Flexibility of energy and water management in pressurized irrigation systems using dynamic modeling of pump operation

In pressurized water distribution systems, a constant speed pump is often used because of its simplicity. However, constant speed pumps are not easily able to deal with changing demands in water flows. When the demand for the discharge differs from the design discharge, the required demand (discharge and head) could be met by changing the pump speed without making any special changes in the system. Using an electronic drive circuit, the electrical frequency can be changed, and the rotation speed of the pump motor can thus be modified. In this study, the application of variable speed pumps in pressurized irrigation systems is investigated. Two pumping station scenarios including a fixed speed pump and a variable speed pump are considered. The selected pump station includes a real sprinkler irrigation system near Tabriz city, Iran, with 3 lateral pipes and 600 m length of main pipe. The diameter of the main pipes is 8 and 6 inches. The results show that using a variable speed pump increases the average pump efficiency by 18.7%. In addition, the variable speed pump system reduces the electrical consumption 57.6% compared to a fixed speed pump. Therefore, the use of variable speed pumps in pressurized systems is recommended. Step-by-step calculations for a sprinkler irrigation system design are the contribution of this study. This information helps engineers who are not familiar with commutation process.

Because of its simplicity, a constant speed pump is frequently employed in pressured water distribution systems. Constant-speed pumps, on the other hand, struggle to cope with fluctuating water flow needs. When the discharge demand differs from the design discharge, the needed demand (discharge and head) can be fulfilled by simply altering the pump speed without making any other system changes. In this study, the efficiency of stations equipped with variable speed pumps under all operating conditions exceeds that of stations equipped with fixed speed pumps. The use of variable speed pumps not only increases efficiency but also aids in meeting water needs. In this study, the application of variable speed pumps in pressurized irrigation systems is investigated. The chosen pump station contains an actual sprinkler irrigation system with three lateral lines and a 600-meter main pipe near Tabriz, Iran. The primary pipes are 8 and 6 inches in diameter. The use of a variable speed pump enhances average pump efficiency by 18.7%, according to the findings. In addition, as compared to a fixed speed pump, the variable speed pump system saves 57.6% on electricity. As a result, variable speed pumps should be used in pressurised systems. This research contributes step-by-step calculations for sprinkler irrigation system design. Engineers who are unfamiliar with the commutation procedure will benefit from this knowledge.

Low efficiencies of irrigation pumping stations usually stem from their improper designing, operation, and maintenance of such systems. In the present study, the water and energy losses and the pressure variations of a pressurized irrigation system were investigated through analysing the characteristic curves of the pumps and assessing the discharge and pressure heads needed by the system during the irrigation season (i.e. the system demand curves). Variable-speed pumps can be adjusted to the system demand, making them more efficient than constant-speed pumps while bringing down water and energy consumption. Given this assumption, the suitability of variable-speed pumps to save water and energy in a 100 hectares apple and peach orchard, located in Isfahan Province, central Iran, was investigated. The pressure head, the pump efficiency, and the water and energy losses of the orchard’s irrigation system designed based on variable-speed pumps were calculated and compared with those of common constant-speed systems. The results showed that using variable-speed technology in designing pumping stations not only increases the efficiency and reduces unnecessary pressures but also can result in optimal water use and, depending on operational condition, 44–54% reduction in energy consumption can be achieved, which is significant in national scale.

At present, constant speed pumps and variable speed pumps always run in parallel in pump stations of most water supply companies in China. Research on the frequency control characteristic for the mixed-pump station based on the two-stage optimal operation is performed. Firstly, the ratio of the variable speed pump is calculated inversely according to the outlet pressure of the pump station, and then the speed range can be determined dynamically, so that the variable speed pump can play the role of energy saving as far as possible in safe and rational running status. Secondly, the two-stage optimal operation model for mixed-pump stations of multi-source is established, which is of the operating-mode adaptability, and it is solved by the intelligent genetic algorithm. Furthermore, when the operation mode of multi-source pump stations is transformed, the optimal dispatching of water distribution system in corresponding operation mode can be realized through adjusting the variable parameters in the model. At last, the utility and superiority of the optimal operation method for mixed-pump stations of multiple resources is verified by means of the application in certain urban in China.

To analyze a system of maintaining a fixed hydraulic head at a location for delivering adequate water supply with little or no storage, a conventional hydraulic model could be applied with constant speed pumps. However, modelers would need to iteratively adjust pump speed for each variable speed pump (VSP) to identify the appropriate speed factors at each time step. No doubt, this is a time consuming task, specially, when there are multiple VSPs installed in a system. This paper presents a technically enhanced approach that extends the hydraulic network model to automatically calculate the pump speed that is to deliver a prescribed hydraulic head. The improvement allows engineer to model not only a single VSP without rule-based control, but also multiple VSPs with simple and logic controls. The desired control head can be specified at any location in a system. This feature offers great flexibilities and modeling capabilities for engineers to efficiently analyze a variety of scenarios for the systems where VSPs are installed.

The present work analyzes energy saving in on-demand irrigation systems served by an upstream pumping station. The objective of this work is to identify the best pumping station operating mode to optimize energy consumption. This objective can be achieved by matching the discharge and the pressure head required by the network (characteristic curve of the network) during the whole irrigation season with the pumping station characteristic curves. The characteristic curve of the network can be obtained using an appropriate stochastic generation modeling, and COPAM software was used in the present work. The characteristic curves of the pumps can be adapted to the network characteristic curve by equipping the pumping station with variable speed devices. Several types of regulation based on variable speed techniques were identified and analyzed. The differences in energy consumption for each technique were quantified for two on-demand irrigation districts in Southern Italy and managed by the Water Users Organization “Consortium of Capitanata”. It was demonstrated that in comparison with the current pumping station regulation, energy savings of about 27 and 35% may be achieved for the two districts.

Greenhouse gas emission is one of the main environmental issues of today, and energy savings in all industries contribute to reducing energy demand, implying, in turn, less carbon emissions into the atmosphere. In this framework, water pumping systems are one of the most energy-consuming activities. The optimal regulation of pumping systems with the use of variable speed drives is gaining the attention of designers and managing authorities. However, optimal management and operation of pumping systems is often performed, employing variable speed drives without considering if the energy savings are enough to justify their purchasing and installation costs. In this paper, the authors compare two optimal pump scheduling techniques, optimal regulation of constant speed pumps by an optimal ON/OFF sequence and optimal regulation with a variable speed pump. Much of the attention is devoted to the analysis of the costs involved in a hypothetical managing authority for the water distribution system in order to determine whether the savings in operating costs is enough to justify the employment of variable speed drives.

Numerical Model of a District Water Distribution System in Bucharest

The purpose of the present paper is to study the key factors responsible for the unsuccessfulness of under pressure irrigation systems in Ilam Province. The research method is casual-relative which is conducted in the form of a survey research. The statistical society of this study includes 440 exploiters who own farming or garden lands and the credits of agriculture bank are granted to them to execute the rain irrigation systems. The sampling method to conduct the study is proportional stratified sampling. To determine the sample size, Kerjesy and Morgan table is used. According to the data of this table, a statistical sample of 250 persons is chosen. The basic tool used in collecting data of this study is questionnaire. To study the reliability of research tools, 30 persons of rural exploiters who are inhabitants of Ilam Province are chosen by random. According to this, the reliability factor of research tool is calculated 92% by using the Cronbach alpha coefficient. Data analysis and processing was conducted in two levels: Descriptive (central and dispersion tendency) and analytic (Spearman correlation coefficient and multi-variable regression in a step-wise form). Results of this study show that there is a meaningful relationship between variables of: The work of designer company, irresponsibility in giving services after installing, incompatibility of under pressure irrigation systems with agricultural-climatic conditions, low quality and broken equipments, the problem of moving pipes and equipments, high expenses of fixing and changing equipments, turn taking of the water, insufficient times and time of irrigation with the variable of unsuccessfulness of under pressure irrigation systems. Results of regression analysis of effective factors on unsuccessfulness of under pressure irrigation systems using step-wise method show that five factors, including: Moving pipes and equipments, low quality and broken equipments, lack of skill and proficiency in company employees for incorrect designing and installing; high expenses of fixing and changing equipments have totally determined the variance of 75%. Key words: Under pressure irrigation, unsuccessfulness, farmers.

A computer model was developed to simulate pressure and flow rate distribution along pipes and laterals of pressurized irrigation systems in operation. The software runs in a Windows environment and is capable of simulating irrigation systems having multiple pump stations combined in series and/or in parallel, booster pump stations, parallel pipes and looping pipes. Hand-move, wheel line and center pivot laterals with pressure regulators, one or two drop pipes per outlet and booster pump can be simulated. Leakage can be included in the main pipe network or along the laterals. Lateral inlet pressure can be set to an upper limit to simulate valve closure. Practically any type of nozzle and pump can be simulated since cubic spline functions are used to interpolate values from head-flow rate sets of data. To accomplish these capabilities, algorithms were developed and adapted to convert laterals into a set of head-flow rate data so that a simplified algorithm could be adapted to solve the entire pipe network. A user-friendly interface was designed to allow data for pumps, nozzle and pressure regulators to be interactively entered, edited and analyzed prior to the simulation run. The layout of the irrigation system can be drawn on screen using the mouse. Data can be independently entered and edited for each irrigation system component already drawn in the screen, at any time and in any order. Data for the entire irrigation system are verified at many levels before the simulation is run, to make the model less susceptible to crash. The model proved to be a practical tool for upgrading and designing pressurized irrigation systems.

To analyse duty points dropdown when centrifugal pumps run with cavitation on their suction side, experiments were conducted on a pumping station (PS) rig, where up to three variable speed driven pumps can run in parallel-coupling. The PS rig is equipped with insufficient measuring devices, like most urban PS-s. The duty points shifting was assessed with respect to pumps' performance curves. A comparison was made with respect to duty points obtained for a regime free of cavitation, after changing the suction pipe (from DN40 to DN63). Global recordings were available, namely a pressure head inside the PS-unit, and the total discharge flow rate at the PS exit. Duty points for each pump were derived using a sensorless control approach and the affinity laws. For the pumps running at nominal speed, the fully cavitating and the incipient cavitating regimes were proved by the NPSH available at the pump inlet, with respect to the NPSH required by the pump. The fully developed cavitation starts way below the 3% head dropdown limit.

Fontan surgery constructs Total Cavo-Pulmonary Connection Circulation (TCPC), but lacks power. Cavopulmonary circulation assist devices (CPAD) has been proposed to support the Fontan circulation. The virtual implantation of blood pumps into the real TCPC structure to analyze the output characteristics of blood pump and flow pattern can better guide design of the pump and the formulation of powered Fontan surgical protocols. We used computational fluid dynamics (CFD) to explore the power assistance effect of an axial flow blood pump when it was virtually implanted in the real TCPC structures of patients with Fontan circulation and analyzed the differences between constant-speed pumps and variable-speed pumps. Numerical simulation results showed that the implantation of the blood pump increases pulmonary circulation blood flow by 32.6%, significantly improving the uneven distribution of flow in the left and right pulmonary arteries (the left/right pulmonary artery flow ratio improved from 1:1.8 to 1:1.2). The constant-speed pump mode increased hepatic venous return flow by 19.4% compared to baseline conditions, whereas the variable-speed pump improved it only by 12.7%. The constant-speed pump generated more stable spiral flow patterns in the TCPC structure, reducing energy loss by 21.3% compared to the variable-speed pump, and the wall shear stress distribution in the inferior vena cava (IVC) region was found to be closer to physiological conditions. According to the results, we confirm that the constant speed mode in powered Fontan circulation has significant advantages in maintaining blood flow stability, optimizing energy efficiency, and promoting organ-specific venous return.

Energy is an important material foundation for developing the national economy and improving human living standards. We discussed the energy-saving principle of urban water supply system variable frequency pumping by analyzing the urban water supply and water pumping station curves, further studied the best speed and flow adjustment range of the Urban Water Supply Systems Variable Speed Pump, from both economic and efficient operation of pumps taken into account to determine the best number of the speed pump sets, which can be referenced for the design of urban water supply system variable frequency speed pump station.

Optimal short-term water-energy dispatch for pumping stations with grid-connected photovoltaic self-generation

Pressure measurements at critical locations in the irrigation system (distributed pressure measurements) wereused to optimize operation of an electric pumping plant equipped for variable speed operation. Operation of the pumpingplant was optimized in terms of providing adequate irrigation coverage with minimum energy use. The pumping plantsupplied water to a single center pivot on undulating topography. The center pivot was equipped with a supervisorycontrol and data acquisition system for variable rate water application. Electrical demand of the irrigation system wasevaluated under four variable speed pumping control schemes. Disregarding inefficiencies of the variable frequencymotor controller, distributed pressure measurement resulted in 15.8 and 20.2% energy savings compared to constantspeed pumping for uniform and variable rate irrigation, respectively. When the efficiency of the variable frequency motorcontroller is accounted for, distributed pressure measurement resulted in 7.5 and 12.4% energy savings compared toconventional constant speed pumping for uniform and variable rate irrigation, respectively. Use of distributed pressuremeasurements to control the variable speed pumping plant was highly effective in minimizing energy use whilemaintaining the pressure required throughout the irrigation system.