Emerging hybrid technologies have better potential than conventional technology for diversifying the desalination industry, which is presently being dominated by thermal and membrane-based desalination. Notwithstanding the technological maturity of the desalination processes, they remain highly energy-intensive processes and have certain disadvantages. Therefore, the hybridization of thermal and membrane desalination processes holds great attention to mitigate limitations of individual processes in terms of energy consumption, quality and quantity of potable water, overall efficiency and productivity. This paper provides an oversight of conventional and developing desalination technologies, emphasizing their existing state and subsequent potential to reduce water scarcity. Conventional hybrid desalination systems (NF-RO-MSF, MED-AD, FO-MED, MSF-MED, RO-MED, RO-MSF and RO-MD) are briefly discussed. This study reveals that the integration of solar thermal energy with desalination has a great potential to substantially reduce greenhouse emissions besides providing the quality and/or quantity of potable water in cost-effective ways. Due to its abundant availability with minimal/no carbon footprint and the ability to generate both thermal and electrical energy, solar energy is considered better than other renewable energy technologies. The findings further suggest that hybrid desalination systems are technically sound and environmentally suitable; however, a significant study of the research process and development is still required to make this technology efficient and economically viable.

Cavitation is undesirable phenomenon and it becomes more severe under off-design conditions and lower tail race level. Transient simulations has been performed using Shear Stress Transport (SST) turbulence model in CFX solver.The Rayleigh Plesset mass transfer model is applied for the numerical predictions of cavitating flow through Francis turbine.An attempt has been carried out to analysis of cavitating flow at low head Francis turbine under different operating conditions having varyingsuction heads. Summarizing, it has been found that the performance loss and cavitation rate are found maximum under over load conditions. A high amplitude of pressure at low frequency has been found at part load operating conditions of the turbine which may cause fatigue damage to the turbine over time. Cavitation intensity, performance loss and instability increase with increase of suction head.

A high velocity is rarely accessible in water streams such as rivers, canals, and outlets of sewage and common effluent treatment plants. However, an average velocity of 0.5 - 1.0 m/s is reported to be available in many water streams most of the time. Hydrokinetic (HK) turbines can extract power from the flowing water in these streams. Considering the small quantum of power generated, the economic factor is more significant than efficiency. A Savonius-type HK turbine can generate energy from low-velocity magnitudes of around 0.5 m/s, although it remains a low-speed and low-efficiency turbine. In this study, an attempt has been made to computationally investigate the performance of the Savonius turbine in a water stream channel. It is observed that the performance of the Savonius turbine is not significant, and the generated power cannot be utilized constructively for different applications. Therefore, it is necessary to develop and investigate variant constructive systems to enhance turbine performance. This manuscript focuses on exploring these variant systems and understanding their performance characteristics. Four variant systems have been selected: (i) System-1: Solely Savonius turbine, (ii) System-2: Savonius turbine with a flume, (iii) System-3: Deflector section used before the flume, and (iv) System-4: Deflector section used before the turbine. The investigation was carried out for these four variant systems using the Fluent commercial code. The results indicate that the Coefficient of performance (Cp) is low for System-1, solely Savonius turbine, with a value of 0.052. For the other variants, Cp values were found to be 0.357, 1.385, and 0.579 for the turbine with a flume, deflector before the flume, and deflector before the turbine respectively at the Tip Speed Ratio (TSR) is 1. Moreover, the study also extends to optimizing Cp under different TSR for the different variant systems. The intention is to use this study to install an HK turbine with an optimum constructive structure for maximizing and stabilizing the power that can be used for an isolated application.

1. The primary drivers behind the hunt for innovative, sustainable ways to produce clean energy are the depletion of fossil fuel supplies brought on by excessive consumption and its detrimental eff...