This paper compares the use of renewable energy sources (RESs) in the EU, focusing on their application in the transport, cooling and heating sectors and electricity production. It examines the current situation in the EU and assesses to what extent their laws and policies have contributed to the transition to renewable energy sources. This study focuses on several forms of renewable energy, including solar, wind, hydro energy, and biomass energy. The analysis is based on several variables, including production, consumption, and environmental impact. The findings of the analysis highlight the contrasts and similarities between the two nations and illuminate the best strategies for advancing sustainable energy development. This study also analyzes the main renewable energy strategies and policies to understand which factors support or hinder the transition to sustainable and clean energy. The analysis underscores the importance of optimizing energy efficiency and achieving long-term savings using RESs. Additionally, this study emphasises the role of RESs in enhancing energy security and promoting economic growth through technological innovation. This study also highlights the potential of RESs to reduce emissions in industry, transport, and agriculture, thereby contributing to environmental sustainability. The results show that the use of renewable energy sources (RESs) in the European Union has increased in the analyzed period. The results of this study can be useful to government agencies, businesses, academia, and the public interested in supporting the development of sustainable energy in the EU.

Operational research is a significant part of management, based on improving efficiency, operability, and machine quality. Those improvements influence the time of the repair process, workforce availability for the repair process, safety, and environment. The main goal of this article is to investigate the optimal – operating service life of the machine and the optimal – operating time interval for the renewal of the CNC metalworking machine. The research was implemented in a small enterprise in Slovakia that needed a CNC machine in the production process. The research hypothesis was determined H1: Using quantitative models of operational research can manage the machine’s life cycle. We used quantitative mathematical models of operational research. By calculation, we found that the optimal – operational lifetime of the CNC machine is 6 years. The renewal time of the machine is between the 5th and 6th year of use with a minimal level of the total costs for repairs and maintenance. This simulation is essential information for the financial plan for CNC machine renewal. The results of the research showed a confirmed hypothesis. The suggested proactive model is a viable instrument for the machine park in small enterprises with various orientations.