Hydraulic modeling of large district energy systems for planning purposes

District Energy Systems (DES), e.g. District Cooling Systems (DCS) and District Heating Systems (DHS), have been widely applied in large institutions in the United States, such as universities, government facilities, commercial districts, airports etc. The hydraulic system of a large DES can be very complicated. They often stem from an original design that has had extensive additions and deletions over time. Expanding or retrofitting such a system involves large capital investment. Consideration of future expansion is often required. Therefore, a thorough study of the whole system at the planning phase is crucial. An effective hydraulic model for the existing DHS will become a powerful analysis tool for this purpose. Engineers can use the model to explore various alternatives of system configuration to find an optimal way of accommodating the DES hydraulic system to the planned future. A complete procedure has been developed to construct the hydraulic model for a large DES by using commercial simulation software for planning purposes. This paper will first introduce the overall modeling procedure. Then real hydraulic models for one DCS and one DHS, which are among the largest DES in the United States, will be introduced, as well as its successful applications in assisting decision makings.