Pressure effect on an ocean-based humidification-dehumidification desalination process

A new humidification-dehumidification (HDH) desalination process is proposed and analyzed. Being ocean based, the process does not produce any brine. It is largely powered jointly by solar energy, wind energy, and various types of ocean energies in a nearly natural way. A vacuum pump is employed to drive the air circulation throughout the HDH process. It is the only unit that consumes electricity. The HDH process is analyzed under various conditions, including using a low pressure (as low as to 0.2 atm) for humidification and the ambient pressure for dehumidification, running the entire HDH process around a low pressure (as low as to 0.2 atm), and running it around the ambient pressure. The results from case studies show that applying different pressure levels to humidification and dehumidification would lead to a prohibitively high electric energy consumption of the vacuum pump. Being the most favorable operating condition, running the HDH process around the ambient pressure yields a freshwater production rate at the level of 4 to 11 l/h per HDH line, depending on the pipe sizing and weather conditions. The associated minimum electric energy consumption of the vacuum pump is at the level of 0.9 to 1.6 kWh/m(3)-water

Unidirectional Rotary Tendency of a Wave-Driven Rotor

Ocean waves can directly drive WECs (wave energy converters) to perform two types of motion—reciprocating motion and unidirectional rotary motion. In general, the efficiency of a reciprocating WEC is strongly wave-frequency dependent, whereas the efficiency of a rotary WEC can be somewhat wave-frequency independent. To date, a huge majority of WEC technologies under development in industry belong to the reciprocating class, and only a few WEC concepts fall in the unidirectional rotary class. In the present work, a wave-driven rotor for unidirectional rotary motion was proposed and characterized. A numerical tool has been developed for characterization of the rotor’s unidirectional rotary tendency. The tool included a wave model and a drag force model. Simple circular tubes were used as blades in a basic rotor design. This basic design demonstrated strong potential for unidirectional rotary motion at a proper rotor submersion level and under various wave conditions. Two improved designs were yielded from the basic design. In one improved design, the original circular tubes were replaced with cylindrical shells of semicircular cross section as new blades. In another design, the semicircular shells were further modified to become one-way foldable. The two improvements significantly enhanced the rotors’ unidirectional rotary tendency in waves, which has been verified by numerical simulation. Broad ranges of wave parameters and the submersion level have been numerically explored on the two improved rotor designs in conjunction with dimensional analysis

Robust Matrix Completion State Estimation in Distribution Systems

Due to the insufficient measurements in the distribution system state estimation (DSSE), full observability and redundant measurements are difficult to achieve without using the pseudo measurements. The matrix completion state estimation (MCSE) combines the matrix completion and power system model to estimate voltage by exploring the low-rank characteristics of the matrix. This paper proposes a robust matrix completion state estimation (RMCSE) to estimate the voltage in a distribution system under a low-observability condition. Tradition state estimation weighted least squares (WLS) method requires full observability to calculate the states and needs redundant measurements to proceed a bad data detection. The proposed method improves the robustness of the MCSE to bad data by minimizing the rank of the matrix and measurements residual with different weights. It can estimate the system state in a low-observability system and has robust estimates without the bad data detection process in the face of multiple bad data. The method is numerically evaluated on the IEEE 33-node radial distribution system. The estimation performance and robustness of RMCSE are compared with the WLS with the largest normalized residual bad data identification (WLS-LNR), and the MCSE

A Vertical Axis Rotor for Wave Energy Conversion

The present work augments vertical-axis unidirectional wave energy converter (WEC) designs with a new approach. The enabling technique is the hydrodynamic design of a special rotor, which consists of a series of uniquely shaped blades in a certain formation. Specifically, individual blades are realized by revolving a two-dimensional symmetric hydrofoil about its chord line. Then the blades are arranged around a vertical shaft in a desired formation to form the rotor. When driven by an approaching flow through interaction, the rotor naturally rotates about the vertical shaft in a predefined direction. The approaching flow could be from any spatial direction, and could have changing speed and direction in any fashion, but the unidirectional behavior of the rotor never changes. Such a behavior guarantees a unidirectional performance of the rotor in waves, where the water flow is omnidirectional and constantly evolving. In validating the proof of concept and characterizing the rotor’s unidirectional performance, experiments were carried out under various flow conditions. Specifically, three types of flows were employed: horizontally oscillating flow, vertically oscillating flow, and orbital flow along a circular path in a vertical plane. The three flows were actually created by translating the rotor in still water, with the first two to characterize the rotor’s responsiveness to the flow direction and the third one to simulate rotor interaction with deep waves. For each flow type, different rotor configurations/blade formations were examined under various testing parameters. For all the cases, the rotor shaft was kept vertically all the time. The experimental results are discussed in details in the paper

Artificial lateral line canal for hydrodynamic detection

Fish use their lateral line system to detect minute water motions. The lateral line consists of superficial neuromasts and canal neuromasts. The response properties of canal neuromasts differ from those of superficial ones. Here, we report the design, fabrication, and characterization of an artificial lateral line canal system. The characterization was done under various fluid conditions, including dipolar excitation and turbulent flow. The experimental results with dipole excitation match well with a mathematical model. Canal sensors also demonstrate significantly better noise immunity compared with superficial ones. Canal-type artificial lateral lines may become important for underwater flow sensing

A Vertical Axis Wave Turbine With Hydrofoil Blades

This work discusses a new wave energy converter (WEC) design that, when deployed in waves, performs unidirectional rotation about a vertical shaft. The uniqueness of this new WEC design is on utilizing omnidirectional water flow generated by waves to drive a rotor to perform unidirectional rotation about a vertical axis. This unique feature circumvents the frequency-dependent issue of common WECs, and eliminate realignment needs to cope with dynamically changing wave propagation directions. The key component of the WEC is a rotor, which has a vertical shaft with a number of blades mounted to it. Each blade has a hydrofoil-shaped cross section and is in a bent shape along its span. The spanwise bending of the blades makes the rotor capable of gaining a unidirectional driving torque about the vertical shaft no matter in which spatial direction the local water is passing by. For validating the WEC design and gaining preliminary understanding, a very first rotor model without any parametric optimization was built. Two types of experiments were then carried out by employing this model. In the first type, the model was translated (with the shaft vertically aligned all the time) in still water along a horizontal direction (back and forth), a vertical direction (up and down), and a circular orbit in a vertical plane. In the second type, the model was exposed in waves generated in a wave flume. In all the experiments, well-established unidirectional rotation of the rotor about its vertical shaft has been observed. The hydrodynamic performance of the rotor in waves was further characterized through systematic experiments under various conditions

Recovery of rectified signals from hot-wire/film anemometers due to flow reversal in oscillating flows

Hot-wire/film anemometers have been broadly used in experimental studies in fluid mechanics, acoustics, and ocean engineering. Yet, it is well known that hot-wire/film anemometers rectify the signal outputs due to the lack of sensitivity to flow direction. This main drawback, in turn, makes them less useful for diverse fluctuating flow measurements. To solve this issue, a rectification recovery method has been developed based on reconstruction of the Fourier series expansion in conjunction with signal-squaring approach. This signal recovery method was experimentally examined and proven to be successful for both conventional and microfabricated hot-wire/film anemometers. The method was further applied to dipole field measurements, with data from recovered signals perfectly matching the analytical model of the dipole field

State Estimation in Low-Observable Distribution Systems Using Matrix Completion

The need for distribution system state estimation is on the rise because of the increased penetration of distributed energy resources and flexible load. To manage the distribution systems in real time, operators need to firstly overcome the challenge of low observability in distribution systems. Also, because of the amount of data present from smart meters, distributed generation measurements, switches, etc., the ideal distribution state estimation methods need to be able to process heterogeneous data. In this paper, an algorithm is developed for voltage phasor estimation in low-observability distribution systems. The algorithm is based on the matrix completion approach from signal processing. The traditional matrix completion formulation is augmented with power-flow constraints to improve results while requiring less data. This method can also use all types of measurements (voltage magnitude, voltage angle, real power, reactive power) to complete the state matrix

Numerical Study of Fully Coupled Fluid-Structure Interaction of Stented Ureter by Varying the Stent Side-Holes

Ureteral stents are a measure used for many medical issues involving urology, such as kidney stones or kidney transplants. The purpose of applying stents is to help relieve the urine flow while the ureter is either blocked or trying to close itself, which creates blockages. These ureteral stents, while necessary, cause pain and discomfort to patients due to them being a solid that moves around inside the patients’ body. The ureter normally moves urine to the bladder through peristaltic forces. Due to the ureter being a hyperelastic material, these peristaltic forces cause the ureter to deform easily, making it necessary for the stent to properly move the urine that flows through it for the patient not to face further medical complications. In this study, we seek to find a relation between the amount of stent side holes and the overall flow rate inside the stent with the ureter contracting due to peristalsis. A fully coupled fluid-structure interaction (FSI) model is developed to visualize how the ureter deforms due to peristalsis and the subsequent effect on the urine flow due to the ureter’s deformation. Numerical simulations using COMSOL Multiphysics, a commercial finite-element based solver, were used to study the fluid-structure interaction, and determine whether the stent performs more properly as the amount of stent side holes increases. The results showed that the stent model with a 10 mm distance between side hole pairs provided the highest outlet flow rate, which indicates a proper stent design that allows for maximized urine discharge. We hope this study can help improve the stent design in kidney transplant procedures to further ease the inconvenience on the patients

Artificial lateral line canal for hydrodynamic detection

Fish use their lateral line system to detect minute water motions. The lateral line consists of superficial neuromasts and canal neuromasts. The response properties of canal neuromasts differ from those of superficial ones. Here, we report the design, fabrication, and characterization of an artificial lateral line canal system. The characterization was done under various fluid conditions, including dipolar excitation and turbulent flow. The experimental results with dipole excitation match well with a mathematical model. Canal sensors also demonstrate significantly better noise immunity compared with superficial ones. Canal-type artificial lateral lines may become important for underwater flow sensing