Cities have a critical role to play in securing a net-zero future. Despite accounting for less than 2% of the Earth’s surface, they consume 78% of the world’s energy and produce more than 60% of greenhouse gas emissions. With projections indicating that the world’s urban population will rise to 68% by 2050 (a 13% increase from 2018), cities must urgently seek out innovative solutions to balance the needs of growing citizen populations, in a manner which is sustainable and consistent with a zero-carbon trajectory.

This presentation will explore how digital twin technology has been leveraged to pursue Limerick’s net-zero vision; their ultimate aim being to go beyond this to become Ireland’s first “Positive Energy City” (i.e. one which generates more primary energy annually than it consumes) by 2050.

Through close collaboration with institutions within the city, a detailed decarbonisation roadmap of the entire city centre was outlined taking into account both transport and built environment-related carbon emissions. The city-level digital twin was used to understand what level of emissions reductions the city would be able to achieve if following the decarbonisation guidance set out at a national level. In doing so, it was identified that Limerick would fall short of its 2050 target by a significant margin (approx. 33%) if following the government guidance alone. The study therefore highlights the need for rigorous testing of decarbonisation policies/guidance, and science-based analysis using appropriate digital tools to ensure that any proposed actions will in fact get cities (or indeed any other group of buildings) where they need to be by 2050.


Susan graduated with a Master’s degree in Energy Systems Engineering from University College Dublin, having completed a Bachelor’s degree in Mechanical Engineering. During her time in university, she carried out research into the decarbonisation of communities, focusing on the integration of energy modelling and stakeholder engagement. Following her studies, she continued working with the university to develop their first Energy Master Plan, which aimed to identify feasible steps that could be taken towards the decarbonisation of the campus. While working in the UCD Energy Institute she gained experience in building energy modelling and retrofit analysis.

Since joining IES in 2020, Susan has worked on a range of research projects, aiming to utilize the digital twin technology to improve the sustainability of the built environment and encourage the uptake of low-carbon technologies. In particular, her work has focused on the development of community- and city-scale digital twins, creating baseline energy models for a number of European cities. Most recently, she has been working on utilising the digital twin of Limerick City to create a tailored decarbonisation roadmap out to 2050, analyzing the impact of national plans and targets on the carbon emissions of the city.