Calendar Ageing Optimised Operation of Battery Storage

Abstract

The battery energy storage systems used to buffer the energy required for Overhead Line Island Systems in a rail network that utilises battery-electrified multiple units needs optimised operational strategies. Existing optimisation models often neglect internal battery temperature variable in ageing, leading to suboptimal operational strategies and inaccurate lifetime predictions. The study aims to implement a linearised non-linear calendar ageing model dependant on temperature for optimised battery storage operation within a linear energy system optimisation framework (oemof.solph). The thermal model of the storage system which was not implemented in oemof.solph earlier, was derived and integrated using a single-state ordinary differential equation. The model accounts for heat generation and heat loss functions with estimated thermal parameters of the cell under test. A non-linear temperature-dependent degradation relation was developed from the literature based calendar ageing model, for temperatures from (0°C - 60°C). The non-linear relation was integrated to linear optimisation domain using convex hull. Single and multi-day optimisation was conducted to compare the operational results of the model with the case that omits temperature based ageing. Results indicated that incorporating the degradation cost during energy system optimisation, reduced the overall battery ageing after 4 years by nearly 8.5%, without an increase in grid consumption. The model proved to be practical for air-cooled battery energy storage systems (BESS), where significant temperature variations occur during operation. In contrast, a liquid-cooled system benefits less, due to its strict thermal management.