1 Abstract

Pipeline simulation is currently usually perceived merely as an engineering tool for solving technical tasks. The new idea presented in this paper is to extend the scope of pipeline simulation to include commercial applications. The paper reports on how this new application is used at VNG - Verbundnetz Gas Aktiengesellschaft, a gas importer and pipeline operator. The pipeline simulator computes calorific values as input data for thermal billing. The application has received statutory approval for billing purposes, and has been routinely used since fall of the year 2000.

2 Background

VNG is a major natural gas importer and pipeline operator in Germany, with a market share of 16 %. VNG wholesales natural gas of different composition, mainly from the North Sea and from Russia. In 2000, deliveries totaled 520 trillion BTU (152.2 billion kWh). To conduct this business, VNG owns and operates a high-pressure transmission system spanning 4,500 miles throughout the eastern part of Germany. For comparison, VNG's supply area matches New York state, both in size and population. For seasonal load management and for ensuring reliable gas deliveries to customers, VNG also operates underground storage facilities with a total capacity of 15 % of annual deliveries. page -2- Figure 1: The VNG high-pressure pipeline grid with the locations of the four main inlet stations and the underground storage facilities. Since the composition of natural gas varies and since there are frequent changes in the composition of the gas purchased, VNG needed to implement a thermal gas billing procedure. However, the necessary metering infrastructure was not available at the time VNG began to operate following unification of the two German states. This situation sparked the innovative idea of using pipeline simulation to compute gas composition for customer billing, in order to cut investment and operating costs in gas analysis metering equipment that would be otherwise have been inevitable. VNG opted for the SIMONE pipeline simulator sold by LIWACOM. The solution has been in use since fall 2000. It has received statutory approval for use in customer billing from the Bureau of Weights and Measures. This approval was mandatory, as consumer protection interests are affected. The simulation-based thermal billing approach has not only reduced costs for VNG, but has also resulted in excellent transparency of business processes. This has improved customer retention, and provides a good basis for optimizing VNG's commercial and technical operations. page -3-

3 Thermal Billing

In the past, gas deliveries were often simply billed on the basis of the volume delivered. More accurate billing taking into account the thermal energy of the gas delivered is acquiring greater importance for many reasons. As gas pipeline systems become increasingly interconnected, variations in the composition of the gas they carry tend to be more frequent and intense. In addition, gas consumers wish to have freedom of choice regarding natural gases of different compositions offered by various vendors, and rising gas prices require more accurate billing.

This content is only available via PDF.
You can access this article if you purchase or spend a download.