Desalinated Water Production Research Articles

A low-carbon dual-functional evaporator with photothermal and catalytic properties for enhanced VOCs removal during water evaporation

Solar interface distillation technologies are widely used for seawater desalination, wastewater treatment, and clean water production. However, during evaporation, volatile organic compounds (VOCs) in the water often evaporate coincidently with the water vapor, presenting a major pollutant challenge. Combining solar evaporation with advanced oxidation processes (AOP) is a potential solution for simultaneous water purification and VOC degradation. Herein, a dual-functional sponge photothermal evaporator (MBC-SA/MS) was designed to assess the efficacy of this approach. A simple porous sponge embedded with a composite catalyst, comprising MoO3−x, BiOCl, and CNT, was able to demonstrate simultaneous photothermal evaporation and catalytic degradation. MBC-SA/MS exhibited exceptional photothermal conversion efficiency and robust catalytic activity, achieving an evaporation rate of 2.1 kg m−2 h−1 under 1.0 sun intensity. Effective mitigating of phenol emissions was observed through persulfate activation resulting in 90 % phenol degradation. Life cycle assessment (LCA) confirmed this evaporator system had low environmental impact and was sustainable. This research presents a new compelling strategy for tackling VOC pollution and simultaneously enhancing water purification via solar interfacial evaporation.

Productivity, energy, and exergy analyses of a water desalination system-based vortex tubes with different configurations: An experimental implementation

The present implementation explores the use of vortex tubes (VTs) as an alternative thermal technology for water desalination systems (WDSs). VTs are utilized to provide hot air for evaporating salt water in the evaporator, while simultaneously supplying cold air to condense the water vapor in the condenser. The study investigates the influence of a number of operating parameters, including inlet water temperature (Ti,w), cold mass ratio (CR), and vacuum pressure (pvac) on the performance of WDS-based VTs through experimental analysis. Different configurations of VTs are tested for WDS applications, including WDS-based single vortex tube (VT), WDS-based two series vortex tubes (2SVTs), and WDS-based two parallel vortex tubes (2PVTs). Performance metrics such as the evaporation heat (QEvap), desalinated water production (DWP), gain output ratio (GOR), and exergy performance are evaluated for each configuration. Results show that the WDS-based 2SVTs exhibits the highest QEvap; while the WDS-based 2PVTs demonstrates the lowest value. Correlations are proposed to predict DWP for different configurations of WDS based on pvac, Ti,w, and CR with a maximum deviation of ±12.2 %. Furthermore, the WDS-based 2SVTs achieves the best GOR of 2.5 at an inlet water temperature of 80 °C, representing a significant improvement compared to the WDS-based VT and 2PVTs. The exergy efficiency (ηex) increases with higher CR, and the WDS-based 2SVTs ensures the best exergy performance, and its maximum overall ηex equals 78.2 %.

Pilot-scale testing of a multi-tube type falling film distillation column equipped with a biphasic thermosyphon as a new alternative for the desalination of brackish water and seawater

This paper proposes an innovative technology for desalinating brackish water and seawater using a multi-tube type falling film distillation column integrated with a biphasic thermosyphon. Based on the literature survey, this proposal has not been previously explored. In this study, the viability of the pilot-scale application of this technology for desalination was tested, and the process performance was evaluated in terms of distillate flow rate, salinity removal, and energy consumption, considering different experimental conditions. Synthetic solutions containing 10.0 and 35.0 g/L of sodium chloride were used to simulate brackish water and seawater salinities, respectively. The thermal desalination pilot plant integrating a compact falling film distillation column and a biphasic thermosyphon demonstrated high effectiveness, consistently producing desalinated water with a conductivity below 10 μS cm−1. Considering both concentrations, the optimal condition for desalinated water production was a feed temperature of 85 °C, a vapor chamber temperature of 121 °C, and an energy consumption of 16 kW. This new technological option’s energy consumption is approximately 33 % lower than that of a simulated flash distillation column operating under similar conditions. In conclusion, this study presents promising results, establishing falling film distillation technology as a viable alternative for desalinating brackish water and seawater.

Techno-economic optimization and working fluid selection of a biogas-based dual-loop bi-evaporator ejector cooling cycle involving power-to-hydrogen and water facilities

Biogas-fueled decentralized energy systems featuring gas turbines emerge as pivotal players in the quest for more adaptable and eco-friendly energy solutions. This study presents the design of a cutting-edge multigeneration system that harnesses the potential of a gas turbine coupled with ejector-driven dual-loop bi-evaporator technology, reverse osmosis desalination, proton exchange membrane electrolysis, and an organic Rankine cycle. The research encompasses an extensive sensitivity analysis and deploys a genetic algorithm-based optimization technique. Through meticulous Optimization, the system achieves remarkable outcomes, including electricity generation, cooling capacity, heating capacity, desalinated water production, and hydrogen yield, measured at 957.3 kW, 231.4 kW, 272.3 kW, 7.336 kg/s, and 0.99 kg/h, respectively. Notably, this performance surpasses the base case by 2% and 8.9%, yielding exergy efficiency and total unit cost improvements of 33.3% and 16.4 $/GJ. Among the critical decisions made was selecting an organic working fluid for the organic Rankine cycle. Through rigorous evaluation, isobutene emerged as the optimal choice, demonstrating significantly improved output power compared to alternatives. Isobutane as the working fluid led to a substantial increase in overall exergy efficiency and a resultant total unit cost of 18.06 $/GJ, accompanied by an impressive 23.48% exergy efficiency.

Shortage Analysis and Strategies for the Water Resource in Saudi Arabia under the Rapid Development of the Tourism Industry

This study evaluates water sustainability in Saudi Arabia amid expanding tourism using a mixed-methods approach. Primary data were collected through surveys targeting 150 stakeholders in water management and tourism, while secondary data were sourced from official reports. Quantitative analysis revealed significant challenges, with an average daily per capita water consumption of 299 liters and severe stress in regions like Riyadh and Jeddah. Groundwater quantity for 2022 was recorded at 1.48 km³, and desalinated water production totaled 1.95 km³, revealing a supply-demand gap of 1.82 km³. The correlation analysis indicated a significant positive relationship (r=0.440) between tourism growth and water demand. Survey results showed 70% of respondents reported no difficulties in accessing clean water during Hajj, while 30% indicated occasional issues. Stakeholders emphasized the need for integrating renewable energy with desalination to reduce operational costs and carbon emissions. The study recommends enhancing Reverse Osmosis (RO) technology with solar energy to improve sustainability and efficiency, aligning with Saudi Arabia's Vision 2030. These findings highlight the necessity for sustainable water management strategies to balance economic growth with resource sustainability, guiding policymakers in developing effective practices for future water security.

Theoretical and experimental analysis of sea ice centrifugal desalination and supercooled water production for slurry ice

This study presents a comprehensive investigation of centrifugal desalination of sea ice and the production of slurry ice from supercooled water. A mathematical model for centrifugal desalination was established and validated through experiments. The results displayed a high level of accuracy in both the theoretical and experimental analyses, with an average goodness of fit of approximately 0.94. An experimental platform is established to produce supercooled water, using different types of water as ice-making solutions. The slurry ice is more suitable for centrifugal desalination than solid ice, and it can be obtained by disrupting the supercooled state of supercooled water, with finer ice crystals produced through ultrasonic supercooling release compared to natural methods. Decreasing the refrigerant temperature benefits enhancing the supercooling degree while compromising the stability of supercooled water generation. The stability is investigated with variations in refrigerant temperature to generate a solution temperature 2.0 °C higher than the refrigerant. When the supercooling degree is 1.0 °C, all of these solutions have a high stability of 80 %, however, it becomes worse as the supercooling degree increases. At the supercooling degree of 2.0 °C, saltwater has the highest stability of only 35 %, and seawater has the lowest stability of 15% due to its complicated composition. This phenomenon also reveals that conducting experiments using saline solution instead of seawater can lead to significant misleading effects. Additionally, the impact of flow rate on the supercooling degree is investigated, showing a minor influence.

Advancing solar-powered hybrid FO-MD desalination: Integrating PVT collectors and PCM for sustainable water production in residential building

The global focus on water desalination using solar energy is particularly pronounced today. Previous studies have affirmed the efficiency of the Forward Osmosis (FO) and Membrane Distillation (MD) hybrid desalination system. The Photovoltaic Thermal (PVT) solar system, which generates both thermal and electrical energy, is complemented using Phase Change Material (PCM). PCM, known for storing and releasing significant heat during phase change, is used in the evening to meet the thermal needs of the system. Additionally, an integrated battery system stores the electrical energy generated by PVT, ensuring the system's electricity requirements are sustained during the night. A comprehensive numerical model, PVT-PCM-FO-MD, has been developed to analyze the proposed system. Operating seamlessly under natural conditions for a typical day on March, June and September, the proposed system can produce freshwater continuously over a 24-hour period. To assess system performance, three PCM thicknesses (2 cm, 4 cm, and 6 cm) were employed. Designed for small-scale applications, this system is well-suited for brackish water desalination in remote areas. Notably, the highest water production recorded was 213.25 L during a 24-hour operation and the MD unit exhibited an impressive 83.78 % evaporation efficiency during the typical day on June, with nighttime efficiency reaching 37.07 %, specifically at 3 am, utilizing a 2 cm PCM thickness in the solar energy system and it was 37.22 % at the same hour and PCM thickness in September. This study further explores the impact of initial brackish water salinity on water production after 24 h and investigates the influence of the initial draw solution concentration in the draw tank on desalinated water production. The study found that despite varying initial salinity levels, the difference in water produced at the end of the day was not exceeding 1.6 L.

Enhancing the electricity and desalinated water production from solar chimney power plants through integration with nuclear power plants: A case study in Jordan

A new energy generation system combining a solar chimney power plant (SCPP) with a nuclear power plant (NPP) cooling tower has been developed and assessed in Irbid, Jordan. The surplus hot air from the NPP is directly routed into the SCPP collector, increasing the initial air temperature and boosting the air profile of the SCPP, improving the air velocity inside the chimney and boosting electricity and water production. The integration of these two systems (SCPP+NPP) has shown significant improvements in electricity and water production compared to a standalone SCPP. The integrated system provides reliable electricity production throughout the day (24/7), thanks to the contribution of heat from the NPP side. Key results include a maximum electricity production rate of about 238 kW at approximately noon, twice the productive value of a conventional SCPP. The average monthly water and electricity production increased from 9.44 ktons and 25.73 MWh in the SCPP to 22.96 ktons and 63.81.64 MWh in the integrated system. The SCPP+NPP system peaks electricity production of 69.4 MWh in December, underscoring the positive influence of the added nuclear heat. While March emerges as the month of the maximum of water production (25.6 ktons) in the SCPP+NPP system, the SCPP water production peaks at 14.9 ktons in July. The results also show that the integrated system demonstrates a remarkable monthly electricity and water production of 63.81 MWh and 22.96 ktons, surpassing the standalone SCPP's production (25.73 MWh and 9.44 ktons), respectively. These results demonstrate this innovative solution's potential for optimizing excess heat produced by the NPP and the potential to revolutionize the energy industry.

A gravity-induced desalination technology effectively improving the freshwater production efficiency of freeze desalination

Low desalination efficiency and water production efficiency limit the commercial application of freeze desalination (FD) technology. In this study, three freezing temperatures were set to carry out single-stage progressive freezing desalination of brackish water in southern Xinjiang, China. The ice were melted using conventional methods and gravity-induced desalination (GD), and the salt migration law during the icing and melting process was studied. The effect of GD technology on the improvement of the output of frozen desalinated produced water was quantitatively analyzed using scenario simulation. Experimental results showed that salts accumulated towards concentrated water during FD process. The ice total dissolved solids (TDS) increased with decreasing freezing temperature, which was linearly and positively correlated with the raw water TDS. GD efficiency was significantly affected by the salt concentration of ice crystals. In the first stage (the first 450 mL), ice-melt water was salt explosive dissolution, with salt drained mass accounted for more than 85% of the total salt mass. During GD process, exponential decay of ice-melt water TDS (TDSI) was observed with increasing ice-melt water amount. Through the simulation of the two exponential equation scenarios, it was found that Scenario II (mixed water TDSI as the target value) had significantly higher water yield and production rate than Scenario I (TDSI as the target value), with an increase of more than 23%. The algebraic relationship between TDSI of mixed water and the amount of ice-melt water was derived. GD technology can effectively improve the freshwater output efficiency of the FD process, which is manifested by the fact that the ice crystals of the FD process cannot produce freshwater using conventional melting. Scenario II can produce freshwater as high as 69.83% of the total amount of the GD ice-melt water. The GD technology performed increased multiplicatively in WPdv (decrease in water production) and WPRdv (decrease in water production rate) when the TDSI of the mixed water demanded by the user was low. When FD and GD are combined to desalinate salt water, lowering the freezing temperature can significantly increase the freshwater yield, breaking the limitation of freezing temperature for FD. Therefore, an automated, energy-saving freeze desalination-gravity desalination device capable of realizing the collection of the product water according to the users' needs was conceptualized. This study provides new ideas and algorithms for accurately assessing the efficiency of water production in the combined desalination of saltwater by FD and GD.

Performance analysis of heat pump polygeneration system

A heat pump polygeneration system is a promising technology to meet daily needs such as drinking water, power, space cooling or heating, and hot water generation. This work is focused on integrating the solar heat pump and two-stage humidification–de-humidification with a minimum space requirement. In this integrated cycle, the desired outputs i.e. condenser heat and evaporator heat are used for maximizing hot water and desalinated water production with minimal thermal pollution. For warm or hot air generation, an air reheater device is used after the heat pump. By using the switching operation, the air reheater is used accordingly as per climatic conditions. So in this integrated cycle, a coconut coir-packed humidifier is used for the humidification process, and a water-cooled heat exchanger and heat pump evaporator are used for the dehumidification process to meet the desired outputs from the system. The MATLAB simulation tool is used to simulate the thermodynamic model of the integrated cycle, and it is focused on studying the effect of mass flow rate, atmospheric temperature, relative humidity, evaporator temperature, and hot/cold water temperature, on outputs, as well as the energy conversion factor of the plant and cycle. At 25°C ambient air temperature, the energy conversion factor of the plant and cycle are 0.866 and 2.2, respectively. Similarly, at 75% humid air and 35°C surrounding air temperature, the gained output ratio and coefficient of performance are 4.03 and 1.964, respectively. And also, the plant and cycle energy conversion factors are 0.903 and 2.4.

Experimental analysis on hybrid adsorption and open air cycle humidification dehumidification (AD–OHD) desalination system

In the current status, an Adsorption Desalination System (ADS) has been found to have lower water production capacity than conventional desalination technologies. This study proposes a hybrid desalination system integrating the Adsorption (AD) and Open air cycle Humidification-Dehumidification (OHD) process to overcome the challenge of lower water production capacity in ADS. This hybrid system known as AD-OHD system comprises of a single bed ADS and a Humidification-Dehumidification (HDH) unit. The main objective of this work is to analyse the performance of the hybrid AD-OHD system based on parameters such as Gain Output Ratio (GOR) and amount of desalinated water production. The performance of the hybrid AD-OHD system is studied under three different operating conditions of switching (tswt) and sorption time (tspt), namely, tswt > tspt, tswt = tspt, and tswt < tspt. The results indicate that the optimal working condition is achieved when the hybrid AD-OHD system operates at condition tswt < tspt. The amount of desalinated water and GOR under the optimal condition is found to be 1.12 l/h and 0.78, respectively. The study also conducts experimental investigations to evaluate the GOR of the hybrid AD-OHD system under different operating conditions, including the temperature of the water entering the evaporator and the temperature of the hot and cooling water input to the adsorbent bed. Experimental data indicates a positive correlation between GOR and hot water temperatures, while increased cooling water temperature reduce GOR due to reduced adsorption behaviour. Although the evaporator inlet water temperature initially boosts GOR, it declines as the adsorption capacity diminishes. The study highlights the superior performance of the hybrid AD-OHD system compared to both the standalone single-bed ADS and open cycle HDH desalination systems. The hybrid AD-OHD desalination system exhibits an 80 % improvement over the single-bed ADS system and a 50 % improvement over the open cycle HDH system in desalinated water production. Additionally, a theoretical model of the adsorption desalination cycle is developed and validated, demonstrating the viability of the AD-OHD system for desalination applications.

A geothermal energy driven integrated energy system for fresh water and power production

Geothermal energy can play a crucial role in the global energy transition towards more sustainable and renewable sources. It can contribute in numerous ways including renewable and clean energy, baseload power generation, energy independence and security, heating and cooling applications, economic benefits and transition support for fossil fuel-dependent regions. Considering the modest deployment of geothermal energy regardless of its immense potential, this study explores the better utilization of geothermal energy for multigeneration purposes that also improves the system efficiencies. In this study, a binary-type geothermal-based system is developed for multigeneration including power generation, seawater desalination and hot water production. The system incorporates an isobutane entailing organic Rankine cycle (ORC) to generate electrical power and a flash distillation system for seawater desalination. A detailed thermodynamic analysis including first and second law efficiency assessment is performed to depict the performance of the designed concept. The system entails a power output of 2262 kW and seawater desalination rate of 11.09 kg/s. The energy efficiency of the overall system is evaluated to be 23.5 %. Also, the exergy efficiency is found to be 28.9 %. In addition, the ORC energetic efficiency is determined to be 7.9 % and the exergetic efficiency is evaluated as 51.1 %. Moreover, the flash distillation subsystem has energetic and exergetic efficiencies of 9.3 % and 2.7 % respectively. Several parametric studies are performed to investigate the effects of varying system conditions and operating parameters on system efficiencies.

Solar driven desalination system for power and desalination water production by concentrated PVT and MED system

Abstract In this paper, a thermodynamic study of the combination of Concentrated Photovoltaic Thermal (CPVT) and Multi Effect Desalination (MED) system was conducted. CPVT produces electricity, and the heat produced in CPVT is used for the MED system. Engineering Equation Software (EES) was utilized to simulate this system. The effect of CPVT parameters (area, concentration ratio, and average solar radiation) and MED parameters (effect number and temperature of heating steam) were investigated on the produced heat, produced power, exergy destruction, total mass flow rate (FR) of desalinated water, total FR of feed water, heating steam FR and total brine FR. The range of changes for CPVT surface, concentration ratio, and average solar radiation was considered from 2000 m2 to 20000 m2, from 5 to 15 and from 400 W/m2 to 1100 W/m2, respectively. Based on obtained results, as the surface area of the solar panel, the ratio of concentration, and average solar radiation increase, the heat produced increases. Transferring this heat to the MED unit increases the total FR of desalinated water. But it has no significant effect on the Gain ratio (GOR). As the surface area of the solar panel increases from 10000 m2 to 12000 m2, the average radiation intensity increases from 800 W/m2 to 1000 W/m2, and the concentration ratio increases from 10 to 12 in effect the number of 4 and steam temperature of 70 °C, the total mass FR of desalinated water increases by 29 %, 23 %, and 20 %, respectively.

Multi-objective study and optimization of a solar-boosted geothermal flash cycle integrated into an innovative combined power and desalinated water production process: Application of a case study

Zero-emission hybrid renewable energy resources have been introduced as a viable solution for international programs aimed at eliminating greenhouse gases. Consequently, this research is motivated to propose a novel solar-boosted integrated geothermal flash cycle-driven combined system for the simultaneous production of electricity, heating load, and desalinated water. The system comprises the integration of a geothermal flash cycle, a solar power tower, a dual-loop organic flash cycle, a humidification-dehumidification desalination cycle, and a multi-effect desalination unit. The proposed model is evaluated from three perspectives: energetic, exergetic, and economic. A seasonal case study is conducted for Jiangsu, China. The results demonstrate a generated desalinated water rate of 28.46 kg/s, a total exergy destruction of 4517 kW, an exergetic efficiency of 21.9%, and a payback period of 4.74 years. Furthermore, a combined MOPSO and LINMAP method is employed to optimize the proposed model in three scenarios. In the first scenario, the objectives are defined as the exergetic efficiency and the exergy destruction rate of the system, which yield optimal values of 22.39% and 4310.21 kW, respectively. The second scenario focuses on the rate of generated desalinated water and the rate of exergy destruction of the system, resulting in objective function values of 27.94 kg/s and 4451.34 kW, respectively. In the third scenario, NPV and exergy destruction rate are the objective values with obtained values of 1.983 $M and 4420 kW, respectively.

Construction of covalent organic framework evaporator based on Bi/BiOCl floating layer and its application in solar desalination and clean water production

Solar interface heating evaporators are widely used and have been able to obtain clean water vapor from sewage. However, the soluble contaminants remaining in the original solution were not removed, and the floating organic pollutants affect the steam production rate. In this paper, the superhydrophobic Bi/BiOCl with low surface tension is synthesized and loaded to the felt to construct the floating layer of the photothermal device. The floating layer collaborated with the filter paper hydrophilic layer and the Pyromellitic dianhydride-Tris (4-aminophenyl) amine covalent organic framework (PMDA-TAPA COF) photothermal layer to treat the sewage containing dissolved pollutants, achieving an interfacial evaporation rate of 1.47 kg⋅m−2⋅h−1. Importantly, the floating layer not only has a contact angle of 161°, which can selectively adsorb the organic solvents floating on the water surface, but also can degrade the pollutants dissolved in the water under the light and solving the problems that hinder device applications. The valence band and conduction band potentials of superhydrophobic Bi/BiOCl are at 3.065 eV and −0.435 eV, respectively, which produce h+ and O2– under light to degrade dissolved pollutants in water. The introduction of novel superhydrophobic Bi/BiOCl photocatalyst in the floating layer provides a reference for solving the problem of pollutant residues.

Environmentally friendly utilization of LNG regasification process and geothermal-based dual-loop power cycle for desalinated water and hydrogen production

The global scarcity of fresh water has prompted the development of innovative strategies for establishing affordable and efficient desalination systems that utilize waste heat from industrial processes. This study presents a novel combination of a geothermal-driven dual-loop organic Rankine cycle and liquefied natural gas (LNG) regasification process intended for electricity, desalinated water, and hydrogen production. The integration of diverse energy sources holds the capability to reduce dependence on traditional fossil fuels and promote a more sustainable and diversified energy portfolio, conducive to ecological well-being. In the suggested approach, a thermoelectric generator (TEG) is employed to harness the thermal contrast present between the residual heat of the geothermal process and the cold LNG stream, which reduces irreversibility and increases the system's power output. After examining the effect of key parameters on the system's performance, a data-driven approach is adopted in which the system's performance is predicted based on artificial neural networks (ANNs). According to the results, the primary generated power, desalinated water production rate, total cost rate, and cooling load are 5.15 MW, 127.31 m3/h, 188.22 $/h, and 2.92 MW, respectively. Also, the findings of the financial investigation demonstrate that the electrolysis unit, with an hourly cost rate of 85.2 $, constitutes more than 45 % of the total cost rate. In addition, the optimization of the system is performed in three distinct cases, wherein each case pertains to a different objective. In optimal conditions, the amount of produced desalinated water and the total cost rate are 153.89 m3/h and 153.58 $/h, respectively.

Chlorine resistant polyamide desalination membrane prepared via organic-organic interfacial polymerization

Desalination of seawater, brackish water and urban sewage is an important way to solve the global water shortage. Polyamide (PA) membranes, including reverse osmosis (RO) membrane and nanofiltration (NF) membrane, are the primary technology for seawater desalination and clean water production. However, traditional thin-film composite PA (TFC-PA) membranes prepared from interfacial polymerization (IP) of amine monomers (either piperazine or m-phenylenediamine) in water and acyl chloride monomers in organic solvent are incapable of tolerating strong acid and chlorine environment. Here, we develop a new IP process, which takes place at the immiscible interface between dimethylacetamide (DMAc) and hexane (referred to as organic/organic IP), to prepare both chlorine-resistant and acid-resistant TFC-PA membranes. Compared to conventional water/oil IP process, the organic/organic IP process can adapt more kinds of amine monomers rather than just PIP, such as tetra (4-aminophenyl) methane (TMAP), tris (4-aminophenyl) amine (TAPA), and 4,4′,4''-(1,3,5-triazine-2,4,6-triyl) triphenylamine (TTA), which we studied in this work, thereby extending the PA molecular structure and enabling the membranes with greatly improved chemical stability. Among them, the TAPM-based TFC-PA membrane exhibits a NaCl rejection of 95.9% and no obvious NaCl rejection deterioration after soaking in a high concentration of NaClO (1000 ppm, pH 7) for more than 30 h, indicating excellent chlorine resistance. The TTA-based TFC-PA membrane shows a Na2SO4 rejection of 97% and remains unchanged after being exposed to a wide pH scan of 2–12. The Organic/organic IP provides a new and easy-to-operate platform for designing chlorine and acid resistant TFC-PA membranes, which will greatly improve their environmental stability as the most advanced desalination membrane at present.

Experimental investigation and performance evaluation of an oval tubular solar still with phase change material

The problem of freshwater scarcity is a major issue for people all over the world. Solar still is one of the most simplest and affordable ways to produce freshwater using solar energy which is available with no cost and eco-friendly. Recently, tubular solar stills (TSS) have gained popularity as one of the best solutions for acquiring pure water, especially in arid and coastal areas. The main objective of this paper is to enhance the productivity and efficiency of TSS by introducing a new form/shape, the oval tubular solar still (OTSS), integrated with cover cooling and phase change material (PCM). The OTSS is made of a transparent oval tube that is permeable to sunlight from all directions to maximize solar irradiance, and it is integrated with a black basin to improve absorption and water evaporation. It has an appropriate level of flexibility, durability, and low cost. Experiments were conducted out in the climatic conditions of Cairo, Egypt. This paper investigated different basin water depths and different water cover cooling flow rates to obtain their optimal values. Moreover, the effects of using PCM as a thermal management solution were studied in detail. In the case of no cooling, it is observed that the production rate decreases with increasing the water depth in the basin and the maximum production rate reached up to 5.21 L/m2/day at the optimal water depth of 0.5 cm. However, with cooling, the maximum production rate of 6.34 L/m2/day was achieved at the optimum water-cooling flow rate of 2 L/h. Using the PCM the maximum production rate of 6.78 L/m2/day was able to be achieved. The efficiency and productivity of the OTSS were enhanced by 41.26 % and 32.42 %, respectively, when using PCM. Furthermore, the daily thermal exergy efficiency of the OTSS was 3.46 %, 3.85 %, and 4.14 % for the cases no cooling, with cooling and with PCM, respectively. Economically, the cost per liter of desalinated water production was $0.020, $0.017, and $0.017 for the three cases, respectively.

Dual-objective optimization of biofuel-based solid oxide fuel cell energy system for hydrogen fuel and desalinated water production

In this research study, the combination of both mentioned solutions and their effects on the efficiency of the system, its environmental concerns, operation cost, and maintenance cost are explored. The intended purpose of the current study was to propose a regenerative cycle that implements multiple sub-cycles to enhance the first and second-law efficiencies of the system and reduce the cost rates. The aforementioned system consists of a gas turbine (Brayton) cycle, a steam turbine (Rankine Cycle), an ORC, a single-effect Li-Br absorption chiller, a reverse osmosis desalination unit, a SOFC, and thermoelectric generators to obtain higher efficiency and electricity, even from the system low-grade waste heat. The dual-objective optimization considering the minimum cost rate and maximum exergy efficiency of the system is proposed. To achieve this goal, a genetic algorithm is implemented for better optimization and the Pareto frontier is represented along with a scatter of distribution plots to determine the optimum outputs of the function and their respective values for the decision variables. The optimization using design parameters lead to the best point with the exergy efficiency of 61.3% and cost rate of 0.27$/s for an interest rate of 12%. Although the environmental aspects are not included in the optimization, the design of the system is tried to be as environmental-friendly as it can be. The decision variables were the most crucial ones that affect the system the most. Isentropic efficiencies of pumps, compressors, and turbines along with the fuel mass flow rate, and pressure ratio in pumps and compressors are considered decision variables. The other decision variable which plays an undeniable role in the efficiency of the system is the temperature difference between the inlet and outlet of the Rankine Cycle HRSG. In the end, the optimizations were repeated for four different interest rates. The projected results illustrated the negative effect of increasing interest rates on both the exergy efficiency and cost rate of the system.

A novel water freezing desalination plant integrated into a combined gas power cycle plant

In this work, a freezing desalination unit is integrated into a conventional combined power plant to improve the plant performance and produce desalinated water. A mathematical model is developed to simulate the modified cycle. The effect of compressor inlet air temperature on thermal performance, desalinated water production capacity and specific fuel consumption is examined. Results of the modified cycle were compared to that of the conventional cycle. The results show that the proposed system is capable of producing up to 2.74 million m3of desalinated water annually from a brackish water source (TDS of 2000 mg/l) with an increase in the Energy Utilization Efficiency (EUE) by 15% as compared to the designed value under ISO standard conditions. Furthermore, operation cost for fresh water production is also examined, results show that the fuel cost of 1 m3 of desalinated water varies between (0.56–0.58) $/m3 compared with 0.66 $/m3 and 0.93 $/m3 for desalination technologies of R. O and MED, respectively.