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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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At least 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Design and Analysis of a Floating-Wind Shallow-Water Mooring System Featuring Polymer Springs

This paper presents a mooring system design featuring polymer springs for the VolturnUS-S 15-MW reference floating wind turbine in site conditions for the New York Bight at a 50-m water depth. Polymer springs have a nonlinear stress-strain curve that allows a stiffer response at low loads and a more flexible response at higher loads, potentially reducing peak mooring line tensions. The mooring dynamics model MoorDyn has been extended to model springs with nonlinear tension-strain curves from a user-inputted look-up table. This MoorDyn modeling advancement is verified against OrcaFlex simulation results. Using MoorDyn's updated capabilities, a spring-equipped catenary mooring system is designed for the 15-MW floating system, along with a baseline catenary mooring system that does not use polymer springs. The floating wind turbine simulator OpenFAST is used to simulate the mooring systems in design-driving load cases to show the effect of polymer springs on key dynamic behaviours. The results show that the spring-equipped design reduces peak tensions by up to 60%, whereas the turbine offsets stay within a maximum of 7.2 m, which is still a reasonable offset limit for cable considerations. The reduction in peak tensions results in a significant decrease in damage equivalent loads - on the order of 50% for upwind lines in fully loaded conditions. These results show that polymer springs can effectively reduce peak tensions and fatigue loads in mooring systems at shallow water depths.

floating offshore wind↗
DOE OSTI2022

Design and Analysis of a Floating-Wind Shallow-Water Mooring System Featuring Polymer Springs: Preprint

In this paper, a mooring system featuring polymer springs is designed for the VolturnUS-S 15 MW reference floating wind turbine in site conditions for the New York Bight at a 50-m water depth. Polymer springs have a nonlinear stress-strain curve that allows a stiffer response at low loads and a more flexible response at higher loads, potentially reducing peak mooring line tensions. The mooring dynamics model MoorDyn has been extended to model springs with nonlinear tension-strain curves from a user-inputted look-up table. This MoorDyn modelling advancement is verified against OrcaFlex simulation results. Using MoorDyn's updated capabilities, a spring-equipped catenary mooring system is designed for the 15 MW floating system, along with a baseline catenary mooring system that does not use polymer springs. The floating wind turbine simulator OpenFAST is used to simulate the mooring systems in design-driving load cases to show the effect of polymer springs on key dynamic behaviours. The results show that the spring-equipped design reduces peak tensions by up to 60%, while the turbine offsets stay within a maximum of 7.2 m, which is still a reasonable offset limit for cable considerations. The reduction in peak tensions results in a significant decrease in damage equivalent loads, on the order of 50% for upwind lines in fully loaded conditions. These results show that polymer springs can effectively reduce peak tensions and fatigue loads in mooring systems at shallow water depths.

floating offshore wind↗
DOE OSTI2023

Open Building Operating System: An Open-Source Grid Responsive Control Platform for Buildings

Grid-interactive efficient buildings (GEBs) with flexible loads are a promising method to decarbonize buildings, shift loads during peak hours, and lower energy use and electricity costs. Despite the promising benefits of GEBs, automation systems that manage flexible loads in response to energy prices or other grid signals are still uncommon in small and medium commercial buildings. Recent literature demonstrates such control solutions, but they often rely on custom integrations lacking the tools and drivers needed for scalability. To address these gaps, our team has created a fully open-source software stack capable of integrating heterogeneous flexible building loads and implementing integrated portable control applications called the Open Building Operating System (OpenBOS). The software can be deployed over existing control architecture with a small capital cost. OpenBOS leverages semantic models, which have been the subject of recent investigations to facilitate application portability. The use of semantic data reduces the labor and expense required to deploy and update smart control applications, increasing scalability. In this paper, the semantic modeling schema "Brick" was used, but the proposed approach can also be applied to ASHRAE standard 223P, when released. This paper describes the methodology and software components of OpenBOS and demonstrates its functionality with a rule-based demand flexibility control application configured using a semantic model. This application was tested at a real building in NY that uses a dual-fuel heating system made up of five ductless heat pump mini-splits and a central furnace serving a single zone. The demonstration reduced electricity costs at the site by 27%, demand during a shed event by 49%, and furnace usage by 35%.

24 POWER TRANSMISSION AND DISTRIBUTION↗
NASA NTRS1984

Helicopter rotor blade design for minimum vibration

The importance of blade design parameters in rotor vibratory response and the design of a minimum vibration blade based upon this understanding are examined. Various design approaches are examined for a 4 bladed articulated rotor operating at a high speed flight condition. Blade modal shaping, frequency placement, structural and aerodynamic coupling, and intermodal cancellation are investigated to systematically identify and evaluate blade design parameters that influence blade airloads, blade modal response, hub loads, and fuselage vibration. The relative contributions of the various components of blade force excitation and response to the vibratory hub loads transmitted to the fuselage are determined in order to isolate primary candidates for vibration alleviation. A blade design is achieved which reduces the predicted fuselage vibration from the baseline blade by approximately one half. Blade designs are developed that offer significant reductions in vibration (and fatigue stresses) without resorting to special vibration alleviation devices, radical blade geometries, or weight penalties.

Taylor, R. B.↗
DOE OSTI2015

Opportunities for Automated Demand Response in California Wastewater Treatment Facilities

Previous research over a period of six years has identified wastewater treatment facilities as good candidates for demand response (DR), automated demand response (Auto-­DR), and Energy Efficiency (EE) measures. This report summarizes that work, including the characteristics of wastewater treatment facilities, the nature of the wastewater stream, energy used and demand, as well as details of the wastewater treatment process. It also discusses control systems and automated demand response opportunities. Furthermore, this report summarizes the DR potential of three wastewater treatment facilities. In particular, Lawrence Berkeley National Laboratory (LBNL) has collected data at these facilities from control systems, submetered process equipment, utility electricity demand records, and governmental weather stations. The collected data were then used to generate a summary of wastewater power demand, factors affecting that demand, and demand response capabilities. These case studies show that facilities that have implemented energy efficiency measures and that have centralized control systems are well suited to shed or shift electrical loads in response to financial incentives, utility bill savings, and/or opportunities to enhance reliability of service. In summary, municipal wastewater treatment energy demand in California is large, and energy-­intensive equipment offers significant potential for automated demand response. In particular, large load reductions were achieved by targeting effluent pumps and centrifuges. One of the limiting factors to implementing demand response is the reaction of effluent turbidity to reduced aeration at an earlier stage of the process. Another limiting factor is that cogeneration capabilities of municipal facilities, including existing power purchase agreements and utility receptiveness to purchasing electricity from cogeneration facilities, limit a facility’s potential to participate in other DR activities.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1987

Mechanical response of unidirectional boron/aluminum under combined loading

Three test methods were employed to characterize the response of unidirectional Boron/Aluminum metal matrix composite material under monotonic and cyclic loading conditions, namely, losipescu shear, off-axis tension and compression. The characterization of the elastic and plastic response includes the elastic material properties, yielding and subsequent hardening of the unidirectional composite under different stress ratios in the material principal coordinate system. Yield loci generated for different stress ratios are compared for the three different test methods, taking into account residual stresses and specimen geometry. Subsequently, the yield locus for in-plane shear is compared with the prediction of an analytical, micromechanical model. The influence of the scatter in the experimental data on the predicted yield surface is also analyzed. Lastly, the experimental material strengths in tension and compression are correlated with the maximum stress and the Tsai-Wu failure criterion.

Becker, Wolfgang↗
NASA NTRS2016

Post-Buckling Analysis of Curved Honeycomb Sandwich Panels Containing Interfacial Disbonds

A numerical study on the effect of facesheet-core disbonds on the post-buckling response of curved honeycomb sandwich panels is presented herein. This work was conducted as part of the development of a damage tolerance plan for the next-generation Space Launch System heavy lift launch vehicle payload fairing. As such, the study utilized full-scale fairing barrel segments as the structure of interest. The panels were composed of carbon fiber reinforced polymer facesheets and aluminum honeycomb core. The panels were analyzed numerically using the finite element method incorporating geometric nonlinearity. In a predetermined circular region, facesheet and core nodes were detached to simulate a disbond, between the outer mold line facesheet and honeycomb core, induced via low-speed impact. Surface-to-surface contact in the disbonded region was invoked to prevent interpenetration of the facesheet and core elements and obtain realistic stresses in the core. The diameter of this disbonded region was varied and the effect of the size of the disbond on the post-buckling response was observed. Significant changes in the slope of the edge load-deflection response were used to determine the onset of global buckling and corresponding buckling load. Finally, several studies were conducted to determine the sensitivity of the numerical predictions to refinement in the finite element mesh.

elastic buckling↗
DOE OSTI2017

Full long-term design response analysis of a wave energy converter

Efficient design of wave energy converters requires an accurate understanding of expected loads and responses during the deployment lifetime of a device. A study has been conducted to better understand best-practices for prediction of design responses in a wave energy converter. A case-study was performed in which a simplified wave energy converter was analyzed to predict several important device design responses. The application and performance of a full long-term analysis, in which numerical simulations were used to predict the device response for a large number of distinct sea states, was studied. Environmental characterization and selection of sea states for this analysis at the intended deployment site were performed using principle-components analysis. The full long-term analysis applied here was shown to be stable when implemented with a relatively low number of sea states and convergent with an increasing number of sea states. As the number of sea states utilized in the analysis was increased, predicted response levels did not change appreciably. Furthermore, uncertainty in the response levels was reduced as more sea states were utilized.

42 ENGINEERING↗
DOE OSTI2017

Quantifying the mechanical effects of He, W and He + W ion irradiation on tungsten with spherical nanoindentation

Here, recent advances in spherical nanoindentation protocols have proven very useful for capturing the grain-scale mechanical response of different metals. This is achieved by converting the load–displacement response into an effective indentation stress–strain response which reveals latent information such as the elastic–plastic transition or indentation yield strength and work-hardening behavior and subsequently correlating the response with the material structure (e.g., crystal orientation) at the indentation site. Using these protocols, we systematically study and quantify the microscale mechanical effects of He, W, and He + W ion irradiation on commercially pure, polycrystalline tungsten. The indentation stress–strain response is correlated with the crystal orientation from electron backscatter diffraction, the defect structure from transmission electron microscopy micrographs, and the stopping range of ions in matter calculations of displacement damage and He concentration. He-implanted grains show a much higher indentation yield strength and saturation stress compared to W-ion-irradiated grains for the same displacement damage. There is also good agreement between the dispersed barrier hardening model with a barrier strength of 0.5–0.8 and void models (Bacon–Kochs–Scattergood and Osetsky–Bacon models) with the experimentally observed changes in indentation strength due to the presence of He bubbles. This finding indicates that a high density (~ 9 × 10 23 m –3 ) and concentration (~ 1.5 at.%) of small (~ 1 nm diameter) He bubbles can be moderate to strong barriers to dislocation slip in tungsten.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Real-time Pricing Demand Response in Operations

Abstract—Dynamic pricing schemes have been implemented in commercial and industrial application settings, and recently they are getting attention for application to residential customers. Time-of-use and critical-peak-pricing rates are in place in various regions and are being piloted in many more. These programs are proving themselves useful for balancing energy during peak periods; however, real-time (5 minute) pricing signals combined with automation in end-use systems have the potential to deliver even more benefits to operators and consumers. Besides system peak shaving, a real-time pricing system can contribute demand response based on the locational marginal price of electricity, reduce load in response to a generator outage, and respond to local distribution system capacity limiting situations. The US Department of Energy (DOE) is teaming with a mid-west electricity service provider to run a distribution feeder-based retail electricity market that negotiates with residential automation equipment and clears every 5 minutes, thus providing a signal for lowering or raising electric consumption based on operational objectives of economic efficiency and reliability. This paper outlines the capability of the real-time pricing system and the operational scenarios being tested as the system is rolled-out starting in the first half of 2012.

Demand Response↗
DOE OSTI2019

Characterization of Stress Corrosion Cracking Initiation Precursors in Cold-Worked Alloy 690 Using Advanced High-Resolution Microscopy

Although highly cold-worked UNS N06690 has been shown to be susceptible to stress corrosion crack growth in pressurized water reactor primary water, it is unclear whether cold-work promotes stress corrosion crack initiation under constant load test conditions. To evaluate the stress corrosion cracking initiation response, constant load tensile and blunt notch compact tension testing were performed on 21% and 31% cold-worked samples from two thermally treated UNS N06690 materials in 360 °C simulated pressurized water reactor primary water. High-resolution examinations were conducted mid- and post-test to record the evolution of grain boundary precursor damage and intergranular crack nucleation by focused ion beam milling combined with scanning electron microscopy and by transmission electron microscopy. The surface and sub-surface morphology of intergranular cavities, local corrosion and shallow cracks were documented. Nanometer-sized cavities were observed associated with grain boundary carbides in all specimens. The 31% cold-work specimens consistently exhibited shallow intergranular cracks with oxidized crack flanks and a high density of cavities ahead of the oxide front. Three-dimensional distribution of carbides and cavities ahead of the cracked grain boundaries was analyzed to gain mechanistic insights into the processes that lead to crack initiation in highly cold-worked UNS N06690.

36 MATERIALS SCIENCE↗
NASA NTRS2011

Self-regulating control of parasitic loads in a fuel cell power system

A fuel cell power system comprises an internal or self-regulating control of a system or device requiring a parasitic load. The internal or self-regulating control utilizes certain components and an interconnection scheme to produce a desirable, variable voltage potential (i.e., power) to a system or device requiring parasitic load in response to varying operating conditions or requirements of an external load that is connected to a primary fuel cell stack of the system. Other embodiments comprise a method of designing such a self-regulated control scheme and a method of operating such a fuel cell power system.

Vasquez, Arturo↗
DOE OSTI2016

Response and representation of ductile damage under varying shock loading conditions in tantalum

The response of polycrystalline metals, which possess adequate mechanisms for plastic deformation under extreme loading conditions, is often accompanied by the formation of pores within the structure of the material. This large deformation process is broadly identified as progressive with nucleation, growth, coalescence, and failure the physical path taken over very short periods of time. These are well known to be complex processes strongly influenced by microstructure, loading path, and the loading profile, which remains a significant challenge to represent and predict numerically. In the current study, the influence of loading path on the damage evolution in high-purity tantalum is presented. Tantalum samples were shock loaded to three different peak shock stresses using both symmetric impact, and two different composite flyer plate configurations such that upon unloading the three samples displayed nearly identical “pull-back” signals as measured via rear-surface velocimetry. While the “pull-back” signals observed were found to be similar in magnitude, the sample loaded to the highest peak stress nucleated a connected field of ductile fracture which resulted in complete separation, while the two lower peak stresses resulted in incipient damage. The damage evolution in the “soft” recovered tantalum samples was quantified using optical metallography, electron-back-scatter diffraction, and tomography. These experiments are examined numerically through the use of a model for shock-induced porosity evolution during damage. The model is shown to describe the response of the tantalum reasonably well under strongly loaded conditions but less well in the nucleation dominated regime. As a result, numerical results are also presented as a function of computational mesh density and discussed in the context of improved representation of the influence of material structure upon macro-scale models of ductile damage.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Using Utility Load Data to Estimate Demand for Space Cooling and Potential for Shiftable Loads

This paper describes a simple method to estimate hourly cooling demand from historical utility load data. It compares total hourly demand to demand on cool days and compares these estimates of total cooling demand to previous regional and national estimates. Load profiles generated from this method may be used to estimate the potential for aggregated demand response or load shifting via coldstorage.

24 POWER TRANSMISSION AND DISTRIBUTION↗
NASA NTRS1997

Novel Composites for Wing and Fuselage Applications: Speedy Nonlinear Analysis of Postbuckled Panels in Shear (SNAPPS)

A simple and rapid analysis method, consisting of a number of modular, 'strength-of-materials-type' models, is presented for predicting the nonlinear response and stiffener separation of postbuckled, flat, composite, shear panels. The analysis determines the maximum principal tensile stress in the skin surface layer under to toe. Failure is said to occur when this stress reaches the mean transverse tensile strength of the layer. The analysis methodology consists of a number of closed-form equations that can easily be used in a 'hand analysis. For expediency, they have been programmed into a preliminary design code called SNAPPS (Speedy Nonlinear Analysis of Postbuckled Panels in Shear), which rapidly predicts postbuckling response of the panel for each value of the applied shear load. SNAPPS response and failure predictions were found to agree well with test results for three panels with widely different geometries, laminates and stiffnesses. Design guidelines are given for increasing the load-carrying capacity of stiffened, composite shear panels.

Sharp, Dave↗
NASA NTRS2014

Evaluating Daily Load Stimulus Formulas in Relating Bone Response to Exercise

Six formulas representing what is commonly referred to as "daily load stimulus" are identified, compared and tested in their ability to relate skeletal mechanical loading to bone maintenance and osteogenic response. Particular emphasis is placed on exercise- induced skeletal loading and whether or not the formulas can adequately capture the known experimental observations of saturation of continuous cyclic loading, rest insertion between repetitions (cycles), recovery of osteogenic potential following saturation, and multiple shorter bouts versus a single long bout of exercise. To evaluate the ability of the formulas to capture these characteristics, a set of exercise scenarios with type of exercise bout, specific duration, number of repetitions, and rest insertion between repetitions is defined. The daily load values obtained from the formulas for the loading conditions of the set of scenarios is illustrated. Not all of the formulas form estimates of daily load in units of stress or in terms of strain at a skeletal site due to the loading force from a specific exercise prescription. The comparative results show that none of the formulas are able to capture all of the experimentally observed characteristics of cyclic loading. However, the enhanced formula presented by Genc et al. does capture several characteristics of cyclic loading that the others do not, namely recovery of osteogenic potential and saturation. This could be a basis for further development of mathematical formulas that more adequately approximates the amount of daily stress at a skeletal site that contributes to bone adaptation.

Pennline, James A.↗
DOE OSTI2014

The behaviour of niobium and molybdenum during uni-axial strain loading

The mechanical response of niobium and molybdenum during one dimensional shock loading in the weak shock regime is investigated in terms of the Hugoniot elastic limit (dynamic yield) and spall (tensile) strengths. Results indicate that although both metals have high elastic limits of ca. 2 GPa, their responses are very different. Deformation in the weak shock regime in niobium is controlled by both the motion and generation of dislocations, resulting in high spall (dynamic tensile) strengths and ductility. In contrast, molybdenum has low spall strength and ductility, which suggests lower dislocation mobility in this metal. We have also shown that the strain-rate in the rising part of the shock front is related to the stress amplitude by the fourth power, as first shown by Swegle and Grady. Although we have not been able to elucidate further on the power relation, we believe that the scaling factor A is related to a materials ability to accommodate shock imposed plasticity via slip and dislocation generation. Overall, we have used arguments about the Peierls stress in body centred cubic metals to explain these results, with niobium (low Peierls stress) having a high dislocation mobility, resulting in behaviour showing some similarities to face centred cubic metals. Molybdenum, with its much higher Peierls stress has a much lower dislocation mobility, and hence lower spall strengths and ductility.

36 MATERIALS SCIENCE↗