Electric power systemFrom Wikipedia, the free encyclopedia

A steam turbine used to provide electric power.Anelectric power systemis a network of electrical components used to supply, transmit and use electric power. An example of an electric power system is the network that supplies a region's homes and industry with powerfor sizable regions, this power system is known asthe gridand can be broadly divided into thegeneratorsthat supply the power, thetransmission systemthat carries the power from the generating centres to the load centres and thedistribution systemthat feeds the power to nearby homes and industries. Smaller power systems are also found in industry, hospitals, commercial buildings and homes. The majority of these systems rely uponthree-phase AC powerthe standard for large-scale power transmission and distribution across the modern world. Specialised power systems that do not always rely upon three-phase AC power are found in aircraft, electric rail systems, ocean liners and automobiles.Contents[hide] 1History 2Basics of electric power 3Balancing the grid 4Components of power systems 4.1Supplies 4.2Loads 4.3Conductors 4.4Capacitors and reactors 4.5Power electronics 4.6Protective devices 4.7SCADA systems 5Power systems in practice 5.1Residential power systems 5.2Commercial power systems 6References 7External linksHistory[edit]

A sketch of the Pearl Street StationIn 1881 two electricians built the world's first power system atGodalmingin England. It was powered by a power station consisting of two waterwheels that produced an alternating current that in turn supplied seven Siemensarc lampsat 250 volts and 34incandescent lampsat 40 volts.[1]However supply to the lamps was intermittent and in 1882Thomas Edisonand his company, The Edison Electric Light Company, developed the first steam powered electric power station on Pearl Street in New York City. ThePearl Street Stationinitially powered around 3,000 lamps for 59 customers.[2][3]The power station useddirect currentand operated at a single voltage. Direct current power could not be easily transformed to the higher voltages necessary to minimise power loss during long-distance transmission, so the maximum economic distance between the generators and load was limited to around half-a-mile (800 m).[4]That same year in LondonLucien GaulardandJohn Dixon Gibbsdemonstrated the first transformer suitable for use in a real power system. The practical value of Gaulard and Gibbs' transformer was demonstrated in 1884 atTurinwhere the transformer was used to light up forty kilometres (25 miles) of railway from a singlealternating currentgenerator.[5]Despite the success of the system, the pair made some fundamental mistakes. Perhaps the most serious was connecting the primaries of the transformers inseriesso that active lamps would affect the brightness of other lamps further down the line. Following the demonstrationGeorge Westinghouse, an American entrepreneur, imported a number of the transformers along with aSiemensgenerator and set his engineers to experimenting with them in the hopes of improving them for use in a commercial power system. In July 1888, Westinghouse also licensedNikola Tesla's US patents for a polyphase AC induction motor and transformer designs and hired Tesla for one year to be a consultant at theWestinghouse Electric & Manufacturing Company'sPittsburghlabs.[6]One of Westinghouse's engineers,William Stanley, recognised the problem with connecting transformers in series as opposed toparalleland also realised that making the iron core of a transformer a fully enclosed loop would improve thevoltage regulationof the secondary winding. Using this knowledge he built a much improved alternating current power system atGreat Barrington, Massachusettsin 1886.[7]By 1890 the electric power industry was flourishing, and power companies had built thousands of power systems (both direct and alternating current) in the United States and Europe. These networks were effectively dedicated to providing electric lighting. During this time a fierce rivalry known as the "War of Currents" emerged between Thomas Edison and George Westinghouse over which form of transmission (direct or alternating current) was superior.[8]In 1891, Westinghouse installed the first major power system that was designed to drive a 100 horsepower (75kW) synchronous electric motor, not just provide electric lighting, atTelluride, Colorado.[9]On the other side of the Atlantic,Oskar von Millerbuilt a 20 kV 176km three-phase transmission line fromLauffen am NeckartoFrankfurt am Mainfor the Electrical Engineering Exhibition in Frankfurt.[10]In 1895, after a protracted decision-making process, the Adams No. 1 generating station atNiagara Fallsbegan transferring three-phase alternating current power to Buffalo at 11 kV. Following completion of the Niagara Falls project, new power systems increasingly chosealternating currentas opposed todirect currentfor electrical transmission.[11]Developments in power systems continued beyond the nineteenth century. In 1936 the first experimentalHVDC(high voltage direct current) line usingmercury arc valveswas built betweenSchenectadyandMechanicville, New York. HVDC had previously been achieved by series-connected direct current generators and motors (theThury system) although this suffered from serious reliability issues.[12]In 1957Siemensdemonstrated the first solid-state rectifier, but it was not until the early 1970s that solid-state devices became the standard in HVDC.[13]In recent times, many important developments have come from extending innovations in theICTfield to the power engineering field. For example, the development of computers meantload flow studiescould be run more efficiently allowing for much better planning of power systems. Advances in information technology and telecommunication also allowed for remote control of a power system's switchgear and generators.Basics of electric power[edit]

An external AC to DC power adapter used for household appliancesElectric power is the product of two quantities:currentandvoltage. These two quantities can vary with respect to time (AC power) or can be kept at constant levels (DC power).Most refrigerators, air conditioners, pumps and industrial machinery use AC power whereas most computers and digital equipment use DC power (the digital devices you plug into the mains typically have an internal or external power adapter to convert from AC to DC power). AC power has the advantage of being easy to transform between voltages and is able to be generated and utilised by brushless machinery. DC power remains the only practical choice in digital systems and can be more economical to transmit over long distances at very high voltages (seeHVDC).[14][15]The ability to easily transform the voltage of AC power is important for two reasons: Firstly, power can be transmitted over long distances with less loss at higher voltages. So in power systems where generation is distant from the load, it is desirable to step-up (increase) the voltage of power at the generation point and then step-down (decrease) the voltage near the load. Secondly, it is often more economical to install turbines that produce higher voltages than would be used by most appliances, so the ability to easily transform voltages means this mismatch between voltages can be easily managed.[14]Solid state devices, which are products of the semiconductor revolution, make it possible to transformDC power to different voltages, buildbrushless DC machinesandconvert between AC and DC power. Nevertheless devices utilising solid state technology are often more expensive than their traditional counterparts, so AC power remains in widespread use.[16]Balancing the grid[edit]One of the main difficulties in power systems is that the amount of active power consumed plus losses should always equal the active power produced. If more power would be produced than consumed the frequency would rise and vice versa. Even small deviations from the nominal frequency value would damage synchronous machines and other appliances. Making sure the frequency is constant is usually the task of atransmission system operator. In some countries (for example in theEuropean Union) this is achieved through abalancing marketusingancillary services.[17]Components of power systems[edit]Supplies[edit]

The majority of the world's power still comes fromcoal-fired power stationslike this.All power systems have one or more sources of power. For some power systems, the source of power is external to the system but for others it is part of the system itselfit is these internal power sources that are discussed in the remainder of this section. Direct current power can be supplied bybatteries,fuel cellsorphotovoltaic cells. Alternating current power is typically supplied by a rotor that spins in a magnetic field in a device known as aturbo generator. There have been a wide range of techniques used to spin a turbine's rotor, from steam heated usingfossil fuel(including coal, gas and oil) ornuclear energy, falling water (hydroelectric power) and wind (wind power).The speed at which the rotor spins in combination with the number of generator poles determines the frequency of the alternating current produced by the generator. All generators on a single synchronous system, for example thenational grid, rotate at sub-multiples of the same speed and so generate electrical current at the same frequency. If the load on the system increases, the generators will require more torque to spin at that speed and, in a typical power station, more steam must be supplied to the turbines driving them. Thus the steam used and the fuel expended are directly dependent on the quantity of electrical energy supplied. An exception exists for generators incorporating power electronics such asgearless wind turbinesor linked to a grid through an asynchronous tie such as aHVDClink these can operate at frequencies independent of the power system frequency.Depending on how the poles are fed, alternating current generators can produce a variable number of phases of power. A higher number of phases leads to more efficient power system operation but also increases the infrastructure requirements of the system.[18]Electricity grid systems connect multiple generators and loads operating at the same frequency and number of phases, the commonest being three-phase at 50 or 60Hz. However there are other considerations. These range from the obvious: How much power should the generator be able to supply? What is an acceptable length of time for starting the generator (some generators can take hours to start)? Is the availability of the power source acceptable (some renewables are only available when the sun is shining or the wind is blowing)? To the more technical: How should the generator start (some turbines act like a motor to bring themselves up to speed in which case they need an appropriate starting circuit)? What is the mechanical speed of operation for the turbine and consequently what are the number of poles required? What type of generator is suitable (synchronousorasynchronous) and what type of rotor (squirrel-cage rotor, wound rotor, salient pole rotor or cylindrical rotor)?[19]Loads[edit]

Atoasteris great example of a single-phase load that might appear in a residence. Toasters typically draw 2 to 10 amps at 110 to 260 volts consuming around 600 to 1200 watts of powerPower systems deliver energy to loads that perform a function. These loads range from household appliances to industrial machinery. Most loads expect a certain voltage and, for alternating current devices, a certain frequency and number of phases. The appliances found in your home, for example, will typically be single-phase operating at 50 or 60Hz with a voltage between 110 and 260 volts (depending on national standards). An exception exists for centralized air conditioning systems as these are now typically three-phase because this allows them to operate more efficiently. All devices in your house will also have a wattage, this specifies the amount of power the device consumes. At any one time, the net amount of power consumed by the loads on a power system must equal the net amount of power produced by the supplies less the power lost in transmission.[20][21]Making sure that the voltage, frequency and amount of power supplied to the loads is in line with expectations is one of the great challenges of power system engineering. However it is not the only challenge, in addition to the power used by a load to do useful work (termedreal power) many alternating current devices also use an additional amount of power because they cause the alternating voltage and alternating current to become slightly out-of-sync (termedreactive power). The reactive power like the real power must balance (that is the reactive power produced on a system must equal the reactive power consumed) and can be supplied from the generators, however it is often more economical to supply such power from capacitors (see "Capacitors and reactors" below for more details).[22]A final consideration with loads is to do with power quality. In addition to sustained overvoltages and undervoltages (voltage regulation issues) as well as sustained deviations from the system frequency (frequency regulation issues), power system loads can be adversely affected by a range of temporal issues. These include voltage sags, dips and swells, transient overvoltages, flicker, high frequency noise, phase imbalance and poor power factor.[23]Power quality issues occur when the power supply to a load deviates from the ideal: For an AC supply, the ideal is the current and voltage in-sync fluctuating as a perfect sine wave at a prescribed frequency with the voltage at a prescribed amplitude. For DC supply, the ideal is the voltage not varying from a prescribed level. Power quality issues can be especially important when it comes to specialist industrial machinery or hospital equipment.Conductors[edit]Conductors carry power from the generators to the load. In agrid, conductors may be classified as belonging to thetransmission system, which carries large amounts of power at high voltages (typically more than 69 kV) from the generating centres to the load centres, or thedistribution system, which feeds smaller amounts of power at lower voltages (typically less than 69 kV) from the load centres to nearby homes and industry.[24]Choice of conductors is based upon considerations such as cost, transmission losses and other desirable characteristics of the metal like tensile strength.Copper, with lower resistivity than aluminium, was the conductor of choice for most power systems. However, aluminum has lower cost for the same current carrying capacity and is the primary metal used for transmission line conductors.Overhead lineconductors may be reinforced with steel or aluminum alloys.[25]Conductors in exterior power systems may be placed overhead or underground. Overhead conductors are usually air insulated and supported on porcelain, glass or polymer insulators. Cables used for underground transmission orbuilding wiringare insulated withcross-linked polyethyleneor other flexible insulation. Large conductors are stranded for ease of handling; small conductors used for building wiring are often solid, especially in light commercial or residential construction.[26]Conductors are typically rated for the maximum current that they can carry at a given temperature rise over ambient conditions. As current flow increases through a conductor it heats up. For insulated conductors, the rating is determined by the insulation.[27]For overhead conductors, the rating is determined by the point at which the sag of the conductors would become unacceptable.[28]Capacitors and reactors[edit]The majority of the load in a typical AC power system is inductive; the current lags behind the voltage. Since the voltage and current are out-of-phase, this leads to the emergence of an "imaginary" form of power known asreactive power. Reactive power does no measurable work but is transmitted back and forth between the reactive power source and load every cycle. This reactive power can be provided by the generators themselves, through the adjustment of generator excitation, but it is often cheaper to provide it through capacitors, hence capacitors are often placed near inductive loads to reduce current demand on the power system (i.e., increase thepower factor), which may never exceed 1.0, and which represents a purely resistive load. Power factor correction may be applied at a central substation, through the use of so-called "synchronous condensers" (synchronous machines which act as condensers which are variable inVARvalue, through the adjustment of machine excitation) or adjacent to large loads, through the use of so-called "static condensers" (condensers which are fixed in VAR value).Reactors consume reactive power and are used to regulate voltage on long transmission lines. In light load conditions, where the loading on transmission lines is well below thesurge impedance loading, the efficiency of the power system may actually be improved by switching in reactors. Reactors installed in series in a power system also limit rushes of current flow, small reactors are therefore almost always installed in series with capacitors to limit the current rush associated with switching in a capacitor. Series reactors can also be used to limit fault currents.Capacitors and reactors are switched by circuit breakers, which results in moderately large steps in reactive power. A solution comes in the form ofstatic VAR compensatorsandstatic synchronous compensators. Briefly, static VAR compensators work by switching in capacitors using thyristors as opposed to circuit breakers allowing capacitors to be switched-in and switched-out within a single cycle. This provides a far more refined response than circuit breaker switched capacitors. Static synchronous compensators take a step further by achieving reactive power adjustments using onlypower electronics.Power electronics[edit]Power electronics are semi-conductor based devices that are able to switch quantities of power ranging from a few hundred watts to several hundred megawatts. Despite their relatively simple function, their speed of operation (typically in the order of nanoseconds[29]) means they are capable of a wide range of tasks that would be difficult or impossible with conventional technology. The classic function of power electronics isrectification, or the conversion of AC-to-DC power, power electronics are therefore found in almost every digital device that is supplied from an AC source either as an adapter that plugs into the wall (see photo inBasics of Electric Powersection) or as component internal to the device. High-powered power electronics can also be used to convert AC power to DC power for long distance transmission in a system known asHVDC. HVDC is used because it proves to be more economical than similar high voltage AC systems for very long distances (hundreds to thousands of kilometres). HVDC is also desirable for interconnects because it allows frequency independence thus improving system stability. Power electronics are also essential for any power source that is required to produce an AC output but that by its nature produces a DC output. They are therefore used by many photovoltaic installations both industrial and residential.Power electronics also feature in a wide range of more exotic uses. They are at the heart of all modern electric and hybrid vehicleswhere they are used for both motor control and as part of thebrushless DC motor. Power electronics are also found in practically all modern petrol-powered vehicles, this is because the power provided by the car's batteries alone is insufficient to provide ignition, air-conditioning, internal lighting, radio and dashboard displays for the life of the car. So the batteries must be recharged while driving using DC power from the enginea feat that is typically accomplished using power electronics. Whereas conventional technology would be unsuitable for a modern electric car, commutators can and have been used in petrol-powered cars, the switch toalternatorsin combination with power electronics has occurred because of the improved durability of brushless machinery.[30]Some electric railway systems also use DC power and thus make use of power electronics to feed grid power to the locomotives and often for speed control of the locomotive's motor. In the middle twentieth century,rectifier locomotiveswere popular, these used power electronics to convert AC power from the railway network for use by a DC motor.[31]Today most electric locomotives are supplied with AC power and run using AC motors, but still use power electronics to provide suitable motor control. The use of power electronics to assist with motor control and with starter circuits cannot be underestimated and, in addition to rectification, is responsible for power electronics appearing in a wide range of industrial machinery. Power electronics even appear in modern residential air conditioners.Power electronics are also at the heart of thevariable speed wind turbine. Conventional wind turbines require significant engineering to ensure they operate at some ratio of the system frequency, however by using power electronics this requirement can be eliminated leading to quieter, more flexible and (at the moment) more costly wind turbines. A final example of one of the more exotic uses of power electronics comes from the previous section where the fast-switching times of power electronics were used to provide more refined reactive compensation to the power system.Protective devices[edit]Main article:power system protectionPower systems contain protective devices to prevent injury or damage during failures. The quintessential protective device is the fuse. When the current through a fuse exceeds a certain threshold, the fuse element melts, producing an arc across the resulting gap that is then extinguished, interrupting the circuit. Given that fuses can be built as the weak point of a system, fuses are ideal for protecting circuitry from damage. Fuses however have two problems: First, after they have functioned, fuses must be replaced as they cannot be reset. This can prove inconvenient if the fuse is at a remote site or a spare fuse is not on hand. And second, fuses are typically inadequate as the sole safety device in most power systems as they allow current flows well in excess of that that would prove lethal to a human or animal.The first problem is resolved by the use ofcircuit breakersdevices that can be reset after they have broken current flow. In modern systems that use less than about 10kW, miniature circuit breakers are typically used. These devices combine the mechanism that initiates the trip (by sensing excess current) as well as the mechanism that breaks the current flow in a single unit. Some miniature circuit breakers operate solely on the basis of electromagnetism. In these miniature circuit breakers, the current is run through a solenoid, and, in the event of excess current flow, the magnetic pull of the solenoid is sufficient to force open the circuit breaker's contacts (often indirectly through a tripping mechanism). A better design however arises by inserting a bimetallic strip before the solenoidthis means that instead of always producing a magnetic force, the solenoid only produces a magnetic force when the current is strong enough to deform the bimetallic strip and complete the solenoid's circuit.In higher powered applications, theprotective relaysthat detect a fault and initiate a trip are separate from the circuit breaker. Early relays worked based upon electromagnetic principles similar to those mentioned in the previous paragraph,modern relaysare application-specific computers that determine whether to trip based upon readings from the power system. Different relays will initiate trips depending upon differentprotection schemes. For example, an overcurrent relay might initiate a trip if the current on any phase exceeds a certain threshold whereas a set of differential relays might initiate a trip if the sum of currents between them indicates there may be current leaking to earth. The circuit breakers in higher powered applications are different too. Air is typically no longer sufficient to quench the arc that forms when the contacts are forced open so a variety of techniques are used. One of the most popular techniques is to keep the chamber enclosing the contacts flooded withsulfur hexafluoride(SF6)a non-toxic gas that has sound arc-quenching properties. Other techniques are discussed in the reference.[32]The second problem, the inadequacy of fuses to act as the sole safety device in most power systems, is probably best resolved by the use of residual current devices (RCDs). In any properly functioning electrical appliance the current flowing into the appliance on the active line should equal the current flowing out of the appliance on the neutral line. A residual current device works by monitoring the active and neutral lines and tripping the active line if it notices a difference.[33]Residual current devices require a separate neutral line for each phase and to be able to trip within a time frame before harm occurs. This is typically not a problem in most residential applications where standard wiring provides an active and neutral line for each appliance (that's why your power plugs always have at least two tongs) and the voltages are relatively low however these issues do limit the effectiveness of RCDs in other applications such as industry. Even with the installation of an RCD, exposure to electricity can still prove lethal.SCADA systems[edit]In large electric power systems,Supervisory Control And Data Acquisition(SCADA) is used for tasks such as switching on generators, controlling generator output and switching in or out system elements for maintenance. The first supervisory control systems implemented consisted of a panel of lamps and switches at a central console near the controlled plant. The lamps provided feedback on the state of plant (the data acquisition function) and the switches allowed adjustments to the plant to be made (the supervisory control function). Today, SCADA systems are much more sophisticated and, due to advances in communication systems, the consoles controlling the plant no longer need to be near the plant itself. Instead it is now common for plant to be controlled from a with equipment similar to (if not identical to) a desktop computer. The ability to control such plant through computers has increased the need for security and already there have been reports of cyber-attacks on such systems causing significant disruptions to power systems.[34]Power systems in practice[edit]Despite their common components, power systems vary widely both with respect to their design and how they operate. This section introduces some common power system types and briefly explains their operation.Residential power systems[edit]Residential dwellings almost always take supply from the low voltage distribution lines or cables that run past the dwelling. These operate at voltages of between 110 and 260 volts (phase-to-earth) depending upon national standards. A few decades ago small dwellings would be fed a single phase using a dedicated two-core service cable (one core for the active phase and one core for the neutral return). The active line would then be run through a main isolating switch in thefuse boxand then split into one or more circuits to feed lighting and appliances inside the house. By convention, the lighting and appliance circuits are kept separate so the failure of an appliance does not leave the dwelling's occupants in the dark. All circuits would be fused with an appropriate fuse based upon the wire size used for that circuit. Circuits would have both an active and neutral wire with both the lighting and power sockets being connected in parallel. Sockets would also be provided with a protective earth. This would be made available to appliances to connect to any metallic casing. If this casing were to become live, the theory is the connection to earth would cause an RCD or fuse to tripthus preventing the future electrocution of an occupant handling the appliance.Earthing systemsvary between regions, but in countries such as the United Kingdom and Australia both the protective earth and neutral line would be earthed together near the fuse box before the main isolating switch and the neutral earthed once again back at the distribution transformer.[35]There have been a number of minor changes over the year to practice of residential wiring. Some of the most significant ways modern residential power systems tend to vary from older ones include: For convenience, miniature circuit breakers are now almost always used in the fuse box instead of fuses as these can easily be reset by occupants. For safety reasons, RCDs are now installed on appliance circuits and, increasingly, even on lighting circuits. Dwellings are typically connected to all three-phases of the distribution system with the phases being arbitrarily allocated to the house's single-phase circuits. Whereas air conditioners of the past might have been fed from a dedicated circuit attached to a single phase, centralised air conditioners that require three-phase power are now becoming common. Protective earths are now run with lighting circuits to allow for metallic lamp holders to be earthed. Increasingly residential power systems are incorporatingmicrogenerators, most notably, photovoltaic cells.Commercial power systems[edit]Commercial power systems such as shopping centers or high-rise buildings are larger in scale than residential systems. Electrical designs for larger commercial systems are usually studied for load flow, short-circuit fault levels, and voltage drop for steady-state loads and during starting of large motors. The objectives of the studies are to assure proper equipment and conductor sizing, and to coordinate protective devices so that minimal disruption is cause when a fault is cleared. Large commercial installations will have an orderly system of sub-panels, separate from the main distribution board to allow for better system protection and more efficient electrical installation.Typically one of the largest appliances connected to a commercial power system is the HVAC unit, and ensuring this unit is adequately supplied is an important consideration in commercial power systems. Regulations for commercial establishments place other requirements on commercial systems that are not placed on residential systems. For example, in Australia, commercial systems must comply with AS 2293, the standard for emergency lighting, which requires emergency lighting be maintained for at least 90 minutes in the event of loss of mains supply.[36]In the United States, theNational Electrical Coderequires commercial systems to be built with at least one 20A sign outlet in order to light outdoor signage.[37]Building code regulations may place special requirements on the electrical system for emergency lighting, evacuation, emergency power, smoke control and fire protection.Athermodynamic systemis the content of amacroscopicvolume in space, along with itswallsandsurroundings; it undergoesthermodynamic processesaccording to the principles ofthermodynamics. Aphysical systemqualifies as a thermodynamic system only if it can be adequately described by thermodynamic variables such as temperature, entropy, internal energy and pressure.Thethermodynamic stateof a thermodynamic system is its internal state as specified by itsstate variables. A thermodynamic account also requires a special kind of function called a state function. For example, if the state variables are internal energy, volume and mole amounts, the needed further state function is entropy. These quantities are inter-related by one or more functional relationships calledequations of state. Thermodynamics defines the restrictions on the possible equations of state imposed by thelaws of thermodynamicsthrough that further function of state.The system is delimited by walls or boundaries, either actual or notional, across which conserved (such as matter and energy) or unconserved (such as entropy) quantities can pass into and out of the system. The space outside the thermodynamic system is known as thesurroundings, areservoir, or theenvironment. The properties of the walls determine what transfers can occur. A wall that allows transfer of a quantity is said to be permeable to it, and a thermodynamic system is classified by the permeabilities of its several walls. A transfer between system and surroundings can arise by contact, such as conduction of heat, or by long-range forces such as an electric field in the surroundings.by types of wall

Types of transfers permittedtype of walltype of transfer

Massand energyWorkHeat

permeable to matter

permeable to energy butimpermeable to matter

adiabatic

adynamic andimpermeable to matter

isolating

A system with walls that prevent all transfers is said to beisolated. This is an idealized conception, because in practice some transfer is always possible, for example by gravitational forces. It is an axiom of thermodynamics that an isolated system eventually reaches internalthermodynamic equilibrium, when its state no longer changes with time.According to the permeabilities of its walls, a system that is not isolated can be in thermodynamic equilibrium with its surroundings, or else may be in a state that is constant or precisely cyclically changing in time - asteady statethat is far from equilibrium. Classical thermodynamics considers only states of thermodynamic systems in equilibrium that are either constant or precisely cycling in time.The walls of aclosed systemallow transfer of energy as heat and as work, but not of matter, between it and its surroundings. The walls of anopen systemallow transfer both of matter and of energy.[1][2][3][4][5][6][7]This scheme of definition of terms is not uniformly used, though it is convenient for some purposes. In particular, some writers use 'closed system' where 'isolated system' is here used.[8][9]In 1824Sadi Carnotdescribed a thermodynamic system as theworking substance(such as the volume of steam) of any heat engine under study. The very existence of such thermodynamic systems may be considered a fundamental postulate of equilibrium thermodynamics, though it is not listed as a numbered law.[10][11]According to Bailyn, the commonly rehearsed statement of thezeroth law of thermodynamicsis a consequence of this fundamental postulate.[12]In equilibrium thermodynamics the state variables do not include fluxes because in a state of thermodynamic equilibrium all fluxes have zero values by definition. Equilibrium thermodynamic processes may of course involve fluxes but these must have ceased by the time a thermodynamic process or operation is complete bringing a system to its eventual thermodynamic state. Non-equilibrium thermodynamics allows its state variables to include non-zero fluxes, that describe transfers ofmatterorenergyorentropybetween asystemand its surroundings.[13]Contents[hide] 1Overview 2History 3Walls 4Surroundings 5Open system 5.1Flow process 5.2Selective transfer of matter 6Closed system 7Isolated system 8Mechanically isolated system 9Systems in equilibrium 10See also 11References 12External linksOverview[edit]Thermodynamics

The classicalCarnot heat engine

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Book:Thermodynamics

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Thermodynamics describes the macroscopic physics of matter and energy, especially including heat transfer, by using the concept of thethermodynamic system, a region of the universe that is under study, specified by thermodynamic state variables, together with the kinds of transfer that may occur between it and its surroundings, as determined by the physical properties of the walls of the system.An example system is the system of hot liquid water and solidtable saltin a sealed, insulated test tube held in a vacuum (the surroundings). The test tube constantly loses heat in the form ofblack-body radiation, but the heat loss progresses very slowly. If there is another process going on in the test tube, for example thedissolutionof the saltcrystals, it probably occurs so quickly that any heat lost to the test tube during that time can be neglected. Thermodynamics in general does not measure time, but it does sometimes accept limitations on the time frame of a process.History[edit]The first to develop the concept of a thermodynamic system was the French physicistSadi Carnotwhose 1824Reflections on the Motive Power of Firestudied what he called theworking substance, e.g., typically a body of water vapor, insteam engines, in regards to the system's ability to do work when heat is applied to it. The working substance could be put in contact with either a heat reservoir (a boiler), a cold reservoir (a stream of cold water), or a piston (to which the working body could do work by pushing on it). In 1850, the German physicistRudolf Clausiusgeneralized this picture to include the concept of the surroundings, and began referring to the system as a "working body." In his 1850 manuscriptOn the Motive Power of Fire, Clausius wrote:"With every change of volume (to the working body) a certain amountworkmust be done by the gas or upon it, since by its expansion it overcomes an external pressure, and since its compression can be brought about only by an exertion of external pressure. To this excess of work done by the gas or upon it there must correspond, by our principle, a proportional excess ofheatconsumed or produced, and the gas cannot give up to the "surrounding medium" the same amount of heat as it receives."

The articleCarnot heat engineshows the original piston-and-cylinder diagram used by Carnot in discussing his ideal engine; below, we see the Carnot engine as is typically modeled in current use:

Carnot engine diagram (modern) - where heat flows from a high temperatureTHfurnace through the fluid of the "working body" (working substance) and into the cold sinkTC, thus forcing the working substance to domechanical workWon the surroundings, via cycles of contractions and expansions.In the diagram shown, the "working body" (system), a term introduced by Clausius in 1850, can be any fluid or vapor body through whichheatQcan be introduced or transmitted through to producework. In 1824, Sadi Carnot, in his famous paperReflections on the Motive Power of Fire, had postulated that the fluid body could be any substance capable of expansion, such as vapor of water, vapor of alcohol, vapor of mercury, a permanent gas, or air, etc. Though, in these early years, engines came in a number of configurations, typicallyQHwas supplied by a boiler, wherein water boiled over a furnace;QCwas typically a stream of cold flowing water in the form of acondenserlocated on a separate part of the engine. The output workWwas the movement of the piston as it turned a crank-arm, which typically turned a pulley to lift water out of flooded salt mines. Carnot defined work as "weight lifted through a height."Walls[edit]A system is enclosed by walls that bound it and connect it to its surroundings.[14][15][16][17][18][19]Often a wall restricts passage across it by some form of matter or energy, making the connection indirect. Sometimes a wall is no more than an imaginary two-dimensional closed surface through which the connection to the surroundings is direct.Topologically, it is often considered nearly or piecewise smoothlyhomeomorphicwith atwo-sphere(ordinary sphere like a surface that forms the boundary of a ball in three dimensions), because a system is often consideredsimply connected.A wall can be fixed (e.g. a constant volume reactor) or moveable (e.g. a piston). For example, in a reciprocating engine, a fixed wall means the piston is locked at its position; then, a constant volume process may occur. In that same engine, a piston may be unlocked and allowed to move in and out. Ideally, a wall may be declaredadiabatic,diathermal, impermeable, permeable, orsemi-permeable. Actual physical materials that provide walls with such idealized properties are not always readily available.Anything that passes across the boundary and effects a change in the contents of the system must be accounted for in an appropriate balance equation. The volume can be the region surrounding a single atom resonating energy, such asMax Planckdefined in 1900; it can be a body of steam or air in asteam engine, such asSadi Carnotdefined in 1824. It could also be just one nuclide (i.e. a system ofquarks) as hypothesized inquantum thermodynamics.Surroundings[edit]See also:Environment (systems)The system is the part of the universe being studied, while thesurroundingsis the remainder of the universe that lies outside the boundaries of the system. It is also known as theenvironment, and thereservoir. Depending on the type of system, it may interact with the system by exchanging mass, energy (including heat and work),momentum,electric charge, orother conserved properties. The environment is ignored in analysis of the system, except in regards to these interactions.Open system[edit]

Generic open systemscheme. Exchanges of matter or energy with system's surroundings are represented by input and output flows.In anopen system, matter may flow in and out of some segments of the system boundaries. There may be other segments of the system boundaries that pass heat or work but not matter. Respective account is kept of the transfers of energy across those and any other several boundary segments.Flow process[edit]

Duringsteady, continuousoperation, an energy balance applied to an open system equates shaft work performed by the system to heat added plus netenthalpyadded.The region of space enclosed by open system boundaries is usually called acontrol volume. It may or may not correspond to physical walls. It is convenient to define the shape of the control volume so that all flow of matter, in or out, occurs perpendicular to its surface. One may consider a process in which the matter flowing into and out of the system is chemically homogeneous.[20]Then the inflowing matter performs work as if it were driving a piston of fluid into the system. Also, the system performs work as if it were driving out a piston of fluid. Through the system walls that do not pass matter, heat (Q) and work (W) transfers may be defined, including shaft work.Classical thermodynamics considers processes for a system that is initially and finally in its own internal state of thermodynamic equilibrium, with no flow. This is feasible also under some restrictions, if the system is a mass of fluid flowing at a uniform rate. Then for many purposes a process, called a flow process, may be considered in accord with classical thermodynamics as if the classical rule of no flow were effective.[21]For the present introductory account, it is supposed that the kinetic energy of flow, and the potential energy of elevation in the gravity field, do not change, and that the walls, other than the matter inlet and outlet, are rigid and motionless.Under these conditions, the first law of thermodynamics for a flow process states:the increase in the internal energy of a system is equal to the amount of energy added to the system by matter flowing in and by heating, minus the amount lost by matter flowing out and in the form of work done by the system.Under these conditions, the first law for a flow process is written:

whereUinandUoutrespectively denote the averageinternal energyentering and leaving the system with the flowing matter.There are then two types of work performed: 'flow work' described above, which is performed on the fluid in the control volume (this is also often called 'PVwork'), and 'shaft work', which may be performed by the fluid in the control volume on somemechanical devicewith a shaft. These two types of work are expressed in the equation:

Substitution into the equation above for the control volumecvyields:

The definition ofenthalpy,H=U+PV, permits us to use thisthermodynamic potentialto account jointly for internal energyUandPVwork in fluids for a flow process:

Duringsteady-stateoperation of a device (seeturbine,pump, andengine), any system property within the control volume is independent of time. Therefore, the internal energy of the system enclosed by the control volume remains constant, which implies thatdUcvin the expression above may be set equal to zero. This yields a useful expression for thepowergeneration or requirement for these devices with chemical homogeneity in the absence ofchemical reactions:

This expression is described by the diagram above.Selective transfer of matter[edit]For a thermodynamic process, the precise physical properties of the walls and surroundings of the system are important, because they determine the possible processes.An open system has one or several walls that allow transfer of matter. To account for the internal energy of the open system, this requires energy transfer terms in addition to those for heat and work. It also leads to the idea of thechemical potential.A wall selectively permeable only to a pure substance can put the system in diffusive contact with a reservoir of that pure substance in the surroundings. Then a process is possible in which that pure substance is transferred between system and surroundings. Also, across that wall a contact equilibrium with respect to that substance is possible. By suitablethermodynamic operations, the pure substance reservoir can be dealt with as a closed system. Its internal energy and its entropy can be determined as functions of its temperature, pressure, and mole number.A thermodynamic operation can render impermeable to matter all system walls other than the contact equilibrium wall for that substance. This allows the definition of an intensive state variable, with respect to a reference state of the surroundings, for that substance. The intensive variable is called the chemical potential; for component substanceiit is usually denotedi. The corresponding extensive variable can be the number of molesNiof the component substance in the system.For a contact equilibrium across a wall permeable to a substance, the chemical potentials of the substance must be same on either side of the wall. This is part of the nature of thermodynamic equilibrium, and may be regarded as related to the zeroth law of thermodynamics.[22]Closed system[edit]Main article:Closed system In thermodynamicsIn a closed system, no mass may be transferred in or out of the system boundaries. The system always contains the same amount of matter, but heat and work can be exchanged across the boundary of the system. Whether a system can exchange heat, work, or both is dependent on the property of its boundary. Adiabatic boundary not allowing any heat exchange: Athermally isolated system Rigid boundary not allowing exchange of work: Amechanically isolated systemOne example is fluid being compressed by a piston in a cylinder. Another example of a closed system is a bomb calorimeter, a type of constant-volume calorimeter used in measuring the heat of combustion of a particular reaction. Electrical energy travels across the boundary to produce a spark between the electrodes and initiates combustion. Heat transfer occurs across the boundary after combustion but no mass transfer takes place either way.Beginning with the first law of thermodynamics for an open system, this is expressed as:

whereUis internal energy,Qis the heat added to the system,Wis the work done by the system, and since no mass is transferred in or out of the system, both expressions involving mass flow are zero and the first law of thermodynamics for a closed system is derived. The first law of thermodynamics for a closed system states that the increase of internal energy of the system equals the amount of heat added to the system minus the work done by the system. For infinitesimal changes the first law for closed systems is stated by:

If the work is due to a volume expansion by dVat a pressurePthan:

For a homogeneous system, in which only reversible processes can take place, the second law of thermodynamics reads:

whereTis the absolute temperature andSis the entropy of the system. With these relations the fundamental thermodynamic relationship, used to compute changes in internal energy, is expressed as:

For a simple system, with only one type of particle (atom or molecule), a closed system amounts to a constant number of particles. However, for systems undergoing achemical reaction, there may be all sorts of molecules being generated and destroyed by the reaction process. In this case, the fact that the system is closed is expressed by stating that the total number of each elemental atom is conserved, no matter what kind of molecule it may be a part of. Mathematically:

whereNjis the number of j-type molecules,aijis the number of atoms of elementiin moleculejandbi0is the total number of atoms of elementiin the system, which remains constant, since the system is closed. There is one such equation for each element in the system.Isolated system[edit]Main article:Isolated systemAn isolated system is more restrictive than a closed system as it does not interact with its surroundings in any way. Mass and energy remains constant within the system, and no energy or mass transfer takes place across the boundary. As time passes in an isolated system, internal differences in the system tend to even out and pressures and temperatures tend to equalize, as do density differences. A system in which all equalizing processes have gone practically to completion is in a state ofthermodynamic equilibrium.Truly isolated physical systems do not exist in reality (except perhaps for the universe as a whole), because, for example, there is always gravity between a system with mass and masses elsewhere.[23][24][25][26][27]However, real systems may behave nearly as an isolated system for finite (possibly very long) times. The concept of an isolated system can serve as a usefulmodelapproximating many real-world situations. It is an acceptableidealizationused in constructingmathematical modelsof certain naturalphenomena.In the attempt to justify the postulate ofentropyincrease in thesecond law of thermodynamics, BoltzmannsH-theoremusedequations, which assumed that a system (for example, agas) was isolated. That is all the mechanicaldegrees of freedomcould be specified, treating the walls simply asmirrorboundary conditions. This inevitably led toLoschmidt's paradox. However, if thestochasticbehavior of themoleculesin actual walls is considered, along with therandomizingeffect of the ambient, backgroundthermal radiation, Boltzmanns assumption ofmolecular chaoscan be justified.The second law of thermodynamics for isolated systems states that the entropy of an isolated system not in equilibrium tends to increase over time, approaching maximum value at equilibrium. Overall, in an isolated system, the internal energy is constant and the entropy can never decrease. Aclosedsystem's entropy can decrease e.g. when heat is extracted from the system.It is important to note that isolated systems are not equivalent to closed systems. Closed systems cannot exchange matter with the surroundings, but can exchange energy. Isolated systems can exchange neither matter nor energy with their surroundings, and as such are only theoretical and do not exist in reality (except, possibly, the entire universe).It is worth noting that 'closed system' is often used in thermodynamics discussions when 'isolated system' would be correct - i.e. there is an assumption that energy does not enter or leave the system.Mechanically isolated system[edit]Main article:Mechanically isolated systemA mechanically isolated system can exchange no work energy with its environment, but may exchange heat energy and/or mass with its environment. The internal energy of a mechanically isolated system may therefore change due to the exchange of heat energy and mass. For a simple system, mechanical isolation is equivalent to constant volume and any process which occurs in such a simple system is said to beisochoric.Systems in equilibrium[edit]Atthermodynamic equilibrium, a system's properties are, by definition, unchanging in time. Systems in equilibrium are much simpler and easier to understand than systems not in equilibrium. In some cases, when analyzing athermodynamic process, one can assume that each intermediate state in the process is at equilibrium. This considerably simplifies the analysis.In isolated systems it is consistently observed that as time goes on internal rearrangements diminish and stable conditions are approached. Pressures and temperatures tend to equalize, and matter arranges itself into one or a few relatively homogeneousphases. A system in which all processes of change have gone practically to completion is considered in a state ofthermodynamic equilibrium. The thermodynamic properties of a system in equilibrium are unchanging in time. Equilibrium system states are much easier to describe in a deterministic manner than non-equilibrium states.For a process to bereversible, each step in the process must be reversible. For a step in a process to be reversible, the system must be in equilibrium throughout the step. That ideal cannot be accomplished in practice because no step can be taken without perturbing the system from equilibrium, but the ideal can be approached by making changes slowly.Bioenergetic systemsaremetabolicprocesses which relate to the flow of energy in the living organisms. Those processes convert the energy intoadenosine triphosphate, which is the form of chemical energy suitable for muscular activity. There are two main forms of synthesis of adenosine triphosphate:aerobic, which involves oxygen from the bloodstream, andanaerobic, which does not.Bioenergeticsis the field of biology which studies the bioenergetic systems.Contents[hide] 1Overview 2Adenosine triphosphate 3The principle of coupled reactions 4Aerobic and anaerobic metabolism 5ATPCP: the phosphagen system 6Anaerobic system 7Aerobic system 8How they work 9References 10Further readingOverview[edit]The cellular respiration process that converts food energy into adenosine triphosphate (a form of energy) is largely dependent on the availability of oxygen. During exercise, the supply and demand of oxygen available to muscle cells is affected by the duration and intensity of the exercise and by the individual's cardiorespiratory fitness level. There are three exercise energy systems that can be selectively recruited, depending on the amount of oxygen available, as part of the cellular respiration process to generate the ATP energy for the muscles. They are adenosine triphosphate, the anaerobic system and the aerobic system.Adenosine triphosphate[edit]Adenosine triphosphate(ATP) is the usable form ofchemical energyfor muscular activity. It is stored in most cells, particularly in muscle cells. Other forms of chemical energy, such as those available from food, must be transferred into ATP form before they can be utilized by the muscle cells.[1]The principle of coupled reactions[edit]Since energy is released when ATP is broken down, energy is required to rebuild or resynthesize ATP. The building blocks of ATP synthesis are the by-products of its breakdown;adenosine diphosphate(ADP) andinorganic phosphate(Pi). The energy for ATP resynthesis comes from three different series of chemical reactions that take place within the body. Two of the three depend upon the food we eat, whereas the other depends upon a chemical compound calledphosphocreatine. The energy released from any of these three series of hi reactions is coupled with the energy needs of the reaction that resynthesizes ATP. The separate reactions are functionally linked together in such a way that the energy released by the one is always used by the other.[2]There are three methods to resynthesize ATP: ATPCP system (phosphogen system) This system is used only for very short durations of up to 10 seconds. The ATPCP system neither usesoxygennor produceslactic acidif oxygen is unavailable and is thus said to be alactic anaerobic. This is the primary system behind very short, powerful movements like a golf swing, a 100m sprint, or powerlifting. Anaerobic system Predominates in supplying energy for exercises lasting less than two minutes. Also known as theglycolytic system. An example of an activity of the intensity and duration that this system works under would be a 400 m sprint. Aerobic system This is the long-duration energy system. By five minutes of exercise, the O2system is clearly the dominant system. In a 1km run, this system is already providing approximately half the energy; in amarathonrun it provides 98% or more.[3]Aerobic and anaerobic metabolism[edit]The term metabolism refers to the various series of chemical reactions that take place within the body. Aerobic refers to the presence of oxygen, whereas anaerobic means with series of chemical reactions that does not require the presence of oxygen. The ATP-CP series and the lactic acid series are anaerobic, whereas the oxygen series, is aerobic.[4]ATPCP: the phosphagen system[edit]

(A) Phosphocreatine, which is stored in muscle cells, contains a high energy bond. (B) When creatine phosphate is broken down during muscular contraction, a large amount of energy is released. The energy released is coupled with the energy requirement to resynthesize ATP.Creatine phosphate(CP), like ATP, is stored in the muscle cells. When it is broken down, a large amount of energy is released. The energy released is coupled to the energy requirement necessary for the resynthesis of ATP.The total muscular stores of both ATP and CP are very small. Thus, the amount of energy obtainable through this system is limited. If an individual were to run 100 meters as fast as they could, the phosphagen stores in the working muscles would probably be exhausted by the end of the sprint, about 1530 seconds later. However,the usefulness of the ATP-CP system lies in the rapid availability of energy rather than quantity. This is extremely important with respect to the kinds of physical activities that humans are capable of performing.[5]Anaerobic system[edit]This system is known as anaerobic glycolysis. Glycolysis refers to the breakdown of sugar. In this system, the breakdown of sugar supplies the necessary energy from which ATP is manufactured. When sugar is metabolized anaerobically, it is only partially broken down and one of the by-products is lactic acid. This process creates enough energy to couple with the energy requirements to resynthesize ATP.When H+ ions accumulate in the muscles causing the blood pH level to reach very low levels, temporary muscular fatigue results. Another limitation of the lactic acid system that relates to its anaerobic quality is that only a few moles of ATP can be resynthesized from the breakdown of sugar as compared to the yield possible when oxygen is present. This system cannot be relied on for extended periods of time.The lactic acid system, like the ATP-CP system, is extremely important, primarily because it also provides a rapid supply of ATP energy. For example, exercises that are performed at maximum rates for between 1 and 3 minutes depend heavily upon the lactic acid system for ATP energy. In activities such as running 1500 meters or a mile, the lactic acid system is used predominately for the kick at the end of a race.[6]Aerobic system[edit] TheKrebs cycle Oxidative phosphorylationGlycolysis The first stage is known as glycolysis, which produces 2 ATP molecules, 2 reduced molecules of NAD (NADH), and 2 pyruvate molecules which move on to the next stage the Krebs cycle. Glycolysis takes place in the cytoplasm of normal body cells, or the sarcoplasm of muscle cells.The Krebs cycle This is the second stage, and the products of this stage of the aerobic system are a net production of one ATP, onecarbon dioxidemolecule, three reduced NAD molecules, one reduced FAD molecule (The molecules of NAD and FAD mentioned here are electron carriers, and if they are said to be reduced, this means that they have had a H+ ion added to them). The things produced here are for each turn of the Krebs cycle. The Krebs cycle turns twice for each molecule of glucose that passes through the aerobic system as twopyruvatemolecules enter the Krebs cycle. In order for the Pyruvate molecules to enter the Krebs cycle they must be converted to Acetyl Coenzyme A. During this link reaction, for each molecule of pyruvate that gets converted to Acetyl Coenzyme A, an NAD is also reduced. This stage of the aerobic system takes place in the matrix of the cells' mitochondria.Oxidative phosphorylation This is the last stage of the aerobic system and produces the largest yield of ATP out of all the stages a total of 34 ATP molecules. It is called oxidativephosphorylationbecause oxygen is the final acceptor of theelectronsandhydrogen ionsthat leave this stage of aerobic respiration (hence oxidative) and ADP gets phosphorylated (an extra phosphate gets added) to form ATP (hence phosphorylation).This stage of the aerobic system occurs on the cristae (infoldings on the membrane of the mitochondria). The NADH+ from glycolysis and the Krebs cycle, and the FADH+ from the Krebs cycle pass down electron carriers which are at decreasing energy levels, in which energy is released to reform ATP. Each NADH+ that passes down this electron transport chain provides enough energy for 3 molecules of ATP, and each molecule of FADH+ provides enough energy for 2 molecules of ATP. If you do your math this means that 10 total NADH+ molecules allow the rejuvenation of 30 ATP, and 2 FADH+ molecules allow for 4 ATP molecules to be rejuvenated (The total being 34 from oxidative phosphorylation, plus the 4 from the previous 2 stages meaning a total of 38 ATP being produced during the aerobic system). The NADH+ and FADH+ get oxidized to allow the NAD and FAD to return to be used in the aerobic system again, and electrons and hydrogen ions are accepted by oxygen to produce water, a harmless by-product.Preliminary Energy Audit

The Preliminary Energy Audit focuses on the major energy suppliers and demands usually accounting for approximately 70% of total energy. It is essentially a preliminary data gathering and analysis effort. It uses only available data and is completed with limited diagnostic instruments. The PEA is conducted in a very short time frame i.e. 1-3 days during which the energy auditor relies on his experience together with all the relevant written, oral visual information that can lead to a quick diagnosis of the plant energy situation. The PEA focuses on the identification of obvious sources of energy wastage's. The typical out put of a PEA is a set of recommendations and immediate low cost action that can be taken up by the department head.

Detailed Energy Audit

The detailed audit goes beyond quantitative estimates of costs and savings. It includes engineering recommendations and well-defined project, giving due priorities. Approximately 95% of all energy is accounted for during the detailed audit. The detailed energy audit is conducted after the preliminary energy audit. Sophisticated instrumentation including flow meter, flue gas analyzer and scanner are use of compute energy efficiency.

Scope of work for detailed Energy Audit

Review of Electricity Bills, Contract Demand and Power Factor:For the last one year, in which possibility will be explored for further reduction of contract demand and improvement of power factor Electrical System Network :Which would include detailed study of all the Transformer operations of various Ratings / Capacities, their operational pattern, Loading, No Load Losses, Power Factor Measurement on the Main Power Distribution Boards and scope for improvement if any. The study would also cover possible improvements in energy metering systems for better control and monitoring. Study of Motors and Pumps Loading :Study of motors (above 10 kW) in terms of measurement of voltage (V), Current (I), Power (kW) and power factor and thereby suggesting measures for energy saving like reduction in size of motors or installation of energy saving device in the existing motors. Study of Pumps and their flow, thereby suggesting measures for energy saving like reduction in size of Motors and Pumps or installation of energy saving device in the existing motors / optimization of pumps. Study of Air conditioning plant :w.r.t measurement of Specific Energy consumption i.e kW/TR of refrigeration, study of Refrigerant Compressors, Chilling Units, etc. Further, various measures would be suggested to improve its performance. Cooling Tower:This would include detailed study of the operational performance of the cooling towers through measurements of temperature differential, air/water flow rate, to enable evaluate specific performance parameters like approach, effectiveness etc. Performance Evaluation of Boilers:This includes detailed study of boiler efficiency, Thermal insulation survey and flue gas analysis. Performance Evaluation of Turbines:This includes detailed study of Turbine efficiency, Waste heat recovery. Performance Evaluation of Air Compressor:This includes detailed study of Air compressor system for finding its performance and specific energy consumption Evaluation of Condenser performance:This includes detailed study of condenser performance and opportunities for waste heat recovery Performance Evaluation of Burners / Furnace :This includes detailed study on performance of Furnace / Burner, thermal insulation survey for finding its efficiency Windows / Split Air Conditioners:Performance shall be evaluated as regards, their input power vis-a-vis TR capacity and performance will be compared to improve to the best in the category Illumination:Study of the illumination system, LUX level in various areas, area lighting etc. and suggest measures for improvements and energy conservation opportunity wherever feasible. DG Set:Study the operations of DG sets to evaluate their average cost of Power Generation, Specific Energy Generation and subsequently identify areas wherein energy savings could be achieved after analysing the operational practices etc. of the DG sets.The entire recommendations would be backed up with techno-economic calculations including the estimated investments required for implementation of the suggested measures and simple payback period. Measurement would be made using appropriate in

Energy conservation''means to reduce the quantity ofenergythat is used for different purposes. This practice may result in increase offinancial capital,environmentalvalue, national and personal security, and human comfort.Individuals and organizations that are directconsumersof energy may want to conserve energy in order to reduce energy costs and promote economic, political and environmentalsustainability. Industrial and commercial users may want to increase efficiency and thus maximize profit.On a larger scale, energy conservation is an important element ofenergy policy. In general, energy conservation reduces the energy consumption and energy demand per capita. This reduces the rise in energy costs, and can reduce the need for new power plants, and energy imports. The reduced energy demand can provide more flexibility in choosing the most preferred methods of energy production.By reducingemissions, energy conservation is an important method to preventclimate change. Energy conservation makes it easier to replacenon-renewable resourceswithrenewable energy. Energy conservation is often the most economical solution to energy shortages.Natural resource and energy conservation is achieved by managing materials more efficiently. Choose from the efforts and resources below to learn how to conserve resources at home and at work. Reduce, Reuse, Recycle: Learn ways to reduce household and industrial waste. Three primary strategies for effectively managing materials and waste are reduce, reuse, and recycle. Reduce waste by making smart decisions when purchasing products, including the consideration of product packaging. Reuse containers and products. Recycle materials ranging from paper to food scraps, yard trimmings, and electronics. Purchase products manufactured with recycled content.

Reducing Food Waste: Information for businesses and organizations on reducing food waste.

Composting for Facilities: Learn more about industrial composting.

Sustainable Materials Management (SMM): SMM is a systemic approach to using and reusing materials more productively over their entire lifecycles. Learn what EPA is doing to advance SMM and how to become involved.

Conservation Tools: Tools and programs that promote waste reduction and recycling. Read guidelines for businesses regarding purchasing recycled materials, controlling solid waste management costs, and streamlining and improving operations. Learn about evaluating effectiveness of recycling in the community.

Common Wastes and Materials: Common materials from the municipal, commercial, and industrial waste streams that have good opportunities for recycling and reuse.Building Evaluation ToolsVERDE.Building Evaluation and Environmental Certification MethodIn the past few years, the concepts of sustainable or green building have evolved, incorporating new notions and concepts.Due to several factors like climate change or a shortage in natural resources, we are witnessing an increase in the environmental awareness of both citizens and designers. This has lead us to look beyond traditional construction methods, taking other problems into consideration, such as energy saving or material selection, following ecological criteria.Nowadays, some ecological and energetic saving measures are generally taken by designers, depending on the context and location of the building, its characteristics and their own knowledge on the subject. Nevertheless, it is more complex to assess whether these measures imply that the building is truly innovative, eco-friendly and sustainable, making it worthy of obtaining an Environmental Certification. At any rate, it becomes clear that introducing one single element is not enough to confirm that a building is actually sustainable.Considering these arguments the Technical Committee atGBCehas put together criteria and established rules to define the requirements and limits a building must meet to be qualified as sustainable, and therefore obtain aGBC Espaa Certificate-VERDE.The evaluation system is based on a feature evaluating method, in accordance with the CTE (Cdigo Tcnico de la Edificacin, Technical Building Code) and European Guidelines. At its core are bio-architecture principles: the buildings respect for the environment, whether it is compatible with its surroundings and the high comfort and quality of life levels required for the users.Evaluation CriteriaThe evaluation criteria are grouped into subjects, as follows:A.Site Selection, Project Planning and Development Recycling strategies for the project or community Autochthonous plants Atmospheric light pollution B. Energy and atmosphere Use of non-renewable energy resources in the manufacture of building materials Use of non-renewable energy resources to transport the building materials Reduction of operating energy Reduction of peak electric loads Provision of on-site renewable energy systems Strategies to reduce the emission of photo-oxidants and NOx substances Strategies to reduce substances aggressive to the stratospheric ozone layer, from building materials and HVAC systems C.Natural Resources Design measures to reduce use of potable water for occupancy needs Rainwater storagefor later reuse Design features for a split grey/potable water system for later reuse Natural impact and hazardous waste generated by building materials used Demolition, dismantling, reusage and recycling strategies Natural impact and hazardous waste generated in the construction processD. Indoor environmental Quality Removal, before occupancy, of pollutants emitted by new interior finishing materials Indoor air CO2 concentration Air movement in mechanically ventilated occupancies Effectiveness of ventilation in naturally ventilated occupancies Air temperature and relative humidity in mechanically cooled occupancies Air temperature in naturally ventilated occupancies Day lighting in primary occupancy areas Glare in non-residential occupancies Illumination levels and quality of lighting in non-residential occupancy design Noise attenuation through the exterior envelope Transmission of facility equipment noise to primary occupancies Noise attenuation between primary occupancy areas E. Service Quality Spatial efficiency Volumetric efficiency Provision and operation of an effective facility management control system Capability for partial operation of facility technical systems Degree of local control of lighting systems in non-residential occupancies Degree of personal control of technical systems by occupants Ability to modify facility technical systems Strategies to maximize adaptability of structural type and payout for the future functional requirements Strategies to minimize constraints imposed by floor-to-floor heights on future functional requirements Strategies to minimize constraints imposed by building envelope and technical systems for future functional requirements Adaptability to future changes in type of energy supply Development and implementation of a maintenance management plan On-going monitoring and verification of building performance (energy and water) F.Social and Economic Aspects Access for physically handicapped persons Access to direct sunlight from living areas of dwelling units Access to private open space from dwelling units Visual privacy from the exterior in principal areas of dwelling units Access to outside views from work areas Minimization of construction cost Minimization of operating and maintenance cost Affordability of residential rental or cost levelsIMPACTSIMPACTINDICATOR

Climate Changekg CO2eq per year

Increase in UV radiation at ground levelkg CFC11 eq year

Soil fertility losskg SO2eq per year

Aquatic life losskg PO4eq per year

Health and cancer riskkg C2H4eq per year

Changes in local biodiversity%

Exhaustion of non-reweable energy resources, primary energyMJ

Exhaustion of non-reneweable energy resources, other than primary energykg material

Exhaustion of potable waterm3

Land usem2

Soil exhaustion due to non-hazardous material disposalm3

Hazardous waste storage or disposalkg

Radioactive waste storage or disposalkg

Health, well-being and productivity of users%

Financial risk or benefit for investors Life cycle cost/m2

Criteria and Impact QuantificationA benchmark, or reference score, is assigned to each criterion. They are set based on the revision of the laws or regulations in force, the performance analysis of the surrounding buildings.The score goes from 0 to 5, in the following order: 0reference value level that implies compliance with current legislation or common practice 3 value level implying good practice 5 value level implying the best possible practice with an acceptable costThe final score will be obtained by comparing and adjusting the impact reduction in relation to the reference building.The load assigned to each impact is related to the significance of such impact on a worldwide scale, at global level, and to the local environment existing situation, at regional level.At present, the assigned load for the several impact categories follows indications from theOSE Report on Sustainability in Spain 2007and theMMA Report on the Environmental Profile in Spain 2007.New Building Design & Construction: Energy-Efficient from the StartFor new construction projects, EPA: Goes beyond the applicable codes and regulations (e.g., 10 CFR Part 435 Subpart A) to pursue DOE design initiatives encouraged by the Energy Policy Act and EO 12902. Such initiatives include passive energy design strategies, use of waste energy and reclaimable resources, and the use of solar and renewable energy Maintaines among staff, site managers, site designers and contractors a high level of awareness of technology developments, especially renewable energy technologies, and a commitment to use them whenever possible, and where cost effective Ensures that all new environmental control systems installed are highly automated, using a comprehensive monitoring and control strategy designed to continuously monitor the systems performance for delivery of services at the expected energy efficiency and pollution prevention levels. The Program of Requests for new laboratories planned for Las Vegas, NV; Kansas City, KS; Edison, NJ; and Lexington, MA; are being amended to include requirements for renewable technology applications.Green Buildings ProgramVast opportunities for implementing regulatory and executive order procurement requirements exist in building construction, renovation, and maintenance. For several years, EPA has been implementing Green Building strategies in a variety of ways, which are expanding with each construction and renovation project. To promote a healthful and productive working environment, the Green Buildings program incorporates principles of energy and resource efficiency, applies waste reduction and pollution prevention practices, ensures unpolluted indoor air, and uses natural light as a light and heat source whenever possible. The Green Buildings Vision and Policy statement, onpage 22, serves as a guide for EPA and as a model for other agencies. It represents a holistic, systems approach to sustainable building design, renovation, and maintenance.There are many examples of Green Building practices that are incorporated in numerous solicitation for offers (SFOs) for construction and/or renovation activities at EPA facilities. For instance, SFOs have specified the collection of recyclable waste materials, the recycling of construction and renovation debris, and the reuse of existing building material. Also, SFOs specify the use of environmentally preferable building products and materials, promote low VOC-content adhesives, and restrict the use of products made from endangered or restricted wood.Several upcoming and recent EPA facility construction projects demonstrate technologies and concepts that integrate a systems approach to Green Buildings procurement using many of the practices previously described. These facilities include the New Headquarters Buildings (Washington, DC), the New Consolidated RTP Facility (Research Triangle Park, NC), the Region IV Science and Ecosystems Support Laboratory (Athens, GA), Region IV Office (Atlanta, GA), Region III Office (Philadelphia, PA), Region VII Central Regional Laboratory (Kansas City, KS), National Vehicle and Fuel Emissions Laboratory (Ann Arbor, MI), and the Fort Meade Environmental Science Center (Fort Meade, MD). The following EPA facilities provide examples of the variety of energy conservation and pollution prevention opportunities which were addressed through the Green Buildings program.Athens, GeorgiaA variety of pollution prevention opportunities were considered and incorporated into the design and construction of the new Region IV laboratory in Athens, Georgia. In incorporating Green Building concepts, OA was able to minimize off-gas environmental contaminants in materials andGREEN BUILDINGS VISION AND POLICY STATEMENTIn order to maintain leadership in environmental protection, EPA must lead by example. Through sustainable design and construction of EPA facilities we will model responsible environmental behavior and help create the framework within which the building industry as a whole can shift towards practices which will promote "Green Buildings".Green Buildings are structures that incorporate the principles of sustainable design -- design in which the impact of a building on the environment will be minimal over the lifetime of that building. Green Buildings incorporate principles of energy and resource efficiency, practical applications of waste reduction and pollution prevention, good indoor air quality and natural light to promote occupant health and productivity, and transportation efficiency in design and construction, during use and reuse.Agency facilities, both new and existing, should serve as models for a healthy workplace with minimal environmental impacts. To achieve this goal, EPA will utilize both innovative, state-of-the-art technologies and a holistic approach to design, construction, renovation, and use. EPA will work with the private sector to identify opportunities for innovation and help create markets for both products and design concepts. Important considerations in the design, construction and use of EPA-owned and -leased facilities include the following: Site planning that utilizes resources naturally occurring on the site such as solar and wind energy, natural shading, native plant materials, topography and drainage Location and programs to optimize use of existing infrastructure and transportation options, including the use of alternative work modes such as telecommuting and teleconferencing Use of recycled content and environmentally preferable construction materials and furnishings, consistent with EPA Procurement Guidelines Minimization of energy and materials waste throughout the buildings life cycle, from design through demolition or reuse Design of the building envelope for energy efficiency Use of materials and design strategies to achieve optimal indoor environmental quality, particularly including light and air, to maximize health and productivity Operation systems and practices which support an integrated waste management system Recycling of building materials at demolition Management of water as a limited resource in site design, building construction and building operations Utilization of solar and other renewable technologies, where appropriateEvaluation of trade-offs will be an important component of the design of Green Buildings. Where the goals of a Green Building are contradictory (for example, increased ventilation vs. increased energy efficiency), the trade-offs will have to be evaluated in a holistic framework to achieve long-term benefits for the environment. Also, the physical considerations must be balanced with other policy objectives such as environmental justice, particularly with regards to site location. We anticipate that there may not be always be single answers to recurring building issues, but we will adopt a consistent approach to evaluating all buildings for sustainable design considerations.products (e.g., adhesives, varnishes, carpets, paints), use CFC-free insulations and refrigerants, and avoid materials in limited supply or not from sustainable sources. OA was able to use recycled content products (e.g., insulation, wall board, and fly-ash concrete), maximize shading through liberal use of trees and shrubs, and include centralized recycling stations. A variety of conservation opportunities were implemented, such as improved efficiency of refrigeration equipment, a VAV HVAC system, split-task ambient lighting system, low-flow plumbing fixtures, and trickle irrigation systems for exterior landscaping.New EPA Headquarters, Washington, DCEPA has completed construction of a consolidated headquarters facility in downtown Washington, DC. The Agency occupies a portion of the Ronald Reagan Federal Building and the adjacent Customs/Connecting Wing/Interstate Commerce Commission and Ariel Rios Buildings. EPAs newHeadquarters operates with many energy-saving features, described below. The variety of solutions implemented by EPA highlights the dynamic diversity of available responses to energy conservation needs.HVAC System EPA required that perimeter walls be adequately insulated and all windows be recaulked and reglazed to virtually "seal" the building and reduce demand on the HVAC system by preventing the loss of cool air during the cooling season and warm air during the heating season. Space-adjustable thermostats control VAV fans to automatically adjust the amount and temperature of the air to meet the requirements of the office or space. Upgraded HVAC system eliminates use of CFCs and is designed to maximize energy efficiency.Lighting Occupancy sensors have been installed in workstations to turn off task and under-cabinet lights when the space is unoccupied for 15 minutes. Daylighting controls and floor-wide occupancy sensors turn off lights when they are not needed. Where possible, partitions have been kept away from external windows to allow penetration of daylight into work spaces. Lighting system is up to 90 percent efficient; EPA expects upgrades will provide savings upwards of 40 percent over typical commercial systems. Work space colors and lighting fixtures are designed to reduce glare.Fort Meade Environmental Science Center, MDEnvironmentally sound materials and processes will be incorporated into the various phases of design at the new facility in Fort Meade, MD. For example, materials for the interior finishes will be selected to minimize chemical off-gasing. Lighter colored finishes will be used in order to maximize the lighting reflectivity. In addition, no mercury, asbestos, or halon will be used within the facility, and no lead is to be used in the water piping connections.Examples of Green Building practices incorporated into the site design phase include stipulating that existing trees will be transported on-site where possible and that, to reduce the need for fertilization, new planting will include native species and grasses. Also, the existing tree stands will be preserved to the extent possible. Another example in this area is the use of recycled asphalt for wearing surfaces for parking and roadway areas.The architectural/structural design phase also provides for many practices that use environmentally benign materials and practices. For example, it is specified that building materials should include recyclable materials where possible, such as within the facilitys insulation and in concrete. In addition, wall bases and selected flooring areas will contain rubber with reclaimed material. Carpet and ceiling tile that are to be used within the facility have been specified to allow these materials to be recycled in the future. Also, a recycling center will be provided for waste materials.Research Triangle Park (RTP),NCThe new 635,000 square-foot consolidated campus at RTP will house about 2,000 EPA staff and contractors in the Agencys largest laboratory and office complex. Energy efficiency has been stressed in every aspect of the design of this new facility, which is now under design and set for completion by early 2001. For example, an integrated systems approach has maximized daylighting while keeping heat gain to a minimum. Although the orientation of the building along the steep slope of the site yields a large amount of southwestern exposure, large forests of tall pines and hardwoods have been carefully preserved to provide the building with much-needed shading. Light-colored pre-cast concrete and roofing material will help reflect radiant heat, and the articulation of the building facade will help to shade the windows from excessive mid-day sun. Insulated, low-E glass will further deflect heat gain while maximizing the daylight benefit of the abundant windows. Motion sensors and daylight dimmers will be combined with high-efficiency electronic fluorescent fixtures which comply with EPAs Green Lights program.Variable speed drives and high-efficiency motors and pumps are used extensively throughout the facility. VAV units and outside air economizers in the office wings keep the energy demand to a minimum. A direct digital control building automation system will tie all heating, cooling and lighting into an integrated system which will minimize energy use throughout the complex.Since laboratories are particularly energy-intensive, special care was given to the custom-designed chemical fume hoods. Each hood will have a specially designed sash which will cut the air demand by 20% in full operation. When the hood is lowered and the researcher turns off the light as he or she leaves the laboratory, air flow is cut dramaticallyyielding a 70% total reduction from the energy demand of a standard fume hood. This energy savings will be realized with no compromise in worker safety protections.

MINIMIZATION OF PETROLEUM USERefer to Appendix C for information on EPAs vehicle fuel consumption.

CONCLUSIONEPA has taken many positive steps to conserve energy over the last year. Since EPA met its 10 percent energy reduction goal in 1995, the Agency has moved beyond the traditional conservation approaches of lighting retrofits and building upgrades to a more aggressive, all-encompassing program. EPAs partnerships with other government agencies and the private sector, use of innovative technolo