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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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The equivalent fluence concept is defined, and its use and potential problems are noted. Silicon and GaAs solar cells are compared in a radiation environment. The analysis indicates that valid equivalent fluence values may be easier to obtain in GaAs than in silicon.
The ionospheric contribution of the polar wind and cleft ion fountain at energies less than 10 eV has been added to previously measured sources; this total ion outflow has then been used to calculate the resulting ion density in the different internal regions of the earth's magnetosphere: plasmasphere, plasma trough, plasma sheet, and magnetotail lobes. Using estimated volumes for these regions and an ion residence time characteristic of each region, it is found that the observed magnetospheric densities can be attained in all cases with no contribution from the solar wind plasma. In the case of the plasma sheet the ionospherically supplied density is more than enough to match the observations and even suggests an invisible component of low-energy plasma (less than 10 eV) which has never been observed. A detailed comparison between the calculated ionospheric source effects in the plasma sheet and those recently measured by ISEE shows excellent agreement and suggests a direct polar low-energy ion source for the plasma sheet which has remained unmeasured because of spacecraft potential effects. Although the solar wind is clearly the earth's magnetospheric energy source and energetic solar wind ions are observed in the magnetosphere, these calculations suggest the possibility that the ionospheric source alone is sufficient to supply the entire magnetospheric plasma content under all geomagnetic conditions.
One of the outstanding questions related to the solar wind is the heating of solar wind plasma. Addressing this question requires a self consistent treatment of the kinetic physics of a collisionless plasma. A hybrid code (with particle ions and fluid electrons) is one of the most convenient computational tools, which allows us to explore self consistent ion kinetics, while saving us computational time as compared to the full particle in cell codes. A common assumption used in hybrid codes is that of isothermal electrons. In this paper, we discuss the role that the equation of state for electrons could potentially play in determining the ion kinetics.
This project focused on the development of metal halide perovskite-polymeric nanofiber nanocomposites for robust and efficient solar cells. Metal halide perovskite solar cells are a potentially disruptive technology with high efficiencies and low-cost solution processability amenable with roll-to-roll fabrication of flexible devices. However, perovskites exhibit extreme brittleness, high internal film stresses, and chemical instabilities that significantly limit service lifetimes under normal operating conditions. To date, most work addressing these shortcomings has been focused on encapsulating devices between thick layers of rigid materials such as glass, which increases the total weight and cost of devices. Furthermore, these rigid and heavy encapsulants do not translate well to emerging solar markets vital for national security, including integrated mobile power, emergency deployments for disaster relief and military engagement, and lightweight power for space. It is therefore critical to improve the thermomechanical and chemical stability of perovskite devices in a way that is compatible with flexible and lightweight substrates. In this project, we integrated nylon-6,6 nanofibers into MAPbI3 to mechanically reinforce the perovskite, demonstrating films that exhibited fracture energies 5-fold greater than pristine MAPbI3 while also maintaining similar power conversion efficiencies due to beneficial light scattering effects from the polymeric nanofibers. These results required successful development of approaches to control the deposition thickness of nanofiber mats down to 100s of nanometers, and to ensure the polymer nanofibers did not inhibit charge transport to the at the perovskite-transport layer interface.
Nonplanar structured photovoltaic absorber design has potential to achieve high solar cell efficiency with significantly reduced material use. We report optoelectronic simulations that highlight photon and generated carrier management opportunities for improvement of thin film Cu(In x Ga 1-x )Se 2 (CIGS) device performance. Structures realized via either self-assembly or patterning via nanoimprint lithography, and also a combination of both are predicted to exhibit significant increases in short circuit current density and open circuit voltage simultaneously. The structures investigated include: 1) self-assembled nonplanar structures that strongly scatter incident light and enhance carrier generation near regions of high electric potential, 2) lithographicallypatterned embedded periodic dielectric structures, 3) planar dielectric layers that separate the CIGS absorber from the molybdenum back-contact via reduced-area contacts that minimize optical and electronic losses, 4) a combination of these for combined effects. We find that the self-assembled nonplanar CIGS cells with 700 nm planar equivalent thickness, combined with dielectric separation layers yield increases in short circuit current density and open circuit voltage up to 3.4 mA cm -2 and 29 mV, respectively. The absolute efficiency increases from 15.4% to 18.1%, compared to the predicted efficiency for planar CIGS thin film cells of equivalent thickness. The addition of a single layer MgF 2 anti-reflection coating brings the maximum predicted efficiency up to 19.7% for randomly textured devices.
This article presents experimental data for the thermal performance of a stationary, spherical-reflector, tracking-absorber solar energy collector (SRTA). The principle of operation and details of thermal performance of such an SRTA have previously been described. These experimental results were compared with the predictions of a thermal analysis previously published. Experimental results were compared with the prediction of Kreider's computer model. Within the range of the temperature of the experiments, the predicted performance of the unit agreed well with experimental data collected under clear sky conditions. In addition, the extrapolation of the efficiency to higher temperature is shown so that the potential of an SRTA solar collector as a means of providing high temperature steam to operate an electric power facility or for process heat can be evaluated. As a result of the tests conducted by NASA, and an economic analysis not yet publicly available, it appears that the SRTA solar collector concept will be economically viable in competition with any other existing solar system in providing electrical energy.
The share of variable renewable energy (VRE) on India's grid has surpassed 100 GW, and the government has ambitious plans reach 450 GW by 2030. One strategy to increase wind and solar PV deployment is through the co-location of wind and solar PV plants to form a single hybrid power plant. Hybrid plants have the potential to reduce transmission infrastructure costs and variability in the output power profile compared to a standalone plant with a single technology, and this resource analysis aims to take a first step towards quantifying the potential savings from hybridizing wind and solar PV plants in India and the size of this opportunity. We utilize a brute-force optimization to minimize the levelized cost of energy (LCOE) for standalone wind, standalone solar PV, and hybrid wind/solar PV plants across all of India. By comparing these LCOEs, we determine that locations where hybrid plants exhibit potential cost savings and grid benefits exhibit both; a high interconnection cost and; a wind capacity factor between roughly 34% and 38%. However, because our work does not capture the value of the electricity generated by looking at energy prices, nor does it quantify the potential of hybrids to provide other value streams such as firm capacity and reserves. Further, because the work does not compare solar PV and wind hybrids to alternative generation technologies or storage systems, it cannot be considered a holistic cost-benefit analysis.
SnO{sub 2} nanofibers and their composites based photoanodes were fabricated and investigated in the application of dye-sensitized solar cells. The photoanode made of SnO{sub 2}/TiO{sub 2} composites yielded an over 2-fold improvement in overall conversion efficiency. The microstructure of SnO{sub 2} nanofibers was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). A compact morphology of composites was observed using scanning electron microscopy (SEM). A long charge diffusion length (62.42 μm) in the composites was derived from time constant in transient photovoltage and photocurrent analysis. These experimental results demonstrate that one-dimensional nanostructured SnO{sub 2}/TiO{sub 2} composites have a great potential for application in solar cells.
The utilization of Space resources has been identified in publications for over 40 years for its potential as a "game changing" technology for the human exploration of Space. It is called "game changing" because of the mass leverage possible when local resources at the exploration destination arc used to reduce or even eliminate resources that are brought from the Earth. NASA, under the Exploration Technology Development Program has made significant investments in the development of Space resource utilization technologies as a part of the In-Situ Resource Utilization (ISRU) project. Over the last four years, the ISRU project has taken what was essentially an academic topic with lots of experimentation but little engineering and produced near-full-scale systems that have been demonstrated. In 2008 & again in early 2010, systems that could produce oxygen from lunar soils (or their terrestrial analogs) were tested at a lunar analog site on a volcano in Hawaii. These demonstrations included collaborations with International Partners that made significant contributions to the tests. The proposed federal budget for Fiscal Year 2011 encourages the continued development and demonstration of ISRU. However it goes beyond what the project is currently doing and directs that the scope of the project be expanded to cover destinations throughout the inner solar system with the potential for night demonstrations. This paper will briefly cover the past accomplishments of the ISRU project then move to a di scussion of the plans for the project's future as NASA moves to explore a new paradigm for Space Exploration that includes orbital fuel depots and even refueling on other planetary bodies in the solar system.
Observations of T Tauri stars and their circumstellar disks, combined with broadly applied theoretical principles, permit the construction of solar nebular models that are potentially useful for the interpretation of meteoritic data. Quantitative comparisons of model results with meteoritic and planetary data is used to test several propositions regarding the bulk properties of chondrites and chondrule precursor material.
Solar coronal shocks are very common phenomena in the solar atmosphere and are believed to be the drivers of solar type II radio bursts. However, the microphysical nature of these emissions is still an open question. This paper proposes that electron cyclotron maser (ECM) emission is responsible for the generation of radiation from the coronal shocks. In the present model, an energetic ion beam accelerated by the shock first excites the Alfvén wave (AW), then the excited AW leads to the formation of a density-depleted duct along the foreshock boundary of the shock. In this density-depleted duct, the energetic electron beam produced via the shock acceleration can effectively excite radio emission by ECM instability. Our results show that this model may potentially be applied to solar type II radio bursts.
The densities of mid-sized Kuiper Belt objects (KBOs) are a key constraint in understanding the assembly of objects in the outer solar system. These objects are critical for understanding the currently unexplained transition from the smallest KBOs with densities lower than that of water, to the largest objects with significant rock content. Mapping this transition is made difficult by the uncertainties in the diameters of these objects, which maps into an even larger uncertainty in volume and thus density. The substantial collecting area of the Atacama Large Millimeter Array allows significantly more precise measurements of thermal emission from outer solar system objects and could potentially greatly improve the density measurements. Here we use new thermal observations of four objects with satellites to explore the improvements possible with millimeter data. We find that effects due to effective emissivity at millimeter wavelengths make it difficult to use the millimeter data directly to find diameters and thus volumes for these bodies. In addition, we find that when including the effects of model uncertainty, the true uncertainties on the sizes of outer solar system objects measured with radiometry are likely larger than those previously published. Substantial improvement in object sizes will likely require precise occultation measurements.
Solar Dynamic power systems can offer many potential benefits to Earth orbiting satellites including high solar-to-electric efficiency, long life without performance degradation, and high power capability. A recent integrated system test of a 2 kilowatt SD power system in a simulated space environment has successfully demonstrated technology readiness for space flight. Conceptual design studies of SD power systems have addressed several potential mission applications: a 10 kilowatt LEO satellite, a low power Space Based Radar, and a 30 kilowatt GEO communications satellite. The studies show that with moderate component development, SD systems can exhibit excellent mass and deployed area characteristics. Using the conceptual design studies as a basis, a SD technology roadmap was generated which identifies the component advances necessary to assure SD systems a competitive advantage for future NASA, DOD, and commercial missions.
The perovskite solar cell has commercial potential due to the low-cost of materials and manufacturing processes with cell efficiencies on par with traditional technologies. Nanomaterials have many properties that make them attractive for the perovskite devices, including low-cost inks, low temperature processing, stable material properties and good charge transport. In this feature article, the use of nanomaterials in the hole transport and electron transport layers are reviewed. Specifically, SnO 2 and NiO x are the leading materials with the most promise for translation to large scale applications. Here, the review includes a discussion of the synthesis, formulation, and processing of these nanoparticles and provides insights for their further deployment towards commercially viable perovskite solar cells.
Solar Coronal Mass Ejections (CMEs) from the Sun are an important aspect of coronal physics, and a potentially important contributor to the solar wind mass flux. However, despite significant progress in studies of CMEs since their discovery in the early 70's, questions remain about their effects on the interplanetary medium. A study is done of the long-term variations of the occurrence rates of CMEs, of activity tracers related to CMEs, and of the solar wind particle flux. CMEs are most directly detected by scattered electron radiation in white light. To estimate their long-term occurrence frequency and their contributions to the in-ecliptic solar wind mass flux, observed CME rates must be corrected for instrumental duty cycles, detection efficiency out of the plane of the sky, mass detection thresholds, and geometrical considerations. These corrections are evaluated using data on solar CMEs from the spaceborne Skylab, SMM, and SOLWIND coronagraphs and on interplanetary plasma clouds from the HELIOS white light photometers. Variations in the CME rate and the contribution of CMEs to the solar wind mass flux are traced over nearly a complete solar activity cycle.
The HyS process, driven by solar power, has great potential to reach high-efficiency and low-cost hydrogen production without greenhouse gas emissions. The high-temperature section of the HyS cycle, which operates the catalytic decomposition of sulfuric acid into sulfur dioxide, oxygen, and water, is a fundamental part of the cycle affecting the overall plant efficiency and cost. Therefore, a high-performance catalyst (i.e., low cost, high catalytic activity, and low degradation catalyst) is of critical importance to achieve high efficiency and low hydrogen cost. Research and development has highlighted that a Pt-based monometallic catalyst had unacceptable catalytic activity and performance degradation for a high-efficiency and low-cost hydrogen production process. A high-efficiency solar receiver-reactor system, which incorporates the new catalyst, also needs to be developed to achieve the required plant efficiency and cost. Greenway Energy (GWE) and the University of South Carolina (USC), partnering with HydroGEN node laboratories Idaho National Laboratory (INL), Savannah River National Laboratory (SRNL), and National Renewable Energy Laboratory (NREL), propose the development of a new catalyst formulation, included in a novel solar receiver-reactor concept, to be tested experimentally in the last part of the project.
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The metal content of asteroids is of great interest, not only for theories of their origins and the evolution of the solar system but, in the case of near-Earth objects (NEOs), also for impact mitigation planning and endeavors in the field of planetary resources. However, since the reflection spectra of metallic asteroids are largely featureless, it is difficult to identify them and relatively few are known. We show how data from the Wide-field Infrared Survey Explorer (WISE)/NEOWISE thermal-infrared survey and similar surveys, fitted with a simple thermal model, can reveal objects likely to be metal rich. We provide a list of candidate metal-rich NEOs. Our results imply that future infrared surveys with the appropriate instrumentation could discover many more metal-rich asteroids, providing valuable data for assessment of the impact hazard and the potential of NEOs as reservoirs of vital materials for future interplanetary space activities and, eventually perhaps, for use on Earth.