Freshwater Yield Research Articles

Investigation of conical passive solar still by incorporating energy metrics, efficiency, and sensitivity analyses for sustainable solar distillation

The application of solar energy technology to solve the freshwater scarcity problem of society will contribute to the sustainable development goal of the United Nations. It will also recede the dependency on fossil fuels. This paper deals with the investigation of conical passive solar still (CPSS) by incorporating energy metrics, efficiency, and sensitivity analyses. Fundamental equations have been obtained from the thermal modelling of CPSS followed by experimental validation. The coefficient of correlation for water temperature is about 0.96, for condensing surface temperature is about 0.99 and for freshwater yield is also 0.99. The present work involves diverse monthly weather conditions for the performance analysis of CPSS. In the present work, a MATLAB-based computational code is used to compute hourly freshwater output, exergy, and energy assessment for their yearly results. Afterward, energy metrics and different efficiencies were computed, and the outcomes were compared with recent investigations. Finally, the energy payback time has been lowered by 161.40%. The energy production factor and life cycle conversion efficiency for CPSS were improved by 61.71% and 28.20%, respectively, compared with the conventional solar still. The comparative study of daily thermal efficiency reveals that the efficiency of CPSS is higher by 51.47% than V-type solar still.

A comparative numerical study of three similar passive solar stills: Single slope, V-type, and greenhouse

In this paper, three solar stills with similar geometries are numerically investigated for analysis and comparison. The solar stills include single slope, V-type, and greenhouse stills. Steady-state laminar flow numerical simulations with different water surface temperatures and cover glass temperatures are performed. Simulation results were confirmed with data from analytical and experimental models to ensure reliability. The results showed that the V-type still has a higher number of recirculation zones than that of single slope and greenhouse stills. These vortex regions are small, but the velocity magnitude is no less than the other two stills. This difference makes the freshwater yield and convection heat transfer coefficient of V-type still the largest. Daily freshwater productions of single slope, V-type, and greenhouse stills are 0.592, 0.673, and 0.623 kg/m2, respectively. Productivity at 15 PM is 2.5 times higher than the hours from noon to 14 PM. The natural convection heat transfer coefficient seemed to be unvaried with the temperature difference but changed strongly with the still geometry.

Investigations on a solar humidification dehumidification desalination system equipped with various packing materials and multi-stage bubble column dehumidifier.

This work presents the theoretical and experimental investigation of a solar-powered humidification dehumidification desalination (HDD) system with different humidifier packing materials and a two-stage bubble column dehumidifier (BCD). Naturally available coconut shells (CS) and coconut shells with drilled holes (CSH) on the surface to improve water permeability were used as packing materials in the humidifier, and their performance was compared with that of commercial-type pall ring (PR) and raschig ring (RR) packings. An in-house developed numerical model of the HDD system in conjunction with a flat plate solar water collector was used in this study. Steady-state experimental results showed that CSH packing exhibited the highest volumetric mass transfer coefficient (0.00852kg/s), resulting in maximum humidifier efficiency (96%) and freshwater yield (2.16kg/hr), followed by PR (0.00841kg/s, 94%, and 2.137kg/hr), CS (0.00831kg/s, 90%, and 2.127kg/hr), and RR (0.0081kg/s, 81%, and 2.087kg/hr) at feedwater mass flow rate of 1.5kg/min and humidifier inlet temperature of 75 [Formula: see text]. Furthermore, transient outdoor test results showed that using a two-stage configuration in a BCD increased the daily average effectiveness to 0.93, as against 0.79 for a single-stage BCD. Employing CSH instead of PR and RR packings in the humidifier reduced freshwater costs by 6.2% and 7.6%, respectively.

Experimental investigation on the performance of a pyramid solar still for varying water depth, contaminated water temperature, and addition of circular fins

The experimental investigation was meant to investigate the effect of water depth in the basin, the water temperature at the inlet of solar still, and adding circular fins to the pyramid solar still on freshwater output. The investigation was divided into three sections. The first area of research is to study effect of increasing water depth in the solar still, which ranged from 2 to 6 cm, second section concentrated on varying the inflow water temperature from 30 to 50ºC, and third section investigated the influence of incorporating circular fins into the solar still basin on the water output and quality. The experimental findings showed that basin depth considerably impacts freshwater flow. The highest significant difference, 38%, was recorded by changing the water level in the basin from 2 to 6 cm. Freshwater yielded the most at a depth of 2 cm, totalling 1250.3 mL, followed by 1046 mL at a depth of 3 cm. A water depth of 4 cm produced 999 mL, whereas a water depth of 5 cm made 911 mL. The lowest production occurred at a water depth of 6 cm, producing 732 mL; furthermore, including fins at the bottom increased productivity by 8.2%. Elevating the temperature from 30 to 50ºC of the inlet water led to a water output increase of 15.3% to 22.2%. These findings underscore the profound potential of harnessing solar energy to address global water challenges and pave the way for further advancements in efficient freshwater production

Energy, Exergy, Economic, Environmental, Exergoenvironmental, Exergoeconomic, and Enviroeconomic Analysis of Photovoltaic/Thermal System with Double‐Fan Arrangement for Effective Condensation and Evaporation: An Experimental Approach

Water is one of the basic needs for all living and nonliving things. It is important to sustain the available water resources effectively for future generations. A lot of studies are employed already to improve the performance of solar desalination systems rather than conventional methods. Subsequently, an experimental approach is proposed with energy, exergy, economic, environmental, exergoenvironmental, exergoeconomic, and enviroeconomic performance of photovoltaic/Thermal (PV/T) solar distillation system using two methods to enhance the fresh water yield production at feasible cost. First is the conventional solar still (CSS) with PV and second is PV with double fan solar still (DFSS) with optimized running time of the double fan, which increases the productivity of the solar distillation system. The results show that average daily energy and exergy efficiency of the system improve with DFSS (19.98%, 1.36%) than CSS (11.74%, 0.36%). The daily yield productivity of CSS is 1.618 L m−2 and is increased as 2.482 L m−2 with DFSS. Average cost of water yield production is also reduced with DFSS and estimated as 0.018$, 0.016$, and 0.015$ for the lifetime of 15, 20, and 30 years for CSS and 0.014, 0.013, and 0.012$ for DFSS. Overall, the proposed methodology shows promising results than the conventional approach.

A Study of PI Controller Tuning Methods Using the Internal Model Control Guide for a Ship Central Cooling System as a Multi-Input, Single-Output System

Since the variable-speed seawater pump and the three-way valve of a ship’s central cooling system are forms of feedback from the same output signal, these controllers may cause interference when they are not coordinated. Therefore, studying an efficient control tuning method for a central cooling water system is necessary. In this study, a central cooling water system is modeled using Matlab Simulink by utilizing an actual operation dataset, and unknown parameters are estimated for fine-tuning. The simulation model is then verified using the second operating dataset. Additionally, transfer functions are developed for the freshwater output temperature against the three-way valve openness input and the electrical power frequency input to the seawater pump motor, supposing that the two systems are independent. Then, the two PI controllers are tuned using internal model control (IMC) filters. Moreover, the modified internal model control tuning method is suggested, using the character of the central cooling system, which has a large time constant for the heat exchanger system with the seawater pump and a small time constant for the three-way valve system. This method simplifies the tuning of the two combined PI controllers, enhancing the seawater pump’s overall efficiency and the three-way valve’s operation. This study presents the proposed tuning methods based on the IMC filter and modified IMC guide, which confirmed the simple determination of the gain values of the PI controller with the efficient control of the rotational speed of the seawater pump and the three-way valve with reasonable control of the freshwater outlet temperature.

Clay-based aerogel combined with CuS for solar-driven interfacial steam generation and desalination

Solar-driven water purification is a promising technology that can effectively utilize solar energy for seawater desalination. However, poor materials are unable to meet the dense energy of solar steam generation in natural sunlight for real-time practical applications. Therefore, the demand for energy density can be increased by using improved semiconductor aerogel materials. Here, we report a simple chemical method to obtain a CuS@ATP/PS composite aerogel (named CuAP), which was made of attapulgite (ATP) and CuS loaded onto it using an N-template to give it good photothermal characteristics (CuS@ATP), and then cross-link it with potato starch (PS). The evaporation rate of CuAP-15 aerogel in pure water at 1 kW m−2 solar radiation is 1.57 kg m−2 h−1. Meanwhile, CuAP-15 aerogel showed excellent salt resistance with an evaporation rate of 1.35 kg m−2 h−1 in 20 wt% NaCl solution. And also exhibited excellent cycling durability in cycling stability tests. More importantly, the freshwater yield can reach 6.54 kg m−2 under natural light irradiation for 11 h. Therefore, CuAP aerogel has a great prospect of application in the field of seawater desalination in the future.

Performance Evaluation of a Novel Multigeneration Plant of Cooling, Power, and Seawater Desalination Using Supercritical CO2 Partial Cooling, ME-TVC Desalination, and Absorption Refrigeration Cycles

Multigeneration systems have gained popularity and approval from scientific minds due to the enhancements these systems bring to total energy utilization efficiency. The use of waste heat from different thermodynamic cycles ensures deceleration of environment pollution. In this paper, a newly conceptualized poly-generation system combining power, cooling and desalination is proposed. Despite the high efficiency generated by the next generation supercritical CO2 (sCO2) Brayton cycles, the pre-coolers (cooling components) of the power block experience a substantial amount of low-grade energy loss. Utilizing this energy loss to increase thermal efficiency further has been the driving force behind this research. The proposed system has three subsystems which are sCO2 Partial cooling cycle with reheat for power generation, followed by a ME-TVC (multi-effect desalination-thermal vapor compression) cycle for producing fresh water and finally an absorption refrigeration cycle (ARC) to provide refrigeration effect. The waste heat from precoolers of sCO2 partial cooling cycle are being utilized by the desalination plant and refrigeration cycle for enhanced system performance. A comprehensive mathematical model is developed and a parametric assessment is performed. The parametric investigation focuses on the primary performance parameters, namely net power output, freshwater yield, energy utilization efficiency, coefficient of performance, and gain output ratio, to assess the multi-generation system's performance across various operational scenarios. The variables that are optimized are turbine inlet temperature of the sCO2 cycle, temperature difference of the generator and the evaporating temperature of the absorption cycle, the number and temperature of the effects of the desalination system. The results show that the greatest energy efficiency of the developed system is up to 70%. The 1st law energy efficiency is termed as Energy Utilization Factor (EUF) in the present work. This term adheres to the logic of the first law of thermodynamics by relating the total energy outputs to the system (work plus refrigeration capacity and heat supplied to the desalination plant) to the total energy input. Using the default parameters, the COP of the ARC is 0.667 and the EUF of the combined system is 59%. Both of these values are higher when compared to previous combined cycles found in literature.

Renewable energy integration in water desalination: State-of-the-art review and comparative analysis

This paper offers a comprehensive overview of advanced water desalination systems powered by renewable energy sources, specifically focusing on developments in the past decade. Solar energy is particularly emphasized as a pivotal resource for powering diverse desalination methods, including membrane distillation, reverse osmosis, humidification-dehumidification, forward osmosis, and hybrid systems. The primary objectives of this study encompass evaluating current advancements in renewable energy systems, especially solar energy, for driving water desalination processes. Furthermore, the study aims to identify gaps in research, challenges, and recommendations within these processes, and to assess the performance and refinement potential of hybrid desalination systems. Through a comprehensive analysis of various investigations, integrated effectiveness and cost-efficiency are examined, focusing on practical energy utilization. Notably, the analysis reveals the potential of hybrid desalination systems to reduce energy consumption. For instance, the hybridization of forward osmosis with membrane distillation showcases a significant energy ratio decrease from 0.89 to 0.64. Moreover, the combination of humidification-dehumidification with reverse osmosis is shown to reduce energy usage while enhancing freshwater output by up to 38% compared to standalone reverse osmosis. However, challenges persist, such as the need for improved integration of hybrid systems with concentrated solar collectors like photovoltaic thermal and concentrated photovoltaic thermal technologies.

Experimental investigation of atmospheric air to water generation based on both end open evacuated tube collector solar air heater

Regional economic, social, and ecological security are all entwined and influenced by the availability of water. Since the available water resources are depleting at a very faster rate and people are restricted to access the clean water, it is urgent to discover new & alternative sources of fresh water to meet everyone's requirements. An inexpensive and effective solution to the rising problem of the water shortage can be atmospheric air to water generation (AWG) technology. This study involves the development and experimental investigation of a novel AWG system based on adsorption under ambient conditions. Both end open evacuated tube collector solar air heater (ETC-SAH) with 5.07 m2 solar collector area and an air-to-air condenser is used. The system’s performance is evaluated based on several key parameters, including adsorption & regeneration rate, energy & exergy efficiency, and economic analysis. The fresh water yield reported from the system is 3.08 L/day at 0.12 $/L cost. The energy & exergy efficiency reported by the system is 9.65% & 3.69%, respectively. Additionally, the water produced is subjected to testing at a regionally certified laboratory to confirm its safety for consumption.

Biomass‐Based Materials for Sustainably Sourced Solar‐Driven Interfacial Steam Generation

Solar‐driven interfacial water evaporation powered by solar energy has gained significant interest as a sustainable and cost‐efficient desalination technology, owing to its zero reliance on fossil fuels. It aligns the relationship between freshwater demand and environmental‐friendly water yields and provides us with a feasible and effective way to mitigate the global water crisis. Biomass‐derived photothermal evaporators stemming from sustainable and renewable resources and performing high freshwater output have piqued researchers’ interest in achieving water evaporation effectively, economically, and greenly. In this review work, biomass‐based photothermal evaporators coming from hydrogels, carbides, and fibers are summarized and their optical design, wettability, thermal management, and salt‐rejection ability are analyzed, presenting an overview of the current status of biomass‐based materials in the solar‐driven water purification system.

Performance evaluation of a solar humidification dehumidification desalination system employing a multistage bubble column dehumidifier

In humidification-dehumidification desalination (HDD) system, conventional dehumidifiers require a large condensing area due to the additional thermal resistance to the heat transfer caused by high concentrations (60–95% by mass) of non-condensable gases present in the air. In a bubble column dehumidifier (BCD), condensation of humid air via direct contact with cold water in a column can significantly decrease condensing area and cost. Hence, in this study, a solar-powered HDD using a multistage BCD is designed and tested in the climatic conditions of Kerala, India. Single-stage and two-stage configurations are investigated in BCD. A mathematical model based on the energy and mass balance of each component is also developed. The model results are observed to be in good agreement with experimental measurements. The results showed that the daily freshwater yield, day average gain output ratio (GOR), and average BCD effectiveness of HDD system with two-stage BCD are 4.571 kg/m2, 0.79, and 0.9, respectively. Furthermore, upgrading the single-stage configuration of BCD to a two-stage configuration increases freshwater yield, day average GOR, and BCD effectiveness by about 6.24%, 6.75%, and 17%, respectively. Detailed water quality analysis revealed that freshwater quality is well within drinking water standards. The cost of freshwater is about 0.0716 $/liter.

Enhancement of distillate quantity and quality of a hybrid solar desalination system

Clean water is a necessity, yet it is scarce due to the increase in demand. Desalination is the most reliable way of getting clean water. The commonest desalination process used and suitable in rural areas is solar still distillation. Although it faces low clean water production and requires enhancements alongside quality checks. This study aims to develop an improved solar desalination system with improved quantity and quality. This was achieved by introducing a heating water element powered by a photovoltaic system and a pre-treatment system using granulated charcoal with different dosages because of its adsorption properties to reduce pollutant strength before desalination. The results showed a 300% increase in freshwater yield from the conventional system. The pre-treatment system reduces pollutant strength by 25.08%. This indicates significant water quantity and quality improvement. In that regard, the work significantly will contribute to improving water quantity and quality in solar still.

A three-dimensional folded multistage distillation device with enhanced air convection for efficient solar interface evaporation

Solar interface evaporation technology is widely used as an effective method of vapor generation. However, the convection and condensation processes that follow vapor generation have received little attention, limiting the actual freshwater output. In this study, we designed an innovative 3D folded structure with enhanced light absorption and air convection for the multistage distillation device. It is demonstrated that the 3D folded structure increases the average air flow velocity by 3 orders of magnitude compared to the conventional flat structure. As a result, the device achieves higher evaporation efficiency with less energy input, with a 7-stage device achieving an evaporation rate of 3.22 kg m−2 h−1 at 1 kW m−2 light intensity. In addition, we have designed an effective salt tolerance strategy for the new structure, with zero liquid discharge and easier salt collection. The experiment proved the stable operation of the device in high concentration brine at 20 wt%. This new structure provides a new idea for the interface evaporator to improve fresh water production and practicality.

Investigation of a distillation desalination system driven by solar and ocean thermal energy

Ocean thermal energy is a stable and abundant marine renewable energy that can be adopted for sustainable desalination in remote islands. However, its relatively low available temperature difference restricts its application. Therefore, to manipulate ocean thermal energy while overcoming its unique small thermocline temperature gradient, a dual-energy-driven distillation desalination system driven by solar and ocean thermal energy is put forward. The merits of this system include resolving the nightly failure of solar desalination systems and higher productivity. To quantify the system potential, a numerical model is developed and thermodynamic analysis is conducted. A comparison between dual-energy-driven system and single-energy-driven systems is conducted. The results indicate that the yield can be significantly improved by simultaneously using solar and ocean thermal energy. A single ocean thermal energy-driven desalination can achieve the minimum freshwater productivity of 0.07 kg·h−1, while coupled solar thermal energy can improve freshwater yield to 1.21 kg·h−1, which is 30.1 % higher than that of a single solar desalination. The system power consumption is only 1.77 kW·h/ton. Furthermore, based on the actual meteorological data in Haikou, China, an annual freshwater productivity of 3524 kg (for a 1 m2 absorber plate area) can be obtained, corresponding to a gain output ratio of 0.44.

Solar steam-driven membrane filtration for high flux water purification

In recent years, interfacial solar steam generation has shown great potential for desalination with high solar-to-steam conversion efficiency. However, the freshwater production rate is still limited by the substantial latent heat of water evaporation and condensation efficiency. Here we designed an interfacial solar steam-driven reverse osmosis/nanofiltration device that generates high pressure that pushes water molecules through a filtration membrane to achieve separation from ions. The solar steam-driven reverse osmosis device reaches a water production rate as high as 81 kg m−2 h−1 under 12 sun illumination. Moreover, a theoretical model indicates that there still exists attractive room to further improve the freshwater output by optimizing the thermal insulation and expansion ratio of the device. This work paves a new way to design highly efficient miniaturized or decentralized drinking water devices. Reverse osmosis of seawater is a popular though energy demanding process to produce freshwater. Interfacing reverse osmosis membranes with solar steam generation shows potential for a more efficient desalination process.

RETRACTED: Performance and exergy analysis of an inclined solar still with baffle arrangements

This study presents the details of performance and exergy investigations on an inclined solar still with baffle arrangements. The shortage of consumable water creates the transformation of accessible brackish water into consumable water an unavoidable one and this can be accomplished utilizing sun-oriented refining. To remove drinkable water from pungent water, sun-oriented still is broadly utilized. To build the contact season of the pungent water with sunlight-based brilliance, perplex course of action is set to expand the opposition in the stream. This prompts more vanishing of brackish water. Therefore, the objective of this study is to improve freshwater yield. The experimental study is performed for two different mass flow rates (mf1 = 0.0833 kg/min and mf2 = 0.166 kg/min). An increase in the mass flow of water directly deteriorates the yield of fresh water. Highest accumulated freshwater yield is achieved as 2.908 kg/m2 day during the month of May for mf1 = 0.0833 kg/min. The accumulated freshwater yield improved by 4.23% in comparison with inclined solar still designs. Moreover, the yield is better by 3.49%–61.56% in comparison with various solar still designs. Using RSM, a polynomial statistical model is specified to estimate as well as maximize the freshwater yield of ISSB. The exergy analysis for mf1 = 0.0833 kg/min shows a maximum hourly exergy efficiency of 6.82%.

The impact of the corrugated absorber shape on the performance of a hemispherical solar still for water desalination: an experimental study

Solar stills utilization has received great interest in arid isolated regions. In this study, experimental approaches have been investigated to prove the impact of the corrugated absorber shape on the hemispherical solar still performance. Four geometric corrugated shapes including present flat, triangular, semi-circular, square forms were tested for the corrugated absorber. Five hemispherical solar distillers have been fabricated and tested. The first distiller includes flat absorber (HSD-FA), the second distiller includes square corrugated absorber (HSDSA), the third distiller includes semi-circular corrugated absorber (HSD-SCA), the fourth distiller includes triangular corrugated absorber (HSDTA), and the fifth distiller is conventional (CHSD). The first and second distillers were compared with the CHSD on the first day. On the second day, the third and fourth distillers were compared with the CHSD as well. Experimental results obtained showed that, the total freshwater yield of the HSD-FA, HSDSA, HSDSCA and HSDTA were improved by 16.67, 27.08, 39.58 and 48.96%, respectively, compared over that of the CHSD. These results prove that the use of the triangular corrugated absorber shaped provides the highest thermal efficiency, and the optimum corrugated absorber shape is the triangular corrugated absorber shape.

Reversed vapor generation with Janus fabric evaporator and comprehensive thermal management for efficient interfacial solar distillation

Interfacial solar steam generation, with high energy efficiency, promotes the solar desalination technology to a new era. However, the problem of low freshwater yield in enclosed distillation system owing to optical loss and insufficient condensation capability remains a challenge. In this work, a reversed interfacial solar distillation system is proposed by combining Janus fabric with comprehensive thermal management to significantly enhance the freshwater yield. Recycled cotton fabric is used to fabricate the low-cost Janus fabric with carbon black@silicone on the top side via a simple and scalable pre-wet coating method. The Janus fabric with high sunlight absorbance (98.0 %) and good sealing properties remarkably guarantees the downward vapor generation to eliminate the optical loss, resulting in the improved freshwater collection of the distiller. Comprehensive thermal management is designed for the distillation system to reduce the heat loss of the evaporator and enhance the condensation effect of the condenser. The optimal Janus fabric-based interfacial solar distiller achieves an outstanding water yield of 1.17 kg m−2h−1 and an efficiency of 78 % under one sun (1 kW m−2) illumination. This work presents a novel design of a high-performance interfacial solar distillation system, offering the potential for large-scale and low-cost industrial production.

Experimental study of a standalone membrane water desalination unit fully powered by solar energy

In this study, a fully solar-driven water desalination system is designed, fabricated, and tested. The proposed system is designed for remote, isolated areas with limited electricity and freshwater access. For commercial PVDF membranes, the performance of the MD unit is evaluated at various feed temperatures, flow rates, and salt concentrations. In addition, the effect of MD cell design was examined to determine the effect of the obstacles on the feed channel. Increasing the temperature by 20 degrees from 55 to 75 °C enhances productivity by 165 % from 6.2 to 16.4 kg/m2.h. At different operating conditions, the new design of the MD cell with cylindrical obstacles attained higher flux productivity compared to the conventional MD cell design. The maximum attained freshwater output flux was around 15 kg/m2.h at a feed inlet temperature of 65 °C and feed mass flowrate of 66 kg/h for the MD cell with cylindrical obstacles. In the presence of obstacles, a reduction in the specific energy consumption (SEC) by 35–15 % is associated with an increase in the gain output ratio (GOR) by 50–20 % compared to the case of no obstacles. Observations indicate that a small PV module with an area of 0.377 m2 is sufficient to operate the membrane unit for contentious 15 h. Collectively, using solar MD units collectively has the potential to be used for decentralized desalination of water.