Variable Speed Pumping System Research Articles

Evaluation of variable speed pumps in pressurized water distribution systems

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.

Optimal diameter of district heating pipe network based on the hybrid operation of distributed variable speed pumps and regulating valves

The district heating system that uses the hybrid operation of distributed variable speed pumps and regulating valves can effectively reduce the pressure level at the far-end of the heating network, while retaining the energy saving advantages of the distributed variable speed pump system and ensuring the safe operation of the heating network. In this study, pipe network optimization based on genetic algorithm was used to determine the pipe diameter required for the hybrid operation of distributed variable speed pumps and regulating valves. A mathematical model was established to evaluate the economic efficacy based on the annual equivalent cost. The zero-pressure difference point was evaluated to optimize the pipe diameter. A real pipe network was assessed to evaluate the efficacy of the method, and a sensitivity analysis of pressure constraints and economic factors was conducted. Our results show the system of hybrid operation of distributed variable speed pumps and regulating valves can reduce the annual equivalent cost by about 10.35% compared to the conventional central circulating pump system. In addition, the annual energy consumption due to heat loss and pump operation is only 0.36% higher than that of the conventional central circulating pump system.

EVASOR, an Integrated Model to Manage Complex Irrigation Systems Energized by Photovoltaic Generators

The carbon footprint and energy cost of irrigation are increasing due to the modernization of irrigation systems, which also necessitates highly efficient use of water resources. Alternatives to conventional energy sources to power irrigation systems are renewable sources, primarily photovoltaic energy. Photovoltaic energy has the main disadvantage of producing a highly variable amount of energy, which affects the irrigation uniformity. Modeling irrigation systems in an integrated manner generates useful information about system performance for technicians that helps in the decision-making process. The EVASOR (EVAluation of SOlar iRrigation systems) model integrates different modules to simulate the whole solar irrigation system using a holistic approach: (1) I-Solar, which simulates the instantaneous power generated by the photovoltaic system, (2) AS-Solar, which simulates the variable speed pumping system, (3) Solar-Net, which simulates the hydraulic performance of the water distribution network, and (4) PRESUD-Irregular, which determines the discharge and pressure of all the emitters of the subunits together with irrigation quality parameters (coefficient of uniformity (CU), emission uniformity (EU), and coefficient of variation of the emitter discharge in the subunit (CVq) for any pressure at the subunit inlet. The integrated model EVASOR determines the irrigation quality parameters of complex irrigation systems with information on irradiance, air temperature, wind speed, and water table level for any combination of open subunits. To validate the model, results are presented regarding a case study located in southeast Spain.

Experimental and numerical optimization on chilled water configuration for improving temperature performance and economic viability of a centralized chiller plant

This research aimed to simulate and optimize chilled water circuit system of a central air conditioning plant applied for a five-star hotel in Bali Island, Indonesia. This optimization was performed because temperature of chilled water distributed to the loading system could not satisfy room temperature requirement. Detailed measurements have been taken on the AC system included refrigeration system of the chillers, chilled water and cooling water distribution, cooling load, heat rejection and pumping systems. Thermodynamic analyses on the system energy performance were carried out. Numerical simulations were also established to evaluate chilled water flow rate in the primary and secondary circuits. The measurement and simulation results showed there was unbalanced chilled water flow rate between primary and secondary circuits and the chilled water flow rate did not comply with rule of flow ‘primary flow must always be equal to or greater than secondary flow’ resulted in the cooling load coils lost their cooling capability. Optimization on the chilled water flow rate between primary and secondary circuits by implementing variable speed pumping system incorporated balancing valve was estimated to be potentially improve temperature performance and economic viability of the chiller plant operation.

A new preset refueling mode for gasoline dispenser using frequency converter and flow rate signals

Fuel dispenser is an integrated fuel pumping and metering system for automotive refueling at the service station. In this paper, we develop a preset refueling mode for the dispenser. A frequency converter and the flow rate signal from the measurement transducer are utilized instead of the solenoid valve, which is used to control the flow rate in the traditional refueling mode. With variable speed pumping system, the rotational speed of the pump is adjusted to achieve the desired flow rate and head necessary for the application. All the experiments were operated on a real dispenser system. How the frequency influences the refueling accuracy is observed. Through choosing a suitable frequency, not only accuracy but also energy efficiency improves compared with the traditional refueling mode. It is able to provide a reference for authority to fill in gaps in low-quantity (less than 5 L) refueling.

Energy Savings Potential for Pumping Water in District Heating Stations

In district heating stations, the heat carrier is circulated between the energy source and consumers by a pumping system. Fluid handling systems, such as pumping systems, are responsible for a significant portion of the total electrical energy use. Significant opportunities exist to reduce pumping energy through smart design, retrofitting, and operating practices. Most existing systems requiring flow control make use of bypass lines, throttling valves or pump speed adjustments. The most efficient of these options is pump speed control. One of the issues in using variable-speed pumping systems, however, is the total efficiency of the electric motor/pump arrangement under a given operating condition. This paper provides a comprehensive discussion about pump control in heating stations and analyzes the energy efficiency of flow control methods. Specific attention is also given to the selection of motor types, sizing and pump duty cycle. A comparative energy analysis is performed on the hot water discharge adjustment using throttling control valves and variable-speed drives in a district heating station constructed in Romania. To correlate the pumped flow rate with the heat demand and to ensure the necessary pressure using minimum energy, an automatic system has been designed. The performances of these control methods are evaluated in two practical applications. The results show that approximately 20%–50% of total pumping energy could be saved by using the optimal control method with variable-speed pumps. Additionally, some modernization solutions to reduce the environmental impact of heating stations are described.

벡터 제어 인버터 구동 원심펌프시스템의 에너지 절감 평가

    인버터 구동 원심펌프시스템   운전효율   가변속 운전   에너지 절감율  펌프 사용율The purpose of this study is to achieve energy saving effect of inverter driving multistage centrifugal pump. For determining the operation points in the pump system, the system curves should be obtained experimentally. To get the system curves, three pumps combined in parallel and one pump operated with different rotational speeds. But for variable speed pump system, energy saving rates can not be evaluated from operation efficiencies. That is why operation efficiencies, system curves, duty cycles, and input powers of the pump system were measured by the constructed experimental apparatus. The duty cycle segmented into different flow rates and weighting the average value for each segment by the interval time. The system was operated with two different periods. The mean duty cycles were collected from apartment and found that the system operated at 40% and at 50% or below capacity. Measured energy saving rate was 58.16%. Estimating method of energy saving rate could be more effective operation index than that of operation efficiency.

Application of Water Pump Proportionality Law to Heating and Air Conditioning Systems

Make an analysis and points out that the engineering conditions of variable speed working condition of water pump in line with the proportionality law are as follows: non-back-pressure system, all parallel pumps changing speed synchronously (including a single variable speed pump system) and fixed pipeline characteristic curve. Energy saving effect analysis of variable speed pumps should be based on the energy consumption comparison of the pump variable speed control to other flow control methods in conditions of achieving the same flow, but not to the design working condition.

Assessing variable speed pump efficiency in water distribution systems

Abstract. Energy savings and greenhouse gas emission reductions are increasingly becoming important design targets in many industrial systems where fossil fuel based electrical energy is heavily utilised. In water distribution systems (WDSs) a significant portion of operational cost is related to pumping. Recent studies have considered variable speed pumps (VSPs) which aim to vary the operating point of the pump to match demand to pumping rate. Depending on the system characteristics, this approach can lead to considerable savings in operational costs. In particular, cost reductions can take advantage of the demand variability and can decrease energy consumption significantly. One of the issues in using variable speed pumping systems, however, is the total efficiency of the electric motor/pump arrangement under a given operating condition. This paper aims to provide a comprehensive discussion about the components of WDS that incorporate variable speed pumps (including electric motors, variable frequency drives and the pumps themselves) to provide an insight of ways of increasing the system efficiency and hence to reduce energy consumption. In addition, specific attention is given to selection of motor types, sizing, duty cycle of pump (ratio of on-time and time period), losses due to installation and motor faults. All these factors affect the efficiency of motor drive/pump system.

Variable speed pumping for submersible wastewater pumping systems

Where variable speed pumping systems are under consideration for a specific application, such as for a wastewater lift station, designers and end users need to understand and take into account various factors and design criteria in order to make an informed decision. In this article from the USA, Charles G. Stolberg, Executive Director of the Submersible Wastewater Pump Association, describes some of the contributing components of the variable speed pumping system and how they interact with certain other components, and provides information to properly evaluate the advantages and disadvantages of applying such a design to submersible pumping equipment.

主機冷却可変量ポンプシステムとその省エネルギーの実績

We firstly introduce a variable speed pump system as an example of the energy saving in the ships and an outline of the development.We chiefly mention in this paper the results of performance test of the first unit at sea trial and the actual running performance at the first voyage of the ship.Furthermore, we refer to some notical points in case of the installation of this unit on board and the wide applications of this energy saving system.