Freshwater Production Research Articles

Thermal-driven osmosis utilizing hollow fiber membranes: Sustainable dye water treatment and electricity extraction

Excessive discharges of chemical dyes have led to severe contamination of seawater, resulting in significant ecological damage. Thermo-osmotic energy conversion technology, which purifies wastewater and generates electricity under temperature gradients, has garnered considerable interest from researchers. However, the operational efficiency of thermo-osmotic energy conversion is inherently limited by the effective membrane area, and conventional systems typically employ flat membranes as separators, resulting in suboptimal performance for the same floorage. In this study, we introduce a novel system that combines thermo-osmotic energy conversion technology with hollow fiber membranes that possess a high effective membrane area, thereby achieving optimized performance. Driven by the temperature gradient, the water in the dye solution condenses outside the membrane and converted from vapor to liquid. The continuous accumulation of condensed water generates pressure and drives a water turbine for sustainable power generation. Our results demonstrate that at temperature gradient of 40 °C, the system can achieve the power output of 16.75 Wm−3 and the freshwater production rate of 70.29 kg m−3 h−1 under ideal conditions. This study presents a novel water-electricity co-production system based on low-grade waste heat recovery for dye solution treatment, which extends the applicability of thermo-osmotic energy conversion technology and improves its practicality.

Ion-engineered solar desalination: Enhancing salt resistance and activated water yield

Solar desalination, which relies on localized heating for interfacial water evaporation, is regarded as a promising and sustainable approach for freshwater production. Significant progress has been achieved in developing high-performance solar-driven interfacial vapor generators (SIVGs), however, their performance in high-concentration brine remains unsatisfactory. Herein, a novel SIVG is proposed as a candidate with advanced ionization engineering design for solar desalination, which exhibits enhanced desalination performance. The design of ionization engineering can promote salt-blocking effects through electrostatic attraction between salt ions in seawater and polymer chains of hydrogel-based evaporator, and high-continuity porous structures, which also contributes to a high evaporation performance by increasing the production of activated water molecules. Furthermore, the introduction of CuO nanoparticles with excellent localized surface plasmon resonance effect enables the light-absorbing copper-based hydrogel (LACH) to achieve an impressive sunlight absorptance rate of 95 %. The evaporation rate and energy efficiency of LACH reach a remarkable 3.93 kg·m−2·h−1 and 93.5 % in simulated brine (3.5 wt% NaCl solution) under one-sun illumination. The salt-resistant LACH-related SIVG is one of ideal candidates for sustainable freshwater harvesting over extended periods. This study is expected to offer valuable insights for advancing the research and development of next-generation solar desalination devices.

Ultrahigh freshwater production achieved by unidirectional heat transfer interfacial evaporation solar still integrated with waste heat recovery

Solar-driven interfacial evaporation technology exhibits notable performance in evaporation, with evaporation efficiency typically maintained at over 80 %. However, utilizing interfacial evaporation for efficient seawater desalination remains a challenge due to low production of freshwater. Therefore, we propose a desalination system based on unidirectional heat transfer solar still, which is capable of combining efficient evaporation with waste heat recovery to achieve high energy utilization. The design of the solar still decomposes the light transmission and condensation functions of the glass cover plate in traditional solar still for independent optimization and reserves space for integrating high-performance interfacial evaporation materials, while minimizing heat loss by ensuring unidirectional heat transfer inside the still. In particular, the proposed unidirectional heat transfer solar still provides a free interface to condense the vapor, where a multi-stage condensation is integrated to recycle latent heat. When using a self-made hydrogel sponge as the interfacial evaporation material, the solar still achieve efficient and stable freshwater production. Outdoor experiments showcase a evaporation rate of 6.0 kg·m−2·h−1, coupled with an freshwater production rate of 4.5 kg·m−2·h−1 under an average sunlight intensity of 1.07 kW·m−2. Our results demonstrate that the freshwater production of the solar still can be further improved. This work is beneficial for further enhancing freshwater collection of solar desalination.

Multi-period reverse logistics network design for water resource management in hydraulic fracturing

This paper addresses the effective management of water resources during the hydraulic fracturing process used for natural gas extraction. With increasing demand and scrutiny on shale gas production due to economic, environmental, and social factors, effective water management strategies are needed to address the challenges of flow-back water usage during hydraulic fracturing. This research contributes to the existing literature from a multi-period reverse logistics network design perspective with realistic modeling approaches. A mathematical formulation is developed for optimizing the design of a multi-period reverse logistics network for effective water resource management that incorporates production scheduling of a hydraulic fracturing process. This mixed integer programming model determines the optimal locations and capacities of impoundments, treatment facilities, and disposal sites while minimizing fixed and operational costs under constraints such as freshwater withdrawal limits, production schedules, inventory balance, and treatment and disposal options. A two-stage stochastic programming formulation is further developed as a means to address the uncertainty associated with water flows during the fracturing operation. The strategic location and capacity decisions are given in the first stage of this formulation, whereas operational decisions such as water flows are handled in the second stage under independently sampled scenarios. A sample average approximation algorithm is proposed to solve the stochastic formulation. The model is tested on a case study from the United States that explores potential impacts on water resource management due to cost variations, changes in operational parameters, and uncertainty in demands and supplies. The base case setup delivers a 12.8% reduction in freshwater usage. The benefit of multi-period reverse logistics network design is further demonstrated through variations in water demand and equipment degradation. The managerial insights derived through sensitivity analysis highlight the values of the proposed multi-period formulation, capacity expansions, and parameter estimations.

An Experimental Investigation of an Open-Source and Low-Cost Control System for Renewable-Energy-Powered Reverse Osmosis Desalination

Considering the degradation of water resources and the increase in human population, desalination seems to be a promising method for meeting the global water demand, from potable water to plant irrigation needs. The contribution of desalination to the agricultural sector, through the supply of water for plants or animals, is critical because this sector represents 70% of the global water demand. Unfortunately, the desalination process is energy-intensive and subjected to several factors that result in undesirable fluctuations on quality/quantity of product water, and/or energy waste. Renewable energy sources can supply the necessary power, but they amplify these challenges because their availability varies over time. A simple and efficient way to tackle this issue is to control the pressure of the feed water before feeding it to the membrane. Typically, the pairing control systems are quite expensive or lack the necessary customization freedom that could improve their operation. Therefore, this study highlights the feasibility of enhancing a typical desalination control equipment via the incorporation of modern low-cost microcontrollers and flexible open-source software; the potential of these tools has not yet been fully explored. The microcontroller executes customized PID logic, driving an industrial inverter module. Our results indicate that the proposed system can keep pace with the desalination process setpoints, reducing the stress of the electromechanical components and periods of out-of-specification freshwater production. This low-level control function implementation minimizes the need for human intervention while providing a promising foundation for further extensions and customizations in this area.

Production of power and fresh water using renewable energy with thermal energy storage based on fire hawk optimization

This manuscript proposes an optimization method for power production and fresh-water using renewable sources with thermal energy storage (TES). The proposed method is the fire hawk optimization (FHO) method. The objective of the proposed method is to find better thermal efficiency. The waste heat in the steam power plant is converted to fresh water using the multi-effect desalination method. The cost of freshwater strongly depends on solar-electricity cost and displays a significant variation because of the variable solar availability state. The integrated structure using thermodynamics is examined by Exergy analysis. Heat exchangers and collectors are related to the energy efficiency of the total integrated structure and the equipment’s highest share of energy destruction. The FHO method is implemented in MATLAB and its execution is calculated with existing approaches. The thermal efficiency in solar collectors is 80% and it is better than existing methods.

Simultaneous solar steam and electricity generation from biochar based photothermal membranes

Clean water and energy are essential for reducing poverty, fostering economic growth and sustainable development while mitigating CO2 emissions. Considering that, solar-powered interfacial vapor or steam generation is sustainable and promising environmental technology for both water purification and energy generation while being CO2-free. Despite continuous research progress, most of the solar absorbers to capture sunlight following heat conversion for steam generation are generally made from expensive nanostructures, which in part prevents their widespread manufacturing for useful applications. Herein, we experimentally demonstrate a biomass-derived carbon composite membrane that nearly covers the entire sunlight spectrum as a solar absorber with an estimated absorptivity of 90%. As a result, the light absorbed yields a surface temperature of 55 °C at the surface of the B700 and 33 °C for water. Evaporation rates up to 1.26 and 1.16 kg/(m2 h) and solar-to-vapor efficiencies of 80 and 74% were recorded in presence of sodium chloride with two different types of biochar B700 and B300 based photothermal membranes, respectively, under 1 sun illumination. The water evaporation in presence of mixed sodium chloride/magnesium chloride reached up to 1.21 and 1.05 kg/(m2 h) with 77 and 69% efficiency with B700 and B300; due to different solar absorber geometry. Furthermore, by merging the thermoelectric technology, we exploit the concept of hybrid clean water and energy generation. At a relative humidity of 60%, the thermoelectric device may generate approximately 0.9 W/m2 power density. These results highlight the interactive effects of biochar and polyvinylidene fluoride with porous hierarchies and enhanced absorption of sunlight, thus enabling a considerable elevation of temperature with great potential for clean water and energy. Overall biochar photothermal membrane represents a significant advancement as low-cost sustainable technology, addressing both water and energy challenges by providing efficient, environmentally friendly solution for freshwater production and clean power generation.

Spatial Patterned Interfacial Solar Evaporators toward Recovering Heat Loss.

The novel freshwater production technology, such as interface solar-steam conversion (ISSC) technology, has advanced so rapidly recently, where its energy capture and conversion process was localized at the air-water interface so as to achieve high efficiency of energy utilization and transformation. However, when enlarging the evaporation surface and application scale, the inevitably increased heat loss and reduced conversion efficiency put it in a dilemma: should we exploit innovative steamer constructs for practical applications. In order to effectively mitigate heat loss from the evaporator to the surrounding environment, a series of spatial pattern evaporators (SPEs) are specifically designed in this article. By recovering the energy of radiation and convection heat loss, SPEs achieved low heat loss in an open evaporator through unequal height auxiliary heat exchange platforms. In an open environment, it achieves a maximum evaporation rate of 1.68 kg m-2 h-1, with approximately 52.41% of the heat loss being reabsorbed. This sophisticated pattern design provides a promising guideline for optimizing thermal management strategies and promoting practically scalable applications.

Highly efficient portable atmospheric water harvester with integrated structure design for high yield water production

Sorption-based atmospheric water harvesting (SAWH) as an appealing way to address global water shortage can obtain water from air anytime and anywhere. However, achieving liter-scale water yield by portable device for daily demand is still a challenge. Here, a 7.5-L portable atmospheric water harvester with optimized structure design was proposed. By adopting central heating and radiation heat shielding strategy to minimize heat losses during desorption process and utilizing a batch-process operation model, the device presented superior productivity of 1150 gwater/day with low energy consumption of 1.7 kWh/L under field test. This is the first demonstration to promote daily water yield of small-size SAWH device to an order of 1000 g with lower energy consumption compared with existing active SAWH studies. Optimized heat and mass transfer within compact structure enabled the water yield per unit volume and weight of the device reaching milestone values of 152.5 gwater/Ldevice/day and 199.4 gwater/kgdevice/day. This remarkable performance motivated the feasibility of distributed freshwater production and pushed SAWH technology one step closer to the practical applications.

Facile preparation of anatase coated nanofiber mats for multifaceted water treatment

Access to and availability of freshwater is increasingly important as the World’s population grows and pollution threatens freshwater resources providing an underlying impetus to explore efficient and environmentally friendly water treatment technologies targeting seawater, industrial wastewater and domestic sewage. By embedding SiO2 in blow spun polyacrylonitrile (PAN) fibers that after peroxidation form a flexible nonwoven mat (SiO2@PNMs) and subsequent carbonization of the PAN and hydrolysis of TiO2 onto the SiO2 nanoparticles (TiO2/SiO2@CNMs), a multifunctional solar evaporator within the fields of photothermal conversion, catalytic degradation, desalination and disinfection is obtained. The sunlight light absorption is above 90 % and due to disruption of inter-water hydrogen bonds and the ability to evaporate through the sides of the nonwoven mat, the evaporation rate of 1.71 kg m-2h−1 exceeds the theoretically considered maximum at an energy conversion efficiency of 92.1 %. The evaporation rate remains stable through a 40-day cycle and the evaporation rate is unaffected by addition of NaCl in concentrations up to 20 % due to salt diffusion and pumping through the porous nonwoven structure demonstrating. anti-salt, anti-fouling and self-cleaning ability. In addition to the solar-driven water evaporation process, the photocatalytic properties of the anatase TiO2 crystals combined with the conducting effect of the carbon fibers trap photogenerated electrons and retard electron-hole complexation to maintain the release of reactive oxygen species to decompose organic dyes and inactivate bacteria in the water source. This multifunctional nanofiber mats provide a simple and sustainable avenue for the production of fresh water, and has potential application in desalination of seawater and purification of printing and dyeing wastewater.

Tri-objective optimization of electricity, fresh water, and hydrogen production in a biomass-driven trigeneration plant: Thermoeconomic and environmental evaluation

Substituting renewable energy sources for fossil fuels is a viable option for mitigating environmental damage caused by the energy sector. Another strategy for better utilization of primary resources is integrating multigeneration energy plants. To that end, this study proposes the construction of a biomass-fired power, water, and hydrogen facility. A gasifier integrated gas turbine (for electricity generation), vanadium-chlorine thermochemical cycle (for hydrogen synthesis), and MED-TVC unit (for water desalination) make up this system. Compared to previous similar researches, the waste heat-driven hydrogen and freshwater production units is the most favorable feature of the proposed tri-generation plant in this research. Exergy, economic, and ecological impacts of the engineered plant are examined. The results of a thorough parametric analysis reveal that, each design variable uniquely impacts the values of three goods and three performance indicators (exergy efficiency, emission index, and levelized cost of product). Therefore, the proposed tri-generation plant's optimal operating conditions can only be determined by the use of a triple-criteria optimization. The best operation was found to have a levelized product cost of 0.0441 $/kWh, a CO2 emission of 0.530 kg/kWh, and an exergy efficiency of 56.64%. The parametric analysis also suggested that a lower pressure ratio and gasification temperature would be optimal for increasing hydrogen production.

Innovative use of air gap membrane distillation to harvest waste heat from alkaline fuel cell for efficient freshwater production: A comprehensive 4E study

Poor power density of alkaline fuel cell (AFC) resulting from inherent waste heat generation significantly hinders its widespread application. Herein, an innovative hybrid system that combines AFC and air gap membrane distillation is proposed, aiming to enhance the power density via utilizing the waste heat for freshwater generation. Based on the laws of thermodynamics and electrochemical theory, the hybrid system model is formulated to derive performance metrics by quantifying various irreversible losses. The thermodynamic performance, competitiveness, economic viability, and environmental impact of the system are comprehensively discussed through energetic, exergetic, economic, environmental (4E) analyses. Calculations predict that the maximum equivalent output power density permits 63.28% higher than that of the standalone AFC at 353 K. The influencing mechanisms of the AFC operation conditions, air gap thickness, and properties of the porous hydrophobic membrane are clarified to discern potential avenues for further performance improvement. Furthermore, a multi-objective local sensitivity analysis indicates that membrane porosity and coolant solution temperature are the most sensitive factors. The levelized costs study reveals that water and electricity costs over the total lifecycle are 56.89 $m−3 and 0.1012 $kWh−1, respectively. The multi-objective optimization further provides a high-performance and cost-effective design solution for the hybrid system.

Zero energy building optimization for a residential complex with a new optimized cogeneration system for electricity, cooling, heating and freshwater production

In this research, a multi-generation system was proposed to meet the energy consumption of a 120-unit zero-energy residential complex with 100 m2 and 2 bedrooms in Sydney, Australia. To meet the heating and cooling demand of the residential complex, a compression chiller was used, and electrical energy was provided using the system's production power. The main goal of this research is to define a zero-energy building by providing the energy consumption of a residential complex with a solar system. Building Energy Optimization (BEopt) Software has been used for the process of simulating the residential complex and extracting the required load of the residential complex. The design of the load supply system of the residential complex was done using EES thermodynamic software. In this research, a large number of inputs have been used in different scenarios to optimize the residential complex, and the tool used in this research by all the modes introduced as inputs turns the problem into a multi-objective optimization problem. The results of the investigation of the residential complex showed that the amount of electricity consumption, heating, and cooling of the residential complex during the year is 36728, 133123, and 17,902 kWh, respectively. Also, by optimizing the energy consumption of the residential complex, it is possible to reduce CO2 emissions and prevent the increase in environmental pollution. The optimal results showed that the system in its most optimal state can reach an exergy efficiency of 25.18 % and a system cost rate of 46.6 $/h. The performance of the system in the city of Sydney showed that the system can produce 166,164 kWh of electricity, 467,945 kWh of heating, and 183,370 kWh of cooling in one year. Comparing the results of residential complex consumption load and system production showed that the proposed system can easily provide the residential complex consumption load throughout the year.

Development of a vacuum double-slope solar still for enhanced freshwater productivity

In this study, a solar-energy-driven high performance water purification system is designed, fabricated, and examined, which may be useful for remote areas with limited access to grid electricity and underground freshwater. This research aims to enhance the performance of a conventional solar still (double-slope type) by creating vacuum inside the chamber and using paraffin wax (PCM) as energy storage material. The performance of the modified solar still (SS) is investigated and compared with the conventional solar still (CSS) in terms of productivity, distillation efficiency, and exergy efficiency. The performance analyses show that the hourly productivity and daily cumulative productivity are increased by 22.33 % and 63 % (from 5.46 L/m2 to 7.03 L/m2) respectively for the modified still compared to the conventional still. Nearly 28.72 % distillation efficiency and 22.43 % exergy efficiency enhancement are recorded for the modified system compared to the conventional system. This study also reveals that the thermal performance of the modified system is significantly improved under vacuum condition and using paraffin wax as heat storage material, which enables the still to operate at low solar intensities. The economic analysis shows that the cost of freshwater produced per liter in the modified SS is 41.4 % less than that of the conventional SS.

Cost-Effective 3D-Printed Bionic Hydrogel Evaporator for Stable Solar Desalination.

Solar desalination using hydrogel evaporators is an eco-friendly, highly efficient means with natural sunlight for sustainable freshwater production. However, it remains challenging to develop a cost-effective and scalable method to prepare salt-resistant hydrogel evaporators for stable desalination. Here, inspired by tree transpiration and hierarchical porous structure, a 3D-printed bionic hydrogel evaporator (3DP-BHE) is designed for long-term solar desalination. Commercialized activated carbon (AC) is introduced into biomass starch skeleton as a solar light absorber to build 3DP-BHE in a cost-effective fashion ($10.14m-2 of total materials cost). The bionic tree leaf layer for 94.01% light absorption and timely vapor diffusion. The bionic tree trunk layer with 3D printed bimodal porous structure for water transfer, thermal isolation, and salt ions convection and diffusion. With the unique bionic structure, the 3DP-BHE achieves a stable evaporation rate of 2.13kgm-2h-1 at ≈90.5% energy efficiency under one sun (1kWm-2). During the 7-day desalination of 10wt.% brine, a steady evaporation rate of 1.98kgm-2h-1 is maintained with a record-high cost-effectiveness (195.3gh-1$-1) manner. This 3DP-BHE will open significant opportunities for affordable solar desalination systems on multiple scales, from individual households to off-grid communities.

Sustainable freshwater production using novel cascade solar still with phase change material, serpentine water path, and copper fins.

Heat losses in solar stills are high, which has led to a decrease in their thermal efficiency. Also, the production of these devices is limited to the presence of the sun, and their production stops during cloudy hours or at night. To solve these problems, in this experimental study, two cascade solar stills are examined under relatively similar conditions for sustainable freshwater production. One of these solar stills is modified with the phase change material and copper fins, and another one is a conventional cascade solar still without using the phase change material and copper fins. Paraffin was selected as a heat storage material to increase the time of desalination of water by the solar still. In addition, the copper fins are used to increase the conduction heat transfer in phase change material and provide better melting and solidification processes. To prolong the water path along the steps, the serpentine water path was considered. The results showed that at sunset hours, desalination efficiency with phase changing material and fins was increased. At 5 pm, the efficiency of the modified device was increased by 29% (on average) as compared to the conventional solar still without using phase changing material and fins. The rate of water production in conventional solar still in midday was higher compared to the modified solar still. However, in the sunset and night hours, the modified solar still has a higher production rate due to heat released from the thermal storage system.

Modeling and simulation of direct contact membrane distillation system integrated with a photovoltaic thermal for electricity and freshwater production

Energy drives the growth, transformation, and economic development of every nation. The vitality of human existence and progress hinges on the accessibility of both energy and water resources. As freshwater resources are diminishing, therefore, desalination needs have increased. In solar membrane distillation systems, the key challenge is maintaining the intake water temperature in the membrane distillation system with fluctuating solar radiation intensity which affects the distillate water quantity and quality. The objective of this study is to enhance and optimize a mathematical model for analyzing a cutting-edge solar-integrated PV/T-DCMD system. In this innovative integration, the direct contact membrane distillation intake water temperature is derived from the photovoltaic thermal output. The integration of direct contact membrane distillation with photovoltaic thermal systems represents a cost-effective and technologically advantageous concept. As the water temperature increases, there is a notable improvement in the evaporation efficiency of PV/T-DCMD systems, with an increase from 35.08% to 42.01%. Additionally, there is a reduction in specific thermal energy consumption, decreasing from 1,192 to 1,386 kWh/m3 as a consequence of the elevated feed water temperature.

Bird's Nest-Shaped Sb2 WO6 /D-Fru Composite for Multi-Stage Evaporator and Tandem Solar Light-Heat-Electricity Generators.

Herein, an integrated solar-thermal-power protocol is presented at a micro-nanoscopic level to maximize the energy utilization efficiency involving utilization period and utilization patterns, and the nexus of freshwater production and nanogeneration is realized. This sophisticated vaporization device is constructed with the merits of thermally confined evaporation space in favor of recycling latent heat of condensation and optimizing light absorption based on the local sunlight angle of incidence. Inspired by a bird's nest, Sb2 WO6 /D-Fructose composites are prepared as photothermal absorbers to achieve a superior water evaporation rate of 2.78kgm-2 h-1 in the Multi-stage evaporator. In addition, a synergistic tandem photo thermal-electric device with a combination of solar-driven water evaporation and further waterflow-driven hydrovoltaic generation, which can output a stable voltage of up to 360.8mV with effective utilization of steam energy and a limited water source, is exploited. Such integrated configurations pave a pathway for clean water production and renewable power generation simultaneously toward energy issues.

Salt resistant and self‐cleaning CNTs‐SEBS‐MAH composite membrane for seawater desalination

AbstractSolar‐driven steam generation membranes have garnered increasing attention for freshwater production. Nonetheless, the adverse impact of salt accumulation on membrane surfaces directly undermines the efficacy of solar evaporation. In this work, one type of composite membrane comprised of carbon nanotubes (CNTs)‐styrene‐ethylene‐butadiene‐styrene (SEBS) was fabricated by modified vapor phase pore‐forming technique. Through the grafting of maleic anhydride (MAH), the CNTs‐SEBS‐MAH composite membrane was successfully hydrolyzed. As a consequence, the composite membrane exhibits evaporation rate as high as 1.28 kg m−2 h−1 under one sun solar irradiation, accompanied by an outstanding solar vapor conversion efficiency of 87.5%. In addition, the fabricated composite membrane has high resistance to salt accumulation, as well as self‐cleaning capability. This work provides a route for manufacturing hydrophilic polymer composite membrane towards solar energy driven seawater desalination.

Performance analysis of hemispherical distiller for different basin materials with mirrors and energy storage material

ABSTRACT A multitude of studies exist on solar desalination systems, particularly focusing on innovative designs for covers and absorber materials to enhance freshwater production. Given the larger exposure area for evaporation and condensation, hemispherical solar stills have become widely utilized. This study primarily centers on improving freshwater yield by incorporating reflective mirrors and absorber materials made of zinc and copper into the hemispherical solar still. The thermal performance is evaluated and compared with a hemispherical solar still lacking these modifications. In addition, sand grains are introduced to the absorber as a means of energy storage. Experimental results demonstrate that the concurrent use of copper as a basin material with reflective mirrors and sand grains as energy storage significantly enhances freshwater production from the hemispherical solar still. The findings reveal an improvement in freshwater yield by up to 156% compared to a conventional hemispherical still. The conventional and modified hemispherical solar stills, with the combined effects of energy storage through sand grains, absorber plate, and reflective mirrors, exhibit a maximum accumulated yield of approximately 4.65 and 11.9 L/m2, respectively. The present findings affirm the importance of the proposed modifications to the hemispherical solar still.