Natural Gas Distribution Systems Research Articles

Thermodynamic analysis of a novel pumped thermal energy storage system utilizing ambient thermal energy and LNG cold energy

Pumped thermal energy storage (PTES) has become a hot topic on large scale energy storage technology because of the independence on geological conditions and fossil fuels. However, few of the PTES systems have higher round trip efficiencies compared with that of pumped hydro storage except for systems utilizing external heat sources. Furthermore, the used external heat sources are not available everywhere and much additional cost is required for the system integration. As an accessible and cheap heat source, ambient thermal energy is employed in the newly proposed PTES system. LNG (liquid natural gas) cold energy is also used as the heat sink based on possible combination with the natural gas distribution system in the practical operation. The charge process is based on transcritical CO2 heat pump cycle, while cascade design of transcritical CO2 Rankine cycle and subcritical NH3 Rankine cycle is employed in the discharge process. A thermodynamic model is established for energy and exergy analysis as well as the system evaluation. The analysis and evaluation of the optimized baseline case obtained by Genetic Algorithm are then carried out. In addition, the sensitivity of system performance to different variable parameters is also analyzed. Based on the analysis of optimized baseline case, the round trip efficiency can reach 139%. If for 1MW net power output, both of the mass flow rates of CO2 and NH3 are 7.4kg/s with LNG mass flow rate of 14.8kg/s. Because of much higher round trip efficiency compared with other large scale energy storage systems, the proposed system is promising for future development and applications.

A chance constrained programming approach to integrated planning of distributed power generation and natural gas network

The growing integration of distributed electric power generators means the reliability of electricity distribution systems will increasingly depend on the reliability of primary energy resources such as natural gas supply for natural gas-fired distributed power generation. This, therefore, necessitates an integrated approach for planning both the electricity and natural gas distribution systems for the purpose of ensuring reliable natural gas supply for electricity generation. We propose a probabilistic planning approach based on the chance constrained programming method for planning these two systems in the presence of uncertain real and reactive power demand. The proposed model minimizes the investment cost of gas-fired generators, natural gas pipeline and the operation cost of the natural gas-fired distributed generators over a long-term planning horizon. The proposed integrated planning approach is used to develop a 10 years long-term plan for 9 and 33 bus distribution systems. The result shows that the integrated planning approach results in a cheaper and more reliable system in comparison with a traditional sequential planning approach.

Strategy selection model for development of natural gas distribution systems based on AHP/DEA methodologies

Strategy selection model for development of natural gas distribution systems based on AHP/DEA methodologies

Locate Fugitive Methane Emission from Compressor Station of Natural Gas Transmission and Distribution System for Reducing Environmental Risk

Locate Fugitive Methane Emission from Compressor Station of Natural Gas Transmission and Distribution System for Reducing Environmental Risk

Locate Fugitive Methane Emission from Compressor Station of Natural Gas Transmission and Distribution System for Reducing Environmental Risk

Locate Fugitive Methane Emission from Compressor Station of Natural Gas Transmission and Distribution System for Reducing Environmental Risk

Optimal Expansion Co-Planning of Reconfigurable Electricity and Natural Gas Distribution Systems Incorporating Energy Hubs

In a carbon-constrained world, natural gas with low emission intensity plays an important role in the energy consumption area. Energy consumers and distribution networks are linked via energy hubs. Meanwhile, reconfiguration that optimizes operational performance while maintaining a radial network topology is a worldwide technique in the electricity distribution system. To improve the overall efficiency of energy infrastructure, the expansion of electricity distribution lines and elements within energy hubs should be co-planned. In this paper, the co-planning process is modeled as a mixed integer quadratic programming problem to handle conflicting objectives simultaneously. We propose a novel model to identify the optimal co-expansion plan in terms of total cost. Operational factors including energy storages and reconfiguration are considered within the systems to serve electricity, cooling and heating loads. Reconfiguration and elements in energy hubs can avoid or defer new elements’ installation to minimize the investment cost, maintenance cost, operation cost, and interruption cost in the planning horizon. The proposed co-planning approach is verified on 3 and 12-node electricity and natural gas distribution systems coupled via energy hubs. Numerical results show the ability of our proposed expansion co-planning approach based on energy hub in meeting energy demand.

On Methane Leaks from Pipelines in Bryan and College Station, Texas, USA

Methane is the second most important anthropogenically emitted greenhouse gas after carbon dioxide. Anthropogenic methane sources in the US are dominated by emissions from domestic ruminants and from fossil fuel exploration, storage and transmission. The fossil fuel source is primarily due to natural gas leaks along the production to distribution chain, and pipeline leaks in urban areas have been identified as a significant contributor. In this study, we evaluated possible leaks in three neighborhoods of a midsize Texas metropolitan region surrounding Texas A&M University through mobile measurements using a fast response, high precision methane analyzer. Neighborhoods were selected by age and land use, and each predetermined driving route was evaluated three times. Methane spikes exceeding 2.5 ppm were identified as leaks, and approximately one leak per mile of urban road was discovered. The largest leaks were found around the Texas A&M natural gas plant and in the oldest neighborhood to its north, while fewer leaks were found in a slightly younger neighborhood. No leaks were found in the youngest, less than 20-year old neighborhood suggesting that pipeline system age is a strong determinant of current and future leaks from the natural gas distribution system.

Direct and Indirect Measurements and Modeling of Methane Emissions in Indianapolis, Indiana.

This paper describes process-based estimation of CH4 emissions from sources in Indianapolis, IN and compares these with atmospheric inferences of whole city emissions. Emissions from the natural gas distribution system were estimated from measurements at metering and regulating stations and from pipeline leaks. Tracer methods and inverse plume modeling were used to estimate emissions from the major landfill and wastewater treatment plant. These direct source measurements informed the compilation of a methane emission inventory for the city equal to 29 Gg/yr (5% to 95% confidence limits, 15 to 54 Gg/yr). Emission estimates for the whole city based on an aircraft mass balance method and from inverse modeling of CH4 tower observations were 41 ± 12 Gg/yr and 81 ± 11 Gg/yr, respectively. Footprint modeling using 11 days of ethane/methane tower data indicated that landfills, wastewater treatment, wetlands, and other biological sources contribute 48% while natural gas usage and other fossil fuel sources contribute 52% of the city total. With the biogenic CH4 emissions omitted, the top-down estimates are 3.5-6.9 times the nonbiogenic city inventory. Mobile mapping of CH4 concentrations showed low level enhancement of CH4 throughout the city reflecting diffuse natural gas leakage and downstream usage as possible sources for the missing residual in the inventory.

Geography And The Capital Investment Costs Of Urban Energy Infrastructure: The Case Of Electricity And Natural Gas Networks

Urban infrastructures are characterized by considerably high investment costs, which make investments almost irreversible. Once the construction is completed, it is difficult and expensive to modify the systems. Therefore a detailed cost analysis should be carried out in advance, to prevent unprecedented future charges and provide reliable infrastructure services. This study aims to reveal the economic characteristics of urban energy (electricity and natural gas) distribution systems’ investment costs using (1) capital investment costs at the local level; (2) outputs such as sectoral numbers of customers and energy sales, and input prices; (3) company-specific characteristics of energy distribution firms; and (4) socio-economic and site-specific urban and geographic variables. However, the fourth group variables have often been neglected in the literature, although the impacts of such variables are expected to be highly relevant. In this study, an econometric approach has been utilized for cost analysis. Regression models tested both log-log and the Box-Cox forms, while the Box-Cox regression model, as a flexible form allowing for the endogenous determination of the parameters, gave better results. Regression estimates show that besides the output and input variables, and company-specific variables, socio-economic and site-specific urban and geographic variables have statistically significant effects on electricity and natural gas distribution capital investment costs. Moreover the results provide evidence for economies of scale and density in these distribution systems under various configurations of market size and local conditions.

Direct Measurements Show Decreasing Methane Emissions from Natural Gas Local Distribution Systems in the United States

Fugitive losses from natural gas distribution systems are a significant source of anthropogenic methane. Here, we report on a national sampling program to measure methane emissions from 13 urban distribution systems across the U.S. Emission factors were derived from direct measurements at 230 underground pipeline leaks and 229 metering and regulating facilities using stratified random sampling. When these new emission factors are combined with estimates for customer meters, maintenance, and upsets, and current pipeline miles and numbers of facilities, the total estimate is 393 Gg/yr with a 95% upper confidence limit of 854 Gg/yr (0.10% to 0.22% of the methane delivered nationwide). This fraction includes emissions from city gates to the customer meter, but does not include other urban sources or those downstream of customer meters. The upper confidence limit accounts for the skewed distribution of measurements, where a few large emitters accounted for most of the emissions. This emission estimate is 36% to 70% less than the 2011 EPA inventory, (based largely on 1990s emission data), and reflects significant upgrades at metering and regulating stations, improvements in leak detection and maintenance activities, as well as potential effects from differences in methodologies between the two studies.

Odor fading in natural gas distribution systems

Since natural gas is odorless, to assure the customer safety, odorants are added to it to alarm the consumer in the case of a gas leak. Although the odorization is a common practice in natural gas distribution systems, odor fading has been reported in pipelines, which is a great safety risk. This paper summarizes results of experiments conducted to investigate possible chemical and physical mechanisms responsible for odor fading. In these experiments, X-ray photoelectron spectroscopy (XPS) and gas chromatography were used to check the possible interactions of tertiary butyl mercaptan (TBM) as odorant with the pipe material. Evidences of chemisorption, adsorption and desorption of TBM on the iron oxide inside the pipe were observed. It was found that by increasing pressure, rusted surface of the pipe, and temperature or by decreasing the gas flow rate and odorant concentration the mercaptan removal was increased.

Quantification and source apportionment of the methane emission flux from the city of Indianapolis

Abstract We report the CH4 emission flux from the city of Indianapolis, IN, the site of the Indianapolis Flux Experiment (INFLUX) project for developing, assessing, and improving top-down and bottom-up approaches for quantifying urban greenhouse gas emissions. Using an aircraft-based mass balance approach, we find that the average CH4 emission rate from five flight experiments in 2011 is 135 ± 58 (1σ) moles s-1 (7800 ± 3300 kg hr-1). The effective per capita CH4 emission rate for Indianapolis is 77 kg CH4 person-1 yr-1, a figure that is less than the national anthropogenic CH4 emission (∼91 kg CH4 person-1 yr-1) but considerably larger than the global figure (∼48 kg CH4 person-1 yr-1). We consistently observed elevated CH4 concentrations at specific coordinates along our flight transects downwind of the city. Inflight investigations as well as back trajectories using measured wind directions showed that the elevated concentrations originated from the southwest side of the city where a landfill and a natural gas transmission regulating station (TRS) are located. Street level mobile measurements downwind of the landfill and the TRS supported the results of aircraft-based data, and were used to quantify the relative contributions from the two sources. We find that the CH4 emission from the TRS was negligible relative to the landfill, which was responsible for 33 ± 10% of the citywide emission flux. A regression of propane versus methane from aircraft flask samples suggests that the remaining citywide CH4 emissions (∼67%) derive from the natural gas distribution system. We discuss the combination of surface mobile observations and aircraft city-wide flux measurements to determine the total flux and apportionment to important sources.

Uniaxial Fatigue of HDPE-100 Pipe. Experimental Analysis

In this paper, an experimental analysis for determining the fatigue strength of PE-100, one of the most used High Density Polyethylene (HDPE) materials for pipes, under cyclic axial loadings is presented. HDPE is a thermoplastic material used for piping systems, such as natural gas distribution systems, sewer systems and cold water systems, which provides a good alternative to metals such as cast iron or carbon steel. One of the causes for failures of HDPE pipes is fatigue which is the result of pipes being subjected to cyclic loading, such as internal pressure, weight loads or external loadings on buried pipes, which generate stress in different directions: circumferential, longitudinal and radial. HDPE pipes are fabricated using an extrusion process, which generates anisotropic properties. By testing in the Laboratory a series of identical specimens obtained directly from PE-100 HDPE pipes in longitudinal directions, the relationships between amplitude stress and number of cycles (S-N curve) test frequency 2 Hz and stress ratio R = 0.0 are established.

Essential Work of Fracture Testing Method Applied to Medium Density Polyethylene

Thermoplastic polyethylene has been increasingly used in important structural applications, e.g., in the production of pipelines for water and natural gas distribution systems, leading to the growing interest in the characterization of the material's fracture toughness. By virtue of its high ductility at room temperature, elastic-plastic fracture toughness concepts are most convenient for this purpose. In this work, a systematic study about the suitability of Essential Work of Fracture (EWF) test protocol to a medium density polyethylene (MDPE) resin designed for water pipelines extrusion is carried out. The influence of test piece preparation and geometry, along with different pre-cracking methods are investigated and their effects on the obtained results are assessed. It has been concluded that EWF methodology is well applicable for the characterization of MDPE resin and the test parameters allow, for instance, the evaluation of process induced anisotropy effects in the sample and the ranking of in-service mechanical performance of different resin grades. It has also been shown that pre-cracking method, test coupon thickness and processing technology impact the obtained results within 5% statistical significance level and that ‘rougher’ pre-cracking methods affect negatively the test results by increasing data dispersion.

Modeling of Flow and Transport Induced by Production of Hydrofracture-Stimulated Gas Wells Near the Rulison Nuclear Test

The Project Rulison test in Western Colorado was conducted in 1969 to determine if a nuclear device could be used to fracture low permeability, gas-bearing rock to enhance natural gas production. The presence of radionuclides (specifically tritium) in the produced gas persisted above acceptable levels, and the test was abandoned. Advances in hydraulic fracturing technology have made it feasible to extract natural gas from low-permeability reservoirs, and drilling activity near the Rulison site has raised concerns that remnant radioactivity in the detonation zone could migrate to nearby producing wells and enter the natural gas distribution system. The site was modeled using the massively parallel version of TOUGH2, TOUGH2_MP-EOS7R, with over 1,000,000 elements. The majority of the tritium is present as tritiated water, and since the gas permeability of the native formation is several orders of magnitude higher than the liquid permeability, any significant migration occurs with the gas phase. In the model, tritium partitions between the aqueous and vapor phases in relation to the Henry’s Law constant. The Henry’s constant for tritiated water vapor is simply the water vapor pressure. The model domain includes the entire targeted gas-bearing section and gas production wells installed in 2010 1.2 km (0.75 mile) from the Rulison site. The model was calibrated to historical production and pressure data from the Rulison reentry well and to data from the recently installed gas wells. The model was used to simulate the effects of current wells and of future wells that could potentially be installed nearer the Rulison site.

Integrated Energy Resource Management Systems: Meeting the Information Needs of Evolving Markets

From the 1994 CAIS Conference: The Information Industry in Transition McGill University, Montreal, Quebec. May 25 - 27, 1994.Advanced information systems requirements are identified to achieve energy market efficiencies sought by regulators and market participants. Natural gas and electric energy distribution systems dependencies on the increasingly complex integration of information relating to scheduling, dispatch and operations monitoring are discussed.

A Holistic Approach for Planning Natural Gas and Electricity Distribution Networks

This paper presents a new planning expansion model of an electricity and natural gas distribution system that has high penetration of distributed generation based on natural gas. The model entails lower investment costs as compared to traditional planning models that consider both systems (electricity and natural gas) as independent networks. This model is especially convenient for utilities that own both systems, as electricity and natural gas customers can derive benefits (via electricity or natural gas tariffs) if there are significant savings in investment costs. For fast-growing economies, the merging of electricity and natural gas distribution systems is seen as a promising business opportunity in which economies of scope can have lower investment costs, so there is a definite need for this type of approach.

Assessment Procedure of Technological Consumption in the Natural Gas Distribution Systems

This paper proposes a procedure of calculus of the technological consumption, usefully for the operators of the natural gas distribution systems. It also sets, based on a statistical study, the minimum possible value of the technological consumption for the operators of natural gas distribution in Romania. There are indicated the environmental issues resulting from the technological consumption and the measures to control and reduce it.

Computational tool for material balances control in natural gas distribution network

In natural gas industry, measurement of process variables allows to assess the quantity and quality of commercialized gas. Nevertheless, since errors, gross and random are always present in measurements, mass and energy balances are not satisfied. This situation leads natural gas distribution companies into invoicing issues. In this paper, a computational tool is proposed, which guarantees that the law of conservation of mass is obeyed by decreasing random error effects and detecting systematic deviations in the measurement equipment (gross errors). This tool is based on Data Reconciliation (DR) and Gross Error Detection (GED) techniques. Different DR and GED methodologies were studied by means of assessment of their advantages and disadvantages. Non-conventional DR and GED methods are proposed as part of the developed tool in order to obtain accurate reconciled results in cases of difficult gross error detections on natural gas distribution systems. The tool was validated by a typical literature problem, and it was then applied to a natural gas distribution network. Results were in agreement with reports of failures of some instruments.

Mapping urban pipeline leaks: Methane leaks across Boston

Natural gas is the largest source of anthropogenic emissions of methane (CH4) in the United States. To assess pipeline emissions across a major city, we mapped CH4 leaks across all 785 road miles in the city of Boston using a cavity-ring-down mobile CH4 analyzer. We identified 3356 CH4 leaks with concentrations exceeding up to 15 times the global background level. Separately, we measured δ13CH4 isotopic signatures from a subset of these leaks. The δ13CH4 signatures (mean = −42.8‰ ± 1.3‰ s.e.; n = 32) strongly indicate a fossil fuel source rather than a biogenic source for most of the leaks; natural gas sampled across the city had average δ13CH4 values of −36.8‰ (±0.7‰ s.e., n = 10), whereas CH4 collected from landfill sites, wetlands, and sewer systems had δ13CH4 signatures ∼20‰ lighter (μ = −57.8‰, ±1.6‰ s.e., n = 8). Repairing leaky natural gas distribution systems will reduce greenhouse gas emissions, increase consumer health and safety, and save money.