Experimental characterization of a multi-effect distillation system coupled to a flat plate solar collector field: Empirical correlations

Abstract In the last three decades, developments in desalination plants have been focused on the minimization of its energetic consumption and cost. Advancements include emerging technologies that make use of low grade thermal energy, like Multi-Effect Distillation (MED). The energy optimization of MED systems and their coupling with solar thermal technologies have been deeply investigated by the Solar Desalination Unit of the Plataforma Solar de Almeria (PSA) through a solar desalination test facility consisting of a MED plant coupled to a static solar field. Recently, the previous solar field composed of compound parabolic concentrators (CPC) has been replaced by a new one with large-aperture flat plate collectors (FPC). In this work, an experimental characterization of the solar MED system under off-design conditions is presented and discussed. The efficiency of the FPCs’ solar field at several temperature levels for different climate conditions has been determined. Also, the influence of the variation of key parameters by which the MED plant is controlled (the inlet hot water flow rate ( m hot ) and temperature ( T hot ) , the feed water flow rate ( m f ) and the condenser vapor temperature ( T c )) on the freshwater production and performance ratio (PR), were analyzed with an experimental campaign of 82 experiments. The results obtained were used to fit polynomial expressions, validated statistically, that predict the distillate yield and the PR for different operation strategies. The experimental characterization of the desalination plant revealed that the rise in the T c has the highest impact in the thermal efficiency of the MED unit, and the rise in the m f has the greatest influence on the distillation production. Moreover, from the analysis of the coupling of the MED plant with the solar field it was found that the thermal storage has an autonomy of up to 6 h when the MED works with hot water at 65 °C, which allows the plant to continue the operation even in transient periods (presence of clouds). Also, from a theoretical annual study for the solar MED system, it was found that the annual solar fraction ranges from 30.7% to 42.4%, which leads to an annual distillate production between 6701 m3 and 11,314 m3, respectively.

[1]  Ali M. El-Nashar,et al.  Simulation of the steady-state operation of a multi-effect stack seawater distillation plant , 1995 .

[2]  Lourdes García-Rodríguez,et al.  Experimental analysis of a multi-effect distillation unit operated out of nominal conditions , 2012 .

[3]  Diego-César Alarcón-Padilla,et al.  Experimental parametric analysis of a solar pilot-scale multi-effect distillation plant , 2016 .

[4]  Hong-Jin Joo,et al.  Performance evaluation of multi-effect distiller for optimized solar thermal desalination , 2013 .

[5]  Shengqiang Shen,et al.  Thermodynamic performance of a low temperature multi-effect distillation experimental unit with horizontal-tube falling film evaporation , 2011 .

[6]  J. Paulo. Davim,et al.  Design of Experiments in Production Engineering , 2016 .

[7]  Wolfgang Wagner,et al.  International Equations for the Saturation Properties of Ordinary Water Substance , 1987 .

[8]  Christopher D. Lloyd,et al.  Spatial Data Analysis: An Introduction for GIS users , 2010 .

[9]  Soteris A. Kalogirou,et al.  Solar thermal collectors and applications , 2004 .

[10]  H. Ettouney,et al.  Multiple-effect evaporation desalination systems. thermal analysis , 1999 .

[11]  Robert Gould,et al.  A Modern Approach to Regression with R , 2010 .

[12]  Ali M. El-Nashar.  Predicting part load performance of small MED evaporators : a simple simulation program and its experimental verification , 2000 .

[13]  Hans Müller-Steinhagen,et al.  Collector test method under quasi dynamic conditions according to the European Standard EN 12975-2 , 2004 .

[14]  Guillermo Zaragoza,et al.  Characterisation of the coupling of multi-effect distillation plants to concentrating solar power plants , 2015 .

[15]  Douglas C. Montgomery,et al.  Applied Statistics and Probability for Engineers, Third edition , 1994 .

[16]  Julián Blanco,et al.  The Aquasol System: Solar collector field efficiency and solar-only mode performance , 2008 .

[18]  Wolfgang Wagner,et al.  International equations for the saturation properties of ordinary water substance. Revised according to the international temperature scale of 1990 , 1993 .

[19]  Dongfeng Zhao,et al.  Theoretical analyses of thermal and economical aspects of multi-effect distillation desalination dealing with high-salinity wastewater , 2011 .

[20]  Aliakbar Akbarzadeh,et al.  Low‐temperature solar–thermal multi‐effect evaporation desalination systems , 2010 .

[21]  Viviane Renaudin,et al.  Experimental study of a three-effect plate evaporator: seawater tests in La Spezia , 2005 .

[22]  S. Bingulac,et al.  Steady‐State Analysis of the Multiple Effect Evaporation Desalination Process , 1998 .

[23]  John G. Georgiadis,et al.  Experimental evaluation of a multiple-effect distillation unit in low seawater flow conditions , 2015 .

[24]  Guillermo Zaragoza,et al.  Steady state model for multi-effect distillation case study: Plataforma Solar de Almería MED pilot plant , 2014 .

[25]  Shi Li,et al.  A lab-scale MED dealing with salinity wastewater: the study of optimal operation schemes and parameters , 2016 .