Study of the dynamic behaviour of an integrated energy storage system through numerical simulations in Aspen Plus Dynamics

The planned widespread installation of intermittent Renewable Energy Sources (RES) such as wind and solar will give rise to an increased need for large-scale electrical energy storage, in order to level the variable power production from these sources and stabilise the grid. While other large scale storage technologies, such as Pumped Hydro Storage (PHS), Compressed Air Energy Storage (CAES), and Flow Batteries (FBs), are limited by geographical constraints (PHS and CAES), require fossil fuel streams (CAES) or are characterised by a short life cycle (FBs), thermal energy storage systems, such as the Integrated Energy Storage System (I-ESS), do not suffer from such limitations. In the I-ESS, the electricity surplus from RES is converted into sensible heat by an electric heater and stored into a packed bed storage tank. When power is required, it can be released by using a Brayton-Joule cycle, in which the combustion chamber has been substituted by the tank. The I-ESS requires cheap materials for its packed bed thermal storage tank, uses air as a working fluid, which is free and readily available, and it can reutilise turbomachinery from decommissioned or underutilised conventional natural gas power plants, making this system a very promising possibility for future electrical energy storage plants. In this work, the dynamic behaviour of the I-ESS has been studied, exploiting the Aspen Plus environment. Firstly, a model in Aspen Custom Modeler has been developed to investigate the behaviour of the packed bed storage tank, starting from the models available in literature; then it has been integrated into Aspen Plus Dynamics to perform dynamic simulations of the whole system and its components. Both charging and discharging phases have been studied.