District heating system: Evaluation of environmental and economic aspects

Abstract

AbSTRACT With the need for limiting pollutant emissions, careful management of energy plants should be con-sidered to reduce the footprints that can be caused by these systems. Advantages of district heating (DH) systems have been linked to a decrease in local and global emissions, centralized heat production located outside urban centres, possible utilization of renewable heat sources. District heating, consisting of the distribution of hot water by means of underground networks for the buildings' heating and sanitary water, is an ever-expanding technology that allows the optimization of energy resources, with positive consequences in terms of both economic savings and environmental impacts. The aim of this work is to analyse the district heating system from an environmental point of view, in way to realize a general procedure of evaluation. To this end, the Italian city of Turin is taken as case study. Turin has long been subject to high concentration levels of pollutants, especially NO x and particulate. The environmental compatibility of extending the district heating network is evaluated. Two different tools are used: first, the environmental balance is defined to perform an evaluation of the flux modification at the emission sources; secondly, the atmospheric impacts of emissions are estimated using CALPUFF dispersion model. The results show a future reduction in overall NO x emission, as well as a reduction of ground level average NO x concentration ranging between 0.2 and 4 μg/m 3 . This study provides important information on the effects of a change of the energy configuration on air quality in an urban area. The proposed comprehensive methodology is applicable for other similar cases. 1 INTRODUCTION District heating (DH) is a technology used for supplying a town district or a complete town with the heat generated in large production plants. by concentrating and scaling up the heat production instead of using single house boilers, a lower specific heat production cost can be obtained as well as a higher conversion efficiency and the possibility to co-generate electric-ity. DH networks are commonly proposed in previous works as an environmentally friendly solution for providing heating services for the built environment due to their multiple ben-efits, such as centralized heat, production located outside urban centres, possible utilization or renewable heat sources and increased comfort for the consumers. The use of combined heat and power (CHP) systems in DH is an increasingly popular solution to meet the thermal energy needs in urban areas. Large DH networks are usually powered by large plants implementing a combined cycle. These systems are usually fuelled by natural gas. The environmental analysis of generation plants connected to DH networks is crucial, as these are usually located in heavily populated urban areas, characterized by the combined contributions of different emission sources, such as traffic, industrial and residential activi-ties. District heating networks are commonly proposed in previous works as an environmen-tally friendly solution for providing heating services for the built environment due to their multiple benefits, such as centralized heat, production located outside urban centres, possible utilization or renewable heat sources and increased comfort for the consumers.