Chillers energy consumption, energy savings and emission analysis in an institutional buildings

Chillers consume more than 40% of the total energy used in the commercial and industrial buildings for space conditioning. In this paper, energy consumption by chillers and chilled water pumps, condenser pumps and fan motors has been estimated using data collected by a walkthrough energy audit for the 16 faculties of the University of Malaya. It has been estimated that chillers and motors and pumps used in chillers consume 10,737 MWh (i.e. 51% of total energy consumption) of electric energy for different percentage of loadings. As chillers are major energy users, variable speed drives are applied in chillers to reduce their energy consumption. It has been estimated that about 8368 MWh annual energy can be saved by using efficient chillers at different loadings. It has also been found that about 23,532 MWh annual energy can be saved for chilled water supply pumps, condenser pumps and cooling tower fan motors by matching required speeds using variable speed drives for 60% of speed reduction. About 1,274,692 kg of CO₂ emission could be avoided for using energy efficient chillers at 50% load. It has been also found that about 2,426,769 kg CO₂ emission can be reduced by using variable speed drives for 60% speed reductions. Payback periods found to be only few months for using variable speed drives in chilled water pumps, condensers and fan motors.     

Analysis of electrical motors load factors and energy savings in an Indian cement industry

Electric motors consume in between 30% and 80% of the total industrial energy use for few selected countries around the world. It was identified that many motors are operated under loaded conditions. In some cases, motors are operated even at 3-16% of their full loads. These low loads can be optimized with the application of variable speed drives (VSD) to match the load requirements. Based on the estimation, it has been found that annually about 1,865,925 MWh of energy can be saved for 60% speed reduction when VSDs are used. It was also found that about 2,122,675 tons CO₂emission could be avoided annually by using VSDs for Low Tension (LT) motors for 60% speed reduction. It was also estimated that annually about 4,600,386 MWh of energy can be saved for High Tension (HT) motors for 60% speed reduction using VSDs. The average payback period (PBP) for implementing VSDs for LT and HT motors found to be very low (i.e. about 2 days). In this particular study it is observed that installing both LT and HT capacitors to improve power factor found to be not economically viable owing to low level of energy savings.     

Efficiency trends in electric machines and drives

Almost all electricity in the UK is generated by rotating electrical generators, and approximately half of it is used to drive electrical motors. This means that efficiency improvements to electrical machines can have a very large impact on energy consumption. The key challenges to increased efficiency in systems driven by electrical machines lie in three areas: to extend the application of variable-speed electric drives into new areas through reduction of power electronic and control costs; to integrate the drive and the driven load to maximise system efficiency; and to increase the efficiency of the electrical drive itself. In the short to medium term, efficiency gains within electrical machines will result from the development of new materials and construction techniques. Approximately a quarter of new electrical machines are driven by variable-speed drives. These are a less mature product than electrical machines and should see larger efficiency gains over the next 50 years. Advances will occur, with new types of power electronic devices that reduce switching and conduction loss. With variable-speed drives, there is complete freedom to vary the speed of the driven load. Replacing fixed-speed machines with variable-speed drives for a high proportion of industrial loads could mean a 15–30% energy saving. This could save the UK 15 billion kWh of electricity per year which, when combined with motor and drive efficiency gains, would amount to a total annual saving of 24 billion kWh.     

Energy and emission analysis for industrial motors in Malaysia

The industrial sector is the largest user of energy in Malaysia. Industrial motors account for a major segment of total industrial energy use. Since motors are the principle energy users, different energy savings strategies have been applied to reduce their energy consumption and associated emissions released into the atmosphere. These strategies include using highly efficient motors, variable speed drive (VSD), and capacitor banks to improve the power factor. It has been estimated that there can be a total energy savings of 1765, 2703 and 3605 MWh by utilizing energy-efficient motors for 50%, 75% and 100% loads, respectively. It was also found that for different motor loads, an estimated US$115,936 US$173,019 and US$230,693 can be saved in anticipated energy costs. Similarly, it is hypothesized that a significant amount of energy can be saved using VSD and capacitor banks to reduce speed and improve the power factor, thus cutting energy costs. Moreover, a substantial reduction in the amount of emissions can be effected together with the associated energy savings for different energy savings strategies. In addition, the payback period for different energy savings strategies has been found to be reasonable in some cases.     

Applications of variable speed drive (VSD) in electrical motors energy savings

Most motors are designed to operate at a constant speed and provide a constant output; however, modern technology requires different speeds in many applications where electric motors are used. A variable speed drive (VSD) is a device that regulates the speed and rotational force, or output torque of mechanical equipment. Effects of applying VSDs are in both productivity improvements and energy savings in pumps, fans, compressors and other equipment. Variable speed drive technology and the importance of controlling the speed of existing motors have fascinated many attentions in the last years with the advent of new power devices and magnetic materials. This paper is a comprehensive review on applications of VSD in electrical motors energy savings. The aim is to identify energy saving opportunities and incorporated costs of applying variable speed drives to the existing applications of electrical motors. Subsequently, economic analysis, payback period and the effect of current and voltage harmonics generated by VSDs are presented. Authors are hopeful to provide useful information for future variable speed drive applications like fans, pumps, chillers, ventilators and heaters.     

Analysis of Jordan's industrial energy intensity and potential mitigations of energy and GHGs emissions

This paper aims to identify the main drivers behind energy intensity changes of the Jordanian industrial sector and to introduce the impact of energy efficient measures within the Jordanian industrial sector. To achieve these objectives, two empirical models were developed for electricity and fuel intensities, respectively of the Jordanian industrial sector based on multivariate linear regression. It was found that the structural effect, electricity prices, capacity utilizations and number of employees are the most important variables that affect changes of electricity intensity while fuel prices, capacity utilizations and number of employees factors are the most important variables that affect fuel intensity. The results show that multivariate linear regression model can be used adequately to simulate industrial energy intensity with very high coefficient of determination. Also, the impact of implementing energy saving technologies, such as use of high efficiency motors (HEMs), optimize motor size, variable speed drives (VSDs), bare steam pipes insulations, steam leak prevention, steam traps repair, and adjustment of boiler air/fuel ratio were investigated and found to be significant. Without such basic energy conservation and management programs, energy consumptions and associated GHG emissions for the industrial sector are predicted to rise by 25% and 23%, respectively in the year 2021. If these measures are implemented on a gradual basis, over the next decade, industrial energy consumption is predicted to rise at a lower rate, reaching 11.9% for same period with low/no cost actions. This would yield an estimated annual emission reductions of 570×10³ t. In addition, the total installed capacity cost savings is estimated to be around 81.9 million US$ by year 2021.     

Energy savings and emissions reductions for rewinding and replacement of industrial motor

Electric motors consume 30-80% of total industrial energy around the world. This study estimates the economic viability of replacing rewound and standard motors with high efficiency motors (HEMs) in the industrial sector. The efficiency of a motor is degraded when it is rewound and it is better to rewind a larger motor compared with a smaller motor. It was found that a HEM can save on average 5.5% of energy compared with a standard motor. In addition, the payback period was found to be reasonable when a motor is operated at a 50% load. HEMs will also save a sizeable amount of energy and reduce emissions. It was estimated that 67,868 MWh/year energy and US$ 4,343,531 per year could be saved by introducing HEMs. By contrast, 44,582 tons of CO₂, 333 tons of SO₂ and 122 tons of NO_x emissions could be reduced through the aforementioned energy savings. This study found that rewound motors of a larger size and HEMs are economically viable.     

Site‐specific Design Optimization of Wind Turbines

This article reports results from a European project, where site characteristics were incorporated into the design process of wind turbines, to enable site‐specific design. Two wind turbines of different concept were investigated at six different sites comprising normal flat terrain, offshore and complex terrain wind farms. Design tools based on numerical optimization and aeroelastic calculations were combined with a cost model to allow optimization for minimum cost of energy. Different scenarios were optimized ranging from modifications of selected individual components to the complete design of a new wind turbine. Both annual energy yield and design‐determining loads depended on site characteristics, and this represented a potential for site‐specific design. The maximum variation in annual energy yield was 37% and the maximum variation in blade root fatigue loads was 62%. Optimized site‐specific designs showed reductions in cost of energy by up to 15% achieved from an increase in annual energy yield and a reduction in manufacturing costs. The greatest benefits were found at sites with low mean wind speed and low turbulence. Site‐specific design was not able to offset the intrinsic economic advantage of high‐wind‐speed sites. It was not possible to design a single wind turbine for all wind climates investigated, since the differences in the design loads were too large. Multiple‐site wind turbines should be designed for generic wind conditions, which cover wind parameters encountered at flat terrain sites with a high mean wind speed. Site‐specific wind turbines should be designed for low‐mean‐wind‐speed sites and complex terrain. Copyright © 2002 John Wiley & Sons, Ltd.     

Assessing high wind energy penetration

In order to convincingly promote installing wind power capacity as a substantial part of the energy supply system, a set of careful analyses must be undertaken. This paper applies a case study concentrated on assessing the cost/benefit of high wind energy penetration. The case study considers expanding the grid connected wind power capacity in Praia, the capital of Cape Verde. The currently installed 1 MW of wind power is estimated to supply close to 10% of the electric energy consumption in 1996. Increasing the wind energy penetration to a higher level is considered viable as the project settings are close to ideal, including a very capable national utility company, Electra, a conventional power supply system based on imported heavy fuel and gas oil, and favourable wind conditions with an estimated annual average of 9.3 m/s at the hub height of the wind turbines. With the applied case study assumptions, simulations with WINSYS over the lifetime of the assessed wind power investment show that investments up to 4.2 MW are economically viable. The economic optimum is found at 2.4 MW reaching an internal rate of return of almost 8% p.a. This 2.4 MW of wind power would, together with the existing wind power, supply over 30% of the electric consumption in 1996. Applying the recommended practices for estimating the cost of wind energy, the life-cycle cost of this 2.4 MW investment is estimated at a 7% discount rate and a 20 year lifetime to 0.26 DKK/kW h.     

A review on compressed-air energy use and energy savings

Compressed-air systems account for about 10% of total industrial-energy use for few selected countries as found in literatures. Compressed air is typically one of the most expensive utilities in an industrial facility. This paper describes a comprehensive literature review about compressed air energy use, savings, and payback period of energy efficient strategies. This paper compiles latest literatures in terms of thesis (MS and PhD), journal articles, conference proceedings, web materials, reports, books, handbooks on compressed air energy use, efficiency, energy savings strategies. Computer tools for compressed air analysis have been reviewed and presented in this paper. Various energy-saving measures, such as use of highly efficient motors, VSD, leak prevention, use of outside intake air, reducing pressure drop, recovering waste heat, use of efficient nozzle, and use of variable displacement compressor to save compressed-air energy have been reviewed. Based on review results, it has been found that for an electric motor used in a compressed-air system, a sizeable amount of electric energy and utility bill can be saved using high efficient motors and applying VSDs in matching speed requirements. Also, significant amounts of energy and emission are reducible through various energy-saving strategies. Payback periods for different energy savings measures have been identified and found to be economically viable in most cases.     

Energy,economic and environmental benefits of using high-efficiency motors to replace standard motors for the Malaysian industries

Electric motors use major share (i.e. about 30–80% of total industrial energy consumption) of total industrial energy use around the world. Experiences from other countries show that government intervention in the form of regulations such as mandatory and voluntary approaches can save sizeable amount of energy along with the reduction in emissions associated with energy savings. This paper presents potential energy savings by introducing high-efficiency motors as a case study in Malaysian industrial sector. Emission reductions associated with the energy savings has been estimated and presented as well. It was also estimated that a cumulative amount of 1940 and 892 GWh of energy can be saved for 20 and 120 kW motors, respectively, in Malaysia relative to BAU over the next 10 years. Similarly, a cumulative amount of USD 100 million and USD 60 million can be saved as utility bills for the same motor categories. It has been found that the payback period of different capacities of motors are less than a year. Based on results, it was found that 1789 million kg of CO₂ emission can be avoided by replacing standard motors with high-efficiency motors.     

An investigation of variable power collective pitch control for load mitigation of floating offshore wind turbines

This paper investigates the loads on offshore floating wind turbines and a new control method that can be used to reduce these loads. In this variable power collective pitch control method, the rated generator speed, which is the set point that the collective pitch control attempts to drive the actual generator speed towards, is no longer a constant value but instead is a variable that depends on the platform pitch velocity. At a basic physical level, this controller achieves the following: as the rotor of a floating turbine pitches upwind, the controller adjusts so as to extract more energy from the wind by increasing the rated generator speed and thus damps the motion; as the rotor pitches downwind, less energy is extracted because the controller reduces the rated generator speed and again damps the motion. This method is applied to the NREL 5 MW wind turbine model, in above rated conditions where the platform motion is most problematic. The results indicate significant load reductions on key structural components, at the expense of minor increases in power and speed variability. The loads on the blades and tower are investigated more generally, and simple dynamic models are used to gain insight into the behavior of floating wind turbine systems. It is clear that for this particular design, aerodynamic methods for reducing platform motion and tower loads are likely inadequate to allow for a viable design, so new designs or possibly new control degrees of freedom are needed. Copyright © 2012 John Wiley & Sons, Ltd.     

Energy,exergy and economic analysis of industrial boilers

In this paper, the useful concept of energy and exergy utilization is analyzed, and applied to the boiler system. Energy and exergy flows in a boiler have been shown in this paper. The energy and exergy efficiencies have been determined as well. In a boiler, the energy and exergy efficiencies are found to be 72.46% and 24.89%, respectively. A boiler energy and exergy efficiencies are compared with others work as well. It has been found that the combustion chamber is the major contributor for exergy destruction followed by heat exchanger of a boiler system. Furthermore, several energy saving measures such as use of variable speed drive in boiler's fan energy savings and heat recovery from flue gas are applied in reducing a boiler energy use. It has been found that the payback period is about 1 yr for heat recovery from a boiler flue gas. The payback period for using VSD with 19 kW motor found to be economically viable for energy savings in a boiler fan.     

Modeling and analysis of variable speed single phase induction motors with iron loss

Despite their usual low power ratings of single phase induction motors, they consume a considerable part of total motors energy consumption due to their large and ever-increasing quantity. The recent rising of oil prices and environmental crises has fortified the idea of energy saving practices in all applications; particularly in single phase induction motors due to their typical low efficiency. An essential requirement for this practice is the modeling and analysis of machine electrical losses under variable frequency operation. In this paper an improved steady state model of single phase induction motors is derived to investigate major motor characteristics like torque–speed, input power, output power, etc. A special emphasis is placed on accurately representing core losses at variable frequency. The winding currents phase difference is reintroduced as a fundamental motor variable to determine motor performances including losses and efficiency. An advanced computerized motor test setup is designed and built for on-line measurement of motor characteristics at different supply and operating conditions. The extensive experimental results, in good agreement with the simulation results based on the mentioned analysis, confirm the validity of the proposed model.     

基于热电互动的分布式能源系统优化研究

  [目的]  为实现分布式能源系统经济、高效的为工业用户供能,基于工业园区电、热负荷的耦合特性,建立了分布式能源系统供能单元的性能模型,提出了优化运行策略。  [方法]  以广州某工业园区为研究对象,结合实际负荷数据,合理确定优化参数,计算了年发电量、年耗气量和一次能源利用效率,并对负荷增量的影响进行了研究。  [结果]  结果表明:机组启动热负荷对分布式能源系统的年发电量影响较大,采用优化运行策略,年发电量提升约18.7%,可以提高园区自供电比例,一次能源利用效率在85%以上。  [结论]  该优化运行策略是正确并有效的,可应用于热电耦合分布式能源系统的优化,有效提升分布式能源系统的供能,同时维持较高的一次能源综合利用效率。     

Optimal and energy efficient operation of conveyor belt systems with downhill conveyors

Downhill conveyors are important potential energy sources within conveyor belt systems (CBSs). Their energy can be captured using regenerative drives. This paper presents a generic optimisation model for the energy management of CBSs that have downhill conveyors. The optimisation model is able to optimally schedule three configurations of a case-study CBS that is connected to the grid and operated under a time-of-use tariff. The three suggested drive configurations showcase potential energy savings/incomes that can be obtained from implementing: (a) variable speed control, (b) internal use of downhill conveyor energy and (c) the export of energy to the grid. The results show that a CBS with a daily energy consumption of 924 kWh can be reconfigured and controlled to reduce consumption by 53 or 100 % or be made to generate 1984 kWh, depending on the configuration. Analysis of the investment in each of the three configurations is assessed using a life-cycle cost and payback period (PBP). The daily operation simulation results show that the use of regenerative drives and variable speed control is able to provide energy savings in CBSs. The cost analysis shows that the configuration that enables sale of energy to the grid is the most profitable arrangement, for the case study plant under consideration. The sensitivity analysis indicates that the PBPs are more sensitive to the annual electricity price increases than changes in the discount rate. Combining regenerative drives and optimal operation of CBS generates energy savings that give attractive PBPs of less than 5 years.     

Adjustable speed drives improve circulating water system

This paper illustrates the integration of electrical and mechanical engineering requirements to produce a solution to past problems and future operating demands. The application of adjustable speed drives in the modifications or the circulating water system at Indian Point No. 3 nuclear power plant provided increased operating flexibility, efficiency and avoided otherwise costly renovations to the plant electrical system. Rectification or the original inadequate design of the circulating water system, in addition to maximizing plant efficiency consistent with environmental considerations, formed the basis for this modification. This entailed replacement of all six circulating water pumps and motors and physical modifications to the intake system. This paper details the methodology used in this engineering task. The new system was installed successfully and has been operating reliably and economically for the past eight gears     

Biomass fired small-scale CHP in Sweden and the Baltic States: a case study on the potential of clustered dwellings

Sweden as well as the three Baltic states has an abundant supply of biomass, mostly wood waste. Much of it goes into district heating (DH), which has expanded continuously since the first system started 50 years ago. DH now accounts for 43% of the heating consumption and a further expansion is possible in many directions. Firstly existing DH systems can be enlarged, secondly DH can be upgraded to combined heat and power (CHP) to a much larger extent, thirdly new DH (and CHP) systems can be implemented in many smaller places down to 1000 inhabitants or less. The last alternative, biomass and especially pellets fired small-scale cogeneration in combination with local heating networks, is the topic for this paper. It presents a method to estimate the potential for small-scale DH and CHP and results from a “test” area in southeast Sweden. The method estimates local heat demand using databases with individual and statistical property data. It identifies areas with clusters of buildings where the heat demand is enough to implement decentralized small DH networks if possible in combination with small-scale CHP. In the event for Swedish circumstances very sparsely populated test area of 36×48 km² with around 8000 inhabitants, the total heat consumption in residential buildings is estimated to 84 GW h. When we have identified the areas with clusters of buildings, we have set the minimum heat consumption in such an area to 500 MW h. The area size is varied in 250 m steps from 250×250 m² to 1000×1000 m². For the four area sizes, the method then identifies and locates 30, 38, 38,30, respectively, clustered areas with a potential for small-scale DH and CHP worth investing closer.     

An investigation of variable power collective pitch control for load mitigation of floating offshore wind turbines

This paper investigates the loads on offshore floating wind turbines and a new control method that can be used to reduce these loads. In this variable power collective pitch control method, the rated generator speed, which is the set point that the collective pitch control attempts to drive the actual generator speed towards, is no longer a constant value but instead a variable that depends on the platform pitch velocity. At a basic physical level, this controller achieves the following: as the rotor of a floating turbine pitches upwind, the controller adjusts so as to extract more energy from the wind by increasing the rated generator speed and thus damps the motion; as the rotor pitches downwind, less energy is extracted because the controller reduces the rated generator speed and again damps the motion. This method is applied to the NREL 5 MW wind turbine model, in above‐rated conditions where the platform motion is most problematic. The results indicate significant load reductions on key structural components, at the expense of minor increases in power and speed variability. The loads on the blades and tower are investigated more generally, and simple dynamic models are used to gain insight into the behavior of floating wind turbine systems. It is clear that for this particular design, aerodynamic methods for reducing platform motion and tower loads are likely inadequate to allow for a viable design, and so new designs or possibly new control degrees of freedom are needed. Copyright © 2012 John Wiley & Sons, Ltd.     

凝结水泵的最佳调节方案分析

为研究变频调速技术在200MW凝汽机组凝结水泵调节中应用的节能效果，分别按照由机组承担的负荷、除氧器运行方式及调节形式形成的6个方案进行计算分析。首先，由管路性能曲线和泵特性曲线取得各工况点的流量、扬程和效率，椐此并利用电动机和变频器的效率等获得凝结水泵消耗的电功率和全年运行时间段的耗电量，最后可有进行方案比较分析的年费用值。在各方案中采用变频调速方式相对于节流调节方式耗电量要小；调峰负荷下的各种方案要比对应基本负荷的情况耗电量和年费用小；调峰负荷时除氧器滑压运行方式下的变频调速方案是最经济方案。结果表明，虽然凝结水泵的变速调节方式初投资较高，但在各运行工况特别是启停和非设计工况节能潜力巨大，可延长设备寿命，有较强的经济效益，推广应用性强。图4表1参6