PowerPoint Presentation

1UNIT-IIUNIT-IWELCOME TO THIS COURSE ENERGY EFFICIENCY IN ELECTRICAL UTILITIESUNIT-IIIELECTRICAL SYSTEMELECTRIC MOTORSCOMPRESSED AIR SYSTEMHVAC AND REFRIGERATION SYSTEMFANS AND BLOWERSPUMPS AND PUMPING SYSTEMCOOLING TOWERDG SET SYSTEMSENERGY EFFICIENT TECHNOLOGIES IN ELECTRICAL SYSTEMS

ENERGY EFFICIENCY IN ELECTRICAL UTILITIES

UNIT I2CHAPTER I

ELECTRICAL SYSTEM

3IntroductionElectricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. Electric Power Supply System is an aggregate of equipment used to transmit and distribute electricity from sources to consumers. ClassificationElectrical Systems may be classified by:type of current (direct and alternating)plant location (overhead and cable)layout (circular and radial)normal operating mode (open and closed)

UNIT IELECTRICAL SYSTEM44Generation, Transmission and Distribution of ElectricityElectricity is generated in a number of ways, the most prominent of all are thermal power plants, hydroelectric power plants, nuclear power plants, etc. There are other ways of producing electricity which are called Non-Conventional Energy sources; which include windmill, solar systems, tidal energy etc.The term transmission is used for the process of transporting electricity at a very high voltage and the transmission is in bulk amount. Transmission is a link between Generation and Distribution.Distribution of electricity denotes sending electricity from substations where it is transmitted and received followed by its distribution to various points of utilisation.

UNIT IELECTRICAL SYSTEM5

Important EquipmentUNIT IELECTRICAL SYSTEM6Electrical Load Management and Maximum Demand ControlIn the utilisation of electrical energy, there are three fundamental parameters which one has to understand. They are:Load FactorDiversity FactorUtilisation Factor

Maximum DemandMaximum Demand is measured during a prefixed time duration of either 15 minutes or 30 minutes and then multiplied by either four or two respectively to give kVAH per hour i.e. KVA. Thus, at the end of each time cycle, the timer is reset and fresh measurement starts.

Contracted Maximum Demand (CMD)Contracted Maximum Demand (CMD) is the demand mutually agreed between the supply company and the consumer by way of a signed contract.UNIT IELECTRICAL SYSTEM7Connected LoadConnected load is the sum of the nameplate ratings of all the equipment utilising electricity inside the consumer installation.

Average load is energy consumption recorded divided by the operating hours of the plant.Load Factor = (Average Load)/ (Maximum Demand) always less than 1. Diversity Factor = (Connected Load)/ (Maximum Demand) always more than 1. Utilisation Factor=(Average Load)/(Connected Load) always less than 1. Utilisation Factor = (Load Factor) / (Diversity Factor)

Power FactorPower Factor is a ratio of kW to KVA which is always less than or equal to unity. This is represented by a famous triangular relation.UNIT IELECTRICAL SYSTEM8Leading and Lagging Power Factor

Position of Power Factor Correction CapacitorsThe ideal location for capacitors is to provide them as close to the point of utilisation as possible. But there are certain practical difficulties:Introduction of capacitors demands a cutting out device which will disconnect them from the live circuit as soon as the main equipment is switched off. If not done, this may result in either the power factor going to the leading side but less than unity again. Moreover it may also result in voltage surges which may damage the installation.Hence installing capacitors for each individual equipment becomes expensive and may work out to be uneconomical.UNIT IELECTRICAL SYSTEM9Performance Assessment of Power Factor Correction CapacitorsOnce the power factor capacitors are installed, they continuously need to be monitored for their performance. Their performance depends on voltage as well as ambient temperature. The capacitor before failing totally, gives a number of indications showing the deterioration of their performance. This can be monitored by recording the daily reading or hourly reading of the consumption and power factor by the user. However specialised testing can be done by the manufacturer to know the exact reason for the failure.TransformerThe transformer is one of the most widely used electrical equipment. The main function of the transformer is to either increase voltage or to reduce voltage.

UNIT IELECTRICAL SYSTEM10Rating of the TransformerRating of the transformer is calculated based on the connected load and applying the diversity factor on the connected load, applicable to the particular industry and arriving at the kVA rating of the Transformer. The diversity factor is defined as the ratio of overall maximum demand of the plant to the sum of individual maximum demand of various equipment.

Location of the TransformerLocation of the transformer is very important as far as distribution losses are concerned. A transformer receives HT voltage from the grid and steps it down to the required voltage. Transformers should be placed close to the load centre, considering other features like optimisation needs for centralised control, operational flexibility, etc. This brings down distribution losses in cables.

Losses and Efficiency of a TransformerThe efficiency varies anywhere between 96 to 99 percent. The efficiency of transformers not only depends on the design, but also, on the effective operating load.Transformer losses consist of two parts:No-load lossLoad lossUNIT IELECTRICAL SYSTEM11Control Used for Voltage FluctuationThe control of voltage in a transformer is important due to frequent changes in the supply voltage level. Voltage regulation in transformers is done by altering the voltage transformation ratio with the help of tapping.

The Parallel Operation of TransformersWhenever two transformers are operating in parallel, both should be technically identical in all aspects and more importantly should have the same impedance level. This minimises the circulating current between transformers.Where the load is fluctuating in nature, it is preferable to have more than one transformer running in parallel, so that the load can be optimised by sharing it between transformers. The transformers can be operated close to the maximum efficiency range by this operation.

UNIT IELECTRICAL SYSTEM12CHAPTER II

ELECTRIC MOTORS

13IntroductionMotors convert electrical energy into mechanical energy by the interaction between the magnetic fields set up in the stator and rotor windings. Electric motors are undoubtedly the largest prime movers used. Industrial electric motors can be broadly classified as:induction motorsdirect current motorssynchronous motors

All motor types have the same four operating components which are:stator (stationary windings)rotor (rotating windings)bearingsframe (enclosure)

Types of MotorsThere are two main types of motors:DC MotorsAC Motors

UNIT IELECTRIC MOTORS14Industrial Classification of MotorsIndustrial electric motors are generally classified as:direct current motors (DC motors)synchronous motors (AC motors)induction motors (induced magnetic field)

UNIT IELECTRIC MOTORS15Direct Current Motors (DC Motors)DC motors have a stationary field winding housed in a stator and rotating armature called rotor. The rotor winding rotate in front of alternating rotor poles, north and south poles. This tries to reverse the current in the winding. To overcome this problem, a commutator and brush arrangement is provided.

Depending on the field and armature connections, the motors are classified into different categories:Separately Excited Motor Self excited motor

Advantages of DC MotorsThe main advantage of DC motors is speed control, which does not affect the quality of power supply. It can be controlled by adjusting:the armature voltage increasing the armature voltage will increase the speedthe field current reducing the field current will increase the speed

UNIT IELECTRIC MOTORS16

Disadvantages of DC MotorsThe disadvantages of these motors are mainly their initial cost and maintenance of brushes and the commutator. Moreover they require a separate cooling arrangement.UNIT IELECTRIC MOTORS17Synchronous/AC MotorsIn these motors, the stator is given a three phase A.C. supply. The Rotor is given a DC supply through brushes and slip rings. The stator produces a rotating magnetic field and the rotor field is locked into the synchronism of the rotating magnetic field.

The main advantage of this motor was that by controlling the rotor excitation, the power factor of the motor could be controlled and the motor could be made to operate with a leading power factor.

The evident disadvantages of this motor were:the slip ring and brush maintenance and provision for the prime mover..the initial cost of these motors also was high. But these days nobody opts to use these motors.

UNIT IELECTRIC MOTORS18Induction MotorsInduction motors are the most commonly used prime mover for various equipment in industrial applications. In induction motors, the induced magnetic field of the stator winding induces a current in the rotor. This induced rotor current produces a second magnetic field, which tries to oppose the stator magnetic field, and this causes the rotor to rotate.

There are two types of Induction Motors:The slip ring induction motor: In this motor, the stator is given a three phase A.C. supply. The rotor is shorted outside through slip rings and brushes. The squirrel cage induction motor: A squirrel cage rotor is the rotating part used in the most common form of AC induction motor. An electric motor with a squirrel cage rotor is termed a squirrel cage motor. UNIT IELECTRIC MOTORS19The Power FactorThe power factor of the motor is given as: Power factor = Cos = kW/kVA

Name Plate Parameters of a Motor

UNIT IELECTRIC MOTORS20Motor LoadBecause the efficiency of a motor is difficult to assess under normal operating conditions, the motor load can be measured as an indicator of the motors efficiency. As loading increases, the power factor and the motor efficiency increase to an optimum value at around full load.Motor Efficiency and its LossesIf power output is measured in Watt (W), efficiency can be expressed as:m = Pout / PinWherem = motor efficiency..Pout = shaft power out (Watt, W)..Pin = electric power in to the motor (Watt, W)

The losses can be generally classified into two categories:Fixed losses are those which occur in the motor irrespective of the quantum of load. These are also called no load losses.Variable losses are those which are dependent on the quantum of the load. UNIT IELECTRIC MOTORS21Factors Affecting Motor PerformanceMotor performance depends on: Partial load operationCorrect Application of the drive to suit the applicationApplication of rated voltage and frequency

Rewinding and Motor Replacement IssuesMany a times during the maintenance of motors, one has to encounter rewinding of motors. The rewound motors seldom give the same performance as original motors. Due to this every time a motor is rewound, its useful life is affected and the next rewinding is advanced. Hence motors rewound must be checked thoroughly before loading them to the original loading pattern.Energy Saving Opportunities with Energy Efficient Motors

UNIT IELECTRIC MOTORS22CHAPTER III

COMPRESSED AIR SYSTEM

23IntroductionAir compressors account for significant amount of electricity used in Indian industries. Compressed air is an essential but costly utility and its use must be made wisely. Compressed air is generated from compressors which are largely driven by electricity. If efficiency is calculated, only 10% useful energy reaches the end point through compressed air. Thus there is a vast scope for energy saving through proper understanding of the functions of this utility and avoiding its wastage.

Classification of CompressorsCompressors are broadly classified as :- Positive Displacement CompressorsDynamic (Centrifugal) Compressors

UNIT ICOMPRESSED AIR SYSTEM24Positive displacement compressorsThe compressors which increase the pressure of the gas by reducing the volume are called positive displacement compressors. These compressors are further classified into:reciprocating compressorsrotary compressors

Dynamic compressorsDynamic compressors increase the air velocity, which is then converted to increased pressure at the outlet. They are basically centrifugal compressors and are further divided into:radial typeaxial flow type

Compressor CapacityCapacity of a compressor is the full rated volume of flow of gas compressed and delivered at conditions of total temperature, total pressure, and composition existing at the compressor inlet. UNIT ICOMPRESSED AIR SYSTEM25Compressed Air System ComponentsUNIT ICOMPRESSED AIR SYSTEM26Prerequisites for Efficient Operation of CompressorThere are a number of issues to be considered right at the stage of project planning and also during operation. Few of them are listed below:Compressor LocationCool Air IntakeDust free air intakeDry AirAppropriate AltitudeOptimum pressure settingsFactors Affecting Performance and EfficiencyFollowing are a few factors affecting the performance and efficiency of compressors:Lack of general awarenessWrong application and extensions of existing pipelinesWrong choice of system (distributive/ centralised )

UNIT ICOMPRESSED AIR SYSTEM27

ENERGY EFFICIENCY IN ELECTRICAL UTILITIES

UNIT II28

29CHAPTER I

HVAC AND REFRIGERATION SYSTEMIntroductionThe Heating, Ventilation, and Air Conditioning (HVAC) and refrigeration systems transfer heat energy from one environment to the other. HVAC includes the bi-directional flow of heat, in the sense that when earth's atmospheric temperature is too low, then the requirements of a closed atmosphere are to be maintained. Heat is injected into the closed atmosphere.Refrigeration on the other hand, has a unidirectional flow of heat. It always extracts heat from the closed atmosphere with the help of a low boiling point refrigerant and dispels it into the open atmosphere of the earth.

UNIT IIHVAC AND REFRIGERATION SYSTEM30Air-Conditioning SystemsDepending on applications, there are several options / combinations, which are available for use as given below:Air Conditioning (for comfort / machine)Split air conditioners Fan coil units in a larger systemAir handling units in a larger system

UNIT IIHVAC AND REFRIGERATION SYSTEM31Refrigeration Systems (for processes)Small capacity modular units of direct expansion type similar to domestic refrigerators, small capacity refrigeration units.Centralised chilled water plants with chilled water as a secondary coolant for temperature range over 50C typically. They can also be used for ice bank formation.Brine plants, which use brines as lower temperature, secondary coolant, for typically sub zero temperature applications, which come as modular unit capacities as well as large centralised plant capacities.

UNIT IIHVAC AND REFRIGERATION SYSTEM32Types of Refrigeration SystemsThe two principle types of refrigeration plants found in industry include:Vapour Compression Refrigeration (VCR)Vapour Absorption Refrigeration (VAR)

VCR uses mechanical energy as the driving force for refrigeration, while VAR uses thermal energy as the driving force for refrigeration.

UNIT IIHVAC AND REFRIGERATION SYSTEM33

EvaporatorThe refrigerant (water) evaporates at around 400C under a high vacuum condition of 754mmHg in the evaporator.Chilled water goes through heat exchanger tubes in the evaporator and transfers heat to the evaporated refrigerant.The evaporated refrigerant (vapour) turns into liquid again, while the latent heat from this vaporization process cools the chilled water. The chilled water is then used for cooling purposes.

AbsorberIn order to keep evaporating, the refrigerant vapour must be discharged from the evaporator and refrigerant (water) must be supplied. The refrigerant vapour is absorbed into lithium bromide solution, which is convenient to absorb the refrigerant vapour in the absorber. The heat generated in the absorption process is continuously removed from the system by cooling water. The absorption also maintains the vacuum inside the evaporatorUNIT IIHVAC AND REFRIGERATION SYSTEM3434High Pressure GeneratorAs lithium bromide solution is diluted, the ability to absorb the refrigerant vapour reduces. In order to keep the absorption process going, the diluted lithium bromide solution must be concentrated again.An absorption chiller is provided with a solution concentrating system, called a generator. Heating media such as steam, hot water, gas or oil perform the function of concentrating solutions.The concentrated solution is returned to the absorber to absorb refrigerant vapour again.

CondenserTo complete the refrigeration cycle, and thereby ensuring the refrigeration takes place continuously, the following two functions are required:To concentrate and liquefy the evaporated refrigerant vapour, which is generated in the high pressure generator.To supply the condensed water to the evaporator as refrigerant (water).

UNIT IIHVAC AND REFRIGERATION SYSTEM35Types of Compressors used in Cooling SystemsCentrifugal CompressorsCentrifugal compressors are the most efficient types , when they operate near full load. Their efficiency advantage is the greatest in large sizes and they offer considerable economy of scale, so they dominate the market for large chillers.

Reciprocating CompressorsThe maximum efficiency of reciprocating compressors is lower than that of centrifugal and screw compressors. Efficiency is reduced by the clearance volume (the compressed gas volume that is left at the top of the piston stroke), throttling losses at the intake and discharge valves, abrupt changes in gas flow, and friction.

Screw CompressorsScrew compressors, sometimes called helical rotary compressors, compress the refrigerant by trapping it in the threads of a rotating screw-shaped rotor.

Scroll CompressorsThe gas is compressed between two scroll-shaped vanes. One of the vanes is fixed, and the other moves within it. The moving vane does not rotate, but its centre revolves with respect to the centre of the fixed vane.UNIT IIHVAC AND REFRIGERATION SYSTEM36Selection of a Suitable Refrigeration SystemA clear understanding of the cooling load to be met is the first and most important part of designing/selecting the components of a refrigeration system. Important factors to be considered in quantifying the load are the actual cooling need, heat (cool) leaks, and internal heat sources (from all heat generating equipment). Consideration should also be given to process changes and/or changes in ambient conditions that might affect the load in the future.

UNIT IIHVAC AND REFRIGERATION SYSTEM37Factors Affecting Performance and Energy Efficiency of Refrigeration PlantsThe various factors which affect the performance and energy efficiency of refrigeration plants are as follows:The Design of Process Heat ExchangersMaintenance of Heat Exchanger SurfacesMulti-staging for EfficiencyMatching Capacity to System LoadCapacity Control and Energy Efficiency

Energy Saving OpportunitiesCold InsulationInsulate all cold lines / vessels using economic insulation thickness to minimise heat gains; and to choose appropriate (correct) insulation.Building EnvelopeOptimise air conditioning volumes by measures such as use of false ceiling and segregation of critical areas for air conditioning by air curtains.Building Heat Loads Minimisation

Cold InsulationUNIT IIHVAC AND REFRIGERATION SYSTEM38

39CHAPTER II

FANS AND BLOWERSIntroductionFans and blowers provide air for ventilation and industrial process requirements. Fans generate a pressure to move air (or gases) against a resistance caused by ducts, dampers, or other components in a fan system. The fan rotor receives energy from a rotating shaft and transmits it to the air. Industrial FansIndustrial fans and blowers are machines whose primary function is to provide a large flow of air or gas to various processes of many industries. This is achieved by rotating a number of blades, connected to a hub and shaft and driven by a motor or turbine.

UNIT IIFANS AND BLOWERS40Types of FansFans are divided into two general categories:Centrifugal flowIn centrifugal flow, airflow changes direction twice once when entering and secondly, while leaving (forward curved, backward curved or inclined, radial)

Axial flowIn axial flow, air enters and leaves the fan with no change in direction (propeller, tube axial, vane axial)

Centrifugal FlowAxial FlowUNIT IIFANS AND BLOWERS41Types of BlowersBlowers can achieve much higher pressures than fans, as high as 1.20 kg/cm2. They are also used to produce negative pressures for industrial vacuum systems. Major types of blowers are:Centrifugal BlowersCentrifugal blowers look more like centrifugal pumps compared to fans. In multi-stage blowers, air is accelerated as it passes through each impeller. In a single-stage blower, air does not take many turns, and hence it is more efficient.

Positive-Displacement BlowersPositive-displacement blowers have rotors, which "trap" air and push it through the housing. Positive-displacement blowers provide a constant volume of air even if the system pressure varies.

Centrifugal BlowerPositive-Displacement BlowerUNIT IIFANS AND BLOWERS42System CharacteristicsThe term system resistance is used while referring to the static pressure. The system resistance is the sum of static pressure losses in the system.The system resistance varies with the square of the volume of air flowing through the system. System resistance increases substantially as the volume of air flowing through the system increases; square of air flow. Conversely, resistance decreases as flow decreases.

System CharacteristicsUNIT IIFANS AND BLOWERS43Fan CharacteristicsThe fan curve is a performance curve for the particular fan under a specific set of conditions. The fan curve is a graphical representation of a number of interrelated parameters.Typically, a curve will be developed for a given set of conditions usually including fan volume, system static pressure, fan speed and brake horsepower required to drive the fan under the stated conditions.

UNIT IIFANS AND BLOWERS44Fan LawsThe fans operate under a predictable set of laws concerning speed, power and pressure. A change in speed (rpm) of any fan will predictably change the pressure rise and power necessary to operate it at the new RPM.

Where, Q flow; SP Static Pressure, kW Power; N speed (RPM)UNIT IIFANS AND BLOWERS45Fan Design and Selection CriteriaFollowing are some important points to remember before selecting a particular fan:Precise determination of air-flow and required outlet pressure System pressure requirementGood judgement on magnitudes of the required flow and static pressureFan Performance and EfficiencyForward curved fans have large hub-to-tip ratios compared to backward curved fans and produce lower pressure.Radial fans can be made with different heel-to-tip ratios to produce different pressures.At both design and off-design points, backward-curved fans provide the most stable operation. Centrifugal fans are suitable for low to moderate flow at high pressures, while axial-flow fans are suitable for low to high flows at low pressures.

UNIT IIFANS AND BLOWERS46Flow Control StrategiesVarious ways to achieve a change in flow are:Pulley ChangeDamper ControlsVariable Speed DrivesSeries and Parallel OperationAir flow MeasurementThe components of air flow management are:Static Pressure: It is the potential energy put into the system by the fan. Velocity Pressure: It is the pressure along the line of the flow that results from the air flowing through the duct. Total Pressure: Sum of Static and Velocity pressuresEnergy Saving OpportunitiesFollowing are a few ways to save energy with respect to fan/blower usage:Minimising demand on the fanMinimising excess air level in combustion systems to reduce FD fan and ID fan loadMinimising air in-leaks in the hot flue gas path to reduce the ID fan load, especially in case of kilns, boiler plants, furnaces, etc. In-leaks / out-leaks in air conditioning systems also have a major impact on energy efficiency and fan power consumption and need to be minimised.UNIT IIFANS AND BLOWERS47

48CHAPTER III

PUMPS AND PUMPING SYSTEMIntroductionA pump is a device used to move fluids, such as liquids, gases or slurries. A pump displaces a volume of fluid by physical or mechanical action. Major Groups of PumpsDirect lift pumpsDisplacement pumpsVelocity pumpsBuoyancy pumpsGravity pumpsMain Purpose of PumpsPumps have two main purposes:transfer of liquid from one place to another place circulate liquid around a system

UNIT IIPUMPS AND PUMPING SYSTEM

49Types of PumpsPumps have a variety of sizes for a wide range of applications. They can be classified according to their basic operating principles as:Dynamic pumps: Dynamic pumps are characterised by their mode of operation; a rotating impeller converts kinetic energy into pressure or velocity that is needed to pump the fluid.

Positive-displacement pumps: In these pumps, liquid is taken from one end and positively discharged at the other end for every revolution.

UNIT IIPUMPS AND PUMPING SYSTEM50Centrifugal PumpThe two main parts of the centrifugal pump are:The impeller, which is the only moving part, is attached to a shaft and driven by a motor. Impellers are generally made of bronze, polycarbonate, cast iron, stainless steel as well as other materials.The diffuser (also called volute) houses the impeller and captures and directs the water off the impeller.

WorkingWater enters the centre (eye) of the impeller and exits the impeller with the help of centrifugal force. As water leaves the eye of the impeller, a low-pressure area is created, causing more water to flow into the eye. Velocity is developed as the water flows through the impeller spinning at high speed.UNIT IIPUMPS AND PUMPING SYSTEM51System CharacteristicsIn a pumping system, the objective, in most cases, is either to transfer a liquid from a source to a required destination, e.g. Filling a high level reservoir or to circulate liquid around a system.Pressure is needed to make the liquid flow at the required rate and this must overcome head losses' in the system.

Losses are of two types: Static Head: The static head is simply the difference in the height of the supply and destination reservoirsFriction Head: The friction head (sometimes called dynamic head loss) is the friction loss on the liquid being moved, in pipes, valves and equipment in the system.

UNIT IIPUMPS AND PUMPING SYSTEM52Factors Affecting Pump PerformanceFactors which affect the performance of the pump are:Matching Pump and System Head-flow CharacteristicsEffect of Over Sizing the PumpEnergy Loss in ThrottlingEfficient Pumping System OperationTo understand a pumping system, one must realise that all of its components are interdependent. While examining or designing a pump system, the process demands must be established first and the most energy efficient solution should be introduced. Following points would be helpful:Target the end-use Good water conservation measures Optimise flow requirements

UNIT IIPUMPS AND PUMPING SYSTEM53Flow Control StrategiesDifferent strategies to control flow are:Pump Control by Varying SpeedPumps in Parallel Switched to Meet DemandStop/Start ControlFlow Control ValveBy-pass ControlSteps for Energy Efficiency in Pumping SystemFollowing are a few steps towards achieving energy efficiency in pumps:Ensure availability of basic instruments at pumps like pressure gauges, flow meters. Operate pumps near the best efficiency pointAdapt to wide load variation with variable speed drives or sequenced control of multiple unitsUse booster pumps for small loads requiring higher pressuresIn multiple pump operations, carefully combine the operation of pumps to avoid throttlingReplace old pumps by energy efficient pumps

UNIT IIPUMPS AND PUMPING SYSTEM54

ENERGY EFFICIENCY IN ELECTRICAL UTILITIES

UNIT III55

56CHAPTER I

COOLING TOWERIntroductionThe primary task of a cooling tower is to reject heat into the atmosphere. They represent a relatively inexpensive and dependable means of removing low-grade heat from cooling water.

Cooling Tower TypesCooling towers fall into two main categories:Natural draft: Natural draft towers use very large concrete chimneys to introduce air through the media. These types of towers are used only by utility power stations.

Mechanical draft: Mechanical draft towers utilise large fans to force or suck air through circulated water. The water falls downward over fill surfaces, which helps to increase the contact time between the water and the air - this helps to maximise heat transfer between the two.UNIT IIICOOLING TOWER57Components of a Cooling TowerThe basic components of an evaporative tower are as follows:Frame and casingFillCold water basinDrift eliminatorsAir inletLouversNozzlesFansTower MaterialsFollowing are a few of the materials used in the construction of cooling towers:Galvanized SteelStainless steel ConcreteGlass Fibre

UNIT IIICOOLING TOWER58Performance ParametersRange is the difference between the cooling tower water inlet and outlet temperature.

Approach is the difference between the cooling tower outlet cold water temperature and the ambient wet bulb temperature.

Cooling tower effectiveness (in percentage) is the ratio of range, to the ideal range, i.e., difference between cooling water inlet temperature and ambient wet bulb temperature, or in other words it is = Range / (Range + Approach).

Cooling capacity is the heat rejected in kCal/hour, given as a product of the mass flow rate of water, specific heat and temperature difference.

Evaporation loss is the water quantity evaporated for cooling duty.

UNIT IIICOOLING TOWER59Factors Affecting Cooling Tower PerformanceCapacityRangeWet Bulb TemperatureWet bulb temperature is an important factor in the performance of evaporative water cooling equipment. It is a controlling factor from the aspect of the minimum cold water temperature to which water can be cooled by the evaporative method. Thus, the wet bulb temperature of the air entering the cooling tower determines the operating temperature levels throughout the plant, process, or system.Range, Flow and Heat LoadRange is a direct function of the quantity of water circulated and the heat load. Increasing the range as a result of added heat load does require an increase in the tower size. If the cold water temperature is not changed and the range is increased with a higher hot water temperature, the driving force between the wet bulb temperature of the air entering the tower and the hot water temperature is increased, the higher level heat is economical to dissipate.UNIT IIICOOLING TOWER60Choosing a Cooling TowerThe counter-flow and cross flows are two basic designs of cooling towers based on the fundamentals of heat exchange.Cross-flow cooling towers are provided with splash fill of concrete, wood or perforated PVC. Counter-flow cooling towers are provided with both film fill and splash fill.Counter flow heat exchange is more effective as compared to cross flow or parallel flow heat exchange.Efficient System OperationSystem efficiency can be improved by employing the following methods:Cooling Water TreatmentAvoiding Drift Loss in the Cooling TowersUsing Cooling Tower FansPerformance Assessment of Cooling Towers

UNIT IIICOOLING TOWER61Flow Control StrategiesControl of tower air flow can be done by varying methods: Starting and stopping (On-off) of fansUse of two or three-speed fan motorsUse of automatically adjustable pitch fansUse of variable speed fans.

Energy Saving Opportunities in Cooling TowersFollowing are a few tips on saving energy while operating Cooling Towers:Follow the manufacturer's recommended clearances around cooling towers and relocate or modify structures that interfere with the air intake or exhaust.Optimise cooling tower fan blade angle on a seasonal and/or load basis.Periodically clean plugged cooling tower distribution nozzles.Correct excessive and/or uneven fan blade tip clearance and poor fan balance. UNIT IIICOOLING TOWER62

63CHAPTER II

LIGHTING SYSTEMIntroductionLighting is an essential service in all the industries. Innovation and continuous improvement in the field of lighting, has given rise to tremendous energy saving opportunities in this area.Lighting is an area which provides a major scope to achieve energy efficiency at the design stage, by the incorporation of modern energy efficient lamps, luminaries and gears, apart from good operational practices.Types of LampsIncandescent Lamps Reflector LampsGas Discharge Lamps

UNIT IIILIGHTING SYSTEM64Other Lighting EquipmentLuminaire: The luminaire is a device that distributes, filters or transforms the light emitted from one or more lamps. Luminaires include all the parts necessary for fixing and protecting the lamps, except the lamps themselves.

Ballast: A current limiting device, to counter the negative resistance characteristics of any discharge lamp. In case of fluorescent lamps, it aids the initial voltage build up, required for starting.

Ignitors: These are used for starting high intensity Metal Halide and Sodium vapour lamps.Lighting TerminologyIlluminance: This is the quotient of the luminous flux incident on an element of the surface at a point of surface containing the point, by the area of that element.

Lux (lx): This is the illuminance produced by a luminous flux of one lumen, uniformly distributed over a surface area of one square metre. One lux is equal to one lumen per square metre. UNIT IIILIGHTING SYSTEM6565A step-by-step approach for assessing the energy efficiency of the lighting system is as stated:Inventorise the lighting system elements and transformers in the facility.With the aid of a lux meter, measure and document the lux levels at various plant locations at the working level, as day time lux and night time lux values alongside the number of lamps ON during measurement.With the aid of a portable load analyser, measure and document the voltage, current, power factor and power consumption at various input points.Compare the measured lux values with standard values as reference and identify locations as under lit and over lit areas.Collect and analyse the failure rates of lamps, ballasts and the actual life expectancy levels from past data.Bring about improvements after proper assessment.Methodology of Lighting System Energy Efficiency Study

UNIT IIILIGHTING SYSTEM66Some Good Practices in LightingInstallation of Compact Fluorescent Lamps (CFL's) in Place of Incandescent Lamps

Installation of Metal Halide Lamps in Place of Mercury/Sodium Vapour Lamps

Installation of High Pressure Sodium Vapour (HPSV) Lamps for Applications where Colour Rendering is not Critical

Installation of LED Panel Indicator Lamps in Place of Filament Lamps

Optimum usage of day lighting

UNIT IIILIGHTING SYSTEM67

68CHAPTER III

DG SET SYSTEMSIntroductionThe Diesel engine is a prime mover, which drives an alternator to produce electrical energy. In the diesel engine, air is drawn into the cylinder and is compressed to a high ratio (14:1 to 25:1). During this compression, the air is heated to a temperature of 700 9000C. A metered quantity of diesel fuel is then injected into the cylinder, which ignites spontaneously because of the high temperature. Hence, the diesel engine is also known as the compression ignition (CI) engine.Classification of Diesel Generating SetsDiesel generating (DG) sets can be classified according to cycle types as:Two strokeFour Stroke

A bulk of the CI engines use the four-stroke cycle.

UNIT IIIDG SET SYSTEMS69

The Four Stroke Diesel EngineThe 4 stroke operations in a diesel engine are: Induction strokeCompression strokeIgnition and power stroke Exhaust stroke

UNIT IIIDG SET SYSTEMS70The DG Set as a SystemA diesel generating set should be considered as a system since its successful operation depends on the well-matched performance of the following components:The diesel engine and its accessoriesThe ac generator The control systems and switchgear. The foundation and power house civil works The connected load with its own components like heating, motor drives, lighting etc.It is necessary to select components with the highest efficiency and operate them at their optimum efficiency levels to conserve energy in this system.Selection ConsiderationsTo make a decision on the type of engine which is most suitable for a specific application, several factors need to be considered. The two most important factors are: Power of the engine: The power requirement is determined by the maximum load.Speed of the engine: Speed is measured at the output shaft and given in revolutions per minute (RPM).

UNIT IIIDG SET SYSTEMS71Diesel Generator Captive Power PlantsDiesel engine power plants are most frequently used in small power (captive non-utility) systems. The main reason for their extensive use is the higher efficiency of the diesel engines compared to gas turbines and small steam turbines in the output range considered.Advantages of adopting Diesel Power PlantsLow installation costShort delivery and installation periods Higher efficiency (as high as 43 -45 %)More efficient plant performance under part loadsSuitable for different types of fuels such as low sulphur heavy stock and heavy fuel oil in case of large capacities.Minimum cooling water requirements

UNIT IIIDG SET SYSTEMS72Selection and Installation FactorsSizing of a GensetHigh Speed Engine or Slow/Medium Speed EngineCapacity CombinationsAir Cooling Vs. Water CoolingSafety FeaturesParallel Operation with GridSite Condition Effects on Performance DeratingUnbalanced Load EffectsOperational FactorsLoad Pattern and DG Set CapacitySequencing of LoadsLoad PatternLoad CharacteristicsGenset

UNIT IIIDG SET SYSTEMS73Load CharacteristicsSome of the load characteristics influence the efficient use of a D.G.set. These characteristics are entirely load dependent and cannot be controlled by the D.G.set. Some of these characteristics are:Unbalanced Load: Unbalanced loads on the A.C. generator lead to an unbalanced set of voltages and additional heating in the A.C. generator. Transient Loading: On many occasions, to contain the transient voltage dip arising due to the transient load application, a specially designed generator may have to be selected.Special Loads: Special loads like the rectifier loads, welding loads, furnace loads need an application check.Energy Performance Assessment of DG SetsRoutine energy efficiency assessment of DG sets on the shop floor involves the following typical steps:Ensure reliability of all instruments used for trial.Collect technical literature, characteristics, and specifications of the plant.Conduct a 2 hour trial on the DG set, ensuring a steady load. The fuel oil/diesel analysis is referred to from an oil company data.Analysis of trial data.UNIT IIIDG SET SYSTEMS74Energy Saving Measures for DG SetsFollowing are a few energy saving measures for DG sets:Ensure steady load conditions on the DG set, and provide cold, dust free air at the intake (use of air washers for large sets, in case of dry, hot weather, can be considered).Ensure fuel oil storage, handling and preparation as per manufacturers' guidelines/oil company data.Improve air filtration. Calibrate fuel injection pumps frequently. Ensure compliance with the maintenance checklist.

UNIT IIIDG SET SYSTEMS75

76CHAPTER IV

ENERGY EFFICIENT TECHNOLOGIES IN ELECTRICAL SYSTEMS Maximum Demand ControllersHigh-tension (HT) consumers have to pay a maximum demand charge in addition to the usual charge for the number of units consumed. This charge is usually based on the highest amount of power used during some period (say 30 minutes) during the metering month.The Maximum Demand Controller is a device designed to meet the need of industries conscious of the value of load management. An alarm is sounded when demand approaches a preset value.

UNIT IIIENERGY EFFICIENT TECHNOLOGIES IN ELECTRICAL SYSTEMS 77Automatic Power Factor ControllersVarious types of automatic power factor controls are available with relay / microprocessor logic. Two of the most common controls are:Voltage Control: Voltage alone can be used as a source of intelligence when the switched capacitors are applied at a point where the circuit voltage decreases as circuit load increases.Kilovar Control: Kilovar sensitive controls are used at locations where the voltage level is closely regulated and not available as a control variable.Energy Efficient MotorsEnergy-efficient electric motors reduce energy losses through an improved design, better material, and improved manufacturing techniques. Improvement in motor efficiency is possible from reducing the Watt losses. Following are a few ways to do that:Use of thinner gauge, lower loss core steel reduces eddy current losses. Use of more copper and larger conductors increases cross sectional area of stator windings. Use of low loss fan design reduces losses due to air movement. UNIT IIIENERGY EFFICIENT TECHNOLOGIES IN ELECTRICAL SYSTEMS 78Soft StarterWhen starting, an AC Induction motor develops more torque than is required at full speed. This stress is transferred to the mechanical transmission system resulting in excessive wear and the premature failure of chains, belts, gears, mechanical seals, etc.The soft starter provides a reliable and economical solution to these problems by delivering a controlled release of power to the motor, thereby providing smooth acceleration and deceleration.

Advantages of Soft StartLess mechanical stressImproved power factorLower maximum demandLess mechanical maintenanceUNIT IIIENERGY EFFICIENT TECHNOLOGIES IN ELECTRICAL SYSTEMS 79Speed Control of Induction MotorsThe induction motor is the workhorse of the industry. It is cheap rugged and provides high power to weight ratio. On account of high cost-implications and limitations of the D.C. System, induction motors are preferred for variable speed applications, the speed of which can be varied by changing the supply frequency.The Variable Frequency DriveThe rotational speed of an AC induction motor depends on the number of poles in that stator and the frequency of the applied AC power. Although the number of poles in an induction motor cannot be altered easily, variable speed can be achieved through a variation in the frequency.

Eddy Current DrivesThis method employs an eddy-current clutch to vary the output speed. The clutch consists of a primary member coupled to the shaft of the motor and a freely revolving secondary member coupled to the load shaft.UNIT IIIENERGY EFFICIENT TECHNOLOGIES IN ELECTRICAL SYSTEMS 80Energy Efficient TransformersThe iron loss of any transformer depends on the type of core used in the transformer. The expected reduction in energy loss over conventional (Si Fe core) transformers is roughly around 70%, which is quite significant. By using an amorphous core with unique physical and magnetic properties, these new types of transformers have increased efficiencies even at low loads - 98.5% efficiency at 35% load.Electronic BallastIn an electric circuit, the ballast acts as a stabiliser. Since the fluorescent lamps cannot produce light by direct connection to the power source, they need an ancillary circuit and device to get started and remain illuminated. The auxillary circuit housed in a casing is known as the ballast.

UNIT IIIENERGY EFFICIENT TECHNOLOGIES IN ELECTRICAL SYSTEMS 81Energy Efficient Lighting Controls

Occupancy SensorsOccupancy-linked control can be achieved using infra-red, acoustic, ultrasonic or microwave sensors, which detect either movement or noise in room spaces. These sensors switch lighting on when occupancy is detected, and off again after a set time period, when no occupancy movements are detected.

Timed Based ControlTimed-turn off switches are the least expensive type of automatic lighting control. In some cases, their low cost and ease of installation makes it desirable to use them where more efficient controls would be too expensive.

Daylight Linked ControlPhotoelectric cells can be used either simply to switch lighting on and off, or for dimming. By using an internally mounted photoelectric dimming control system, it is possible to ensure that the sum of daylight and electric lighting always reaches the design level by sensing the total light in the controlled area and adjusting the output of the electric lighting accordingly.UNIT IIIENERGY EFFICIENT TECHNOLOGIES IN ELECTRICAL SYSTEMS 82