Pumping water for irrigation can be a major expense for irrigated farms. In 2003 more than 500,000 pumps were used for irrigation, and the total estimated energy cost nationwide was over 15.5 billion dollars. Improving the efficiency of irrigation pumps has many benefits, including improving the profitability of the irrigated farm.
When a single pump is required to operate over a range of flow rates and pressures, standard procedure is to design the pump to meet the greatest output demand of both flow and pressure. For this reason, pumps are often oversized and they will be operating inefficiently over a range of duties. This common situation presents an opportunity to reduce energy requirements by using control methods such as a variable speed drive.
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Variable speed pumping: A guide to successful applications.
Pumping systems account for nearly 20% of the world’s energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial
facilities. Significant opportunities exist to reduce pumping system energy consumption through smart design, retrofitting, and operating practices. In particular,
the many pumping applications with variable-duty requirements offer great potential for savings. The savings often go well beyond energy, and may include improved performance, improved reliability, and reduced life cycle costs. Most existing systems requiring flow control make use of bypass lines, throttling valves, or pump speed adjustments. The most efficient of these is pump speed control. When a pump’s speed is reduced, less energy is imparted to the fluid and less energy needs to be throttled or bypassed. Speed can be controlled in a number of ways, with the most popular type of variable speed drive (VSD) being the variable frequency drive (VFD). Pump speed adjustment is not appropriate for all pumping systems, however. This overview provides highlights from Variable Speed Pumping — A Guide To Successful Applications, which has been developed by Europump and the Hydraulic Institute as a primer and tool to assist plant owners and designers as well as pump, motor, and drive manufacturers and distributors. When the requirements of a pump and system are understood, the user can consult this guide to help determine whether variable speed pumping is the correct choice. The guide is applicable for both new and retrofit installations and contains flowcharts to assist in the selection process.
Energy efficiency: benefits of variable speed control in pumps, fans and compressors
A large proportion of the electricity produced around the world is used to raise, move or pressurize liquids and gases with machines such as pumps, fans and compressors.
Given the increasing importance of controlling energy consumption, special attention must be paid to the way these machines are operated and the energy savings that can be achieved through variable speed control. These different aspects will be dealt with in this Cahier Technique publication, both from the qualitative and quantitative standpoint. Variable speed drives are among the front-ranking solutions proposed by Schneider Electric to increase Energy efficiency.
A visual tool to calculate optimal control strategy for non-identical pumps working in parallel, taking motor and VSD efficiencies into account
A simple graphical tool was developed, that finds the optimal combination of pumps and their rotational speeds for all possible working points for a pump battery. The tool was integrated into EPANET as well as EPA SWMM simulation packages. The tool allows us to analyse and optimize operation non-identical parallel pumps with different minimum and maximum frequencies for all possible working points. Pump characteristics and efficiency curves can be given in tabular format or as analytical functions of flow. Degradation of pump efficiency at lower rotational speed is taken into account, as well as motor and variable speed drive efficiencies at partial loads. The optimal solution provided by the tool was compared to measurements in two case studies. Our case studies showed 6.1–8.5% reduction in energy usage using the optimal parallel pumping control strategy compared to the currently used strategy, where all running pumps have the same frequency
Detailed dynamic pumping energy models for optimization and control of wastewater applications
Despite the increasing level of detail in wastewater treatment process models, oversimplified energy consumption models (i.e. constant ‘average’ power consumption) are being used in optimization exercises. A new dynamic model for a more accurate prediction of pumping costs in wastewater treatment has been developed to overcome this unbalance in the coupled submodels. The model is calibrated using two case studies. The first case study concerns the centrifugal influent pumps (Nijhuis RW1-400 · 525A) of the municipal wastewater treatment plants (WWTPs) in Eindhoven (The Netherlands), governed by Waterboard De Dommel. For the second case study, concerning a centrifugal pump (Flygt, type NT3153 · 181) of the intermediate pumping station (pumping primary treated wastewater) of the Mekolalde WWTP, located in Bergara (Guipúzcoa, Spain), a model extension was necessary in order to allow a better description of the pump curve, making the model more generic. Both cases showed good agreement between the model predictions and the measured data of energy consumption. The model is thus far more accurate compared with other approaches to quantify energy consumption, paving the way towards ‘global’ process optimization and new, improved control strategies for energy reduction at WWTPs.
MONTEIRO, M.A.G.; MONACHESI, M.G. Eficiência energética em sistemas de bombeamento. Rio de Janeiro, Eletrobras; Procel, 2005. 86 p. (Manual Prático)
MONTEIRO, M.A.G.; MONACHESI, M.G. Eficiência energética em sistemas de bombeamento. Rio de Janeiro, Eletrobras; Procel, 2005. 86 p. (Manual Prático)
Please note that this text is in Portuguese
Pump cavitation various npshr criteria, nphsa, margins, and impeller life expectancy
This tutorial deals with pump cavitation, discussing various net positive suction head required (NPSHR) criteria, net positive suction head available (NPSHA) margins and impeller life expectancy. It gives an introduction to the subject matter and provides insights on particulars like cavitation inception, 3 percent head drop, and 40,000 hours impeller life, as well as NPSH scaling laws. It further devotes attention to the effect of dissolved gases and thermal suppression (i.e., thermodynamic effect). With regard to numerical prediction capabilities the use of computational fluid dynamics (CFD) shall be discussed. Furthermore, guidance for cavitation damage diagnosis shall be given, including the peculiar aspects of various cavitation modes, the prediction of cavitation erosion rate, and assessment of impeller life expectancy. The tutorial will further address NPSHR criteria and NPSHA margin factors.
Calibration and optimization of the pumping and disinfection of a real water supply system
Maintaining a disinfectant residual in water distribution systems WDSs is generally considered paramount to ensuring a safe drinking water supply. This objective can be assisted by the use of booster stations to increase disinfectant concentrations throughout the network. However, identifying the appropriate dose at each station is an optimization problem. The aim is to minimize the total mass of disinfectant dosed and reduce the cost of disinfection along with potential taste, odor, or by-product problems, while maintaining a certain minimum residual in the network. The residual present in the water at any location is not only dependent on the amount of disinfectant added to the water, but also the hydraulics of the system and the resulting detention times. A number of previous studies have tackled this optimization problem, however, a review of current literature suggests that in many cases the hydraulics of the system have been held constant, or the WDSs considered were hypothetical systems with relatively few constraints. This study considers the booster disinfection dosing problem, including daily pump scheduling, for a real system in Sydney, Australia. Before the system can be optimized, a representative model is required to ensure useful results, and the many constraints on the daily operation system must be accounted for in the fitness function considered. The results from the optimization study indicate it is necessary to consider the hydraulics as well as the dosing regime in the optimization process, as cycling reservoir levels minimizes detention times, and hence, disinfectant residuals are maintained at the extremities of the network. Also, significant energy cost savings of up to 30% can be made by scheduling the pumping in the system in line with the off-peak electricity costs.
Energy Efficiency in the Water Industry: A Compendium of Best Practices and Case Studies – Global Report
Over the last decade, energy consumption by the water sector has increased considerably as a consequence of the implementation of new technologies to meet new potable water and effluent quality standards. The price of energy has also substantially increased and these increases will be compounded by the need for additional energy intensive processes to achieve more exacting regulatory requirements.
This Compendium draws together the best practice in energy efficient design and operation of water industry assets. The book identifies the developments and future opportunities by detailed examination of current best practice and technologies:
It illustrates incremental improvements in energy efficiency through optimisation of existing assets and operations. More substantial improvements in energy efficiency from the adoption of novel technologies. Successful case studies based on results of full scale operations. This compendium is an invaluable reference for water engineers, utility managers, and water and energy professionals.
Water and wastewater energy best practice guidebook
Water and wastewater energy best practice guidebook.