determines the matched load resistance.

A novel class of piezoelectric-based energy harvesting devices with integrated safety and firing setback event detection electronics and logic circuitry that can be used in gun-fired munitions is presented. In this paper, the application of the device to the development of initiators for thermal reserve batteries in gun-fire munitions is presented. The novel and highly efficient electrical energy collection and storage and event detection and safety electronics used allows the use of a very small piezoelectric element. As a result, such devices can be highly miniaturized for used in small reserve batteries. For thermal battery initiation, when the prescribed firing setback acceleration profile, i.e., the prescribed all-fire condition is detected, a highly efficient charge collection electronic circuitry routes the charges generated by the piezoelectric element of the device to the initiator bridge element, thereby causing the thermal battery pyrotechnic material to be ignited. For munitions powered by thermal reserve batteries, the present initiation device provides a self-powered initiator with full no-fire safety circuitry for protection against accidental drops, transportation vibration, and other similar low amplitude accelerations and/or high amplitude but short duration acceleration events. The device is shown to be readily set to initiate thermal batteries under almost any all-fire conditions. The device can be readily hardened to withstand very high G firing setback accelerations in excess of 100,000 G and the harsh firing environment. The design of prototypes and testing under realistic conditions are presented.

Physical Optics Corporation (POC) developed the body-worn Integrated Soldier Power and Data System (ISPDS), a configurable node for plug-in wired or wireless server/client or peer-to-peer computing with accommodations for power, sensor I/O interfaces, and energy harvesting. The enabling technology increases the efficacy of uniformed personnel and first responders and provides an option for reducing force structure associated with the need for hardware network infrastructure to enable a mobile digital communications architecture for dismounted troops. The ISPDS system addresses the DoD’s need for an “intelligent” power control system in an effort to increase mission duration and maximize the first responders and warfighter’s effectiveness without concern for the available energy resources (i.e., batteries). ISPDS maximizes durability and survivability, assesses influences that affect performance, and provides the network backbone and mobile node hardware. POC is producing two vest-integrated variants, one each for the U.S. Army PEO Ground Soldier and the Air Soldier, with each including state-of-the-art low-profile and robust wearable connectors, cabling, and harnesses, and an integrated low-profile power manager and conformal battery for data and power distribution. The innovative intelligent power controller (IPC), in the form of the ISPDS firmware and power sensing and control electronics, will enable ISPDS to optimize power levels both automatically and in accordance with manually set preferences. The IPC module is power dense and efficient, and adaptively provides lossless transfer of available harvested photovoltaic energy to the battery. The integrated systems were tested for suitable electrical, electromagnetic interference (EMI), and environmental performance as outlined in military standards such as MIL-STD- 810G and MIL STD-461F.

Efficient photovoltaic energy harvesting requires device structures capable of absorbing a wide spectrum of incident radiation and extracting the photogenerated carriers at high voltages. In this paper, we review the impact of active layer thickness on the voltage performance of GaAs-based photovoltaic device structures. We observe that thin absorber structures can be leveraged to increase the operating voltage of energy harvesting devices. Thin absorbers in combination with advanced light trapping structures provide an exciting pathway for enhancing the performance of flexible, lightweight photovoltaic modules suitable for mobile and portable power applications.

Over 2.5 billion people do not have access to safe and effective sanitation. Without a sanitary sewer infrastructure, self-contained modular systems can provide solutions for these people in the developing world and remote areas. Our team is building a better toilet that processes human waste into burnable fuel and disinfects the liquid waste. The toilet employs energy harvesting to produce electricity and does not require external electrical power or consumable materials. RTI has partnered with Colorado State University, Duke University, and Roca Sanitario under a Bill and Melinda Gates Foundation Reinvent the Toilet Challenge (RTTC) grant to develop an advanced stand-alone, self-sufficient toilet to effectively process solid and liquid waste. The system operates through the following steps: 1) Solid-liquid separation, 2) Solid waste drying and sizing, 3) Solid waste combustion, and 4) Liquid waste disinfection. Thermoelectric energy harvesting is a key component to the system and provides the electric power for autonomous operation. A portion of the exhaust heat is captured through finned heat-sinks and converted to electricity by thermoelectric (TE) devices to provide power for the electrochemical treatment of the liquid waste, pumps, blowers, combustion ignition, and controls.

Recent years have witnessed an explosion of interest and research endeavor in lithium-ion batteries to enable vehicle electrification. In particular, a critical imperative is to accelerate innovation for improved performance, life and safety of lithium-ion batteries for electric drive vehicles. Lithium ion batteries are complex, dynamical systems which include a multitude of coupled physicochemical processes encompassing electronic/ionic/diffusive transport in solid/electrolyte phases, electrochemical and phase change reactions and diffusion induced stress generation in multi-scale porous electrode microstructures. While innovations in nanomaterials and nanostructures have spurred the recent advancements, fundamental understanding of the electrode processing – microstructure – performance interplay is of paramount importance. In this presentation, mesoscale physicochemical interactions in lithium-ion battery electrodes will be elucidated.

A tritium-based indirect converting photovoltaic (PV) power source has been designed and prototyped as a long-lived (~15 years) power source for sensor networks. Tritium is a biologically benign beta emitter and low-cost isotope acquired from commercial vendors for this purpose. The power source combines tritium encapsulated with a radioluminescent phosphor coupled to a commercial PV cell. The tritium, phosphor, and PV components are packaged inside a BA5590-style military-model enclosure. The package has been approved by the nuclear regulatory commission (NRC) for use by DOD. The power source is designed to produce 100μW electrical power for an unattended radiation sensor (scintillator and avalanche photodiode) that can detect a 20 μCi source of ¹³⁷Cs at three meters. This beta emitting indirect photon conversion design is presented as step towards the development of practical, logistically acceptable, lowcost long-lived compact power sources for unattended sensor applications in battlefield awareness and environmental detection.

This paper studies the coupling between stress and open circuit voltage in a commercial lithium-ion pouch cell. This coupling is characterized through measurements of a coupling factor, which is defined as the rate of change in voltage with respect to applied mechanical stress. Based on a simple thermodynamic model, this coupling factor is expected to be related to the expansion characteristics of the pouch cell during charging. The expansion characteristics of the pouch cell are compared with measurements of the coupling factors at different states of charge, and are found to be in agreement with the simple thermodynamic model. This work opens the door for the development of mechanical force sensors based on intercalation materials.

Gel electrolyte based on 1M LiPF₆ in ethylene carbonate:dimethyl carbonate, polyethyleneglycol diacrylate oligomer, and 2,2′-azobis(2-methylpropionitrile) is infiltrated into porous sintered LiCoO₂ electrodes and cured in situ. The associated batteries function well, which is consistent with microscopy observations indicating that the gel electrolyte penetrates the electrode well and wets to the electrode particles. Trimethyl silyl acrylate is used to functionalize glass substrates and will cross link with polyethyleneglycol diacrylate during curing to promote bonding between the substrate and the gel electrolyte. The functionalization can localize adhesion allowing the electrolyte to easily release from unfunctionalized glass, which can be used as a mold.

The most significant advantage of double layer supercapacitors over batteries is their ability of being almost continuously charged and discharged without degradation. This is why batteries and supercapacitors are complementary to each other. The supercapacitors can supply power to the system when there are surges or energy bursts relying on their fast charge/discharge ability while the batteries can supply the bulk energy since they can store and deliver larger amount of energy over a longer period of time resulting in a higher discharge capacitance. With the introduction of new electrodes, super-capacitors will provide higher energy densities and charge rapidly with longer lifetimes, relying on the addition of pseudo-capacitance as well as higher surface areas. Pseudo-capacitance is achieved by the use of metal-oxides yielding faradaic reactions over redox couples. Capacitive charge-storage properties of mesoporous films made of complex metal-oxides preferably in core + shell architecture are superior to those of nonporous crystalline metal-oxides. RuO₂ yields the highest energy densities however is not attractive for commercial use due to high cost. Other promising candidates are MnO₂, Co₂O₃, NiO, etc. which need to be improved for achievement of long-term stability. Additionally, the type of electrolyte is important in terms of supercapacitor’s performance and thus, needs to be optimized considering the characteristics of the employed electrode material. This work describes the fabrication and performance of mesoporous double oxides (MnCu, MnNi, MnCo) in aqueous electrolytes. Thin films are deposited by sputtering technique on graphite foils. Specific capacitance, energy and power densities are calculated and the role of electrolyte on electrode performance is discussed.

This paper presents a new nanofiber photovoltaic cell with ITO/ZnO/ITO concentric core designed to have high efficiency of solar energy conversion. The high energy bandgap of ZnO relative to ITO creates quantum wells for effective charge transfer of photogenerated carries from the ZnO active region, and the higher refractive index of the ZnO relative to the ITO enables solar radiation, incident on the ITO inner and outer cores, to couple to the ZnO resulting in effective separation of the optical signal path and the drift current. At the highest fill factor of 0.941, the proposed fiber produces 0.654V as an open-circuit voltage with fiber length of 1mm; where the solar cell could operate at maximum power point of P_mp =0.24mW at V_mp =0.5722V and I_mp =0.0.415mA. The cell voltage and current are dependent on fiber length and area where the highest open-circuit voltage recorded at 0.9317V and the highest shortcircuits current recorded at 0.4379A for fiber length of 1μm with power of 0.408W.

Streaming Process for Electrode-less Electrochemical Deposition (SPEED) method is used to create complex thin-film structures, such as KBNNO, in a single step, in contrast to hydrothermal approaches with separate nanoparticle growth and deposition processes. This new ferroelectric oxide [KNbO₃]_1-x[BaNi_1/2Nb_1/2O _3-δ]_x or “KBNNO” has an alloy-tunable band gap as low as 1.1 eV, so that its absorption can be tailored to match the solar spectrum. At the same time, it has a reasonably large polarization allowing for charge separation across the bulk, sizeable photocurrents, and open-circuit voltages V_oc that exceed the band gap, potentially leading to efficiencies that exceed those possible for standard pnjunction cells. Physical characterization of KBNNO films demonstrate the microstructure and stoichiometry of SPEEDproduced thin-films, ratio of elements needed to achieve an ideal band gap of ~1.39 eV, the effect on film chemistry, microstructure, and band gap of annealing, the practical separation of excited carriers at room temperature, the maximum achievable polarization and its temperature dependence, and the conditions for ideal poling. Photovoltaic characterization of KBNNO cells will determine the efficiency, the relative strengths of dark and photo currents, the open circuit voltage, the short circuit current, and cell fill factor (FF).

A study of solar cells took place by using Lambert W function based diode model. All calculations were made through computer algebra, having the software Maple a special place. Current vs. Voltage graph corresponding to cells was obtained as a main result, so as diode’s parameters values such as the series, shunt resistances and its constant. Analytical results will be useful for cell manufacturing, either for home or industrial usage. As a future research line, Lambert W function utilization is suggested as a mean for multi-diode systems development.

Military based sensor systems are often hindered in operational deployment and/or other capabilities due to limitations in their energy storage elements. Typically operating from lithium based batteries, there is a finite amount of stored energy which the sensor can use to collect and transmit data. As a result, the sensors have reduced sensing and transmission rates. However, coupled with the latest advancements in energy harvesting, these sensors could potentially operate at standard sensing and transition rates as well as dramatically extend lifetimes. Working with the magnetostrictive material Galfenol, we demonstrate the production of enough energy to supplement and recharge a solid state battery thereby overcoming the deficiencies faced by unattended sensors. As with any vibration-based energy harvester, this solution produces an alternating current which needs to be rectified and boosted to a level conducive to recharge the storage element. This paper presents a power converter capable of efficiently converting an ultra-low AC voltage to a solid state charging voltage of 4.1VDC. While we are working with Galfenol transducers as our energy source, this converter may also be applied with any AC producing energy harvester, particularly at operating levels less than 2mW and 200mVAC.

In solar vehicle competition, the available space for installation of the solar panel in the car is limited. In order to optimize space, it is difficult not to install solar modules in areas impacted by shadows, even if they cause reduction of efficiency in the overall photoelectric generation. Shadow patterns arise from the relative position of the sun to the earth, and the relative position of the vehicle towards both of them. Since vehicle, earth and sun are moving in semi-predictable patterns, computer simulations can cross and match data from such sources to forecast generation behavior. The outputs of such simulations are shadow patterns on the surface of the vehicle, indicating locations that are suitable or unsuitable to install solar cells. This paper will show the design procedure of the solar panel for a Challenger Class solar vehicle that participated in the World Solar Challenge 2013, intended to increase the net energy collection. The results obtained, illustrate how the employment of a computational tool can help in the acquisition of both qualitative and quantitative information, related to shadows position and their impact on energy collection. With data inputs such as vehicle geometry and its relative position towards the route, the tool was used to evaluate different possible configurations of solar panel module distribution and select the ones that are more convenient to the given scenario. Therefore, this analysis allows improving the solar panel design by considering important variables that were often overlooked.

Solar competition cars are a very interesting research laboratory for the development of new technologies heading to their further implementation in either commercial passenger vehicles or related applications. Besides, worldwide competitions allow the spreading of such ideas where the best and experienced teams bet on innovation and leading edge technologies, in order to develop more efficient vehicles. In these vehicles, some aspects generally make the difference such as aerodynamics, shape, weight, wheels and the main solar panels. Therefore, seeking to innovate in a competitive advantage, the first Colombian solar vehicle “Primavera”, competitor at the World Solar Challenge (WSC)-2013, has implemented the usage of a Concentrating Photovoltaic (CPV) system as a complementary solar energy module to the common silicon photovoltaic panel. By harvesting sunlight with concentrating optical devices, CPVs are capable of maximizing the allowable photovoltaic area. However, the entire CPV system weight must be less harmful than the benefit of the extra electric energy generated, which in adjunct with added manufacture and design complexity, has intervened in the fact that CPVs had never been implemented in a solar car in such a scale as the one described in this work. Design considerations, the system development process and implementation are presented in this document considering both the restrictions of the context and the interaction of the CPV system with the solar car setup. The measured data evidences the advantage of using this complementary system during the competition and the potential this technology has for further developments.

Since the dawn of precursory revolution in the seismology and electromagnetic radiation platform., F.T. Freund (2010) et.al, have used piezoelectric effect on the crustal geo-materials and emanation of seismic pre signals frequently. Their effect in form of ULF and VHF are commonly detected (by Greece and American seismologists)in the upper ionosphere from surface of globe. TEC, OLR. MMC are the consequent instrumentation in acquiring data to these pre-earthquake signals. Our attempt is to detect the signals prior to earthquake due to impending stress in the area and store the spreading destructive energy to electrical voltage applying the mathematics of piezoelectric equations and algebra. Energy released during seismic eruption is in the range of 10 ¹³ to 10¹⁸ Joule for each event of 6 to 8 Mw. Spread and propagation of energy follows the Maxwell theory of wave equation and fundamental law of electricity and electromagnetism. Stress accumulated within the crustal block is triggered into bringing about geophysical and geochemical changes within the reservoir rocks interacting stress. Study made by pioneers in the seismic precursory development states generation of charge and coronal discharge prior seismicity within the rocks under stress. This is consequence to admixing of positive charge developed at unstressed volume and negative at stressed sub volume of rocks¹ [F.T.Freidemann2010]. Ionosphere proturbance in form of ULF, ELF, ELS and EQL, EQS are the projected consequence of electromagnetic wave propagation ^{2 [10,11,15 ]} Harnessing of electrical components from the energy propagated due to stress inducing EM waves is the aim of paper. Electrical discharge prior to seismicity within geo-materials is established phenomena which can be calibrated with the piezoelectric sensors application implanted for detection and harnessing the signals. These prior signals induced in form of electromagnetic response are felicitated into being converted into electrical energy with the suitable circuit diagram of capacitors, condensers and diodes in the piezoelectric mesh of sensors implication implanted within the ground of seismic prone area.

Photonic power conversion combined with a high power laser diode, is a high efficiency solution for rapid, wireless transfer of power to dormant sensors, which have sporadic need for electrical power. In particular, these devices replace, thermal/inductive power sources inside a munition shell, leading to a safe non-radiating environment. Experimental results with a 25 F double-layer, super-capacitor, indicate that the surface irradiance and laser power both determine the minimum energy transfer time. At a power level of 4 W, the energy transfer rate reduces from a 1 J/s to 0.35 J/s as the irradiance level changes from 1125 suns to 63 suns.