**4. Conclusions**

The CHP model includes all the elements involved in the generation and distribution of energy to drive the process and supporting infrastructure. Optimizing such complex system requires a sophisticated model.

Within Saudi Aramco, the CHP model of each operating facility was found to be extremely useful in understanding the interactions between the various utilities' components. The interactions between these components could have been very complex without constructing a reasonably accurate mathematical model. Such tools are used during the design phase of capital projects to optimize cogeneration system sizes and configurations, explore alternatives, and conduct thermal efficiency synthesis to estimate what the final design would look like.

For operating facilities, the CHP model is used to evaluate potential efficiency enhancements, monitor the performance of existing equipment, identify energy saving opportunities, change operation and control based on optimum operational advice, and evaluate the impact of process variations on the CHP utilities system. The features of the model can be summarized in the following points:

