Assessing the feasibility of cogeneration retrofit and district heating/cooling networks in small Italian islands

Sustainability of energy supply in small islands has been emerging as a severe issue, due to the large margins for improvement of the most frequently adopted solutions. In many European islands large amounts of heat are wasted by the operation of engines-based power plants; conversely, heat is produced by boilers or by electric equipment for different uses, like domestic hot water or space heating. In this paper a techno-economic analysis is proposed to assess the feasibility of CHP-retrofit of existing power plants and the possible utilization of the recovered heat to supply, via a district heating and/or cooling network, the energy requests of civil users in the tertiary and residential sectors. The analysis is performed for six islands in Italy characterized by different demographic and climatic conditions, so as to get a comprehensive understanding of the factors that favour/obstruct the viability of the examined technical solution. As expected, due to the low “linear heat density” observed in small islands, the investments resulted “far from being attractive”; only in the case where public support mechanisms are adopted, the integration of the existing power plants with heat recovery devices and a district heating network resulted moderately attractive, especially in the largest islands.