Top-level analysis of site utility systems

This paper presents a practical approach to the analysis of industrial utility systems to determine the true value of steam savings and to identify improvements to the utility system. The analysis is carried out for existing utility systems in cases when potential energy saving projects to site processes are identified and evaluated. The potential benefits identified can be used to determine the economics of retrofitting the processes on a site to decrease their energy consumption. The approach builds on a robust optimization framework for industrial utility systems. A stepwise optimization procedure is applied to determine the true marginal price of steam at the different pressure levels and the constraints on steam savings imposed by the utility system. This allows the analysis of complex utility systems with automated tools for utility system optimization. Steam at a given level can have different values depending on how much is saved. This contradicts the common practice of attributing a single price to steam at a given level. The resulting top-level analysis provides a strategy for steam saving on total sites and modifications to the utility system.