593 Matching Results

Search Results

Advanced search parameters have been applied.

Modeling Population Exposures to Pollutants Emitted from Natural Gas Cooking Burners

Description: We developed a physics-based data-supported model to investigate indoor pollutant exposure distributions resulting from use of natural gas cooking appliances across households in California. The model was applied to calculate time-resolved indoor concentrations of CO, NO2 and formaldehyde resulting from cooking burners and entry with outdoor air. Exposure metrics include 1-week average concentrations and frequency of exceeding ambient air quality standards. We present model results for Southern California (SoCal) using two air-exchange scenarios in winter: (1) infiltration-only, and (2) air exchange rate (AER) sampled from lognormal distributions derived from measurements. In roughly 40percent of homes in the SoCal cohort (N=6634) the 1-hour USEPA NO2 standard (190 ?g/m3) was exceeded at least once. The frequency of exceeding this standard was largely independent of AER assumption, and related primarily to building volume, emission rate and amount of burner use. As expected, AER had a more substantial impact on one-week average concentrations.
Date: June 1, 2011
Creator: Lobscheid, Agnes; Singer, Brett C. & Klepeis, Neil E.
Partner: UNT Libraries Government Documents Department

Performance of Installed Cooking Exhaust Devices

Description: The performance metrics of airflow, sound, and combustion product capture efficiency (CE) were measured for a convenience sample of fifteen cooking exhaust devices, as installed in residences. Results were analyzed to quantify the impact of various device- and installation-dependent parameters on CE. Measured maximum airflows were 70% or lower than values noted on product literature for 10 of the devices. Above-the-cooktop devices with flat bottom surfaces (no capture hood) – including exhaust fan/microwave combination appliances – were found to have much lower CE at similar flow rates, compared to devices with capture hoods. For almost all exhaust devices and especially for rear-mounted downdraft exhaust and microwaves, CE was substantially higher for back compared with front burner use. Flow rate, and the extent to which the exhaust device extends over the burners that are in use, also had a large effect on CE. A flow rate of 95 liters per second (200 cubic feet per minute) was necessary, but not sufficient, to attain capture efficiency in excess of 75% for the front burners. A-weighted sound levels in kitchens exceeded 57 dB when operating at the highest fan setting for all 14 devices evaluated for sound performance.
Date: November 1, 2011
Creator: Singer, Brett C.; Delp, William W.; Apte, Michael G. & Price, Philip N.
Partner: UNT Libraries Government Documents Department

Pollutant Removal Efficiency of Residential Cooking Exhaust Hoods

Description: Capture efficiency (CE) of exhaust from a natural gas cooking range was quantified for three common designs of residential range hoods in laboratory experiments: (A) microwave exhaust combination; (B) short hood with grease-screen-covered air inlet at bottom; and (C) deep, open hood exhausting at top. Devices were evaluated at varying installation heights, at highest and lowest fan settings, and with the hood installed 15 cm away from back wall with intent to improve CE for front burners. Each configuration was evaluated for the oven and for three cooktop burner combinations (two back, two front, one front and one back). At highest fan settings and standard installation against the wall, Hoods A and C captured back cooktop burner exhaust at > 90 percent and Hood B at > 80 percent. In this configuration, CE for front burner exhaust was 73-78 percent for Hoods A and C but only 46-63 percent for Hood B. CEs followed similar patterns but were substantially lower on the lowest fan speed. Installing the hood away from the wall improved CE for oven and front burners on Hood A at low speed, but substantially reduced CE for back burners for all hoods at low and high speed.
Date: July 1, 2011
Creator: Singer, Brett C.; Sherman, Alexander D.; Hotchi, Toshifumi & Sullivan, Douglas P.
Partner: UNT Libraries Government Documents Department

Comment on"Air Emissions Due to Wind and Solar Power" and Supporting Information

Description: Katzenstein and Apt investigate the important question of pollution emission reduction benefits from variable generation resources such as wind and solar. Their methodology, which couples an individual variable generator to a dedicated gas plant to produce a flat block of power is, however, inappropriate. For CO{sub 2}, the authors conclude that variable generators 'achieve {approx} 80% of the emission reductions expected if the power fluctuations caused no additional emissions.' They find even lower NO{sub x} emission reduction benefits with steam-injected gas turbines and a 2-4 times net increase in NO{sub x} emissions for systems with dry NO{sub x} control unless the ratio of energy from natural gas to variable plants is greater than 2:1. A more appropriate methodology, however, would find a significantly lower degradation of the emissions benefit than suggested by Katzenstein and Apt. As has been known for many years, models of large power system operations must take into account variable demand and the unit commitment and economic dispatch functions that are practiced every day by system operators. It is also well-known that every change in wind or solar power output does not need to be countered by an equal and opposite change in a dispatchable resource. The authors recognize that several of their assumptions to the contrary are incorrect and that their estimates therefore provide at best an upper bound to the emissions degradation caused by fluctuating output. Yet they still present the strong conclusion: 'Carbon dioxide emissions reductions are likely to be 75-80% of those presently assumed by policy makers. We have shown that the conventional method used to calculate emissions is inaccurate, particularly for NO{sub x} emissions.' The inherently problematic methodology used by the authors makes such strong conclusions suspect. Specifically, assuming that each variable plant requires a dedicated natural gas backup plant to create ...
Date: March 18, 2009
Creator: Mills, Andrew D.; Wiser, Ryan H.; Milligan, Michael & O'Malley, Mark
Partner: UNT Libraries Government Documents Department

Effects of Inclusions in HSLA Carbon Steel on Pitting Corrosion in CaCl2

Description: Susceptibility of high strength low alloy steel to localized corrosion was studied in 6.7 M CaCl{sub 2} for oil and natural gas drilling applications. Results of the immersion and electrochemical experiments showed that the steel is susceptible to pitting corrosion. Optical microscopy investigations of the polished samples revealed that 10% of the surface area was occupied by defects in the form of pits. The energy dispersive X-ray (EDX) and wavelength dispersive X-ray (WDX) chemical analyses revealed higher concentrations of Mn and S compared to the metal matrix in defected areas. These areas served as the sites for development of corrosion pits during both immersion and electrochemical experiments. The fatigue results of the corroded samples indicate that if the pit was the most significant defect, the fatigue crack initiated and propagated at this site.
Date: December 5, 2011
Creator: Ziomek-Moroz, M.; Bullard, S.; Rozman, K. & Kruzic, J.J.
Partner: UNT Libraries Government Documents Department

Investigation of the carbon dioxide sorption capacity and structural deformation of coal

Description: Due to increasing atmospheric CO2 concentrations causing the global energy and environmental crises, geological sequestration of carbon dioxide is now being actively considered as an attractive option to mitigate greenhouse gas emissions. One of the important strategies is to use deep unminable coal seams, for those generally contain significant quantities of coal bed methane that can be recovered by CO2 injection through enhanced coal bed natural gas production, as a method to safely store CO2. It has been well known that the adsorbing CO2 molecules introduce structural deformation, such as distortion, shrinkage, or swelling, of the adsorbent of coal organic matrix. The accurate investigations of CO2 sorption capacity as well as of adsorption behavior need to be performed under the conditions that coals deform. The U.S. Department of Energy-National Energy Technology Laboratory and Regional University Alliance are conducting carbon dioxide sorption isotherm experiments by using manometric analysis method for estimation of CO2 sorption capacity of various coal samples and are constructing a gravimetric apparatus which has a visual window cell. The gravimetric apparatus improves the accuracy of carbon dioxide sorption capacity and provides feasibility for the observation of structural deformation of coal sample while carbon dioxide molecules interact with coal organic matrix. The CO2 sorption isotherm measurements have been conducted for moist and dried samples of the Central Appalachian Basin (Russell County, VA) coal seam, received from the SECARB partnership, at the temperature of 55 C.
Date: January 1, 2010
Creator: Hur, Tae-Bong; Fazio, James; Romanov, Vyacheslav & Harbert, William
Partner: UNT Libraries Government Documents Department

Summary of Inorganic Compositional Data for Groundwater, Soil-Water, and Surface-Water Samples at the Headgate Draw Subsurface Drip Irrigation Site

Description: As part of a 5-year project on the impact of subsurface drip irrigation (SDI) application of coalbed-methane (CBM) produced waters, water samples were collected from the Headgate Draw SDI site in the Powder River Basin, Wyoming, USA. This research is part of a larger study to understand short- and long-term impacts on both soil and water quality from the beneficial use of CBM waters to grow forage crops through use of SDI. This document provides a summary of the context, sampling methodology, and quality assurance and quality control documentation of samples collected prior to and over the first year of SDI operation at the site (May 2008-October 2009). This report contains an associated database containing inorganic compositional data, water-quality criteria parameters, and calculated geochemical parameters for samples of groundwater, soil water, surface water, treated CBM waters, and as-received CBM waters collected at the Headgate Draw SDI site.
Date: January 1, 2007
Creator: Geboy, Nicholas J.; Engle, Mark A.; Schroeder, Karl T. & Zupanic, John W.
Partner: UNT Libraries Government Documents Department

Surface Studies of Ultra Strength Drilling Steel after Corrosion Fatigue in Simulated Sour Environment

Description: The Unites States predicted 60% growth in energy demand by 2030 makes oil and natural gas primary target fuels for energy generation. The fact that the peak of oil production from shallow wells (< 5000 m) is about to be reached, thereby pushing the oil and natural gas industry into deeper wells. However, drilling to depths greater than 5000 m requires increasing the strength-to weight ratio of the drill pipe materials. Grade UD-165 is one of the ultra- high yield strength carbon steels developed for ultra deep drilling (UDD) activities. Drilling UDD wells exposes the drill pipes to Cl{sup -}, HCO{sub 3}{sup -}/CO{sub 3}{sup 2-}, and H{sub 2}S-containig corrosive environments (i.e., sour environments) at higher pressures and temperatures compared to those found in conventional wells. Because of the lack of synergism within the service environment, operational stresses can result in catastrophic brittle failures characteristic for environmentally assisted cracking (EAC). Approximately 75% of all drill string failures are caused by fatigue or corrosion fatigue. Since there is no literature data on the corrosion fatigue performance of UD-165 in sour environments, research was initiated to better clarify the fatigue crack growth (FCGR) behavior of this alloy in UDD environments. The FCGR behavior of ultra-strength carbon steel, grade UD-165, was investigated by monitoring crack growth rate in deaerated 5%NaCl solution buffered with NaHCO{sub 3}/Na{sub 2}CO{sub 3} and in contact with H{sub 2}S. The partial pressure of H{sub 2}S (p{sub H2S}) was 0.83 kPa and pH of the solution was adjusted by NaOH to 12. The fatigue experiments were performed at 20 and 85 C in an autoclave with surface investigations augmented by scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) spectroscopy. In this study, research focused on surface analyses supported by the fatigue crack growth rate measurements. Fig. 1 shows an SEM ...
Date: May 6, 2012
Creator: Ziomek-Moroz, M.; Hawk, J.A.; Thodla, R. & Gui, F.
Partner: UNT Libraries Government Documents Department

Case Study of the California Cement Industry

Description: California is the largest cement producing state in theU.S., accounting for between 10 percent and 15 percent of U.S. cementproduction and cement industry employment. The cement industry inCalifornia consists of 31 sites that consume large amounts of energy,annually: 1,600 GWh of electricity, 22 million therms of natural gas, 2.3million tons of coal, 0.25 tons of coke, and smaller amounts of wastematerials, including tires. The case study summarized in this paperfocused on providing background information, an assessment ofenergy-efficiency opportunities and barriers, and program recommendationsthat can be used by program planners to better target products to thecement industry. The primary approach to this case study involvedwalk-through surveys of customer facilities and in depth interviews withcustomer decision makers and subsequent analysis of collected data. Inaddition, a basic review of the cement production process was developed,and summary cement industry energy and economic data were collected, andanalyzed. The analysis of secondary data provides background informationon the cement industry and identification of potential energy-efficiencyopportunities. The interviews provide some understanding of the customerperspective about implementation of energy-efficiencyprojects.
Date: May 1, 2005
Creator: Coito, Fred; Powell, Frank; Worrell, Ernst; Price, Lynn & Friedmann, Rafael
Partner: UNT Libraries Government Documents Department

Can Deployment of Renewable Energy and Energy Efficiency PutDownward Pressure on Natural Gas Prices

Description: High and volatile natural gas prices have increasingly led to calls for investments in renewable energy and energy efficiency. One line of argument is that deployment of these resources may lead to reductions in the demand for and price of natural gas. Many recent U.S.-based modeling studies have demonstrated that this effect could provide significant consumer savings. In this article we evaluate these studies, and benchmark their findings against economic theory, other modeling results, and a limited empirical literature. We find that many uncertainties remain regarding the absolute magnitude of this effect, and that the reduction in natural gas prices may not represent an increase in aggregate economic wealth. Nonetheless, we conclude that many of the studies of the impact of renewable energy and energy efficiency on natural gas prices appear to have represented this effect within reason, given current knowledge. These studies specifically suggest that a 1% reduction in U.S. natural gas demand could lead to long-term average wellhead price reductions of 0.8% to 2%, and that each megawatt-hour of renewable energy and energy efficiency may benefit natural gas consumers to the tune of at least $7.5 to $20.
Date: June 1, 2005
Creator: Wiser, Ryan & Bolinger, Mark
Partner: UNT Libraries Government Documents Department

A combined saline formation and gas reservoir CO2 injection pilotin Northern California

Description: A geologic sequestration pilot in the Thornton gas field in Northern California, USA involves injection of up to 4000 tons of CO{sub 2} into a stacked gas and saline formation reservoir. Lawrence Berkeley National Laboratory (LBNL) is leading the pilot test in collaboration with Rosetta Resources, Inc. and Calpine Corporation under the auspices of the U.S. Department of Energy and California Energy Commission's WESTCARB, Regional Carbon Sequestration Partnership. The goals of the pilot include: (1) Demonstrate the feasibility of CO{sub 2} storage in saline formations representative of major geologic sinks in California; (2) Test the feasibility of Enhanced Gas Recovery associated with the early stages of a CO{sub 2} storage project in a depleting gas field; (3) Obtain site-specific information to improve capacity estimation, risk assessment, and performance prediction; (4) Demonstrate and test methods for monitoring CO{sub 2} storage in saline formations and storage/enhanced recovery projects in gas fields; and (5) Gain experience with regulatory permitting and public outreach associated with CO{sub 2} storage in California. Test design is currently underway and field work begins in August 2006.
Date: April 28, 2006
Creator: Trautz, Robert; Myer, Larry; Benson, Sally; Oldenburg, Curt; Daley, Thomas & Seeman, Ed
Partner: UNT Libraries Government Documents Department

Comparing Price Forecast Accuracy of Natural Gas Models andFutures Markets

Description: The purpose of this article is to compare the accuracy of forecasts for natural gas prices as reported by the Energy Information Administration's Short-Term Energy Outlook (STEO) and the futures market for the period from 1998 to 2003. The analysis tabulates the existing data and develops a statistical comparison of the error between STEO and U.S. wellhead natural gas prices and between Henry Hub and U.S. wellhead spot prices. The results indicate that, on average, Henry Hub is a better predictor of natural gas prices with an average error of 0.23 and a standard deviation of 1.22 than STEO with an average error of -0.52 and a standard deviation of 1.36. This analysis suggests that as the futures market continues to report longer forward prices (currently out to five years), it may be of interest to economic modelers to compare the accuracy of their models to the futures market. The authors would especially like to thank Doug Hale of the Energy Information Administration for supporting and reviewing this work.
Date: June 30, 2005
Creator: Wong-Parodi, Gabrielle; Dale, Larry & Lekov, Alex
Partner: UNT Libraries Government Documents Department

Balancing Cost and Risk: The Treatment of Renewable Energy inWestern Utility Resource Plans

Description: Markets for renewable electricity have grown significantly in recent years, motivated in part by federal tax incentives and in part by state renewables portfolio standards and renewable energy funds. State renewables portfolio standards, for example, motivated approximately 45% of the 4,300 MW of wind power installed in the U.S. from 2001 through 2004, while renewable energy funds supported an additional 15% of these installations. Despite the importance of these state policies, a less widely recognized driver for renewable energy market growth is poised to also play an important role in the coming years: utility integrated resource planning (IRP). Formal resource planning processes have re-emerged in recent years as an important tool for utilities and regulators, particularly in regions where retail competition has failed to take root. In the western United States, recent resource plans contemplate a significant amount of renewable energy additions. These planned additions - primarily coming from wind power - are motivated by the improved economics of wind power, a growing acceptance of wind by electric utilities, and an increasing recognition of the inherent risks (e.g., natural gas price risk, environmental compliance risk) in fossil-based generation portfolios. The treatment of renewable energy in utility resource plans is not uniform, however. Assumptions about the direct and indirect costs of renewable resources, as well as resource availability, differ, as do approaches to incorporating such resources into the candidate portfolios that are analyzed in utility IRPs. The treatment of natural gas price risk, as well as the risk of future environmental regulations, also varies substantially. How utilities balance expected portfolio cost versus risk in selecting a preferred portfolio also differs. Each of these variables may have a substantial effect on the degree to which renewable energy contributes to the preferred portfolio of each utility IRP. This article, which is based on ...
Date: September 1, 2005
Creator: Wiser, Ryan & Bolinger, Mark
Partner: UNT Libraries Government Documents Department

Health, Safety, and Environmental Screening and Ranking Frameworkfor Geologic CO2 Storage Site Selection

Description: This report describes a screening and ranking framework(SRF) developed to evaluate potential geologic carbon dioxide (CO2)storage sites on the basis of health, safety, and environmental (HSE)risk arising from possible CO2 leakage. The approach is based on theassumption that HSE risk due to CO2 leakage is dependent on three basiccharacteristics of a geologic CO2 storage site: (1) the potential forprimary containment by the target formation, (2) the potential forsecondary containment if the primary formation leaks, and (3) thepotential for attenuation and dispersion of leaking CO2 if the primaryformation leaks and secondary containment fails. The framework isimplemented in a spreadsheet in which users enter numerical scoresrepresenting expert opinions or general information available frompublished materials along with estimates of uncertainty to evaluate thethree basic characteristics in order to screen and rank candidate sites.Application of the framework to the Rio Vista Gas Field, Ventura OilField, and Mammoth Mountain demonstrates the approach. Refinements andextensions are possible through the use of more detailed data or modelresults in place of property proxies. Revisions and extensions to improvethe approach are anticipated in the near future as it is used and testedby colleagues and collaborators.
Date: March 15, 2006
Creator: Oldenburg, Curtis M.
Partner: UNT Libraries Government Documents Department

Joule-Thomson Cooling Due to CO2 Injection into Natural GasReservoirs

Description: Depleted natural gas reservoirs are a promising target for Carbon Sequestration with Enhanced Gas Recovery (CSEGR). The focus of this study is on evaluating the importance of Joule-Thomson cooling during CO2 injection into depleted natural gas reservoirs. Joule-Thomson cooling is the adiabatic cooling that accompanies the expansion of a real gas. If Joule-Thomson cooling were extreme, injectivity and formation permeability could be altered by the freezing of residual water,formation of hydrates, and fracturing due to thermal stresses. The TOUGH2/EOS7C module for CO2-CH4-H2O mixtures is used as the simulation analysis tool. For verification of EOS7C, the classic Joule-Thomson expansion experiment is modeled for pure CO2 resulting in Joule-Thomson coefficients in agreement with standard references to within 5-7 percent. For demonstration purposes, CO2 injection at constant pressure and with a large pressure drop ({approx}50 bars) is presented in order to show that cooling by more than 20 C can occur by this effect. Two more-realistic constant-rate injection cases show that for typical systems in the Sacramento Valley, California, the Joule-Thomson cooling effect is minimal. This simulation study shows that for constant-rate injections into high-permeability reservoirs, the Joule-Thomson cooling effect is not expected to create significant problems for CSEGR.
Date: April 21, 2006
Creator: Oldenburg, Curtis M.
Partner: UNT Libraries Government Documents Department

The Rosetta Resources CO2 Storage Project - A WESTCARB GeologicPilot Test

Description: WESTCARB, one of seven U.S. Department of Energypartnerships, identified (during its Phase I study) over 600 gigatonnesof CO2 storage capacity in geologic formations located in the Westernregion. The Western region includes the WESTCARB partnership states ofAlaska, Arizona, California, Nevada, Oregon and Washington and theCanadian province of British Columbia. The WESTCARB Phase II study iscurrently under way, featuring three geologic and two terrestrial CO2pilot projects designed to test promising sequestration technologies atsites broadly representative of the region's largest potential carbonsinks. This paper focuses on two of the geologic pilot studies plannedfor Phase II -referred to-collectively as the Rosetta-Calpine CO2 StorageProject. The first pilot test will demonstrate injection of CO2 into asaline formation beneath a depleted gas reservoir. The second test willgather data for assessing CO2 enhanced gas recovery (EGR) as well asstorage in a depleted gas reservoir. The benefit of enhanced oil recovery(EOR) using injected CO2 to drive or sweep oil from the reservoir towarda production well is well known. EaR involves a similar CO2 injectionprocess, but has received far less attention. Depleted natural gasreservoirs still contain methane; therefore, CO2 injection may enhancemethane production by reservoir repressurization or pressure maintenance.CO2 injection into a saline formation, followed by injection into adepleted natural gas reservoir, is currently scheduled to start inOctober 2006.
Date: January 30, 2006
Creator: Trautz, Robert; Benson, Sally; Myer, Larry; Oldenburg, Curtis; Seeman, Ed; Hadsell, Eric et al.
Partner: UNT Libraries Government Documents Department

Active Control for Statistically Stationary Turbulent PremixedFlame Simulations

Description: The speed of propagation of a premixed turbulent flame correlates with the intensity of the turbulence encountered by the flame. One consequence of this property is that premixed flames in both laboratory experiments and practical combustors require some type of stabilization mechanism to prevent blow-off and flashback. The stabilization devices often introduce a level of geometric complexity that is prohibitive for detailed computational studies of turbulent flame dynamics. Furthermore, the stabilization introduces additional fluid mechanical complexity into the overall combustion process that can complicate the analysis of fundamental flame properties. To circumvent these difficulties we introduce a feedback control algorithm that allows us to computationally stabilize a turbulent premixed flame in a simple geometric configuration. For the simulations, we specify turbulent inflow conditions and dynamically adjust the integrated fueling rate to control the mean location of the flame in the domain. We outline the numerical procedure, and illustrate the behavior of the control algorithm on methane flames at various equivalence ratios in two dimensions. The simulation data are used to study the local variation in the speed of propagation due to flame surface curvature.
Date: August 30, 2005
Creator: Bell, J.B.; Day, M.S.; Grcar, J.F. & Lijewski, M.J.
Partner: UNT Libraries Government Documents Department

Accounting for fuel price risk when comparing renewable togas-fired generation: the role of forward natural gas prices

Description: Unlike natural gas-fired generation, renewable generation (e.g., from wind, solar, and geothermal power) is largely immune to fuel price risk. If ratepayers are rational and value long-term price stability, then--contrary to common practice--any comparison of the levelized cost of renewable to gas-fired generation should be based on a hedged gas price input, rather than an uncertain gas price forecast. This paper compares natural gas prices that can be locked in through futures, swaps, and physical supply contracts to contemporaneous long-term forecasts of spot gas prices. We find that from 2000-2003, forward gas prices for terms of 2-10 years have been considerably higher than most contemporaneous long-term gas price forecasts. This difference is striking, and implies that comparisons between renewable and gas-fired generation based on these forecasts over this period have arguably yielded results that are biased in favor of gas-fired generation.
Date: July 17, 2004
Creator: Bolinger, Mark; Wiser, Ryan & Golove, William
Partner: UNT Libraries Government Documents Department

Sequestration of CO2 in the Altmark natural gas field, Germany:Mobility control to extend enhanced gas recovery

Description: We are investigating the technical feasibility of injecting CO2 for carbon sequestration with enhanced gas recovery (CSEGR) in the depleted Altmark natural gas reservoir, Germany. Our approach is numerical simulation using TOUGH2/EOS7C. Our earlier simulation studies have shown early CO2 breakthrough due to fast-flow through the high-permeability sand layers. In order to extend the period of enhanced CH4 recovery, we propose the preinjection of gelling fluids for the purpose of limiting the mobility of injected CO2 and thereby improving CO2 sweep and delaying CO2 breakthrough. We have implemented a simple gel model into EOS7C and simulated gel injection followed by CSEGR.Preliminary simulations to date show minimal improvements in CSEGR with breakthrough times delayed by only a few months to a year. While mobility control using pre-injected gelling fluids appears to be a promising strategy in controlling early breakthrough, more work is needed to design and simulate an effective procedure.
Date: April 21, 2006
Creator: Rebscher, D.; May, F. & Oldenburg, C.M.
Partner: UNT Libraries Government Documents Department

Electricity and Natural Gas Efficiency Improvements forResidential Gas Furnaces in the U.S.

Description: This paper presents analysis of the life-cycle costs for individual households and the aggregate energy and economic impacts from potential energy efficiency improvements in U.S. residential furnaces. Most homes in the US are heated by a central furnace attached to ducts for distributing heated air and fueled by natural gas. Electricity consumption by a furnace blower is significant, comparable to the annual electricity consumption of a major appliance. Since the same blower unit is also used during the summer to circulate cooled air in centrally air conditioned homes, electricity savings occur year round. Estimates are provided of the potential electricity savings from more efficient fans and motors. Current regulations require new residential gas-fired furnaces (not including mobile home furnaces) to meet or exceed 78 percent annual fuel utilization efficiency (AFUE), but in fact nearly all furnaces sold are at 80 percent AFUE or higher. The possibilities for higher fuel efficiency fall into two groups: more efficient non-condensing furnaces (81 percent AFUE) and condensing furnaces (90-96 percent AFUE). There are also options to increase the efficiency of the furnace blower. This paper reports the projected national energy and economic impacts of requiring higher efficiency furnaces in the future. Energy savings vary with climate, with the result that condensing furnaces offer larger energy savings in colder climates. The range of impacts for a statistical sample of households and the percent of households with net savings in life cycle cost are shown. Gas furnaces are somewhat unusual in that the technology does not easily permit incremental change to the AFUE above 80 percent. Achieving significant energy savings requires use of condensing technology, which yields a large efficiency gain (to 90 percent or higher AFUE), but has a higher cost. With respect to electricity efficiency design options, the ECM has a negative effect on ...
Date: May 26, 2006
Creator: Lekov, Alex; Franco, Victor; Meyers, Steve; McMahon, James E.; McNeil, Michael & Lutz, Jim
Partner: UNT Libraries Government Documents Department

Depressurization-induced gas production from Class 1 and Class 2hydrate deposits

Description: Class 1 hydrate deposits are characterized by a Hydrate-Bearing Layer (HBL) underlain by a two-phase zone involving mobile gas. Such deposits are further divided to Class 1W (involving water and hydrate in the HBL) and Class 1G (involving gas and hydrate in the HBL). In Class 2 deposits, a mobile water zone underlies the hydrate zone. Methane is the main hydrate-forming gas in natural accumulations. Using TOUGH-FX/HYDRATE to study the depressurization-induced gas production from such deposits, we determine that large volumes of gas could be readily produced at high rates for long times using conventional technology. Dissociation in Class 1W deposits proceeds in distinct stages, but is continuous in Class 1G deposits. Hydrates are shown to contribute significantly to the production rate (up to 65 percent and 75 percent in Class 1W and 1G, respectively) and to the cumulative volume of produced gas (up to 45 percent and 54 percent in Class 1W and 1G, respectively). Large volumes of hydrate-originating CH4 could be produced from Class 2 hydrates, but a relatively long lead time would be needed before gas production (which continuously increases over time) attains a substantial level. The permeability of the confining boundaries plays a significant role in gas production from Class 2 deposits. In general, long-term production is needed to realize the full potential of the very promising Class 1 and Class 2 hydrate deposits.
Date: May 12, 2006
Creator: Moridis, George J. & Kowalsky, Michael
Partner: UNT Libraries Government Documents Department

Exact solutions in a model of vertical gas migration

Description: This work is motivated by the growing interest in injectingcarbon dioxide into deep geological formations as a means of avoidingatmospheric emissions of carbon dioxide and consequent global warming.One of the key questions regarding the feasibility of this technology isthe potential rate of leakage out of the primary storage formation. Weseek exact solutions in a model of gas flow driven by a combination ofbuoyancy, viscous and capillary forces. Different combinations of theseforces and characteristic length scales of the processes lead todifferent time scaling and different types of solutions. In the case of athin, tight seal, where the impact of gravity is negligible relative tocapillary and viscous forces, a Ryzhik-type solution implies square-rootof time scaling of plume propagation velocity. In the general case, a gasplume has two stable zones, which can be described by travelling-wavesolutions. The theoretical maximum of the velocity of plume migrationprovides a conservative estimate for the time of vertical migration.Although the top of the plume has low gas saturation, it propagates witha velocity close to the theoretical maximum. The bottom of the plumeflows significantly more slowly at a higher gas saturation. Due to localheterogeneities, the plume can break into parts. Individual plumes alsocan coalesce and from larger plumes. The analytical results are appliedto studying carbon dioxide flow caused by leaks from deep geologicalformations used for CO2 storage. The results are also applicable formodeling flow of natural gas leaking from seasonal gas storage, or formodeling of secondary hydrocarbon migration.
Date: June 27, 2006
Creator: Silin, Dmitriy B.; Patzek, Tad W. & Benson, Sally M.
Partner: UNT Libraries Government Documents Department

Geologic Storage of Greenhouse Gases: Multiphase andNon-isothermal Effects, and Implications for Leakage Behavior

Description: Storage of greenhouse gases, primarily CO2, in geologic formations has been proposed as a means by which atmospheric emissions of such gases may be reduced (Bachu et al., 1994; Orr, 2004). Possible storage reservoirs currently under consideration include saline aquifers, depleted or depleting oil and gas fields, and unmineable coal seams (Baines and Worden, 2004). The amount of CO2 emitted from fossil-fueled power plants is very large, of the order of 30,000 tons per day (10 million tons per year) for a large 1,000 MW coal-fired plant (Hitchon,1996). In order to make a significant impact on reducing emissions, very large amounts of CO2 would have to be injected into subsurface formations, resulting in CO2 disposal plumes with an areal extent of order 100 km2 or more (Pruess et al., 2003). It appears inevitable, then, that such plumes will encounter imperfections in caprocks, such as fracture zones or faults, that would allow CO2 to leak from the primary storage reservoir. At typical subsurface conditions of temperature and pressure, CO2 is always less dense than aqueous fluids; thus buoyancy forces will tend to drive CO2 upward, towards the land surface, whenever adequate (sub-)vertical permeability is available. Upward migration of CO2 could also occur along wells, including pre-existing wells in sedimentary basins where oil and gas exploration and production may have been conducted (Celia et al., 2004), or along wells drilled as part of a CO2 storage operation. Concerns with leakage of CO2 from a geologic storage reservoir include (1) keeping the CO2 contained and out of the atmosphere, (2) avoiding CO2 entering groundwater aquifers, (3)asphyxiation hazard if CO2 is released at the land surface, and (4) the possibility of a self-enhancing runaway discharge, that may culminate in a ''pneumatic eruption'' (Giggenbach et al., 1991). The manner in which CO2 may leak from ...
Date: August 5, 2005
Creator: Pruess, Karsten
Partner: UNT Libraries Government Documents Department

Comparison of kinetic and equilibrium reaction models insimulating gas hydrate behavior in porous media

Description: In this study we compare the use of kinetic and equilibriumreaction models in the simulation of gas (methane) hydrate behavior inporous media. Our objective is to evaluate through numerical simulationthe importance of employing kinetic versus equilibrium reaction modelsfor predicting the response of hydrate-bearing systems to externalstimuli, such as changes in pressure and temperature. Specifically, we(1) analyze and compare the responses simulated using both reactionmodels for natural gas production from hydrates in various settings andfor the case of depressurization in a hydrate-bearing core duringextraction; and (2) examine the sensitivity to factors such as initialhydrate saturation, hydrate reaction surface area, and numericaldiscretization. We find that for large-scale systems undergoing thermalstimulation and depressurization, the calculated responses for bothreaction models are remarkably similar, though some differences areobserved at early times. However, for modeling short-term processes, suchas the rapid recovery of a hydrate-bearing core, kinetic limitations canbe important, and neglecting them may lead to significantunder-prediction of recoverable hydrate. The use of the equilibriumreaction model often appears to be justified and preferred for simulatingthe behavior of gas hydrates, given that the computational demands forthe kinetic reaction model far exceed those for the equilibrium reactionmodel.
Date: November 29, 2006
Creator: Kowalsky, Michael B. & Moridis, George J.
Partner: UNT Libraries Government Documents Department