Energy savings and better performances through variable speed drive application in desalination plant brine blowdown pump service

Motors are the single largest users of electric power, consuming over half of all electricity and more than 60% of that used in the industrial sector. The use of energy-efficient motor technologies offers utilities the possibility of achieving substantial energy savings and reduction of GHG emissions. This paper presents a comprehensive literature review about energy efficiency opportunities and savings potential for electric motor. This paper compiles latest literatures in terms of journal articles, conference proceedings, web materials, reports, books, handbooks on electrical motor energy use, and opportunities for energy efficiency as well as energy savings strategies. Besides, present status of the efficient motor technology, market potential have been presented in this paper. Also, different energy savings strategies such as rewinding, use of variable speed drive (VSD), and capacitor bank to improve the power factor to reduce their energy uses have also been reviewed. Furthermore, cost parameters to carry out economic analysis and payback period for different energy savings strategies have been shown as well. DOI: http://dx.doi.org/10.11591/ijece.v3i4.3592

Scale formation and fouling problems effect on the performance of MSF and RO desalination plants in Saudi Arabia

In this paper, we present the energy-saving potential of using optimized control for centrifugal pump–driven water storages. For this purpose, a Simulink pump-pipe-storage model is used. The equations and transfer function for steady-state and transient system behavior are presented and verified. Two different control strategies—optimum constant flow rate and level guided speed control—are compared to an allegedly optimal-driven pump with constant rotational speed. Twelve centrifugal pumps between 1 and 120 kW nominal power are evaluated to analyze the influence of different system parameters. The system characteristics, which are the static head, dynamic head factor, and maximum filling head, are varied 25 times for each pump in consideration of the pump’s best efficiency point. Thus, 300 different systems are optimized for each control strategy and compared to the constant speed control. The results are analyzed and the relevant system’s parameters, which have the most significant impact on energy savings, are shown. This theoretical energy–saving potential is verified with measurements, which show the high impact of the part load losses of the frequency converter and the electric motor. A law for identifying and estimation potential energy savings is developed using this information. Four use cases are analyzed with this law. It is shown that for a cost-minimal operation, not only the savings potential but also the operating time is decisive.

The 3 C’s Cash - Control - and Coordination based on the use of variable speed drives in the Citrus Industry is covered in this paper. Proper use of variable speed drives results in more money (CASH) from Energy Savings, Reduced Maintenance cost, and Improved Efficiencies. By regulating the speed of pumps and conveyor belts, less problems from mismatched speeds occur (CONTROL). The timing of the material reaching the correct location through proper speeds of equipment means improved COORDINATION. The various types of variable speed drives and their manufacturers are discussed. The type of drives covered range from simple eddy current, with minimum control features, to electronic AC and DC drives with unlimited control functions. Paper published with permission.

Solution of vibration problems in the electric motors and centrifugal pumps is important for proper operation and performance. Excessive vibrations seen in the electric motors and centrifugal pumps shorten the life of the machine and lead to the mechanical fatigue and even to damage of the machine. The causes of these vibrations in the electric motors and centrifugal pumps may be mechanical, fluid-borne or electromechanical [1]. Many of the mechanical and electromechanical-borne vibrations are directly related to the machine speed and can be determined by vibration analysis [2]. It is necessary to carry out the measurements in order to determine the source of vibrations. The source of the vibration can be determined by examining the relationships among data obtained from these measurements in the time and frequency domains. Imbalance is one of the vibration sources in the electric motors and centrifugal pumps. The main causes of this problem in the electric motors and the pumps are: defects during manufacturing, corrosion in the pump fan, partial permanent pollution of the pump fan blade, the unbalanced mounting of one of the pump bearings carrying the whole loads of pump fan, improper mass distribution in the rotor arms and blades of the electric motor, the bending of the pump and electric motor shaft. The imbalance problem encountered in electric motor and centrifugal pumps causes negative eects on pump

The result of a technical-economic survey of energy usage by centrifugal pumping equipment in the United States is presented. The possibility of significant energy savings in at least four key pumping categories is discussed. Methods of improving pump and system efficiencies in order to effect these savings are given. The present and future economics of enhanced pumping efficiencies are also considered. I. Introduction R ECENT dramatic rises in the cost of energy, along with concerns over future energy supplies in the United States, dictate that all types of machinery and systems be carefully examined for possible energy savings. One of the most common types of machinery in use is the pump. Only electric motors are more numerous,1 and over half of these above one horse-power are used to drive pumps.2 Thus, pumping equipment clearly represents a major consumption of energy and the apparent possibility of significant energy savings in the future. Centrifugal pumps are at the focus of the present study because of their commanding numbers relative to other pump types,3 and because they are utilized across a broad range of sizes, power inputs, and efficiencies. A centrifugal pump imparts energy to a liquid through the work done by a rapidly rotating vaned impeller. Some fraction of the impeller energy appears as increased pressure or head in the liquid discharged by the pump. Centrifugal pumps are thus distinct from rotary and reciprocating pumps, which involve a positivedisplacement action rather than an impeller, and from compressors, fans, and blowers, which impart energy to gases rather than to liquids. This paper concerns a study aimed at defining a national program in energy-effici ent pump utilization. The study includes a broad technical-economic survey of energy usage by pumps in the United States, followed by technical analysis and performance testing to identify the means by which significant national energy savings are possible. Portions of the study are still in progress and will be fully reported on at a later date.4

This paper presents the development of secondary controlled hydraulic pressure forming of sheet metal for both potential energy saving and electric motor power consumption reduction. Most of the reported existing pressure forming processes have limited pressure application and are mostly used for batch production. Above all, none of the existing processes use hydraulic accumulator and hydraulic transformer to save and reuse the energy or convert the system pressure and flow to the predetermined load requirement which could prevent wrinkling and fracture effect caused by low and unduly high pressure. Instead, most of the processes throttle excess fluid that is not required back to the reservoir thereby wasting excess motor energy as well as generating heat to the system. The resultant effect been the use of much energy during metal forming operation that leads to enormous financial lost to companies. It was as a result of these problems that the research was carried out. This development uses two secondary units (the hydraulic transformer) to transform a low pressure/high fluid flow into a high-pressure/low fluid flow. The use of variable speed drive (VSD) unit prevents pressure surges and ensures smooth starting and stopping of the machine. The hydraulic punch unit coupled to the hydraulic cylinder (ram) on a single action stroke performs the forming operation when the cylinder rams strikes. During ram retraction, the system saves and recycles both the hydraulic energy and generated heat back into the accumulator. The highly pressurized fluid generates a force of about (1500kN) which is used to power the punch piston for steel forming of thickness between 1.00mm-2.5mm. This operation leads to mass production of high strength, quality surface textured metallic parts within a second. The system simulation is performed using SIMULINK. The experimental results does not only agree with theoretical analysis but also appears to prove that the system is very efficient in energy saving and recuperation.

Centrifugal pumps are widely used in moving liquids from one location to another in homes, offices and industries. Due to the ever increasing demand for centrifugal pumps it became necessary to design and construction of a two-stage centrifugal pump. The pump consisted of an electric motor, a shaft, two rotating impellers, two stationary diffusers, suction and discharge nozzles and stuffing boxes. The pump was constructed using locally available materials and technology. It was then assembled and tested. Tests results showed that the pump performed satisfactorily. The pump had a capacity of 14.7 m3/hr and developed a head of 22.4 m at the design point. The pump is easy to use and can be maintained locally. Keywords: Centrifugal pump , electric motor, discharge nozzles, impellers

Saving of energy and cost in seawater desalination with speed controlled pumps

This paper investigates the influence of the volute geometry on the hydraulic performance of a low-specific-speed centrifugal pump using numerical simulations. The performance characteristics for the pump with the volute geometry designed using the constant velocity method show a significant discrepancy between the design point and the best efficiency point (BEP). This design methodology also results in a relatively flat head–capacity curve. These are both undesirable characteristics which can be mitigated by a reduction in the volute throat area. This design methodology also leads to a reduction in the power consumption and an increase in efficiency, especially at underload and design flow conditions. These impacts of the volute throat area on performance characteristics are investigated in terms of the change in internal flow characteristics due to the reduction in the volute throat area. Another aspect of the study is the impact of the width of the volute gap on performance characteristics. A reduction in the gap width results in a nearly vertical shift of the head–capacity curve, so that head delivered is higher across all the flow rates as the gap width is reduced. This is also accompanied by a slight improvement in efficiency under design flow and overload conditions. Numerical simulations are used to relate the change in performance characteristics with internal flow characteristics.

An end-use energy analysis in a Malaysian public hospital

The problem of fresh water lack can be solved my desalination of the seawater. Desalination of the seawater can be accomplished by several methods. Distillation of the seawater is one of the most promising among them. Comparative analysis of distillation desalination plant requires certain criteria. This criterion must take into account both energy consumption and seawater salinity. Relation of the minimal work required for seawater desalination to energy consumption was selected as such criterion. Four types of the distillation plants were considered: Multi-effect distillation plants (MED), multi-effect distillation plants with mechanical vapor compression (MVC) plants, MVC desalination plants have the best multi-effect distillation plant with thermal vapor compression (TVC) plants and Multistage flash distillation plants (MSF). MSF plants gave dependency that their efficiency rise along the gain ratio. That may be explained by the fact that its steam consumption does not depend on seawater consumption. TVC plants have slightly higher efficiency than MED plants. Thus, MVC plants can be recommended to use if there is no heat source, MSF plants - if there is heat source and plant must have a high gain ratio and TVC plant in the rest cases.

Many coastal areas in the Gulf experience a rapid industrial and urban growth. This development is sustained by an increasing number of seawater desalination plants in the region which satisfy the growing demand for fresh water. The combined seawater desalination capacity in the Gulf countries exceeds 11 million cubic metres per day and accounts for 45% of the total world capacity. The predominating process is multi-stage flash distillation (MSF), whereas only a minor amount of the drinking water is produced by reverse osmosis (RO) plants and other processes (together < 15%). Due to their waste water discharges to the sea, desalination plants - and especially MSF plants - must be considered a main source of pollution in the Gulf. It is estimated that the combined discharge of all MSF plants in the Gulf amounts to a waste water flow of about 1,000 m3 per second - which is the equivalent of a major river. This waste water is characterised by increased salinity and elevated temperature. It additionally contains substantial amounts of chemical pollutants, such as chlorine (which is used for biofouling control in the plants), antiscalants (which are used for scale inhibition) and heavy metals (which are present due to corrosion). This paper gives an overview on the waste water characteristics of the two main desalination processes (MSF, RO), presents estimates of total chemical discharges to the Gulf for two selected pollutants (chlorine, copper) and discusses the potential impacts of seawater desalination activity on the Gulf’s marine environment.

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.

Energy, exergy and economic analysis of industrial boilers