As global energy demand continues to rise, integrating renewable energy sources (RES) into power systems has become increasingly important. However, the intermittent nature of RES, such as solar and wind, presents challenges for maintaining a stable energy supply. To address this issue, energy storage systems are essential. One promising technology is micro-compressed air energy storage (micro-CAES), which stores excess energy as compressed air and releases it when needed to balance supply and demand. This study investigates the integration of micro-CAES with RES in a 19-home microgrid in northern Portugal. The research aims to evaluate the effectiveness of a microgrid configuration that includes 100 kW of solar PV, 70 kW of wind power, and a 50 kWh micro-CAES system. Using real-world data on electricity consumption and local renewable potential, a simulation is conducted to assess the performance of this system. The findings reveal that this configuration can supply up to 68.8% of the annual energy demand, significantly reducing reliance on the external grid and enhancing the system’s resilience. These results highlight the potential of micro-CAES to improve the efficiency and sustainability of small-scale renewable energy systems, demonstrating its value as a key component in future energy solutions.

Pneumatic machines and systems are highly popular in the automation and mechanisation of production lines in many industry sectors, such as, e.g., food, automotive, production, and packaging. However, the energy efficiency of the pneumatic system is very low at about 10 to 20% The exhaust air from pneumatic machines has high energy, which is considered waste. This study introduces a novel energy recovery machine designed for integration into industrial compressed air systems. The authors describe the potential of the recovery machine within an industrial environment and present a developed exhaust air recovery system which collects exhaust air and converts it into electricity. Comprehensive industrial tests were conducted to evaluate its performance. The results, along with a detailed analysis, are presented, thereby showing there machine’s capabilities in recovering energy from compressed air processes. This research provides valuable insights into the practical implementation and benefits of deploying such energy recovery systems at an industrial scale. The findings demonstrate the machine’s potential to enhance energy efficiency and reduce operational costs in a wide array of industrial applications that are reliant on compressed air.

As the global demand for clean and efficient energy continues to grow, the development of advanced energy storage technologies is becoming increasingly important. This study explores the influence of the dead volume coefficient and pulse-width modulation (PWM) control strategy on the performance of a piston expander in a micro-compressed air energy storage system. Simulation results showed that low dead volume values, combined with short air supply durations with PWM values between 0.1 and 0.2, led to improved energy utilization. This was achieved through complete piston strokes and stable power output. In contrast, high dead volume values and high PWM settings, such as 0.9, resulted in incomplete air expansion, excessive air consumption, and a significant reduction in overall system efficiency, even though peak power output may increase. Sensitivity analysis confirmed that PWM had a major impact on efficiency, with the highest value of 0.76 achieved for a dead volume coefficient of 0.05 and a PWM value of 0.2. Under these operating conditions, the expander delivered a generated power output of 970 W. Additionally, PWM enabled flexible control of power output, without requiring modifications to the system’s physical design. The study highlights the importance of adjusting the air admission strategy to match the internal volume characteristics.

As renewable energy sources (RES), such as solar and wind, continue to grow in the energy mix, it becomes crucial to address their inflexibility and daily demand-production gap. Energy storage is vital, allowing storage during low demand and supplying power when needed. The authors investigated compressed air energy storage (CAES) as a mechanical solution, focusing on micro-CAES (μ-CAES) for smaller industries or housing estates. This research aimed at optimizing μ-CAES efficiency through modifications to the air expander's construction (piston parameters) and process parameters (air pressure, temperature). Initial results with a 3-cylinder expander showed an average power of 2.2 kW and 0.45 efficiency. Further enhancements, such as compressed air supply control and waste heat utilization during expansion expects to affect on increase of efficiency to 0.8.

This study presents the research and development possibilities of an expander for compressed air energy storage systems (CAES). The computer simulations made by the authors aim to find the optimal working parameters of the piston engine. The criteria for evaluating engine operation and the objects of analysis are the compressed air engine system’s efficiency and the electrical power output. Sensitivity analysis was performed on well-suited system parameters and geometrical sizes of the energy utilisation element. Appropriate selection achieves not only higher efficiency but also allows the system to be scaled to the end-user’s needs.