Battery Energy Storage Systems are being projected as a key instrument for energy transition particularly within the context of the European Union's energy transition goals. The study focuses on Spain as a key market, exploring the integration of BESS with renewable sources such as solar and wind to enhance grid stability and optimize energy usage. Through market research, data exploration, and optimization modelling, the study examines the economic viability of BESS under various operational scenarios and project parameters. The findings indicate that co-located BESS can significantly improve the economic performance of renewable energy installations by enabling energy arbitrage, frequency regulation, and peak shaving, thereby enhancing revenue streams while reducing operational costs. The research highlights the technological synergies of BESS, such as shared infrastructure and reduced transmission losses, which contribute to overall grid stability and reliability. However, the study also identifies challenges, including high capital costs, evolving technology standards, and market sensitivity to electricity prices and regulatory changes. These factors necessitate careful planning and consideration in the deployment of BESS projects. The analysis suggests that, despite these challenges, the integration of BESS with renewable energy projects offers substantial opportunities for enhancing efficiency and profitability, particularly in markets with high electricity price volatility and robust ancillary service markets. The study also explores stand-alone use cases of BESS as a cost saving approach for data centres and any other large electrical load centres. The economic viability of BESS projects for these use cases was discussed and the results provide a framework for project developers to identify and develop BESS projects for their specific requirements.