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72 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Vegetation Management Cost and Maintenance Implications of Different Ground Covers at Utility-Scale Solar Sites

Utility-scale solar photovoltaics (PV) is the largest and fastest-growing sector of the solar energy market, and plays an important role in ensuring that state and local jurisdictions can meet renewable energy targets. Potential adverse environmental impacts of utility-scale solar PV are well-documented, and the effects of diverse mitigation and dual land use strategies under the banner of ’low-impact solar’ are justly receiving more attention; this article seeks to contribute to improving understanding of this topic. Capital costs for different PV configurations are well-documented; however, operation and maintenance (O&M) costs for vegetation management at low-impact utility-scale solar PV sites are not as well-understood, particularly as they compare to costs for sites that use more conventional ground cover practices, such as turfgrass or gravel. After a literature review of different vegetation strategies and O&M cost considerations, we collected data from utility-scale solar PV O&M stakeholders, including site owners/operators, O&M service providers, vegetation maintenance companies, and solar graziers, on costs and activities associated with vegetation management at low-impact, agrivoltaic, and conventional PV sites. In this paper, we perform data analysis to detail the per-activity and total O&M costs for vegetation management at PV sites with different ground covers and management practices, providing the most comprehensive and detailed assessment of PV vegetation O&M costs to date. For the 54 sites included in our analysis, we found that while the per-acre and per-kilowattdc (kWdc) costs for individual activities, such as mowing, trimming, and herbicide application at native or pollinator friendly ground covers, were lower than at turfgrass sites, the total combined vegetation O&M costs were slightly higher; this is presumably because more individual activities are required for the first 3–5 years of vegetation establishment. Qualitative results include recommendations from data providers for site and system design, and ongoing vegetation management operations.

14 SOLAR ENERGY↗
NASA NTRS1978

Feature discrimination/identification based upon SAR return variations

A study of the statistics of The look-to-look variation statistics in the returns recorded in-flight by a digital, realtime SAR system are analyzed. The determination that the variations in the look-to-look returns from different classes do carry information content unique to the classes was illustrated by a model based on four variants derived from four look in-flight SAR data under study. The model was limited to four classes of returns: mowed grass on a athletic field, rough unmowed grass and weeds on a large vacant field, young fruit trees in a large orchard, and metal mobile homes and storage buildings in a large mobile home park. The data population in excess of 1000 returns represented over 250 individual pixels from the four classes. The multivariant discriminant model operated on the set of returns for each pixel and assigned that pixel to one of the four classes, based on the target variants and the probability distribution function of the four variants for each class.

Rasco, W. A., Sr.↗
NASA NTRS1978

The thermoelastic patch contact problem for large Peclet number

An equation in the form of a Fourier series was derived in an earlier study to give displacements of the originally straight edge of a plate as the result of a small heat input patch moving at speed c along that edge. That unwieldly formulation is reduced to a simple integral equation, which is shown to be manageable in an example calculation. The integral equation is shown to be closely related to that of Ling and Mow, although it is much simpler to use. Comparison of the results of the simplification to results of the original series formulation suggest that the equation proposed for 'high Peclet number' may be a valid approximation for Peclet number as low as 2.5.

Kilaparti, S. R.↗
NASA NTRS1987

AIS-2 spectra of California wetland vegetation

Spectral data gathered by Airborne Imaging Spectrometers-2 from wetlands were analyzed. Spectra representing stands of green Salicornia virginica, green Sesuvium verrucosum, senescing Distichlis spicata, a mixture of senescing Scirpus acutus and Scirpus californicus, senescing Scirpus paludosus, senescent S. paludosus, mowed senescent S. paludosus, and soil were isolated. No difference among narrowband spectral reflectance of the cover types was apparent between 0.8 to 1.6 micron. There were, however, broadband differences in brightness. These differences were sufficient to permit a fairly accurate decomposition of the image into its major cover type components using a procedure that assumes an additive linear mixture of surface spectra.

Gross, Michael F.↗
NASA NTRS1997

Threatened and Endangered Species Survey for Patrick Air Force Base, Florida

A review of previous environmental work conducted at Patrick Air Force Base (PAFB) indicated that several threatened, endangered, or species of special concern occurred or had the potential to occur there. This study was implemented to collect more information on protected species at PAFB. A map of landcover types was prepared for PAFB using aerial photography, groundtruthing, and a geographic information system (GIS). Herbaceous vegetation was the most common vegetation type. The second most abundant vegetation type was disturbed shrubs/exotics. The beach and associated dune vegetation comprised 3.2% of the land area, but was the most extensive natural community within PAFB. A few isolated mangrove communities exist along the Banana River. Seventy-seven species of vascular plants occurred on the dunes, including four species listed by state agencies: spider lily (Hymenocallis latifolia), prickly pear cactus (Opuntia stricta), beach star (Remirea maritima), and inkberry (Scaevola plumien). Surveys of other habitats revealed eighty-four species of vascular plants including two state-listed species: spider lily and prickly pear cactus. Many of these areas are dominated by invasive, exotic species, particularly Brazilian pepper (Schinus terebinthifolius) and Australian pine (Casuarina equisetifolia), and native species of open or disturbed sites such as camphorweed (Heterotheca subaxillaris) and beardgrass (Andropogon spp.). Due to the isolation of PAFB from other natural areas, most exotic plant populations on the base are not an immediate threat to intact native plant communities. Dune habitat was surveyed for the southeastem beach mouse (Peromyscus polionotus niveiventris) by quarterly trapping along eight 100 m transects. No beach mice were found. The limited extent of dune habitat, its fragmented condition, and the isolation of PAFB from extant populations of the beach mouse probably accounts for its absence. Surveys of birds on PAFB found an avifauna characteristic of species that occur in the Indian River Lagoon system. Twenty-five species of waterbirds were observed during quarterly surveys on PAFB, including five species listed as species of special concern by the state of Florida: Snowy Egret (Egretta thula), Little Blue Heron (Egretta caerulea), Tricolored Heron (Egretta tricolo4, White Ibis (Eudocimus albus), and Brown Pelican (Pelecanus occidentalis). The Golf Course was used extensively by almost all species of waterbirds on PAFB. Twenty-two species of shorebirds were observed on PAFB. Although no listed species were observed, the potential exists for several protected species of shorebirds to use the beach at PAFB during some parts of the year. The Airfield runways and associated grass areas were important sites at PAFB for loafing and feeding for some shorebirds. Surveys of rooftop nesting by Least Terns (Stema antillarum) on PAFB found a large colony on a rooftop in the PAFB Industrial Area. This colony produced some independent young. Two rooftop Least Tern colonies reported from previous years were inactive during 1996. A small number of Black Skimmers (Rhynchops nigee attempted to nest at the Least Ten colony but were unsuccessful. Surveys for the gopher tortoise (Gopherus polyphemus) revealed burrows and tortoises only at the Waste Study Site; five burrows and three tortoises were observed. No Florida scrub lizards (Sceloporus woodi), eastern indigo snakes (Drymarchon corais couperl), or diamondback terrapins (Malademys terrapin terrapin) were observed. American alligators (Alligator mississippiensis) were observed on the Golf Course and using ditches, ponds, and areas along the Banana River. The amount of dune habitat could be expanded by not mowing areas adjacent to the dunes to allow dune species to colonize and expand. Planting dune species as part of the beach renourishment project will also increase this habitat. Exotic plants dominate several areas on the base and are used by threatened, endangered, and species of special concern. However, the use of native vegetation in landscaping projects throughout the base would improve habitat for wildlife, and invasive, exotic plants should not be used in any horticultural plantings. Water quality of ponds, ditches, and canals is important for waterbirds; it should be maintained and protected from contamination. Nesting Least Terns are sensitive to disturbance; rooftops used for nesting should be protected from disturbance. Monitoring of Least Tern and Black Skimmer nesting should be continued to determine what roofs are being used and whether nesting is successful. Furthermore, based on the large numbers of waterbirds observed on PAFB, continued monitoring of them is recommended.

Oddy, Donna M.↗
NASA NTRS2008

Using Hyperspectral Imagery to Identify Turfgrass Stresses

The use of a form of remote sensing to aid in the management of large turfgrass fields (e.g. golf courses) has been proposed. A turfgrass field of interest would be surveyed in sunlight by use of an airborne hyperspectral imaging system, then the raw observational data would be preprocessed into hyperspectral reflectance image data. These data would be further processed to identify turfgrass stresses, to determine the spatial distributions of those stresses, and to generate maps showing the spatial distributions. Until now, chemicals and water have often been applied, variously, (1) indiscriminately to an entire turfgrass field without regard to localization of specific stresses or (2) to visible and possibly localized signs of stress for example, browning, damage from traffic, or conspicuous growth of weeds. Indiscriminate application is uneconomical and environmentally unsound; the amounts of water and chemicals consumed could be insufficient in some areas and excessive in most areas, and excess chemicals can leak into the environment. In cases in which developing stresses do not show visible signs at first, it could be more economical and effective to take corrective action before visible signs appear. By enabling early identification of specific stresses and their locations, the proposed method would provide guidance for planning more effective, more economical, and more environmentally sound turfgrass-management practices, including application of chemicals and water, aeration, and mowing. The underlying concept of using hyperspectral imagery to generate stress maps as guides to efficient management of vegetation in large fields is not new; it has been applied in the growth of crops to be harvested. What is new here is the effort to develop an algorithm that processes hyperspectral reflectance data into spectral indices specific to stresses in turfgrass. The development effort has included a study in which small turfgrass plots that were, variously, healthy or subjected to a variety of controlled stresses were observed by use of a hand-held spectroradiometer. The spectroradiometer readings in the wavelength range from 350 to 1,000 nm were processed to extract hyperspectral reflectance data, which, in turn, were analyzed to find correlations with the controlled stresses. Several indices were found to be correlated with drought stress and to be potentially useful for identifying drought stress before visible symptoms appear.

Hutto, Kendall↗
NASA NTRS2023

Stand Alone Electrical Equipment PRL 227a (Formerly PRL 227 LOC3) Confirmatory Sampling Report Addendum

HydroGeoLogic, Inc. (HGL) prepared this Confirmatory Sampling Report Addendum (CSRA) for the National Aeronautics and Space Administration (NASA), Kennedy Space Center (KSC), Florida. PRL 227a Location of Concern (LOC) 3 is located on 10th Street, west of the former Vertical Processing Facility (M7-1469), SWMU 077. The Load Break Switches (LBS) were installed in 1986 and are suspected to have formerly contained dielectric fluid that contained polychlorinated biphenyls (PCBs). The LBS were replaced in 1993 with new LBSs that do not contain PCBs. The LBS are located on a concrete pad surrounded by grass that is mowed and maintained. A total of 330 soil samples were collected between June 2020 and December 2022 from 88 locations at depths ranging from 0-0.5 to 19-20 ft bls. In general, soil samples collected from depths less than 5 ft were collected via hand auger and samples collected beyond 5 ft bls were collected using a direct-push technology drill rig. Soil samples collected from greater than 5 ft bls to 20 ft bls were collected to confirm PCBs were not present at depth in the aquifer matrix. Delineation samples were collected using an approximately 20 ft horizontal spacing. PCB impacted soil has been completely delineated to the State of Florida residential soil cleanup target level (SCTL) at PRL 227a horizontally and vertically. PCB concentrations have been identified above the residential and industrial SCTL as well as concentrations greater than or equal to 50 ppm requiring coordination with EPA and disposal at a facility authorized under TSCA. Based upon the CSRA sampling, an interim measure is recommended to remove PCB impacted soil above the residential SCTL. The total volume of PCB impacted soil to be removed is 591.6 cubic yards. This includes approximately 9.3 cubic yards of soil with PCB concentrations greater than or equal to 50 ppm. An interim measure work plan is included as an attachment to this report.

electrical equipment↗
DOE OSTI2020

Colloidal Three-Dimensional Covalent Organic Frameworks and Their Application as Porous Liquids

Developing solid porous materials into free-flowing liquids with permanent porosity is a promising strategy for overcoming certain limitations of conventional sorbent materials employed in gas storage and separation applications. The ability to control the pore size and chemical functionalities of organic frameworks gives these particular nanoporous materials distinct advantages over other small cage-like molecules or hollow particles that have been developed into porous liquids. Here, we describe the synthesis of a 3D imine-linked colloidal covalent organic framework (COF)-based porous liquid, designed for efficient size-exclusion of solvent, as well as for long-term stability. By tethering ionic liquids to the colloid surface, the colloids can be dried, purified, and resuspended in a variety of solvents without irreversible aggregation typically observed of COF colloids. Colloid size could be controlled between 50 and 400 nm, with surface areas as high as 800 m2/g. The 3D intertwining morphology of the colloids had pore sizes ranging from 5 to 14 Å, allowing them to efficiently sizeexclude bulky ionic liquids. The COF colloids were stable towards flocculation in an ionic liquid for > 1 year. Permanent porosity was confirmed with a combination of 19F NMR measurements and gas sorption techniques. CO2 and CH4 uptake in these porous liquids increased more than 10 and 20-fold, respectively, over non-porous, neat ionic liquid control samples. The work not only advances the state of COF-based colloid science but also represents a practical advance towards developing more robust, tunable framework-based porous liquid materials for a host of gas storage and separation applications.

Mow, Rachel E.↗
DOE OSTI2020

Addressing the Stability Gap in Photoelectrochemistry: Molybdenum Disulfide Protective Catalysts for Tandem III–V Unassisted Solar Water Splitting

While photoelectrochemical (PEC) solar-to-hydrogen efficiencies have greatly improved over the past few decades, advances in PEC durability have lagged behind. Corrosion of semiconductor photoabsorbers in the aqueous conditions needed for water splitting is a major challenge that limits device stability. In addition, a precious-metal catalyst is often required to efficiently promote water splitting. In this work, we demonstrate unassisted water splitting using a nonprecious metal molybdenum disulfide nanomaterial catalytic protection layer paired with a GaInAsP/GaAs tandem device. This device was able to achieve stable unassisted water splitting for nearly 12 h, while a sibling sample with a PtRu catalyst was only stable for 2 h, highlighting the advantage of the nonprecious metal catalyst. In situ optical imaging illustrates the progression of macroscopic degradation that causes device failure. Furthermore, this work compares unassisted water splitting devices across the field in terms of the efficiency and stability, illustrating the need for improved stability.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Thermal Activation of a Copper-Loaded Covalent Organic Framework for Near-Ambient Temperature Hydrogen Storage and Delivery

Copper(II) formate is efficiently incorporated into the pores of a 2D imine-based covalent organic framework (COF) via coordination with the phenol and imine groups. The coordinated metal ion is then reduced to Cu(I) with a thermal treatment that evolves CO 2 . After loading with hydrogen gas, the majority of H 2 desorbs from the coordinatively saturated Cu(II) COF at temperatures < -100 degrees C. However, the activated Cu(I) COF retains adsorbed H 2 above room temperature. Adsorption/desorption of H 2 was highly reversible. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) strongly supports a molecular hydrogen interaction with Cu(I). A Kissinger analysis of variable ramp rate desorption experiments estimates the enthalpy of H 2 desorption from Cu(I) at 15 kJ mol -1 . The results represent an advance toward practical H 2 storage and delivery in a lightweight, stable, and highly versatile material.

08 HYDROGEN↗
NASA NTRS2017

EOS Terra: EOS DAM Automation Constellation MOWG

Brief summary of the decision factors considered and process improvement steps made, to evolve the ESMO debris avoidance maneuver process to a more automated process. Presentation is in response to an action item/question received at a prior MOWG meeting.

Constellation MOW↗
NASA NTRS2017

Aqua/Aura Inclination Adjust Maneuver Series Spring 2018 Planning

This will be presented at the International Earth Science Constellation Mission Operations Working Group meeting on December 6-8, 2017 to discuss the Aqua/Aura Spring 2018 Inclination Adjust Maneuver series planning. Presentation has been reviewed and approved by Eric Moyer, ESMO (Earth Science Mission Operations) Deputy Project Manager.

MOW↗
DOE OSTI2021

Atomic Layer Deposition for Materials-Based H2 Storage: Opportunities and Limitations

The transportation demands in our growing hydrogen (H2) economy requires robust storage systems. The current commercially implemented technology in fuel cell cars relies on the well-established technology of hydrogen gas compressed to 350-700 bar, depending on the application. The compressed gas tanks in use today are bulky and cost intensive. To address this challenge, material-based storage is one of the long-term alternatives considered and constitutes the focus of this talk. Material-based storage is broadly defined as hydrogen bound to solid materials, with its binding strength varying from physisorption to porous materials, such as zeolites and metal organic frameworks, to chemisorption in (complex) metal hydrides. The ultimate targets set by the U.S. Department of Energy for this technology include a system gravimetric capacity of 6.5 wt% and volumetric capacity of 40 g/L at 100 bar, operating temperatures ranging between -40 C and +40 C and adsorption/desorption timescales of < 5 min. Storage in the form of physisorbed or chemisorbed hydrogen has guided the materials research, which metal- organic framework and (complex) metal hydrides being the most promising materials classes. A variety of these materials have met one or more of the targets, but it has remained elusive for a single material system to meet all these stringent requirements. Nano-encapsulation and low-concentration chemical additives have previously been employed separately to overcome such challenges. Functionalization via atomic layer deposition (ALD), however, offers unique characteristics that make it suitable for both, nano-encapsulation and "doping" with low-concentration additives. This deposition technique has sub-monolayer thickness control, is highly conformal in high-surface area materials and is self-limiting, i.e., once the gas-phase precursor reacts with the available surface sites, the surface reactions stop. In this presentation, we will showcase examples where ALD, more generally vapor-phase functionalization, on (complex) metal hydrides and organic frameworks has improved the material properties for H2 storage. In our first study, Al2O3 was deposited on magnesium borohydride, Mg(BH4)2, at room temperature using trimethylaluminum (TMA) and water. From our findings, encouraging initial results were obtained: the H2 desorption temperature was lowered by 60-120 degrees C, the desorbed gravimetric H2 capacity at temperatures < 250 degrees C was doubled, and the desorption kinetics increased by a factor of ~6 compared to uncoated Mg(BH4)2. However, hydrolysis reactions caused by residual surface -OH groups from the ALD water-pulse degraded the sample substantially. Through this study, the use of TMA was observed to be highly reactive with the Mg(BH4)2 surface species, leading to the strategy of exposing the sample only to TMA. The relative mole fraction of the vapor-phase additive can be precisely controlled with the number of TMA pulses and pulse duration. By tuning these parameters, we show in our second study that 10 pulses of TMA at ambient conditions were able to decrease the H2 desorption temperature by ~100 degrees C while retaining <95 % of its H2 capacity. We applied this approach with other additives such as BBr3, TiCl4 and tetrahydrofuran, and demonstrate that this unique approach opens the door to a new class of molecular additives and catalysts which cannot easily be introduced with conventional mechano-chemical or solvent-based techniques for (complex) metal-hydrides. In the case of metal organic frameworks, ALD is a promising technique to functionalize the pores with metal atoms or functional groups able to tune the gas selectivity and binding energy, for which ~15 kJ/mol has been established as the optimal value for H2 storage in sorbent materials. Vapor-phase techniques such as ALD have numerous benefits over other functionalization tools for H2 storage materials opening innumerable opportunities to the field. To exploit these opportunities, the current limitations on room temperature and water-less ALD processes needs to be overcome which will greatly expand the possibilities of encapsulation and incorporation of additives for organic frameworks and (complex) metal hydrides.

atomic layer deposition↗