The objective of master thesis is to analyze the technical and economic potential of electrical battery energy storage systems to increase of renewable energy capacity in power system and their effect on costs of electricity generated. For this purpose an electricity system model shall be created for the analysis and evaluation of the impact of different shares of renewables scenarios on different types of power systems, identification of optimal portfolio of generation and battery systems and visualization of model results. The model shall be applicable to the simulation of energy systems at scales ranging from islands to small size national levels, that will be simulated, focusing on the use of battery storage to cost-effectively manage day-night and other short-term variations in supply. The master thesis encompasses the following activities: 1) literature review 2) theoretical work, including mathematical formulation of the problem 3) model implementation 4) case studies, evaluation and interpretation of results and 5) written presentation. Model complexity shall be as low as possible to reduce the solving computational speed. Simplified representations of generation system components shall be used. A copperplate (no restrictions on power flow) approach will be used to model transmission. Short-term period (one year) will be simulated, while using an appropriate temporal resolution for operational decisions such as unit generation commitment or battery storage state of energy. Trade-offs between timestep resolution, simulation times and accuracy could be investigated as part of the research work. The energy system optimization model shall be based on a deterministic optimisation of the system parameters (assuming perfect knowledge of renewable energy generation and demand) solved through Linear Program. The optimization criteria shall be to minimize discounted, levelized costs of electricity production across the study period (one year). The model shall simulate the system economic dispatch of all generation, battery storage and interconnection capacities, taking into account forecasted demand, generation plant characteristics and fuel prices as well as for the given set of constraints including ramp rates and minimum generation levels. The focus of the model is on the reliability of supply in terms of balancing electricity generation and consumption. Other criteria of security of supply like grid stability will not be investigated. The developed model shall be applied for the analysis of a specific case study. Scenarios without and with different renewables share and battery storage combinations (and optionally different demand scenarios) shall be analyzed. Optimal generation and battery storage capacities for the different scenarios, system dispatch and the resulting levelized cost of electricity generation shall be estimated. The model can be created by adjusting an existing model. As an example, the following energy modelling systems available under open source could be evaluated as basis for implementation: • SWITCH: http://switch-model.org/ • Calliope: http://www.callio.pe • Oemof: https://oemof.org