Biomass-fired CHP and heat storage system simulations in existing district heating systems

The installation of a biomass-fired Organic Rankine Cycle (ORC) unit coupled to a heat storage system (HSS) in an existing district heating (DH) system is proposed and analyzed from both energetic and economic point of view. A real DH system is considered as case study, and the optimal layout configuration is investigated varying the size of the components. The analysis is carried out tuning the heat demand dataset obtained from real data of a different existing DH system with a 6-min time step and ten years of operation. The heat demand is used to match the production from different generation units. The overall efficiency of the system, the primary energy savings related to CHP production, as well as the pay back time of the investment are evaluated. Calculations show that for the considered case study the maximum size of the HSS that gives noticeable advantages is 150 m3/MWth. The optimal configuration is different when considering energetic or economic criteria. Moreover, the current Italian incentive tariff on electricity production from renewable sources appears to promote the choice of low efficiency layouts for the case study under consideration.