Modeling the Energy Freight- Transportation Network

Societies all over the world are entirely dependent on energy for achieving and sus­taining their development. Energy, in any form, plays a vital role in the industrial environment. Whenever sufficient energy is available, economic development occurs. A wide range of energy forms are being consumed, including natural gas (NG) for industrial uses and heating, electricity for light and to power electronic devices, petrochemicals to produce plastics, and petroleum derivatives such as gas­oline and diesel for transportation.

Because modern life is based on energy, individuals, corporations, and firms should have a reliable access to energy in all its forms. Problems involving the con­tinuous transportation and delivery of energy can lead to the disruption and break­down of economic, industrial, and social infrastructures. An energy resource cannot be reliable unless, first of all, it is delivered to right place at the right time, and sec­ondly, it must be available in the consumer desired quantity. Maintaining the effi­cient and reliable generation, transportation, and distribution of energy is the most important in a world which is so dependent on energy.

Different kinds of energy are used in today's industries and in people's lives. Some are fossil fuel resources such as oil and gas, but electricity, nuclear energy, solar energy resources, wind energy, and wave energy are also being used. All of these types should be delivered to consumers. The two most useful forms are fossil fuels and electricity. Electrical and gas systems are quite similar. Both are designed ^t0 carry energy from suppliers to consumers. The process of generating the energy and delivering it to the final consumer can be structured into:

Suppliers (electrical power plants or gas fields)

Transmission (high-voltage or high-pressure networks)

Distribution (medium-low voltage network or medium- or low-pressure network)

Customers (electricity customers or gas customers) [ 1 ].

^°8l*tics Operations and Management. DOI: 10.1016/B97K-0-12-.185202-1.00021 -9

²⁰¹1 Elsevier Inc. All rights reserved.

Nevertheless, there are differences between these two types of energy. NG j directly obtained from gas fields, whereas electrical energy is a secondary form of energy that is produced by the transformation of a primary form in a power plant Moreover, gas can be stored for future use in peak load periods, whereas electrical energy cannot be efficiently stored.

As societies develop, they inevitably need more and newer sources of energy Planning for power-generation expansion is necessary to meet the rising need for energy. Planning determines which types, where, and when new generation or transmission installations should be constructed [2|. Clearly, in any expansion plan there is an interaction between the energy supply and transport and power plants For example, gas is carried from gas Fields (suppliers) to consumers in liquefied natural gas (LNG) ships or flows through pipelines. Gas consumers can be classified as domestic or industrial customers [1]. Combined-cycle power plants are NG industrial customers that use gas to generate electricity. The expansions of pipeline networks, which are the part of the energy-transportation network, are complex and extensive. It is also possible to increase the capacity of the pipelines. However, the transmission capacity of a gas pipeline is not unbounded and depends on the pres­sure difference between the two ends of the pipeline. To increase the capacity of the network, compressors can be added at certain locations. Compressors enlarge the pressure difference between the two nodes of pipeline network. By expanding the network or increasing the capacity, the amount of gas that can be supplied to consumers is always limited.