Simulation of a district heating system with biomass-fired CHP and heat storage system

Renewable energy production from biomass can play an important role to achieve the objectives set out in the Climate and Energy package of the European Commission. District heating (DH) systems, micro-cogeneration plants and smart grids are key factors to allow an efficient use of bioenergy. Careful analysis should be performed in planning a DH system, in order to evaluate the performance of the whole system by means of different parameters and the primary energy savings calculated through the PES index. In this work the simulation of a DH system with a biomass-fired micro-cogeneration system and a heat storage was performed by means of a novel tool developed at the Energy Department of the Politecnico di Torino. This simulation tool is based on data collected from a real DH system (city of Turin) during 10 years with a time step of 6 minutes. The model has been used to evaluate the matching between heat demand and the contribution of each generation unit. The simulations were performed modeling the operation of combined cycles, biomass-fired micro-CHP (micro-Combined Heat and Power) unit and backup boilers and taking into account the presence of heat storage systems of different sizes and the effects they entail in the network thermal requirements and in the heat loads. The analysis performed show the variation of the system performance and the possibility to guarantee higher PES value due to a careful design and layout of the system. In particular, the role of heat storage has been shown to be essential to optimize the global DH system, with improvement in the efficiency, reduction of the peak of heat demand and increase of CHP production resulting in primary energy savings and environmental benefits.