Water distillation in a combined solar still and solar pond system: Iraq as a case study

  • Osamah A. H. Al-Musawi
  • Anees A. Khadom
  • Fakhru’l-Razi B. Ahmadun
  • Dayang R. Biak
Original Paper


A hybrid system of mini solar pond combined with single-slope still was used to increase the production of the distilled water from R.O. rejections and to harness the generated thermal energy from this mini solar pond. This study is focused on the solar distillation coupled with solar pond technique as a renewable energy method in Iraq and as a case study for desalinization with no negative ecological effects. This eco-friendly system has the potential to maintain the water sources environment by reusing R.O. rejections. Daily efficiency and recovered water were studied for 12 working hours per day, and the value of mass flux was 12 kg/m2 day of the R.O. effluent that used as a feed to the system. The experiment and theoretical calculations were carried out during 50 days in May, June, and July 2015. The vital climatic conditions of experiment were collected throughout the study period. Experimental tests showed the temperature profiles of mini solar pond and the maximum temperature of 62–64 °C at the LCZ of the mini solar pond with an efficiency of ~ 10%. Moreover, the productivity of distilled water obtained from the solar still in the tested system was ~ 2.5 l with an efficiency of ~ 30%. The comparison of the productivity was 0.63 kg on the 20th of May, 1.0521 kg on the 16th of June, and 1.1427 kg on the 9th of July by operating the solar still alone, with solar pond, and sunshade over the still in the combination system, respectively.


Solar pond Solar still Energy Reverse osmosis Water recovery 


\( H_{{0(X_{2} )}} \)

The input net radiation flux from the (NCZ) which move into lower (heat store) layer (LCZ), (W/m2)

\( H_{{0(X_{1} )}} \)

The input net radiation flux from the (UCZ) which transfer into intermediate layer (NCZ), (W/m2)

\( H_{{X_{2} }} \)

The amount radiation flux at depth x2, (W/m2)

\( H_{{X_{1} }} \)

The amount radiation flux at depth x1, (W/m2)


Emissivity of water surface (dimensionless)


Humid heat capacity of air (J/kg °C)


Surface area of wall sides of the pond (m2)

\( \emptyset_{\text{r}} \)

Refraction angle at the pond’s surface, which is measured in degrees

\( \emptyset_{\text{i}} \)

Incident angle at direct radiation to horizontal plane with zenith angle (normal), measured in degrees

\( H_{0} \)

Monthly average insolation incident on horizontal surface from the sun


Latent heat of vaporization of water (J/kg)


Partial pressure for the water surface temperature in UCZ (Pa)


Partial pressure of water vapor at the ambient air (Pa)


Atmospheric pressure (pa)


The transient heat by conduction \( (Q_{\text{cond }} 1) \) out of the upper zone (UCZ) into the surrounding of solar pond


The transient heat by conduction \( (Q_{{{\text{cond}} }} 2) \) to the zone from the next layer into the preceding layer in solar pond (from NCZ to UCZ)


The transient heat by conduction \( (Q_{{{\text{cond}} }} 3) \) to the zone from the next layer into the preceding layer in solar pond (from LCZ to NCZ)


The thermal energy (heat) input


The net collected thermal energy (heat) at each layer in the solar pond


Thermal energy (heat) output from solar pond, it is also heat loss


The fallen net amount of solar irradiation which captivated by solar pond at (UCZ)


Heat loss into the surroundings from the (UCZ)


Heat loss through sides of the pond


Temperature at the lower convective zone (°C)


Temperature at the non-convective zone (°C)


Temperature at the upper convective zone (°C)


Ambient temperature (°C)


The sky temperature (°C)


Wall heat transfer coefficient (w/m2 °C)


Thickness of NCZ layer (m)


Thickness of LCZ layer (m)


Convection heat transfer coefficient (w/m2 °C)


Heat lost as a result of convection to surrounding (w/m2)


Heat lost due to evaporation (w/m2)


Heat lost radiation in the upper zone to surrounding (w/m2)


Specific humidity in kg water vapor per kg dry air in the mixture


The lower convective zone or the heat storage zone


The intermediate convective zone or the non-convective zone


The upper convective zone of the solar pond


Thickness of the UCZ layer (m)

\( H_{{X_{3} }} \)

The amount radiation flux at depth x3 (W/m2)


Thermal conductivity of water


The day of the year (1 ≤ N ≤ 365)


Average monthly wind speeds (m/s)


Local time (h)


Latitude angle


Declination angle


Stefan–Boltzmann’s constant (W/m2 k4)

\( \omega \)

Hour angle, which is defined as an angular gauge of the time measured from noon according to local time h


Specific fresh water production (kg/m2 h)


The corresponding mass transfer coefficient


Vapor pressures of water inside basin still at basin temperature (Tw), measured in (Pa)


Vapor pressures of water at cover temperature (Tg), measured in (Pa)


Convective coefficient for the still


Temperature average water, K


Temperature glass covering, K


Proficiency of solar still


Proficiency of solar pond


Solar still area (m2)


Compliance with ethical standards

Conflict of interest

On behalf of all authors, the corresponding author states that there is no conflict of interest.

Supplementary material

41207_2018_57_MOESM1_ESM.docx (381 kb)
Supplementary material 1 (DOCX 380 kb)


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Copyright information

© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  • Osamah A. H. Al-Musawi
    • 1
  • Anees A. Khadom
    • 2
  • Fakhru’l-Razi B. Ahmadun
    • 1
  • Dayang R. Biak
    • 1
  1. 1.Department of Chemical and Environment Engineering, Faculty of EngineeringUniversity Putra MalaysiaSerdangMalaysia
  2. 2.Department of Chemical Engineering, College of EngineeringUniversity of DiyalaBaqubaIraq

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