Energy performance enhancements of a 950 m3/d seawater reverse osmosis unit in Grand Cayman

Andrews, W.T.; Pergande, Wil; McTaggart, Gregory S.

doi:10.1016/s0011-9164(01)00150-3

Cited by 34 publications

(22 citation statements)

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“…Due to the fundamental nature of this interaction, this system has been the subject of considerable study [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] in two distinct, but related contexts. Due to the fundamental nature of this interaction, this system has been the subject of considerable study [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] in two distinct, but related contexts.…”

Section: Introductionmentioning

confidence: 99%

A general formula for the rate of resonant transfer of energy between two electric multipole moments of arbitrary order using molecular quantum electrodynamics

Salam

2005

The Journal of Chemical Physics

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A general expression is derived for the matrix element for the resonant transfer of energy between an initially excited donor species and an acceptor moiety in the ground state, with each entity possessing an electric multipole moment of arbitrary order. In the quantum electrodynamical framework employed, the coupling between the pair is mediated by the exchange of a single virtual photon. The probability amplitude found from second-order perturbation theory is a product of the electric moments located at each center and the resonant multipole-multipole interaction tensor. Using the Fermi golden rule, a general formula for the rate of energy transfer is obtained. As an illustration of the efficacy of the theory developed, rates of excitation energy exchange are calculated for systems interacting through dipole-quadrupole, dipole-octupole, quadrupole-quadrupole, and the familiar dipole-dipole coupling. For each of the cases examined, the near- and far-zone limits of the migration rate are calculated from the result valid for all donor-acceptor separations beyond wave function overlap. Expression of the octupole contribution to the transfer rate in terms of its irreducible components of weights 1 and 3 leads to new features. The octupole weight-1 term is found to contribute only when the interaction is retarded, while the dipole-octupole weight-1 contribution appears as a higher-order correction term to the dipole-dipole rate. Order of magnitude estimates are given for the contributions of dipole-quadrupole and dipole-octupole terms relative to the leading dipole-dipole rate for near-, intermediate-, and far-zone separations to further understand the role played by higher multipole moments in the transfer of excitation and the mechanism dominating the process.

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Section: Introductionmentioning

confidence: 99%

A general formula for the rate of resonant transfer of energy between two electric multipole moments of arbitrary order using molecular quantum electrodynamics

Salam

2005

The Journal of Chemical Physics

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“…55 In the long-range ͑pair separations exceeding optical wavelengths͒ a radiative, photon emission-capture process yielding the familiar inverse square law was thought to operate 56 -the latter mechanism attested by the reabsorption of photons in optically thick samples. 57 In a unified theory formulated by Andrews and co-workers in a series of works [58][59][60] the radiationless and radiative mechanisms were identified as the short-and longrange asymptotes of a single mechanism. Based on quantum electrodynamics ͑QED͒, and following ground-breaking quantum mechanical work by Avery 56 and Gomberoff and Power, 61 the unified theory establishes energy transfer as a process mediated by the propagation of virtual photons, optical quanta whose character becomes progressively ''real'' and energy conserving as their propagation distance ͑and hence lifetime͒ increases.…”

Section: Introductionmentioning

confidence: 99%

Resonance energy transfer: The unified theory revisited

Daniels

Jenkins

Andrews

2003

The Journal of Chemical Physics

147

134

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Resonance energy transfer ͑RET͒ is the principal mechanism for the intermolecular or intramolecular redistribution of electronic energy following molecular excitation. In terms of fundamental quantum interactions, the process is properly described in terms of a virtual photon transit between the pre-excited donor and a lower energy ͑usually ground-state͒ acceptor. The detailed quantum amplitude for RET is calculated by molecular quantum electrodynamical techniques with the observable, the transfer rate, derived via application of the Fermi golden rule. In the treatment reported here, recently devised state-sequence techniques and a novel calculational protocol is applied to RET and shown to circumvent problems associated with the usual method. The second-rank tensor describing virtual photon behavior evolves from a Green's function solution to the Helmholtz equation, and special functions are employed to realize the coupling tensor. The method is used to derive a new result for energy transfer systems sensitive to both magnetic-and electric-dipole transitions. The ensuing result is compared to that of pure electric-dipoleelectric-dipole coupling and is analyzed with regard to acceptable transfer separations. Systems are proposed where the electric-dipole-magnetic-dipole term is the leading contribution to the overall rate.

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“…However, several factors limit the efficiency of the mechanical to chemical potential energy conversion process, including hydraulic pump efficiency, recovery of pressure energy from waste water, uncontrolled mixing of saline and fresh water, and fluid flow resistance of the RO membrane. Along with the thermodynamic cost of solute concentration, these combine to make energy the largest component of the operating cost for seawater desalination facilities [34,1,36,26]. Recent advances in pressure recovery devices have placed the energy conversion efficiency of the mechanical components (hydraulic pump and pressure recovery) in the 85-89% range [42,1].…”

Section: Chapter 2 Thermodynamic Analysis Of Membrane Separations Promentioning

confidence: 99%

“…Along with the thermodynamic cost of solute concentration, these combine to make energy the largest component of the operating cost for seawater desalination facilities [34,1,36,26]. Recent advances in pressure recovery devices have placed the energy conversion efficiency of the mechanical components (hydraulic pump and pressure recovery) in the 85-89% range [42,1]. Taking example data from the Perth desalination plant [43], the pressure drop across the RO membrane accounts for 1.85 kWh/m 3 of the total desalination energy budget, while 0.4 kWh/m 3 is lost to mechanical efficiency, and a remaining 1.2 kWh/m 3 is used for pre/post treatment and transport throughout the facility.…”

Section: Chapter 2 Thermodynamic Analysis Of Membrane Separations Promentioning

confidence: 99%

“…In reality, the input pump is only 80-90% efficient, the pressure exchanger is 80-95% efficient, and a steady rate of pressure and heat leakage occurs throughout the pipeline. Current RO desalination plants report that 50-65% of the operating energy (around 2 kW-h / m 3 ) is consumed in the RO membrane unit [1]. pulling a volume fraction ∆v of input at a constant concentration and osmotic pressure difference -a process requiring zero work, but increasing the potential energy of the enclosed volume.…”

Section: Equilibrium Energy Cost Analysismentioning

confidence: 99%

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Computational and experimental platform for understanding and optimizing water flux and salt rejection in nanoporous membranes.

Rempe¹

2010

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Affordable clean water is both a global and a national security issue as lack of it can cause death, disease, and international tension. Furthermore, efficient water filtration reduces the demand for energy, another national issue. The best current solution to clean water lies in reverse osmosis (RO) membranes that remove salts from water with applied pressure, but widely used polymeric membrane technology is energy intensive and produces water depleted in useful electrolytes. Furthermore incremental improvements, based on engineering solutions rather than new materials, have yielded only modest gains in performance over the last 25 years. We have pursued a creative and innovative new approach to membrane design and development for cheap desalination membranes by approaching the problem at the molecular level of pore design. Our inspiration comes from natural biological channels, which permit faster water transport than current reverse osmosis membranes and selectively pass healthy ions. Aiming for an order-of-magnitude improvement over mature polymer technology carries significant inherent risks. The success of our fundamental research effort lies in our exploiting, extending, and integrating recent advances by our team in theory, modeling, nano-fabrication and platform development. A combined theoretical and experimental platform has been developed to understand the interplay between water flux and ion rejection in precisely-defined nano-channels. Our innovative functionalization of solid state nanoporous membranes with organic protein-mimetic polymers achieves 3-fold improvement in water flux over commercial RO membranes and has yielded a pending patent and industrial interest. Our success has generated useful contributions to energy storage, nanoscience, and membrane technology research and development important for national health and prosperity. 3 AcknowledgmentWe gratefully thank the LDRD program for funding that provided full or partial support to a summer undergraduate student intern, four Sandia postdocs, and three postdocs and a student at the U of New Mexico. We also thank the LDRD office for presenting this project with the 2010 Award for Excellence. Finally, we are indebted to Prof. Eric Jakobsson and a grant from the National Center for Supercomputing Applications at UIUC, which provided compute time to our foreign national postdoc.4

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Energy performance enhancements of a 950 m3/d seawater reverse osmosis unit in Grand Cayman

Cited by 34 publications

References 1 publication

A general formula for the rate of resonant transfer of energy between two electric multipole moments of arbitrary order using molecular quantum electrodynamics

A general formula for the rate of resonant transfer of energy between two electric multipole moments of arbitrary order using molecular quantum electrodynamics

Resonance energy transfer: The unified theory revisited

Computational and experimental platform for understanding and optimizing water flux and salt rejection in nanoporous membranes.

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