Flow Of Saline Water Research Articles

Multi-criteria decision-making and artificial bee colony algorithm for optimization of process parameters in pyramid solar still

This study focuses on optimizing process parameters for pyramid solar still using Multi-Criteria Decision-Making Grey Relational Analysis (MCDM-GRA) and bio-inspired metaheuristic Artificial Bee Colony (ABC) algorithm. The objective is to enhance the performance of the pyramid solar still (PSS) performance integrated with a peripheral solar water heater under different operational parameters, including saline water flow rate, temperature, and solar intensity. Experiments are designed using Taguchi's L9 (33) orthogonal array (OA), and the outputs are optimized with MCDM-GRA. The optimum conditions for maximized productivity and system efficiency are a solar intensity of 1000 W/m2, a saline water mass of 3 kg, and a saline water temperature of 40 °C. With these settings, the system achieves an efficiency of 65.33 % and produces 1.96 kg of potable water. The ABC Algorithm, on the other hand, suggests that the optimal conditions for achieving maximum productivity and system efficiency involve a solar intensity of 1000 W/m2, a mass of 3 kg for the saline water, and a water inlet temperature of 30 °C. In this scenario, the system produced 1.92 kg of potable water with an efficiency rate of 64 %. Analysis of variance (ANOVA) shows that solar intensity contributes significantly towards productivity by 81.72 % with an error of 3.82 % and regression coefficient of 96.18 %. Regression models are developed from the results obtained and fed to ABC for further optimization, yielding results similar to MCDM-GRA.

The impact of a balanced humidification-dehumidification desalination system driven by a vapor-compression heat-pump system

This study adopts a numerical thermo-economic investigation of a novel desalination system. In this system, a vapor compression (VC) heat pump is used to drive a balanced humidification-dehumidification (HDH) desalination unit with multiple extractions. The mathematical model of the proposed VC-HDH system is validated experimentally. The system is examined for water production under a condenser temperature of 45 °C, evaporator temperature of −5°C, feed saline water temperature of 30 °C, feed saline water flow rate of 1 kg/s, and an energy effectiveness value of 0.85 for the HDH unit’s components. The results show that without air extraction, the system can produce 6.62 kg/h of desalinated water for 0.011 $/l with a gained-output-ratio (GOR) value of 9.1. On the other hand, when a single air extraction is applied, about 20 kg/h of desalination water is produced by the system for 0.0042 $/l and 29 GOR. Increasing the number of air extractions to two yields a freshwater production rate of approximately 40 kg/h for 0.0026 $/l and a GOR value of 57. A considerable positive effect of the HDH unit’s performance is found on the system’s performance on both thermodynamic and economic scales. For better desalination performance, it is found that the feed water temperature should be maintained between 25 °C and 30 °C. Finally, the theoretical ceiling of the proposed system’s GOR is estimated.

Integration of desalination and energy conversion in a thermo-osmotic system using low-grade heat: Performance analysis and techno-economic evaluation

Freshwater and electricity cogeneration systems, using renewable energy sources, can play a crucial role at the water-energy nexus. By placing a hydrophobic, porous membrane between a hot saline water flow and a pressurized cold freshwater flow, thermal-osmotic energy conversion and thermal-osmotic desalination can be implemented simultaneously. A novel open-loop freshwater and electricity cogeneration system is proposed and evaluated, which consists of a hydrophobic membrane module, a seawater pump, two heat exchangers, and a hydraulic turbine. In the base case designed for a daily freshwater production of 3.9 × 104 m3/day, the net power output is estimated to be 2.15 MWe and the energy efficiency of power generation is 0.24%. Considering the economic benefits brought by the electricity production, the water production cost is 0.36 $/m3 with a global average industrial electricity price of 0.11 $/kWh. Compared with the commercial reverse osmosis desalination technology, the desalination cost of the hybrid system is reduced by over 28%. The parameter analysis is carried out and reveals that optimizing membrane properties and operating conditions can greatly improve the energy efficiency and reduce the water production cost. Improving the liquid entry pressure and permeability coefficient and reducing the thermal conductivity of the membrane are the key to improving the application prospect of the system.

Performance analysis of step type solar still and comparison of the performance with evacuated tube collector coupled with single slope step type solar still

This research project aims to address the growing need for freshwater in regions affected by water scarcity, particularly in coastal and desert areas. The focus is on evaluating the effectiveness of a solar-powered desalination system, which utilizes a single slope step type solar still and an Evacuated Tube Collector (ETC) to produce fresh drinkable water. Additionally, Computational Fluid Dynamics (CFD) analysis is conducted to gain insights into the natural convection of heat transfer within a glass tube, which creates a buoyant flow of saline water. The design consists of a solar evacuated tube, which heats up due to the exposure to sun rays and this heat is transferred to the impure/saline water (effluent). The water is then discharged to a single slope step type solar still which absorbs energy from sunlight and increases the evaporation rate in the solar still. Thus, the water evaporates and is then condensed by the inner surface of the glass roof hence purified water is collected. The CFD flow analysis of incompressible fluid under the effect of gravity in the transient condition is carried out for ETC in the ANSYS workbench. Also, fluid flow analysis of single slope step type solar still consisting of ten steps with a water depth of 3 cm in multiphase conditions using the VOF model is carried out to obtain the amount of distillate output per day in fair weather conditions in the location 13.2848⁰ N, 74.7486⁰ E in Katapady, Udupi. The amount of distillate collected as a result of CFD analysis was found to be 5.195 kg/day. The contours obtained from the steady state analysis for solar still showed the distribution of temperature, solar heat flux, and mass flow rate. The transient analysis of the ETC assisted well in obtaining the temperature in the ETC collector tank and the variation in solar radiation throughout the day. The contours of ETC showed the buoyant flow of water under natural convection, velocity distribution, density distribution and solar irradiation distribution on glass walls.

Spatio-Temporal Patterns of Saltwater Intrusion in A Narrow Meandering Channel

Saltwater intrusion has become a crucial issue for water resources management across the globe. Consequently, this issue leads to problems such as encroachment on water intake zone, loss of freshwater vegetation and also disturbance to aquatic life habitat. Undeniably climate change increases the saline water flow into the river system. The meandering rivers are common, and the hydraulics is more complex than straight rivers. An experimental hydraulic investigation was carried out in the Universiti Teknologi Malaysia to elucidate the hydrodynamic interactions between saline water and freshwater in a narrow meandering channel. The spatio-temporal salinity profiles along the river are discussed in this paper. The findings prevailed a typical characteristic of a salt-wedge estuary and indicated the processes of estuarine mixing. As the saltwater flows upstream, the salinity level drops due to the dilution process. Salinity levels and densimetric Froude number were mainly driven by freshwater discharge in the channel. A variation of dilution rate in a narrow meandering channel were up to 78.9% due to strong velocity forces produced by a high freshwater discharge. Furthermore, the flow resistance induced by the channel boundaries and meander planform itself influenced the salinity intrusion profiles along the channel.

Influence of PV/T waste heat on water productivity and electricity generation of solar stills using heat pipes and thermoelectric generator: An experimental study and environmental analysis

In recent years, numerous studies have been performed to improve the evaporation rate of solar stills and the electrical power of the photovoltaic module. In this paper, an experimental study of modified single slope solar still integrated with a photovoltaic panel, heat pipes and thermoelectric generator to enhance the performance of solar still is presented and compared with conventional solar stills. Five heat pipes were proposed and installed below a photovoltaic module to transfer the generated waste heat to the saline water of a solar still. Two thermoelectric generators were installed between the photovoltaic panel (hot sides) and the cooling water block (cold sides) to use the generated waste heat. The saline water flows to the cooling water block and then to the evaporation zones of the heat pipes to increase the water temperature and enhance the electrical power of the photovoltaic panel and thermoelectric generator. Results showed that the highest hourly power generation of the solar panel of conventional solar still (CSS), solar still by water cooling and thermoelectric generators (SS-WT), solar still by heat pipes (SS-HP) and solar still by heat pipes, water cooling and thermoelectric generators (SS-HP-WT) was about 68 W, 69 W, 73 W and 75 W, respectively. Also, the daily water productivity of CSS, SS-WT, SS-HP and SS-HP-WT was about 748 ml/m2, 832 ml/m2, 1058 ml/m2 and 1162 ml/m2, respectively. Moreover, CPL of CSS, SS-WT, SS-HP and SS-HP-WT were about 0.042 $/L, 0.098 $/L, 0.077 $/L, 0.084 $/L, respectively. In addition, cost per power production of conventional photovoltaic, SS-WT, SS-HP and SS-HP-WT were about 0.061 $/kWh, 0.141 $/kWh, 0.128 $/kWh and 0.147$/kWh, respectively.

Fault mapping and characterization of a coastal aquifer related to a mangrove ecosystem, using electrical resistivity tomography (ERT), ground penetrating radar (GPR) and hydrochemical data: The case of the Mangue de Pedra Aquifer, Armação dos Búzios, Brazil

The Mangue de Pedra is a rare and fragile ecosystem. It stands above a sandstone-conglomerate substratum of the Neogene Barreiras Formation, which also hosts the local coastal aquifer, known as the Mangue de Pedra Aquifer. The Pai Vitório Fault, a regional structure, which represents the south border of the São João da Barra Graben, separates the Paleoproterozoic crystalline basement from these sediments and limits the occurrence of both the mangrove and aquifer. Aside from hydrochemical data, geophysical surveys, including electrical resistivity tomography (ERT) and ground penetrating radar (GPR), allowed to investigate the local substrate and the role of fault structures affecting the aquifer-mangrove ecosystem, as well as to provide a better understanding on groundwater circulation and effects of seawater interface dynamics. The hydrochemical data for 11 water samples were used for interpolation to generate pH, Eh and electrical conductivity (EC) maps, and the results revealed a zone of less saline water flow and a discharge zone at the cliff's base. The survey of five ERT lines, using the dipole-dipole configuration, provided a picture of the saturated zone of the aquifer. The interpreted sedimentary units have been divided in three different layers, based on water content and variation of the water quality: 1) unsaturated zone; 2) good/intermediate-quality freshwater (34.4–137 Ω-m); 3) brackish/poor-quality freshwater (4.46–34.4 Ω-m). This method indicated the presence of at least five normal faults, including major and shallow structures along the mangrove, and the basement 5 m below sea level. The radargrams also confirmed the presence of most of these faults, recognized as complex fault zones at shallow levels. The interpretation on orientation of these structures was then enhanced by geoprocessing techniques, indicating a major NE-SW trend. This set of faults provides some of the requirements for the mangrove existence, including: a) the shape and materials of the beach and surrounding landscape, composed by chalcedony breccias blocks which are resistant to erosion, protecting the local environment from impact of sea waves; b) pathways for groundwater flow; and c) traps or barriers within the aquifer, which channel less saline waters to that specific site. This set of factors creates a unique ecosystem, which normally does not occur in beaches from open sea shorelines.

Review on 2D MXene and graphene electrodes in capacitive deionization

The development of the electrochemical desalination technique for saline water by the capacitive deionization (CDI) process is progressing with ever-increasing interest. In the CDI technology, the saline water flows through the spacer sandwiched between the pair of electrodes, and the ions are captured and stored within electric double layers (EDLs) when a voltage between 0.5–2.0 V is applied. When the voltage is reversed or removed, adsorbed ions are released, and electrodes are regenerated. Carbon materials-based electrodes show effective, but limited electrosorption capacity as the ions are removed based on the EDL mechanism only. There is a demand for new advanced materials that can enhance the electrosorption performance of the CDI. The improvement can be achieved by involving other electrosorption mechanisms such as redox pseudocapacitance and intercalation pseudocapacitance mechanisms. Graphene is a 2D nanosheet material, it has a laminar structure and can be stacked up to form slip shape pores in the electrode and allow easy ion motions than other random porous materials. Graphene can also be prepared into a 3D graphene sponge as an interconnected framework. MXene is a new group of materials made of 2D transition metal nitrides, carbides, and carbonitrides. It has exhibited a significant pseudocapacitance behavior, outpacing the energy storage capacity of many other capacitive materials, particularly when normalizing to the electrode’s volume. This review discusses (1) the recent advances in graphene materials and their limitation for enhanced desalination performance and (2) the state-of-the-art art developments of MXene as an emerging material for CDI. • The recent advances and limitations of graphene and MXene as CDI electrodes. • Redox and ion intercalation pseudocapacitance mechanisms are employed in CDI. • Graphene nanosheets and 3D sponges have a laminar structure allowing easy ion motion. • MXene has exhibited an outstanding pseudocapacitance behaviour behavior as electrodes. • The state-of-the-art developments of MXene as an emerging CDI electrode materials.

Experimental investigation on a cooling cum desalination system using a modified mechanical heat pump

An experimental study on a mechanical heat pump unit incorporated with a humidification-dehumidification system for desalination and cooling is presented. The experimental prototype is developed by modifying the condenser of a mechanical heat pump unit into an evaporative condenser. The evaporative condenser is used as a humidifier, and the evaporator as a dehumidifier, of the humidification-dehumidification desalination system. The proposed unit is evaluated with combinations of air and saline water flow rates, and also evaluated by means of total desalination output, cooling output, gained output ratio and energy utilization factor. At fixed air flow rate, increasing saline water flow rate decreases the desalination output, and increases the cooling output, gained output ratio and energy utilization factor, respectively. The highest fresh water yield and gained output ratio are 2.94 LPH and 1.30 respectively. The highest cooling output and energy utilization factor are 4.39 kWth and 4.12, respectively. The total urban heat island mitigation at the operating condition of 200 m3.h−1 and 380 LPH is 5.25 kWth. Compared with similar vapor compression refrigeration operated humidification dehumidification desalination units, the present study produces more fresh water yield and cooling output with fewer energy consuming devices and heat exchangers.

Performance assessment of a novel solar distiller with a double slope basin covered by coated wick with lanthanum cobalt oxide nanoparticles

Solar distillers are simple desalination systems used to produce freshwater from saline water by utilizing solar energy. The low water yield is the key drawback of solar distillers. In this work, a novel double slope wick type solar distiller (DSWSD) coated with lanthanum cobalt oxide (LaCoO 3 ) nanoparticles doped in black paint is experimentally investigated. The nano LaCoO 3 /black paint is uniformly speared on the jute wick surface to boost the absorption improvement of solar irradiance for effective desalination. The influence of water flow rate (namely; 0.050, 0.10, and 0.20 kg/min) on the internal mass and heat transfer of the proposed DSWSD is analyzed. The mass and heat transfer coefficients (HTCs) are computed using the experimental results and compared with those computed according to Dunkle’s correlations. Experiments have been conducted on the established DSWSD under climatic conditions of Vijayawada, Andhra Pradesh (16.4419° N, 80.6226° E), India. It is observed that there is an increase in the internal HTCs as well as distilled yield at low flow rates of saline water for the DSWSD. The daily productivity of the proposed DSWSD coated with and without 20 wt % LaCoO 3 /black paint is 5.40 and 3.85 kg/m 2 . day, respectively, at saline water flow rate of 0.05 kg/min. Moreover, the average values of evaporative and convective HTCs as well as energy efficiency are found higher by 11.20%, 17.54%, and 24.86%, respectively, than that of the solar distiller without LaCoO 3 /black paint.

Experimental evaluation of salinity geosynthetics capillary barriers

This paper explores the transient upward flow of saline water in one-dimensional soil and soil–geosynthetics columns to evaluate preventive measures to mitigate salinity rise. Unsaturated soil concepts are utilised to elucidate the salinity movement through geotextile and geocomposite drain interfaces. The presence of a geotextile layer slowed down the capillary rise of the saline water. However, it did not prevent the breakthrough of the saline water due to the hydrophilicity of the geotextile and the suction at the geotextile base being close to the geotextile's water entry suction value. In contrast, using a geocomposite drain mitigated the upward saline wetting front. It acted as a salinity capillary barrier due to the initial hydrophobicity of its geotextile component and the air gap present in the geonet core.

Freshwater Transport in the Scotian Shelf and Its Impacts on the Gulf of Maine Salinity

AbstractA 3D unstructured‐grid ocean circulation model covering the continental shelf and coastal seas around New England is used to investigate freshwater transport (FWT) on the Scotian Shelf (SS) and its impact on the salinity in the Gulf of Maine (GoME). The model was first validated using observed elevation, velocity, temperature, and salinity at multiple locations, demonstrating generally high model skills. Intraseasonal variabilities of freshwater fluxes in 2017 and 2018 were then analyzed across different transects around SS and Browns Bank (BB). These indicated that the flow pattern in SS during 2017 was consistent with previous understanding: low salinity water flows southwestward along the shelf and turns into the GoME around BB. However, in 2018, most of the low salinity water did not enter the GoME, but was transported to the open ocean. The most striking difference occurred early in the year when the FWT, normally at its maximum, was practically stopped by an anticyclonic eddy impinging upon the shelf break near the western end of SS. Then in March, in contrast to the prevailing eastward wind, two southwestward wind events occurred that induced an excessive amount of FWT in SS. We further showed that when anticyclonic eddies impinge on the shelf break, the typical geostrophic balance associated with southwestward flow is interrupted, and a new geostrophic balance is established with the directions of pressure gradient force and flow reversed. The influence from anticyclonic eddies explains the abnormally low FWT in SS and higher GoME salinity in 2018.

Optimal design of a hybrid thermal- and membrane-based desalination unit based on renewable geothermal energy

• A renewable-based hybrid desalination system consisting of HDH and RO is evaluated. • Two different operating modes of the introduced system are investigated. • Exergoeconomics is used to identify the optimal working condition of the system. • Maximum exergy efficiency of the plant is 28.86% for the second operating mode. • The first operating mode can provide freshwater at a maximum rate of 22070 m 3 /day. In this article, exergoeconomic analysis of a hybrid desalination system driven by renewable geothermal energy source is investigated. Freshwater and electrical power are the products of this system. Humidification – dehumidification (HDH) unit works in parallel with reverse osmosis (RO) unit to produce freshwater and Kalina cycle is the power generator unit. Thermoelectric generator (TEG) is responsible for providing the energy required by RO unit. As both HDH and TEG can operate with low-grade energy, two different modes are suggested for the proposed system. In the first mode, the geothermal low grade energy stream is passed to TEG unit, while in the second, it goes through the HDH unit. The effect of different parameters on four main objective functions is examined in parametric study. Moreover, with the aid of selection maps, the objectives of modes can be compared in different operating conditions. The maximum attainable exergy efficiency is calculated to be 28.86% for mode 2. Single objective optimization studies revealed that the first mode produces the largest amount of freshwater at a rate of 22,072 (m 3 /day), while the minimum achievable freshwater cost and total product cost rate can be obtained in the second mode, which is calculated to be 21.94 (¢/m3) and 37.19 ($/GJ). Besides, Sankey diagrams for exergy flow and mass flow of saline water are presented to unravel the impact of each sub-system on exergy and salinity.

Investigation of the transport properties for saline water in porous materials - Modeling of the permeability coefficient for saline water-

Salt weathering is a major concern for cultural heritages such as ruins and tombs, and desalination by poulticing is an interesting potential method to efficiently remove contaminating salt. Predicting the degree of achievable desalination is very important. However, many existing models used to consider saline water transport in porous materials have been developed based on the theory of pure water. To understand saline water flow in porous materials, we determined the saline water permeability of a tuff stone by the falling-head method. We found that the permeability of the tuff stone was affected by factors other than the density and dynamic viscosity of the saline water.

Experimental investigation of lab scale solar powered Electrodialysis system with corrugated membrane configuration

An experimental laboratory-scale setup of a solar-powered electrodialysis (ED) water desalination system is investigated in this study. The introduced ED system maintains a coupled configuration of corrugated membranes for the first time. The corrugated membrane configuration allows for increasing saline water's flow velocity fluctuations, especially near the membrane surfaces. As a result, the flow turbulence and mixing at the membrane surfaces are promoted, and therefore, higher rates of ion exchange can be attained. The acquired concentration of dilute water was measured at the steady-state operation over a diversity of system parameters: input voltage (4–12) volts, flow rates (5–22 mL/s), and feed concentrations (15–35 g/L). The optimal current efficiency (CE) value was obtained at 70% with a flow rate of around 15mL/s and feed concentration of around 30g/L. High CE percentage values were obtained (60–70%) within the ED system, which indicates that the process of ions transfer through the exchange membranes is effective even if higher feeding flow and concentrations are applied. Regarding the obtained salt removal (SR) percentage values, the present ED model showed a practical operation scenario where an optimal salt removal value of 35% was achieved within 15 minutes. The findings in this study concluded that the present ED system is superior in desalinating saline water when compared to other ED systems in the literature. The energy demands required to power the current ED system are fully supplied by a photovoltaic solar panel. A larger scale of the current ED setup could be useful in the regions that suffer from the lack of freshwater while potential access to renewable energy sources is available, especially in off-grid areas.

Numerical investigation of effective parameters of falling film evaporation in a vertical‐tube evaporator

AbstractWastewater treatment is one of the most effective solutions to manage the problem of water scarcity. Falling film evaporators are excellent technology in wastewater treatment plants. These wastewater evaporators provide high heat transfer, short residence time in the heating zone, and high‐purity distilled water. In the present study, the mechanism of turbulent falling film evaporation in a vertical tube has been investigated. A model has been developed for symmetrical two‐dimensional pure and saline water flow in a vertical tube under constant wall heat flux. The numerical simulation has been carried out by a commercial computational fluid dynamics code. The evaporation of saturated liquid film is simulated utilizing a two‐phase volume of fluid method and Tanasawa phase‐change model. The main objective of this study is to evaluate the effects of water salinity, liquid Reynolds number, wall heat flux, and liquid film thickness on the two‐phase heat transfer coefficient and vapor volume fraction. The numerical heat transfer coefficients are compared with the obtained results by Chen's empirical correlation. With a MAPE ≤ 11%, this study proves that the numerical method is highly effective at predicting the heat transfer coefficient. Moreover, the empirical coefficient of the Tanasawa model and the minimum thickness of the falling film are determined.

Advances in the Coastal and Submarine Groundwater Processes: Controls and Environmental Impact on the Thriassion Plain and Eleusis Gulf (Attica, Greece)

This study focuses on the hydrogeological conditions in the coastal (Thriassion plain) and submarine (Eleusis Gulf) environment of West Attica, Greece. Up to now, the predominant aspect for the Thriassion plain groundwater—hosted within the Neogene-Quaternary sediments—was its direct hydraulic contact with the seawater. Due to that, the coastal plain groundwater is strongly believed to be of brackish quality irrespective of the local hydrodynamic conditions. Our major goal is to evaluate the actual mechanism controlling the groundwater flow, the origin and distribution of saline water, and the existence of fresh groundwater in the submarine environment. We summarize the following: (1) groundwater of the Thriassion plain is partly discharged as an upwards leakage from deeper aquifers, (2) modern direct seawater intrusion is not possible in the Neogene-Quaternary sediments, and (3) fresh groundwater possibly exists below the sea floor of the Eleusis Gulf. The results may serve as hint of further research in groundwater resources below the Mediterranean Sea floor, and, consequently, a new perspective on water resource management could emerge.

Observation and Modeling of Low Saline Water Flow through Gulf of Mannar during December 2016

Anand, P.; Anubhav, C.A., and Albert, P.I., 2020. Observation and modeling of low saline water flow through Gulf of Mannar during December 2016. In: Sheela Nair, L.; Prakash, T.N.; Padmalal, D., and Kumar Seelam, J. (eds.), Oceanic and Coastal Processes of the Indian Seas. Journal of Coastal Research, Special Issue No. 89, pp. 20-25. Coconut Creek (Florida), ISSN 0749-0208.Indian Ocean is unique as it features the reversal of currents in relation to the monsoonal winds. During the north-east monsoon season (November-February), the East Indian Coastal Current (EICC) is known to flow round Srilanka into the South Eastern Arabian Sea (SEAS) which transports low saline waters from the Bay of Bengal (BoB). Till now, due to lack of observational data along the Gulf of Mannar (GoM), it is not evident, whether part of the water that flows from BoB is passing through the Palk Strait/Bay and GoM to reach SEAS. There are two schools of thought existing, one is that, the flow exists through this passage. Efforts have been made to prove this using simulation studies. The second thought is that the Pamban Pass as well as the Adam's Bridge act as barriers for this passage of water. To study the subject in detail, CTD observations during December 2016 along GoM and west coast of India are utilized. Analysis shows that, the surface waters along transect of GoM is lower in salinity (33 psu) than that of SEAS (34 psu) with the lowest surface salinity along the easternmost transect. Different case studies, carried out using high resolution (10 km) Princeton Ocean Model (POM), suggested that the flow exists through the GoM. The signature of low saline water (33.2 psu) in this region is also well matched with that of the observations. The study concludes that, the flow through the Palk Bay/Strait and GoM have a distinct role in bringing the water from the Bay to SEAS.

Analysis on Renewable Energy Generation of From Salinity Gradient by Reverse Electro Dialysis

Global warming and high oil price have made the world to look into renewable energy like solar, wind, fuel cells etc. A massive amount of energy is released in the process of mixing of water of different salinity. This process is known as reverse electrodialysis. In this method, the production of electricity is free from thermal pollution, no output of pollutant, no radioactive waste. The Reverse Electroddialysis (RED) is the method where the voltage can be acquiring by the change in chemical potential between the concentration and dilute solution. The process which involves the flow of saline water and dilutes solutions through a cell in which the anion and cation exchanging membranes are present in between two electrodes where the electricity is generated. The electricity generation varies from cell to cell. Different types of membrane, electrode distance, type of electrode used, the concentration of feed, which are all the factors that influence the generation of power. In the setup of reverse electrodialysis, the smaller the membrane distance and the flow path length and thinner the membranes – higher power densities are obtained. Temperature changes also play an essential role. For the increased temperature in RED, the power densities will be maximum. The practical power output obtained is limited due to concentration polarization phenomena and spacer shadow effects. Other than the concentration polarization and spacer shadow effect, the fouling of the membrane occurs, which is also leads to the less power output. By improvement of those factors which results in a significant increase in the output of the RED process. This Review work consists of work of different types of reverse electrodialysis models the recent advancement from the beginning till the date. The surface properties like transport number, water contact angle, surface roughness have also been studied. Many mathematical models have also been illustrated via thermodynamical considerations, and some of the models predict the experimental results well, and their results are established.

Have Bangladesh’s Polders Decreased Livelihood Vulnerability? A Comparative Case Study

Communities living in coastal regions are vulnerable to flooding, salinity intrusion, and natural hazards. This is aggravated by climate change. In order to reduce this vulnerability, governments have invested heavily in developing coastal infrastructures. One type of infrastructure development regards polders (i.e., pieces of land previously subject to permanent or temporal overflow that are now surrounded by embankments that prevent inundation). The impact of polderization on livelihood vulnerability is not straightforward and is therefore still poorly understood. In order to analyze such impacts, we present a comparative case study of four polders in Bangladesh that are characterized by varying societal circumstances, hydrological conditions, hydrological interventions, and different levels of community response to polderization. How does livelihood vulnerability vary temporally and spatially in polders, and what explains such variation? We use data collected via 162 surveys, 40 semi-structured interviews, and secondary research to analyze trends in the scores of the livelihood vulnerability index. Based on our analysis, we argue that after accounting for interactions amongst variables like hydrological conditions, hydrological interventions, community response, and other societal factors, livelihood vulnerability is lower in polders characterized by higher community involvement in using hydrological interventions to control the flow of saline water.