Natural Gas Transmission Network Research Articles

Convex Relaxations of Maximal Load Delivery for Multi-Contingency Analysis of Joint Electric Power and Natural Gas Transmission Networks

Recent increases in gas-fired power generation have engendered increased interdependencies between natural gas and power transmission systems. These interdependencies have amplified existing vulnerabilities in gas and power grids, where disruptions can require the curtailment of load in one or both systems. Although typically operated independently, coordination of these systems during severe disruptions can allow for targeted delivery to lifeline services, including gas delivery for residential heating and power delivery for critical facilities. To address the challenge of estimating maximum joint network capacities under such disruptions, we consider the task of determining feasible steady-state operating points for severely damaged systems while ensuring the maximal delivery of gas and power loads simultaneously, represented mathematically as the nonconvex joint Maximal Load Delivery (MLD) problem. To increase its tractability, we present a mixed-integer convex relaxation of the MLD problem. Then, to demonstrate the relaxation’s effectiveness in determining bounds on network capacities, exact and relaxed MLD formulations are compared across various multi-contingency scenarios on nine joint networks ranging in size from 25 to 1191 nodes. The relaxation-based methodology is observed to accurately and efficiently estimate the impacts of severe joint network disruptions, often converging to the relaxed MLD problem’s globally optimal solution within ten seconds.

Regional Planning for Just and Reasonable Rates

Natural gas—a fuel used for electricity generation, heating, and transportation—plays an outsized role in the U.S. economy. Under the Natural Gas Act, the Federal Energy Regulatory Commission (FERC or the Commission) is responsible for overseeing the orderly development of interstate natural gas pipelines, which facilitate the transmission of natural gas throughout the country. Before a developer can construct or expand an interstate pipeline, it must apply to FERC for authoriza-tion; FERC can approve the pipeline only if it finds that it is required by the “public convenience and necessity.” Although FERC should consid-er a range of factors to determine whether a pipeline will serve the public interest, in practice, it looks primarily to the existence of prece-dent agreements, i.e., contracts between a developer and its customers for the purchase of pipeline capacity. If a developer can demonstrate that there is a party willing to pay to use its pipeline, FERC rarely asks questions and almost always finds “public” need. In this way, the natu-ral gas transmission network has developed through a system of ad hoc decisionmaking organized around the needs of private companies that earn a hefty return on their capital investments.
 This pipeline-by-pipeline approach to natural gas transmission build-out leads to the construction of unnecessary, underused pipe-lines, which in turn increases ratepayer costs and decreases consumer welfare. Climate change further increases the risk that pipelines will become obsolete as cities and states move toward electrification. Fur-thermore, the gas transmission planning process—or lack thereof—stands in stark contrast to electric transmission planning, an activity that FERC also regulates but that is conducted by centralized entities on a regional scale. This contrast is especially confounding consider-ing that electric transmission is regulated under the Federal Power Act, a sister law to the Natural Gas Act with similar statutory require-ments.
 Relying on economic theory, legal history, and policy analysis, we make the case for FERC’s adoption of regional gas transmission plan-ning. We begin by describing the status quo and articulating why FERC’s current process is economically inefficient. In doing so, we draw parallels between gas and electric transmission planning and de-scribe how FERC treats the two activities inconsistently. We then ex-plain why, under two provisions of the Natural Gas Act, FERC possesses both the legal authority and obligation to require regional planning. Finally, we envision how FERC might conduct gas transmission plan-ning going forward, encouraging FERC to account for increasing elec-trification efforts and to plan for gas and electric transmission in tan-dem.

Generator Start-Up Strategy for Power System Restoration Considering Interdependency With Natural Gas Transmission Network

Generator Start-Up Strategy for Power System Restoration Considering Interdependency With Natural Gas Transmission Network

Simultaneous multi-objective framework of natural gas pipeline network operations

The optimization of gas transportation networks is essential as natural gas demand increases. Conflicting objectives, such as maximizing delivery flow rate, minimizing power consumption, and maximizing line pack, pose challenges in this context. To address these complexities, a novel multi-objective optimization method based on the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) is proposed. The method generates a diverse set of Pareto optimal solutions, empowering decision-makers to select the most suitable solution for gas transportation networks. Three case studies validate the approach's effectiveness, showcasing its advantages in yielding more economical networks and enhancing the cost-effectiveness of natural gas transmission networks. The proposed method's versatility allows application to various gas transportation network scenarios. Decision-makers benefit from a range of Pareto optimal solutions, providing valuable insights. Moreover, the seamless integration of the proposed method into existing gas transportation network optimization frameworks further enhances performance. In conclusion, the study presents a robust multi-objective optimization method based on TOPSIS for gas transportation network optimization. It offers cost-effective solutions and improves the efficiency of natural gas transmission networks. The provision of diverse Pareto optimal solutions enables well-informed decision-making, contributing to sustainable energy solutions in the face of increasing natural gas demand.

Analysis of the Policy of Moving the National Capital (IKN) with an Energy Increase Strategy: Readiness of Economic and Public Administration Aspects

This article examines the policy of moving the National Capital (IKN) from Jakarta Province to East Kalimantan Province with an energy improvement strategy based on readiness from economic and public administrative aspects. The theory used is agenda-setting theory with descriptive qualitative research methods. The results show that the policy analysis of moving IKN from Jakarta to East Kalimantan can be reviewed based on readiness in economic and public administrative factors. In public administration, the policy of moving IKN to East Kalimantan Province can adjust the concept of a smart city, green city, and international standard. East Kalimantan Province has a diverse economy, with small and medium-sized businesses, fishing, agriculture, plantations, mining, and services all present. Energy improvement strategies include building natural gas transmission networks, bolstering the electrical interconnection transmission network, building large-scale hydropower plants, building installations, and clean energy, and putting energy in place energy-efficient transportation systems. It can be used to optimize these economic aspects. The emission-free idea, the PLTS system's organization, and a public administration system based on technology and information are all necessary proposals to make it simpler for staff members to serve the community.

Effect of flow-rate measurement accuracy on unaccounted for gas in transmission networks

Unaccounted-for-Gas (UAG) in modern natural gas transmission networks is a very debated topic among researchers and network managers, since UAG significantly affects the physical and commercial balancing of the network itself. On the technical hand, UAG is caused by the unavoidable errors in measuring and estimating gas quantities in the network and it is either positive or negative. However significant and tendentially positive/negative UAG values often occur in modern networks and this can be ascribed to the rise of systematic errors. Furthermore, cyclic trends of UAG are often observed and the correlation with the accuracy of flow-rate measurements has not been adequately investigated, despite this latter is widely recognized as a crucial issue. In this paper, the rangeability faults of flow-meters installed at the interconnections with regional and city networks have been investigated, together with the effect of the drift of the instrument due to the lack of subsequent calibrations. From the analysis carried out, it was found that about 12% of the average daily flow-rates measured in a whole year at the exit points of the Italian network are below the minimum flow-rate of the flow-meter and that a significant correlation between monthly UAG and the number of flow-meter rangeability faults exists.

Effect of hydrogen blending on the energy capacity of natural gas transmission networks

In this paper the effects of hydrogen on the transport of natural gas-hydrogen mixture in a high-pressure natural gas transmission system are investigated in detail. Our research focuses on the decrease in transferable energy content under identical operating conditions as hydrogen is blended in the gas transmission network. Based on the extensive literature review the outstanding challenges and key questions of using hydrogen in the natural gas system are introduced. In our research the transmissible energy factor - TEF - is defined that quantifies the relative energy capacity of the pipeline caused by hydrogen blending. A new equation is proposed in this paper to find the value of TEF at specific pressure and temperature conditions for different hydrogen concentrations. This practical equation helps the natural gas system operators in the decision-making process when hydrogen emerges in the gas transmission system. In this paper the change of the compression power requirement, which increases significantly with hydrogen blending, is investigated in detail.

Techniques for Creating Synthetic Combined Electric and Natural Gas Transmission Grids

This paper presents a methodology for the creation of a synthetic combined electric and natural gas transmission network, along with representative benchmark results. The systems do not contain actual, confidential network data, but are synthetic, meaning they are built to capture the behavior of a combined network that is geographically constrained. First, natural gas loads are placed in a selected area. Work already done in building synthetic electric grids aids in this process, where the natural gas-powered generators are modeled as loads in the natural gas system. Publicly available data is then used to place the remaining gas loads and the gathering plant. Next, a method is introduced to construct a pipeline network connecting the loads and processing plant, which acts as the source. The combined electric-gas system is then solved for the nodal pressures, pipeline flow rates, and electric state variables. A 51-node gas test case with 49 pipes, 23 loads, 2 compressor stations and a loop is constructed and solved in combination with a 173-bus electric system, designed to aid with developing and validating analysis techniques for combined electric-gas systems.

Stochastic Simulation of Flow Rate and Power Consumption Considering the Uncertainty of Pipeline Cracking Rate and Time-Dependent Topology of a Natural Gas Transmission Network

Various gas pipeline networks used for the transit of energy sources are some of the most important infrastructures. However, carrying gas from one point to another is not the only concern when planning the construction of a new network or expanding an already existing one. The reliability and environmental impact of the system are crucial when evaluating the network and risks posed by potential gas leaks, fires, explosions, etc. Even though everyone admits that reliability is a key aspect of any system, its constraints will still be most likely neglected in the assessment of the pipeline project. How much energy is wasted by pushing an additional amount of gas through the pipeline network, which will eventually gush out of the pipeline because of one crack or another? Moreover, if this additional power or fuel consumption and related environmental impact are significant, how could it be reduced? In this paper, an approach is introduced for the simulation and quantification of how much more power would be required if the pipelines are regarded as unreliable (i.e., by leaking, rupturing, or even exploding). By employing stochastic simulations and time-dependent topology (topology determined by the value of a variable representing time) of the pipeline network as a case study for the selected representative gas transmission network, the amount of additional power consumption in gas compressor stations due to uncertain cracking and the leaking rate was evaluated. Although the analysis of power consumption was performed for a hypothetical network, the estimates of the cracking rates, detection effectiveness, and leaking rates used were as close to the real cases as possible.

Comparative Life Cycle Evaluation of the Global Warming Potential (GWP) Impacts of Renewable Natural Gas Production Pathways

Renewable natural gas (RNG) sources are being considered in future energy strategy discussions as potential replacements for fossil natural gas (FNG). While today’s supply of RNG resources is insufficient to meet U.S. demands, there is significant interest in its viability to supplement and decarbonize the natural gas supply. However, the studies compare the life cycle global warming potential (GWP) of various RNG production pathways are lacking and focus mostly on a singular pathway. This effort is an attempt to close this gap and provide a comparison between the life cycle GWP of three major RNG pathways and the FNG pathway. The three RNG pathways evaluated are anaerobic digestion (AD), thermal gasification (TG), and power-to-gas (P2G) using various feedstocks. The functional unit is 1 MJ of compressed RNG ready for injection into the natural gas transmission network. The results show that RNG production is not always carbon neutral or negative. Depending on the pathway, the GWP impact of RNG production can range from −229 to 27 g CO2e/MJ compressed RNG, with AD of animal manure and AD of municipal solid waste being the least and the most impactful pathways, respectively, compared to the 10.1 g CO2e/MJ impact for compressed FNG.

Advancing in the decarbonized future of natural gas transmission networks through a CFD study

The injection of green hydrogen into the natural gas grid is a way to decarbonize the gas sector and build an economic transport route for the large-scale delivery of hydrogen. The suitability of the natural gas infrastructure for this purpose depends on the impact that hydrogen may have on the correct operation of its components and understanding the new flow conditions in the system is essential for this aim. Computational studies can anticipate the expected environment in the pipe system, assessing the readiness of the system. However, the experience on this topic is not extensive enough and deeper understanding is necessary. Here we show a CFD study to simulate the transport of H 2 /NG blends in a gas setup with the main characteristics of injection sites and gas pipelines representatives of the transmission gas network. This setup considers a blending station, the pumping and injection procedure, and different pipelines geometries to predict the behavior of various mixtures of H 2 /NG. It can be seen how (1) a good mixing is achieved in the blending station after a pipe length equivalent to 20–30 diameters is reached; (2) pumping gas by a piston type compressor shows pulsations in the flow regardless the composition of the blend that can be damped implementing mitigation measurements; and (3) asymmetries in the flow are found when the direction of the fluid changes after section reduction, but 20 diameters downstream of the reduction the flow is fully developed. • Modelling the injection of hydrogen in the natural gas transmission grid. • CFD studies to anticipate the behavior of the new fluid. • Mixing quality and possible segregation in blending stations considered. • Flow pattern when DN 80 pipes expands to a DN 150 or a DN 250 pipes. • Simulation of pumping of H 2 and CH 4 by a piston type compressor.

Operation Optimization of Multiroute Cyclic Natural Gas Transmission Network under Different Objectives

Natural gas transmission networks (NGTNs) are the main facility connecting upstream gas sources and downstream consumers. For a cyclic NGTN with multiple gas transmission routes, different gas transportation schemes will affect not only the energy consumption of the system but also the pipeline transportation costs paid by consumers. In this paper, three operation optimization models are established to determine the optimal operating state of a multiroute cyclic NGTN under different scenarios. The three mathematical models correspond to three different objective functions: minimize the cost of compressor energy consumption, minimize the expense of pipeline transportation, and minimize the sum of the two expenses. The decision variables of the models include the pipeline flow rate, the number of operating compressors, and the outlet pressure of the compressors. In addition, a series of linear and nonlinear constraints of nodes, pipelines, and compressors is also proposed to guarantee the feasibility of solutions. The operation optimization problem is solved by the General Algebraic Modeling System (GAMS), and the effectiveness of this method is tested on a small double-route cyclic NGTN and a large three-route cyclic NGTN. The results show that the developed optimization model is able to find optimal solutions under different models. In the cyclic network, the difference in the flow distribution of gas transmission routes is the key factor affecting the optimization result. In addition, compared with the compressor energy consumption cost minimization objective, the pipeline transportation expense minimization objective can create greater economic benefits for consumers. In the two network cases, consumers can save 14.51 and 59.18×104 RMB. Finally, optimizing the two objectives at the same time makes it possible to achieve an effective balance between them.

Flexible object-oriented modelling for the control of large gas networks

In this work we develop an innovative framework for the dynamic modelling of natural gas transmission networks. Thanks to its flexibility, this tool may be used to support operation of the network while also giving the possibility to explore and test new optimized scenarios, introduce new elements in the grid itself (ranging from new branches to new machines) and test the use of new gas mixtures. We use as benchmark the Italian high pressure gas transportation network, executing simulations of past daily operation scenarios. Results are compared to real measurements so to prove the validity of the adopted approach.

A unified benchmark for security and reliability assessment of the integrated chemical plant, natural gas and power transmission networks

This work presents a simulation framework to investigate the rigorous transient behavior of integrated systems comprising natural gas and power transmission networks, and a chemical plant whose feedstock is natural gas. This framework entails dynamic models for the gas transmission network and the SynGas plant, and a continuous-time AC-power flow formulation with dispatchable loads. It addresses the following key challenges: (i) analyzing energy and chemical system interdependencies, and their impacts on each other's supply reliability and security; (ii) providing an environment conducive to settling a critical question of how to prioritize the natural gas consumption as fuels of power plants or feedstocks of chemical plants based on sustainability and resiliency criteria. The framework provides an integrated benchmark enabling users to realistically study various planning, scheduling, and operation problems of these integrated systems such as process control, fault diagnosis, optimization, and environmental damage analyses. Effectively coordinating natural gas, power, and chemical industries, the benchmark outclasses conventional energy test problems in analyzing presented reliability and security scenarios since such traditional works solely focused on integrated gas and power systems. Results evidence the effects of nonlinear behavior of chemical plants on reliability and security of both natural gas and power transmission networks, in an integrated manner. Moreover, scenarios on power demand variations, compressor failure occurrences, and gas storage utilizations are enacted; according to the results, the unified benchmark lends insight into crucial information such as spatiotemporal characteristics of disturbances and their propagation throughout the integrated systems and the required period and strategy to damp such disturbances. Such information facilitates reliability and security analyses of the integrated systems and enables the coordination of chemical plants with traditional gas and power networks, particularly in multiple load shedding events which requires supply prioritization of natural gas to power and chemical plants.

Pressure-Based Energy Storage in Natural Gas Transmission Networks: Proof-of-Concept Analysis

Abstract This paper presents the possibility of energy storage in natural gas transmission networks using two strategies. Proof-of-concept calculations were performed under a steady-state assumption, and the more promising option was additionally modeled in a transient approach. The first strategy is based on a dedicated compressor–expander system installed at two ends of a pipeline. An electric-driven compressor increases the gas pressure in periods of peak electricity generation, while a gas expander allows energy recovery at a later stage. The compressor–expander distance determined by the inlet flow velocity of 5 m/s and a 4–5 h time shift ranges from approx. 75 to 120 km. The system provides a synergy effect, which allows to exceed 100% storage efficiency by reducing transmission losses. Storage efficiency obtained from the simplified model ranges from 70% to 128% for the performed case study. The second option uses existing compressors and pressure letdown stations expanding the gas to the distribution pressure. Here, gas pre-heating required prior to the expansion reduces the storage efficiency to about 30–40%. The dedicated machinery option was also evaluated using a transient model, which reports a lower efficiency if applied to the same assumptions. The system redesigned with the transient model is characterized by a longer storage duration (about 12 h) and a promising efficiency of 103.5%. Further research is needed to find the optimum design system parameters and to solve the detected problem of simultaneous compressor–expander operation which introduces idle work to the designed system.

Deep learning for spatio‐temporal supply and demand forecasting in natural gas transmission networks

AbstractGermany is the largest market for natural gas in the European Union, with an annual consumption of approx. 95 billion cubic meters. The German high‐pressure gas pipeline network's length is roughly 40 000 km, which enables highly fluctuating quantities of gas to be transported safely over long distances. Considering that similar amounts of gas are also transshipped through Germany to other EU states, it is clear that Germany's gas transport system is essential to the European energy supply. Since the average velocity of gas in a pipeline is only 25 km/h, an adequate high‐precision, high‐frequency forecasting of supply and demand is crucial for efficient control and operation of such a transmission network. We propose a deep learning model based on spatio‐temporal convolutional neural networks (DLST) to tackle the problem of gas flow forecasting in a complex high‐pressure transmission network. Experiments show that our model effectively captures comprehensive spatio‐temporal correlations through modeling gas networks and consistently outperforms state‐of‐the‐art benchmarks on real‐world data sets by at least 15%. The results demonstrate that the proposed model can deal with complex nonlinear gas network flow forecasting with high accuracy and effectiveness.

Environmental Effect on Temperature Measurement in Natural Gas Network Balance

Accurate temperature measurements are essential for accounting and balancing natural gas in transmission and distribution networks. In fact, in order to convert the gas volumes measured at operational conditions into standard reference ones, the accurate knowledge of both the thermodynamic conditions of the gas (i.e. temperature and pressure) and its chemical composition is necessary. In the case of large flow-meters, even small measurement errors (e.g. deriving from difference between the ambient temperature and the temperature of the fluid) can become relevant in terms of “unaccounted for gas”, especially when they do not find adequate compensation during the annual balancing of the network. To this aim it is necessary to carefully evaluate the systematic errors affecting temperature measurement which depend on instrumentation metrological characteristics as well as on thermo-fluid dynamic issues. In some cases, thermal insulation of the flow-meter and both upstream and downstream measuring stretches should be necessary. In this paper the authors present the results of an experimental study on the installation effects of temperature probes in closed conduits, performed at different operating conditions of natural gas transmission networks and aimed at estimating the typical random and systematic effects, and proposing optimal installation and operative solutions.

Impact of hydrogen injection on thermophysical properties and measurement reliability in natural gas networks

In the context of the European decarbonization strategy, hydrogen is a key energy carrier in the medium to long term. The main advantages deriving from a greater penetration of hydrogen into the energy mix consist in its intrinsic characteristics of flexibility and integrability with alternative technologies for the production and consumption of energy. In particular, hydrogen allows to: i) decarbonise end uses, since it is a zero-emission energy carrier and can be produced with processes characterized by the absence of greenhouse gases emissions (e.g. water electrolysis); ii) help to balancing electricity grid supporting the integration of non-programmable renewable energy sources; iii) exploit the natural gas transmission and distribution networks as storage systems in overproduction periods. However, the hydrogen injection into the natural gas infrastructures directly influences thermophysical properties of the gas mixture itself, such as density, calorific value, Wobbe index, speed of sound, etc [1]. The change of the thermophysical properties of gaseous mixture, in turn, directly affects the end use service in terms of efficiency and safety as well as the metrological performance and reliability of the volume and gas quality measurement systems. In this paper, the authors present the results of a study about the impact of hydrogen injection on the properties of the natural gas mixture. In detail, the changes of the thermodynamic properties of the gaseous mixtures with different hydrogen content have been analysed. Moreover, the theoretical effects of the aforementioned variations on the accuracy of the compressibility factor measurement have been also assessed.

Optimization of the Egyptian Natural Gas Transmission Networks

Optimization of the Egyptian Natural Gas Transmission Networks

Secure Operation of Integrated Natural Gas and Electricity Transmission Networks

The interaction between natural gas and electricity networks is becoming more significant due to the projected large penetration of renewables into the energy system to meet the emission targets. This is due to the role of gas-fired plants in providing backup to renewables as the linkage between these networks. Therefore, this paper proposes a deterministic coordinated model for the secure and optimal operation of integrated natural gas and electricity transmission networks by taking into account the N-1 contingency analysis on both networks. In order to reduce the computational burden and time, an iterative algorithm is proposed to select the critical cases and neglect other contingencies, which do not have a significant impact on the energy system. The proposed integrated mixed-integer nonlinear programming operational model is evaluated and compared to another enhanced separated model on the IEEE 24-bus and 15-node gas test systems. The results emphasize the importance and effectiveness of the proposed framework (up to 6.7% operational costs savings are achieved).