This paper has experimentally investigated the performance of a dual-chamber oscillating water columns (OWC) imposed on Caspian Sea wave’s characteristics. Experimental runs were performed for three water draft depths of 10, 15, and 20 cm and eight wave frequencies ranging from 0.4 to 0.7 Hz. Also, if the converter consists of only one chamber, the power generated was 75W; however, by placing the second chamber serial behind the first chamber, the converter power increased to 116 watts (55% improvements). The results showed that if the frequency of the incident wave is not in the natural frequency range, the converter performs is better at the lowest water draft depth (10 cm). Whereas if the frequency of the incident wave is in the natural frequency range, the converter will have the best performance at the maximum water draft depth (20 cm). As the power generated at a water draft depth of 10 cm increased by 3.8% compared to a water draft depth of 20 cm. But within the natural frequency range and by resonance, the power produced at a depth of 20 cm is 27.3% more than the power generated at a depth of 10 cm.

Due to the necessity of utilizing renewable energies, the Archimedes screw turbine can be used as a power generation converter for the use of hydropower energy from river flows. A laboratory-scale model of this turbine with a scale of 1:6 has been designed and constructed. In the experimental tests, the performance characteristics of the turbine were investigated based on variations in the flow rate and electrical resistance. The optimal flow rate for the turbine was determined with the aim of achieving maximum efficiency. The performance characteistics of the turbine at this flow rate were evaluated using empirical equations derived from the experimental tests for various parameters. These equations indicated higher values for these parameters at this flow rate. Furthermore, for the scaling of the Archimedes screw turbine, dimensionless numbers such as Froude number and flow rates ratio were introduced. The experimental results were extrapolated to the prototype scale at the optimal flow rate of 2.6 (lit/s), where the maximum turbine efficiency occurs. The results showed that the use of Froude scaling led to approximately 25% higher values for the performance characteristics of the turbine compared to scaling based on flow rates ratio.

Using cogeneration systems is a great way to tackle fossil fuel consumption problems. This paper introduces a Combined Cooling Heating Power (CCHP) system to recover the waste heat of an RK215 heavy diesel engine as a prime mover. Therefore the CCHP system consists of Internal Combustion Engine (RK215), a heat storage tank, and an absorption chiller. Also, the system has been studied in four modes: CCHP, CHP, CCP, and single generation. The waste heat ratio has changed due to a y factor, and the effect of this different parameter, such as the start of fuel injection and exhaust gas heat, on the system's efficiency by considering first and second laws of thermodynamic in different operating modes has been investigated. The system's highest energy and exergy efficiency in CCHP mode is equal to 50.46 and 30.8%, respectively. According to the result, as the CCHPs cooling load to the absorption chiller increases, the performance also rises. Also, the system’s carbon dioxide emissions reduction has been studied. The results showed that using different modes for waste heat recovery can reduce carbon dioxide by up to 30% approximately for different modes. Also, the fuel energy saving ratio (FESR) has been investigated, and the results showed that systems in CCHP, CHP, and CCP modes could have FESR approximately equal to 21%.

In waste heat recovery from a heavy-duty diesel engine, with a focus on engine speed's impact, is explored. The critical problem of enhancing energy efficiency and reducing emissions through waste heat utilization is addressed. Waste heat in internal combustion engines, vital for sustainable energy use and environmental preservation, is investigated. Experimental analysis and thermodynamic modeling introduce Organic Rankine Cycle (ORC), Steam Rankine Cycle (SRC), and Combined Steam and Organic Rankine Cycle (CSO) for waste heat recovery. A non-linear relationship between engine speed and waste heat is identified. Waste heat increases up to 1600 rpm and decreases thereafter. The CSO cycle outperforms ORC and SRC cycles, achieving 43.4% higher efficiency. Fuel energy savings demonstrate CSO's superior economy, along with excellence in Annual Carbon Dioxide Emissions Reduction (ACO2ER). Waste heat recovery knowledge is advanced by introducing the efficient CSO cycle, contributing significantly to existing research.