Optimal Extension of District Heating Systems Through Thermoeconomics

Network extension is an issue in planning district heating systems, specially in a large town; the optimal network does not necessarily connect all the buildings, because of technical and economical reasons. The selection of areas to be connected should be made during the design process, since further variations in the topology are usually difficult and conduct to a non-optimal configuration. This paper deals with the optimal extension of the district heating network using economic criteria. The algorithm here proposed is based on the application of thermoeconomics, together with some concepts derived from the optimization technique called simulated annealing. The algorithm reduces significantly the time required for solving the problem with respect to other optimization techniques such as genetic algorithms. An initial superstructure connecting all the possible users is built. Then the structure is progressively simplified, until the optimal configuration is found. The procedure is applied first to the actual district heating network operating in Turin. The application to a small portion of the central urban area of Turin, at the moment not connected with the DH network. is also proposed. Some general considerations about the optimal network configuration are then obtained by varying the climatic data, the volume of the buildings in the considered area and the distribution of users throughout this area.