A unit commitment study of the application of energy storage toward the integration of renewable generation

To examine the potential benefits of energy storage in the electric grid, a generalized unit commitment model of thermal generating units and energy storage facilities is developed. Three different storage scenarios were tested—two without limits to total storage assignment and one with a constrained maximum storage portfolio. Given a generation fleet based on the City of Austin’s renewable energy deployment plans, results from the unlimited energy storage deployment scenarios studied show that if capital costs are ignored, large quantities of seasonal storage are preferred. This operational approach enables storage of plentiful wind generation during winter months that can then be dispatched during high cost peak periods in the summer. These two scenarios yielded $70 million and$94 million in yearly operational cost savings but would cost hundreds of billions to implement. Conversely, yearly cost reductions of $40 million can be achieved with one compressed air energy storage facility and a small set of electrochemical storage devices totaling 13GWh of capacity. Similarly sized storage fleets with capital costs, service lifetimes, and financing consistent with these operational cost savings can yield significant operational benefit by avoiding dispatch of expensive peaking generators and improving utilization of renewable generation throughout the year. Further study using a modified unit commitment model can help to clarify optimal storage portfolios, reveal appropriate market participation approaches, and determine the optimal siting of storage within the grid.Mechanical Engineerin

Management of Science

NASA concept, philosophy, and approach to science managemen

Optimizing significance testing of astronomical forcing in cyclostratigraphy

Peer reviewedPublisher PD

On the Numerical Dispersion of Electromagnetic Particle-In-Cell Code : Finite Grid Instability

The Particle-In-Cell (PIC) method is widely used in relativistic particle beam and laser plasma modeling. However, the PIC method exhibits numerical instabilities that can render unphysical simulation results or even destroy the simulation. For electromagnetic relativistic beam and plasma modeling, the most relevant numerical instabilities are the finite grid instability and the numerical Cherenkov instability. We review the numerical dispersion relation of the electromagnetic PIC algorithm to analyze the origin of these instabilities. We rigorously derive the faithful 3D numerical dispersion of the PIC algorithm, and then specialize to the Yee FDTD scheme. In particular, we account for the manner in which the PIC algorithm updates and samples the fields and distribution function. Temporal and spatial phase factors from solving Maxwell's equations on the Yee grid with the leapfrog scheme are also explicitly accounted for. Numerical solutions to the electrostatic-like modes in the 1D dispersion relation for a cold drifting plasma are obtained for parameters of interest. In the succeeding analysis, we investigate how the finite grid instability arises from the interaction of the numerical 1D modes admitted in the system and their aliases. The most significant interaction is due critically to the correct represenation of the operators in the dispersion relation. We obtain a simple analytic expression for the peak growth rate due to this interaction.Comment: 25 pages, 6 figure

Screening analysis and selection of emission reduction concepts for intermittent combustion aircraft engines

An analysis was conducted to screen, evaluate, and select three engine exhaust emission reduction concepts from a group of 14 candidate alternatives. A comprehensive literature search was conducted to survey the emission reduction technology state-of-the-art and establish contact with firms working on intermittent combustion engine development and pollution reduction problems. Concept development, advantages, disadvantages, and expected emission reduction responses are stated. A set of cost effectiveness criteria was developed, appraised for relative importance, and traded off against each concept so that its merit could be determined. A decision model was used to aid the evaluators in managing the criteria, making consistent judgements, calculating merit scores, and ranking the concepts. An Improved Fuel Injection System, Improved Cooling Combustion Chamber, and a Variable Timing Ignition System were recommended to NASA for approval and further concept development. An alternate concept, Air Injection, was also recommended

Nomad, a naval message understanding system

We are building systems to automatically analyze Navy messages. Such messages typically are terse and use many abbreviations and Navy jargon. As a result, they are more difficult to understand than everyday English.The NOMAD system interacts with a message sender to ensure that only unambiguous and reasonably correct messages are generated. The VOX system will allow a human tutor to interactively extend the knowledge base of NOMAD

Preliminary rotor wake measurements with a laser velocimeter

A laser velocimeter (LV) was used to determine rotor wake characteristics. The effect of various fuselage widths and rotor-fuselage spacings on time averaged and detailed time dependent rotor wake velocity characteristics was defined. Definition of time dependent velocity characteristics was attempted with the LV by associating a rotor azimuth position with each velocity measurement. Results were discouraging in that no apparent time dependent velocity characteristics could be discerned from the LV measurements. Since the LV is a relatively new instrument in the rotor wake measurement field, the cause of this lack of periodicity is as important as the basic research objectives. An attempt was made to identify the problem by simulated acquisition of LV-type data for a predicted rotor wake velocity time history. Power spectral density and autocorrelation function estimation techniques were used to substantiate the conclusion that the primary cause of the lack of time dependent velocity characteristics was the nonstationary flow condition generated by the periodic turbulence level that currently exists in the open throat configuration of the wind tunnel

Building a comprehensive mentoring academy for schools of health.

Formal mentoring programs are increasingly recognized as critical for faculty career development. We describe a mentoring academy (MA) developed for faculty across tracks (i.e., researchers, clinicians, educators) within a "school of health" encompassing schools of medicine and nursing. The program is anchored dually in a clinical and translational science center and a school of health. The structure includes the involvement of departmental and center mentoring directors to achieve widespread uptake and oversight. A fundamental resource provided by the MA includes providing workshops to enhance mentoring skills. Initiatives for junior faculty emphasize establishing and maintaining strong mentoring relationships and implementing individual development plans (IDPs) for career planning. We present self-report data on competency improvement from mentor workshops and data on resources and barriers identified by junior faculty (n = 222) in their IDPs. Mentors reported statistically significantly improved mentoring competency after workshop participation. Junior faculty most frequently identified mentors (61%) and collaborators (23%) as resources for goal attainment. Top barriers included insufficient time and time-management issues (57%), funding limitations (18%), work-life balance issues (18%), including inadequate time for self-care and career development activities. Our MA can serve as a model and roadmap for providing resources to faculty across traditional tracks within medical schools

Increased Rates of Prolonged Length of Stay, Readmissions, and Discharge to Care Facilities among Postoperative Patients with Disseminated Malignancy: Implications for Clinical Practice.

BackgroundThe impact of surgery on end of life care for patients with disseminated malignancy (DMa) is incompletely characterized. The purpose of this study was to evaluate postoperative outcomes impacting quality of care among DMa patients, specifically prolonged length of hospital stay, readmission, and disposition.MethodsThe American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database was queried for years 2011-2012. DMa patients were matched to non-DMa patients with comparable clinical characteristics and operation types. Primary hepatic operations were excluded, leaving a final cohort of 17,972 DMa patients. The primary outcomes were analyzed using multivariate Cox regression models.ResultsDMa patients represented 2.1% of all ACS-NSQIP procedures during the study period. The most frequent operations were bowel resections (25.3%). Compared to non-DMa matched controls, DMa patients had higher rates of postoperative overall morbidity (24.4% vs. 18.7%, p<0.001), serious morbidity (14.9% vs. 12.0%, p<0.001), mortality (7.6% vs. 2.5%, p<0.001), prolonged length of stay (32.2% vs. 19.8%, p<0.001), readmission (15.7% vs. 9.6%, p<0.001), and discharges to facilities (16.2% vs. 12.9%, p<0.001). Subgroup analyses of patients by procedure type showed similar results. Importantly, DMa patients who did not experience any postoperative complication experienced significantly higher rates of prolonged length of stay (23.0% vs. 11.8%, p<0.001), readmissions (10.0% vs. 5.2%, p<0.001), discharges to a facility (13.2% vs. 9.5%, p<0.001), and 30-day mortality (4.7% vs. 0.8%, p<0.001) compared to matched non-DMa patients.ConclusionSurgical interventions among DMa patients are associated with poorer postoperative outcomes including greater postoperative complications, prolonged length of hospital stay, readmissions, disposition to facilities, and death compared to non-DMa patients. These data reinforce the importance of clarifying goals of care for DMa patients, especially when acute changes in health status potentially requiring surgery occur