Public defence in Engineering Physics, M.Sc. Justinas Jasiunas

Public defence from the Aalto University School of Science, Department of Applied Physics
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Title of the thesis: Energy system resilience to extreme disruptions: reexamining impacts and their assessment

Doctoral student: Justinas Jasiunas
Opponent: Assistant Professor Mathaios Panteli, University of Cyprus, Cyprus
Custos: Professor Peter Lund, Aalto University School of Science, Department of Applied Physics

Nowadays, much attention is justifiably given to energy systems' cost and environmental impacts. However, major disruptions remind modern societies of the primacy of interrupted energy supply. One major disruption can disrupt as much as all moderate disruptions in years. Moreover, the week-long loss of heating and water supply impacts more than seven days-long loss of leisure. Therefore, the unprecedented severity disruptions can cause extreme impacts that were not considered possible and thus not prepared for, as illustrated by the COVID pandemic and the Russo-Ukrainian war.

This work presents the development of modeling methods and their use to assess the spatiotemporal lost load (i.e., unsupplied electricity demand) profile from a historically unprecedented but meteorologically plausible windstorm. The windstorms were chosen as Finland's largest cause of supply interruptions after mapping a broad landscape of threats and analyzing Finnish grid vulnerabilities. The lost load assessment required a reexamination of relevant impact factors and suitable methods, as most existing impact models focus on historical severity level disruptions. The spatiotemporal field of unprecedented wind gusts was generated by scaling up the field of the historic windstorm with a statistical method that goes beyond existing methods only for spatial extremes. The impacts of this windstorm were assessed by modeling a synthetic (i.e., real-like) electricity grid with its component fragilities (i.e., fault probabilities) and disruption-severity-dependent repair times. The synthetic electricity grid has a previously unseen detail of medium voltage powerlines (most vulnerable to wind-induced tree fall) at national scale (this work focuses on strategic questions like regulation and standards). The synthetic grid is generated with the new methodology by mapping data of many small distribution grid operators in Finland to work around the absence of real grid data.

The impact model recreates lost load profiles for Finland's three most impactful and recent windstorms with errors of around 20%. The unprecedented windstorm's 24% higher wind gusts produce a ten times larger lost load than the most impactful historic windstorm. Expected uses of the produced lost load profile include the assessment of cost-benefit of security measures, the identification of major cost factors, and a realistic scenario for emergency preparedness exercises.

Keywords: resilience, energy system, windstorm, synthetic system, faults and repairs

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