Operational Modelling of Regional Energy System with High Share of Wind Power, Photovoltaics and Large Heat Pumps: Case Study in the Baltic Countries Towards 2030

European energy systems are in a rapid transition driven by emission reduction targets and development in renewable energy and electrification technologies. Variable wind and solar generation, and electrification are expected to expand fast already within the next decade. Transition from dispatchable power and heat generation towards intermittent and unpredictable generation demands new solutions in flexibility and sector integration. Planning and operation of future energy systems require increasingly sophisticated computational modelling, able consider sufficient operational limitations, temporal resolution and sectoral co-operation. The Baltic countries — Estonia, Latvia and Lithuania — have ambitious targets in achieving emission reductions, increasing renewable generation and renewing their energy system already by 2030. This thesis studies the features of energy system modelling and research — especially in terms of wind and solar power and large heat pumps integration — and investigates the near-term future of the Baltic system using Backbone modelling software. First, an introduction to general trends in energy systems research as well as the operational characteristics of variable generation and heat pumps is given. Then, the special features of the Baltic system, as well as state-of-the-art solutions in computational modelling of energy systems are addressed. Finally, the case study models the hourly operation of the Baltic regional system in 2030 (including power, heat, transport and building sectors) based on realization of the national energy and climate plans. The operation and indicators of the scenario year 2030 are compared with a historical model year of 2017. Additionally, the sensitivity of the 2030 system operation towards different capacities of wind power, photovoltaics and large heat pumps is investigated in a comparative analysis. Results are analysed in terms of operational decisions as well as economic, environmental and energy security indicators. The case study modelling indicates a drastic transition in system operation, especially in Estonia, as oil shale based generation is substituted with renewables, and in Lithuania, ending up with a very ambitious share of variable generation. The modelled transition achieves substantial emission reductions, and increases renewable and domestic generation. The model maintains hourly system balance with active use of existing storages and interconnectors. However, possible energy security concerns are observed regarding Estonian balancing capacity, Latvian natural gas cogeneration plants and Lithuanian very high wind integration and simultaneous grid renovations. Additionally, the modelled power and heat system costs increase compared with 2017 in all three Baltic countries, and the model does not achieve targets in EU effort sharing sector emissions, due to increase in traffic demand and slow progress in end-use electrification. Deployment of wind power, especially onshore wind, seems to reduce emissions and increase domestic and renewable power generation shares in the Baltics inexpensively. The economic indicator results support the nationally planned wind power investment levels. Megawatt-scale photovoltaics competes with offshore installations in price, and can offer support for complementing wind variability, although full-load hours of solar generation in the Baltic region remain low. Large heat pumps show promise in feasibility in supplying district heat in Tallinn, Riga and Vilnius, especially when combined with large heat storages. In addition to improving energy efficiency and emission reductions, heat pumps can offer flexibility to complement variable generation, and support investments and domestic generation by increasing value of electricity