PSI - Issue 77

Arian Semedo and João Garcia/ Structural Integrity Procedia 00 (2026) 000–000

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Arian Semedo et al. / Procedia Structural Integrity 77 (2026) 498–511

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1. Introduction The transition towards sustainable refrigeration systems has become increasingly critical due to growing socio-economic pressures and environmental challenges, particularly the need to reduce greenhouse gas emissions and improve energy efficiency. Among re frigeration technologies, CO₂ -based systems are recognized for their lower environmental impact compared to traditional refrigerants, yet their integration with renewable energy sources remains underexplored (Costa and Garcia, 2016; Costa and Garcia, 2015; Garcia and Rosa, 2019).The integration of renewable energy sources, such as solar, wind, and tidal power, into CO₂ refrigeration systems is essential to enhance sustainability and address both environmental and operational challenges. Utilizing locally available renewable resources not only reduces dependence on conventional energy but also mitigates CO₂ emissions and operational costs. Despite increasing interest, the feasibility, performance, and economic viability of such integrated solutions in specific contexts, particularly in coastal regions, require further investigation. This study aims to assess the feasibility and benefits of incorporating renewable technologies into CO₂ refrigeration systems, focusing on a refrigerated storage facility in Tarrafal, Santiago, Cape Verde. Four system solutions are evaluated through a comprehensive analysis considering technical, environmental, and financial criteria. The study seeks to identify the most effective solution for minimizing energy consumption and CO₂ e missions, while demonstrating how local renewable energy integration can advance sustainable refrigeration practices. By combining system optimization with renewable energy deployment, this work contributes to the development of environmentally sustainable refrigeration solutions and aligns global objectives for energy efficiency and emission reduction (Garcia and Semedo, 2024). 2. Principles of vapor compression refrigeration The vapor compression refrigeration system, which operates based on the reversed Rankine cycle, comprises four primary components: the compressor, condenser, expansion device, and evaporator. These components are interconnected to produce refrigeration by facilitating the thermodynamic processes of compression, condensation, expansion, and evaporation (Mahmood et al., 2021). The system functions by maintaining two distinct pressure levels, enabling the refrigerant to absorb or release heat as a result of the temperature difference between its gaseous and liquid states (Linhares et al., 2010). In this study, all analyzed refrigeration systems adhere to the vapor compression principle, utilizing the reversed Rankine cycle. Amid growing environmental concerns a nd international regulatory pressures, carbon dioxide (CO₂) has emerged as a sustainable and viable alternative to conventional refrigerants, such as R134a, within the examined case study (Maurois et al., 2020). Natural refrigerants like CO₂ offer long -term advantages due to their non-flammability and non-toxicity, making them highly suitable for vapor compression cycles. Furthermore, their widespread availability and negligible contribution to global warming establish them as environmentally responsible options (Sarabia et al., 2019). The transition toward such sustainable technologies highlights the refrigeration industry’s commitment to eco-friendly practices, in alignment with global initiatives promoting environmentally responsible solutions. 2.1. Evaluation of thermal loads Accurate determination of thermal loads for each refrigerated zone is essential to properly size the refrigeration system across the various configurations analyzed in this study. This ensures the maintenance of optimal temperature and storage conditions, thereby enhancing the system’s overall energy efficiency. Equations 1 through 4 provide a framework for selecting suitable refrigeration equipment by quantifying the thermal loads within each area. The assessment of thermal loads accounts for critical factors such as material thermal conductivity, wall thickness, and temperature differentials, allowing for a precise evaluation of cooling requirements. This analysis enables the design of refrigeration systems specifically tailored to the unique demands of each refrigerated space. In particular, conduction through walls is a major component of the thermal load, which can be calculated using the wall material’s thermal conductivity, thickness, and the temperature gradient across the surface. Equation (1) is employed to quantify the thermal load arising from conduction through the walls (Alaidross, 2023).