Evaluating energy consumption of air gap membrane distillation for seawater desalination at pilot scale level

Duong, Hung Cong; Cooper, Paul; Nelemans, Bart; Cath, Tzahi Y.; Nghiem, Long D.

doi:10.1016/j.seppur.2016.04.014

Cited by 167 publications

(69 citation statements)

References 36 publications

(57 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Duong et al report a low value of around 0.3 kWh/m 3 for the specific electrical energy consumption [63]. Nevertheless, even for a pump power consumption of 1-2 kWh/m 3 -product, the relative contribution of pump energy consumption is much lower than that of capital cost and thermal energy.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Energy efficiency of membrane distillation up to high salinity: Evaluating critical system size and optimal membrane thickness

et al. 2018

View full text Add to dashboard Cite

This study presents a comprehensive analytical framework to design efficient single-stage membrane distillation (MD) systems for the desalination of feed streams up to high salinity. MD performance is quantified in terms of energy efficiency (represented as a gained output ratio, or GOR) and vapor flux, both of which together affect the specific cost of pure water production. Irrespective of the feed salinity, permeate or conductive gap MD (P/CGMD) performs better than direct contact MD (DCMD) when the heat transfer resistance of the gap (in P/CGMD) is lower than that of the external heat exchanger in DCMD. Air gap MD's (AGMD) better performance relative to the other configurations at high salinity and large system area can be explained in terms of its thicker 'effective membrane', which includes the air-gap region. CGMD and DCMD employing a thick membrane are also resilient to high salinity, similar to AGMD, while not being susceptible to the gap flooding that can harm AGMD's performance. A method is described to simultaneously determine the cost-optimal membrane thickness and system size as a function of the ratio of specific costs of heat energy and module area. At low salinity and small system size, GOR rises and flux declines with an increase in membrane area. For salty feed solutions, there exists a critical system size beyond which GOR also begins to decline. Since both GOR and flux are lower, no economic rationale favors operation above this critical size, irrespective of the costs of thermal energy and system area. A closed-form analytical expression for this critical system area is derived as a function of the feed salinity and two dimensionless ratios of heat transfer resistances within the MD module.Keywords: membrane distillation, high salinity, energy efficiency, system size, optimal membrane thickness * Corresponding author: lienhard@mit.

show abstract

Section: Discussionmentioning

confidence: 99%

“…Potential for flooding in AGMD The present numerical model is compared against results from the pilot scale MD module reported in [63].…”

Section: Discussionmentioning

confidence: 99%

Energy efficiency of membrane distillation up to high salinity: Evaluating critical system size and optimal membrane thickness

et al. 2018

View full text Add to dashboard Cite

show abstract

“…Thus, the optimal operation strategy in terms of energy efficiency as well as distillate production should be characterized for each MD module. Several performance indices can be adopted to evaluate thermal efficiency, being the Specific Thermal Energy Consumption (STEC), which is widely employed in the literature to 190 evaluate the energy consumption of MD systems (Duong et al, 2016;Guillén-Burrieza et al, 2012;Zaragoza et al, 2014;Ruiz-Aguirre et al, 2017a,b), the one used in this work:…”

Section: Optimal Operation Of the MD Modulementioning

confidence: 99%

Optimal operation of a Solar Membrane Distillation pilot plant via Nonlinear Model Predictive Control

Gil

Roca

Ruiz-Aguirre

et al. 2018

Computers & Chemical Engineering

View full text Add to dashboard Cite

Solar Membrane Distillation (SMD) is an under-investigation desalination process suitable for developing self-sufficient small scale applications. The use of solar energy considerably reduces the operating costs, however, its intermittent nature requires a non-stationary optimal operation that can be achieved by means of advanced control strategies. In this paper, a hierarchical control system composed by two layers is used for optimizing the operation of a SMD pilot plant, in terms of thermal efficiency, distillate production and cost savings. The upper layer is formed by a Nonlinear Model Predictive Control (NMPC) scheme, that allows us to obtain the optimal operation by optimizing the solar energy use. The lower layer includes a direct control system, in charge of attaining the variable references provided by the upper layer. Simulation and experimental tests are included and commented in order to demonstrate the benefits of the developed control system.

show abstract

“…MD designs resemble counter-current heat exchangers with a liquid-repelling membrane and channel on the hot fluid side [10][11][12], where heat transfer across the membrane ideally occurs mostly by evaporation and condensation of pure water [13][14][15][16][17]. Of the MD configurations developed, air gap MD (AGMD) is one of the most common and has been shown to have the greatest potential for high thermal efficiency under more saline conditions [6,[18][19][20][21][22][23][24][25].…”

Section: Introductionmentioning

confidence: 99%

Comprehensive condensation flow regimes in air gap membrane distillation: Visualization and energy efficiency

Warsinger

Swaminathan

Morales

et al. 2018

Journal of Membrane Science

View full text Add to dashboard Cite

The thermal performance of air gap membrane distillation (AGMD) desalination is dominated by heat and mass transfer across the air gap between the membrane and the condensing surface. However, little is known about the impact of condensate flow patterns in some design variations of the air gap. In this study, air gap membrane distillation experiments were performed at various inlet temperatures, varying module inclination angle, condensing surface hydrophobicity, and gap spacer design to identify the effect of each on the permeate production rate and thermal efficiency of the system. Energy efficiency modeling was performed as well. Additionally, this study is one of the first with enhanced visualization of flow patterns within the air gap itself, by using a transparent, high thermal conductivity sapphire plate as the condenser surface. System-level numerical modeling is used to further understand the impact of these flow regimes on overall energy efficiency, including flux and GOR. A brief review of membrane distillation condensation regimes is provided as well. For tilting the AGMD flat-plate module, permeate flux was barely influenced except at extreme positive angles (>80ᵒ), and moderate negative angles (<-30ᵒ), where condensate fell onto the membrane surface. The surface with the hydrophobic coating (for dropwise condensation) was shown to have better droplet shedding (with very small nearly spherical droplets) and fewer droplets bridging the gap. Superhydrophobic surfaces (for jumping droplet condensation) were similar, with much smaller droplet sizes. Meanwhile, the hydrophilic surface for small gap sizes (< 3 mm) often had pinned regions of water around the hydrophilic surface and plastic spacer. Overall, the various results imply that the common assumption of a laminar condensate film poorly describes the flow patterns in real systems for all tilt angles and most spacer designs. Real system performance is likely to be between that of pure AGMD and permeate gap membrane distillation (PGMD) variants, and modeling shows that better condensing in air gaps may improve system energy efficiency significantly, with strong relative advantages at high salinity.

show abstract

Evaluating energy consumption of air gap membrane distillation for seawater desalination at pilot scale level

Cited by 167 publications

References 36 publications

Energy efficiency of membrane distillation up to high salinity: Evaluating critical system size and optimal membrane thickness

Energy efficiency of membrane distillation up to high salinity: Evaluating critical system size and optimal membrane thickness

Optimal operation of a Solar Membrane Distillation pilot plant via Nonlinear Model Predictive Control

Comprehensive condensation flow regimes in air gap membrane distillation: Visualization and energy efficiency

Contact Info

Product

Resources

About