Energy Desalination Research Articles

Novel synergetic integration of supercritical carbon dioxide Brayton cycle and adsorption desalination

High ambient conditions and high energy desalination technologies could penalize power cycle performance and this synergistic integration is proposed as a solution to address this challenge. A novel integration of closed loop recuperative supercritical carbon dioxide Brayton cycle with low temperature adsorption desalination cycle is investigated. Brayton cycle provides the heat source for the adsorption desalination cycle and the latter provides the cooling required for heat rejection in Brayton cycle. The integrated system is modeled and the performance is analyzed through energy, exergy analysis, and parametric studies. Finally, the integrated system performance is compared against a stand-alone cycle and literature for performance gains. A maximum improvement of about 9.1%, 21.1%, and 10.7% for energy efficiency, exergy efficiency, and overall system effectiveness were observed for the lowest chilled water temperature of 25 °C over typical ambient conditions of 35 °C. Maximum specific daily water production and specific cooling output at these conditions were 11.3 kg of water kg of SG and 195 W kg of SG , an improvement of about 26% and 28% over typical ambient conditions. Finally, overall system effectiveness improvement of about 14.3% over a stand-alone system is achieved, compared to a maximum of 10% improvement for supercritical carbon dioxide and multi-effect desalination integrations. Better performance improvement achieved at lower turbine inlet temperatures compared to multi-effect systems warrant the advantage of synergetic integration of power cycles like the supercritical carbon dioxide Brayton cycle with less energy-intensive adsorption desalination. • Novel synergetic integration of supercritical Brayton and adsorption desalination cycle. • Energy, exergy, parametric study, and performance compared with similar systems. • Improvement of 10.7% in overall system effectiveness over tropical conditions. • Increase of 14.3% in overall system effectiveness over stand-alone Brayton cycle. • Better performance at lower turbine inlet temperatures than multi-effect integrations.

Facile Preparation of Cu2S/Cu Mesh For High‐performance Solar Water Evaporation

AbstractSolar vapor generation has attracted tremendous attention as one of the most efficient ways of utilizing solar energy. Compared with bulk heating, interfacial solar steam generation efficiency is high, and the heat loss to the surrounding environment is minimal, which is an eco‐friendly and energy‐efficient way of harvesting solar energy for desalination and wastewater treatment. So it is highly desirable to develop low‐cost and high‐efficiency solar absorbers for practical applications of interfacial solar steam generation. In this work, Cu2S/Cu mesh was prepared by depositing Cu2S nanoparticles on copper mesh by one‐step hydrothermal method, which was used as photothermal conversion material for solar interfacial evaporation. This material owns a high solar absorptivity of 84.01 % within the wavelength range of 0.25–2.5 μm. Under one sun illumination, the evaporation rate is 1.55 kg m−2 h−1 and the solar thermal conversion efficiency reaches 96.9 %. The cycle stability tests showed that the evaporation rate decreased firstly and then was balanced at 1.34 kg m−2 h−1 in 10 cycles. Furthermore, this material can maintain a stable performance of interfacial solar steam generation during desalination of seawater and purification of dye wastewater containing Rhodamine B and Methyl Orange, respectively. This work provides a low‐cost, simple, and efficient preparation method for synthesizing an efficient Cu2S/Cu mesh solar steam evaporation material.

Optimization of a solar-wind- grid powered desalination system in Saudi Arabia

The utilization of renewable energy to run desalination plants has enormously expanded in the last two decades. In this study, a grid-connected hybrid solar-wind system is proposed to power a small-scale Reverse Osmosis (RO) desalination unit. In a case study, the system's performance has been analyzed under the weather conditions of the Eastern Province, Saudi Arabia. A numerical model has been developed based on a mixed-integer linear programming (MILP) approach to design and size the proposed system. The developed model is solved on an hourly basis to capture hourly variations of weather conditions with the aim to obtain an efficient design to operate the RO plant and supply freshwater to a small community living in a remote area at minimum cost. The developed model allows finding the optimal number of wind turbines, the number of photovoltaic (PV) modules, and the energy purchased from the national grid. Since the desalination energy consumption depends on the feed water conditions, two energy consumption rates are considered, namely, 2 and 4 kWh/m 3 . The results show that brackish water can be purified for the two different energy requirements at a cost varying between 1.72 and 1.84 $/m 3 , respectively.

Nanomaterials-based air-cathodes use in microbial desalination cells for drinking water production: Synthesis, performance and release assessment

Global water desalination capacity is around 95 million m3 day−1, accounting for an enormous energy demand, thus low energy desalination technologies are needed. Microbial desalination cells (MDC), a bioelectrochemical reactor that allows water desalination while treating wastewater with low energy requirement represents a potential low energy solution. Air-cathode based MDC is a promising environmentally friendly reactor configuration as it reduces operational costs but has limited performance due to low cathode oxygen reduction reaction (ORR) kinetics. Air-cathodes with high ORR performance must be developed considering cost, performance and toxicologic characteristics. In the present work we developed two different carbon-based platinum free air-cathodes: iron doped carbon nanofibers (CNF-Fe) and gas diffusion electrodes based on MnO2 (MnO2-GDE). The air-cathodes demonstrated dissimilar ORR performances; CNF-Fe performed better at low overpotential while MnO2-GDE did better at high overpotentials. MDC reactors were tested employing both air-cathodes, achieving average output electrical current densities of 4.1 mA cm−2 and 1.3 mA cm−2 for MnO2-GDE and CNF-Fe, respectively. Also, the desalination performance of MDC employing MnO2-GDE was higher than CNF-Fe based MDC, reaching a salt removal rate of 4.8 g m−2 h−1 and 3.6 g m−2 h−1, respectively. Finally, the release of nanomaterials during both air-cathodes use in MDC operation was assessed, which represents the first study of this type to author’s knowledge. The results demonstrated some cathode catalyst release, but at a concentration below the threshold to represent a threat for the environment and humans.

Investigation of implementing solar energy for groundwater desalination in arid and dry regions: A case study

Desalination is a perfectly viable solution for alleviating the problem of water scarcity in arid and dry regions with access to seawater or brackish groundwater. Yazd province in central desert part of Iran suffers from drinking water for most of the cities, because of the low precipitation. This study aimed at prioritizing the capitals of counties for desalinating water for the first time for this area. Also selected criteria are being used for the first time which could be used for other regions in the world. Five existing water wells from each of nine counties are nominated and ranked. Technique for Order of Preference by Similarity to Ideal Solution method was used to rank counties in terms of suitability for desalination. Validity of the results is assessed by two different methods, which Marvast found as best location. The maximum capacity of the desalination equipment is 50 m 3 /h. The project in order to be economically feasible, equipment must operate at least 2 h a day, therefore it would be able to desalinate minimum of 100 cubic meters of water for total of 2 h. By implementing these methods, decision makers can rationally select and rank locations for construction of desalination plants. • Solar energy for groundwater desalination was investigated for Yazd, Iran. • Districts were investigated for prioritization. • TOPSIS method and Comfar software were used. • Marvast was selected as best location. • Economically, it must produce minimum 100 m 3 /day potable water.

Aquatech's AI partnership addresses desalination's energy consumption

Aquatech International is partnering with Pani Energy, a Canadian artificial intelligence (AI) analytics solution provider for water applications, to reduce the energy and cost associated with desalination.

Nanofibrous hydrogel-reduced graphene oxide membranes for effective solar-driven interfacial evaporation and desalination

• The photothermal membrane has excellent light absorbing ability. • The evaporator has a high evaporation rate and energy conversion efficiency. • The evaporator exhibits stable solar-driven desalination performance. • Water in the hybrid hydrogel membrane has a low vaporization enthalpy. • Intermediate water dominates the interfacial evaporation. Interfacial evaporation from light-absorbing, porous materials have offered an exciting opportunity to utilize sustainable renewable solar energy for desalination. However, the efforts to understand the fundamental mechanisms governing the interfacial evaporation have greatly lagged behind performance studies. Herein, a hybrid nanofibrous hydrogel-reduced graphene oxide (NHrG) membrane is demonstrated in this work. We experimentally characterized the state of water in the NHrG membrane and proved the presence of intermediate water in the porous membrane. By monitoring the vaporization enthalpy as a function of membrane saturation, we demonstrated that the vaporization of intermediate water dominates the interfacial evaporation process, thus playing a key role in lowering the vaporization enthalpy. The lowered enthalpy value together with other factors, such as the high light absorption efficiency enabled by reduced graphene oxide (rGO) and the porous hydrophilic network induced by electrospun hydrogel nanofibers, led to a highly efficient solar-driven interfacial evaporator. The NHrG membrane had an evaporation rate of up to 1.85 kg m −2 h −1 with a high energy conversion efficiency of 95.4% under one sun irradiation. In addition, the evaporator exhibited excellent desalination performance in treating fresh seawater and achieved high removal of salt as well as heavy metal ions. Our study provides important knowledge for performance optimization and process design.

Energy consumption of an electrodialyzer desalinating aqueous polymer solutions

When performing electrodialysis (ED) to desalinate a stream, both the energy for desalination and the energy for pumping contribute to the total energy consumption, although under typical working conditions (e.g., brackish water desalination) the latter is usually negligible. However, the energy penalty might increase when desalinating viscous mixtures (i.e., viscosity of 2–20 cP). In this work, we experimentally investigate the desalination performance of an ED-unit operating with highly viscous water-polymer mixtures. The contribution of desalination and pumping energy to the total energy consumption was measured while varying diverse parameters, i.e., salinity and viscosity of the feed, and geometry and thickness of the spacer. It was found that the type of spacer did not significantly influence the energy required for desalination. The pumping energy was higher than predicted, though in most cases minimal compared to the energy for desalination. Only when using thin spacers (300 μm) and/or highly viscous feeds (12 cP), the pumping energy accounted for 50% of the total energy for low salinity feeds. Therefore, the main contributor to the energy consumption of viscous solutions is the desalination energy, provided that large spacer thicknesses (at least 450 μm) and adequate operating conditions are utilized to limit pumping energy losses. • Electrodialysis of highly viscous fluids was experimentally investigated. • Effects of spacer thickness, fluid viscosity, salinity, and linear velocity considered • Increase in overall energy consumption only for high viscosity feeds + thin spacers

New Resins for Ion Exchange Applications and a Process for Their Sustainable Regeneration

The report is concerned with the design and synthesis of a mixed bead resin for high salt level desalination. The resin allows for the simultaneous exchange of both anions and cations, within the same polymer. This improves the efficiency of desalination at seawater levels. A novel process for sustainable and low energy desalination for brackish water has already been achieved via ion exchange resins as explained below. The advance in resin technology improves a novel membrane process with closed–cycle regeneration of the resin. It is a superior alternative to reverse osmosis.

Overview

It is an indisputable observation, beyond climate change: that the urgent development of simple new technologies, to ensure the supply of quality fresh water for cities and towns, industry and agriculture, presents an existential challenge for humanity.
 Several novel technologies that fill that need show that the job is not impossible. They are summarized in this volume. They are environmentally friendly and inexpensive.
 They include techniques for seawater desalination, wastewater sterilization –including viruses-, selective removal of heavy metals from industrial wastewater, efficient concentration of wastewater slimes to recycle water, and the prevention of water cavitation for much cheaper transport. Other new techniques like high temperature reactions achieved in low temperature water, and low energy desalination are in the wings. Borrowing from biology , new and edible class of surfactants is environmentally friendly, and can replace standard surfactants in present useage. The new technologies are cheap and scalable.

Mussel-inspired photothermal synergetic system for clean water production using full-spectrum solar energy

A simple manufacturing strategy of photothermal synergetic system for seawater desalination and sewage purification. • • A multi-scale rough structure was prepared by wet chemical etching and mussel chemistry inspiration. • • A low-cost and easy-to-manufacture photothermal synergetic system. • • Full-spectrum solar absorption and highly-efficient solar evaporation. • • The solar-driven purification of various sewage and the photocatalytic degradation of organic pollutants are realized. Facing the long-term shortage of global water resources, the use of solar energy for desalination and wastewater treatment has always been the focus of human exploration. Here, inspired by mussel-chemistry, we designed a functional photothermal-photocatalysis system based on Cu foam with abundant marigold-like CuO nanoflowers and Prussian blue (PB) nanoparticles. This superhydrophilic composite material (CuO@PDA/PB) has superior full-spectrum solar energy absorption (300–2500 nm), which achieved interfacial heating under solar radiation to generate stable water vapor. Besides, superhydrophobic CuO@PDA/PB with self-floating properties and Janus CuO@PDA/PB with asymmetric wettability and anti-turnover ability were prepared to systematically compare the effects of wettability on solar energy utilization. We conclude that the hydrophilicity of the sample and the strong capillary pumping effect are more conducive to water transmission, and the superhydrophilic CuO@PDA/PB has a higher evaporation rate (1.39 kg m –2 h −1 ) and efficiency (87.10%) than other samples under 1.0 sun. Importantly, the superhydrophilic CuO@PDA/PB with excellent salt-tolerance and antifouling property can also be used for the purification of the saline solution, oily wastewater and dyeing effluents via the solar-driven water evaporation. Moreover, CuO@PDA/PB possessed superior adsorption and photocatalytic degradation ability for the organic dyes in dyeing wastewater. Therefore, this solar-driven superwetting functional material provides an expandable and cost-effective platform for seawater desalination and sewage purification.

Integrated system based on solar chimney and wind energy for hybrid desalination via reverse osmosis and multi-stage flash with brine recovery

This paper studies the viability of utilizing an integrated system to yield electricity and freshwater, with solar chimney and wind energy as its leading technologies. An initial analysis is performed to evaluate the electricity generation and heat absorption by the storage system of the solar chimney. Moreover, thermal and membrane-based desalination technologies are included in a cascaded manner to produce freshwater, utilizing the heat source of the solar chimney thermal storage. In addition, a Pressure-Retarded Osmosis subsystem is incorporated to use the discharged brine from the desalination systems, creating an additional electrical output by recovering brine energy. A wind power plant is added for generating more power while satisfying the demand of the multisystem. For energy storage purposes, a pumped hydro system is implemented to store freshwater and meet electrical and water demand without interruption. As a result, the integrated system, including a 5 × 3.4 MW wind farm, presents an overall energetic efficiency of 52.53% during the discharge of the water tank, and 52.51% while storing the water. These efficiencies are significantly higher than a stand-alone solar chimney (0.44%) dedicated to electricity generation only.

Geothermal energy for food and water security for Yemen: a review

Yemen’s economy, food security, and energy have touched rock bottom due to the 2015 devastating war. The country’s imports have plunged from 13,292 million US$ in 2013 to 6580 US$ in 2015. In order to help Yemen fight poverty and hunger, the Food and Agricultural Organization of the United Nations Organization proposed to spend 218.5 million US$ to support about 80 million people affected due to food scarcity and hunger. In this paper, it is shown that part of this fund can be spent to develop geothermal energy in Yemen to provide food and energy security permanently. The cost of developing 1057 × 106 kWh of power from the Damt site would cost around 80 billion US$. Developing two such sites would cost well below the aid proposed by the (FAO 2019). This power can be utilized to establish desalination plants to provide fresh water. This will provide a permanent solution to water and food scarcity in the country. The levelized cost of generating 1 MWh power from geothermal sources is about 76 US$. Developing two such sites would cost well below the aid proposed by the FAO. According to the earlier work, 173 billion liters of freshwater can be generated using 1057 × 106 kWh of geothermal energy at 278 billion US$. Using fossil fuels, as source energy for desalination, the freshwater generation cost would be similar but at the cost of huge CO2 emissions.

Intelligent optimization of a hybrid renewable energy system-powered water desalination unit

The use of renewable energies for pumping and desalination of seawater and/or brackish water can be a viable solution to reach a more sustainable freshwater production and reduce environmental impacts. In this way, a new approach based on the design of experiment method for optimal sizing a stand-alone solar–wind-reverse osmosis desalination system is investigated. For this, system modelling is presented with the development of a single sizing parameter between desalination motor pump and reverse osmosis unit and a dynamic simulator of the proposed energy–water system with its energy management loop is developed using climatology year data of southern Tunisia. In optimization loop, the methodology with one-year dynamic simulation necessarily leads to very long convergence times of several days. To try to reduce this time, a track has been proposed which consists in using meta-models instead of dynamic simulators. In order to apply this track, a meta-model (hybrid spline) that represents the system constraints and objectives is investigated based on design of experiments tool and a bi-objective genetic algorithm is applied in the optimization process via the developed meta-model. Two objective functions are used: loss of power supply probability (reliability indicator) which is used to present the dissatisfaction of the water production and embodied energy (environmental indicator) which is used to compute energetic cost (MJ) and to evaluate the environmental impacts potential (across the whole life cycle). Optimal sizing of the system via meta-models instead of dynamic simulator led to encouraging results with significantly reduced CPU times (from several days to 13 min).

Systematic Analysis Reveals Thermal Separations Are Not Necessarily Most Energy Intensive

Summary At the industrial level, separation of a variety of mixtures is predominantly carried out by thermally driven processes such as distillation. Nevertheless, the current literature seems to suggest that much is to be gained by replacing these processes with alternative non-thermal methods, which will potentially require a fraction of the energy used by distillation. This is primarily due to the widespread perception that thermal separation processes, particularly those that involve vaporization, are highly energy intensive. However, this belief is not well founded, because it is based on extrapolation from comparisons in the literature, many of which make ad-hoc assumptions and result in incorrect conclusions. Our analysis shows that this confusion arises because the processes utilize different types of energy: heat and electricity. Here, we present a consistent framework that enables a fair comparison between different processes that consume different forms of energies. Using this framework, we refute the general perception that thermal separation processes are inherently the most energy intensive and conclusively show through the examples of two challenging mixtures constituting components with low relative volatilities, that distillation processes, when run properly, can consume remarkably lower fuel than non-thermal membrane alternatives, which have often been touted as more energy efficient.

Potential of solar desalination for irrigation in Tunisia

In arid countries like Tunisia, the need to find new sources of water for irrigation has become imminent. Desalination of seawater can be an alternative to irrigation. In this article, we take a look at the leading food companies specializing in desalination for irrigation around the world and the prospects for the solar energy desalination potential for irrigation in Tunisia. We have noticed that several companies invest money to desalinate water for agricultural purposes. However, the cost of a cubic meter of water sometimes remains high to go forward in this new technology.

Wetting-resistant photothermal nanocomposite membranes for direct solar membrane distillation

Efficient use of solar energy for desalination is one strategy to solve the world's water scarcity issues. In this work, a dual functional, omniphobic−photothermal nanocomposite membrane was developed to achieve wetting resistance and low energy consumption in desalination by direct solar membrane distillation (DSMD). The membrane was prepared by forming a hierarchical structure of 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FAS17) modified carbon black (CB) nanoparticles (NPs) on a polyvinylidene fluoride (PVDF) membrane surface. The fluorinated CB NPs absorbed sun light to provide localized heating for DSMD, which increased membrane flux by 25% upon simulated solar irradiation at one sun unit. The utilization efficiency of solar energy in the DSMD process, 75.4%, is more than one order of magnitude higher than the energy efficiency of the conventional direct contact membrane distillation process. Furthermore, the re-entrant structure formed by the CB NPs together with the hydrophobic FAS17 coating led to low surface energy and hence omniphobicity, increasing the contact angle of the 80 vol% ethanol-in-water from 0 to 94.2°. As a result, the dual functional membrane exhibited much higher resistance to wetting by surfactants. Whereas the pristine PVDF membrane was wetted by 0.2 mM SDS, SDS had no effect on the dual function membrane over the whole SDS concentration range tested (0.1–0.4 mM). The photothermal activity, improved thermal efficiency, and strong wetting resistance make the dual functional omniphobic−photothermal membrane an excellent membrane material for the DSMD process. • First membrane distillation membrane with omniphobic and photothermal properties. • The membrane achieves wetting-resistance and photothermal heating simultaneously. • Photothermal carbon black provides re-entrant structure for omniphobicity.

Biomimetic artificial water channel membranes for enhanced desalination.

Inspired by biological proteins, artificial water channels (AWCs) can be used to overcome the performances of traditional desalination membranes. Their rational incorporation in composite polyamide provides an example of biomimetic membranes applied under representative reverse osmosis desalination conditions with an intrinsically high water-to-salt permeability ratio. The hybrid polyamide presents larger voids and seamlessly incorporates I-quartet AWCs for highly selective transport of water. These biomimetic membranes can be easily scaled for industrial standards (>m2), provide 99.5% rejection of NaCl or 91.4% rejection of boron, with a water flux of 75 l m-2 h-1 at 65 bar and 35,000 ppm NaCl feed solution, representative of seawater desalination. This flux is more than 75% higher than that observed with current state-of-the-art membranes with equivalent solute rejection, translating into an equivalent reduction of the membrane area for the same water output and a roughly 12% reduction of the required energy for desalination.

Reverse Electrodialysis: Potential Reduction in Energy and Emissions of Desalination

Salinity gradient energy harvesting by reverse electrodialysis (RED) is a promising renewable source to decarbonize desalination. This work surveys the potential reduction in energy consumption and carbon emissions gained from RED integration in 20 medium-to-large-sized seawater reverse osmosis (SWRO) desalination plants spread worldwide. Using the validated RED system’s model from our research group, we quantified the grid mix share of the SWRO plant’s total energy demand and total emissions RED would abate (i) in its current state of development and (ii) if captured all salinity gradient exergy (SGE). Results indicate that more saline and warmer SWRO brines enhance RED’s net power density, yet source availability may restrain specific energy supply. If all SGE were harnessed, RED could supply ~40% of total desalination plants’ energy demand almost in all locations, yet energy conversion irreversibility and untapped SGE decline it to ~10%. RED integration in the most emission-intensive SWRO plants could relieve up to 1.95 kg CO2-eq m−3. Findings reveal that RED energy recovery from SWRO concentrate effluents could bring desalination sector sizeable energy and emissions savings provided future advancements bring RED technology closer to its thermodynamic limit.

All-Day Freshwater Harvesting through Combined Solar-Driven Interfacial Desalination and Passive Radiative Cooling.

Solar-driven interfacial evaporation has received increasing research attention for clean water generation, but freshwater harvesting often occurs only during daytime. Herein, we report a strategy for all-day freshwater harvesting through combining solar-driven interfacial desalination and dew water generation. Through spray-coating carbon nanotubes onto a flexible substrate that has high-infrared emittance in the atmosphere window, a dual functional film was prepared to efficiently absorb solar energy for desalination at daytime and passively cool down the surface temperature to collect dew water at night. By integrating the dual functional film within a three-stage membrane distillation device, the home-made system achieved a drinkable freshwater collection efficiency of 71.1% when desalinating seawater under 1 sun illumination and achieved a dew water collection rate of 0.1 L m-2 day-1 at night. The readily available low-cost raw materials, simple fabrication process of the dual functional films, and the resultant all-day freshwater collection systems make the combined solar-thermal interfacial desalination and dew water collection a promising solution to alleviate the freshwater shortage in many underdeveloped regions, arid areas, and islands.