Experiences in mid-term planning of district heating systems

District heating systems often consist of two types of units: those that only produce heat, and those that produce both heat and power, called combined heat and power units. In order to improve the operation of such systems, detailed and reliable optimization models and methods must be available. The present paper considers mid-term planning, i.e. planning of the production of heat and power for periods of up to one month. Problem features and the questions relevant on the mid-term horizon are discussed. These include the operation of fuel storage and the influence of the national tax system. A mixed integer programming model of a set of district heating systems in Sweden is developed. The major goal is to minimize the operation cost, subject to the condition of fulfilling heat demands. The main output results are the power produced and consumed each day of the planning horizon. This is important information for the hedging activities performed in the financial power market. The model has been used regularly to support an energy company with production plans. Computational results are presented. (C) 2003 Elsevier Ltd. All rights reserved.