Strategic planning of electricity systems: Integrating renewable energie

The decision making process applied to the energy sector, particularly to the electricity sector, is complex and frequently requires the use of optimization models to deal with problems in the scope of electricity planning. The continuous growth of renewable energy sources (RES) to generate electricity became sustainable over the last years. This growth is justified by the increasing concerns related to the security of supply, the reduction of external energy dependency of most European countries, including Portugal, and the reduction of greenhouse gases emissions. Despite of the RES benefits, their integration is characterized by the difficulties on forecasting and variable electricity output. These difficulties bring considerable challenges to the electricity system management and to its planning. This work is focused on the assessment of the RES impacts on the electricity system and on its integration in the long and short-term electricity planning. The main goals of this work are to analyse in which way the growth of RES can affect the electricity system and its power plants, and also to propose new optimization models for the strategic planning of the electricity system, which are able to recognize and include RES impacts. This will provide the decision maker with tools that will support the design of long-term scenarios for the electricity sector. According to the outlined goals, four different optimization models were developed. All models were tested for a mixed hydro-thermal-wind power system, with characteristics close to the Portuguese one. The first one was proposed for the long-term strategic electricity power planning and a 10 years planning period was considered. Its usefulness was demonstrated by applying it for the analysis of the wind power integration in the electricity system. The second one, with a short-term horizon, aimed to solve the problem of the commissioning of power plants based on the available resources. The implementation of this model showed that modelling the electricity power systems requires a large set of constraints and a large number of data and information, resulting in significant computational effort to obtain a optimal solution. The development of a third model, a simplified approach of the short-term model, became therefore necessary. As previously, both short-term model and its simplified approach were used for the analysis of the impacts of wind power in the electricity system and in the operation of the different power plants. The last model resulted from the combination of the strategic electricity power planning model with the simplified model proposed for the commissioning of the power plants. The goal of this fourth model is to allow the inclusion of RES impacts in the design of scenarios for the electricity system, for a 10 years planning period. The models application demonstrated the need to acknowledge and include the impacts of RES integration, particularly wind power, on the strategic electricity expansion planning. Throughout the work, the complexity of models was evidenced along with the difficulties that non-experienced users may face when applying them. A user-friendly platform enabling researchers and stakeholders to deal with electricity planning problems in a simpler but reliable way was then proposed, resulting in an important contribution for the effective dissemination and usage of these models.