Improving the productivity of solar still by using water fan and wind turbine

doi:10.1016/j.solener.2017.03.041

Solar Energy

Volume 147, 1 May 2017, Pages 181-188

https://doi.org/10.1016/j.solener.2017.03.041 Get rights and content

Highlights

•
Performance of modified still with water fan and wind turbine was investigated.
•
Performance of stills is influenced by the fan speed and water depth.
•
FSS productivity is higher than that of conventional still by 17% at 3 cm and 30 rpm.
•
The daily efficiency of FSS is improved to be 39.8%.
•
Daily productivity of still increases with raising the wind turbine speed.

Abstract

This investigation explores the potential benefits of using water fan inside a conventional solar still (CSS) to solve the problems in our previous work (Kabeel et al., 2012) under different conditions. Two stills, CSS and fan solar still (FSS), were constructed and tested under environmental conditions. The fan fixed inside the FSS was operated using a wind turbine. Different water depths of FSS (1, 2, 3 and 4 cm) were investigated. It was found that the distillate of still increments with integrating the fan. During experimentations, the maximum productivity of FSS is achieved at water depth of 1 cm for fan rotational speeds less than 22 rpm, and at 3 cm for speeds greater than 22 rpm. Using water fan in CSS enhanced the daily productivity by about 17% at 3 cm and 30 rpm. Whilst, the daily efficiency of fan still was approximately 39.8% compared to 36.7% in our previous work at the same conditions.

Introduction

Extracting the potable freshwater from saline/brackish water is a function of solar still that can be utilized. These devices are suitable for a single house or a small community for providing good quality drinking water. The productivity of fresh water by CSSs is limited as investigated by many researchers. In addition, thermal efficiency of CSSs is low (∼35–40%) with normal daily productivity of 3–4 L/m² d (Yadav and Sudhakar, 2015).

Several techniques and designs have been developed to improve efficiency and productivity of CSSs, such as double-basin (Al-Karaghouli and Alnaser, 2004), multi-effect (Tanaka and Nakatake, 2007), regenerative (Abu-Arabi and Zurigat, 2005), stepped still (Ziabari et al., 2013), corrugated wick (Omara et al., 2015), tubular solar (Ahsan and Fukuhara, 2010), conical still (Gad et al., 2015), solar still with reflectors (Tanaka, 2010, Tanaka and Nakatake, 2009), rotating drum (Lilian et al., 2016), solar collectors (Voropoulos et al., 2003), with fins and sponges (Velmurugan et al., 2008), internal condenser (Al-Nimr and Dahdolan, 2015), and hybrid solar still (Voropoulos et al., 2003), special designs (hemispherical, spherical, triangular, concave, etc.) (Durkaieswaran and Kalidasa, 2015) and using nanofluids (Lovedeep and Tiwari, 2016). A review of different techniques and designs of various solar stills was made by (Mojtaba et al., 2016, Sivakumar and Ganapathy, 2013).

The various factors that affect the daily distillate of multiple-effect stills integrated with a solar collector were investigated by Tanaka and Nakatake (2007). Also, influence of inclination of external collector of conventional still in winter was conducted by the same researchers.

Ziabari et al. (2013) simulated a stepped still under two climatic conditions of Koshk and Bandar Abbas, Iran. Results demonstrated that the average productivity of freshwater was 6.7 L/m²/d, which was higher by 26% in comparison with the initial site (Koshk village). Ahsan and Fukuhara (2010) proposed a new model of heat and mass transfer of a tubular still. They found that, the heat balance of the humid air and the mass balance of the water vapor in the humid air were formulized for the first time.

Tanaka (2010) conducted a numerical study to investigate the effects of external reflectors and internal reflectors on the conventional still. He concluded that the daily productivity could be increased by inclining the external reflector forward in all seasons except for in summer become backward. A conventional solar still integrated with a rotating drum enhanced more daily distillate compared with a conventional one (Lilian et al., 2016). The speed of drum and saline water level were ranged from 0.25 to 4 rpm and 1 to 5 cm, respectively. They found that daily distillate is inversely proportional to drum speed.

A conventional still, a conventional collector and a storage tank were connected together (Voropoulos et al., 2003) to study the influence of augmentation on the solar still. The solar still inlet was connected to solar collector (fin type) as its outlet was fed to the solar still. They indicated that the productivity utilizing augmentation was improved by 52% with saline water as a feed. Al-Nimr and Dahdolan (2015) modeled a novel concentrated still that increases with an internal condenser and a porous evaporator, for different condenser and ambient temperatures, solar irradiations and wind speeds, using Microsoft Excel software. They concluded that a reduction in temperature of condenser and the speed of wind alleviated the efficiency and productivity of the solar still.

The daily distillate of still depends on the heat transfer mechanism and working temperature. The heat transfer coefficients can be increased by enhancing the thermo-physical properties of saline water. Suspension of nanoparticles into saline water is a simple technology which enhances the thermo-physical properties (Lovedeep and Tiwari, 2016).

The fresh water amount condensed in CSS depends on the glass cover temperatures and velocity of air flows on the outer surface of cover of glass. Al-Hinai et al. (2002) predicted dependency of solar still distillate on operational parameters and climatic by using a theoretical model. Their results showed that an increase of 1–3 m/s leads to 8% augmentation of distillate.

An experimental and theoretical study on a solar still was developed by Abu-Qudais et al. (1996). In this work, an increase in water productivity was observed when the velocity of air was higher than 1.5 m/s, and decreases for a velocity of air of 3 m/s. This means that any additional cooling reduced the water temperature in the basin, i.e. a slight breeze was sufficient to enhance the efficiency. An experimental research on a CSS was developed by Margarita et al. (2015). His results showed increments in the production and total efficiency when the velocity of air increases up to 5.5 m/s. Above this velocity, these increments were diminished. In addition, he concluded that the optimum velocity is achieved at 3.5 m/s.

Zeinab and Ashraf (2005) used a rotating shaft with horizontal axis introduced near to the water surface of the absorber of solar still to improve still performance. They used an electrical motor to rotate the shaft. Their results showed that the still thermal efficiency was improved by 5.5% at July, 5% at June, and 2.5% at May.

Eltawil and Zhengming (2009) presented a hybrid desalination system that constitutes of inclined solar water distillation (ISWD) and wind turbine (to rotating horizontal shaft) integrated with main solar still (MSS). The effect of change water depths (1, 2 and 3 cm), different flow rates of feeding water (25.0, 41.7 and 58.3 ml/min) and two modes of operation as due south and tracking the sun are consider. They indicated that the daily water productivity from the ISWD could be higher than the MSS by about 26.55–29.17%.

In our previous study (Kabeel et al., 2012), we have experimentally attempted to improve the fresh water production of CSS by using a rotating water fan with a vertical shaft. A photovoltaic system (PV) used to power a DC-motor, which used to rotate the water fan. The effect of the water fan speed (ranged from 30 to 45 rpm) and the saline water depth (ranged from 1 to 7 cm) on the performance of the still was studied. Experimental results indicated that the still production increases with fan speed and the maximum difference of yield between FSS and CSS is obtained at water depth of 3 cm (with fan rotation). In addition, we concluded that utilizing water fan enhances the yield by about 25% at a speed of 45 rpm, and a depth of 3 cm.

In the same study, some difficulties are created and not solved. The vertical shaft of rotating fan passes through the still base through ball bearing, so that this connection increases the chance of leaking. In addition, the initial cost of the PV system is high and the projected area of PV cell is considered in still efficiency calculations.

The aim of this study is solve the problems in our previous work. In the present work water fan powered by wind turbine is used to increase the distillate of CSS. The rotating shaft passes through back side wall of still, so there is not leaking. In addition, initial and maintenance costs are reduced. The new system has small space about previous system.

Section snippets

Experimental setup

To eliminate the influence of experimental conditions, two solar stills (FSS and CSS) were manufactured, Fig. 1. The FSS prepared with a water fan works with wind turbine.

Experimental procedures

The experimental tests were carried out at University of Prince Sattam bin Abdulaziz, KSA, and the tests were performed from 8 am to 6 pm during July and November 2015. Every 1 h the accompanying parameters were measured for various depths and various modes of experimentations: atmospheric temperature, solar irradiation, glass cover temperature, saline water temperature and water productivity, while the velocity of wind was measured every 0.5 h. The totally accumulated productivity is also

Experimental uncertainty analysis

The present study used the same method proposed by (Holman, 1994) for estimating the uncertainty in the results. Suppose a set of measurement is made in order to measure “n” number of experimental variables. These measurements are then used to calculate some desired result of the experiment (R). Thus $R = R (X_{1}, X_{2}, X_{3} . . . . . . . . . . . . . . . . . ., X_{n})$

Let W_R be the uncertainty in the result and W₁, W₂, W₃,…..….................W_n be the uncertainties in the independent variables. The uncertainty in result is

Experimental results and discussion

Experimental results carried out in this study are used to discuss and put more shed on the effects of, water productivity, solar irradiation, wind velocity, water depth, daily efficiency and hourly efficiency.

Conclusions

Effect of incorporating wind turbine and water fan into conventional still was investigated to indicate how much this modification effects on solar still performance. In this study, the following points can be concluded:

•
The daily amount of distillate is affected by the water depth and the wind turbine rotational speed.
•
An effective method to enhance the rate of evaporation, and hence improving the freshwater production is proposed and is based on using a fan inside the solar still.
•
The amount of

References (28)

M. Abu-Arabi et al.
Year-round comparative study of three types of solar distillation units
Desalination
(2005)
M. Abu-Qudais et al.
Experimental study and numerical simulation of a solar still using an external condenser
Energy
(1996)
A. Ahsan et al.
Mass and heat transfer model of tubular solar still
Sol. Energy
(2010)
H. Al-Hinai et al.
Parametric investigation of a double-effect solar still in comparison with a single-effect solar still
Desalination
(2002)
A.A. Al-Karaghouli et al.
Experimental comparative study of the performances of single and double basin solar-stills
Appl. Energy
(2004)
M. Al-Nimr et al.
Modeling of a novel concentrated solar still enhanced with a porous evaporator and an internal condenser
Sol. Energy
(2015)
P. Durkaieswaran et al.
Various special designs of single basin passive solar still – a review
Renew. Sustain. Energy Rev.
(2015)
M.A. Eltawil et al.
Wind turbine-inclined still collector integration with solar still for brackish water desalination
Desalination
(2009)
H.E. Gad et al.
Thermal analysis of a conical solar still performance: an experimental study
Sol. Energy
(2015)
Z.M. Omara et al.
Effect of using nanofluids and providing vacuum on the yield of corrugated wick solar still
Energy Conserv. Manage.
(2015)

M.K. Phadatare et al.

Influence of water depth on internal heat and mass transfer in a plastic solar still

Desalination

(2007)

Saurabh Yadav et al.

Different domestic designs of solar stills: a review

Renew. Sustain. Energy Rev.

(2015)

V. Sivakumar et al.

Improvement techniques of solar still efficiency: a review

Renew. Sustain. Energy Rev.

(2013)

H. Tanaka

Monthly optimum inclination of glass cover and external reflector of a basin type solar still with internal and external reflector

Sol. Energy

(2010)

Cited by (83)

Utilizing the dangled jute cords, reflectors, and condensation cycle to improve the double sloped distiller performance
2024, Solar Energy
The global water scarcity issue affects various regions, especially those distant from urban centers, making solar stills a vital solution. However, these systems suffer from limited productivity. This study investigates the operation of a cords wick double slope distiller (WDSSS) under different conditions. It examines the impact of varying cord counts (9, 16, 25, & 35 cords) and tests the influence of using reflectors and a condensation cycle with WDSSS. The results indicate that the optimal performance for WDSSS, both with and without reflectors and a condensation cycle, is achieved with 25 and 35 cords, respectively. Furthermore, at the 25-cord configuration, the WDSSS without the use of either reflectors or a condensation cycle demonstrated a 140 % increase in yield compared to a conventional solar still (7200 vs. 3000 mL/m².day, respectively). In addition, the WDSSS with reflectors and 25 cords exhibited an 180 % improvement in yield over the conventional solar still (9500 vs. 3400 mL/m².day, respectively). Moreover, at 25 cords, the combined effect of condensation and reflectors substantially boosted the WDSSS yield by 212 % compared to the conventional solar still (11250 vs. 3600, respectively). Finally, the highest performance of the WDSSS was achieved with reflectors and a condensation cycle using 35 jute cords, resulting in a remarkable 51.5 % increase in efficiency and a substantial 228 % increase in distillate yield.
Enhancing freshwater production with a high-performance solar interface evaporator and in low-vacuum environment: A solar-driven low-vacuum interfacial distillation system
2023, Desalination
Solar-driven interfacial evaporation technology has immense potential in addressing the global challenge of freshwater scarcity. Currently, most solar interface evaporators have complex and costly manufacturing processes, hindering practical applications. Additionally, in many solar distillation systems, the evaporation and condensation processes occur within the same space. This causes sunlight to be scattered or absorbed by the water droplets on the transparent surface, thereby reducing the solar energy reaching the evaporator, the high internal humidity ratio further hinders water evaporation. Therefore, we developed a cost-effective polyvinyl alcohol/carbon black hydrogel (PCH) with a simple fabrication process. PCH achieves an evaporation rate of 1.54 kg m⁻² h⁻¹ and an energy conversion efficiency as high as 90.5 % under 1 sun (1 kW m⁻²). Furthermore, we have introduced a novel solar-driven low-vacuum interfacial distillation system (SLIDS) that separates the evaporation and condensation processes into distinct spaces and employs the principle of low pressure to enhance water evaporation. The condensate yield rate of the SLIDS was 1.46 kg m⁻² h⁻¹, which is 2.2 times higher than traditional system under 1 sun. This increase in the condensate yield rate by 41.6 % was achieved through the introduction of low-pressure conditions.
Methods used to improve solar still performance with generated turbulence for water desalination- detailed review
2023, Results in Engineering
In everyday living, the need for fresh water is crucial. The most pressing problem in developing nations is the ongoing lack of access to clean water. In many ways, the solar still is a great source of freshwater for both drinking and cultivation, it is one of the most popular essential and technically practicable sun energy uses. This study lists studies on solar stills with different methods of creating turbulence to enhance solar stills productivity in an effort to offer a full picture of current scientific advancements. These methods serve to induce turbulence in basin water and break the thermal boundary layer between still surface and water to enhance the evaporation. The use of turbulence devices converts free evaporation to forced evaporation, which increases the evaporation rate. Spraying unit, air bubbles, vibratory harmonic effect, stirring turbulence, rotating parts and ultrasonic fogger were used to create water turbulence. Diverse results (productivity and enhancement) demonstrated shown the importance of spraying unit (5400 mL/m²/day −56%), air bubbles (5490 mL/m²/day–21.96%), stirring turbulence (5400 mL/m²/day −39.49%), and ultrasonic fogger (6270 mL/m²/day– 83.87%). The benefit of this review is that it will allow for a systematic understanding of the role and influence of each thermal-methods on the daily productivity rate using various turbulence techniques.
Enhancing a solar still's performance by preheating the feed water and employing phase-change material
2023, Alexandria Engineering Journal
Drinkable water is becoming increasingly scarce due to increased industrialization and population development, which has forced researchers to come up with new ways to meet this need. Drinkable water can be produced using solar stills, but their output isn't particularly high. A modified solar still (MSS) and a conventional still (CSS) have both been used in an experimental study. The MSS has undergone testing using spiral copper water heating coils (MSS), internal reflector (MSS-IR), and Nano-phase change material (MSS-IR-PCM). The performance of MSS and CSS was tested in three different sets of experiments under identical meteorological conditions. The rise in productivity/thermal efficiency for MSS, MSS-IR, and MSS-IR-PCM are 66%/44%, 81%/46.2% and 115%/51.3%, respectively. The distillate production was increased to be 81% higher than CSS's by adding internal reflector to the MSS's back wall. Therefore, the incorporation of the internal reflector boosted the MSS output by about 15%. It was shown that MSS-IR-PCM is 115% more productive overall than CSS. As a result, utilizing PCM boosted MSS-IR productivity by roughly 34% when compared to the situation without PCM. Economic analysis was also considered. For the CSS and MSS-IR-PCM, the cost of the distilled freshwater is 0.03 and 0.0235 $/L, respectively.
Solar thermal waste heat energy recovery in solar distillation systems by using thermoelectric generators
2023, Engineering Science and Technology, an International Journal
In this study, the novel use of thermoelectric technology in solar desalination systems was experimentally investigated. The new type of solar still with the thermoelectric generator (CSS-TEG) was proposed to improve the water output and efficiency. CSS-TEG’s performance was assessed and compared with the conventional one (CSS). Economic and enviro-economic assessments, as well as energy and exergy analyses, were conducted based on the system parameters and measurements taken from the designed experimental setup. The new system’s daily energy and exergy efficiency were obtained as 40.34% and 2.462% respectively, whereas, with the CSS one, they were 35.55% and 2.403%, respectively. The daily production of distilled water from the CSS and the newly designed solar still with TEG was measured at 4313 g/m² and 4893 g/m², respectively. In general, the estimated production cost of 1 kg of freshwater from CSS was 0.055$, and CSS-TEG was 0.081$. Additionally, referring to the exergo-economic parameter, CSS and CSS-TEG mitigated an average of 0.596 and 0.6132 tons of CO₂ respectively.
Experimental performance evaluation of a novel design solar desalination device equipped with air stones
2022, Desalination
The increasing need for a freshwater supply has led researchers to suggest improved solar stills as one solution to the problem of water shortages. For this purpose, to cover the maintenance and performance gap in this field, three enhancement techniques, including rigid PVC boxes, sliding absorber plates, and air stones at different water depths, are tested in the solar stills. The highest daily production and efficiency for rigid PVC insulation boxes (case A) were about 23 % and 7.6 % more than the conventional solar still and more proper than many previous studies. The maximum daily production and efficiency of an improved solar still with air stones (case B) with water depths of 2 have been 4192 mL/m² and 42 %, respectively. The daily production of case B with a water depth of 2 cm and air stone lengths of 0.1 m, 0.3 m, and 0.55 m was 22.6 %, 27.6 %, and 34.7 % higher than the conventional one. By comparing the cost per litre (CPL) of the conventional and improved solar stills, it was observed that the CPL in cases A and B was 0.013 $/L and 0.016 $/L, which was about 16 % lower and 11 % higher than a conventional still, respectively.

View all citing articles on Scopus

¹: Currently Prince Sattam bin Abdulaziz University, Saudi Arabia.

View full text

Published by Elsevier Ltd.

Improving the productivity of solar still by using water fan and wind turbine

Highlights

Abstract

Introduction

Section snippets

Experimental setup

Experimental procedures

Experimental uncertainty analysis

Experimental results and discussion

Conclusions

Desalination

Energy

Sol. Energy

Desalination

Appl. Energy

Sol. Energy

Renew. Sustain. Energy Rev.

Desalination

Sol. Energy

Energy Conserv. Manage.

Desalination

Renew. Sustain. Energy Rev.

Renew. Sustain. Energy Rev.

Sol. Energy