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Investigation of design configurations and effective parameters on productivity enhancement of vertical diffusion solar stills

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Abstract

Solar distillation is one of the most promising solutions to provide freshwater in limited-population communities with high availability of solar radiation and poor accessibility to safe and clean water. Until now, several types of solar stills have been developed including wick-type stills, stepped stills, inclined and double-slope stills, tubular stills, and pyramid stills. Among them, vertical diffusion solar stills (VDSSs) have been newly developed, offering several priorities over conventional types. This study presents a detailed review of VDSSs by investigating effective parameters and employed techniques to enhance the productivity of these solar stills. For this purpose, design factors along with operational parameters including heat energy input, type of carrier gas, basin water depth, and feedwater flow rate are studied and profoundly discussed. Additionally, enhancement techniques including feedwater preheating, shape modifications, waste heat utilization, and integration with reflectors are studied. According to the literature, the productivity of VDSSs is enhanced by a reduction of the diffusion gap and a decrease in the number of effects. In some studies, the use of waste heat and electricity as energy inputs has led to higher productivity in comparison with solar energy. Moreover, considering design factors, a modified configuration can increase productivity by 44%. In this review, the environmental and economic aspects of VDSSs are also discussed. Numerical analyses have predicted that a passive VDSS with a multiple-chamber configuration and 13.85% exergy efficiency could cut 67.93 tons (average) of CO2 emission during its 20-year lifetime, while its financial payback time is 0.63 years. The studies have also demonstrated that an optimized VDSS can reach the water price of 6.1 USD/m3 which makes this technology more attractive than other low-capacity stills from economic aspects.

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Notes

  1. SCP is defined as the ratio of heat demanded by the still to the solar energy received by the system.

Abbreviations

A col :

Collector area (m2)

A eva :

Evaporation area (m2)

A HW :

Heating section area (m2)

CCF:

CO2 conversion factor (kg/kW h)

C col :

Capital cost of the solar collector ($/m2)

C m :

Capital cost of the miscellaneous components

COP:

Coefficient of performance

C p :

Specific heat of water (J/kg K)

CPL:

Cost of distillate per liter (USD/L)

CS:

Carbon saving (kg)

C T :

Total annual cost per glass area (USD/m2)

C VS :

Capital cost of the vertical still (USD/m2)

EP:

Energy produced by the solar system (kWh)

EPBT:

Energy payback time (year)

Exeva :

Exergy of evaporation

Exin :

Input exergy

Exout :

Output exergy

Exsun :

Exergy of sun

F :

Sinking fund factor

f cr :

Capital recovery factor

g 1 :

First glass cover

g 2 :

Second glass cover

GOR:

Gain output ratio

G S :

Total solar incident (W/m2)

h c :

Convective heat transfer coefficient (W/m2 K)

h CH :

Convective heat transfer coefficient of the fluid inside the heating unit (W/m2k)

h fg :

Latent heat of condensation (J/kg)

H V :

Water latent heat of evaporation (J/kg)

\(I_{t}\) :

Solar radiation intensity (W/m2)

IR:

Interest rate

LHV :

Annual average latent heat of evaporation (J/kg)

LT:

Life time (yr)

M a :

The molecular weight of air (kg/kmol)

M col :

Annual operation and maintenance cost of the solar collector (%C)

mC p :

Heat capacity (J/k)

m d( i ) :

Distillate yield ith each cell (kg)

m d, daily :

Daily productivity of the still (kg/d)

m e :

Evaporation rate (kg/s)

m p :

Water production rate (kg/h)

m f :

Feedwater flow rate (kg/s)

m f(P) :

Mass flow rate of saline water on the plate (kg/s)

M m :

Annual operation and maintenance cost of the miscellaneous components (%C)

M V :

Molecular weight of water vapor

M VS :

Annual operation and maintenance cost of the vertical still (%C)

n :

Number of effects/cells

P i :

\(i{\text{th}}\) Evaporating/condensing plate

PBP:

Payback period (year)

PPD:

Productivity per USD invested (kg/USD)

PR:

Performance ratio

Pr:

Prandtl number

P s :

Saturated water vapor pressure corresponding to the plat temperature (Pa)

P t :

Total pressure (Pa)

P T (P i ) :

Partial vapor pressure in the temperature of the ith plate (Pa)

Q c :

Convection heat (W)

Q col :

Total energy produced by the solar collector (W)

Q d :

Conduction heat (W)

Q e :

Heat flux of evaporation–condensation (W)

Q f :

Heat energy used for heating the saline water (W)

Q in :

Heat flow supply into the system (W)

Q L :

Total loss of energy (W)

Q r :

Radiation heat transfer (W)

S col :

Salvage value of the solar collector (%C)

SCP:

Solar energy coefficient of performance

S m :

Salvage value of the miscellaneous components (%C)

S p :

Selling price of product water (USD/L)

SVS :

Salvage value of the vertical still (%C)

T :

Temperature (K)

T sun :

Temperature of the sun (6000 K)

T W :

Water temperature (°C)

T amb :

Ambient temperature (K)

T f :

Feedwater temperature (K)

T fc :

Fluid temperature inside the heating unit (K)

T mean :

Mean temperature between evaporating and condensing surfaces (K)

u w :

Wind speed (m/s)

β g :

Coefficient of glass volume expansion (1/K)

δ g :

Glazing gap (m)

δ g –P :

Distance between the glass and the plate (m)

δ H :

Thickness of the heating unit (m)

δ P :

Gap between the plates (m)

η col :

Thermal efficiency of the solar collector

\(\eta_{{{\text{exergy}}}}\) :

Exergy efficiency

\(\eta_{{{\text{th}}}}\) :

Thermal efficiency of solar still

λ a :

Air thermal conductivity (W/m K)

λ f :

Thermal conductivity of the fluid (W/m Ksss)

λ h :

Thermal conductivity of humid air (W/m K)

λ HW :

Thermal conductivity of the heating wall (W/m K)

\(A\) :

Aperture area (m2)

\(D\) :

Diffusivity of water vapor in the air (m2/s)

\({\text{EP}}\) :

Amount of energy produced annually (kWh)

\({\text{Gr}}\) :

Grashof number

\(R\) :

Gas constant of water (J/kg K)

\(g\) :

Gravitational acceleration (m2/s)

\(l\) :

Characteristic length (m)

\(v\) :

Kinematic viscosity of air (m2/s)

\(\alpha\) :

Absorbance

\(\varepsilon\) :

Emissivity

\(\sigma\) :

Stefan–Boltzmann constant

\(\tau\) :

Transmittance

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Acknowledgements

This project was supported by Ministry of Science, Research and Technology of Islamic Republic of Iran and Department of Science and Technology of India as one of the selected proposals announced by India–Iran Joint call in 2018. The authors would also like to acknowledge Laxmikant D. Jathar because of his valuable advisory and contribution to this study.

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Authors and Affiliations

  1. MAHTEP Group, Dipartimento Energia “Galileo Ferraris” (DENERG), Politecnico Di Torino, 10129, Turin, Italy

    H. Ebadi

  2. Biosystems Engineering Department, Faculty of Agriculture, Tarbiat Modares University (T.M.U.), P.O. Box: 14115-111, Tehran, Iran

    S. Gorjian

  3. Adhoc Faculty, Department of Mechanical Engineering, National Institute of Technology Andhra Pradesh, Tadepalligudem, Andhra Pradesh, India

    H. Sharon

  4. Plataforma Solar de Almería (CIEMAT), Carretera Senés, km 4, 04200, Tabernas, Almería, Spain

    J. Blanco-Galvez

  5. Department of Mechanical Engineering, Delhi Technological University, Delhi, 110 042, India

    A. Kumar

Authors
  1. H. Ebadi
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  2. S. Gorjian
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  3. H. Sharon
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  4. J. Blanco-Galvez
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  5. A. Kumar
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Contributions

HE was involved in the conceptualization; methodology; resources; optional; and writing—original draft. SG contributed to the writing—original draft; conceptualization; methodology; supervision; and funding acquisition. HS contributed to the writing—original draft; review and editing. JB-G contributed to the conceptualization; writing—review and editing. AK was involved in the visualization; writing—review and editing.

Corresponding author

Correspondence to S. Gorjian.

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Conflict of interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. The authors declare the following financial interests/personal relationships which may be considered as potential competing interests.

Additional information

Editorial responsibility: Samareh Mirkia.

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Ebadi, H., Gorjian, S., Sharon, H. et al. Investigation of design configurations and effective parameters on productivity enhancement of vertical diffusion solar stills. Int. J. Environ. Sci. Technol. 19, 6889–6924 (2022). https://doi.org/10.1007/s13762-021-03823-z

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  • DOI: https://doi.org/10.1007/s13762-021-03823-z

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