Parallel Pumping Research Articles

Constraint-based Model for Energy Optimization Management of Parallel Pumping Systems with Demand Variability

Constraint-based Model for Energy Optimization Management of Parallel Pumping Systems with Demand Variability

Reciprocal and non-reciprocal electromagnetic wave propagation in sub-100 nm epitaxial YIG thin films deposited under different oxygen growth pressure

Directional dependent transport of information in magnetic thin films offers a great opportunity to realize reciprocal and nonreciprocal microwave devices, such as filters, phase shifter, isolators and circulators. Electromagnetic wave (EM) propagation in sub-100 nm thin magnetic film is critical, yet reciprocal and non-reciprocal wave propagation and its accurate measurements remain a challenge. We investigated reciprocal and non-reciprocal wave propagation in 90 nm thick epitaxial thin films of yttrium iron garnet (Y3Fe5O12:YIG) grown by pulse laser deposition (PLD) technique on gadolinium gallium garnet [GGG(100)] substrates. The effect of oxygen growth pressure during deposition of YIG films exhibit directional dependence properties of electromagnetic wave propagation. The reciprocal EM wave propagation was generated by a S-type transmission line to achieve microwave (RF) magnetic fields (hRF) perpendicular to applied dc magnetic fields (HDC), to ensure the ferromagnetic resonance (FMR) condition. The center frequency is tuned up to 20 GHz with an applied magnetic field of 6 kOe. The tuning of the center frequency was achieved as of 85.3 % with HDC of 6 kOe. To achieve non-reciprocal EM-wave propagation one straight microstrip line was used to ensures a parallel configuration (parallel pumping FMR condition) of hRF to HDC. The nonreciprocity observed is due to the presence of gyrotropic properties in the YIG thin films and it enhances when YIG film was placed in asymmetric geometry. Further, oxygen growth pressure (>0.1 mbar) grown YIG films enhances the nonreciprocity by 21.6 %. The experimental results were successfully validated using high-frequency structure simulator (HFSS). Hence, these results indicate that controlled deposition parameters can be a crucial parameter in the design of reciprocal and nonreciprocal microwave signal processing devices.

Modelling W/O/W double emulsions preparation in static mixers: Accounting for the shear-thinning behaviour of the dispersed phase

The dispersion of a shear-thinning non-Newtonian fluid using in-line mixers to prepare double emulsions is investigated experimentally and numerically in this study. A two-step method is adopted for the preparation of double emulsions, comprising in a first step the preparation of a reverse water-in-oil (W/O) emulsion using a high-shear rotor-stator device. This inner emulsion is dispersed in a second step into an outer aqueous phase by continuous parallel pumping of both phases through a set of static mixers. The second preparation step is modelled using a population balance equation (PBE) accounting for droplet breakage inside the mixers. Since the inner emulsion behaves as a shear-thinning fluid, the breakage efficiency depends on the local shear rate. Using classical turbulent breakage kernels is therefore inappropriate, hence there is a need for a kernel accounting for the shear-thinning character of the dispersed phase. To tackle this issue, single-phase CFD simulations of the fluid flow through the mixers are carried out showing a high shear rate magnitude near the walls of the pipe and the mixer crossbars. To avoid CFD-PBE direct coupling, the probability density function (PDF) of the shear rate is extracted from the CFD simulations. This PDF is then used to develop a volume-averaged PBE, where a classical Ostwald-de Waele model is employed to relate the apparent viscosity of the inner emulsion to the shear rate. Different experimental parameters influencing the quality of the dispersion are investigated, including the fraction of the inner emulsion phase, the oil viscosity and the inner and outer aqueous phase viscosities. In the different cases, the model captures the transient evolution of the droplet size distribution of the W/O/W double emulsions at the outlet of the mixers while the computational time remains very low.

Parallel pumping of magnons in inhomogeneous spin textures probed through NV spin relaxometry

We combine micromagnetic simulations and nitrogen-vacancy (NV) defect center spin relaxometry measurements to study magnon modes in inhomogeneous spin textures. A thin, micrometer-scale ferromagnetic disk is magnetized in a vortex state in which the magnetization curls around a central core. Micromagnetic simulations show that at zero applied field, the magnetization dynamics of the disk consist of a low frequency gyrotropic mode and higher frequency azimuthal magnon modes, all far detuned from the NV spin transition frequencies. An in-plane static magnetic field breaks the azimuthal symmetry of the vortex state, resulting in the magnon modes transforming in frequency and spatial profile as the field increases. Experimentally, we probe the dynamics of vortex magnetization as a function of applied in-plane static field and ac driving frequency by optically monitoring a nearby NV defect center spin. At certain values of the applied magnetic field, we observe enhanced spin relaxation when driving at twice the frequency of the NV ground state spin transition in optically detected magnetic resonance measurements. We attribute this effect to parallel pumping of a magnon mode in the disk producing magnons at half the excitation frequency. Micromagnetic simulations support this finding, showing spatial and spectral overlap of a confined magnon mode and an NV spin transition, with sufficient interaction strength to explain the observed signal.

Operation of 2 K cryogenic system with cold compressors for the SHINE test facility

The Shanghai high repetition rate X-ray free electron laser (XFEL) and extreme light facility (SHINE), a quasi-continuous wave hard XFEL facility, is currently under construction. In order to test all the superconducting components, assembled cryomodules and undulators, the SHINE test facility that consists of various test benches has been built. A superfluid cryoplant with 1 kW@2K was installed, commissioned, acceptance tested and turned into operation to support the cryogenic tests. The plant consists not only of a standard compressor system and cold box but also of a process vacuum system for 2 K operation. In the 2 K cryogenic system, three-stage cold compressors are firstly used to compress helium vapor at a mass flow of up to 50 g/s from 28 mbar to about 400 mbar. Afterwards, the sub-atmospheric helium is continually pressurize to the suction pressure of the warm compressors by five parallel process vacuum pumps. During the first eight months of 2 K operations, the tuning of the cold compressor regulation has been implemented to adapt the different static and dynamic heat loads. A helium pressure stability of superconducting cavities better than ±0.15 mbar at 31 mbar was achieved inside the vertical test bench with additional heating power of 160 W. In this paper, the pump down procedure and the operation results of cryogenic system at 2 K will be described.

Optimal selection of parallel pumps running as turbines for energy harvesting in water transmission lines considering economic parameters

The need for energy is growing due to concerns about development and well-being, but the traditional methods of energy production harm people and the environment. This impact can be reduced by using renewable energy sources like hydropower. Since the cost of electromechanical equipment in small hydroelectric power plants accounts for a large percentage of the capital cost, applying the pump as turbine (PAT) is recommended. In this research, an effort has been made to select the optimal arrangement of PATs for a water transmission line without the need for control systems. The selection optimization process involves selecting the model of the pump as turbine and the number of turbines in parallel simultaneously. The optimization process relies on economic parameters, aiming to maximize the Net Present Value (NPV) of the power plant. In addition, the financial analysis of the project has been carried out. As a first step to achieve this objective, a database including single and double-suction pumps based on available pumps is needed. To cover a wider range of heads and flow rates, impeller trimming relationships for the pumps are considered. The Brute-Force algorithm has been used for the optimization process and two different objective functions (OF) have been investigated. First, it is based on economic optimization, and the NPV function is used as the OF; then, the Multi-Criteria Decision Making (MCDM) method is used as the second OF. The case study of this research is a water transmission line between two cities in Iran. A MATLAB code has been developed to perform all the steps of this study. The results demonstrate that by considering impeller trimming for pumps in the database and using NPV as OF, the number of pumps used for the power plant decreased from 12 to 6 and the capital cost decreased by about 10%. By implementing impeller trimming, the NPV and energy production of the PAT power plant are increased. Comparing the two desired objective functions leads to the recommended appropriate OF for applications. It is worth mentioning that the harvested energy from this water transmission line is about 9 GWh/year. The economic analysis results show that the PAT power plant payback period (PP) for this water transmission line is less than one year.

Multi-objective optimization of liquid-cooled power unit with multiple pumps in parallel under variable operating conditions

Multi-objective optimization of liquid-cooled power unit with multiple pumps in parallel under variable operating conditions

A liquid metal based, integrated parallel electroosmotic micropump cluster drive system.

The application of liquid metal in a microfluidic system enables the fabrication of highly integrated on-chip electroosmotic micropumps (EOPs). In this work, a low-voltage driveable integrated parallel EOP cluster drive system is proposed. This system consists of two layers, a branch-channel layer and a trunk-channel layer. The lower branch-channel layer contains separate parallel pumping channels and a pair of comb liquid metal electrodes. The separated branch channels are connected together through the trunk channels in the upper layer. With this structural arrangement, the parallel micropumps form an integrated micropump cluster for larger pumping capacity. The distance between the pumping channel and the electrode next to it is controlled to 20 μm. To guide the pump design, parametric studies are performed and fully discussed. According to the experimental results, the micropump cluster can be driven at a low voltage of 0.5 V, and the flow rate reaches 274 nL min-1 at 5 V. In addition, the paper finally proposes an electrode protection strategy and an integrated pump-valve drive system which is expected to solve the shortcoming of electroosmotic pumps in terms of long-time storage and driving.

System Control Methods for Energy Efficiency Improvement of Parallel Pump Systems: A Review

System Control Methods for Energy Efficiency Improvement of Parallel Pump Systems: A Review

Performance analysis of a novel combined open absorption heat pump and FlashME seawater desalination system for flue gas heat and water recovery

Thermal desalination processes generally consume a huge amount of thermal energy and industries release a large amount of latent waste heat in flue gas exhausts into the environment. In order to efficiently utilize this waste heat and to improve the energy efficiency of desalination process, this paper presents a novel combined system based on the open cycle absorption heat pump and low-grade thermal energy driven FlashME desalination. The proposed combined system is designed to recover the latent waste heat from flue gas exhausts in a parallel double stage open absorption heat pump which is driven by multiple energy sources and efficiently utilizes the recovered low temperature heat in FlashME for freshwater production. The validated process model of the combined system is developed in Aspen Plus and a parametric assessment is carried out to analyze its energy performance with the impact of various independent operational parameters by using HCOOK-H2O as an absorbent solution. The simulation results of the parametric study show that the combined system is capable of recovering the waste heat with an efficiency of 89.42 % by operating at a thermal performance coefficient of 2.21 and utilizes this heat in the form of hot seawater at 70 °C to drive FlashME desalination process for freshwater production at the performance ratio of 3.05. The critical analysis of the results highlights that the heat recovery performance of the absorption cycle is strongly dependent on the inlet parameters of flue gas and spray solution. In contrast, the water recovery performance of FlashME is dependent on regeneration pressure such that the water recovery rate varies from 9.19 % to 37.17 % with a pressure variation between 23.23 and 51.39 kPa which raises the seawater temperature 60–79 °C before the flashing stage. Furthermore, the system is flexible enough to operate with two heat sources of different temperature levels by adjusting the regeneration load in separate regenerators.

Pumps as turbines for pumped hydro energy storage systems - A small-size case study

Pumped Hydro Energy Storage (PHES) technology has been used since early 1890s and is, nowadays, a consolidated and commercially mature technology. PHES systems allow energy to be stored by pumping water from a lower-to a higher-level reservoir. Subsequently, this energy can be released through a turbine placed in a penstock, which connects the two reservoirs, to produce energy. Although these plants have historically been employed at large power scales (in the order of hundreds of MW), in recent years, micro- and small-scale plants are becoming more interesting, due to their possibility of being integrated with renewable energy systems (RES) used in autonomous island grids. Capital costs associated with hydraulic machines used in PHES systems represent the most critical economic factor, which can be mitigated by using commercial centrifugal pumps in reverse mode (Pumps as Turbines, PATs) in place of small hydro turbines. These expected economic benefits must be weighed in each specific case study, with some drawbacks related to the use of PATs, mainly associated to a lower round-trip efficiency with respect to specifically designed pumps and turbines.In this work, a small-scale PHES plant has been studied coupled to an existent photovoltaic system for the integration in the electric grid of a small island in Southern Italy. Two different PHES outlines have been compared based on techno-economic considerations. The former is a typical PHES system composed of both pumps and a turbine, while the latter uses only an array of parallel pumps which work also in reverse mode. The analysis demonstrates the feasibility of integrating a photovoltaic and PHES plant, which results in a lower cost of electricity production, while PHES performance in the PAT-based outline results penalized by the lower efficiency of PATs with respect to the hydraulic turbine.

Monolithic SOI through-wafer Knudsen pumps with mechanically robust Si channels

Knudsen pumps (KPs) generate gas flow using thermal transpiration in narrow channels with a longitudinal temperature gradient. With no moving parts, KPs offer long lifetime and are attractive for complex microfluidic systems. Although high performance was previously reported in microfabricated KPs that utilized suspended dielectric membranes to construct the pumping channels, this approach can limit the mechanical robustness and complicate the fabrication process. In this work, we present monolithically microfabricated KPs without using suspended membranes. These types of structures significantly improve the mechanical robustness, allow a wider process window, and simplify the microfabrication process. The pumping channels in this work are 14 µm in length, 1.2 × 200 µm2 in cross-section, vertically oriented, and with rigid silicon and dielectric sidewalls; the overall structures are easily manufacturable. This work primarily focuses on two core KP designs, which incorporate 4 and 6 parallel pumping channels in ≈ 11 and 17 mm2 footprints, respectively. The scaling capability is also investigated preliminarily in a design with 45 parallel pumping channels. The KPs were fabricated on a silicon-on-insulator wafer by a six-mask lithographic process with standard fabrication steps. This process eliminated the use of complicated trench refill, polish, and sacrificial dry etch steps that were required for the previously reported KPs with suspended membranes. At atmospheric pressure, the 4-channel KPs provided a blocking pressure of 620 Pa and maximum flow rate of 0.041 sccm through 0.001 mm2 channel area, using 2 W applied power. This maximum flow rate per unit channel area (sccm/mm2) is superior to that of the KPs with suspended membranes. For all the KP designs, the experimentally measured pumping performance well matched the modeling results, with <15 % discrepancy. The fabrication simplicity and reliability of the mechanically robust KPs can enable monolithic integration onto complex lab-on-a-chip systems.

Energy saving through modifications of the parallel pump schedule at a pumping station: A case study

Diverse state-of-the-art methods can be utilized to reduce energy consumption in water supply and distribution systems, including using high-efficiency equipment, shifting energy use away from peak demand times, energy recovery and storage devices, and renewable energy. However, the benefit of using high efficiency equipment can sometimes never be completely realized, as the performance of the individual pumps within a site can be reduced from optimal owing to a variety of reasons: a lower operating rate of the water treatment plant than the design flow rate, hydraulic conditions such as pipeline resistance or determined pressure, and pump scheduling. This research focused on optimizing pump scheduling through real-time monitoring utilizing smart temperature and pressure sensors, wireless low-power data communicators, and a pump data analysis algorithm to determine the hydraulic efficiency from thermodynamic state variables with subsequent parallel pump optimization. Thermodynamic pump performance measurements provided real-time information, including flow rate, specific power, and pump efficiency, in both individual and parallel pump operations. Evaluation of the specific power under diverse parallel pump operation scenarios demonstrated a variation of 0.115–0.140 kWh/m3 in the range of 7800–10,100 m3/h. However, the deviation in specific power was more than 17 % when operating at less than 7800 m3/h and more than 10,000 m3/h. The summary of the pump combination operation suggested that energy could be saved by up to 15 % by optimum pump scheduling, that is, small capital investment, simple optimization of control through thermodynamic state variable measurement, analysis, and feedback.

Parallel pump and chiller system optimization method for minimizing energy consumption based on a novel multi-objective gorilla troops optimizer

Minimizing the energy usage of the parallel pump and chiller system is a crucial method for lowering buildings’ energy consumption. The variations in the cooling load of buildings should be taken into account when optimizing the operation of the parallel pump and chiller system. Although several strategies have been put forth, it is challenging to operate at a general optimal level. The parallel pump and chiller system with different chillers and pumps is frequently used in practical applications but is rarely taken into account in literature. Hence, we propose a two-step energy consumption optimization method for a parallel pump and chiller system with different chillers and pumps based on a novel multi-objective gorilla troops optimizer (MOGTO). The gorilla troops optimizer (GTO), which makes use of an exclusive non-dominated sorting (NDS) and a diversity-preserving crowding distance (CD) mechanism, is the inspiration for the proposed MOGTO method. By resolving the trade-off between chillers and pumps, a holistic optimization based on the MOGTO algorithm was carried out to determine the least amount of energy used overall. By optimizing practical parameters, including binary and continuous variables, the overall energy consumption as well as the difference between the flow rates of pumps and chillers were simultaneously reduced. A simulation was used to examine the suggested strategy. The outcomes imply that the optimization was made logically.

Optimization of an isolated photovoltaic water pumping system with technical–economic criteria in a water users association

AbstractWith proper management, the modernization of irrigation systems makes it possible to improve the efficiency of application and use of water at the cost of an increase in pumping needs and, therefore, an increment of the energy consumed. The recent drastic price increase for energy put the viability of many farms at risk. In this context, using photovoltaic solar energy to power pumping stations has become an increasingly attractive alternative and a cheap and reliable option. The dimensioning of pumping systems powered by photovoltaic solar energy must be done considering the variability of solar radiation to take advantage of the available photovoltaic energy, especially during periods of less irradiation. By investigating a particular case, this paper studies the effect of increasing the number of pumps in parallel while maintaining the total power, as well as the relationship between the installed photovoltaic capacity and the power of the pumping system, to meet pumping requirements throughout the year. The pumped volume increased as the number of pumps installed in parallel increased for the same photovoltaic power generator. Although this increment has a limit, beyond which no greater significant rise in volume is achieved, installation costs increase. In addition, for the same pumping power installed, the required photovoltaic generator power decreases as the number of pumps in parallel increases. In the case studied, a 27% increase in the annual pumped volume was achieved by incrementing the number of pumps in parallel from one to five, thus leading to a 44.1% reduction in the size of the photovoltaic generator and a 13.3% reduction in the cost of installation compared with a system with only one pump. The procedure used to determine the most appropriate number of pumps to install in parallel when pumping water between two tanks, which minimizes the photovoltaic generator's size while guaranteeing pumping requirements, is easily generalizable for sizing isolated photovoltaic water pumping systems.

Flow distribution optimization of parallel pumps based on improved mayfly algorithm

An improved mayfly algorithm is proposed for the energy saving optimization of parallel chilled water pumps in central air conditioning system, with the minimum energy consumption of parallel pump units as the optimization objective and the speed ratio of each pump as the optimization variable for the solution. For the problem of uneven random initialization of mayflies, the variable definition method of Circle chaotic mapping is used to make the initial position of the population uniformly distributed in the solution space, and the mayfly fitness value and the optimal fitness value are incorporated into the calculation of the weight coefficient, which better balances the global exploration and local exploitation of the algorithm. For the problem that the algorithm is easy to fall into the local optimum at the later stage, a multi-subpopulation cooperative strategy is proposed to improve the global search ability of the algorithm. Finally, the performance of the improved mayfly algorithm is tested with two parallel pumping system cases, and the stability and time complexity of the algorithm are verified. The experiments show that the algorithm can get a better operation strategy in solving the parallel water pump energy saving optimization problem, and can achieve energy saving effect of 0.72% 8.68% compared with other optimization algorithms, and the convergence speed and stability of the algorithm have been significantly improved, which can be better applied to practical needs.

Fuzzy Pressure Control: A Novel Approach to Optimizing Energy Efficiency in Series-Parallel Pumping Systems

Automation and control systems are constantly evolving, using artificial intelligence techniques to implement new forms of control, such as fuzzy control, with advantages over classic control strategies, especially in non-linear systems. Water supply networks are complex systems with different operating configurations, uninterrupted operation requirements, equalization capacity and pressure control in the supply networks, and high reliability. In this sense, this work aims to develop a fuzzy pressure control system for a supply system with three possible operating configurations: a single motor pump, two motor pumps in series, or two motor pumps in parallel. For each configuration, an energy efficiency analysis was carried out according to the demand profile established in this case study. In order to validate the proposed methodology, an experimental water supply system was used, located in the Laboratory of Energy Efficiency and Hydraulics in Sanitation at the Federal University of Paraiba (LENHS/UFPB).

Thermodynamic analysis of a novel tri-generation system integrated with a solar energy storage and solid oxide fuel cell – Gas turbine

The conventional cooling, heating and power tri-generation system still has problems such as high greenhouse gas emissions and high fossil fuel consumption. A new integrated energy system is proposed which includes solar-methanol hydrogen production, energy storage device, solid oxide fuel cell and dual-effect absorption chiller/heat pump with less carbon dioxide emissions, higher energy conversion efficiency and less fossil fuel consumption. The solar energy storage device drives the methanol reformation reaction and the Li-Br chiller/heat pump in parallel, decoupling the power and cooling/heating of the system to simultaneously satisfy the user demands and increases system flexibility. The proposed system is modeled and simulated in Aspen Plus and Fortran. The system thermodynamic performance is analyzed at the design conditions and the results shows the new system obviously enhances the energy conversion efficiency compared with the reference system. The effects of the methanol flow rate on the system output parameters and the thermodynamic performances of the system in different seasons when meeting the cooling, heating and power needs of the district users are studied. The results shows that the maximum system energy efficiency is 92.98% when the system operates in summer, and the system power generation efficiency is 48.03%; in winter, the maximum total system energy efficiency reaches 146.30%, and the system power generation efficiency is 53.26%; in the transition season, the system only needs to provide users with power load and domestic hot water, and the exhaust gas provides the methanol reaction heat. The system power generation efficiency increases to 65.38% and the energy efficiency is 87%.

Optimal control of outdoor transmission and distribution pipe networks for district heating and cooling systems

The optimization of the differential pressure setting value mostly uses the valve position signal as the monitoring parameter, but in the district heating and cooling systems (DHCSs), the end valve position signal has hysteresis and cannot be completely collected. Therefore, a variable differential pressure control strategy based on end-load monitoring is proposed in this paper, which can satisfy differential pressure requirements at the most unfavorable thermodynamic end. Then combined with the optimal control of parallel pumps, pay attention to the situation that the rated head of the variable frequency pump is much greater than the differential pressure of the pipe network, and consider operating at the lower frequency limit of the variable frequency range to minimize the total energy consumption of the pump. A district energy station in Chongqing is used as the research object to verify and evaluate the proposed optimization strategies. The test results reveal that the proposed optimal control strategies demonstrate a positive control effect and the performance of the pipe network and pump operation are significantly improved. Compared with the traditional constant differential pressure control strategy, the energy consumption of the pump under heating conditions can be reduced by up to 34.27%.

An Asynchronous Gradient Descent Based Method for Distributed Resource Allocation With Bounded Variables

This article considers the distributed resource allocation problem over a network of n agents with individual optimization functions and coupled resource constraints. The optimization variables are bounded for each agent. We propose an asynchronous distributed gradient descent based method, which is able to tackle time-varying communication networks and communication problems. The main ideas are twofold. First, the degree of freedom of the network is reduced to deal with the global constraint. Second, we utilize delay compensation to counteract the delay of asynchronous communication. We prove that the convergence rate is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$O(\frac{1}{k})$</tex-math></inline-formula> and analyze both the communication complexity and the time complexity. This method is applied into the parallel pump control problem in HVAC system and shows good numerical results.