Optimizing the temperature schedule of overground heat mains

Abstract

An approach to optimizing the operating mode of existing overground district heating networks by modifying the heat supply temperature schedule is considered. The majority of large consumers receive heat via the heat networks from local boiler houses or combined heat and power stations, which operate according to the temperature schedules defined in designing them. As time passes, the number of customers changes considerably, and so are their loads and the amount of heat transmitted via the heat network. New loads are covered by increasing the capacity of heat sources, whereas the heat networks remain unchanged. As a result, the fuel resources are utilized in a nonoptimal manner, and more energy is spent for transmission of heat. The rational organization of heat supply under the conditions of growing heat consumption will make it possible to reduce costs for transmission of heat. The aim is to reduce the financial or energy costs for transmission of heat via the heat mains. These costs include the cost of electricity for pumping the heat carrier, the costs due to loss of heat through the insulation of pipelines, and costs due to heat carrier leaks. The values of heat losses and the costs for pumping heat carrier are determined in accordance with applicable regulations. A relation for determining the optimum heat carrier temperature in the heat network's delivery pipeline is derived. Operating the overground heat mains at the optimal temperature determined from the proposed relation will make it possible to achieve the minimal financial or energy costs. The calculation was carried out using the parameters averaged over the heating period (the average heating season temperature, the average heat load, etc.). An example of calculating the optimal temperature schedule is given.