A Thermoeconomic Approach for the Analysis of District Heating Systems

Abstract

District heating is a rational way to use fossil fuels for domestic heating (and cooling) in towns, especially if it is joined with a cogenerative production of electricity. As with every other process it must be economically convenient for its realization, so technical considerations must be integrated into the economic ones. Thermoeconomic theories take into account these two aspects, representing a good tool for an optimized design and correct management (Bejan et al. 1996).

The aim of this paper is to propose the use of thermoeconomic procedures for the analysis of district heating systems, in order to define criteria for the network design. The approach consists of the choice of significant design parameters, which can be varied in order to determine the optimized system.

An application to the Turin district heating system is presented here. The system is composed of a steam power plant and a gas turbine power plant, both cogenerative, and of the pipe network. The effects of the choices in the network project on the working conditions of the system and on the cost of its products are shown. The optimization problem has been solved by evaluating the decision variable under some particular conditions, obtained by solving fluid-dynamic, thermal and thermoeconomic problems for the whole system, corresponding to different values of the supply fluid temperature.

The application of the thermoeconomic theory to the network allows one to determine the effects of the parameters characterizing each user to the cost of the service provided. This information constitutes a tool for making management decisions, like the opportunity and modality for future expansions of the served area.

Keywords

• district heating, cogenerative systems, thermoeconomic analysis, system management