Sea Water Conversion Research Articles

Green Hydrogen Generation from Eco-Friendly and Cost-Effective Red Sea Water Using a Highly Photocatalytic Nanocomposite Film, As2O3/Poly-3-methylaniline

The primary objective of this research is to address the energy challenges by introducing an innovative nanocomposite material. This material is designed to facilitate the conversion of environmentally friendly and economically viable Red Sea water into hydrogen gas. The ultimate goal of this work is to pave the way for the development of a practical device that can be employed within households and industrial settings to directly convert water into hydrogen gas. This novel nanocomposite material synthesized through oxidative polymerization comprises As2O3 and Poly-3-methylaniline (P3MA). This material possesses an extensive absorption range, spanning up to 700 nm, and features a bandgap of 1.75 eV, making it a promising candidate for use as a photoelectrode in green hydrogen production. The unique aspect of this setup lies in the utilization of Red Sea water, a natural sacrificing agent, as the electrolyte, rendering the process eco-friendly and cost-effective. When it is employed as a photoelectrode, this material exhibits high sensitivity to green hydrogen production, generating 6 moles/10 cm2·h of hydrogen. At a voltage of −0.83 V, the current density values are measured as −0.08 mA·cm−2 (Jph) in light and −0.02 mA·cm−2 (Jo) in darkness. Furthermore, the photoelectrode’s responsiveness to light is assessed with different optical filters, revealing the optimal performance at 340 nm, where Jph reaches −0.052 mA·cm−2. These outcomes provide strong evidence of the photoactivity of the As2O3/P3MAphotoelectrode for green hydrogen production using Red Sea water. This underscores its potential for the development of an electrochemical cell for the direct conversion of sea water into H2 gas.

An innovative biomass-driven energy systems for green energy and freshwater production with less CO2 emission: Environmental and technical approaches

Considering the current crisis of fossil energies, the exploitation of renewables and green technologies is necessary and unavoidable. Additionally, the design and development of integrated energy systems with two or more output products and the maximum usage of thermal losses in order to improve efficiency can boost the yield and acceptability of the energy system. In this regard, this paper develops a comprehensive multi-aspect assessment of the operation of a new solar and biomass energies-driven multigeneration system (MGS). The main units installed in MGS are three electric energy generation units based on a gas turbine process, a solid oxide fuel cell unit (SOFCU) and an organic Rankine cycle unit (ORCU), a biomass energy conversion unit to useful thermal energy, a seawater conversion unit into useable freshwater, a unit for converting water and electricity into hydrogen energy and oxygen gas, a unit for converting solar energy into useful thermal energy (based on Fresnel collector), and a cooling load generation unit. The planned MGS has a novel configuration and layout that has not been considered by researchers recently. The current article is based on presenting a multi-aspect evaluation to study thermodynamic-conceptual, environmental and exergoeconomic analyzes. The outcomes indicated that the planned MGS can produce about 6.31 MW of electrical power and 0.49 MW of thermal power. Furthermore, MGS is able to produce various products such as potable water (∼0.977 kg/s), cooling load (∼0.16 MW), hydrogen energy (∼1.578 g/s) and sanitary water (∼0.957 kg/s). The total thermodynamic indexes were calculated as 78.13% and 47.72%, respectively. Also, the total investment and unit exergy costs were 47.16 USD per hour and 11.07 USD per GJ, respectively. Further, the content of CO2 emitted from the desgined system was equal to 10.59 kmol per MWh. A parametric study has been also developed to identify influencing parameters.

Parallel arrays of clay nanosheets sandwiched in two-dimensional nanofluidic membrane for enhanced ion transport properties

High ion selectivity and high structural stability have always been the pursuit of nanofluidic ion exchange membranes but they are often trade-offs. Herein, we built a sandwich structure by introducing parallel arrays of clay nanosheets in two-dimensional nanofluidic membrane to improve the ion transport performance. The introduction of an appropriate amount of clay nanosheets can not only redistributes internal stress and thereby increases the tensile strength but also provides higher surface charge density and thereby effectively increases ion selectivity of the membrane. The current density obtained from the sandwich structure membrane is ∼5 times than that of the homogeneous membrane and the cation mobility can reach a maximum of 0.98. When simulating the energy conversion of seawater and river water, the maximum output power density achieved through the membrane is 0.70 W m−2, which is increased by ∼6 times. Interestingly, it significantly weakens the internal resistance from 100 to 30 kΩ and the energy barriers from 4.56 to 2.13 kJ mol−1 of ion permeation in the entire regime although the clay nanosheets arrays increases the thickness of the membrane. This strategy of introducing negatively charged nanosheets of natural minerals to enhance ion transport properties provides a new idea for the enhancement and application of salinity gradient energy harvesting membranes.

Application of nanomaterial based alkaline electrolyzer for hydrogen production in renewable energy-driven system: Multi-criteria assessment, environmental and exergoeconomic approaches

An alkaline electrolyzer is a traditional equipment to generate hydrogen. Improving the yield of electrolyzers has recently captured much attention. In this regard, the utilization of carbon-coated nanomaterial structures is a state-of-art method. On the other hand, considering the current crisis of fossil energies, the exploitation of renewables and green technologies is necessary and unavoidable. Additionally, the design and development of integrated energy systems with two or more output products and the maximum usage of thermal losses to enhance productivity can increase the flexibility and acceptability of the energy system. In this regard, the current paper develops a framework for the performance of a new solar and biomass energies-driven multigeneration system (MGS). The main units installed in MGS are three electric energy generation units based on a gas turbine process, a solid oxide fuel cell unit (SOFCU) and an organic Rankine cycle unit (ORCU), a biomass energy conversion unit to useful thermal energy, a seawater conversion unit into useable freshwater, a unit for converting water and electricity into hydrogen energy and oxygen gas via a nanomaterial-based alkaline electrolyzer, a unit for converting solar energy into useful thermal energy (based on Fresnel collector), and a cooling load generation unit. The planned MGS has a novel structure and layout that has not been considered by researchers in previous papers. The current article is based on presenting a multi-aspect evaluation in order to investigate thermodynamic-conceptual, environmental and exergoeconomic analyzes. The outcomes indicated that the planned MGS can produce about 6.31 MW of electrical power and 0.49 MW of thermal power. Furthermore, MGS is able to produce various products such as potable water (∼0.977 kg/s), cooling load (∼0.16 MW), hydrogen energy (∼1.578 g/s) and sanitary water (∼0.957 kg/s). The overall energy and exergy productivities were measured as 78.13% and 47.72%, respectively. Also, the total investment and unit exergy costs were 47.16 USD per hour and 11.07 USD per GJ, respectively. Further, the content of carbon dioxide released from the planned system was equal to 10.59 kmol per MWh. A parametric study has been also developed to identify influencing parameters.

Methods to enhance the productivity of solar still: A review

Water is the main factor for livings on earth. The requirement for potable water is rising gradually because of the rapid population growth. 71% earth’s area is occupied by oceans. So the availability of brine & brackish water is around 75% but for the human being all purposes like drinking, laboratories purposes & automobiles batteries we need fresh water. To conquer the availability scenario of clean water scarcity, the conversion of seawater into freshwater is needed. In the present era, there are various techniques available for conversion but solar distillation is the most economical technique to gain potable water. To enhance conversion factors different solar still studied and compared with several output parameters, also this paper demonstrates the enhancing yield parameter through experimentation at various depth, different phase change material, design modification, etc. & their prospect.

A new type of superhydrophobic membrane seawater desalination device

In response to the existing problems of the current seawater desalination equipment, this project designed a new type of super-hydrophobic membrane tangential distillation seawater desalination device with simple structure, low energy consumption, high seawater conversion rate, operation and reduced maintenance costs. The successful implementation of the project will not only provide economical and applicable freshwater equipment for the living water of island residents, but also have potential application value for China’s coastal defense construction and offshore development.

Catalytic conversion of seawater to fuels: Eliminating N vacancies in g-C3N4 to promote photocatalytic hydrogen production

The use of solar energy to decompose seawater and produce hydrogen is of great significance in solving the energy crisis. Numerous studies have shown that vacancies can significantly improve photocatalytic activity due to their electron-rich nature. However, our recent research has shown that materials with vacancies are not suitable for photocatalytic reactions in seawater. In this study, g-C3N4 with rich N vacancies was selected as the research object, and urea was used as the precursor; in this system, the N vacancies in g-C3N4 could be effectively reduced by the addition of ZIF-8 (ZCNQx). The activity of ZCNQ40 was 5.6 times higher than that of g-C3N4 in fresh seawater, but only 3.1 times higher in freshwater. Based on the analysis of the experimental results, we believe that g-C3N4 has a limiting relationship between H+ adsorption catalysis and H2 product desorption. In addition, seawater contains many heteroatoms that will also compete with proton (H+) reduction. The results of our study show that catalysts with vacancies are not necessarily suitable for catalytic reactions in seawater media. This research will stimulate new ideas for research into the conversion of solar energy to chemical energy in seawater media.

A Ti(III) reduction method for one-step conversion of seawater and freshwater nitrate into N2 O for stable isotopic analysis of 15 N/14 N, 18 O/16 O and 17 O/16 O.

The nitrogen and oxygen (δ15 N, δ18 O, and δ17 O values) isotopic compositions of nitrate (NO3 - ) are crucial tracers of nutrient nitrogen (N) sources and dynamics in aquatic systems. Current methods such as bacterial denitrification or Cd-azide reduction require laborious multi-step conversions or toxic chemicals to reduce NO3 - to N2 O for 15 N and 18 O isotopic analyses by isotope ratio mass spectrometry (IRMS). Furthermore, the 17 O composition of N2 O cannot be directly disentangled using IRMS because 17 O contributes to mass 45 (15 N). We describe a new one-step chemical conversion method that employs Ti(III) chloride to reduce nitrate to N2 O gas in septum sample vials. Sample preparation takes only a few minutes followed by a 24-h reaction producing N2 O gas (65-75% recovery) which partitions into the headspace. The N2 O headspace was measured for 15 N, 18 O and 17 O by IRMS or laser spectrometry. IRMS and laser spectrometric analyses gave accurate and reproducible N and O isotopic results down to 50 ppb (3.5 μM) NO3 -N, similar in precision to the denitrifier and Cd-azide methods. The uncertainties for dissolved nitrate reference materials (USGS32, USGS34, USGS35, IAEA-NO3 ) were ±0.2‰ for δ15 N values and ±0.3‰ for δ18 O values using IRMS. For laser-based N2 O isotope analyses the results were similar, with an δ17 O uncertainty of ±0.9‰ without any need for 15 N correction. Advantages of the Ti(III) reduction method are simplicity, low cost, and no requirement for toxic chemicals or anaerobic bacterial cultures. Minor corrections may be required to account for sample nitrate concentration variance and potential chemical interferences. The Ti(III) method is easily implemented into laboratories currently using N2 O headspace sampling apparatus. We expect that the Ti(III) method will promulgate the use of N and O isotopes of nitrate in important studies of nutrient dynamics and pollution in a wide range of aquatic ecosystems.

Hydrate-Based Desalination Using Cyclopentane Hydrates at Atmospheric Pressure

The use of a hydrate-based technology in seawater desalination is an interesting potential hydrate application since salt ions would be excluded from the hydrate crystal lattice. In order to better understand the hydrate-based desalination process, experiments have been conducted using cyclopentane (CyC5, sII) hydrates, which can be formed at atmospheric pressure and temperatures below 7.7 °C. The hydrate formation experiments were performed at various subcoolings for aqueous solutions with different salinities in a bubble column. The hydrate formation times decreased and the hydrate conversion increased with increasing subcooling and agitation. Various hydrate-former injection methods were studied, with the most effective method involving spraying finely dispersed CyC5 droplets (around 5 μm in diameter) into the water-filled bubble column. The latter method resulted in a 2-fold increase in seawater conversion to hydrate crystals compared with injecting millimeter-scale CyC5 droplets. A desalination effic...

Experimental scrutinization on conversion of seawater into drinking water using solar energy

The paper investigates the experimental studies on conversion of seawater into drinking using solar energy with the help of single basin double slope solar still unit.

Discourse and desalination: Potential impacts of proposed climate change adaptation interventions in the Arizona–Sonora border region

The specter of climate change threatens fresh water resources along the U.S.–Mexico border. Water managers and planners on both sides of the border are promoting desalination—the conversion of seawater or brackish groundwater to fresh water—as an adaptation response that can help meet growing water demands and buffer against the negative impacts of climate change on regional water supplies. However, the uneven distribution of costs and benefits of this expensive, energy-intensive technology is likely to exacerbate existing social inequalities in the border zone. In this paper, we examine the discourses employed in the construction of the climate problem and proposed solutions. We focus our analysis on a proposed Arizona–Sonora binational desalination project and use insights from risk and hazards literature to analyze how, why, and to what effect desalination is emerging as a preferred climate change adaptation response. Our risk analysis shows that while desalination technology can reduce some vulnerabilities (e.g., future water supply), it can also introduce new vulnerabilities by compounding the water-energy nexus, increasing greenhouse gas emissions, inducing urban growth, producing brine discharge and chemical pollutants, shifting geopolitical relations of water security, and increasing water prices. Additionally, a high-tech and path-dependent response will likely result in increased reliance on technical expertise, less opportunity for participatory decision-making and reduced flexibility. The paper concludes by proposing alternative adaptation responses that can offer greater flexibility, are less path dependent, incorporate social learning, and target the poorest and most vulnerable members of the community. These alternatives can build greater adaptive capacity and ensure equity.

Desalination Activities in Late 17th Century England

During the late 17th century, especially during the reign of Charles II, there was a burst of interest in seawater desalination in England. This was due largely to the desire of Charles II to restore England's naval prominence, weakened during civil wars and the interregnum, and to the energies and influence of Secretary of the Admiralty Samuel Pepys. Prominent among the activities was a lengthy, high-profile legal dispute between patent holders of competing desalination devices. At the height of this fracas, commemorative medals were struck off, an epic poem was written, and political strings were pulled. Robert Boyle, eminent scientist and formulator of laws relating temperature, volume, and pressure of gases, was a key figure in the fray. This article recounts these and related activities of the period when interest in seawater conversion reached the top levels of government, only to fade away as actual technical accomplishments failed to live up to hopes and expectations.

Seafaring Solution for Regional Water Supplies

This article presents the Seawater Conversion Vessel (SCV), an ocean‐going ship that houses a self‐contained seawater desalination plant. The SCV includes a multi‐depth intake line and pump station to draw water from the sea; microfiltration, reverse osmosis, and posttreatment systems to convert the seawater to potable water; a sophisticated mixing and dispersion system to properly dispose of the brine; and a variety of means by which the potable water can be transported to shore. The article discusses the advantages of the SCV over land‐based desalination facilities, minimizing impingement and entrainment effects, cleaning and discharging the brine, use of a tug barge to deliver desalinated water to the shore in highly sensitive shoreline areas, and coastal and global interest in the SCV.

NF membrane characteristics and evaluation for sea water processing applications

Nanofiltration (NF) has not been well defined. Many authors define an NF membrane as any RO membrane that is not as highly salt rejecting as the state of the art. The authors of this report define an NF membrane as a membrane that has a sodium chloride permeability that is proportional to the sodium chloride concentration to a power greater than 0.4. The permeabilities of both sodium chloride and potassium bicarbonate are proportional to the solute concentration to the power of about 0.5 for a typical NF membrane. HL-NF membranes reject sulfate ions very well, typically greater than 99%, and divalent cations fairly well, typically 80–95%. Dr. Ata Hassan of SWCC reported the NF pretreatment results from the Umm Lujj SWRO NF pretreatment plant at the IDA conference in Kuwait in March 2002. The nanofiltration pretreatment step reduces total hardness from 7500 to 220 ppm, total dissolved solids from 45,460 to 28,260 ppm, and chloride from 21,587 to 16,438 ppm. With the ionic makeup at the Umm Lujj plant, sulfate was rejected at a rate better than 99%, magnesium at 98%, calcium at 92% and bicarbonate at 44%. The remained of these ions were less than 2 ppm for sulfate, 29 ppm for magnesium, 40 ppm for calcium and 17 ppm for bicarbonate. Without pushing the membrane and the equipment to their flux and pressure limits, the nanofiltration equipment operated at a 65% conversion rate and the reverse osmosis equipment at a 56% conversion rate, providing an overall seawater conversion rate of 36.4%. This compared with the conversion rate or a parallel plant of 28%, this represents a 30% increase in overall recovery.

Performance evaluation of a mechanical vapor compression desalination system

Desalination processes are making rapid technological progresses for the conversion of seawater to fresh water. In this study, experiments have been performed on a mechanical vapor compression desalination system (MVC). The MVC pilot plants has two vertical evaporator condensers and its rated capacity is about 1 m3/d. The performance of the system has been evaluated under variable operating conditions, where the different values of brine recirculation rate and compressor speed were considered. Throughout the experiment, the top brine temperature was kept constant at a value of 103°C. For different concentrations ranging from 20,000 ppm to 33,000 ppm, the influence of increasing brine recirculation rate and compressor speed were observed. It has been found that the performance is better with lower concentration and increased compressor speed. The highest average PR obtained was 2.52.

Melting and mingling of phonolitic pumice deposits with intruding dykes: an example from the Otago Peninsula, New Zealand

A mound of bedded phonolitic pumice lapilli ash was deposited on the marine shelf (modern Otago Peninsula, New Zealand) during a shallow subaqueous eruption in the Miocene. Basaltic dykes subsequently intruded the unconsolidated pumice deposit and formed an unusual peperite. Dyke–sediment interaction began with weak steam-driven mixing, accompanied by fluidisation at the contact zone that produced a metres-broad zone in which bulbous tongues (up to 3 m) of the dykes extended into, and locally engulfed, host sediment. Irregular, sinuous contacts of dykes with the pumice are marked by black glass that formed by partial melting, shearing and remoulding of the glassy pumice. Such melting and remoulding of host sediment is not a typical peperite feature. Temperature evolution, volume of water vapour, load pressure and time, as well as initial contact temperature, control the welding and remoulding of pumice and glass shards. A slow cooling rate of the dykes at the dyke contacts is inferred from remoulding textures, and is attributed to continuous feeding of the dyke. Seawater may have promoted softening and remoulding of the pumice because Na and K, if partially taken into the glass structure, can decrease the melting point of glass dramatically and reduce the viscosity of the shards. Remoulding may have occurred by continuous conversion of seawater in the peperite to steam, which is inferred to have enhanced transfer of Na and K from seawater to pumice glass.

Water for the desert—a viewpoint

The dwindling water resources combined with climatological conditions which severely affected several areas of the world, particularly those where subsistence agriculture and nomadic animal husbandry are the mainstay of the way‐of‐life, require immediate action. Some schemes have been proposed which at first sight were to be considered engineers’ dreams. From seawater conversion, to iceberg towing and long distance piping, solutions are edging from the realm of fantasy to conceivable achievements. Perhaps the mighty Zaire River may be one day tapped to quench the thirst of parched Central Africa or fill the jugs of Arabia.

A novel 2500 GPD 5-effects wiped-film rotating-disk vapor-compression module; preliminary results

A laboratory model wiped-film rotating-disk (WFRD) vapor-compression compression evaporator with a capacity of 300 liters/day (80 gpd) was conceived, designed, and built in the late sixties at the Sea Water Conversion Laboratory, University of California at Berkeley. Preliminary data obtained from this model showed exceptionally high overall heat transfer coefficient, U, in excess of 28 kW/m 2C (5000 Btu/hft 2F). Results from later data with precise instrumentation confirmed the earlier results and showed even higher values for U. Thermoeconomic analysis of multieffect vapor-compression systems to reclaim 95 percent of agricultural drainage water at the San Joaquin Valley in California showed that the use of multieffect VC systems instead of convention single effect VC systems reduces energy consumption. It also showed that the ratio of U in the evaporator to its cost per unit area of heat transfer has very strong influence on distilled water cost; the higher the ratio, the lower the distilled water cost. The analysis also showed that because of the exceptionally high value of U in the WFRD evaporator and based on data obtained from the laboratory model at Los Banos, California uisng agricultural drainage water, its use in a 5-effect VC system will reduce product water cost by a factor of 2 and energy consumption by a factor of 3 as compared to off-the-shelf single effect conventional VC systems. A semicommercial 2500 gal/day five-effect vapor-compression WFRD evaporator module was designed, built and tested with tap water. Preliminary data were obtained. The results from these data show an average value of U to be about 20 kW/m 2C (3500 Btu/hft 2F) and energy consumption by the compressor between 3.6 and 5.1 kWh/m 3 (13.6 and 19.3 kWh/1000 gal) of product water.

Computer code for optimizing MSF desalination plant

Egypt faces the prospect of population growth pressing on available agricultural land resources. A very large areas of coastal desert could be helpful in population density redistribution and of great economical interest, with the installation of a suitable water supply. Of the many desalination processes, the Multi-Stage Flash (MSF) desalination process is still the most developed and reliable technology for large scale conversion of sea water to fresh water. In this paper, a computer code was developed for optimizing a large scale MSF plant. This code can calculate the optimum design for the plant, and the minimum cost of product fresh water, as a function of both design and operating variables. Sample results obtained using this code for the Egyptian conditions are presented. The effect of, energy and material costs, the chemical treatment types, and the feed water salinity on the optimum performance ratio and the minimum fresh water cost are drawn.

Computer code for optimizing MSF desalination plant

Egypt faces the prospect of population growth pressing on available agricultural land resources. A very large areas of coastal desert could be helpful in population density redistribution and of great economical interest, with the installation of a suitable water supply. Of the many desalination processes, the Multi-Stage Flash (MSF) desalination process is still the most developed and reliable technology for large scale conversion of sea water to fresh water. In this paper, a computer code was developed for optimizing a large scale MSF plant. This code can calculate the optimum design for the plant, and the minimum cost of product fresh water, as a function of both design and operating variables. Sample results obtained using this code for the Egyptian conditions are presented. The effect of energy and material costs, the chemical treatment type, and the feed water salinity on the optimum performance ratio and the minimum fresh water cost are drawn.