Modelling the long-term evolution of the Italian energy system: The role of renewable resources and energy storage facilities

Climate change is a worldwide issue which is causing several difficulties and consequences both at human and environmental level. The energy sector is one of the main contributors to greenhouse gas (GHG) emissions and thus policy challenges are the main tool to contain this crisis. Indeed, a necessary path to intervene is the transition from traditional fossil fuels use toward the renewable sources, therefore leaving the carbon-based electricity generation in favour of an energy mix based on a higher renewable share and the residual part on gas. The aim of this thesis is to elaborate an energy model of the Italian energy system by performing long-term planning of energy evolution. In particular, it is investigated the key role of photovoltaic and onshore and offshore wind resources, by coupling them with power-to-power (P2P) systems based on hydrogen and batteries. The OSeMOSYS (Open-Source energy Modelling System) tool is used to develop those energy strategies at Italian national level. OSeMOSYS is a deterministic, linear optimization long-term modelling framework, based on the optimization of the net present cost of the energy system. An enhanced version is used, applying a specific approach for the time series representation, which is the clustering method. In this way, representative days (RDs) of the different years are defined considering specific attributes, such as the demand and the supply sides. A sensitivity analysis is performed to identify the optimal number of representative days as a compromise between the computational time and the solution accuracy, by means of a simplified base scenario. The starting point of the energy model is the potential assessment of both photovoltaic and wind onshore resources in order to determine their actual technical availability. It is used the Geographical Information Systems (GIS), which is a useful tool to manipulate and analyse spatial and geographical data. Subsequently, three main scenarios are elaborated aiming to determine the feasibility of renewable penetration in the electricity grid, by means of P2P systems. In particular, Li-ion batteries and hydrogen storage are the new energy storage technologies introduced in order to avoid an oversizing of renewable systems and allow a higher flexibility of the electricity system itself. Three main scenarios are elaborated varying the storage technology: only-battery (OB), only-hydrogen (OH) and a hybrid battery-hydrogen scenarios (BH). Results from the techno-economic optimization show that the BH scenario is preferrable: a cost-effective energy system is achieved combining the renewable energy systems with the storages facilities, leading to more than 60% of variable renewable energy sources (VRES) in the final energy mix production. Therefore, it is possible and feasible to achieve a high renewable share in the energy mix able to meet the future energy and climate challenges.