Synergistic Impact of Magnets and Fins in Solar Desalination: Energetic, Exergetic, Economic, and Environmental Analysis

Abstract

This study investigates the effectiveness of combining magnets with parabolic and truncated fins in enhancing the distillation process of solar stills. The integration of magnets accelerated evaporation rates, while the fins increased the heat absorption area, resulting in improved output, vis-à-vis traditional solar stills. A comparative assessment revealed that the parabolic fin solar still (PFS) with magnets outperformed the truncated fin solar still (TCFS), producing 20%, 15%, and 16% more distillate at three different depths (1, 2, and 3 cm). The superior performance of the PFS is attributed to the magnetism of the water and the fins’ more extensive surface area for heat absorption. Efficiency measurements at a water depth of 1 cm showed that the PFS achieved the maximum energy and exergy efficiencies at 30.49% and 8.85%, respectively, compared with TCFS’s 25.23% and 6.22%. Economically, the PFS setup proved more feasible, with a 20.9% lower cost per liter of distilled water than TCFS. Additionally, the environmental impact assessment indicated a significant reduction in CO₂ emissions, potentially generating revenues of approximately USD 1242.32 through carbon credits. These results reflect a considerable margin to enhance the efficiency of solar desalination through well-planned adjustments, which bodes well for the future of optimized solar distillation systems from an economic and environmental perspective.

1. Introduction

Water is a primary necessity for every living being. For every creature, water is required daily. Even though there is abundant water on Earth, 97% of it is found in the seas, which is useless saline water, and just 3% of the water is fit to drink. Only 1% of drinkable water is accessible to humans and comes in the form of lakes and rivers; the remaining 2% is found beneath the surface of the earth [1]. The human population is rising every day. Hence, there is an increasing demand for effective water purification methods to meet the growing needs. Due to the available quantity of saline water, desalination is one of the most important ways to accomplish this among the available options [2]. There are multiple ways to desalinate water. Solar desalination is an eco-friendly and inexpensive way of purifying water with the aid of a renewable energy source. Solar stills are used for this process, and they are inexpensive devices that can even be deployed in distant locations. They also require minimal maintenance [3]. This device produces pure water by heating, evaporating, and performing condensation of brackish water in an enclosed area [4,5]. Switching to solar-powered distillation will save a large amount of money because solar energy is free, and producing stills is comparatively inexpensive [6].

Solar stills are categorized into active and passive, based on the heat source used for water evaporation. This heat source could be either directly from the sun or through external aids. In passive solar stills, the water directly absorbs solar energy, causing it to evaporate. The vapor then condenses and is collected as freshwater [7]. Active solar desalination systems use external energy sources to enhance efficiency. These systems often use pumps, fans, heaters, or other devices to escalate the evaporation and condensation rates [8].

Scholars have utilized various techniques to boost the efficiency of solar desalination. Like Mohamed et al., the use of porous absorber materials led to an increase in exergy efficiency of 65%, 104%, and 123% compared with a conventional solar still (CSS) at 1 cm, 1.5 cm, and 2 cm, respectively [9]. The cumulative distillate yield increased by 34.57%, and the daily efficiency increased by 34.83% when sandbags were used as the energy storage material [10]. Panchal [11] demonstrates the use of evacuated tubes in a double-effect solar still to desalinate water in remote locations, with a minimum water cost of just 0.033 USD/L and a payback period as short as 45 days when selling water at 0.30 USD/L. Kabeel et al. [12] investigated the usage of composite heat storage materials in solar stills, finding a 37.55% increase in productivity compared with using latent heat energy storage alone. Abu-Hijileh and Rababa’h [13] used sponge cubes in saline water to enhance evaporation rates, demonstrating that distillate productivity increased by 18–273%. Natarajan et al. [14] enhanced solar efficiency using sawdust, rice husk, and rice straws. The mixture of sawdust and rice straws increased freshwater output by 62.88% compared with a conventional solar still (CSS). Arjunan et al. [15] tested various heat storage materials (HSMs) in a single-slope solar still and found that black granite gravel was the most efficient, achieving the highest overall efficiency of 43%, outperforming pebbles and blue metal stones.

A promising modification to conventional stills is fins, which enhance the heat transfer rate, thereby increasing the evaporation rate. To enhance thermal performance and the yield of drinking water, Sathyamurthy et al. [16] emphasized the necessity of fins being added to the flat absorber plate. Fins increased the overall yield by 46.85%. Similarly, Khalili et al. found that efficiency and yield grew by 44.8 percent due to the addition of fins. The length and spacing of the fins control the shading effect. Enhanced results were obtained as fins can improve heat transfer conditions and increase absorption area in a distiller, improving performance [17]. The experimental double-basin solar still with evacuated tubes that used easily accessible materials and solid fins yielded a 25% better output of distillate than the setup without fins [18]. When fins and sponges were combined into a single-basin solar still, the output of the distilled water was greater than before by 45.5% and 15.3%, respectively, over the standard basin-type still [19]. Using aluminum fins in solar stills improved productivity by enhancing heat transfer, achieving a daily output of 660 mL/0.25 m²/day under Tamil Nadu climate conditions [20]. Rupinder et al. [21] investigated an innovative fin theory for thermal storage in high-temperature solar cooling, finding that decreasing the height of fins improved heat absorption and reduced melting time by 30% in a solar absorption chiller. Hardik et al. [22] Rabhi et al. used mild steel square hollow fins on an absorber plate to enhance solar still productivity. They found that a 10 mm water depth yielded the highest efficiency, with a production of 0.9672 kg/m²-day. The thin water layer facilitated better heat transfer from the absorber plate, increasing desalinated water output [23]. Incorporating pin fins and an external condenser into a solar still significantly enhanced water production efficiency, achieving a combined output gain of 41.95% over traditional designs. Pin fins, composed of 3 mm diameter steel and spanning 60 mm in depth, improved hourly efficiency by 12.9% when used with an external condenser.

In an experiment conducted at Hyderabad, Kaviti et al. [24] added aluminum truncated conic fins to a standard solar still and discovered that the energy efficiency had increased by 29.61% compared with a conventional solar still. Similarly, Kaviti et al. [25] experimented using parabolic fins composed of aluminum and attained an output of 1250 mL per day. The previous results show that using fins has increased the productivity by almost 58% and 52% for truncated fin solar stills (TCFSs) and parabolic fin solar stills, respectively, compared with CSSs [26].

Research has been conducted by scientists to study the effect of magnetic fields on the rate of evaporation in solar distillers. There is a noticeable increase in the rate of evaporation as an outcome of the interaction between the hydrogen bonds in water and the magnetic field [27]. Water evaporates eleven times quicker in a magnetic field than it does in a non-magnetic setting. This phenomenon occurs because of the disruption that the magnetic field causes at the gas/liquid interface, which leads to prolonged evaporation after distillation [28]. Applying magnetic fields increases the performance of conventional solar distillation by enhancing water generation and heat transfer rates. A magnetic field added to water was shown to improve the output by 43% [29]. Using graphite plate fins and magnets (GPF-MSSs) in the solar still has improved the performance of a single inclined solar distillation device. Under identical climate conditions, the GPF-MSS has been compared with a standard solar distillation device (CSS). Compared with CSSs, GPF-MSSs demonstrated higher output, energy effectiveness, and energy efficiency [30]. This study compares three distinct varieties of solar stills: the standard stepped solar still (CSSS), the magnetic stepped solar still (MSSS), and the magnet charcoal stepped solar still (MCSSS). In comparison with the CSSS, the MCSSS greatly surpassed the others, increasing yield output and heat transfer rates by 91.70% and 104.54%, respectively [31]. Magnets are used to modify a single-slope solar still. The exergy efficiency achieved by using magnets is 33% higher when compared with the CSS [1].

The literature shows numerous methods to enhance the efficiency of solar stills. Based on the findings, further research is needed to explore the synergistic effect of magnets and fins. Solar stills with fins work more efficiently because they have a larger surface area for absorbing heat. Magnets can improve heat circulation within the basin, resulting in more consistent heating. The researchers studied fins and magnets independently. Fins and magnets, in a novel way, can dramatically increase evaporation rates. The combination of the fins’ ability to absorb more sunlight and the magnets’ ability to alter the motion of water molecules makes for a possibly faster rate of evaporation. This experimental work aims to increase the distillate output of a double-slope solar still by combining magnets and fins. Truncated and parabolic fins, coupled with magnets, are used in two double-slope solar stills. Experiments at 1 cm, 2 cm, and 3 cm depths are conducted in two double-slope solar stills simultaneously. The economic viability, energy efficiency, and environmental impact of double-slope sun stills are the three primary indices utilized in evaluating these solar stills’ effectiveness.

2. Methodology

2.1. Experimental Setup

This experimental arrangement uses two identical dual-slope solar stills, as shown in Figure 1c,d. The basin was composed of mild steel and measured 100 × 50 cm. Black paint was applied to the basin’s surface to maximize heat absorption. Each basin was contained in a wooden box measuring with a thickness of 10 cm to avoid heat losses from the still to its atmosphere; a thermocol was placed into the space between the still and the wooden box. The top surface of the dual slope is covered with a glass cover. The properties of a glass cover are crucial for improving the performance. The optical properties of the glass were 90%, 5%, and 5% for transmissivity, absorptivity, and reflectivity, respectively. K-type thermocouples were used to track temperatures inside the basin, in the water, and on the inside and outside surfaces of the solar still’s glass to facilitate temperature monitoring. In addition, two instruments were used to detect solar radiation and wind velocity: a pyranometer and an anemometer.

Two modifications were implemented to compare performance. The first modification involved the integration of fins to increase the surface area, while the second modification incorporated magnets to enhance the evaporation rate. The magnets utilized in both modifications had the following measurements: 1.5 cm thickness, 3 cm inner diameter, and 7 cm outer diameter. The fins have these magnets firmly attached to them, as shown in Figure 1. The ferrite ring magnets are employed in this project. These ring-shaped magnets are built from iron oxide-based magnetic ceramics. They are primarily formed from iron oxide; thus, they cannot corrode further. They have a high coercivity, making them difficult to demagnetize. Magnetization is anisotropic, resulting in increased coercivity and magnetic strength. As previously stated, ferrite magnets are formed from rust (iron oxide). Consequently, they do not corrode further. Ferrite magnets maintain their performance at high temperatures and can be used up to 250 degrees Celsius. Magnetic field strength and magnetic field orientation affects the breaking of hydrogen bonds in water. Two different fin types, truncated and parabolic, were used. Figure 1a,b provide a clear view of the fins and magnets utilized in this experiment. The length of the truncated fins was 5 cm, the base diameter was 2 cm, and the slant height was 5.5 cm. Parabolic fins’ proportions were as follows: their base diameter was 2 cm, and their height was 5.0 cm, with the stills covered with glass panels at a 17° angle, corresponding to Hyderabad’s latitude.

2.2. Experimental Procedure

The trials were carried out in May at the VNR Vignana Jyothi Institute of Engineering and Technology in Hyderabad, India (17.3850° N latitude, 78.4867° E longitude). As shown in Figure 1c,d, fin-equipped magnets were strategically placed to improve the still production. Stills are positioned in such a way that one slope is facing toward the east and the other is facing toward the west. Around the base of the solar still, the magnets were distributed uniformly over the parabolic fins. To provide contrast, another solar still had the exact same measurements but with magnets and truncated fins.

The parabolic fin solar still (PFS) and the truncated fin solar still (TCFS) had 1 cm of water added to them the day before the experiment. The experiments were conducted for three days for one depth of water. Likewise, experiments were conducted for a 2 cm depth of water and a 3 cm depth of water. The best reading among the three days was considered for evaluation of the performance of the solar stills. The water became magnetized as there were magnets present. By efficiently breaking the hydrogen bonds between the water molecules, these ferrous magnets were used to magnetize the water inside the still, increasing the evaporation rate. The studies were carried out from 9:30 a.m. to 5:00 p.m. using parabolic and truncated fins at one, two, and three cm water depths. The ambient temperature, water temperature, solar still’s glass, and basin were all measured using temperature sensors, especially K-type thermocouples. In addition, pyranometers and anemometers were used to measure sun radiation and wind speed, respectively.

Table 1. Range of operation and precision of the utilized instruments.

S.no.	Device	Precision	Range
1	Pyranometer	±5 W/m2	0–2000 W/m2
2	Thermocouple	±1 °C	100–500 °C
3	Anemometer	±0.5 m/s	0–30 m/s

provides specifics on the operational parameters and accuracy of the equipment listed.

The still efficiency, distillate output, and heat transfer coefficients (HTCs) were computed by taking readings every hour. After the data were carefully arranged and evaluated, a comparison of the efficiency of the PFS and TCFS was performed.

2.3. Uncertainty Analysis

The uncertainty analysis is all about the difference between the actual value and the estimated value, which is another term that is commonly used to refer to an error. Ambiguity errors can be broken down into two categories. Type A errors can be quantified by the utilization of mathematical and repetitive research, which are examples of random errors. It is possible to determine type B errors by using the calibration report of the instruments or the data book, both of which are examples of systematic errors. Inferences regarding the normal uncertainty can be drawn from the mathematical theorem that is shown beneath.

$$\mathrm{u}=\mathrm{a}/\sqrt{3}$$

where u = standard uncertainty

a = measuring device accuracy

The experimental inquiry focusses on the measuring process’s inherent instrumental uncertainties. Daily fresh water productivity has a margin of error of ±1.5%, driven by instrumental uncertainties. This element of the analysis emphasizes the importance of employing accurate apparatus and measurement techniques in order to obtain reliable data. The research faces additional challenges in measuring solar radiation and system temperatures, as shown in Table 1, in addition to the previously noted difficulties. Because of their impact on solar still performance, these uncertainties are essential study variables.

3. Performance Indices

Three main indices are used to evaluate the effectiveness of solar desalination: economic viability, energy efficiency, and environmental impact. Economic analysis assesses the costs, including startup, maintenance, and operating expenses, while energy efficiency gauges the system’s capacity to transform solar energy into potable water. Environmental analysis examines carbon emissions, water use, and ecological impacts. Together, these indices offer a thorough assessment of the system’s functionality.

3.1. Energy Analysis

By examining the energy conversion and thermal dynamics, energy analysis is crucial in maximizing the efficiency of solar stills. By studying variables like distillate production, absorber area, latent heat of vaporization, and solar radiation intensity, experts may pinpoint inefficiencies and enhance the architecture of systems. The energy efficiency, $\sum E_i=\sum E_o$, is determined by this analysis using the first law of thermodynamics (Equation (1)) as a basis:

$$\sum E_i=\sum E_o$$

(1)

Thermal efficiency is calculated using Equation (2) [32,33]:

$${\eta }_{energy}={\displaystyle \frac{\sum m_w\times h_{fg}}{ A_b\int I_s\left(t\right)dt}}\times 100$$

(2)

where the latent heat of vaporization ($h_{fg}$) is measured in joules per kilogram (J/kg), the absorber area of the SS ($A_b$) is measured in square meters (m²), the distillate output ($m_w$) is expressed in liters per square meter (L/m²), and the intensity of solar radiation ($I_s$) is measured in watts per square meter (W/m²).

3.2. Exergy Analysis

By identifying irreversibilities and losses, the exergy analysis evaluates the thermodynamic efficiency and capacity for productive activity in solar desalination systems. It applies the second rule of thermodynamics to determine the exergy efficiency [34]:

$${\eta }_{exergy}={\displaystyle \frac{E_{ex\left(o\right)}}{E_{ex\left(i\right)}}}$$

(3)

$$\sum E_{ex\left(i\right)}=I_s\times A_b\times \left[1-{\displaystyle \frac{4}{3}}\left({\displaystyle \frac{T_{amb}}{T_{sun}}}\right)+{\displaystyle \frac{1}{3}}{\left({\displaystyle \frac{T_{amb}}{T_{sun}}}\right)}^4\right]$$

(4)

$$\sum E_{ex\left(o\right)}=m_w\times h_{fg}\times \left[1-\left({\displaystyle \frac{T_{amb}}{T_w}}\right)\right]\times {\displaystyle \frac{1}{3600}}$$

(5)

The variables denote the input and output exergy in kWh/year, $E_{ex\left(i\right)}$ and $E_{ex\left(o\right)}$, respectively. $T_{amb}$ and $T_{sun}$ are Kelvin values for the surrounding air and sun, respectively. The absorber area of the SS ($A_b$) is measured in square meters (m²), the latent heat of vaporization ($h_{fg}$) in joules per kilogram (J/kg), and the intensity of solar radiation ($I_s$) in watts per square meter (W/m²).

3.3. Economic Analysis

The economic analysis evaluates the costs, including materials, labor, operation, and maintenance, when assessing the financial viability of solar desalination systems. Metrics like the Capital Recovery Factor (CRF) and Total Yearly Cost (C_YTC) are calculated to help assess the overall economic viability. From these calculations, the cost of producing potable water per liter (C_FWPL) is obtained, which offers insights into the system’s financial sustainability, $M_y$ [35].

Let C be the initial capital needed to build the solar still, with an interest rate of 12% per year (i) for a 15-year useful life (n). Consequently, the following formulas are used to calculate the Capital Recovery Factor (CRF) and Yearly Fixed Cost (C_YFC):

$$C_{FWPL}={\displaystyle \frac{C_{YTC}}{M_y}}$$

(6)

$$M_y=m_d\times N_d$$

(7)

• m_y = distill water produced annually (L/m²)
• m_d = mean daily fresh water (L/m²)
• N_d = number of sunny days in a year

$$C_{YTC}=C_{YFC}+C_{YMC}-C_{YSV}$$

(8)

$$C_{YFC}=C\times CRF$$

(9)

$${\mathrm{Y}\mathrm{e}\mathrm{a}\mathrm{r}\mathrm{l}\mathrm{y} \mathrm{m}\mathrm{a}\mathrm{i}\mathrm{n}\mathrm{t}\mathrm{e}\mathrm{n}\mathrm{a}\mathrm{n}\mathrm{c}\mathrm{e} \mathrm{c}\mathrm{o}\mathrm{s}\mathrm{t}\mathrm{s}(C}_{YMC})=0.10\times C_{YFC}$$

(10)

$$\mathrm{C}\mathrm{a}\mathrm{p}\mathrm{i}\mathrm{t}\mathrm{a}\mathrm{l} \mathrm{R}\mathrm{e}\mathrm{c}\mathrm{o}\mathrm{v}\mathrm{e}\mathrm{r}\mathrm{y} \mathrm{f}\mathrm{a}\mathrm{c}\mathrm{t}\mathrm{o}\mathrm{r}\left(CRF\right)={\displaystyle \frac{i\times {\left(i+1\right)}^n}{{\left(i+1\right)}^n-1}}$$

(11)

$$\mathrm{S}\mathrm{a}\mathrm{l}\mathrm{v}\mathrm{a}\mathrm{g}\mathrm{e} \mathrm{C}\mathrm{o}\mathrm{s}\mathrm{t} \mathrm{C}\mathrm{a}\mathrm{l}\mathrm{c}\mathrm{u}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}\left(C_{YSV}\right)=0.2\times C\times SFP$$

(12)

where SFP is derived as:

$$SFP={\displaystyle \frac{i}{{\left(i+1\right)}^n-1}}$$

(13)

$${\mathrm{A}\mathrm{n}\mathrm{n}\mathrm{u}\mathrm{a}\mathrm{l} \mathrm{m}\mathrm{a}\mathrm{r}\mathrm{k}\mathrm{e}\mathrm{t} \mathrm{c}\mathrm{o}\mathrm{s}\mathrm{t} \mathrm{o}\mathrm{f} \mathrm{f}\mathrm{r}\mathrm{e}\mathrm{s}\mathrm{h}\mathrm{w}\mathrm{a}\mathrm{t}\mathrm{e}\mathrm{r} (C}_{YMW})=M_y\times freshwater price per \mathrm{k}\mathrm{g}$$

(14)

$$Yearly earning\left(C_y\right)=C_{YMW}-C_{YMC}$$

(15)

$$\mathrm{P}\mathrm{a}\mathrm{y}\mathrm{b}\mathrm{a}\mathrm{c}\mathrm{k} \mathrm{p}\mathrm{e}\mathrm{r}\mathrm{i}\mathrm{o}\mathrm{d} \mathrm{o}\mathrm{f} \mathrm{t}\mathrm{h}\mathrm{e} \mathrm{s}\mathrm{o}\mathrm{l}\mathrm{a}\mathrm{r} \mathrm{s}\mathrm{t}\mathrm{i}\mathrm{l}\mathrm{l}\left(N_{pb}\right)={\displaystyle \frac{C}{C_y}}\times 365$$

(16)

3.4. Environmental Analysis

The environmental analysis assesses the sustainability of solar desalination systems by measuring CO₂ emissions and their mitigation [36].

$$\mathrm{C}{\mathrm{O}}_2 \mathrm{E}\mathrm{m}\mathrm{i}\mathrm{s}\mathrm{s}\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{s}\left({\mathsf{\Psi }}_{C{O}_2}\right)={\displaystyle \frac{E_{im}\times 1.58}{n}}$$

(17)

where (E_im) represents the embodied energy of the distiller, essentially the total energy consumed over its lifecycle, and (n) is the lifespan of the distiller in years. The multiplier 1.58 reflects the average CO₂ emission in kg per kWh of energy produced from fossil fuels in India, accounting for transmission, distribution, and appliance losses.

$$\mathrm{C}{\mathrm{O}}_2 \mathrm{E}\mathrm{m}\mathrm{i}\mathrm{s}\mathrm{s}\mathrm{i}\mathrm{o}\mathrm{n} \mathrm{M}\mathrm{i}\mathrm{t}\mathrm{i}\mathrm{g}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}\left({\xi }_{C{O}_2}\right)={\displaystyle \frac{\left[\left(E_{out}\times n\right)-E_{in}\right]\times 1.58}{1000}}$$

(18)

Here, (E_out) is the yearly energy output from the distiller, and (n) is the lifespan. This equation helps quantify the net reduction in CO₂ emissions due to the operation of the solar still, considering the CO₂ cost of its embodied energy.

$$\mathrm{C}\mathrm{a}\mathrm{r}\mathrm{b}\mathrm{o}\mathrm{b} \mathrm{C}\mathrm{r}\mathrm{e}\mathrm{d}\mathrm{i}\mathrm{t} \mathrm{E}\mathrm{a}\mathrm{r}\mathrm{n}\mathrm{e}\mathrm{d}\left(CCE\right)={\displaystyle \frac{\left[\left(E_{out}\times n\right)-E_{in}\right]\times 1.58\times z}{1000}}$$

(19)

This equation factors in the same variables as CO₂ emission mitigation but includes a multiplier (z) that could represent the market value per ton of CO₂ or a similar metric.

This analysis demonstrates the environmental benefits and potential carbon credits earned by the system, emphasizing its role in promoting sustainability.

Energy, exergy, economic, and environmental analyses evaluate the performance of solar desalination systems. Collectively, these analyses highlight the system’s efficiency, financial viability, and environmental sustainability, providing a comprehensive assessment for further development and adoption.

4. Results and Discussion

The experiment was conducted from 9:30 a.m. to 5:00 p.m. under Hyderabad’s climatic conditions. Two modifications were tested, one featuring truncated fins and the other with parabolic fins, with magnets being the common modification. Solar intensity variation graphs were plotted for the respective days of the experiment, as shown in Figure 2. The solar intensity was initially recorded as low at the commencement of the experiment, gradually increasing after that. The intensity peaked at 1 p.m., followed by a gradual decrease in intensity levels. When looking at the change in the three different water depth conditions, the same pattern emerged. After 5 p.m., the sun’s intensity dropped significantly. Therefore, studies were carried out daily till 5 p.m.

In solar stills, the basin, water, and condensing glass temperatures are critical parameters determining the output. With increasing solar intensity, the temperatures of the stills gradually rose from morning until noon, reaching their peak at 1 p.m. Subsequently, the temperatures gradually decreased towards the end of the day. Given that the volume of water in the still at a 1 cm depth is the least compared with 2 cm and 3 cm, higher temperatures were observed at a 1 cm depth. Notably, the temperature difference between the water and condensing glass significantly affects the output, with the phenomenon being more pronounced in the parabolic fin solar still (PFS) than in the truncated fin solar still (TCFS). Consequently, the PFS exhibited higher temperature differences than the TCFS, particularly at the 1 cm depth. Figure 3, Figure 4 and Figure 5 depict that, for all depths, the temperatures in the PFS were higher than those in the TCFS, reflecting similarly in the output. A surface tension force of around 72 N/m is present in water when it is at normal temperature, making it one of the liquids with the highest surface tension. The majority of the earlier research that had been conducted on the effect of magnetic fields on the surface tension property of water was analyzed, and it was found that increasing the magnetic field resulted in a decrease in the surface tension. The researchers [37] found that a magnetic field brought about a decrease in surface tension. In their study, Guo and colleagues [38] found that the magnetic field had a substantial impact on lowering the surface tension of salty water, which led to enhancement of the evaporation. So, in addition to temperature, the magnetic field plays a vital role in improving evaporation.

Graphs illustrating the variations of cumulative and hourly yields of the two modifications are presented in Figure 6 and Figure 7. Initially, a low amount of distillate formed due to low temperatures. However, compared with previous experiments, these modifications yielded favorable results, owing to the combined effect of magnets and fins. Fins increase the heat absorption surface area, while magnets magnetize the water. The performance of the present solar still with fins and magnets is compared with that of the empty solar still (without fins and magnets). The results are compared with the work carried out by the same author [24]. It is found that without magnets and fins, the cumulative distillates are 795 mL, 505 mL, and 430 mL at 1 cm, 2 cm, and 3 cm depth water, respectively. In the present work, the maximum cumulative distillate is 1305 mL, 1275 mL, and 825 mL at 1 cm, 2 cm, and 3 cm, respectively. The cumulative yield of the PFS with magnets was 20% higher than that of the TCFS with magnets at a 1 cm depth. Similarly, at 2 cm and 3 cm depths, the PFS produced 15% and 16% more distillate than the TCFS.

The evaluation of various solar still configurations under different water depths (1 cm, 2 cm, and 3 cm) revealed distinct energy efficiency metrics, emphasizing the significant influence of design and working parameters on performance. Specifically, for the parabolic and truncated configurations (PFS and TCFS), notable variations in energy efficiency percentages were observed. The energy efficiency of the PFS and TCFS are depicted in Figure 8. These values are compared with previous work conducted by the same author [26]. There was an improvement in the efficiencies due to the magnetic effect in addition to the fins. At a water depth of 1 cm, PFS demonstrated an efficiency of 30.49%, surpassing TCFS, which recorded an efficiency of 25.23%. Similarly, at 2 cm depth, PFS maintained a relatively high efficiency of 30.15%, while TCFS exhibited a slightly lower efficiency of 26.13%. However, PFS’s effectiveness dropped to 19.88% at a depth of 3 cm, and TCFS’s efficiency decreased even more to 16.98%. These results demonstrate how the depth of the water affects solar still energy efficiency, with shallower depths typically translating into higher efficiencies.

Exergy efficiency was measured for a variety of solar still designs at three distinct water depths (1, 2, and 3 cm) and is depicted in Figure 9. The results showed notable variability in exergy efficiency, indicating the impact of design and operating characteristics on performance. The maximum exergy efficiencies for the parabolic (PFS) and truncated (TCFS) shapes were noted at a water depth of 1 cm, where PFS achieved 8.85% and TCFS achieved 6.22%. Subsequently, PFS showed an efficiency of 7.50% at the 2 cm depth, but TCFS showed 5.83%. PFS had an efficiency of 5.00% and TCFS had 3.68% at the lowest depth of 3 cm. These results highlight the intricate interactions between design, operating parameters, and water depth and highlight the significance of taking into account both energy and exergy efficiency measures for optimizing solar still setups for sustainable desalination processes. The energy efficiency of the parabolic solar still varied between 8.85% and 5.00%, while the truncated solar still showed a range of 6.22% to 3.68%. Energy and exergy efficiencies behaved in a comparable manner.

Generally, PFS exhibits lower CPL values, as shown in the

Table 2. Economic analysis to assess the CPL.

Parameters	USD ($)
Total Cost (P)	133.68
Capital Recovery Factor (CRF)	0.1468
Fixed Annual Cost (FAC)	19.62
Salvage Value (S)	26.74
Sinking Fund Factor (SFF)	0.0268
Annual Salvage Value (ASV)	0.72
Annual Maintenance Operational Cost (AMC)	2.94
AC (Annual Cost)	21.85
M (Average Annual Productivity) in Liters per m2	783
CPL (Cost of distilled water Per Liter)	0.028

and

Table 3. Variation of CPL for different water depths of the PFS and TCFS.

Experimental Conditions at Different Depths of Water	Cost per Liter (USD)
PFS at 1 cm	0.028
TCFS at 1 cm	0.034
PFS at 2 cm	0.029
TCFS at 2 cm	0.033
PFS at 3 cm	0.044
TCFS at 3 cm	0.052

, compared with TCFS, suggesting low costs per liter of distilled water produced. Additionally, deeper water depths result in increased CPL values due to low evaporation rates. Specifically, CPL values for PFS range from 0.028 to 0.044 USD/L, while TCFS CPL values range from 0.034 to 0.052 USD/L across the tested depths. These values are compared with previous work of the same author [26]. The cost per liter is decreased by 7.15%. These findings showcase the economic implications of solar desalination technologies and can help in the decision regarding their implementation and optimization strategies.

As shown in

Table 4. Embodied energy of double solar still and its components.

Material	Mass (kg)	Energy Density (kWh/kg)	Product (kWh)
Wood	11.12	16	177.92
Thermocol	1.5	0.15	0.225
Aluminum	3.7	8.61	31.857
Glass	4.55	2.5	11.375
Pipe	0.184	21	3.864
Black paint	0.2	25	5
Magnets	1.2	10	12
Total	22.454	83.26	242.241

, the system’s embodied energy is 242.241 units when the mass of each distiller component is multiplied by its energy density. Considering the distiller’s total energy input over its 15-year lifespan, the calculated CO₂ emissions was 25.516 tons.

The environmental impact of solar distillers extends into the realm of carbon trading, with the CO₂ emission mitigation translating into carbon credits. Calculated by multiplying the mitigated CO₂ quantity by the current CO₂ trading cost, the project showcases an impressive potential for carbon credit earnings. For the given period, the earnings are estimated at around USD 1234.98, as shown in the

Table 5. Environmental parameters of the double-slope solar still.

Environment	Value
CO2 emission per year (kgs)	25.51
CO2 mitigation (tons)	20.85
Carbon credit ($)	1234.98

, highlighting the enviro-economic viability of solar distillation systems.

5. Conclusions and Future Scope

5.1. Conclusions

Adding magnets and parabolic fins considerably enhanced the distillation process of solar stills, with the PFS surpassing the TCFS. This study draws the following conclusions.

• The PFS produced 20%, 15%, and 16% more distillate at water depths of 1 cm, 2 cm, and 3 cm, respectively, than the TCFS, owing to the combined effects of magnetism and the larger heat absorption area.
• At a water depth of 1 cm, the PFS achieved the highest efficiency in energy and exergy, with 30.49% and 8.85%, respectively, while the TCFS achieved 25.23% and 6.22%. These measures demonstrate how water depth and design significantly influence solar still performance.
• The PFS setup proved more economically viable, with a 20.9% lower cost per liter of distilled water compared with the TCFS.
• The PFS showed a considerable reduction in CO₂ emissions, with a possible revenue creation of USD 1234.98 through carbon credits, emphasizing its environmental benefits.
• The environmental impact assessment showed a significant reduction in CO₂ emissions, which might result in potential revenues of around USD 1234.98 through the purchase of carbon credits. This demonstrates the solar distillation systems’ economic and environmental potential.
• This study only considers water depths of 1 cm, 2 cm, and 3 cm. This range might not cover all possible operational scenarios. Testing additional depths could provide a more comprehensive understanding of the system’s performance.

5.2. Future Scope

Given the conclusions, the future scope for enhancing the performance and sustainability of solar stills with parabolic fins (PFSs) and magnetism could be explored in some exciting directions.

The use of nanomaterials or special coatings that could further enhance heat absorption and reduce heat losses could be investigated, improving the overall efficiency of the distillation process.

While the study highlights the benefits of magnetism, it might not thoroughly explore potential negative impacts or side effects. Further investigation into how magnetism influences long-term performance and material durability would be valuable.