Produzione e distribuzione di elettricità e calore
District Heating Systems
Autors: Fabio Nardecchia, Fabio Bisegna, Fabio Zanghirella
Production and Distribution of Electricity and Heat
The basic idea of district heating (DH) is to use local fuel or heat resources (waste or renewable heat) to meet heating demand of local users, using a pipe distribution network to carry that heat. DH systems provide heat for space heating and hot water to households, commercial and service buildings and industrial users. In DH systems, heat generation is centralized or derived from an existing heat source, and distributed to consumers through pipelines, mainly in form of hot water. Heat sources for DH systems include: combined heat and power (CHP) plants producing both heat and electricity, different types of boilers, industrial systems producing waste heat, geothermal heat sources, solar heat, waste heat from incinerators and heat pumps. The current objective for district heating systems is to use a combination of two types of heat, e.g. industrial waste heat and renewable heat sources (solar, geothermal) to replace primary energy (particularly fossil fuels) and meet consumers heat demand, thus achieving emissions and the environmental impact. DH systems can also reduce the heating service cost, particularly if compared with fossil fuel–based heating systems. The DH additional cost for heat distribution is usually lower in urban areas with high population density, where demand is highly concentrated. DH systems has been developed in northern Europe, mainly in Scandinavian and Baltic countries, where they serve from 42% (Sweden) to 64% (Latvia) of the population. In Iceland, DH systems using the large local geothermal resources serve 99% of the resident population. Italy is one of the European countries where DH is less developed, serving only 4-5% of the population and meeting about 5% of heat demand. At the end of 2017, some 295 district heating networks were in operation. The municipal territories with at least one network are 238 distributed in 13 regions and autonomous provinces of central and northern Italy. Overall, the extension of district heating networks is just under 4600 km, about 30% of which is concentrated in 40 municipalities of the Lombardia region. About 85% of the current district heated volume is concentrated in three regions: Lombardia (45%), Piemonte (27%) and Emilia-Romagna (14%). In terms of heated volume (cubic meters, m3) per inhabitant the most heated regions are Piemonte (16.7 m3 per inhabitant) and Trentino-Alto Adige (16.5 m3 per inhabitant), followed by Lombardia and Valle d'Aosta (about 13 m3/inhabitant) and Emilia Romagna (about 9.5 m3/inhabitant).