**3. Results**

We have used single-basin, double-slope solar distillation still for the study and hence the results have signified the need for multi-slope and multi-basin for improved performance. Observations were made for water temperature (**T <sup>w</sup>**), top condensing surface temperature (**T <sup>g</sup>**), and distillate output in mL. The temperature of water and glass was measured using two k-type thermocouples. The vapor temperature (**Tv**) was taken as the average water temperature and glass temperature.

$$\mathbf{T\_v = (T\_w + T\_g)/2} \tag{5}$$

#### **3.1 Solar distillation readings at various heights**

**Tables 1** and **2** describes the variation of water temperature recorded from 8:30 am until 5:30 pm in 9 hours, each with different heights of water—5 and 7 cm respectively. Water and condensing surface temperature are averaged and recorded in a separate column, which is correlated with distillate collected, **Figures 6** and **7** show variation of temperatures **Tw**, **Tg**, and **Tv** with increasing time in hours. As the day progresses till noon, the water temperature increases faster as compared to the condensate temperature due to exposure of the glass surface to the ambient atmosphere. Alteration in condensate and water temperature can be attributed to unstable climatic conditions. However, in all cases, the pattern followed by the hourly variation shows a constant rise and fall in all line plots (**Figure 8**).

It can be inferred from the above implications and **Figures 7** and **9** that the yield of distillate and the pattern of rising and falling of the curve is similar indicating no variation upon water depth change. The temperature of the condensing surface temperature is rising since morning till past noon and decreases after maxima. We can notice that the temperature variation of water basin coupled with PCM, as shown in **Figures 10** and **11** show similar and broader variation when compared to the curves of water in **Figure 8** and **9** [26, 27]. In the early hours of the day, the


**177**

**Figure 6.**

with an increase in hours.

*Water depth (d) = 0.07 m.*

*Experimental results without PCM.*

**Table 2.**

**3.2 Solar distillation using PCM**

*Hourly variation of temperature at water depth-1.*

*Water Desalination Using PCM to Store Solar Energy DOI: http://dx.doi.org/10.5772/intechopen.92597*

**S. No. Time (h) Tw (°C) Tg (°C) Tv (°C) Distillate (mL)** 9 30 27.8 29.95 0 10 35.3 32.8 36 5 11 41.2 37.6 41.4 9 12 48.7 43.8 48.15 109 13 51.3 47.4 53.5 201 14 54.8 50.8 54.7 330 15 52.3 45.3 52.55 292 16 48.7 39.1 47.2 215 17 45 34.2 41.65 157

inner glass temperature is close to that of water basin temperature. However, as the day, progresses the difference broadens because water can absorb some of the incident solar energy, whereas glass transmits most of the incident solar intensity. From figures about PCM phenol, we can see how phenol is retaining the solar energy, which decreases the slope of the line, which indicates declining temperature

Five kilograms of phenol was covering the 5-mm metal plate in the solar still basin while the experiment was being conducted, there was no mixing of water and PCM. The reading of these experiments was taken on an hourly basis till 5.00 pm and the cumulative distillate of the next 2 h was taken the next day at 9.00 am [8].

#### **Table 1.**

*Experimental results without PCM.*

*Water Desalination Using PCM to Store Solar Energy DOI: http://dx.doi.org/10.5772/intechopen.92597*


#### **Table 2.**

*Thermodynamics and Energy Engineering*

**3.1 Solar distillation readings at various heights**

ments at 0.05 and 0.07 m.

**3. Results**

recorded on an hourly basis; 5 kg of phenol as PCM was used to perform the experi-

We have used single-basin, double-slope solar distillation still for the study and hence the results have signified the need for multi-slope and multi-basin for improved performance. Observations were made for water temperature (**T <sup>w</sup>**), top condensing surface temperature (**T <sup>g</sup>**), and distillate output in mL. The temperature of water and glass was measured using two k-type thermocouples. The vapor temperature (**Tv**) was taken as the average water temperature and glass temperature.

**Tv = (Tw + Tg)/2** (5)

**Tables 1** and **2** describes the variation of water temperature recorded from 8:30 am until 5:30 pm in 9 hours, each with different heights of water—5 and 7 cm respectively. Water and condensing surface temperature are averaged and recorded in a separate column, which is correlated with distillate collected, **Figures 6** and **7** show variation of temperatures **Tw**, **Tg**, and **Tv** with increasing time in hours. As the day progresses till noon, the water temperature increases faster as compared to the condensate temperature due to exposure of the glass surface to the ambient atmosphere. Alteration in condensate and water temperature can be attributed to unstable climatic conditions. However, in all cases, the pattern followed by the

hourly variation shows a constant rise and fall in all line plots (**Figure 8**).

It can be inferred from the above implications and **Figures 7** and **9** that the yield of distillate and the pattern of rising and falling of the curve is similar indicating no variation upon water depth change. The temperature of the condensing surface temperature is rising since morning till past noon and decreases after maxima. We can notice that the temperature variation of water basin coupled with PCM, as shown in **Figures 10** and **11** show similar and broader variation when compared to the curves of water in **Figure 8** and **9** [26, 27]. In the early hours of the day, the

**S. No. Time (h) Tw (°C) Tg (°C) Tv (°C) Distillate (mL)** 9 30.3 28.3 30.01 0 10 39.3 32.7 36.3 23 11 45.6 37.2 421.4 106 12 52.2 44.1 47.15 204 13 54.3 52.7 52.5 287 14 56.1 53.3 55.7 348 15 55.2 48.3 53.55 273 16 49.1 45.7 48.2 217 17 48.7 38.5 42.65 149

**176**

**Table 1.**

*Water depth = 0.05 m.*

*Experimental results without PCM.*

*Experimental results without PCM.*

inner glass temperature is close to that of water basin temperature. However, as the day, progresses the difference broadens because water can absorb some of the incident solar energy, whereas glass transmits most of the incident solar intensity. From figures about PCM phenol, we can see how phenol is retaining the solar energy, which decreases the slope of the line, which indicates declining temperature with an increase in hours.

#### **3.2 Solar distillation using PCM**

Five kilograms of phenol was covering the 5-mm metal plate in the solar still basin while the experiment was being conducted, there was no mixing of water and PCM. The reading of these experiments was taken on an hourly basis till 5.00 pm and the cumulative distillate of the next 2 h was taken the next day at 9.00 am [8].

**Figure 7.** *Hourly variation of distillate yield at water depth-1.*

**Figure 8.** *Temperature variation at water depth-2.*

**179**

**Figure 10.**

**Figure 11.**

*Water Desalination Using PCM to Store Solar Energy DOI: http://dx.doi.org/10.5772/intechopen.92597*

*Hourly variation of distillate with phenol as PCM-1.*

*3.2.1 Solar distillation with phenol as PCM*

*Hourly variation of distillate yield with phenol as PCM-2.*

In **Figures 12** and **13**, it can be seen that the highest temperature attained by the water basin decreases with an increase in depth of water as in the case of PCM with and without PCM too (**Tables 1** and **2**). However, the standard deviation when Phenol as PCM is comparatively larger (**Tables 3** and **4**). In **Figures 10** and **11**, it can also be observed that for phenol, there has been a 4.1% drop in the maximum condensate surface temperature when the water depth has been increased from 5 cm to 7 cm. The decrease in water basin temperature with an increase in depth of water can be attributed to an increase in the volume of water. After sunset, due to a lack of solar radiation, the temperature of water in the basin decreases at a slower rate due to the use of stored heat energy from the PCM. The variation between water basin temperatures in two cases without phenol and with phenol at different water depths is subject to environmental conditions like fluctuation in solar radia-

tion, wind speed, ambient temperature, and spatial wind barriers.

**Figure 9.** *Hourly variation of distillate yield at water depth-2.*

*Water Desalination Using PCM to Store Solar Energy DOI: http://dx.doi.org/10.5772/intechopen.92597*

*Thermodynamics and Energy Engineering*

*Hourly variation of distillate yield at water depth-1.*

**178**

**Figure 9.**

**Figure 8.**

**Figure 7.**

*Temperature variation at water depth-2.*

*Hourly variation of distillate yield at water depth-2.*

**Figure 10.** *Hourly variation of distillate with phenol as PCM-1.*

**Figure 11.** *Hourly variation of distillate yield with phenol as PCM-2.*

#### *3.2.1 Solar distillation with phenol as PCM*

In **Figures 12** and **13**, it can be seen that the highest temperature attained by the water basin decreases with an increase in depth of water as in the case of PCM with and without PCM too (**Tables 1** and **2**). However, the standard deviation when Phenol as PCM is comparatively larger (**Tables 3** and **4**). In **Figures 10** and **11**, it can also be observed that for phenol, there has been a 4.1% drop in the maximum condensate surface temperature when the water depth has been increased from 5 cm to 7 cm. The decrease in water basin temperature with an increase in depth of water can be attributed to an increase in the volume of water. After sunset, due to a lack of solar radiation, the temperature of water in the basin decreases at a slower rate due to the use of stored heat energy from the PCM. The variation between water basin temperatures in two cases without phenol and with phenol at different water depths is subject to environmental conditions like fluctuation in solar radiation, wind speed, ambient temperature, and spatial wind barriers.

**Figure 12.** *Hourly variation of temperature with phenol-1.*

**Figure 13.** *Hourly variation of temperature with phenol-2.*


**181**

**4. Discussion**

**Table 4.**

*Water depth = 0.07 m.*

*Experimental results with phenol as PCM-2.*

given by:

*where,*

*C and n are constants. Also, the heat produced or*

*the power in kWh/m2*

*same, basin being assumed a black body.*

**4.1 Effect of the amount of water**

*.*

*Water Desalination Using PCM to Store Solar Energy DOI: http://dx.doi.org/10.5772/intechopen.92597*

The rationale behind conducting this study was to establish a clear relationship between incident solar radiation and the amount of fresh water produced. After developing the relationship and analyzing statistical information, we concur with the results from confirming data with two different depths [28, 29]. Then PCM was introduced, we chose phenol having attributions of economic availability and versatile properties. Phenol was also varied between two heights, and data was contrasted with that of water. Underlying factors were calculated as follows related to the heat and mass transfer [15].

**S. No. Time (h) Tw (°C) Tg (°C) Tv (°C) Distillate (mL)** 9 30.2 27.8 29 0 10 35.1 32.6 33.85 5 11 42.8 37.4 39.5 8 12 47.4 44 45.7 115 13 51.6 47.7 49.65 195 14 54.6 50.7 56.78 323 15 52.2 45.3 48.75 313 16 48.6 39.2 43.9 242 17 45 34.3 39.65 189

**Nu = hcw d/k = C (Gr Pr)<sup>n</sup>** (7)

*which is approximately (***Ta** *−* **Tw)** *as basin and water temperature is almost the* 

*Above gives a model to find Q and A for the required basin the fraction Q/A yields* 

For a fixed amount of water, the cumulative amount of freshwater produced had a steep rise as the sun goes higher until sunsets (**Table 5**). PCM, however, continue to heat the water even after the sunset giving the effect of evaporation a boost. We are assuming this as a unit operation under steady-state conditions because we are assuming that the feed water equals the sum of the rate of freshwater produced

from solar still is

*Qew* **= 0:01***6hcw***(***Pw –Pg*) (6)

*Q produced = mw\*L = UAᵹT … ᵹT = Ta − Tb,* (8)

We know from Dunkle [30], the hourly evaporation per m<sup>2</sup>

#### **Table 3.**

*Experimental results with phenol as PCM.*

*Water Desalination Using PCM to Store Solar Energy DOI: http://dx.doi.org/10.5772/intechopen.92597*


#### **Table 4.**

*Thermodynamics and Energy Engineering*

*Hourly variation of temperature with phenol-1.*

*Hourly variation of temperature with phenol-2.*

**S. No. Time (h) Tw (°C) Tg (°C) Tv (°C) Distillate (mL)** 9 31.8 29.5 30.35 0 10 38.6 33.5 36.05 28 11 43.8 38.4 41.1 95 12 51.6 45.6 48.6 193 13 54.7 52.1 53.4 286 14 57.1 52.5 54.8 370 15 55.4 49.6 52.5 297 16 49.5 45.1 47.3 268 17 45.2 39.8 42.5 1760 18 + 19 — — — 84

**Figure 12.**

**Figure 13.**

**180**

**Table 3.**

*Water depth = 0.05 m.*

*Experimental results with phenol as PCM.*

*Experimental results with phenol as PCM-2.*
