scholarly journals Approximating Nonlinear Relationships for Optimal Operation of Natural Gas Transport Networks

Processes ◽  
2018 ◽  
Vol 6 (10) ◽  
pp. 198 ◽  
Author(s):  
Kody Kazda ◽  
Xiang Li
Keyword(s):  
Natural Gas ◽  
Piecewise Linear ◽  
Approximation Error ◽  
Compressibility Factor ◽  
Optimal Operation ◽  
Operating Conditions ◽  
Mixed Integer ◽  
Nonlinear Relationships ◽  
The Common

The compressor fuel cost minimization problem (FCMP) for natural gas pipelines is a relevant problem because of the substantial energy consumption of compressor stations transporting the large global demand for natural gas. The common method for modeling the FCMP is to assume key modeling parameters such as the friction factor, compressibility factor, isentropic exponent, and compressor efficiency to be constants, and their nonlinear relationships to the system operating conditions are ignored. Previous work has avoided the complexity associated with the nonlinear relationships inherent in the FCMP to avoid unreasonably long solution times for practical transportation systems. In this paper, a mixed-integer linear programming (MILP) based method is introduced to generate piecewise-linear functions that approximate the previously ignored nonlinear relationships. The MILP determines the optimal break-points and orientation of the linear segments so that approximation error is minimized. A novel FCMP model that includes the piecewise-linear approximations is applied in a case study on three simple gas networks. The case study shows that the novel FCMP model captures the nonlinear relationships with a high degree of accuracy and only marginally increases solution time compared to the common simplified FCMP model. The common simplified model is found to produce solutions with high error and infeasibility when applied on a rigorous simulation.

scholarly journals Integrated Process Re-Design with Operation in the Digital Era: Illustration through an Industrial Case Study

Processes ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 1203
Author(s):  
Maria Marcos ◽  
José Luis Pitarch ◽  
Cesar de Prada
Keyword(s):  
Cooling Water ◽  
Heat Pumps ◽  
Optimal Operation ◽  
Operating Conditions ◽  
Mixed Integer ◽  
Industrial Case Study ◽  
Non Linear Programming ◽  
Digital Era ◽  
Network Operation

This work discusses what should be the desirable path and correct tools for the optimal re-design and operation of processes in the Industry 4.0 framework, as illustrated in a challenging case study corresponding to a complex network of evaporation plants in a viscose-fiber factory. The goal is to integrate optimal design, to improve the existing cooling systems, together with the optimal operation of the whole network, balancing the initial investment with the potentially achievable savings. A rigorous mathematical model for such optimization purpose has been built. The model explicitly considers different structural alternatives as a superstructure for the incorporation of new equipment into the network. The uncertainty associated to future operating conditions is also considered by using a two-stage stochastic formulation. Furthermore, the model is also the base from which a deterministic real-time optimization (RTO) builds upon to support the daily management of the future network operation. The RTO tool suggests the allocation of different products to evaporation plants, the distribution of the cooling water and the suitable number of heat pumps to switch on for optimal economic operation. Design and operation problems are formulated and solved via mixed-integer non-linear programming and the results have been tested with historical plant data.

Calculation Method of Natural Gas Compressibility Factor and its Application in Pipeline Trade

2014 ◽  
Author(s):  
Xiaocui Tian ◽  
Xiaokai Xing ◽  
Rui Chen ◽  
Shubao Pang ◽  
Liu Yang
Keyword(s):  
Natural Gas ◽  
Compressibility Factor ◽  
Economic Benefits ◽  
Ideal Gas ◽  
Operating Conditions ◽  
Pipeline System ◽  
Natural Gas Pipeline ◽  
Gas Volume ◽  
Gas Compressibility ◽  
Simplified Formula

In the custody transfer metering of natural gas, it’s necessary to transform gas volume from metering state into standard state. Natural gas is non-ideal gas, and its compressibility factor varies with different components, temperature and pressure. So the accuracy of its calculation has direct impact on that of natural gas metering, and then affects the economic benefits of the enterprise [1]. According to related standard of China, in the custody transfer metering of natural gas, the formula stipulated by AGA NO.8 should be adopted to calculate compressibility factor. But the components of natural gas must be monitored at all times when this method is used, and the calculation process is complicated. In practical operation of natural gas trade, compressibility factor changes because of frequent adjustment of pipeline operating conditions. In order to simplify the calculation, simplified formula is applied to calculate compressibility factor generally, but it’s difficult to guarantee the accuracy at the same time. In this paper, the simplified formula, which is used for calculating natural gas compressibility factor of a joint-stock natural gas pipeline of CNPC, is modified with the standard formula stipulated by AGA NO.8. After the modification, an empirical formula of compressibility factor calculation applicable to this pipeline system is proposed, whereby the accuracy of compressibility factor calculation is improved. When the modified one is applied to natural gas trade, the accuracy of metering is improved likewise.

scholarly journals Optimal Operating Schedule for Energy Storage System: Focusing on Efficient Energy Management for Microgrid

Processes ◽  
2019 ◽  
Vol 7 (2) ◽  
pp. 80 ◽  
Author(s):  
Sooyoung Jung ◽  
Yong Tae Yoon
Keyword(s):  
Energy Storage ◽  
Energy Management ◽  
Power Grid ◽  
Optimal Operation ◽  
Operating Conditions ◽  
Mixed Integer ◽  
Small Scale ◽  
Basic Operation ◽  
Electricity Use ◽  
Operation Schedule

A microgrid is a group of many small-scale distributed energy resources, such as solar/wind energy sources, diesel generators, energy storage units, and electric loads. As a small-scale power grid, it can be operated independently or within an existing power grid(s). The microgrid energy management system is a system that controls these components to achieve optimized operation in terms of price by reducing costs and maximizing efficiency in energy consumption. A post-Industry-4.0 consumer requires an optimal design and control of energy storage based on a demand forecast, using big data to stably supply clean, new, and renewable energy when necessary while maintaining a consistent level of quality. Thus, this study focused on software technology through which an optimized operation schedule for energy storage in a microgrid is derived. This energy storage operation schedule minimizes the costs involved in electricity use. For this, an optimization technique is used that sets an objective function representing the information and costs pertaining to electricity use, while minimizing its value by using Mixed Integer Linear Programming or a Genetic Algorithm. The main feature of the software is that an optimal operation schedule derivation function has been implemented with MATLAB for the following circumstances: when the basic operation rules are applied, when operating with another grid, when the external operating conditions are applied, and when the internal operating conditions are applied.

Optimal Power Generation Unit Sizing for Combined Heating and Power Systems With Uncertain Loads and Fuel/Electricity Prices

2011 ◽  
Author(s):  
Aaron Smith ◽  
Kyungtae Yun ◽  
Robert Thomas ◽  
Rogelio Luck
Keyword(s):  
Power Systems ◽  
Optimal Solution ◽  
Optimal Operation ◽  
Computational Effort ◽  
Mixed Integer ◽  
Weather Data ◽  
Optimal Sizing ◽  
Electricity Cost ◽  
Analytical Scheme

An optimal sizing method is developed in this work based on an analytical scheme for determining optimal operation decisions. Using the analytic optimal operation scheme allows for a more thorough optimal sizing method because of the minimal computational effort required as compared to mixed integer programming approaches. For example, an optimal sizing method based on this approach can more feasibly consider several years of weather data and the range of likely fuel/electricity costs for the term of operation of the PGU. The optimal sizing method in this work takes advantage of this efficient optimal operation scheme and provides a robust optimal solution with respect to weather and fuel/electricity cost uncertainty. A case study of a medium sized office building is carried out by testing the algorithm for a range of 20 commercially available diesel engine PGUs.

The Effect of Compressibility Factor on Turbine Performance

2021 ◽  
Author(s):  
David Baumgärtner ◽  
John J. Otter ◽  
Andrew P. S. Wheeler
Keyword(s):  
Boundary Layer ◽  
Dynamic Behaviour ◽  
Compressibility Factor ◽  
Ideal Gas ◽  
Operating Conditions ◽  
Turbine Performance ◽  
Gas Dynamic ◽  
Dimensional Parameters ◽  
The Common ◽  
Common Perception

Abstract The compressibility factor Z is one of the most common properties that describes a fluid diversion from an ideal gas. Still, its effect on turbine performance is not well known. We determine a set of non-dimensional parameters that fix the gas dynamic behaviour, independent of Z, and thus isolate the effect that Z has on turbine performance. The results indicate that, contrary to the common perception, low values of Z and hence a strong diversion from an ideal gas lead to a reduction in loss for supersonic operating conditions, if all other non-dimensionals are accounted for. The aerodynamic mechanisms responsible are due to reductions in shock, boundary layer and trailing edge loss. The results from this paper are relevant for all future turbines operating with non-ideal working fluids.

Assessing Hydrate Formation in Natural Gas Pipelines Under Transient Operation / Ocena zjawiska tworzenia się hydratów w warunkach nieustalonego przepływu gazu w gazociągach

2013 ◽  
Vol 58 (1) ◽  
pp. 131-144
Author(s):  
Andrzej Osiadacz
Keyword(s):  
Natural Gas ◽  
Gas Flow ◽  
Hydrate Formation ◽  
Operating Conditions ◽  
Gas Pipelines ◽  
Natural Gas Pipelines ◽  
Hydrate Phase ◽  
Real Gas Effects ◽  
Classical Thermodynamics

This work presents a transient, non-isothermal compressible gas flow model that is combined with a hydrate phase equilibrium model. It enables, to determine whether hydrates could form under existing operating conditions in natural gas pipelines. In particular, to determine the time and location at which the natural gas enters the hydrate formation region. The gas flow is described by a set of partial differential equations resulting from the conservation of mass, momentum, and energy. Real gas effects are determined by the predictive Soave-Redlich-Kwong group contribution method. By means of statistical mechanics, the hydrate model is formulated combined with classical thermodynamics of phase equilibria for systems that contain water and both hydrate forming and non-hydrate forming gases as function of pressure, temperature, and gas composition. To demonstrate the applicability a case study is conducted.

Energy Usage in Natural Gas Pipeline Applications

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Augusto Garcia-Hernandez ◽  
Klaus Brun
Keyword(s):  
Natural Gas ◽  
Fuel Consumption ◽  
Transport System ◽  
Gas Pipeline ◽  
Operating Conditions ◽  
Pipeline System ◽  
Entire System ◽  
Energy Usage ◽  
Natural Gas Pipeline

Energy required to transport the fluid is an important parameter to be analyzed and minimized in pipeline applications. However, the pipeline system requirements and equipment could impose different constraints for operating pipelines in the best manner possible. One of the critical parameters that it is looked at closely, is the machines’ efficiency to avoid unfavorable operating conditions and to save energy costs. However, a compression-transport system includes more than one machine and more than one station working together at different conditions. Therefore, a detailed analysis of the entire compression system should be conducted to obtain a real power usage optimization. This paper presents a case study that is focused on analyzing natural gas transport system flow maximization while optimizing the usage of the available compression power. Various operating scenarios and machine spare philosophies are considered to identify the most suitable conditions for an optimum operation of the entire system. Modeling of pipeline networks has increased in the past decade due to the use of powerful computational tools that provide good quality representation of the real pipeline conditions. Therefore, a computational pipeline model was developed and used to simulate the gas transmission system. All the compressors’ performance maps and their driver data such as heat rate curves for the fuel consumption, site data, and running speed correction curves for the power were loaded in the model for each machine. The pipeline system covers 218 miles of hilly terrain with two looped pipelines of 38″ and 36″ in diameter. The entire system includes three compressor stations along its path with different configurations and equipment. For the optimization, various factors such as good efficiency over a wide range of operating conditions, maximum flexibility of configuration, fuel consumption and high power available were analyzed. The flow rate was maximized by using instantaneous maximum compression capacity at each station while maintaining fixed boundary conditions. This paper presents typical parameters that affect the energy usage in natural gas pipeline applications and discusses a case study that covers an entire pipeline. A modeling approach and basic considerations are presented as well as the results obtained for the optimization.

scholarly journals Optimal Operation of High-Speed Trains Using Hybrid Model Predictive Control

2018 ◽  
Vol 2018 ◽  
pp. 1-16 ◽  
Author(s):  
Yingze Yang ◽  
Zheng Xu ◽  
Weirong Liu ◽  
Heng Li ◽  
Rui Zhang ◽  
...  
Keyword(s):  
Linear System ◽  
Model Predictive Control ◽  
Hybrid Model ◽  
Predictive Control ◽  
High Speed ◽  
Piecewise Linear ◽  
Optimal Operation ◽  
Mixed Integer ◽  
Piecewise Linear System ◽  
Train Operation

The high-speed train operation process is highly nonlinear and has multiple constraints and objectives, which lead to a requirement for the automatic train operation (ATO) system. In this paper, a hybrid model predictive control (MPC) framework is proposed for the controller design of the ATO system. Firstly, a piecewise linear system with state and input constraints is constructed through piecewise linearization of the high-speed train’s nonlinear dynamics. Secondly, the piecewise linear system is transformed into a mixed logical dynamical (MLD) system by introducing the auxiliary binary variables. For the transformed MLD system, a hybrid MPC controller is designed to realize the precise control under hard constraints. To reduce the online computation complexity, the explicit control law is computed offline by employing the mixed-integer linear programming (MILP) technique. Simulation results validate the effectiveness of the proposed method.

Energy Usage in Natural Gas Pipeline Applications

2011 ◽  
Author(s):  
Augusto Garcia-Hernandez ◽  
Klaus Brun
Keyword(s):  
Natural Gas ◽  
Fuel Consumption ◽  
Transport System ◽  
Gas Pipeline ◽  
Operating Conditions ◽  
Pipeline System ◽  
Entire System ◽  
Energy Usage ◽  
Natural Gas Pipeline

Energy required to transport the fluid is an important parameter to be analyzed and minimized in pipeline applications. However, the pipeline system requirements and equipment could impose different constraints for operating pipelines in the best manner possible. One of the critical parameters that is looked at closely, is the machines’ efficiency to avoid unfavorable operating conditions and to save energy costs. However, a compression-transport system includes more than one machine and more than one station working together at different conditions. Therefore, a detailed analysis of the entire compression system should be conducted to obtain a real power usage optimization. This paper presents a case study that is focused on analyzing natural gas transport system flow maximization while optimizing the usage of the available compression power. Various operating scenarios and machine spare philosophies are considered to identify the most suitable conditions for an optimum operation of the entire system. Modeling of pipeline networks has increased in the past decade due to the use of powerful computational tools that provide good quality representation of the real pipeline conditions. Therefore, a computational pipeline model was developed and used to simulate the gas transmission system. All the compressors’ performance maps and their driver data such as heat rate curves for the fuel consumption, site data, and running speed correction curves for the power were loaded in the model for each machine. The pipeline system covers 218 miles of hilly terrain with two looped pipelines of 38″ and 36″ in diameter. The entire system includes three compressor stations along its path with different configurations and equipment. For the optimization, various factors such as good efficiency over a wide range of operating conditions, maximum flexibility of configuration, fuel consumption and high power available were analyzed. The flow rate was maximized by using instantaneous maximum compression capacity at each station while maintaining fixed boundary conditions. This paper presents typical parameters that affect the energy usage in natural gas pipeline applications and discusses a case study that covers an entire pipeline. A modeling approach and basic considerations are presented as well as the results obtained for the optimization.

scholarly journals Secure Operation of Integrated Natural Gas and Electricity Transmission Networks

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4954
Author(s):  
Ali Mohammad Rostami ◽  
Hossein Ameli ◽  
Mohammad Taghi Ameli ◽  
Goran Strbac
Keyword(s):  
Natural Gas ◽  
Energy System ◽  
Optimal Operation ◽  
Mixed Integer ◽  
Contingency Analysis ◽  
Transmission Networks ◽  
Operational Model ◽  
Electricity Transmission ◽  
Integer Nonlinear Programming

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).

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