Evaporation suppression and solar energy collection in a salt-gradient solar pond

Abstract Evaporation represents a significant challenge to the successful operation of solar ponds. In this work, the suppression of evaporative losses from a salt-gradient solar pond was investigated in the laboratory. Two floating element designs (floating discs and floating hemispheres) and a continuous cover were tested; all three covers/elements were non-opaque, which is unique from previous studies of evaporation suppression in ponds or pools where increasing temperature and heat content are not desired. It was found that floating discs were the most effective element; full (88%) coverage of the solar pond with the floating discs decreases the evaporation rate from 4.8 to 2.5 mm/day (47% decrease), increases the highest achieved temperature from 34 °C to 43 °C (26% increase), and increases heat content from 179 to 220 MJ (22% increase). As a result of reduced evaporative losses at the surface, the amount of heat lost to the atmosphere is also reduced, which results in lower conductive losses from the NCZ and the LCZ and hence, increased temperatures in the NCZ and LCZ. The magnitude of evaporation reduction observed in this work is important as it may enable solar pond operation in locations with limited water supply for replenishment. The increase in heat content allows more heat to be withdrawn from the pond for use in external applications, which significantly improves the thermal efficiencies of solar ponds.

[1]  D. Weeks,et al.  What happens when a solar pond boils , 1981 .

[2]  S. Aboul-Enein,et al.  History of the solar ponds: A review study , 2011 .

[3]  N. C. Van de Giesen,et al.  Measuring heat balance residual at lake surface using Distributed Temperature Sensing , 2013 .

[4]  M. A. Garmana,et al.  Sizing and thermal study of salinity gradient solar ponds connecting with the MED desalination unit , 2008 .

[5]  S. Samdarshi,et al.  Combined effect of bottom reflectivity and water turbidity on steady state thermal efficiency of salt gradient solar pond , 2004 .

[6]  J. P. Schwartze,et al.  The evaporation of water into air of different humidities and the inversion temperature phenomenon , 2000 .

[7]  Scott W. Tyler,et al.  A fully coupled, transient double-diffusive convective model for salt-gradient solar ponds , 2010 .

[8]  Mark B. Hausner,et al.  Assessment of a vertical high-resolution distributed-temperature-sensing system in a shallow thermohaline environment , 2011 .

[9]  A. Akbarzadeh,et al.  A laboratory experimental study of mixing the solar pond gradient zone , 2011 .

[10]  Aliakbar Akbarzadeh,et al.  Solar energy storage by salinity gradient solar pond: Pilot plant construction and gradient control , 2011 .

[11]  Sergio Saul Solis.  Water desalination by membrane distillation coupled with a solar pond , 1999 .

[12]  Suarez Poch,et al.  Salt-gradient solar ponds for renewable energy, desalination and reclamation of terminal lakes , 2010 .

[13]  S. Aboul-Enein,et al.  Experimental testing of a shallow solar pond with continuous heat extraction , 2004 .

[14]  J.L.A. Francey,et al.  Low-cost solar heating of community pools using pool covers , 1980 .

[15]  Herbert D. Hein,et al.  Solar and Waste Heat Desalination by Membrane Distillation , 2000 .

[16]  Jah Brown.  The Potential for Reducing Open Water Evaporation Losses: A Review , 1988 .

[17]  Scott W. Tyler,et al.  Temperature evolution of an experimental salt-gradient solar pond , 2010 .

[18]  S. Assouline,et al.  Evaporation from partially covered water surfaces , 2009 .

[19]  John R. Hull,et al.  Salinity Gradient Solar Ponds , 1988 .

[20]  Keith R. Cooley,et al.  Energy Relationships in the Design of Floating Covers for Evaporation Reduction , 1970 .

[21]  W. Marion,et al.  A new solar radiation data manual for flat‐plate and concentrating collectors , 1994 .

[22]  Ari Rabl,et al.  Solar ponds for space heating , 1975 .

[23]  R. Ghys.  [Infrared thermography]. , 1970, Les cahiers du nursing.

[24]  Jamal Seyed-Yagoobi,et al.  Effect of water turbidity on thermal performance of a salt-gradient solar pond , 1995 .

[25]  M. M. González-Real,et al.  Efficiency of shading materials in reducing evaporation from free water surfaces , 2006 .

[26]  S. Assouline,et al.  Evaporation suppression from water reservoirs: Efficiency considerations of partial covers , 2011 .

[27]  Francisco Suárez,et al.  A theoretical study of a direct contact membrane distillation system coupled to a salt-gradient solar pond for terminal lakes reclamation. , 2010, Water research.

[28]  Jamal Seyed-Yagoobi,et al.  Effects of water turbidity and salt concentration levels on penetration of solar radiation under water , 1994 .

[29]  B. Henderson-Sellers.  Calculating the Surface Energy Balance for Lake and Reservoir Modeling: A Review (Paper 6R0209) , 1986 .

[30]  Andrew Swift,et al.  Advancements in Salinity Gradient Solar Pond Technology Based on Sixteen Years of Operational Experience , 2004 .

[31]  I Burston.  Conservation of water from open storages by minimising evaporation , 2002 .

[32]  John G. Harris,et al.  Scattering of an ultrasonic beam from a curved interface , 1989 .