Energetic and Exergetic Performance of short term thermal storages in urban district heating networks

Meeting the heat demand of all customers attached, is the main objective for the operation of district heating (DH) systems combined with combined heat and power (CHP) plants. On the other hand, the economic ratification for the operation of CHP plants strongly depends on highly volatile electricity prices on the market. This trend will be reinforced in future, due to the additional integration and exploitation of renewable energies. Within this techno-economic field of most different operational objectives, DH systems and CHP plants must find a way for a cost-covering and efficient operation in future. Against this background, time shifts in producing and allocating heat supplied in parallel with electricity, are most attractive for DH system and CHP plant operators. Thus, margins on the electricity market could be maximized. On the other hand, heat amounts produced in parallel should be decoupled from the production of electricity as efficient as possible. Thus, thermal energy storages enter the limelight of interest for DH system operators. However, aspects concerning most different mechanisms for energetic and exergetic losses have to be considered for an optimized operation of these systems. Within this paper, the energetic and exergetic performance of sensible thermal storages will be examined. Underlying loss mechanisms of typical urban thermal storages are described qualitatively and quantified energetically and exergetically. For this purpose, existing models from literature are combined with practically relevant operational parameters for simulations.