Well-To-Wheels Analysis of Landfill Gas-Based Pathways and Their Addition to the Greet Model. (open access)

Well-To-Wheels Analysis of Landfill Gas-Based Pathways and Their Addition to the Greet Model.

Today, approximately 300 million standard cubic ft/day (mmscfd) of natural gas and 1600 MW of electricity are produced from the decomposition of organic waste at 519 U.S. landfills (EPA 2010a). Since landfill gas (LFG) is a renewable resource, this energy is considered renewable. When used as a vehicle fuel, compressed natural gas (CNG) produced from LFG consumes up to 185,000 Btu of fossil fuel and generates from 1.5 to 18.4 kg of carbon dioxide-equivalent (CO{sub 2}e) emissions per million Btu of fuel on a 'well-to-wheel' (WTW) basis. This compares with approximately 1.1 million Btu and 78.2 kg of CO{sub 2}e per million Btu for CNG from fossil natural gas and 1.2 million Btu and 97.5 kg of CO{sub 2}e per million Btu for petroleum gasoline. Because of the additional energy required for liquefaction, LFG-based liquefied natural gas (LNG) requires more fossil fuel (222,000-227,000 Btu/million Btu WTW) and generates more GHG emissions (approximately 22 kg CO{sub 2}e /MM Btu WTW) if grid electricity is used for the liquefaction process. However, if some of the LFG is used to generate electricity for gas cleanup and liquefaction (or compression, in the case of CNG), vehicle fuel produced from LFG can have no fossil …
Date: June 30, 2010
Creator: Mintz, M.; Han, J.; Wang, M.; Saricks, C. & Systems, Energy
Object Type: Report
System: The UNT Digital Library
UC Merced Center for Computational Biology Final Report (open access)

UC Merced Center for Computational Biology Final Report

Final report for the UC Merced Center for Computational Biology. The Center for Computational Biology (CCB) was established to support multidisciplinary scientific research and academic programs in computational biology at the new University of California campus in Merced. In 2003, the growing gap between biology research and education was documented in a report from the National Academy of Sciences, Bio2010 Transforming Undergraduate Education for Future Research Biologists. We believed that a new type of biological sciences undergraduate and graduate programs that emphasized biological concepts and considered biology as an information science would have a dramatic impact in enabling the transformation of biology. UC Merced as newest UC campus and the first new U.S. research university of the 21st century was ideally suited to adopt an alternate strategy - to create a new Biological Sciences majors and graduate group that incorporated the strong computational and mathematical vision articulated in the Bio2010 report. CCB aimed to leverage this strong commitment at UC Merced to develop a new educational program based on the principle of biology as a quantitative, model-driven science. Also we expected that the center would be enable the dissemination of computational biology course materials to other university and feeder institutions, …
Date: November 30, 2010
Creator: Colvin, Michael & Watanabe, Masakatsu
Object Type: Report
System: The UNT Digital Library
Eliminating Electricity Deficit through Energy Efficiency in India:  An Evaluation of Aggregate Economic and Carbon Benefits (open access)

Eliminating Electricity Deficit through Energy Efficiency in India: An Evaluation of Aggregate Economic and Carbon Benefits

Electricity demand has consistently exceeded available supply in India. While the electricity deficit varies across states, nationally it was estimated to be of the order of 12percent on peak and 11percent for electricity during 2008-09. This paper explores a demand-side focused potential for energy efficiency improvement to eliminate the electricity deficit compared to a business as usual (BAU) supply-side focused scenario. The limited availability of finance and other legal and administrative barriers have constrained the construction of new power plant capacity in India. As a result, under the BAU scenario, India continues to face an electricity deficit beyond the end of the Twelfth Five Year Plan. The demand-side cost-effective potential achieved through replacement of new electricity-using products, however, is large enough to eliminate the deficit as early as 2013 and subsequently reduce the future construction of power plants and thus reduce air pollutant emissions. Moreover, energy efficiency improvements cost a fraction of the cost for new supply and can lead to a substantial increase in India's economic output or gross domestic product (GDP). Eliminating the deficit permits businesses that have experienced electricity cutbacks to restore production. We estimate the size of the cumulative production increase in terms of the contribution …
Date: April 30, 2010
Creator: Sathaye, Jayant & Gupta, Arjun
Object Type: Report
System: The UNT Digital Library
Enhancing FEL Power with Phase Shifters (open access)

Enhancing FEL Power with Phase Shifters

Tapering the undulator parameter is a well-known method for maintaining the resonant condition past saturation, and increasing Free Electron Laser (FEL) efficiency. In this paper, we demonstrate that shifting the electron bunch phase relative to the radiation is equivalent to tapering the undulator parameter. Using discrete phase changes derived from optimized undulator tapers for the Linac Coherent Light Source (LCLS) x-ray FEL, we show that appropriate phase shifts between undulator sections can reproduce the power enhancement of undulator tapers. Phase shifters are relatively easy to implement and operate, and could be used to aid or replace undulator tapers in optimizing FEL performance.
Date: July 30, 2010
Creator: Ratner, Daniel; Chao, Alex & Huang, Zhirong
Object Type: Article
System: The UNT Digital Library
Two-Chicane Compressed Harmonic Generation of Soft X-Rays (open access)

Two-Chicane Compressed Harmonic Generation of Soft X-Rays

We propose a simple single-stage scheme to produce fully coherent 3nm radiation. Seeding an electron bunch prior to compression simultaneously shortens the laser wavelength and duration, and increases the modulation amplitude. The final X-ray wavelength is tunable by controlling the compression factor with the RF phase. We propose a two chicane scheme that allows for nearly arbitrary modulation amplitudes, extending the method to photocathode beams. We also show that transportation of fine compressed modulation structure is feasible due to a canceling effect of the second chicane.
Date: July 30, 2010
Creator: Ratner, Daniel; Huang, Z. & Chao, A.
Object Type: Article
System: The UNT Digital Library
Threshold Studies of the Microwave Instability in Electron Storage Rings (open access)

Threshold Studies of the Microwave Instability in Electron Storage Rings

We use a Vlasov-Fokker-Planck program and a linearized Vlasov solver to study the microwave instability threshold of impedance models: (1) a Q = 1 resonator and (2) shielded coherent synchrotron radiation (CSR), and find the results of the two programs agree well. For shielded CSR we show that only two dimensionless parameters, the shielding parameter {Pi} and the strength parameter S{sub csr}, are needed to describe the system. We further show that there is a strong instability associated with CSR, and that the threshold, to good approximation, is given by (S{sub csr})th = 0.5 + 0.12{Pi}. In particular, this means that shielding has little effect in stabilizing the beam for {Pi} {approx}< 2; for larger {Pi} it is effective, with threshold current depending on shielding aperture as h{sup -3/2}. We, in addition, find another instability in the vicinity of {Pi} = 0.7 with a lower threshold, (S{sub csr}){sub th} {approx} 0.2. We find that the threshold to this instability depends strongly on damping time, (S{sub csr}){sub th} {approx} {tau}{sub p}{sup -1/2}, and that the tune spread at threshold is small - both hallmarks of a weak instability.
Date: July 30, 2010
Creator: Bane, K. L. F.; Cai, Y. & Stupakov, G.
Object Type: Article
System: The UNT Digital Library
Electron Beam-Based Sources of Ultrashort X-Ray Pulses. (open access)

Electron Beam-Based Sources of Ultrashort X-Ray Pulses.

A review of various methods for generation of ultrashort x-ray pulses using relativistic electron beam from conventional accelerators is presented. Both spontaneous and coherent emission of electrons is considered. The importance of the time-resolved studies of matter at picosecond (ps), femtosecond (fs), and atttosecond (as) time scales using x-rays has been widely recognized including by award of a Nobel Prize in 1999 [Zewa]. Extensive reviews of scientific drivers can be found in [BES1, BES2, BES3, Lawr, Whit]. Several laser-based techniques have been used to generate ultrashort x-ray pulses including laser-driven plasmas [Murn, Alte, Risc, Rose, Zamp], high-order harmonic generation [Schn, Rund, Wang, Arpi], and laser-driven anode sources [Ande]. In addition, ultrafast streak-camera detectors have been applied at synchrotron sources to achieve temporal resolution on the picosecond time scale [Wulf, Lind1]. In this paper, we focus on a different group of techniques that are based on the use of the relativistic electron beam produced in conventional accelerators. In the first part we review several techniques that utilize spontaneous emission of electrons and show how solitary sub-ps x-ray pulses can be obtained at existing storage ring based synchrotron light sources and linacs. In the second part we consider coherent emission of electrons …
Date: September 30, 2010
Creator: Zholents, A. & (APS), Accelerator Systems Division
Object Type: Report
System: The UNT Digital Library
Spin Properties of Transition-Metallorganic Self-Assembled Molecules (open access)

Spin Properties of Transition-Metallorganic Self-Assembled Molecules

This report summarizes SRI's accomplishments on the project, 'Spin Properties of Transition-Metallorganic Self-Assembled Molecules' funded by the Office of Basic Energy Sciences, US Department of Energy. We have successfully carried out all tasks identified in our proposal and gained significant knowledge and understanding of spin-polarized electronic structure, spin relaxation, and spin-dependent transport in transition-metallorganic molecules and enhohedral fullerenes. These molecules contain integrated spin and charge components and will enable us to achieve sophisticated functions in spintronics and quantum computing at molecular level with simple circuitry and easy fabrication. We have developed microscopic theories that describe the underlying mechanisms of spin-dependent porcesses and constructed quantitative modeling tools that compute several important spin properties. These results represent the basic principles governing the spin-dependent behaviors in nanostructures containing such molecules. Based on these results we have shown that novel device functions, such as electrically controlled g-factor and noninvasive electrical detection of spin dynamics, can be achieved in these nanostructures. Some of our results have been published in peer-reviewed journals and presented at professional conferences. In addition, we have established a close collaboration with experimentalists at Oxford University, UK (Dr. J. Morton and Prof. G. Briggs), Princeton University (Dr. A. Tyryshkin and Prof. S. …
Date: June 30, 2010
Creator: Yu, Zhi Gang
Object Type: Report
System: The UNT Digital Library
Air and Radon Pathway Modeling for the F Area Tank Farm (open access)

Air and Radon Pathway Modeling for the F Area Tank Farm

An air and radon pathways analysis was conducted for the F-Area Tank Farm (FTF) to estimate the flux of volatile radionuclides and radon at the ground surface due to residual waste remaining in the tanks following closure. This analysis was used as the basis to estimate the dose to the maximally exposed individual (MEI) for the air pathway per Curie (Ci) of each radionuclide remaining in the combined FTF waste tanks. For the air pathway analysis, several gaseous radionuclides were considered. These included carbon-14 (C-14), chlorine-36 (Cl-36), iodine-129 (I-129), selenium-79 (Se-79), antimony-125 (Sb-125), tin-126 (Sn-126), tritium (H-3), and technetium-99 (Tc-99). The dose to the MEI was estimated at the SRS Boundary during the 100 year institutional control period. For the 10,000 year post closure compliance period, the dose to the MEI was estimated at the 100 m compliance point. Additionally, the dose to the MEI was estimated at a seepage outcrop located 1600 m from the facility. For the radon pathway analysis, five parent radionuclides and their progeny were analyzed. These parent radionuclides included uranium-238 (U-238), plutonium-238 (Pu-238), uranium-234 (U-234), thorium-230 (Th-230), and radium-226 (Ra-226). The peak flux of radon-222 due to each parent radionuclide was estimated for the simulation …
Date: July 30, 2010
Creator: Dixon, K. & Phifer, M.
Object Type: Report
System: The UNT Digital Library

Fuel Cell Power Model for CHP and CHHP Economics and Performance Analysis

This presentation describes the fuel cell power model for CHP and CHHP economics and performance analysis.
Date: March 30, 2010
Creator: Steward, D. & Penev, M.
Object Type: Presentation
System: The UNT Digital Library
Carrier hopping in disordered semiconducting polymers: How accurate is the Miller-Abrahams model? (open access)

Carrier hopping in disordered semiconducting polymers: How accurate is the Miller-Abrahams model?

We performed direct calculations of carrier hopping rates in strongly disordered conjugated polymers based on the atomic structure of the system, the corresponding electronic states and their coupling to all phonon modes. We found that the dependence of hopping rates on distance and the dependence of the mobility on temperature are significantly different than the ones stemming from the simple Miller-Abrahams model, regardless of the choice of the parameters in the model. A model that satisfactorily describes the hopping rates in the system and avoids the explicit calculation of electron-phonon coupling constants was then proposed and verified. Our results indicate that, in addition to electronic density of states, the phonon density of states and the spatial overlap of the wavefunctions are the quantities necessary to properly describe carrier hopping in disordered conjugated polymers.
Date: July 30, 2010
Creator: Vukmirovic, Nenad & Wang, Lin-Wang
Object Type: Article
System: The UNT Digital Library
The Study of Single Nb3Sn Quadrupole Coils Using a Magnetic Mirror Structure (open access)

The Study of Single Nb3Sn Quadrupole Coils Using a Magnetic Mirror Structure

Several 90-mm quadrupole coils made of 0.7-mm Nb{sub 3}Sn strand based on the 'Restack Rod Process' (RRP) of 108/127 design, with cored and non-cored cables and different cable insulation, were fabricated and individually tested at Fermilab using a test structure designed to provide a quadrupole magnetic field environment. The coils were instrumented with voltage taps and strain gauges to study quench performance and mechanical properties. The Nb{sub 3}Sn strand and cable parameters, the coil fabrication details, the mirror model assembly procedure and test results at temperatures of 4.5 K and 1.9 K are reported and discussed.
Date: July 30, 2010
Creator: Chlachidze, G.; Andreev, N.; Barzi, E.; Bossert, R.; Kashikhin, V. S.; Kashikhin, V. V. et al.
Object Type: Article
System: The UNT Digital Library
Hydrogeologic Model for the Gable Gap Area, Hanford Site (open access)

Hydrogeologic Model for the Gable Gap Area, Hanford Site

Gable Gap is a structural and topographic depression between Gable Mountain and Gable Butte within the central Hanford Site. It has a long and complex geologic history, which includes tectonic uplift synchronous with erosional downcutting associated with the ancestral Columbia River during both Ringold and Cold Creek periods, and by the later Ice Age (mostly glacial Lake Missoula) floods. The gap was subsequently buried and partially backfilled by mostly coarse-grained, Ice Age flood deposits (Hanford formation). Erosional remnants of both the Ringold Formation and Cold Creek unit locally underlie the high-energy flood deposits. A large window exists in the gap where confined basalt aquifers are in contact with the unconfined suprabasalt aquifer. Several paleochannels, of both Hanford and Ringold Formation age, were eroded into the basalt bedrock across Gable Gap. Groundwater from the Central Plateau presently moves through Gable Gap via one or more of these shallow paleochannels. As groundwater levels continue to decline in the region, groundwater flow may eventually be cut off through Gable Gap.
Date: September 30, 2010
Creator: Bjornstad, Bruce N.; Thorne, Paul D.; Williams, Bruce A.; Last, George V.; Thomas, Gregory S.; Thompson, Michael D. et al.
Object Type: Report
System: The UNT Digital Library
Final Status Survey Report for Corrective Action Unit 117 - Pluto Disassembly Facility, Building 2201, Nevada National Security Site, Nevada (open access)

Final Status Survey Report for Corrective Action Unit 117 - Pluto Disassembly Facility, Building 2201, Nevada National Security Site, Nevada

This document contains the process knowledge, radiological data and subsequent statistical methodology and analysis to support approval for the radiological release of Corrective Action Unit (CAU) 117 – Pluto Disassembly Facility, Building 2201 located in Area 26 of the Nevada National Security Site (NNSS). Preparations for release of the building began in 2009 and followed the methodology described in the Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM). MARSSIM is the DOE approved process for release of Real Property (buildings and landmasses) to a set of established criteria or authorized limits. The pre-approved authorized limits for surface contamination values and corresponding assumptions were established by DOE O 5400.5. The release criteria coincide with the acceptance criteria of the U10C landfill permit. The U10C landfill is the proposed location to dispose of the radiologically non-impacted, or “clean,” building rubble following demolition. However, other disposition options that include the building and/or waste remaining at the NNSS may be considered providing that the same release limits apply. The Final Status Survey was designed following MARSSIM guidance by reviewing historical documentation and radiological survey data. Following this review a formal radiological characterization survey was performed in two phases. The characterization revealed multiple areas of …
Date: September 30, 2010
Creator: Frenette, Jeremy Gwin and Douglas
Object Type: Report
System: The UNT Digital Library
Marketing Strategy and Implementation (open access)

Marketing Strategy and Implementation

This report documents the preparation of materials for the marketing campaign that has been designed for middle and high school students in New Mexico to increase interest in participation in national security careers at the National Nuclear Security Administration. The materials and the marketing campaign build on the research that was previously completed, as well as the focus groups that were conducted. This work is a part of the National Nuclear Security Preparedness Project (NSPP). Previous research included outcome analysis to determine appropriate marketing strategies. The analysis was based upon focus groups with middle school and high school students, student interactions, and surveys completed by students to understand and gauge student interest in Science, Technology, Engineering, and Math (STEM) subjects, interest in careers at NNSA, future job considerations, and student desire to pursue post-secondary education. Further, through the focus groups, students were asked to attend a presentation on NNSA job opportunities and employee requirements. The feedback received from the students was utilized to develop the focus and components of a marketing campaign divided into DISCO (Discovering Intelligence and Security Career Opportunities) for the middle school age group and DISCO…..Your Way! for high school age groups. Both campaigns have an intertwined …
Date: September 30, 2010
Creator: unknown
Object Type: Text
System: The UNT Digital Library
Intelligent Component Monitoring for Nuclear Power Plants (open access)

Intelligent Component Monitoring for Nuclear Power Plants

Reliability and economy are two major concerns for a nuclear power generation system. Next generation nuclear power reactors are being developed to be more reliable and economic. An effective and efficient surveillance system can generously contribute toward this goal. Recent progress in computer systems and computational tools has made it necessary and possible to upgrade current surveillance/monitoring strategy for better performance. For example, intelligent computing techniques can be applied to develop algorithm that help people better understand the information collected from sensors and thus reduce human error to a new low level. Incidents incurred from human error in nuclear industry are not rare and have been proven costly. The goal of this project is to develop and test an intelligent prognostics methodology for predicting aging effects impacting long-term performance of nuclear components and systems. The approach is particularly suitable for predicting the performance of nuclear reactor systems which have low failure probabilities (e.g., less than 10-6 year-). Such components and systems are often perceived as peripheral to the reactor and are left somewhat unattended. That is, even when inspected, if they are not perceived to be causing some immediate problem, they may not be paid due attention. Attention to such …
Date: July 30, 2010
Creator: Tsoukalas, Lefteri
Object Type: Report
System: The UNT Digital Library
MIT Clean Energy Prize Competition Final Technical Scientific Report (open access)

MIT Clean Energy Prize Competition Final Technical Scientific Report

Final information about the MIT Clean Energy Competition Submissions
Date: June 30, 2010
Creator: Pacheco, Jose
Object Type: Report
System: The UNT Digital Library
Development and Use of a Bulk Tritium Shipping Package (open access)

Development and Use of a Bulk Tritium Shipping Package

A shipping package for transporting tritium has been developed for use by the National Nuclear Safety Administration as a replacement for the DOE Model UC-609, a tritium package developed and used by the DOE and NRC since the early 1970s. This paper presents the major design features and highlights the improvements made over its predecessor by incorporating new engineered materials and implementing improved testing, handling, and maintenance capabilities, while improving manufacturability. A discussion will be provided demonstrating how the BTSP complies with the regulatory safety requirements of the Nuclear Regulatory Commission. The paper further summarizes the results of testing to 10 CFR 71 Normal Conditions of Transport and Hypothetical Accident Conditions events. Planned and possible future missions for this packaging will be addressed.
Date: September 30, 2010
Creator: Blanton, P.
Object Type: Article
System: The UNT Digital Library
Switchable cell trapping using superparamagnetic beads (open access)

Switchable cell trapping using superparamagnetic beads

Ni{sub 81}Fe{sub 19} microwires are investigated as the basis of a switchable template for positioning magnetically-labeled neural Schwann cells. Magnetic transmission X-ray microscopy and micromagnetic modeling show that magnetic domain walls can be created or removed in zigzagged structures by an applied magnetic field. Schwann cells containing superparamagnetic beads are trapped by the field emanating from the domain walls. The design allows Schwann cells to be organized on a surface to form a connected network and then released from the surface if required. As aligned Schwann cells can guide nerve regeneration, this technique is of value for developing glial-neuronal co-culture models in the future treatment of peripheral nerve injuries.
Date: April 30, 2010
Creator: Bryan, M. T.; Smith, K. H.; Real, M. E.; Bashir, M. A.; Fry, P. W.; Fischer, P. et al.
Object Type: Article
System: The UNT Digital Library
Consolidation of K Basin Sludge Data and Experiences on Agglomerate Formation (open access)

Consolidation of K Basin Sludge Data and Experiences on Agglomerate Formation

This report addresses observations of agglomerate formation, conditions that the data shows lead to agglomeration, the frequency of agglomerate formation and postulated physiochemical mechanisms that may lead to agglomeration.
Date: June 30, 2010
Creator: Hill, S.R.
Object Type: Report
System: The UNT Digital Library
Liquid Hydrogen Absorber for MICE (open access)

Liquid Hydrogen Absorber for MICE

Liquid hydrogen absorbers for the Muon Ionization Cooling Experiment (MICE) have been developed, and the first absorber has been tested at KEK. In the preliminary test at KEK we have successfully filled the absorber with {approx}2 liters of liquid hydrogen. The measured hydrogen condensation speed was 2.5 liters/day at 1.0 bar. No hydrogen leakage to vacuum was found between 300 K and 20 K. The MICE experiment includes three AFC (absorber focusing coil) modules, each containing a 21 liter liquid hydrogen absorber made of aluminum. The AFC module has safety windows to separate its vacuum from that of neighboring modules. Liquid hydrogen is supplied from a cryocooler with cooling power 1.5 W at 4.2 K. The first absorber will be assembled in the AFC module and installed in MICE at RAL.
Date: May 30, 2010
Creator: Ishimoto, S.; Suzuki, S.; Yoshida, M.; Green, Michael A.; Kuno, Y. & Lau, Wing
Object Type: Article
System: The UNT Digital Library
Juvenile Salmon Acoustic Telemetry System Transmitter Downsize Assessment (open access)

Juvenile Salmon Acoustic Telemetry System Transmitter Downsize Assessment

At the request of the U.S. Army Corps of Engineers, Portland District, researchers from Pacific Northwest National Laboratory investigated the use of an application-specific integrated circuit (ASIC) to reduce the weight and volume of Juvenile Salmon Acoustic Telemetry System (JSATS) transmitters while retaining current functionality. Review of the design of current JSATS transmitters identified components that could be replaced by an ASIC while retaining the function of the current transmitter and offering opportunities to extend function if desired. ASIC design alternatives were identified that could meet transmitter weight and volume targets of 200 mg and 100 mm3. If alternatives to the cylindrical batteries used in current JSATS transmitters can be identified, it could be possible to implant ASIC-based JSATS transmitters by injection rather than surgery. Using criteria for the size of fish suitable for surgical implantation of current JSATS transmitters, it was concluded that fish as small as 70 mm in length could be implanted with an ASIC-based transmitter, particularly if implantation by injection became feasible.
Date: April 30, 2010
Creator: Carlson, Thomas J. & Myjak, Mitchell J.
Object Type: Report
System: The UNT Digital Library
Void Growth and Coalescence in Dynamic Fracture from the Atomistic Level (open access)

Void Growth and Coalescence in Dynamic Fracture from the Atomistic Level

An important example of multiscale material response is the fracture of ductile solids. In the process of ductile fracture, voids nucleate, grow and coalesce, and it is this linking process that creates the fracture. Ductile fracture has typically been modeled at the continuum level, in a variety of models that may or may not model voids explicitly. Previously we have studied the plasticity associated with void growth in fcc metals, focusing on copper. In the work discussed here we examine void growth in single crystal and polycrystalline body-centered cubic (bcc) metals (V, Nb, Ta, Mo and W) subjected to tension at a high rate and high triaxiality. Large-scale atomistic models provide detailed information on void nucleation and growth and the plasticity generated as voids coalesce, based solely on the constitutive properties inherent in the interatomic forces. The details of the plasticity may be used to inform dislocation dynamics and continuum plasticity models in order to develop models that scale beyond the nanoscale. We also discuss concurrent multiscale modeling of void growth using Coarse-Grained Molecular Dynamics.
Date: September 30, 2010
Creator: Rudd, R E
Object Type: Article
System: The UNT Digital Library
Modeling and Measurement Constraints in Fault Diagnostics for HVAC Systems (open access)

Modeling and Measurement Constraints in Fault Diagnostics for HVAC Systems

Many studies have shown that energy savings of five to fifteen percent are achievable in commercial buildings by detecting and correcting building faults, and optimizing building control systems. However, in spite of good progress in developing tools for determining HVAC diagnostics, methods to detect faults in HVAC systems are still generally undeveloped. Most approaches use numerical filtering or parameter estimation methods to compare data from energy meters and building sensors to predictions from mathematical or statistical models. They are effective when models are relatively accurate and data contain few errors. In this paper, we address the case where models are imperfect and data are variable, uncertain, and can contain error. We apply a Bayesian updating approach that is systematic in managing and accounting for most forms of model and data errors. The proposed method uses both knowledge of first principle modeling and empirical results to analyze the system performance within the boundaries defined by practical constraints. We demonstrate the approach by detecting faults in commercial building air handling units. We find that the limitations that exist in air handling unit diagnostics due to practical constraints can generally be effectively addressed through the proposed approach.
Date: May 30, 2010
Creator: Najafi, Massieh; Auslander, David M.; Bartlett, Peter L.; Haves, Philip & Sohn, Michael D.
Object Type: Article
System: The UNT Digital Library