Abstract:

Contrary to isolated systems, district networks allow better integration of all the resources and the reduction of the environmental impact. Nevertheless, this kind of system needs an important initial investment cost and an adapted management policy. Bearing this in mind, in this document we present the first part of a project which aims to develop a methodology for the optimal management of a cooling network, considering the dynamic interactions of the system components. A preliminary analysis for an academic case study is made. The system is composed of a distribution network, five distinct kinds of users and a return network. The problem includes constraints related to the structure of the network, the variation of users' load requirements and dynamic external conditions. Temperature dynamics in the pipelines is represented by a one-dimensional heat transfer equation. The resulting partial differential-algebraic equation (PDAE) system, which includes the mentioned differential equation and the network related equations, is transformed into a set of algebraic equations, using the method of orthogonal collocation on finite elements (OCFE). This methodology enables to solve dynamic optimization problems using a simultaneous (Oriented Equation) strategy. Thus, optimal temporal profiles for the operating parameters of the network, for an operational objective function that avoids the so-called “low ΔT syndrome” of the system were computed and analyzed. The problem was modeled in GAMS® (General Algebraic Modeling System) and solved using feasible path solver CONOPT. These results demonstrate the potential implementation of the proposed model and solution strategy for real study cases, due to its low computational times for solution.

Keywords: District cooling networks, Dynamic modelling, dynamic optimization, Orthogonal Collocation