Low energy demand scenario for feasible deep decarbonisation: Whole energy systems modelling for Ireland

Typically, energy system decarbonisation scenarios neglect the mitigation opportunities from reducing and restructuring energy service demands (ESDs), focusing instead on technology and fuel substitutions. Models tend to be designed to factor technologies explicitly while ESDs are exogenous. However, existing literature suggests that the scale and speed of decarbonisation required to limit global warming to $1.5^{\circ }$ C by the end of the century requires a shift in energy demands to avoid the need for large-scale negative emission technologies. This can be brought about by major structural changes in drivers of demand such as transport modal shifting, substituting emission intensive materials like cement, and reducing building heat demand through behaviour change and efficiency. Ireland, the subject of this paper, has legislated one of the most ambitious decarbonisation targets in the world: the need to understand the role of demand shift is paramount. To fill this gap, the Irish Low Energy Demand (ILED) mitigation narrative is developed and applied to the TIMES-Ireland Model (TIM), an energy systems optimisation model. ILED represents a scenario where ESDs are decoupled from economic growth by shifting travel, increasing end-use efficiency, densifying urban settlement, focusing on low-energy intensive economic activities and changing social infrastructure. Compared to a scenario where ESDs follow ‘Business-as-usual’ growth, ILED enables the achievement of steep decarbonisation targets with a less rapid energy system transformation, lower capital and marginal abatement costs, and with lower reliance on the deployment of novel technologies.