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Toward a predictive understanding of low emission fuel-flexible distributed energy turbine systems

Lacaze, Guilhem; Oefelein, Joseph

Using hydrogen derived from coal in power generation is one of the potential strategies being considered for eliminating CO2 emissions from combustion. In a two-stage gas combustor, injection of hydrogen into a secondary combustor provides an effective means for achieving a wide range of power settings. However, when additional hydrogen is injected into the exit stream of the first stage turbine, the mixture may autoignite. This uncontrolled autoignition event is undesirable as it leads to strong acoustic waves and high levels of nitrogen oxides (NOx). Since hydrogen was not a main fuel in the past, studies of hydrogen combustion under gas turbine environments have not been extensively carried out. Autoignition of hydrogen depends on pressure in a nonlinear fashion and is sensitive to the unique transport properties of the small hydrogen molecules, making prediction of autoignition a very challenging task. For both steady and transient flames, Large Eddy Simulation (LES) is essential for obtaining a fundamental understanding of flame stability mechanisms. As such, this work performs a LES study aimed at modeling and understanding 1) key stability mechanism(s) related to flame propagation and/or autoignition, and 2) the effect of pressure on hydrogen combustion over the range of 1 to 20 bar.

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TYPE SAND Report YEAR 2013
DOIOSTI

Microgrid Cyber Security Reference Architecture (V.1.0)

Veitch, Cynthia K.; Henry, Jordan M.; Richardson, Bryan T.; Hart, Derek

This document summarizes the on-going cyber security work and resulting cyber security reference architecture for a secure microgrid control system network. The architecture pre sented here provides guidelines and security recommendations for the implementation of a secure microgrid control system at Department of Defense (DOD) installations. The mi crogrid is designed using the Energy Surety MicrogridTM (ESM) methodology developed by Sandia National Laboratories (SNL). Microgrids developed using the ESM methodology demonstrate— • increased reliability for critical mission loads resulting from the interconnection of electrical generation assets using the existing distribution network • reduced reliance on diesel-generated backup power through the use of renewable energy sources during outages • increased efficiency of diesel backup generators through careful, coordinated operation across the microgrid system • reduced operational risk through a strong focus on cyber security The design of a microgrid control system needs to be more robust than that of a traditional industrial control system (ICS) for the following reasons: • The microgrid is used in emergency situations and may be critical to continuity of operations of an installation. • The microgrid must function during active attack by a capable adversary. As such, the traditional design and implementation for an ICS may not be sufficient for implementing a robust and secure microgrid.

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TYPE SAND Report YEAR 2013
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Reducing Uncertainty in High-Resolution Sea Ice Models

Peterson, Kara J.; Bochev, Pavel B.

Arctic sea ice is an important component of the global climate system, reflecting a significant amount of solar radiation, insulating the ocean from the atmosphere and influencing ocean circulation by modifying the salinity of the upper ocean. The thickness and extent of Arctic sea ice have shown a significant decline in recent decades with implications for global climate as well as regional geopolitics. Increasing interest in exploration as well as climate feedback effects make predictive mathematical modeling of sea ice a task of tremendous practical import. Satellite data obtained over the last few decades have provided a wealth of information on sea ice motion and deformation. The data clearly show that ice deformation is focused along narrow linear features and this type of deformation is not well-represented in existing models. To improve sea ice dynamics we have incorporated an anisotropic rheology into the Los Alamos National Laboratory global sea ice model, CICE. Sensitivity analyses were performed using the Design Analysis Kit for Optimization and Terascale Applications (DAKOTA) to determine the impact of material parameters on sea ice response functions. Two material strength parameters that exhibited the most significant impact on responses were further analyzed to evaluate their influence on quantitative comparisons between model output and data. The sensitivity analysis along with ten year model runs indicate that while the anisotropic rheology provides some benefit in velocity predictions, additional improvements are required to make this material model a viable alternative for global sea ice simulations.

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TYPE SAND Report YEAR 2013
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Sandia Capabilities for the Measurement, Characterization, and Analysis of Heliostats for CSP

Andraka, Charles E.; Ghanbari, Cheryl M.; Gill, David D.; Ho, Clifford K.; Kolb, William J.; Moss, Timothy A.; Yellowhair, Julius

The Concentrating Solar Technologies Organization at Sandia National Laboratories has a long history of performing important research, development, and testing that has enabled the Concentrating Solar Power Industry to deploy full-scale power plants. Sandia continues to pursue innovative CSP concepts with the goal of reducing the cost of CSP while improving efficiency and performance. In this pursuit, Sandia has developed many tools for the analysis of CSP performance. The following capabilities document highlights Sandia's extensive experience in the design, construction, and utilization of large-scale testing facilities for CSP and the tools that Sandia has created for the full characterization of heliostats. Sandia has extensive experience in using these tools to evaluate the performance of novel heliostat designs.

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TYPE SAND Report YEAR 2013
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Evaluation of Annual Efficiencies of High Temperature Central Receiver Concentrated Solar Power Plants With Thermal Energy Storage

Ehrhart, Brian D.; Gill, David D.

The current study has examined four cases of a central receiver concentrated solar power plant with thermal energy storage using the DELSOL and SOLERGY computer codes. The current state-of-the-art base case was compared with a theoretical high temperature case which was based on the scaling of some input parameters and the estimation of other parameters based on performance targets from the Department of Energy SunShot Initiative. This comparison was done for both current and high temperature cases in two configurations: a surround field with an external cylindrical receiver and a north field with a single cavity receiver. There is a fairly dramatic difference between the design point and annual average performance, especially in the solar field and receiver subsystems, and also in energy losses due to the thermal energy storage being full to capacity. Additionally, there are relatively small differences (<2%) in annual average efficiencies between the Base and High Temperature cases, despite an increase in thermal to electric conversion efficiency of over 8%. This is due the increased thermal losses at higher temperature and operational losses due to subsystem start-up and shut-down. Thermal energy storage can mitigate some of these losses by utilizing larger thermal energy storage to ensure that the electric power production system does not need to stop and re-start as often, but solar energy is inherently transient. Economic and cost considerations were not considered here, but will have a significant impact on solar thermal electric power production strategy and sizing.

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TYPE SAND Report YEAR 2013
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Omen: identifying potential spear-phishing targets before the email is sent

Wendt, Jeremy

We present the results of a two year project focused on a common social engineering attack method called "spear phishing". In a spear phishing attack, the user receives an email with information specifically focused on the user. This email contains either a malware-laced attachment or a link to download the malware that has been disguised as a useful program. Spear phishing attacks have been one of the most effective avenues for attackers to gain initial entry into a target network. This project focused on a proactive approach to spear phishing. To create an effective, user-specific spear phishing email, the attacker must research the intended recipient. We believe that much of the information used by the attacker is provided by the target organization's own external website. Thus when researching potential targets, the attacker leaves signs of his research in the webserver's logs. We created tools and visualizations to improve cybersecurity analysts' abilities to quickly understand a visitor's visit patterns and interests. Given these suspicious visitors and log-parsing tools, analysts can more quickly identify truly suspicious visitors, search for potential spear-phishing targeted users, and improve security around those users before the spear phishing email is sent.

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TYPE SAND Report YEAR 2013
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Spatially Varying Embedded Stochastic Galerkin Methods for Steady-State PDEs

Cyr, Eric C.

Existing discretizations for stochastic PDEs, based on a tensor product between the deter ministic basis and the stochastic basis, treat the required resolution of uncertainty as uniform across the physical domain. However, solutions to many PDEs of interest exhibit spatially localized features that may result in uncertainty being severely over or under-resolved by existing discretizations. In this report, we explore the mechanics and accuracy of using a spatially varying stochastic expansion. This is achieved through an adaptive refinement algorithm where simple error estimates are used to independently drive refinement of the stochastic basis at each point in the physical domain. Results are presented comparing the accuracy of the adaptive techinque to the accuracy achieved using uniform refinement.

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TYPE SAND Report YEAR 2013
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Results 57101–57200 of 99,299
Results 57101–57200 of 99,299