Numerical Model of a District Water Distribution System in Bucharest

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.

Variable water demands in growing season, spatial altitude difference in hydrant points, incompatibility in irrigation time, crop pattern alternation and the other environmental factors are among the most important dynamic factors affecting the operation of pumping stations in an irrigation system. Pumping stations could be effectively operated using a dynamic or time-dependent approach. In this study, the performance of an agricultural pumping station, which will be equipped with variable speed pumps, was analyzed. The station is located in an agricultural area in Qazvin Province, northern Iran. The dynamic model of the pumping station was developed for simulating five defined operation scenarios. The results showed that using variable speed pumps is capable of reducing energy consumption up to 67 %, in comparison with current constant speed modes. The ratio of energy consumption for pumped water was determined equal to 0.37 kwh/m3 in variable speed mode, implying up to 45% reduction in comparison with use constant speed pumps.

ANNs-based modeling and prediction of hourly flow rate of a photovoltaic water pumping system: Experimental validation

Economic development and population growth are continuously increasing the pressure on water utilities. Water transmission and distribution networks are considered an energy-intensive process. The primary energy consumption in water networks is due to pumping. Minimizing the energy consumption of the pumps becomes the primary target for many water utilities around the world. This research aims to develop a decision tool to optimize pumping operation costs in water distribution networks. A pilot case study from a utility water network company is selected to develop and test a new optimization tool. The case study consists of two water pumping stations, six variable speed pumps, six tanks, and nine demand nodes. The operation system of these pumping stations automatically controls all the variables (motor speed, pressure, flowrate, valve opening, and closing) that will satisfy the hydraulic requirement of the water network. Currently, the start and stop of each pump are decided based on human experience regardless of the electricity tariff. In this study, a new optimization decision tool is developed to help the operation decide the optimum pumping flowrate for the upcoming 24 hours, minimizing pumping cost and satisfying all requirements and constraints. The model required the user to fill the hourly demand forecast at each demand node, electricity tariff, initial tanks level, maximum and minimum pump flowrate. The optimization model uses a linear programming algorithm for finding the optimum flowrate for 24 hours. AIMMS optimization software was selected for the implementation of the optimization model and the development of a user-friendly interface. The optimum flowrates were tested on EPANET to verify the feasibility of the optimum schedule from hydraulics perspectives. Results show that the new optimization tool is robust and has successfully reduced the energy cost of a pumping station by up to 9%.

Pressure-rate convolution and deconvolution response for fractured conventional and unconventional reservoirs using new decline rate model

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.

The control system’s point is to bring the pumping curve close to the set-point curve. That concept is essential for proper design of a pumping station. An adequate design is focused not only on selecting the total number of pumps and the type of control to use (flow or pressure), but it also is important to determine the optimal number of fixed speed pumps (FSPs) and variable speed pumps (VSPs) for each flow rate. This work discusses the most common methods and procedures for control systems on a design of pumping stations with a proposed methodology. This methodology consists of expressing the characteristics of the pumping curve and the set-point curve in a dimensionless form so that the methodology is standardized for any pump model and set-point curve. These formulations allow us to discuss how the characteristic of a pump and the set-point curve of the network influence the optimal number of FSPs and VSPs in energy terms. In general, the objective of this work is to determine the most suitable total number of pumps in a pumping station design and to determine the optimal pumping configuration in every flow rate, thus the consumed energy would be the minimum. Additionally, this methodology develops an expression to estimate the performance of a frequency inverter when a VSP operates at different rotational speeds. This work will be applied to different study cases, and the obtained results allow us to question several usual procedures for pumping control system. In general, it can be concluded that the number of pumps of a pumping system cannot be inferred in a simple form without a deep analysis of a control system.

Chapter 15 - Variable-Speed Pumping

Variation in the flow rate of drip emitters in a subsurface irrigation system for different soil types

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

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.

A large amount of energy would be consumed for open-channel water transfer projects due to the low efficiency of pumping stations. One measure to improve the efficiency of a pumping station is to install variable-frequency drives (VFDs). In this paper, a discharge optimization model is proposed for a single pumping station equipped with different numbers of variable speed and blade angle-adjustable pump (VSBAP) units, and then a head optimization model is proposed for cascade pumping stations. The study on the Miyun Reservoir Regulation and Storage Project in China shows that the installation of VFDs can increase the number of operable conditions of a single BAP unit by changing the blade angle and speed and ensure the high efficiency of the pumping unit under most operating conditions, thus reducing the energy consumption of the pumping station. It is desirable to install two VFDs in the Tuancheng Lake–Huairou Reservoir section to ensure the long-term operation of the cascade pumping stations in an economically profitable way. In conclusion, the installation of VFDs can effectively reduce the operation cost of cascade pumping stations.

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.

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.