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With the rapid surge of renewable energy integrations into the electrical grid, the main questions remain; how do we manage and operate optimally these surges of fluctuating resources? However, vast optimization approaches in renewable energy applications have been widely used hitherto to aid decision-makings in mitigating the limitations of computations. This paper comprehensively reviews the generic steps of stochastic optimizations in renewable energy applications, from the modelling of the uncertainties and sampling of relevant information, respectively. Furthermore, the benefits and drawbacks of the stochastic optimization methods are highlighted. Moreover, notable optimization methods pertaining to the steps of stochastic optimizations are highlighted. The aim of the paper is to introduce the recent advancements and notable stochastic methods and trending of the methods going into the future of renewable energy applications. Relevant future research areas are identified to support the transition of stochastic optimizations from the traditional deterministic approaches. We concluded based on the surveyed literatures that the stochastic optimization methods almost always outperform the deterministic optimization methods in terms of social, technical, and economic aspects of renewable energy systems. Thus, this review will catalyse the effort in advancing the research of stochastic optimization methods within the scopes of renewable energy applications. • Stochastic optimizations of uncertainty models in renewable energy applications. • Stochastic optimization approaches outperform deterministic approaches in the intermittent of RESs. • Trending of uncertainty models are converging towards data driven methods. • Power management in stochastic optimization approach is potential for the future research directions. • Hybridization of metaheuristic methods are preferred to solve the complex RE generations. [ABSTRACT FROM AUTHOR]

The implementation of renewable energy brings numerous advantages including reduction of power transmission cost and minimization of the global warming problems. The investigation of the influencing operational parameters as well as optimization of the solar energy system is the key factors to enhance the power conversion efficiency. The different optimization methods in solar energy applications have been utilized to improve performance efficiency. However, the development of optimal methods under the intermittent nature of solar energy resources remains key issues to be explored. Therefore, this paper presents a comprehensive review of the main generic objectives of optimization in renewable energy systems, such as solar energy systems. Moreover, this study introduces the most recent intelligent optimization methods used in solar energy systems with regard to its functions, constraints, research gaps and contributions. From this review, it can be concluded that the main objectives of optimizations methods are to reduce minimize investment, operation and maintenance costs and emissions to enhance the system reliability. This review also outlines a brief discussion of various challenges and issues of solar energy optimization. Finally, the review delivers some effective future directions toward the development of an efficient and stable solar PV system. • A comprehensive review on the optimization objectives in solar energy systems are explained. • Intelligent control strategies and optimization methods are utilized in solar energy systems. • Optimizations strategies reduce emissions and costs of system into maximizing reliability. • Solar energy systems enhance the output power and minimize the interruptions in the connected load. • This review highlights the challenges on optimization to increase efficient and stable PV system. [ABSTRACT FROM AUTHOR]

• The coupling of CCPP power generation units to an inlet air cooling system has been presented. • Classifications and performance of the inlet air cooling systems have been reviewed. • Technical characteristics of various inlet air cooling techniques on the CCPP have been compared. • The thermal performance of the inlet air cooling technique and its effect on the CCPP performance augmentation has been reviewed. This work aims to provide a state-of-the-art review of the performance of combined cycle power plant (CCPP) based on several proposed inlet air cooling systems. Investigators strive to meet the significant need to promote and develop inlet air cooling technologies to recover heat from the wasted energy in the exhaust gasses of the CCPP and diminish the environmental impacts. Various types of cooling systems mainly offer a boost for electric power generation during the peak load hours. The output power of the CCPP directly depends on the mass flow rate of air that flows through the air compressor. Therefore, during extremely hot weather conditions, subsequently, the air density drops, and this leads to a drastic decrease in the power output. This paper reviews available studies investigated the impacts of inlet air cooling systems on the performance of the CCPP. The fogging cooling system contributed by up to 17% in improving the total performance of the CCPP; however, with the use of the evaporative cooling, the performance was enhanced by only 4%. The energy consumption of mechanical chiller compared to that of evaporative cooling is high due to the effectiveness of the evaporative cooler which depends on the humidity of inlet airflow. Further, the mechanical cooling system can provide the CCPP with a cooling effect for around 7-hour on-peak periods. This method increases the gain of the CCPP performance by 13.6%. Ultimately, the CCPP equipped with an absorption chiller demonstrates the best solution to increase the performance by up to 23%. [ABSTRACT FROM AUTHOR]

• Novel hybrid rainfall hydropower with solar photovoltaic-battery is introduced. • Photovoltaic-battery and photovoltaic-battery-hydro system are analysed and compared. • Robust energy management is carried out to utilize the excess power for water pumping. • Photovoltaic-battery-hydro and robust energy management reduces levelized cost of energy. • The hybrid photovoltaic-battery-hydro is suiting standalone rural electrification. This paper presents analysis and optimization of standalone hybrid renewable energy system for powering a 3.032 kWh/day housing unit. The hybrid system is strategized to utilize harvesting rainfall and integrating a pumped-hydro storage with a solar photovoltaic-battery system. The optimization, using particle swarm optimization technique, is conceived for minimizing the over sizing of components and secure reliable power supply management with objective function to minimize the levelized cost of energy for loss of power supply probability of 0.0. Four different cases have been optimized, analyzed and compared. Case 1 is a conventional photovoltaic-battery system, Case 2 is photovoltaic-battery integrated with hydro system utilizing only the direct rainfall, Case 3 is photovoltaic-battery integrated with pumped-hydro storage system with the battery bank as the primary power backup, and Case 4 is the photovoltaic-battery integrated with pumped-hydro storage system with hydro system as the primary power backup. Results are revealing that integration of rainfall-based hydropower system of only 100 W with effective water storage of 6.5 m3 at 7.0 m of net water head has resulted in reduction of the installed photovoltaic capacity by about 13.0% compared to power system without rainfall-based hydropower system. The highest hydropower share of 5.0% is observed in Case 4. Case 4 has also resulted in least levelized cost of energy of 0.443 $/kWh. It has been demonstrated that it is possible to achieve environmental appropriateness, reliable and low-cost power generation by integration of harvesting rainfall with photovoltaic-battery system. The suggested system has less dependency on the battery storage as the batteries are the most expensive part with short life span in the proposed integrated renewable systems. [ABSTRACT FROM AUTHOR]