Renewable energy-driven desalination opportunities - A case study

Experimental study on a solar-powered cogeneration system for freshwater and electricity production

In this study, a photovoltaic/thermal (PVT) collector and a stepped solar still system were constructed and integrated. The PVT collector was used to improve the performance of a stepped solar still device. Saltwater enters into the PV-T system and the temperature of the solar panel declines, and then ultimately the efficiency of the PV-T collector increases. After leaving the PVT collector, the temperature of the saltwater increased and was used as a pre-heater for further evaporation in the solar still, which ultimately caused an increase in its efficiency. The more tremendous temperature difference generated between the stepped surface and the glass increases efficiency and produces more freshwater. A flow rate of 7.5 L/hour of saline water was used to study the efficiency of the solar still device and the PVT collector. The value of productivity of solar still system with photovoltaic/thermal collector was 0.76 kg/m2 more than that of conventional solar still. Despite the PVT collector, the daily efficiency of the solar still system increased to 34.8%, which shows an increase of 13.9% compared to the passive solar still device. Also, by cooling the PV-T system, the average electrical efficiency has increased from 13.1 to 13.7%. Production power reached 72.46 W from 65.96 W in two consecutive days at 11:15.

A review on role of solar photovoltaic (PV) modules in enhancing sustainable water production capacity of solar distillation units

Sustainable production of potable water is one of the United Nations sustainable development goals set for 2030. Among available renewable energy resources, solar energy is abundantly available in most of the fresh water scarce rural and remote locations. Moreover, solar distillation units and solar photovoltaic (PV) modules have been acknowledged as suitable candidates for addressing rising fresh water and electricity demands in these regions. In recent years, researchers have proposed a number of novel hybrid solar distillation units where the solar PV modules are integrated with solar thermal distillation units in different ways to harvest both electric power and potable water. In this work, a detailed review highlighting the classification, working principle, performance and features of these novel hybrid units have been carried out. In most of these hybrid units, integration is highly beneficial for solar thermal distillation units rather than for PV modules. Direct utilization of PV module as absorber, condenser and reflector in solar stills has few drawbacks. However, indirect utilization like utilizing electric power and waste heat energy recovered from PV module in distillation units has posed significant distillate yield enhancement up to 300.0%. In some cases, the integrated PV module has even generated sufficient power for carrying out essential domestic activities. Integrated PV module's performance has also improved significantly in few studies but the magnitude of improvement has not been disclosed clearly in most of the studies as more focus has been given to distillation units rather than PV modules. However, these novel hybrid configurations have not been fully explored & optimized and their techno-enviro-economic aspects have not yet been disclosed in these available precious literatures and they are still available as a potential research gap.

Recent Progress in Renewable Energy Based-Desalination in the Middle East and North Africa MENA Region

BACKGROUND

The Middle East and North African (MENA) countries are rapidly growing in population with very limited access to freshwater resources. To overcome this challenge, seawater desalination is proposed as an effective solution, as most MENA countries have easy access to saline water. However, desalination processes require massive demand for energy, which is mostly met by fossil fuel-driven power plants. The rapid technological advancements in renewable energy technologies, along with their gradually decreasing cost place renewable energy-driven power plants and processes as a promising alternative to conventional fuel-powered plants.

AIM OF REVIEW

In the current work, renewable energy-powered desalination in the MENA region is investigated. Various desalination technologies and renewable energy resources, particularly those available in MENA are discussed. A detailed discussion of suitable energy storage technologies for incorporation into renewable energy desalination systems is also included.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The progress made in implementing renewable energy into power desalination plants in MENA countries is summarized and analyzed by describing the overall trend and giving recommendations for the potential amalgamation of available renewable energies (REs) and available desalination technologies. Finally, a case study in the MENA region, the Al-khafji solar seawater reverse osmosis (SWRO) desalination plant in the Kingdom of Saudi Arabia KSA, is used to demonstrate the implementation of REs to drive desalination processes.

Analysis of the Water-Energy Nexus Applied to an Insular System: Case Study of Tenerife

Insular territories face important challenges in achieving effective sustainable development, mainly due to low internal availability of basic resources, which results in a high external dependency. The analysis of the energy–water nexus of islands is a powerful instrument to evaluate the sustainable goals of the region and to identify the key actions to take to fulfill these objectives in future scenarios. The aim of this study is to review the energy–water nexus applied to Tenerife (Canary Islands), considering three scenarios: the base case scenario, corresponding to the current situation, where 1.1% of consumed water is dedicated to energy production and 10.2% of the energy is supplied for water abstraction, depuration, and ocean discharge; and two projections for the year 2050: a maintained trend scenario, and an ecology-aware scenario, where the population growth and the deployment of electrical vehicles are considered. In 2018, the total energy consumed was 1954 ktoe, of which renewable energy made up 2%. In the maintained trend scenario, this amount rises to 2003 ktoe, of which renewable energies represent 29%. However, in the ecology-aware scenario, this amount could be reduced to 1710 ktoe of which 51% of energy is obtained from renewable sources.

Updates on Evaporation and Condensation Methods for the Performance Improvement of Solar Stills

Solar still, a small equipment using evaporation and condensation processes to get clean water, is expected to be widely used for sea/brackish water desalination, water purification, and wastewater treatment because of its convenient carrying, friendly environment, and low energy consumption. In recent years, considerable progress has been made in improving the productivity of solar still. This paper will reclassify the methods to improve the solar still by elevating the evaporation rate and condensation rate. The main methods increasing evaporation rate are as follows: (i) adding heat storage materials; (ii) using nanoparticles; (iii) changing structure of the absorption plate; and (iv) using photothermal materials. The primary methods increasing the condensation rate are as follows: (i) cooling the condensing surface; (ii) increasing the condensation area; (iii) changing the wettability of the condensing surface; and (iv) using a separate condenser. The advantages and disadvantages of each method are compared. Furthermore, this paper includes an economic analysis of current solar stills and a forecast of future developments. The freshwater cost of solar still is in the range of about USD 0.0061–0.277/L, which provides reference and direction for future researching solar stills on their low cost and high productivity.

The feasibility of solar-powered small-scale brackish water desalination units in a coastal aquifer prone to saltwater intrusion: A comparison between electrodialysis reversal and reverse osmosis

In the face of increasing water shortages worldwide, water desalination has the potential to expand the available freshwater supply options in many water stressed regions. This paper assesses the feasibility of adopting photovoltaic powered small-scale brackish water desalination units in a coastal aquifer facing saltwater intrusion and chronic water shortages. Moreover, a detailed cost comparison, which incorporates the associated environmental costs, is conducted between the Electrodialysis Reversal (EDR) technique and Reverse Osmosis (RO). The results showed that PV-powered small-scale desalination units were more economically viable as compared to grid-powered units, when the electricity tariffs reflected non-subsidized electricity prices and environmental costs were internalized. EDR-PV proved to be more economically feasible and with a lower environmental footprint as compared to RO-PV, up until the salinity of the aquifer was below 5000 ppm (EDR: 0.57-1.18 $/m³; RO = 1.19-1.59 $/m³). Beyond that salinity, the RO-PV was found to be the more economically viable option, with costs reaching as high as 2.65 $/m³ at a salinity of 25,000 ppm. Overall, the environmental costs between the two technologies varied significantly, largely due to differences in the generated brine volume, with EDR having better efficiencies at lower salinity levels. Finally, the study highlighted the risk of accelerating saltwater intrusion as a result of the increased market penetration of solar-powered desalination units along vulnerable coastal aquifers.

Molecular dynamics simulation for membrane separation and porous materials: A current state of art review

Computational frameworks have been under specific attention within the last two decades. Molecular Dynamics (MD) simulations, identical to the other computational approaches, try to address the unknown question, lighten the dark areas of unanswered questions, to achieve probable explanations and solutions. Owing to their complex microporous structure on one side and the intricate biochemical nature of various materials used in the structure, separative membrane materials possess peculiar degrees of complications. More notably, as nanocomposite materials are often integrated into separative membranes, thin-film nanocomposites and porous separative nanocomposite materials could possess an additional level of complexity with regard to the nanoscale interactions brought to the structure. This critical review intends to cover the recent methods used to assess membranes and membrane materials. Incorporation of MD in membrane technology-related fields such as desalination, fuel cell-based energy production, blood purification through hemodialysis, etc., were briefly covered. Accordingly, this review could be used to understand the current extent of MD applications for separative membranes. The review could also be used as a guideline to use the proper MD implementation within the related fields.

Assessing Future Water Demand and Associated Energy Input with Plausible Scenarios for Water Service Providers (WSPs) in Sub-Saharan Africa

This study examined the current state of water demand and associated energy input for water supply against a projected increase in water demand in sub-Saharan Africa. Three plausible scenarios, namely, Current State Extends (CSE), Current State Improves (CSI) and Current State Deteriorates (CSD) were developed and applied using nine quantifiable indicators for water demand projections and the associated impact on energy input for water supply for five Water Service Providers (WSPs) in Kenya to demonstrate the feasibility of the approach based on real data in sub-Saharan Africa. Currently, the daily per capita water-use in the service area of four of the five WSPs was below minimum daily requirement of 50 L/p/d. Further, non-revenue water losses were up to three times higher than the regulated benchmark (range 26–63%). Calculations showed a leakage reduction potential of up to 70% and energy savings of up to 12 MWh/a. The projected water demand is expected to increase by at least twelve times the current demand to achieve universal coverage and an average daily per capita consumption of 120 L/p/d for the urban population by 2030. Consequently, the energy input could increase almost twelve-folds with the CSI scenario or up to fifty-folds with the CSE scenario for WSPs where desalination or additional groundwater abstraction is proposed. The approach used can be applied for other WSPs which are experiencing a similar evolution of their water supply and demand drivers in sub-Saharan Africa. WSPs in the sub-region should explore aggressive strategies to jointly address persistent water losses and associated energy input. This would reduce the current water supply-demand gap and minimize the energy input that will be associated with exploring additional water sources that are typically energy intensive.

Comparative Analysis of Conventional and Emerging Technologies for Seawater Desalination: Northern Chile as A Case Study

The aim of this work was to study different desalination technologies as alternatives to conventional reverse osmosis (RO) through a systematic literature review. An expert panel evaluated thermal and membrane processes considering their possible implementation at a pilot plant scale (100 m³/d of purified water) starting from seawater at 20 °C with an average salinity of 34,000 ppm. The desalination plant would be located in the Atacama Region (Chile), where the high solar radiation level justifies an off-grid installation using photovoltaic panels. We classified the collected information about conventional and emerging technologies for seawater desalination, and then an expert panel evaluated these technologies considering five categories: (1) technical characteristics, (2) scale-up potential, (3) temperature effect, (4) electrical supply options, and (5) economic viability. Further, the potential inclusion of graphene oxide and aquaporin-based biomimetic membranes in the desalinization processes was analyzed. The comparative analysis lets us conclude that nanomembranes represent a technically and economically competitive alternative versus RO membranes. Therefore, a profitable desalination process should consider nanomembranes, use of an energy recovery system, and mixed energy supply (non-conventional renewable energy + electrical network). This document presents an up-to-date overview of the impact of emerging technologies on desalinated quality water, process costs, productivity, renewable energy use, and separation efficiency.

A Hydrostatic Pressure-Driven Desalination System for Large-Scale Deep Sea Space Station

Compared with the common marine renewable energy sources like solar, wind, and wave energy, etc., the hydraulic pressure stored in the deep seawater can output stable and successive energy flow. Thus, it can be directly coupled with the reverse osmosis (RO) process to supply drinkable mineral water for crews of Deep Sea Space Station (DSSS). We proposed a novel submarine RO desalination system driven by the hydraulic pressure of deep seawater (SHP-RO), composed of a desalination branch to generate fresh water and a back pressure branch to ensure the depth independence of the desalination. The influences of the deep sea environment on the RO were analyzed, based on which the pretreatment of the seawater and the preparation of the drinkable mineral water were studied. The turbine-based energy recovery scheme was investigated in virtue of the CFD simulation on the flow behavior in the different turbine series. It was predicted that, when the DSSS was located at the depth of 1100 m and the operating pressure of the RO process was 6.0 MPa, for a drinkable water production rate of 240 m3/d, the recovered hydraulic pressure energy can achieve 39.22 kW·h, which was enough for driving electricity consumers in the SHP-RO system.

The Role of Renewable Energy Resources in Sustainability of Water Desalination as a Potential Fresh-Water Source: An Updated Review

Desalination is becoming a practical option to meet water demand in an increasing number of locations that are facing water scarcity. Currently, more than 150 countries in the world are already using desalination technologies, which account for about one percent of the world’s drinking water. Although for specific regions, desalination is the only feasible solution to close the supply–demand gap (for example the production of desalinated seawater in the Middle East is predicted to rise almost fourteen-fold by 2040), the sustainability of desalination systems is still remarkably under question. This review aims first to investigate the technical and economic trends and environmental and social aspects of desalination systems and then, in the second stage, to give an overview of the role of renewable energy technologies in the sustainability of the future water systems with an increasing share of desalination.