8.4 Detailed Hourly Performance Modeling

The next step in the cogeneration developmental process is an hourly simulation of the site loads and system performance. This type of analysis directly addresses the issues of load coincidence and the relationship between the equipment hourly output, as adjusted for temperature, and other site conditions and the site hourly load.

The purpose of the case study is to illustrate how the more detailed analysis of loads and their variations can result in operating cost projections that vary from estimates developed using a simpler screening model. The case study is not intended as a tutorial on the use of any particular hour-by-hour model or as an endorsement of any model, and the hour-by-hour model is described in somewhat generic terms and only to the extent necessary to illustrate the case study. In addition, for illustrative purposes, some of the parameters used for the screening study (e.g., the project budget and turbine maintenance costs) were used directly in the hourly analysis, although it is recognized that more precise or accurate budget estimates are likely to be developed during the hourly analysis.

The hourly simulation was performed using a commercially available computer program. Many hourly simulation programs with differing capabilities are available. The choice of a program for a particular study should include consideration of factors such as user familiarity, cost, data availability and compatibility with program requirements, accuracy, and the program's suitability for the objectives of the analysis. It should be noted that many programs, including...