Energy storage in multi-energy carrier communities: Li-ion batteries and hydrogen multi-physical details for integration into the planning stage

The energy transition process, towards a carbon-neutral society, is undergoing, yet, still at a gradual pace. To facilitate it, the implementation of sector coupling measures is required. While the primary type of sector coupling measure, i.e. end-users' electrification, is a straightforward option, supported by the rapid growth of renewable electricity production, however, it fails to meet the overall energy needs. To overcome such limitations, the second type of sector coupling measure, i.e. cross-vector integration, for example, adopting hydrogen integration, which enables the coupling of two different energy vectors (thermal and electrical energy), can assume a decisive role. Furthermore, the energy end-users' role must be reconsidered in the energy paradigm. Indeed, while they played as passive actors previously, as they would consume energy based on habits without doubting the consequences, now they would be actively involved, by locally producing the energy, sharing it and even trading it for economic revenues. Such a concept is the foundation of the Local Energy Communities (LEC). By the European Commission's definition, LECs are legal entities that encompass the production, distribution, and utilisation of diverse energy carriers. They aim to maximise local energy benefits, which include community sharing, bolstering energy independence from the national grid, reducing the community's carbon footprint, and enhancing energy flexibility. Moreover, energy storage systems are central to the adoption of LECs. Enabling the decoupling of production and consumption and unlocking cross-vector potential by the use of hydrogen or thermal energy vectors. With the ever-growing interest in this, also scientific research is thriving, indeed energy systems modelling, which is the research topic to assess the impact of such measures, to provide key insights to policymakers, supporting them in making energy-related decisions, has been gaining progressively emphasis.Moreover, energy systems modelling has different sub-categories. Indeed, from a system-level perspective, where the focus is on the interconnection of different energy assets, each of them modelled as a single entity, through the optimisation of the planning and scheduling of LECs, i.e. management of the synergies among various energy vectors, delivering the requested energy demands, in the most efficient way. Commonly, for LEC energy planning, a bottom-up approach is adopted, meaning the energy asset's details are first investigated, to be then connected with proper connections and limitations, finalising the whole energy community of interest. The dominant mathematical formulation used is Mixed Integer Linear Programming, with time-dependent data at hourly resolution spanning a one-year planning horizon minimum. However, there is a lack of proper models, that are capable of accommodating dynamic variations in input parameters, such as energy costs, and investments. Additionally, correlations among different technology deployments, are not widely discussed. From the technological perspective of energy system modelling, the single energy asset is studied in detail, with all its subcomponents. Nevertheless, many cross-vector technologies, like hydrogen-related energy conversion technologies, have not received comprehensive coverage in the energy system modelling literature, due to their technology readiness level. Likewise, the Li-ion battery, despite being a mature energy storage solution, its technology degradation is not sufficiently explored, especially in stationary applications within the LEC context, which affects the system level planning, causing a mismatch of financial assessment due to its premature replacement. To address these limitations, from both system and technological perspectives, this thesis serves as a comprehensive exploration of energy storage integration within Local Energy Communities. Specifically addressing hydrogen and Li-ion battery technology. Moreover, this work has the aim to bridge both the technology and system perspectives of energy planning, indeed, single system details and limitations are first analysed, to be considered further at the system level. From the system perspective, this work addresses the necessity of having optimal alternatives during the energy planning stage. Indeed, the correlation between different technologies that is usually hindered, can be unveiled, thanks to these alternatives. Furthermore, the inclusion of dynamic variations of input parameters, along with different investment stages over the planning horizon, is explored. As a demonstration of proposed methodologies, this thesis presents two distinct case studies, that effectively take into account both levels of detail (technological and system). The first reported case study concerns the optimal design of a green hydrogen production plant, which consists of an offshore wind turbine, and an alkaline electrolyser system with all its auxiliary components. The second case study instead, has the the objective of analysing long-term storage solutions for a fully electrical energy-independent LEC, through the comparison of hydrogen and Li-ion battery solutions, taking into account the challenges posed by battery degradation.