Electracation

The area

23.27 Compensation in Power Systems

Electrical power demand is growing at a great rate day by day and the generation is, in general, not able to cope up with the demand. Several ways of increasing the power generation are investigated including many nonconventional modes. Again, transmission of increased power over the existing lines is considered to meet the increasing demand as laying of new lines and acquisition of right of way are too expensive in developed areas. This necessitated the implementation of compensation in power systems. For many years, series and shunt compensators are in use. Electrical energy cannot be stored in bulk quantities. There must always exist a balance between generation and demand.

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Wind-powered Electricity Generation on Lundy Island

D.G. Infield, J. Puddy, in Energy for Rural and Island Communities: Proceedings of the Third International Conference Held at Inverness, Scotland, September 1983, 1984

THE ELECTRICAL SUPPLY SYSTEM

Electrical power is provided on an interrupted basis. The guaranteed period of supply is from 7 am to 12 noon, and 4 pm until midnight. Conventional generation plant consists of three 6 kVA single-phase Lister diesel generator sets, and one 27 kVA three-phase unit. The original distribution system consisted of two separate single-phase radial feeders and one single-phase ring main. Underground cables are used throughout. A switchboard in the generator house allows each circuit to be run individually with its own single-phase set, or in groups, or from the three-phase set. The run of these distribution cables is shown in Fig. 2.

Fig. 2. South Lundy electrical services

(from Somerville and Puddy, 1983)

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Road Transport

JS Davenport, ... MJH Chandler CEng, FIEE, FICE, FIHT, in Electrical Engineer's Reference Book (Sixteenth Edition), 2003

44.2.5 Power supply

Electrical power is normally obtained from the local electricity supply company; in the UK this is normally at 11 kV a.c. Substations comprising transformer/rectifier units convert this to a lower voltage d.c. This is supplied to the overhead system at a voltage not exceeding 750 V d.c. on the street-running sections, although 1500 V d.c. may be used on segregated sections of the line.

The visual impact of the overhead-line equipment is greatly reduced by the use of insulated support wires made from Parafil which eliminates the need for obtrusive insulators. Wires can also be attached to existing buildings to obviate the need for separate poles. The minimum wire height on street-running sections in the UK is 5.5 m in order to provide safe clearance above other road traffic, but may be reduced to about 3.8 m on fully segregated sections.

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Flocculation and electroflocculation for algal biomass recovery

Tawan Chatsungnoen, Yusuf Chisti, in Biofuels from Algae (Second Edition), 2019

6.4 Costs

Electrical power and the sacrificial anode are the main consumables in an electroflocculation process [94]. Power consumption depends substantially on the operating conditions, including the current density, the electrode type and number, the surface area of the electrodes, the electrode spacing and the duration of operation [95]. The relationship between electrical power consumption (Pe, W), the applied voltage (U, V) and current (I, A) is as follows:

(3)Pe=UI

In terms of the resistance R (ohm) to flow of the electrical current between electrodes, the power consumption can be shown to depend on the electrical current, as follows:

(4)Pe=RI2

Thus, the power consumption depends strongly on the current density. For a fixed current density, power consumption can be reduced by reducing the electrical resistance R, for example, by reducing the distance between the electrodes or increasing the electrical conductivity of the culture medium [94].

The total cost of harvesting the marine microalga Tetraselmis sp. by electroflocculation has been estimated to be US$0.19 kg− 1 of biomass, or $190 per metric ton [38]. This included the cost of electricity, the replacement of anodes, and a 10% annual depreciation for a facility with a potential biomass processing capacity of 57,480 metric tons per annum [38]. Electricity usage contributed 49.2% to the total operational cost, whereas the contributions of electrode replacement and capital depreciation were 37.3% and 13.5%, respectively.

Table 4 compares the cost of harvesting of microalgae by some of the methods available. According to this table, harvesting by electroflocculation appears to be cheapest, but conventional flocculation combined with sedimentation is relatively cheap compared to the other methods.

Table 4. Cost comparison of different microalgae harvesting methods

Harvesting methodYearUS $ per metric ton of dry biomassItems included in costingReferenceOriginal2017aCentrifugation (self-cleaning disc separator)199517102755Plant depreciation, maintenance and energy[22]Flocculation with flotation198813901889Plant depreciation, maintenance, flocculant and energy[22]Flocculation with sedimentation1988370768Plant depreciation, maintenance, flocculant and energy[101]Electroflocculation2012190203Plant depreciation, electrode consumption and energy[38]

aUS inflation was calculated from http://www.usinflationcalculator.com.

Source: Modified from A.K. Lee, D.M. Lewis, P.J. Ashman, Harvesting of marine microalgae by electroflocculation: the energetics, plant design, and economics, Appl. Energy 108 (2013) 45–53.

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Preconditions of Successful (Gastrointestinal) Surgery

Armin Schneider, Hubertus Feussner, in Biomedical Engineering in Gastrointestinal Surgery, 2017

4.3.9 Structural Preconditions

The highly specialized workplace "surgical OR" requires the consideration of hygienic, climatic, energy-providing, etc. aspects [9].

Electrical power supply plays a central role in modern hospitals, since most devices are electrically powered and must be ready for operation with highest availability. Therefore, already hospitals of average size are supplied with high-voltage current directly from the electricity supplier.

To guarantee the safety of the patients and for retention of the functional capability of the hospital, technical arrangements are required by law to ensure that essential devices can still operate for at least 24 hours with loss of the central electric power [10]. The most reliable electrical power supply is necessary for OR lamps and all medical-technical devices which are necessary for maintaining vital functions [11]. Therefore, typically two different emergency power systems are installed in hospitals: uninterruptible power supply (UPS, battery-based) and generators, usually diesel engine driven.

The battery backup provides uninterrupted power to critical lifesaving devices while the generator needs about 15 seconds to start up. To reduce load on the UPS, in hospitals red colored outlets indicate that they are on the battery backup current supply (Fig. 4.28A).

Figure 4.28. (A) Battery- or generator-based current can be identified by the red signal color (arrows); (B) terminal wall outlets (gases).

All from MITI.

Contemporary ORs are equipped with piped medical gas and vacuum systems. The supply of oxygen, nitrous oxide, and carbon dioxide comes from cylinder batteries whose size is based on the individual requirements. The central gas supply is typically located in an area where fresh supply from the provider can be carried out easily (Fig. 4.29) [12]. Compressed air is generated with compressors, driven by electric motors, additional dryers then withdraw the humidity. Filters and catalytic converters ensure an oil-free, medically pure compressed air. Finally, a pressure-relief valve reduces the air pressure to the required operating pressure.

Figure 4.29. Central gas supply of a modern hospital with an easy to reach channel of supply for big trucks.

From MITI.

The gases are passed through a branched pipe network. Gas outlets are either fitted flush on walls or as overhead booms (Fig. 4.28B). The terminal gas outlets are labeled and the connection probe assembly differs to avoid false connections. For the continuity of patient care with medical gases, pressure monitoring with optical and acoustical alarms is provided in all rooms connected to the central gas supply.

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New applications for submarine cables

Stephen Lentz, in Undersea Fiber Communication Systems (Second Edition), 2016

8.4.3 Electrical power safety

Electrical power safety is a vital concern for offshore oil and gas platforms where even the slightest electrical discharge can have disastrous effects. Accordingly, connection and earthing of submarine cable power conductors is approached very cautiously. This is the case even where the platform is connected via a branch cable which does not normally carry power feed current. There is some benefit to providing access to the cable center conductor, as it allows a secondary method of fault location (in addition to OTDR tests) and permits electroding tone to be applied to the cable. A suitable cable termination unit (CTU) and duplicated earth connections permit test access to the branch conductor. However, because these capabilities are rarely used, it is common practice to earth the cable center conductor in the wet plant before reaching the platform. These two methods of earthing a branch cable are shown in Figure 8.15. In the most common case where the platform is connected via an unrepeatered branch, the seabed earth unit has no impact on the system design. In the case of a repeatered segment, the segment must be single end fed. A branch segment with repeaters would require a PFBU.

Figure 8.15. Branch cable power safety.

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Reliability, Availability, and Maintainability (RAM Analysis)

DrEduardo Calixto, in Gas and Oil Reliability Engineering (Second Edition), 2016

Electrical Subsystem

The electrical power required for running the CENPES II and CIPD installations will be provided via a cogeneration subsystem with three motor generators powered by natural gas, with 3.5 MVA each, at 13.2 kV, three phases, 60 Hz, suitable for continuous generation of electrical power and to be located in the utility building. The electrical subsystem of the cogeneration plant will operate together with the local electrical power provider, Light SESA, which, during a downtime of the generation equipment for unscheduled maintenance, will immediately activate, without interruptions, the site's electrical load. Power supply by Light, at a tension of 13.2 kV, three phases, 60 Hz, will be used as power backup and to supplement demand.

It will be necessary to contract from Light two independent underground feeders. Both circuits, one a spare of the other, with automatic feed transfer, will be capable of meeting estimated initial load plus 25% for future expansion. There will be an emergency power supply system included for the three generators powered by diesel oil, feeding the electrical system, in the event of loss of power from main generators and Light.

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Underwater vehicles

In The Maritime Engineering Reference Book, 2008

10.4.4.3 Ac Versus Dc Considerations

Electrical power transmission techniques are an important factor in ROV system design due to their effect upon component weights, electrical noise propagation and safety considerations. The DC method of power transmission predominates the observation-class ROV systems due to the lack of need for shielding of components, weight considerations for portability, and the expense of power transmission devices. On larger ROV systems, AC power is used for the umbilical due to its long power transmission distances, which are not seen by the smaller systems. AC power in close proximity to video conductors could cause electrical noise to propagate due to EMF (electromotive force) conditions. The shielding necessary to lower this EMF effect could cause the otherwise neutrally buoyant tether to become negatively buoyant, resulting in vehicle control problems. And the heavy and bulky transformers are a nuisance during travel to a job site or as checked baggage aboard aircraft.

Larger work-class systems normally use AC power transmission from the surface down the umbilical to the cage (the umbilical normally uses fibre-optic transmission, lowering the EMF noise through the video) since the umbilical does not require neutral buoyancy. At the cage, the AC power is then rectified to DC to run the submersible through the neutrally buoyant tether that runs between the cage and vehicle.

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ENERGY CONSERVATION FOR A PROVINCIAL OFFICE BUILDING

G.D. McKenzie P. Eng., in Energy Developments: New Forms, Renewables, Conservation, 1984

ELECTRICAL

Electrical power is provided to the building from the city distribution system at 4160 volts feeding a 1500 KVA dry transformer located in the building basement.

Major electrics in the building operate on 600 volt power. Building lighting is primarily fluorescent at 347 volt.

The office lighting is somewhat unique and worth further comment. The fluorescent fixtures in the office area are hung directly from the vault ceiling shape produced by the structural ribs of the precast assembly. In general every second row of lighting is suspended above an eight inch round ventilation duct. The fixtures are twin lamp stacked vertically in the locations above the duct and single lamp where there is no duct. The fixture lens has an opaque bottom and clear sides thus projecting light primarily to the ceiling's surface.

Corridors are lit with conventional recessed lighting fixtures in a suspended ceiling. Lighting for the core traffic area, at the elevators is a luminous ceiling achieved by mounting fluorescent strip lighting behind luxon panels.

The glass stair towers are lit with incandescent lamps, one over each step.

The installed lighting level of the building was calculated at 130 KJ/hr m2. Delamping has reduced this considerably to the present level of about 70 KJ/hr m2 on average.

Switching of the office lighting is in relatively large blocks, i.e. four switches per floor. Hallway lighting is separated from the office space and stair towers. In the stair towers, lighting is arranged in six circuits per tower, each circuit picking up every 6th lamp.Publisher Summary

This chapter discusses the use of electrical energy apart from being used as a fuel. Electrical energy is used as a substitute for fuel and replaces it in many industrial applications. There are several sources by which electricity can be generated, for example, by conversion of chemical energy, potential energy, kinetic energy, nuclear energy, or by the use of electrolytic and fuel cells. The chapter also discusses that it is necessary to develop cells that would work on cheaper fuels and preferably on solid fuel, such as powered coal, to be really useful. This might be possible using fluidization techniques. An advantage of these techniques is that the efficiency of conversion of chemical to electrical energy is theoretically 100% because it does not involve heat at any stage. The chapter discusses generation of electricity in an alternator by rotating an assembly of conducting coils in magnetic field. It has been observed that electricity is also used in a few specialized metallurgical extraction techniques because the melting down time is much shorter in electric arc furnaces than in fuel-fired furnaces and the advantages of increased productivity outweighs the higher price of electrical energy.

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Electrical energy

W.T. Norris, in Information Sources in Energy Technology, 1988

Publisher Summary

The chapter discusses various sources of information regarding electricity generation .The most widely used form of energy is electrical energy, and the generation, distribution, and use of electrical energy is the theme of this chapter.. Specific topics covered include the generation and distribution of electrical energy for public consumption; consumer-owned generating systems; industrial installations; storage of electrical energy including batteries; and other aspects of electrotechnology. The most prominent source of industrial reports in electrical engineering is the Electric Power Research Institute in Palo Alto, California, which has financed extensive investigations over the past decade into many aspects of electricity supply, having taken on some of the work of the Edison Electric Institute. On the international front, the International Electrotechnical Commission (IEC) issues a series of standards, which, with time, are becoming harmonized with national standards, although there is a special European process of harmonization, operating through CENELEC, which tends to be faster than the harmonization program of IEC, and many British standards are also harmonized in Europe.

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International energy agencies and services

Jacqui Brookes, in Information Sources in Energy Technology, 1988

INTERNATIONAL UNION OF PRODUCERS AND DISTRIBUTORS OF ELECTRICAL ENERGY (UNIPEDE)

UNIPEDE was founded in 1925 as an international forum promoting the generation and use of electrical energy. Currently, national and governmental bodies of 38 countries are represented. UNIPEDE holds triennial international congresses (the 19th in Brussels, 1982) where authoritative papers on all aspects of power generation, transmission and distribution of electrical energy are presented. A series of standing committees considers and reports on pertinent subjects such as nuclear energy, thermal generation, large systems and international interconnections, medical aspects, research and computers. As well as conference proceedings, UNIPEDE publishes generation and consumption statistics for member nations.

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Introduction to electrical energy systems

Bora Novakovic, Adel Nasiri, in Electric Renewable Energy Systems, 2016

1.1 Electrical energy systems

Electrical energy is one of the most commonly used forms of energy in the world. It can be easily converted into any other energy form and can be safely and efficiently transported over long distances. As a result, it is used in our daily lives more than any other energy source. It powers home appliances, cars, and trains; supplies the machines that pump water; and energizes the light bulbs lighting homes and cities.

Any system that deals with electrical energy on its way between energy sources and loads can be considered to be an electrical energy system. These systems vary greatly in size and complexity. For instance, consider a supply system of a computer, large data center, or power system of a country. All these systems include some sort of power conversion to generate electrical energy, power transmission, and distribution. In all cases, some kind of power transformation is also included either to convert between direct current (DC) and alternating current (AC) systems or to adapt electric supply voltage to the load's requirements.

All electrical energy systems are characterized by the voltage waveform, rated voltage, power levels, and the number of lines or phases in the case of AC systems. Based on the voltage waveform, electrical energy systems can be divided in two main categories, AC systems and DC systems. AC systems transport and distribute energy using alternating voltages and currents while DC systems use direct currents and voltages for the same purpose. Another classification of low voltage (less than 600 V), medium voltage (600 V–69 kV), high voltage (69–230 kV), and extra-high voltage systems (more than 230 kV) can be done based on the voltage ratings of the system [1]. AC systems exist at all voltage levels. DC systems, on the other hand, are more common at extra-high and low voltage levels. AC systems can be further divided to single-phase and polyphase systems depending on the number of phases used for power transmission. Among polyphase systems, the three-phase system is most commonly used.

Another classification of electrical energy systems can be based on their purpose. Assuming that the electrical energy goes through a chain of systems on its path from sources to the loads, it is possible to identify system groups that have common or similar purposes. At the beginning and end of this chain, we generally have some types of energy conversion systems. These devices convert mechanical, thermal, chemical, or some other form of energy into electrical energy or vice versa. They are usually considered to be sources or loads, depending on whether they produce or consume electrical energy. In between we have transmission and distribution systems, which may include a number of electrical energy conversion (transformation) systems. The main purpose of transmission systems is to transport electrical energy in the most efficient manner. Distribution systems distribute electrical energy among loads and make sure that the form of the electrical energy fits the load requirements. Electrical energy conversion (transformation) systems are usually part of transmission and distribution systems. They change the form of electrical energy by modifying either the voltage levels, voltage waveforms, or the number of phases in the case of polyphase systems.

As an example, consider a large utility grid system. In this type of system, the end points are sources and loads. On the source side, we have energy conversion systems in the form of large power plants, converting the energy from fossil, renewable, or nuclear energy sources into electrical energy. These systems are highly complicated and may include several energy conversion stages. However, output is in most cases at the terminals of a medium voltage three-phase generator, which is an electromechanical energy conversion system on its own. In a large power system, generators are usually far from loads. As a consequence, medium voltage three-phase power from the generators first goes to the transmission system, which transports the energy over long distances. Before it is transported, electrical energy is transformed into a form that is suitable for low loss transportation over large distances, usually high voltage AC or DC. From the transmission system, the high voltage electrical energy is transferred to a distribution system where it is converted into low and medium voltage levels and distributed among loads.

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Storing Energy in China—An Overview

Haisheng Chen, ... Shan Hu, in Storing Energy, 2016

1 Introduction

Electrical energy storage (EES) refers to a process of converting electrical energy from a power network into a form that can be stored for converting back to electrical energy when needed [1–3]. Such a process enables electricity to be produced at times of either low demand, low generation cost, or from intermittent energy sources and to be used at times of high demand, high generation cost, or when no other generation is available [1–5]. EES has numerous applications including portable devices (mobile phones, laptops, toys, personal stereos, etc.), transport vehicles (electrical vehicles, yachts, autocycles, trains, etc.), and stationary energy resources [1–9]. This chapter concentrates on EES systems for stationary applications such as power generation, distribution and transition network, distributed energy resource, renewable energy, and industrial and commercial customers.

EES is currently enjoying somewhat of a renaissance, for a variety of reasons including changes in the worldwide utility regulatory environment; ever-increasing reliance on electricity in industry, commerce, and the home; power quality/quality-of-supply issues; the growth of renewables as a major new source of electricity supply; and all of these combined with ever increasing stringent environmental requirements [3,4,6]. These factors, combined with the rapidly accelerating rate of technological development in many emerging EES systems, with anticipated unit cost reductions, now make their practical application look very attractive on future timescales of only a few years. The governments of the United States [1,2,9,13–15], the European Union [3,6,10], Japan [10,16], and Australia [4] all have announced national programs on EES since the late 1990s. The anticipated storage level will boost energy by between (10–15)% in the United States and in European countries, and even higher in Japan in the near future [4,10] (as of 2015).

Although started later than other developed countries mentioned above, China has achieved much progress in research and application of EES. This chapter aims to review the current status of EES in China on both aspects of technology and development. As this book demonstrates, there are over 10 types of EES technologies in usage or under development at the present time. These include pumped hydroelectric storage (PHES) [11,12,17], compressed air energy storage (CAES) [18–22], flywheels [13,16,33,34], lead–acid batteries [23–27], lithium–ion batteries, sodium–sulfur batteries, flow batteries [3,4,6,13], fuel cells [24,28], solar fuel [4,29], superconducting magnetic energy storage (SMES) [30–32], cryogenic energy storage [33–43], and capacitor and supercapacitor storage [4,16]. Currently in China the first seven types of technologies have been in use, as large-scale, megawatt-scale facilities or as demonstration facilities. This chapter will focus on these seven types of EES technologies.

The chapter will include a discussion on the imperativeness and applications of EES technologies; technical characteristics, research, deployment, and the status of development of EES systems; and the prospects for EES technologies in China.

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Economical Aspects in Photocatalytic Membrane Reactors

Wolfgang M. Samhaber, Minh Tan Nguyen, in Current Trends and Future Developments on (Bio-) Membranes, 2018

11.2.1.4 Electrical Energy per Mass

•

Definition: Electrical energy per mass (EE/M) is the electrical energy in kilowatt hours (kWh) required to bring about the degradation of a unit mass (1 kilogram, kg) of a contaminant C in polluted water or air.

•

EE/M can be best used when [C] is high (i.e., phenomenologically zero order in C).

•

EE/M (kWh kg) can be calculated by formula (11.15):

(11.15)EE/M=Pτ1000VM60(Ci−Cf)

For photochemical process of the zeroth-order rate:

Eq. (11.15) can be written in another way as:

(11.16)

EE/M is inversely proportional to the fundament efficiency factors such as G, χ, and ϕZ.

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Energy storage technologies

Fayaz Hussain, ... M. Hasanuzzaman, in Energy for Sustainable Development, 2020

6.3.4.4 Time shifting

When electrical energy is less expensive, time-shifting can be obtained by storing electrical energy. After this, the stored energy can be used or sold during the high demand periods of energy. Storing energy using PHES can also facilitate the shifting of renewable energy from one-time frame of the day to another and from weekdays to weekends (Zabalawi, Mandic, & Nasiri, 2008). In this regard, PHES technology needs to have power between 1 and 100 MW. Other energy storage systems like conventional batteries and solar fuels have also the capability for such application.

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Physiological principles of electrical stimulation

Narendra Bhadra, in Implantable Neuroprostheses for Restoring Function, 2015

Abstract

Electrical energy is applied to living tissue in a number of procedures for diagnosis, therapy, or functional restoration. Biological responses depend on the nature of the tissue and characteristics of the applied stimulus. An ionic internal environment and the presence of semipermeable cellular membranes result in charge separation and intrinsic electrical fields in the body. These fields can be manipulated by electronically generated electrical stimuli. This chapter discusses the physiological basis of excitable body tissues and electrical stimulation in the context of neuroprosthetics. It begins with an overview of target tissues at macro- and microscopic levels and functional aspects of biochemistry and biophysics of excitable tissues. It later covers electrical activation of nerve and muscle tissue and interactive aspects of stimulation electrodes.

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UV-based advanced oxidation process for the treatment of pharmaceuticals and personal care products

Kaiheng Guo, ... Jingyun Fang, in Contaminants of Emerging Concern in Water and Wastewater, 2020

2.3 Energy requirement

The electrical energy per order (EE/O) is applied to calculate the energy requirements of removing PPCPs during the UV/H2O2 process.16,29,48,49 The EE/O consists of the energy input of the UV (EE/OUV) process and the cost of the oxidants (EE/Ooxidant). Compared with UV treatment alone, the addition of H2O2 significantly decreases the energy requirement for the removal of PPCPs that are resistant to UV photolysis, such as naproxen, ibuprofen, bisphenol A, carbamazepine, primidone, atenolol, trimethoprim, gemfibrozil, DEET, and meprobamate.48 For the removal of various types of PPCPs under practical conditions, the EE/O for a 90% PPCP transformation by UV/H2O2 varied in the ranges from 0.17 to 2.38 kW h m−3, respectively, in simulated drinking water, while the EE/O varied in the ranges from 0.22 to 8.09 kW h m−3, respectively, in wastewater.16 The cost of UV irradiation far outweighed the cost of the oxidants in the process,49 taking > 94% of overall cost.16 The energy consumption can be higher for the UV/H2O2 process when considering the reagent cost for the quenching residual H2O2.50

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Power System Energy Storage Technologies

Paul Breeze, in Power Generation Technologies (Third Edition), 2019

Abstract

Electrical energy storage can play an important role in electricity supply by storing off-peak energy for delivery in periods of peak demand and by helping to stabilise the generation from intermittent resources such as wind and solar power. Analysis suggests that for optimum grid stability, 15% of capacity should be based on energy storage. However, the storage of electricity has proved difficult to master. The main large-scale energy storage technologies are pumped-storage hydropower, compressed air energy storage and at the lower capacity range, batteries. For smaller scale storage, supercapacitors and flywheels can be used and small superconducting magnetic energy storage rings have been used in some grid stability applications. Pumped-storage hydropower accounts for most of the capacity already in place and much of this was built to support nuclear generating capacity. There is interest today in energy storage to help the integration of intermittent renewable capacity.

Electrical_system

Electrical systems and equipment include the alarm system, aids to navigation, communication system, area classification, power generation, emergency generator, electrical switchgear/MCC, lighting systems and fire detection.

From: Handbook of Offshore Engineering, 2005

Related terms:

Energy Engineering

Semiconductor

Amplifier

Resistors

Impedance

Capacitance

Oscillators

Transistors

Amplitudes

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Electrical Systems

Nicolae Lobontiu, in System Dynamics for Engineering Students, 2010

Introduction

Electrical systems, also named circuits or networks, are designed as combinations of mainly three fundamental components—resistor, capacitor, and inductor—which are correspondingly defined by resistance, capacitance, and inductance, generally considered to be lumped parameters. In addition to these primary electrical components, in this chapter, we also discuss the operational amplifier. Producing the electron motion or voltage difference in an electrical circuit are the voltage or current sources, which are the counterparts of forces or moments in mechanical systems. The focus in this chapter is the formulation of mathematical models using methods of electrical circuit analysis. Examples will be analyzed using MATLAB® and Simulink® to determine the natural, free, and forced responses of electrical systems.

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Electrical Systems

Nicolae Lobontiu, in System Dynamics for Engineering Students (Second Edition), 2018

Introduction

Electrical systems, also named circuits or networks, are designed as combinations of mainly three fundamental components: resistor, capacitor, and inductor. They are correspondingly defined by resistance, capacitance, and inductance—generally considered to be lumped-parameter properties. In addition to these primary electrical components, we also discuss the op amp in this chapter. The voltage or current sources, which produce the electron motion in an electrical circuit, are the counterparts of forces or moments in mechanical systems. The focus in this chapter is on formulating mathematical models with methods of electrical circuit analysis and on finding and characterizing the natural, free damped, and forced responses of electrical systems by using MATLAB and Simulink. Analogies between electrical and mechanical systems are also studied.

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Measurement techniques for piston-ring tribology

I. Sherrington, in Tribology and Dynamics of Engine and Powertrain, 2010

Limitations

Electrical systems such as thermocouples and thermistors are highly convenient and well-established technologies for temperature measurement. They can be relatively easily incorporated into pistons and are able to measure internal and surface temperatures. However, they normally record average temperature and are not normally able to respond to the rapid and potentially wide-ranging changes in temperature which occur at the surface of the piston along its stroke and as a consequence of combustion gas flow effects.

Optical systems are largely valuable for measuring the surface temperature of engine components. The exception to this is the use of thermographic phosphor doped optical fibres which can also be inserted into components for localised measurements. Optical methods also offer the possibility to respond to rapid transient changes in surface temperature which is potentially of considerable value in lubrication problems.

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Electrical Power Systems

John P.T. Mo, ... Raj Das, in Demystifying Numerical Models, 2019

Abstract

An electrical system consists of many different forms of components such as motors, resistors, capacitors, and transistors. These components are designed to be connected in an electrical circuit. The primary objective is to drive the electrical circuit with two electrical characteristics, i.e., voltage and current, which can be measured for understanding and control of the electrical systems, so that desirable system outcomes can be achieved. This chapter uses motor circuits to illustrate how numerical integration methods such as Runge–Kutta can be used to find the responses of the motor system. The numerical responses are compared with the analytical responses and the errors are computed.

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Impact of Energy and Atmosphere

Sam Kubba Ph.D., LEED AP, in LEED v4 Practices, Certification, and Accreditation Handbook (Second Edition), 2016

9.4.1 General

Electrical systems that provide a facility with accessible energy for heating, cooling, lighting and equipment (telecommunication devices, personal computers, networks, copiers, printers, etc.) and appliance operation (e.g., refrigerators and dishwashers) has witnessed dramatic developments in the past few decades, comprising the fastest-growing energy load within a building. More than ever, facilities today need electrical systems to provide power with which most of the vital building systems operate. These systems control the energy required in the building and distributes it to the location utilizing it. Most frequently, distribution line voltage carried at utility poles is delivered at 2400/4160 V. Transformers step down this voltage to predefined levels for use within buildings. In an electric power distribution grid, the most common form of electric service is through the use of overhead wires known as a service drop, which is an electrical line running from a utility pole to a customer's building or other premises. It is the point where electric utilities provide power to their customers.

In residential installations in North America and countries that use their system, a service drop comprises of two 120-V lines and a neutral line. When these lines are insulated and twisted together, they are referred to as a triplex cable. In order for these lines to enter a customer's premises, they must usually first pass through an electric meter and then the main service panel, which will usually contain a "main" fuse or circuit breaker. This circuit breaker controls all of the electrical current entering the building at once, and a number of smaller fuses/breakers, which protect individual branch circuits. There is always a main shutoff switch to turn off all power; when circuit breakers are used, this is provided by the main circuit breaker. The neutral line from the pole is connected to an earth ground near the service panel – often a conductive rod driven into the earth.

In residential applications, the service drop provides the building with two separate 120-V lines of opposite phase, so 240 V can be obtained by connecting a circuit between the two 120-V conductors, whereas 120-V circuits are connected between either of the two 120-V lines and the neutral line. In addition, 240-V circuits are used for high-power devices and major appliances, such as air conditioners, clothes dryers, ovens, and boilers, whereas 120-V circuits are used for lighting and ordinary small appliances. It should be noted that these are "nominal" numbers, meaning that the actual voltage may vary.

In Europe and many other countries, a three-phase 416Y/230 system is used. The service drop consists of three 240-V wires, or phases, and a neutral wire, which is grounded. Each phase wire provides 240 V to loads connected between it and the neutral. Each of the phase wires carries 50-Hz alternating current, which is 120° out of phase with the other two. The higher voltages, combined with the economical three-phase transmission scheme, allow a service drop to be longer than in the North American system, and allow a single drop to service several customers.

For commercial and industrial service drops, which are usually much larger and more complex, a three-phase system is used. In the United States, common services consist of 120Y/208 (three 120-V circuits 120° out of phase, with 208 V line to line), 240-V three-phase, and 480-V three-phase. In Canada, 575-V three-phase is common, and 380–415 V or 690-V three-phase is found in many other countries. Generally, higher voltages are used for heavy industrial loads, and lower voltages for commercial applications.

The difference between commercial and residential electrical installations can be quite significant, particularly with large installations. Although the electrical needs of a commercial building can be simple, consisting of a few lights for some small structures, they are often quite complex, with transformers and heavy industrial equipment. When electrical or lighting system deficiencies become evident and need attention, they are usually measurable and include power surges, tripped circuit breakers, noisy ballasts, and other more obvious conditions such as inoperative electrical receptacles or lighting fixtures that are frequently discovered or observed during a review of the system. As illustrated in Figures 9.16 and 9.17, there are a number of typical deficiencies found in both the electrical and the lighting systems.

Figure 9.16. Diagram Showing Typical Deficiencies Found in Electrical Systems.

Figure 9.17. Diagram Showing Typical Deficiencies Found in Lighting Systems.

In many commercial buildings, the major load placed on a given electrical system comes from the lighting requirements; therefore, the distribution and management of electrical and lighting loads must always be monitored on a regular basis. Lighting management should also be periodically checked because building space uses change and users relocate within the building. It is also highly advisable for the lighting system to be integrated with the electrical system in the facility. Lighting systems are designed to ensure adequate visibility for both the interior and exterior of a facility and are composed of an energy source, and distribution elements normally consisting of wiring and light-emitting equipment.

There are several different electrical codes today being enforced in various jurisdictions throughout the United States. Some of the larger cities, such as New York and Los Angeles, have created and adopted their own electrical codes. The National Electrical Code (NEC) and the National Fire Protection Code (NFPC), published by the National Fire Protection Association (NFPA), cover almost all electrical system components. The NEC is commonly adopted in whole or in part by municipalities. Inspection of the electrical and lighting system should include a determination of general compliance with these codes at the facility.

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Power Electronic Systems for Aircraft

Tao Yang, ... Patrick Wheeler, in Control of Power Electronic Converters and Systems, 2018

24.2.2 Conventional Aircraft Electrical Power Systems

Electrical systems have made significant advances over the years with the development of power electronics and electrical drive systems. The use of electrical power structure in a conventional aircraft has been illustrated by an electrical power system structure shown in Fig. 24.2. Each generator delivers 115 VAC/400 Hz electrical power to the main AC bus and controlled by its own Generator Control Unit (GCU). The 115 VAC power is transformed to 28 VDC power using transformer rectifier units (TRUs). TRUs consist of a multiphase transformer and an n-pulse diode rectifier, where n = 12 or 18, to reduce the ripple on the DC-link and to achieve the power quality requirements. The electrical loads supplied by the 28 VDC bus are the avionics, cabin electronics and the back-up batteries. Other AC electrical loads, such as lighting, galley loads, entertainment system and auxiliary hydraulic pumps are directly fed by the AC bus.

Fig. 24.2. Conventional aircraft electrical system architecture.

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Mixed Signal Modeling

Peter Wilson, in Design Recipes for FPGAs (Second Edition), 2016

18.5 Mixed Domain Modeling

In order to use standard models, there has to be a framework for terminals and variables, which is where the standard packages are used. There is a complete IEEE Std (1076.1.1) that defines the standard packages in their entirety; however, it is useful to look at a simplified package (electrical systems in this case) to see how the package is put together.

For example electrical systems models need to be able to handle several key aspects:

•

electrical connection points;

•

electrical through variables, that is, current;

•

electrical across variables, that is, voltages.

The electrical systems package needs to encompass these elements.

First the basic subtypes need to be defined. In all the analog systems and types, the basic underlying VHDL type is always real and so the voltage and current must be defined as subtypes of real.

1 subtype voltage is real ;

2 subtype current is real ;

Notice that there is no automatic unit assignment for either, but this is handled separately by the unit and symbol attributes in IEEE Std 1076.1.1. For example, for voltage the unit is defined as Volt and the symbol is defined as V.

The remainder of the basic electrical type definition then links these subtypes to the through and across variable of the type, respectively:

1 package electrical_system is

2 subtype voltage is real ;

3 subtype current is real ;

4 nature electrical is

5 voltage across

6 current through

7 ground reference ;

8 end package electrical_system ;

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Management of Batteries for Electric Traction Vehicles

Daniel D. Friel, in Electric and Hybrid Vehicles, 2010

3.3.2 Connection sequence

Most electrical systems are connected to a power source by first connecting the most negative or ground connection, then the most positive. In the case of a BMS, the power source is the battery and the connection sequence cannot always be guaranteed.

Smaller battery systems such as LEV, industrial or microhybrid (start–stop) vehicles may allow the most negative electrochemical cell to be connected first, then the next most negative, on up to the most positive cell.

But in larger battery arrays such as those in EVs, mild and full hybrids, and PHEVs, the connection of the electrochemical cells to the BMS is often random. Thus it is possible for high voltages to exist for many seconds, while the connection sequence is occurring. The BMS electronics must therefore be protected against these large voltages during this crucial time.

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Development of sustainable nuclear power plant project

Nikolay Belyakov, in Sustainable Power Generation, 2019

13.1.1.2 Electrical system analysis

A national or even regional cross-boundary electrical system analysis is usually performed to understand the capacity and needs of the demand of the electricity market, as well as the capacity of the grid to accommodate these additional capacities.

An electrical system analysis assumes a number of activities and includes:

•

Current electricity demand and its forecast for the whole lifecycle of a nuclear power plant;

•

Supply characteristic of the generated electricity;

•

Electricity market structure and its organization with the potential influence with new plant;

•

Base scenario of the overall electricity system development;

•

Nuclear power plant project impact on the grid and the possibility to transfer full capacity with the current grid assets.

This study can be carried out together with other planning activities of new capacity introduction compared with the regional electricity demand. This analysis is normally based on historical data, and can include:

•

Thorough study of the electricity consumption scheme;

•

Load demand, e.g., base, semi-peak, and especially peak;

•

Duration of each demand and its nature (seasonal, weekly or daily);

•

Efficiency study of the transmission and distribution system, understanding current and possible future losses and capacity bottlenecks;

•

Historical supply of electricity, including fuel and electricity pricing, as well as various flows of energy imports and exports.

Finally, electricity demand projections for the nuclear power plant project lifecycle time are proposed. There are multiple approaches, including statistics-based extrapolation or consumer analysis, however, the result shall give a clear understanding of the market energy demand. This understanding is crucial to define the scope of the future power plant, namely electrical capacity and the capability of the generator to respond to the grid requirements.

The analysis should be conducted with relevant and consistent macroeconomic and microeconomic data, so that electricity demand projections can be reliable and consistent with demographic, economic, and industrial development projections [3].

Remark 13.1

While the same type of analysis is conducted for any type of a power plant, it is by far more important for nuclear projects. This is due to much higher investment costs and rather low flexibility of the plant to match market demand, if needed. While thermal plants require less money to build, and big hydro facilities can operate with certain flexibility (to allow for better market fit within semi- and peaking mode), nuclear energy is subject to much higher risks.

The result of the analysis shall clearly highlight the advantages of an addition of nuclear capacities within the market, for example, to cover growing base load electricity demand, growing emissions charges to be mitigated with low carbon technology, energy independence of the region from foreign power imports, etc.

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Piezoelectric and fibre-optic hydrophones

A. Hurrell, P. Beard, in Ultrasonic Transducers, 2012

Minimum (noise equivalent) acoustic signal

All electrical systems have some level of inherent noise. The noise figure for any given hydrophone system could be expressed in terms of an electrical noise measurement. However, a hydrophone system is providing an acousto-electrical transduction and thus the minimum acoustic signal that can be measured is of more relevance. This can be conveniently achieved by considering the noise equivalent pressure (NEP), which is the acoustic pressure that provides an SNR of unity. This quantity is insensitive to the details of the transduction method (i.e. piezoelectric or fibre-optic) and has the added advantage of implicitly incorporating any gain/attenuation included within the system.

NEP is inherently related to sensitivity of a hydrophone, as well as the noise floor of the data acquisition (DAQ) system used to record the hydrophone's output signal. Consider an idealised hydrophone with a uniform sensitivity of 100 mV/MPa at all frequencies. Furthermore, let the bandwidth of the measurement system be 100 MHz and let the noise level of the hydrophone system be 50 μV rms over this bandwidth. The system thus has an NEP of

50μV100mV/MPa=0.5×10−3MPa=500Parms.

Two slight complications arise from this initial, simplistic example. Firstly, the majority of DAQ systems currently in use are unable to quantify signals much smaller than 0.5 mV. Consequently the practical NEP of a hydrophone system connected to such a DAQ device would be at least an order of magnitude worse due to the inherent noise floor. As such, it is important for a hydrophone user to consider the difference between theoretically and practically achievable NEP, given the limitations of the DAQ they may be using.

Secondly, the example above assumed hydrophone sensitivity was independent of frequency. As will be discussed in some detail within Section 19.2.2 and elsewhere within this chapter, hydrophones have a frequency-dependent sensitivity. Ideally a spectral method of noise assessment capable of incorporating this frequency dependence should be used when assessing NEP. However, for many practical applications this added complexity is avoided by assuming a nominal hydrophone sensitivity across the bandwidth of interest.

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Recommended publications:

Renewable and Sustainable Energy Reviews

Journal

Renewable Energy

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Energy

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Electric Power Systems

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Electrical Energy

Related terms:

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Interconnections

D.I. Crecraft, S. Gergely, in Analog Electronics: Circuits, Systems and Signal Processing, 2002

12.1 Introduction

Electrical energy is transferred between components, sub-systems and systems either by conduction along an electrical conductor, a wire, a track on a printed circuit board or a wave guide, or by radiation in free space as in radio or TV broadcasting. In the case of electrical signals (as defined in Section 2.1), it is the change of the pattern of energy that is of interest. Similarly, light energy is transferred either by a light guide (optical fibre) or in air. Interconnections are often taken for granted as 'just a bit of wire' but it is obvious that the performance of any system is degraded, sometimes to the point of total failure, if the process of energy, and therefore signal, transfer is inefficient or inadequate.

It is important and interesting to note that a great many of the failures of electrical and electronic equipment are caused by the failure of interconnections. This is why shaking or hitting malfunctioning equipment is so frequently effective and therefore tempting. The resulting vibration may re-establish the electrical contact. Similarly, the failure of i.cs can often be traced to the failure of the internal connections.

It is often said that components etc. are connected by a piece of wire. But in fact two pieces of such wire are required since electrical current flows in a closed circuit. Very often the system earth (ground) connection is used as the second of the two pieces of wire. This path is usually shared by a number of circuits. The problems created by the sharing of the 'return' path are considered later in Section 12.3.2.

The electrical properties of the interconnections are determined using their equivalent circuit. This was first established in connection with the long distance transmission of electrical power and telegraph messages. Therefore, the term transmission lines is used in a wide range of applications. It will be shown that short lines at high frequencies behave very similarly to long ones at low frequencies.

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Vehicle Sensors and Lighting

Robert D. Christ, Robert L. WernliSr., in The ROV Manual (Second Edition), 2014

11.2.2 Practical applications

This explanation of lighting comes from Ronan Gray, an expert on the subject. The need for underwater lighting becomes apparent below a few feet from the surface. Ambient visible light is quickly attenuated by a combination of scattering and absorption, thus requiring artificial lighting to view items underwater with any degree of clarity. We see things in color because objects reflect wavelengths of light that represent the colors of the visible spectrum. Artificial lighting is therefore necessary near the illuminated object to view it in true color with intensity. Underwater lamps provide this capability.

Lamps convert electrical energy into light. The main types or classes of artificial lamps/light sources used in underwater lighting are incandescent, fluorescent, high-intensity gas discharge, and light-emitting diode (LED)—each with its strengths and weaknesses. All types of light are meant to augment the natural light present in the environment. Table 11.2 shows the major types of artificial lighting systems, as well as their respective characteristics.

Table 11.2. Light Source Characteristics

SourceLumens/WattLife (hours)ColorSizeBallastIncandescent15−2550−2500ReddishM–LNoTungsten-halogen18−3325−4000ReddishS–MNoFluorescent40−9010,000VariesLYesGreen fluorescent12510,000GreenLYesMercury20−5820,000BluishMYesMetal halide70−12510,000VariesMYesHigh-pressure sodium65−14024,000PinkMYes/IXenon arc20−40400−2000DaylightVYes/IHMI/CID70−100200−2000DaylightSYes/ILow-pressure sodium100−18518,000YellowLYesXenon flash30−60NADaylightMNA

V, very small; S, small; M, medium; L, large; I, ignitor required; NA, not applicable.

Source: Courtesy of Deep Sea Power & Light.

•

Incandescent: The incandescent lamp was the first artificial lightbulb invented. Electricity is passed through a thin metal element, heating it to a high enough temperature to glow (thus producing light). It is inefficient as a lighting source with approximately 90% of the energy wasted as heat. Halogen bulbs are an improved incandescent. Light energy output is about 15% of energy input, instead of 10%, allowing them to produce about 50% more light from the same amount of electrical power. However, the halogen bulb capsule is under high pressure instead of a vacuum or low-pressure noble gas (as with regular incandescent lamps) and, although much smaller, its hotter filament temperature causes the bulbs to have a very hot surface. This means that such glass bulbs can explode if broken or if operated with residue (such as fingerprints) on them. The risk of burns or fire is also greater than with other bulbs, leading to their prohibition in some underwater applications. Halogen capsules can be put inside regular bulbs or dichroic reflectors, either for aesthetics or for safety. Good halogen bulbs produce a sunshine-like white light, while regular incandescent bulbs produce a light between sunlight and candlelight.

•

Fluorescent: A fluorescent lamp is a type of lamp that uses electricity to excite mercury vapor in argon or neon gas, producing short-wave ultraviolet light. This light then causes a phosphor coating on the light tube to fluoresce, producing visible light. Fluorescent bulbs are about 40% efficient, meaning that for the same amount of light they use one-fourth the power and produce one-sixth the heat of a regular incandescent. Fluorescents typically do not have the luminescent output capacity per unit volume of other types of lighting, making them (in many underwater applications) a poor choice for underwater artificial light sources.

•

High-intensity discharge: High-intensity discharge (HID) lamps include the following types of electrical lights: mercury vapor, metal halide, high-pressure sodium, and, less common, xenon short-arc lamps. The light-producing element of these lamp types is a well-stabilized arc discharge contained within a refractory envelope (arc tube) with wall loading (power intensity per unit area of the arc tube) in excess of 3 W/cm2 (19.4 W/in2). Compared to fluorescent and incandescent lamps, HID lamps produce a large quantity of light in a small package, making them well suited for mounting on underwater vehicles. The most common HID lights used in underwater work are of the metal halide type.

•

LED: An LED is a semiconductor device that emits incoherent narrow-spectrum light when electrically biased in the forward direction. This effect is a form of electroluminescence. The color of the emitted light depends on the chemical composition of the semiconducting material used and can be near-ultraviolet, visible, or infrared. LED technology is useful for underwater lighting because of its low power consumption, low heat generation, instantaneous on/off control, continuity of color throughout the life of the diode, extremely long life, and relatively low cost of manufacture. LED lighting is a rapidly evolving technology and is being widely adapted by ROV manufacturers and users.

Observation-class ROV systems use the smaller lighting systems, including halogen and metal halide HID lighting (although LED systems are now standard equipment for most OEM OCROVs). In the MSROV and WCROV world, LED lights have now become standard equipment.

The efficiency metric for lamps is efficacy, which is defined as light output in lumens divided by energy input in watts, with units of lumens per watt (LPW). Lamp efficacy refers to the lamp's rated light output per nominal lamp watts. System efficacy refers to the lamp's rated light output per system watts, which include the ballast losses (if applicable). Efficacy may be expressed as "initial efficacy," using rated initial lumens at the beginning of lamp life. Alternatively, efficacy may be expressed as "mean efficacy," using rated mean lumens over the lamp's lifetime; mean lumens are usually given at 40% of the lamp's rated life and indicate the degree of lumen depreciation as the lamp ages.

An efficient reflector will not only maximize the light output that falls on the target but will also direct heat forward and away from the lamp. The shape of the reflector will be the main determinant in how the light output is directed. Most are parabolic, but ellipsoidal reflectors are often used in underwater applications to focus light through a small opening in a pressure housing. The surface condition of a reflector will determine how the light output will be dispersed and diffused. The majority of reflectors are made of pure, highly polished aluminum that will reflect light back at roughly the same angle to the normal at which it was incident. By adding dimples or peens to the surface, the reflected light is dispersed or spread out. When a plain white surface is used, the reflected light is diffused in all directions.

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13th International Symposium on Process Systems Engineering (PSE 2018)

Lucas Lyrio de Oliveira, ... Erik Eduardo Rego, in Computer Aided Chemical Engineering, 2018

1 Introduction

The global electrical energy demand may increase by a factor of seven over the next five decades (Siirola, 2012). As a developing country, Brazil presents a high potential for electricity consumption growth. Forecasts from the Empresa de Pesquisa Energética (EPE) – shows that in 2026 the country's demand for electricity will be 43.6% higher than in 2016 (EPE, 2017). The Brazilian electricity mix is predominantly renewable but due to recent droughts there has been an expressive increase in the demand for fossil fuels for thermopower generation. Thus, an important question is: how to expand the Brazilian electricity capacity to attend the demand growth considering renewable sources.

The Brazilian grid is made up of four interconnected electricity subsystems with more than 99% of the electricity generated in the country being delivered through the national interconnected system (Operador Nacional do Sistema (ONS), 2017). Hydropower is the main generation source, corresponding to 61.40% of the total installed capacity (Agência Nacional de Energia Elétrica (Aneel), 2017). Other important renewable sources are biomass and wind, representing 8.77% and 6.71% of the country's installed capacity. Fossil fuels account for 16.76%, nuclear 1.24% and importation from Paraguay, Argentina, Venezuela and Uruguay 5.04% (Aneel, 2017). Natural gas plays an important role to guarantee the system reliability. Brazil uses fossil fuel power plants to overcome the variability on the hydro, wind and biomass supply, with natural gas representing more than 48% of the fossil installed capacity (Aneel, 2017).

As the hydro potential in many regions is already saturated and most of the country's remaining potential is situated far from the centres with the highest demand, high investments on transmission lines would be required to attend the demand growth. Moreover, the operation of hydropower plants depends on the hydrological conditions, exposing the system to the risk of electricity shortfalls during drought periods. Consequently, the expansion of other sources to meet the growing demand is needed and the choice of such sources is a challenge.

One approach to determine the amount of expansion for each energy source is through Modern Portfolio Theory (Markowitz, 1952). Originally designed to find portfolios of financial assets with minimum risk, this approach has been adapted to many applications, including electricity portfolios (Awerbuch and Berger, 2003).

Expressive regional differences with respect to natural resources availability, level of industrialization, socioeconomic conditions and climate influence the operation of the whole Brazilian system. Therefore, it is possible that transmission constraints and limits on the amount of generation in different regions of the country may affect the overall participation of each generation source. Such issues are considered in the present study through the development of optimization models. The objective is to find electricity matrices with minimum cost risk, to meet the demand forecasted by EPE for the year 2026 (EPE, 2017).

The models consider two risk measures: the variance of costs, as in the original work of Markowitz (1952), and the β-CVaR, a tail risk measure proposed by Rockafellar and Uryasev (2000) defined as the expected cost, above a fixed β-percentile. The decision variables - xijk - are the amount of electricity generated through source k, in the supply subsystem i, to be sent to the consumption subsystem j.

Recent discoveries of natural gas reserves in the Brazilian pre-salt, the effort to maintain high shares of renewable sources and improvements on bioelectricity generation technologies suggest four different scenarios to be analysed regarding the costs of electricity generation: Scenario 1 considers industry experts costs estimation, Scenario 2 and 3 assume respectively that natural gas and biomass generation costs maintains 20% lower than in Scenario 1, and Scenario 4 considers that both natural gas and biomass generation costs maintain 20% lower than in Scenario 1.

Section 2 presents an overview of the Brazilian power sector. The portfolio models are described in section 3 and the results are presented in section 4. Section 5 concludes this study.

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Power and Telemetry

Robert D. Christ, Robert L. WernliSr., in The ROV Manual (Second Edition), 2014

7.1.7.2 Electrohydraulic power

While the OCROV has electrical energy exclusively driving moving components, both the MSROV and WCROV typically involve some form of fluid component drive (i.e., hydraulics) for a portion or all of its moving components. On all hydraulic components, the electric circuit drives an electric motor which in turns drives a hydraulic pump at the design specifications of the pump manufacturer. On MSROVs, this typically means that the vehicle manufacturer modifies (or directly uses) a thruster motor to turn the low-volume pump, while the WCROV manufacturer will specially design an HV motor (or design the hydraulic system around a COTS HV motor) to achieve the system's design objective involving a large number of hydraulic components.

As an example, the Schilling design philosophy for driving its WCROV power system involves a single high-capacity electrical motor with double-ended splines to drive the vehicle's two easily replaceable pumps—one high-capacity pump for the main hydraulic system (for thrusters, manipulators, valve packs, and (optionally) P&T unit) and the other for the auxiliary/tooling system (Figure 7.14). The purpose of the dual hydraulic systems is to maintain the cleanliness of the main hydraulics as tooling is typically interchangeable and will often induce contaminated oil into an otherwise sanitary hydraulic system. Clogged valves for manipulators or thrusters will produce unexpected movements, possibly compromising safety.

Figure 7.14. Schilling design for single motor driving a two-pump system for separate circuits.

(Courtesy Schilling Robotics.)

Other manufacturers use variations on this combination with single hydraulic circuits but introducing multiple layers of filtering to reduce the possibility of oil contamination from tooling components.

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26th European Symposium on Computer Aided Process Engineering

Fridolin Röder, ... Ulrike Krewer, in Computer Aided Chemical Engineering, 2016

1 Introduction

Lithium-ion batteries supply electrical energy via an electrochemical redox reaction at anode and cathode. The anodes are used at electrical potentials outside the electrochemical stability window of the electrolyte. Continuous decomposition of the electrolyte is prevented by a thin layer at the active particle surface. This layer consists of various by products of electrolyte decomposition reactions and acts as an Solid Electrolyte Interface (SEI). The interphase needs to be a good lithium-ion conductor, but insulating for electrons in order to provide good performance and long lifetime of the battery.

Research has been carried out on modeling layer growth and its impact on the battery performance using macroscopic models (Colclasure et al., 2011; Ploehn et al., 2004), while atomistic models based on Molecular Dynamic and Transition State Theory studies have been used to determine the most important reaction mechanisms (Ganesh et al., 2012; Leung and Budzien, 2010; Wang et al., 2001; Leung, 2013; Agubra and Fergus, 2014). According to Arorat et al. (1998), atomistic models are limited in time and length scales, and thus cannot be used to understand the SEI formation and predict its composition. In order to bridge this cap, this article introduces a multi-scale modeling approach using kinetic Monte Carlo (kMC) method in combination with a macroscopic model, which provides new insights in the layer formation mechanism during a long time-scale discharge process.

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23rd European Symposium on Computer Aided Process Engineering

Georgios M. Kopanos, Efstratios N. Pistikopoulos, in Computer Aided Chemical Engineering, 2013

5.1 Basic Concept

Consider as uncertain parameters θ the electrical energy and heat demand as well as the initial state of the system (i.e., εi0 and βi0).

Define the prediction horizon (i.e., time horizon wherein θ parameters could be considered as certain) and the control horizon (i.e., time horizon wherein the output of the optimization is applied); depending on the complexity of the problem and/or the nature of the uncertain parameters.

Solve off-line and once the resulting mp-LP problem, and obtain the critical regions (and their corresponding functions) for the whole range of the uncertain parameters.

The output of the (off-line) parametric optimization is used in a receding horizon fashion for the reactive scheduling of the microCHP fuel cell systems; once the actual uncertain parameters (e.g., energy demands) are known with certainty. Note that the initial state of the system in a given prediction horizon n is equal to the final state of the system in the previous control horizon n-1. See Figure 1.

Figure 1. Concept for reactive scheduling via multiparametric programming.

By following the proposed concept, the on-line optimization problem is transformed into a closed-loop control problem. Importantly, the proposed approach could be embedded into a model predictive control scheme involving energy demand forecasting techniques for improving the performance of the method. The salient feature of the proposed methodology is that the optimization is performed just once (i.e., assuming that the range of the uncertain parameters as well as the remaining known parameters will not vary) and off-line (i.e., long ago before the beginning of the actual scheduling horizon). We strongly believe that such an approach will be of highly practical interest, and constitute a proper means to cope with the scheduling problem under consideration wherein energy demands frequently fluctuate.

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Security Lighting

Joseph Nelson CPP, ... James F. Broder CPP, in Effective Physical Security (Fifth Edition), 2017

Twenty-Five Things You Need to Know About Lighting [7]

Watts: Measures the amount of electrical energy used.

Foot-candle: Measure of light on a surface 1 square foot in area on which one unit of light (lumen) is distributed uniformly.

Lumen: Unit of light output from a lamp.

Lamp: Term that refers to light sources that are called bulbs.

Lux: Measurement of illumination.

Illuminare: Intensity of light that falls on an object.

Brightness: Intensity of the sensation from light as seen by the eye.

Foot-lambert: Measure of brightness.

Glare: Excessive brightness.

10.

Luminaire: Complete lighting unit; consists of one or more lamps joined with other parts that distribute light, protect the lamp, position or direct it, and connect it to a power source.

11.

Ballast: Device used with fluorescent and high-intensity discharge (HID) lamps to obtain voltage and current to operate the lamps.

12.

HID: Term used to identify four types of lamps—mercury vapor, metal halide, and high- and low-pressure sodium.

13.

Coefficient of utilization: Ratio of the light delivered from a luminaire to a surface compared to the total light output from a lamp.

14.

Contrast: Relationship between the brightness of an object and its immediate background.

15.

Diffuser: Device on the bottom or sides of a luminaire to redirect or spread light from a source.

16.

Fixture: A luminaire.

17.

Lens: Glass or plastic shield that covers the bottom of a luminaire to control the direction and brightness of the light as it comes out of the fixture or luminaire.

18.

Louvers: Series of baffles arranged in a geometric pattern. They shield a lamp from direct view to avoid glare.

19.

Uniform lighting: Refers to a system of lighting that directs the light specifically on the work or job rather than on the surrounding areas.

20.

Reflector: Device used to redirect light from a lamp.

21.

Task or work lighting: Amount of light that falls on an object of work.

22.

Veiling reflection: Reflection of light from an object that obscures the detail to be observed by reducing the contrast between the object and its background.

23.

Incandescent lamps: Produce light by passing an electric current through a tungsten filament in a glass bulb. They are the least efficient type of bulb.

24.

Fluorescent lamps: Second most common source of light. They draw an electric arc along the length of a tube. The ultraviolet light produced by the arc activates a phosphor coating on the walls of the tube, which causes light.

25.

HID lamps: Consist of mercury vapor, metal halide, and high- and low-pressure sodium lamps. The low-pressure sodium is the most efficient but has a very low CRI of 5.

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22nd European Symposium on Computer Aided Process Engineering

Qiong Cai, ... Nigel P. Brandon, in Computer Aided Chemical Engineering, 2012

3.2 Minimizing electrical energy consumption

The second scenario considered is the minimisation of the electrical energy consumption for a change of average current density between 7000 A/m2 and 1000 A/m2 over a 3000 s time horizon. The optimal profiles for the energy consumption, current density, air ratio and temperature using piecewise linear control are shown in Figs. 7–10. As opposed to maximising hydrogen production, it is favourable to operate at the lowest current density for the longest time period possible, as this consumes the minimal electrical energy. As shown in Fig. 8, the optimal control strategy decreases the current density from 7000 to 1000 A/m2 at the beginning of the optimisation and stays constant until the end of control process at 3000s. The cumulative minimum electrical energy consumed within 3000s is 2735 W, as shown in Fig. 7. The air ratio in Fig. 9 shows an instant increase to the highest value of 14; which is in accordance with the decrease in current density. In the optimal control trajectory for temperature gradient as shown in Fig. 10, the temperature gradient goes through a hill shape and stabilized at around 47.97 K after 1500 seconds; the change in the temperature gradient value is small.

Fig. 7. The optimal control trajectory for cumulative electrical energy consumption.

Fig. 8. The optimal control trajectory for current density.

Fig. 9. The optimal control trajectory for air ratio

Fig. 10. The optimal control trajectory for temperature gradient across the cell.

In both scenarios, one would expect that an air ratio of 5.26 should be enough to satisfy the temperature constraint when current density is changed to 1000 A/m2, from the steady-state performance shown in Fig. 2. However, the increases in air ratio seen in this work are bigger than expected. In practice, there is a penalty to the system efficiency when increasing the air flow rate. Further investigations will be done to examine how the optimal control will respond when such a penalty is applied to the model.

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Antennas, Diversity, and Link Analysis

Vijay K. Garg, in Wireless Communications & Networking, 2007

10.3 Antenna Gain

The task of a transmitting antenna is to convert the electrical energy travelling along a transmission path into electromagnetic waves in space. The antennas are passive devices, the power radiated by the transmitting antenna cannot be greater than the power entering from the transmitter. It is always less because of losses. Antenna gain in one direction results from a concentration of power in that direction and is accompanied by a loss in other directions. Antenna gain [7] is the most important parameter in the design of an antenna system. A high gain is achieved by increasing the aperture area, A, of the antenna. Antennas obey reciprocity; the transmit gain and receive gain are the same, and the antenna can be analyzed by examining it as either a receive or transmit antenna. The amount of power captured by an antenna is given as:

(10.1)P=pA

where:

p = power density (power per unit area)

A = aperture area

Antenna gain can be defined either with respect to an isotropic antenna or with respect to a half-wave dipole and is usually analyzed as a transmit antenna. An isotropic antenna is an idealized system that radiates equally in all directions. The half-wave dipole antenna is a simple, practical antenna which is in common use.

The gain of an antenna in a given direction is the ratio of power density produced by it in that direction divided by the power density that would be produced by an isotropic antenna. The term dBi is used to refer to the antenna gain with respect to the isotropic antenna. The term dBd is used to refer to the antenna gain with respect to a half-wave dipole (0 dBd = 2.1 dBi). While most analyses of system performance use a half-wave dipole as the reference, many times antenna gain figures are quoted in dBi to give a falsely inflated gain figure. The system designer must carefully read data sheets on antennas to use the correct gain figure. As a rule of thumb, if the gain is not quoted in either dBd or dBi, the gain is in dBi, with the dBi left out to inflate the gain figures.

For an isotropic antenna in free space, the received power density is given as

(10.2a)pR=PT4πd2

where:

PT = transmitter power

pR = receiver power density

d = distance between transmitter and receiver

When a directional transmitting antenna with power gain factor, GT, is used, the power density at the receiver antenna is GT times Equation 10.2a, i.e.,

(10.2b)pR=GTPT4πd2

The amount of power captured by the receiver is pR times the aperture area, AR, of the receiving antenna. The aperture area is related to the gain of the receiving antenna by

(10.3)GR=4πARλ2

where:

λ=cf

f = the transmission frequency in Hz

c = 3 × 108 m/s is the free-space speed of propagation for electromagnetic waves

AR = the effective area of aperture, which is less than the physical area by an efficiency factor ρR; typical value for ρR ranges from 60 to 80%

The total received power, PR is given as:

(10.4)PR=ARpR

Substituting the value of PR and AR from Equations 10.2b and 10.3 into Equation 10.4, together with the transmitting antenna gain GT, we get

(10.5)PR=[λ4πd]2PTGTGR

Equation 10.5 includes the power loss only from the spreading of the transmitted wave. If other losses are also present, such as atmospheric absorption or ohm losses of the waveguides leading to antennas, Equation 10.5 can be modified as [4]:

(10.6)PRPT=[λ4πd]2⋅GTGRL0

(10.7)PRPT=GTGRL0Lp

where:

Lp=[4πdλ]2 denotes the loss associated with propagation of electromagnetic waves from the transmitter to the receiver as discussed in Chapter 3.

Lp depends on carrier frequency and separation distance d. This loss is always present. L0 is the loss factor for additional losses.

When we express Equation 10.7 in terms of decibels, we get

(10.8)PR=20log[λ4πd]+PT+GT+GR−L0 dB

The product PTGT is called the effective isotropic radiated power (EIRP) and term 20log[λ4πd] refers to free space path loss (Lp) in dB. Another term, effective radiated power (ERP), is also used. It is the power input multiplied by the antenna gain measured with respect to a half-wave dipole antenna. The EIRP is related to ERP as

(10.9)EIRP=ERP+2.14 dB

In the free space, the path between two antennas has no obstruction (see Figure 10.1) and there is no object where reflection can occur. Thus, the received signal is composed of only one component. When the two antennas are located on the earth, then there are multiple paths from the transmitter to the receiver. The effect of multiple paths is to change the path loss between two points. The simplest case occurs when the antenna heights hT and hR are small compared to their separation distance d and the reflecting earth surface is assumed to be flat (see Chapter 3). The received signal can then be represented by a field that is approximated by a combination of a direct wave and a reflected wave as shown in Figure 10.2. In this case the received power, PR, and transmitted power, PT, are related as (see Chapter 3 and Appendix B for derivation):

Figure 10.1. Free-space path-loss model.

Figure 10.2. Path-loss model with reflection.

(10.10)PRPT=[hThRd2]2⋅GTGRL0

Expressing Equation 10.9 in decibels, we get

(10.11)PR=20log[hThRd2]+PT+GT+GR−L0 dB

comparing it with Equation 10.8 we note that Equation 10.10 is independent of transmitting frequency.

This chapter discusses about electricity. An alternating current is induced in a conductor rotating in a magnetic field. The value of the current and its direction of flow in the conductor depends upon the relative position of the conductor to the magnetic flux.. In a direct current (dc) generator, the natural alternating current (ac) produced is rectified to dc by the commutator. DC is little used in standard electricity distribution systems but is used in industry for special applications. Alternating current electricity is generated at thermal power stations and also at nuclear power stations under the control of the present Central Electricity Generating Board which, under the privatization proposals, is divided into two "generating plcs." It is then transmitted by way of overhead lines at 400 kV, 232 kV or 132 kV to distribution substations where it is transformed down to 33 kV or 11 kV for distribution to large factories, or transformed down to 240 V for use in domestic and commercial premises and the smaller factories.

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