Proceedings of the 6th International Seminar on ORC Power Systems

Hybrid power plants comprising combined heat and power (CHP) integrated with a biomass-fired Organic Rankine Cycle (ORC) represent interesting opportunities for efficient district heating (DH) systems, increasing the level of renewable energy use and producing additional electric power at high efficiency. Nevertheless, in the case of biomass-fuelled plants, there is an increasing necessity for good alignment with the potential of the territory. In this paper, the mountain area of Susa Valley (North-West Italy) is investigated to find an optimal solution for the installation of a 1 MWe ORC unit, exploiting wood chips available in the area. The analysis concerns the simulation of three different thermal plants (two existing DH systems fuelled by natural gas and one at the design stage) characterized by different sizes of demand and percentages of user type (eg. residential, tertiary). The study first analysed real data available for the two existing DH systems (30 minute steps over 5 years), evaluating normalized thermal load. Then, based on climate data and the characteristics of the thermal user, a Matlab model was used to evaluate the new DH system at hourly intervals and to simulate both of the existing configuration plants in order to assess different plant designs. Finally, the Matlab model is used to identify the best solution, in terms of energy, environmental and economic aspects. For each case study, specific KPI (Key Performance Indicators) were evaluated, such as energy efficiency, primary energy consumption, carbon dioxide emissions and SPBT (Simple Payback Time). The study highlights the ORC’s role in the Emission Trading System (ETS) scheme in order to reduce total CO2 emissions of thermal plants and to obtain better economic return with respect to ever-increasing costs of environmental burdens linked to ETS. Due to the profit margin for heat and of electricity in the Italian context, the study found the optimal choice to be the DH system which is characterized by the highest heat sales and the lowest DH network temperatures.