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Energy Efficiency Options

1. DSM Energy Efficient Technologies
2. Maximum Demand Control
3. Power Factor Correction
4. Motors
5. Pumps & Pumping System
6. Lighting
7. Compressed air
8. Refrigeration
9. New Processes
10. Energy Efficient Equipment
11. References

1.0 DSM Energy Efficient Technologies

The industrial sector uses about 50% of the total commercial energy available in India. In the industrial sector, the major consumers of energy are fertilizer, textile, sugar, cement, and steel. The Indian energy sector is highly energy intensive and efficiency is well below that of other industrialized countries. Efforts are made on a regular basis to promote energy conservation in these countries as this will help reduce the cost of production. It has been estimated that the total conservation potential of this sector is around 25% of the total energy used by it.

If such industries can promote energy conservation, it could lead to substantial reduction in their costs of production. This is the crux of the near term goal Bureau Of Energy efficiency set up under Ministry of Power.

Energy management is very important as all well-planned actions can help reduce an organization’s energy bills and minimize the damage it does to the environment. The two main energy management strategies are conservation and efficiency. This requires the establishment of a system of collection, analysis, and reporting on the organization’s energy consumption and costs.
Up to 75% of electricity use in industry goes through motors and motor driven systems. Another 10% is for lighting and 3-5 % for plant level distribution losses .Energy services such as compressed air is often overlooked and yet a leak in a compressed air line can be wasting lakhs of rupees every year. A precise national level picture on the industrial efficiency is extremely difficult to predict. One cannot ignore the large contribution of Process efficiencies on the energy productivity indices which vary depending on the sector , technology , feed stocks age , management style , etc. Therefore, there is no escape to an in-depth research ; even with the best efforts one may land up a rough or guess estimate which may not find many takers. Besides, relevant details are not often shared in the public domain. The complex issues impacting the industrial sector have to be addressed at the dis- aggregated levels involving the specific sector associations, academic and researchers besides the industry experts. Perhaps, BEE would be able to address this issue as a part of its mandate. It has on its anvil major tasks related to information from the designated consumers as well as fixing energy consumption norms.

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2.0 Maximum Demand Control

3.0 Power Factor Correction

4.0 Motors

Up to 70% of electricity use in industry goes through motors and motor driven systems. Energy services such as compressed air and steam are often overlooked and yet a leak in a compressed air line can be wasting lakhs of rupees every year.
The following suggested measures would enable all electricity users to drive not only an appreciable cost saving but also would keep up efficient at full load between 55 and 95% depending on speed on size and speed – the lower the speed the lower the efficiency, particularly in the case of small horse power motors (below 2 H.P) Power factor is adversely affected by low loading. With over sizing, we have, therefore, increased capital cost of the motor itself, the increased capital cost of matching switchgear and wiring, the increased cost of power factor correction equipment and the increased cost of the electricity itself due to lower efficiencies.

4.1 Motor Idling

Motor idling is a very common feature of industrial usage. Compressors, laths and machines tools in general as well as production lines themselves are all culprits and motors are left on when there is no actual productivity work being done. Depending on circumstances, up to 50% full load current may be taken by idling motors particularly when still connected to gear trains and belt drivers.

The most direct power savings can be obtained by shutting off idling motors, thereby eliminating no-load losses. While the approach is simple, in practice it calls for constant supervision or automatic control. Often, no-load power consumption is considered unimportant. However, the idle no-load current is frequently about the same as the full-load current.
An example of this type of loss in textile mills occurs with sewing machine motors that are generally operated for only brief periods. Although these motors are relatively small (1/3 horsepower), several hundred may be involved at a plant. A switch connected to the pedal can provide automatic shutoff.

4.2 Motor Replacement :
Normally motor replacement will occur because existing units are beyond economical repair. Perhaps In some cases, repairs are still carried out because of the cost of the new motor. This is particularly evident incase of over-sized motors in which both power factor and efficiency are adversely affected and with long periods of idling, matters became worse. A policy should be instituted through the factory to ascertain what the actual full load demands on a particular motor are. This should be done for every motor in the works. Having logged these loads, the actual capacity of the motors should be compared with the figures.
The stock of motors should be reviewed to see if there is a possibility of switching motors so that the large motors which are under-loaded (or oversized) can be replaced by smaller capacity motors available in the factory. Whilst in ideal Circumstances, the moving of motors should mean that only a few small motors need be bought to fill vacancies thus arising it may so happen in some cases that because of the problem of mountings and short peak loads, motors cannot be replaced by smaller units. In this cases replacement by improved efficiency motors should be considered taking advantage of development of energy-efficient motors.

4.3 Energy Efficient Motors
As the efficiency of standard motor at less loading is low, its operating performance get reduces considerably. If the delta to star change over option is not suitable for improving the efficiency, replacement of existing standard motor with energy efficient motor could be very viable. The conditions which increase viability of installing energy efficient motors are as follows :

The efficiency of the Energy efficient motor is almost constant at all percentage loadings. Due to its flat efficiency characteristics, it maintains efficiency almost constant at all loads. Normally, this option is suitable for the motors with rated capacity below 50 HP. The efficiencies of standard motors above 50 HP rating are almost similar to that of energy efficient motors. In many cases, though the initial cost of energy efficient motor is 15 to 20% higher than the standard motor, the simple payback period is less due to the savings.

Design to minimize electrical losses will mean increased cost in terms of better materials. As I2 R losses (heat losses) will be reduced (thus reducing the wind age losses ) However, as the total cost will be higher than for a standard motors with energy efficient motors must be considered.

Factors to be taken into account when looking at the economics of energy efficient motors are:

• The load in terms pf, maximum load and how the ;load fluctuates. From this, the correct see of motor can be established and also, hopefully, some idea of average loading.
• How the standard motor of the required capacity compares at the average load with the energy efficient motor.
• Times and hours of operation during the year.
• Electricity tariffs-including KWh rates and maximum demand charges.
  Typical cases of motor replacement by Energy Efficient Motors have shown pay – back periods of between 6 months and 2-1/2 years, depending on whether the motor is being run continuously over the year or in shingle shift.

4.4 Conversion of Delta connection in to Star Connection

Design to minimize electrical losses will mean increased cost in terms of better materials. As I2 R losses (heat losses) will be reduced (thus reducing the wind age losses ) However, as the total cost will be higher than for a standard motors with energy efficient motors must be considered.

The induction motor with a percentage loading below 50% would operate at lower efficiency in delta mode. This efficiency at low loading can be improved by converting delta connection into star connection. The reported savings due to this conversion varies from around 3% to 10% because the rated output of motor drops to 1/3rd of delta configuration without affecting performance and the percent loading increases as compared to delta mode. This option does not require any capital investment and is one of the least cost options available for the energy conservation in induction motors.

Though the margin of saving due to this option is low, but as the plant installations normally have hundreds of motors, converting most of the under-loaded motors in the plant would result into considerable savings.

Some motors operate on step loading and some on continuously variable load. The motors which operate on step loading, techno-economic feasibility of Delta-Star Automatic Change-over Switch is to be worked out (e.g. a machine with an induction motor performs three operations in its operating cycle resulting into motor loading of 25%, 40% & 80%; in such cases permanent delta to star conversion is not possible. A n automatic delta-star change-over controller could be installed there. It will connect the motor in star mode in 25% & 40% motor load operations; and in delta mode in 80% load operation). For the applications where starting torque requirement is high but otherwise the load is low, Automatic Delta to star Converter can give significant energy savings.

The motors which operate on continuously variable load, feasibility of installing Soft-starter/Energy Saver is to be worked out. This option of permanent Delta to Star conversion can not be implemented for the loads where starting torque requirement is very high. While implementing permanent Delta to Star conversion, care should be taken to decrease the setting of over load protection relay to 2/3 rd of the delta setting.

4.5 Rewound Motors

Rewinding can reduce motor efficiency, depending on the capability of the rewinding shop. Shops do not necessarily use the best rewind procedure to maintain initial performance. In some cases the loss inefficiency, particularly with smaller-sized motors, may not justify rewinding. Ideally, a comparison should be made of the efficiency before and after a rewinding. A relatively simple procedure for evaluating rewind quality is to keep a log of no-load input current for each motor in the population. This figure increases with poor quality rewinds. A review of the rewind shop’s procedure should also provide some indication of the quality of work. Some of the precautions that must be taken are as follows:

• When stripping to rewind a motor, unless the insulation burnout is performed in temperature controlled ovens an inorganic lamination insulation had been used, the insulation between laminations may break down and increase the eddy current losses .
• Roasting the old winding at uncontrolled temperature, or using a hand-held torch to soften varnish for easier coil removal, should signal the need to go elsewhere.
• If the core loss is increased as a result of improper burnout, the motor will operate at a higher temperature and possible fail prematurely.
• If the stator turns are reduced, the stator core loss will increase. These losses are a result of leakage (harmonic) flux induced by load current and vary as the square of the load current.
• When rewinding a motor, if smaller diameter wire is used, the resistance and the I2R losses will increase. Rewinding techniques vary among repair shops and should be investigated before deciding where to have motors rewound.

A rewinding method developed by Wan lass Motor Corporation claims to increase efficiencies as much as 10 percent. The firm’s technique involves replacing the winding in the core with two windings designed to vary motor speed according to load. Claims of improved efficiency have been disputed and trade-offs have been determined to exist in other features of motor design (cost, starting torque, service life, etc.) While the Wan lass motor has been in existence for over a decade, potential users should recognize that the design remains controversial and has been generally regarded in the motor industry as offering no improvement over that which can be achieved through conventional winding and motor design techniques.

4.6 Belts

Closely associated with motor efficiency is the energy efficiency of V-belt drives. Several factors affecting V-belt efficiency are

1. Over belting: A drive designed years ago with ratings in existence then should be reexamined. Higher-rated belts, with resulting increase in efficiency.
2. Tension: Improper tension can cause efficiency losses of up to 10 percent. The best tension for a V-belt is the lowest tension at which the belt will not slip under a full load.
3. Friction: Unnecessary frictional losses will result from misalignment, worn sheaves, poor ventilation, or rubbing of belts against the guard.
4. Sheave diameter: While a sheave change may not be possible, in general, the larger the sheave, the greater the drive efficiency.

Substitution of the notched V-belt (cog belt) for the conventional V-belt offers attractive energy savings. The V-belt is subjected to large compression stresses when conforming to the sheave diameter. The notched V-belt has less material in the compression section of the belt, thereby minimizing rubber deformation and compression stresses. The result is higher operating efficiency for the notched V-belt.

With conventional V-belts the efficiency for power transmission is low as high frictional engagement exists between the lateral wedge surfaces of the belts which cause less power transmission and hence higher power consumption for the same work to be done by the load; but with Flat-belts, this frictional engagement is on the outer pulley diameter only. V-belts contain higher bending cross section and large mass which cause higher bending loss. Also, as each groove of the pulley contains individual V-belt, the tension between the belt and the pulley distributes unevenly which causes unequal wear on the belt. This leads to vibrations and noisy running and hence reduces power transmission further. The consequences could be bearing damage also. This problem can be solved by using energy efficient Flat-belt.

It has been observed that the percentage of energy savings achieved during practical trails fairly match the gain in efficiency represented in above graph. As with the flat belt drive, the frictional engagement and dis-engagement is on the outer pulley diameter, not on the lateral wedge surface as in the case of the V-belt, wear on the belt is less and hence the life of the flat belt drive is higher than V-belt. Some of the applications where conversion of V-belts with Flat belts is much effective are Compressors, Milling machines, Sliding lathes, Rotary printing presses, Stone crushers, Fans, Generators in Hydroelectric power plants etc.

4.8 Using Soft Starters
Soft starters, which have solid state electronic components, are used to control the input voltage according to the torque required by the driven equipment. Thus at almost all the load the motor operates at same efficiency and power factor. This results in smooth starting of the motors by drawing lower current and thus avoiding the high instantaneous current normally encountered. Starting current and torque are directly related to the voltage applied when starting the motor. By reducing the line voltage when the motor is started, soft starter reduces the starting inrush current and eliminates the high impact or jerk starts that causes mechanical wear and damage. Soft starters are useful in cases where motors operate with high impact loads. Some of the applications are Cranes, Conveyors, Hoists, Compressors, Machine tools, Textile machinery, Food processing machinery etc.

4.9. Adjustable Speed Drives & converters
A significant amount of energy is used by industrial processes involving equipments like fans, pumps and compressors. These equipments are seldom used at their full capacity and hence it is required to control the generated flow by one or more external means. The conventional method by far is to use constant speed motors and to control the flow mechanically by using dampers, throttle valve, inlet vanes etc. These mechanical means of achieving flow control have a major disadvantage, in terms of heat and friction, resulting in overall poor efficiency. By using variable speed drives it is possible to vary and regulate the speed of motor driving the pump or fan, in a step-less manner. This results in controlling the flow at the output very easily and efficiently.
The other method of flow control is to change the speed of the motor itself. It results in reduced power consumption. The situation is reversed in case of variable speed operation. When the pump is driven by a variable speed drive, flow reduction is achieved by reducing the speed from full speed to the required speed. For this speed a set of new pump head capacity curves is drawn through the new operating point. How much energy can be saved depends upon various parameters. These are:

• The actual flow requirement over a period of time (utility profile)
• The rated capacity of the motor and actual load
• The conventional method of flow control currently used

Multi-speed motors
Motors can be wound such that two speeds, in the ratio of 2:1, can be obtained. Motors can also be wound with two separate windings, each giving 2 operating speeds, for a total of four speeds. Multi-speed motors can be designed for applications involving constant torque, variable torque, or for constant output power. Multi-speed motors are suitable for applications, which require limited speed control (two or four fixed speeds instead of continuously variable speed), in which cases they tend to be very economical. They have lower efficiency than single-speed motors

Frequency AC Drives
Adjustable frequency drives are also commonly called inverters. They are available in a range of kW rating from fractional to 750 kW. They are designed to operate standard induction motors. This allows them to be easily added to an existing system. The inverters are often sold separately because the motor may already be in place. If necessary, a motor can be included with the drive or supplied separately.

The basic drive consists of the inverter itself which coverts the 50 Hz incoming power to a variable frequency and variable voltage. The variable frequency is the actual requirement, which will control the motor speed.

There are three major types of inverters designs available today. These are known as Current Source Inverters (CSI), Variable Voltage Inverters (VVI), and Pulse Width Modulated Inverters (PWM).

Direct Current Drives (DC)
The DC drive technology is the oldest form of electrical speed control. The drive system consists of a DC motor and a controller. The motor is constructed with armature and field windings. Both of these windings require a DC excitation for motor operation. Usually the field winding is excited with a constant level voltage from the controller.

Then, applying a DC voltage from the controller to the armature of the motor will operate the motor. The armature connections are made through a brush and commutator assembly. The speed of the motor is directly proportional to the applied voltage.
The controller is a phase controlled bridge rectifier with logic circuits to control the DC voltage delivered to the motor armature. Speed control is achieved by regulating the armature voltage to the motor. Often a tach generator is included to achieve good speed regulation. The tach would be mounted on the motor and produces a speed feedback signal that is used within the controller.

Wound Rotor AC Motor Drives (Slip Ring Induction Motors)
Wound rotor motor drives use a specially constructed motor to accomplish speed control. The motor rotor is constructed with windings which are brought out of the motor through slip rings on the motor shaft. These windings are connected to a controller which places variable resistors in series with the windings. The torque performance of the motor can be controlled using these variable resistors. Wound rotor motors are most common in the range of 300 HP and above.

A device which is used to provide continuous range process speed control. An ASDs may be referred to by a variety of names, such as variable speed drives, adjustable frequency drives or variable frequency inverters. An ASD is capable of adjusting both speed and torque from a constant speed electric motor. These may be a) Variable frequency/Voltage AC motor controllers for squirrel cage motors b) DC Motor controllers for DC Motors c) Eddy current clutches for AC Motors d) Cycloconverters (less efficient) e) Hydraulic Drives f) Adjustable belts and pulleys gears g) Throttling valves h) Fan dampers i) Magnetic clutches
A variable frequency drive controls the speed of an AC motor by varying the frequency supplied to the motor. A variable frequency drive has two stages of power conversion- rectifier & inverter. Inverter may be a) Variable Voltage Inverter or Voltage Source Inverter (VSI) b) Current Source Inverter (CSI) and c) Pulse Width Modulated PWM) Inverter .

Solid-state rectifiers are a preferred source of direct current (DC) for DC motors or other DC uses. Motor-generator sets, which have been commonly used for direct current, are decidedly less efficient than solid-state rectifiers. Motor-generator sets have efficiencies of about 70 percent at full load, as opposed to around 96 percent for a solid-state rectifier at full load. When the sets are under loaded, the efficiency is considerably lower because efficiency is the product of the generator and motor efficiencies.

Typically 70% of the electricity used in industry goes through motors and motor driven systems. Examples of motor driven systems are pumps, fans, compressors, conveyors and crushing/mixing. Often these systems can be designed and controlled more efficiently. In a pumping example, improvements to the motor, drive, drive control, pump, and transmission system can improve efficiency by 30%-70%.

Some of the main opportunities for savings are:

5.0 Pumps & Pumping System

5.1 Pump Characteristics

Pumps come in a variety of sizes for a wide range of applications. They can be classified according to their basic operating principle as dynamic or displacement pumps. Dynamic pumps can be sub-classified as centrifugal and special effect pumps. Displacement pumps can be sub-classified as rotary or reciprocating pumps.

In principle, any liquid can be handled by any of the pump designs. Where different pump designs could be used, the centrifugal pump is generally the most economical followed by rotary and reciprocating pumps. Although, positive displacement pumps are generally more efficient than centrifugal pumps, the benefit of higher efficiency tends to be offset by increased maintenance costs.
Since, worldwide, centrifugal pumps account for the majority of electricity used by pumps, the focus of this chapter is on centrifugal pump.

The pressure (head) that a pump will develop is in direct relationship to the impeller diameter, the number of impellers, the size of impeller eye, and shaft speed. Capacity is determined by the exit width of the impeller. The head and capacity are the main factors, which affect the horsepower size of the motor to be used. The more the quantity of water to be pumped, the more energy is required. A centrifugal pump is not positive acting; it will not pump the same volume always. The greater the depth of the water, the lesser is the flow from the pump. Also, when it pumps against increasing pressure, the less it will pump. For these reasons it is important to select a centrifugal pump that is designed to do a particular job.

Since the pump is a dynamic device, it is convenient to consider the pressure in terms of head i.e. meters of liquid column. The pump generates the same head of liquid whatever the density of the liquid being pumped. The actual contours of the hydraulic passages of the impeller and the casing are extremely important, in order to attain the highest efficiency possible. The standard convention for centrifugal pump is to draw the pump performance curves showing Flow on the horizontal axis and Head generated on the vertical axis. Efficiency, Power & NPSH Required, are also all conventionally shown on the vertical axis, plotted against Flow, as illustrated in figure.1 below.

Given the significant amount of electricity attributed to pumping systems, even small improvements in pumping efficiency could yield very significant savings of electricity. The pump is among the most inefficient of the components that comprise a pumping system, including the motor, transmission drive, piping and valves.

5.2 Factors Affecting Pump Performance

Matching Pump and System Head-flow Characteristics
Centrifugal pumps are characterized by the relationship between the flow rate (Q) they produce and the pressure (H) at which the flow is delivered. Pump efficiency varies with flow and pressure, and it is highest at one particular flow rate.

Effect of over sizing the pump
As mentioned earlier, pressure losses to be overcome by the pump as a function of flow – the system characteristics – are also quantified in the form of head-flow curves. The system curve is basically a plot of system resistance i.e. head to be overcome by the pump versus various flow rates. The system curves change with the physical configuration of the system; for example, the system curves depends upon height or elevation, diameter and length of piping, number and type of fittings and pressure drops across various equipment - say a heat exchanger.

A pump is selected based on how well the pump curve and system head-flow curves match. The pump operating point is identified as the point, where the system curve crosses the pump curve when they are superimposed on each other.
The Figure 2 below shows the effect on system curve with throttling.

In the system under consideration, water has to be first lifted to a height – this represents the static head. Then, we make a system curve, considering the friction and pressure drops in the system- this is shown as the green curve. Suppose, we have estimated our operating conditions as 500 m3/hr flow and 50 m head, we will chose a pump curve which intersects the system curve (Point A) at the pump’s best efficiency point (BEP).

But, in actual operation, we find that 300 m3/hr is sufficient. The reduction in flow rate has to be effected by a throttle valve. In other words, we are introducing an artificial resistance in the system. Due to this additional resistance, the frictional part of the system curve increases and thus the new system curve will shift to the left -this is shown as the red curve.

So the pump has to overcome additional pressure in order to deliver the reduced flow. Now, the new system curve will intersect the pump curve at point B. The revised parameters are 300 m3/hr at 70 m head. The red double arrow line shows the additional pressure drop due to throttling.

You may note that the best efficiency point has shifted from 82% to 77% efficiency.
So what we want is to actually operate at point C which is 300 m3/hr on the original system curve. The head required at this point is only 42 meters.

What we now need is a new pump which will operate with its best efficiency point at C. But there are other simpler options rather than replacing the pump. The speed of the pump can be reduced or the existing impeller can be trimmed (or new lower size impeller). The blue pump curve represents either of these options.

Energy loss in throttling
Consider a case where we need to pump 68 m3/hr of water at 47 m head. The pump characteristic curves (A…E) for a range of pumps are given in the Figure 3.

If we select E, then the pump efficiency is 60%

Hydraulic Power = Q (m3/s) x Total head, hd - hs (m) x ? (kg/m3) x g (m2/s) / 1000

= (68/3600) x 47 x 1000 x 9.81
1000
= 8.7 kW
Shaft Power - 8.7 / 0.60 = 14.5 Kw
Motor Power - 14.8 / 0.9 = 16.1Kw (considering a motor efficiency of 90%)
If we select A, then the pump efficiency is 50% (drop from earlier 60%)
Obviously, this is an oversize pump. Hence, the pump has to be throttled to achieve the desired flow. Throttling increases the head to be overcome by the pump. In this case, head is 76 metres.
Hydraulic Power = Q (m3/s) x Total head, hd - hs (m) x ? (kg/m3) x g (m2/s) / 1000

= (68/3600) x 76 x 1000 x 9.81
1000
= 14 kW

Shaft Power - 14 / 0.50 = 28 kW
Motor Power - 28 / 0.9 = 31 kW (considering a motor efficiency of 90%)
Hence, additional power drawn by A over E is 31 –16.1 = 14.9 kW.
Extra energy used - 8760 hrs/yr x 14.9 = 1,30,524 kw.
= Rs. 5,22,096/annum

In this example, the extra cost of the electricity is more than the cost of purchasing a new pump.

5.3 Efficient Pumping System Operation

To understand a pumping system, one must realize that all of its components are interdependent. When examining or designing a pump system, the process demands must first be established and most energy efficiency solution introduced. For example, does the flow rate have to be regulated continuously or in steps? Can on-off batch pumping be used? What are the flow rates needed and how are they distributed in time?

The first step to achieve energy efficiency in pumping system is to target the end-use. A plant water balance would establish usage pattern and highlight areas where water consumption can be reduced or optimized. Good water conservation measures, alone, may eliminate the need for some pumps.

Once flow requirements are optimized, then the pumping system can be analysed for energy conservation opportunities. Basically this means matching the pump to requirements by adopting proper flow control strategies. Common symptoms that indicate opportunities for energy efficiency in pumps are given in the Table .

Table. Symptoms that Indicate Potential Opportunity for Energy Savings

5.4 Effect of speed variation

As stated above, a centrifugal pump is a dynamic device with the head generated from a rotating impeller. There is therefore a relationship between impeller peripheral velocity and generated head. Peripheral velocity is directly related to shaft rotational speed, for a fixed impeller diameter and so varying the rotational speed has a direct effect on the performance of the pump. All the parameters shown in fig 3.1 will change if the speed is varied and it is important to have an appreciation of how these parameters vary in order to safely control a pump at different speeds. The equations relating rotodynamic pump performance parameters of flow, head and power absorbed, to speed are known as the Affinity Laws:

Where:
Q = Flow rate
H = Head
P = Power absorbed
N = Rotating speed

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6.0 Lighting

6.1 Conservation scope
About 17% of energy generated in our country is consumed for lighting and illumination. This area provides for a further saving in energy as, by and by, more efficient luminaries and lighting system have come up. The evolution can be seen if we go through the ready obsolescence of old systems being replaced by the new (viz., incandescent bulbs having place to fluorescent, MV lamps, sodium vapor lamps, development of slim tubes to in existing tube holders, electronic ballasts, usher in saving of 10 to 15%of electricity with no decrease in illumination). From fluorescent lamps to mercury lamps and then to the most efficient sodium vapor lamps is only a short jump. For bay lighting and public lighting, sodium vapor lamps occupy a predominant place with nearly 50% saving of energy. Lighting improvements usually have some of the shortest paybacks. If you can combine your lighting improvement project with other efficiency improvement projects with longer paybacks, you can frequently create a more comprehensive project that meets your company’s financial requirements. The sleeper bonus here is increased productivity—this is not well-quantified yet, but the data is growing.

6.2 Lighting options
A good supply of light does not necessarily mean the consumption of a great deal of energy. If the right lamp is selected for the right type of function, it is possible to save energy. There are four basic types of lighting: incandescent, fluorescent, high intensity discharge, and low pressure sodium.

Incandescent lamps are the least expensive to buy but are the most expensive to operate. They have the shortest lives and are inefficient compared with other lighting types.

Fluorescent lighting is used mainly indoors and is about three to four times as efficient as incandescent lighting. They last about ten times longer than the incandescent types.

Compact fluorescent lamps or CFL are the most significant lighting devices developed for homes in recent years. They combine the efficiency of fluorescent lighting with the convenience and popularity of the incandescent fixtures. They can replace incandescent ones that are roughly three to four times their wattage, saving up to 70% of the initial lighting energy. Although these bulbs cost ten to twenty times more than the ordinary bulbs they last ten to fifteen times as much. In fact all this makes it the most energy efficient option for the purpose of lighting.

High intensity discharge lamps or the HID provide the longest service life and the highest quality of any lighting type. They are commonly used for outdoor lighting and in large indoor areas. These lamps and fixtures can save 70%–90% of lighting energy when they replace incandescent ones. The three most common types of HID lamps are the mercury vapor, metal halide, and high-pressure sodium lamps.

Low pressure sodium lamps are the most efficient artificial lighting, having the longest service life, and maintain their light output better than any other lamp type. They work in some ways like fluorescent lights and is used where color is not so important. Its typical applications include highways and security lighting.

The Table shows the various types of lamp available along with their features.

Based on lighting energy audit & careful assessment and evaluation, bring out improvement options, which could include :

6.4 Case Examples

Energy Efficient Replacement Options
The lamp efficacy is the ratio of light output in lumens to power input to lamps in watts. Over the years development in lamp technology has led to improvements in efficacy of lamps. However, the low efficacy lamps, such as incandescent bulbs, still constitute a major share of the lighting load. High efficacy gas discharge lamps suitable for different types of applications offer appreciable scope for energy conservation. Typical energy efficient replacement options, along with the per cent energy saving, are given in Table- below

* Wattages of CFL includes energy consumption in ballasts.
Energy Saving Potential in Street Lighting
The energy saving potential, in typical cases of replacement of inefficient lamps with efficient lamps in street lighting is given in the Table below.

6.5 Some Good Practices in Lighting

Installation of energy efficient fluorescent lamps in place of “Conventional” fluorescent lamps.
Energy efficient lamps are based on the highly sophisticated tri-phosphor fluorescent powder technology. They offer excellent colour rendering properties in addition to the very high luminous efficacy.

Installation of Compact Fluorescent Lamps (CFL's) in place of incandescent lamps.
Compact fluorescent lamps are generally considered best for replacement of lower wattage incandescent lamps. These lamps have efficacy ranging from 55 to 65 lumens/Watt. The average rated lamp life is 10,000 hours, which is 10 times longer than that of a normal incandescent lamps. CFL's are highly suitable for places such as Living rooms, Hotel lounges, Bars, Restaurants, Pathways, Building entrances, Corridors, etc.

Installation of metal halide lamps in place of mercury / sodium vapour lamps.
Metal halide lamps provide high color rendering index when compared with mercury & sodium vapour lamps. These lamps offer efficient white light. Hence, metal halide is the choice for colour critical applications where, higher illumination levels are required. These lamps are highly suitable for applications such as assembly line, inspection areas, painting shops, etc. It is recommended to install metal halide lamps where colour rendering is more critical.

Installation of High Pressure Sodium Vapour (HPSV) lamps for applications where colour rendering is not critical.
High pressure sodium vapour (HPSV) lamps offer more efficacy. But the colour rendering property of HPSV is very low. Hence, it is recommended to install HPSV lamps for applications such street lighting, yard lighting, etc.
Installation of LED panel indicator lamps in place of filament lamps.

Panel indicator lamps are used widely in industries for monitoring, fault indication, signaling, etc. Conventionally filament lamps are used for the purpose, which has got the following disadvantages:

6.5 Light distribution

Energy efficiency cannot be obtained by mere selection of more efficient lamps alone. Efficient luminaires along with the lamp of high efficacy achieve the optimum efficiency. Mirror-optic luminaires with a high output ratio and bat-wing light distribution can save energy.

For achieving better efficiency, luminaires that are having light distribution characteristics appropriate for the task interior should be selected. The luminaires fitted with a lamp should ensure that discomfort glare and veiling reflections are minimised. Installation of suitable luminaires, depends upon the height - Low, Medium & High Bay. Luminaires for high intensity discharge lamp are classified as follows:

System layout and fixing of the luminaires play a major role in achieving energy efficiency. This also varies from application to application. Hence, fixing the luminaires at optimum height and usage of mirror optic luminaries leads to energy efficiency.

6.6 Light Control

The simplest and the most widely used form of controlling a lighting installation is "On-Off" switch. The initial investment for this set up is extremely low, but the resulting operational costs may be high. This does not provide the flexibility to control the lighting, where it is not required.

Hence, a flexible lighting system has to be provided, which will offer switch-off or reduction in lighting level, when not needed. The following light control systems can be adopted at design stage:

The advantage of HF electronic ballasts, out weigh the initial investment (higher costs when compared with conventional ballast). In the past the failure rate of electronic ballast in Indian Industries was high. Recently, many manufacturers have improved the design of the ballast leading to drastic improvement in their reliability. The life of the electronic ballast is high especially when, used in a lighting circuit fitted with a automatic voltage stabiliser.

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7.0 Compressed air

Compressed air is used in almost all types of industries and accounts for a major share of the electricity used in some of the plants. It is utilized for a variety of end-uses such as pneumatic tools and equipment, instrumentation, conveying, etc. and is preferred in industries because it is more convenient and safe. The compressor is the main component of this system and its selection must be done carefully. Leakage points have to be identified and sealed, and proper pressure has to be maintained. Compressed air can cost up to five times as much as electricity and offer immense potential for energy savings.

Compressed air is a handy medium for transmitting energy and is often referred to as the fourth utility. It is used extensively in industry and not always in the most efficient manner. Compressed air is used to operate mechanical equipment and power tools, to pressurize, to clean etc. Some industries have specific applications such as paint spraying and bottle forming. Because of the enormity of the potential savings in compressed air consumption there are a number of good websites with details on achieving efficient use. These are listed below.

Compressed air energy consumption is dependant upon the size and nature of the load, the efficiency of the distribution system and the performance characteristics of the motor being used to drive the compressor. Therefore, many of the efficiency issues under Energy Efficient Motors and Drives and Driven Systems also apply here.

Specific compressed air issues are:

Compressed Air System measure includes: optimization of compressed air distribution network; decentralized supply of compressed air at a far-away site; use of multi-stage compressor with inter-cooling; provision for compressed air storage to handle fluctuating loads, Compressed Air System. The measures include: adjust supply pressure to suit the required use; matching of compressors with the loads; supply of air at the lowest temperature; adequate inter-stage cooling of compressed air; provision for evacuation of condensate water from the line; and check leaks in the distribution circuits.

Performance Evaluation:

The description of the tests required to evaluate the performance of the compressor are given below:
Pump - up or capacity Test

This test determines the pumping capacity of the compressors in terms of free air delivery (FAD) i.e. air pumped at atmospheric conditions. To conduct this test, the air receiver of the compressor should be isolated from the system i.e. only compressor should be with the receiver. Drain the air receiver completely. Now, switch on the compressor and observe the time taken by the compressor to maintain the working pressure in air receiver. In other words, note down the time required by the compressor to fill the air receiver up to required pressure. Minimum three readings are required to calculate an average value of time in minutes. Feed this average value in minutes and other values such as receiver diameter, length or volume in the formula to determine the pump-up capacity of the compressor.

The following are different formulas used to evaluate the performance of Compressor :
FAD = V x (P2 - P1) / (Po x T)
Where FAD - Free Air Delivery (m3/min)
V - Volume of the receiver (m3) + volume of the pipeline connected from compressor to air receiver (m3)
Po - Atmospheric Pressure
P1 - Initial Pressure of the receiver (Kg/cm2)
P2 - Final Pressure of the receiver (Kg/cm2)
T - Average Time taken (min)
Specific Power (KW / 100 CFM) = Actual Power x 100 / FAD (CFM)
Where KW - Actual Power drawn by compressor
Compare this value this design value of FAD. If the difference is more than 20%, it is high time to look at piston rings, cylinder bores etc.

Leakage Test
To conduct this test, close all the valves at the equipments where compressed air is in use. Drain the air receiver completely and start the compressor. Note down the time taken by the compressor to maintain the system pressure i.e. up to compressor unloads. This is compressor on load time in seconds. Due to the leakages in the systems (if present), the pressure in the receiver drops to the cut off pressure and again compressor starts. Note down the time taken by system pressure to drop up to cut off pressure. This is compressor off load time in seconds. The readings should be taken minimum three times and the average values are to be used to determine leakages in the lines. Feed these two values in seconds in the formula to determine leakages and its potential.

Leakages (m3/min) = FAD x T1 / (T1 + T2)
Where, FAD - Actual free air delivery of compressor (m3/min)
T1 = Average on load time of compressor (min)
T2 = Average off load time of compressor (min)
Power wasted in Rs. / Annum = 5.54 x L x Operating hours per annum x Rs./KWhr
Where L - Leakages in m3/min
Conversion Factors : M3/hr = NM3/hr x 1.17
Scfm (Standard Cubic foot per minute) = M3/hr x 31.81
M3/min = cfm x 35.3

While large leakages can be detected easily due to hissing sound produced, there are large number of small leakages that are difficult to detect. Small leakages can be detected by applying soap solution on pipelines, joints etc. or with the help of the ultrasonic testing equipments available in the market. Some of the most susceptible points are: Underground pipelines, Threaded pipe joints, Flange connections, Valve steam, Traps and drains, Filters, Hoses, Connectors, Operating valves on pneumatic devices, Check valves, Relief valves, End use machines or tools

Pressure drop in Compressed Airline
In most of the industries, compressed air is supplied from a central compressor room. As per the requirement, the number of compressors list goes up. Finally most industries are saddled with a battery of compressors at one location while end use points are spread over large area. Hence considerable losses take place in the distribution of pipe lines, joints, bends, valves, hoses, couplings etc. Proper sizing of the pipelines and hoses and selection of appropriate type of valves and couplings are essential to ensure efficient operations.

The pressure in a pipeline can be calculated using following formula:
Pressure Drop, Kg/cm2 = 7.57 x (Q1.85) x L x (104) / (d5) x p
Where Q = Air flow in cu.m/min (FAD)
L = Length of pipeline (m)
d = inside diameter of pipe (mm)
P = Initial pressure, kg/cm2
The points to be kept in mind while designing a distribution system are :

A general guide for selection of pipe size as recommended in IS:6202 is that the pressure drop should not exceed 3 kg/sq.cm at the farthest end of the line. For plants, covering large area, the pressure drop up to 0.5 Kg/sq.cm may be acceptable.

The required pipe diameter and length of the pipe line are given in report if the pressure drop exceeds the allowed pressure drop. The pressure drop can be reduced either with the increase in diameter or with reducing the effective length of the pipe but not with both. 

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8.0 Refrigeration

Refrigeration process uses various methods such as the vapor compression system, absorption system, and the steam jet system. An air conditioning and a refrigeration plant are efficient when all the system components, i.e. the compressor, the condenser, the evaporator, the cooling tower, etc., are working in matching condition. Other than the servicing of the components and their maintenance, care should be taken to ensure that the outdoor air is kept at a minimum. Chiller / Air-conditioning System.

The energy conservation measures include: accurate temperature and humidity control to suit the need; maintenance of condenser/evaporator coils; adjustment of chilled water temperature; improved performance of cooling towers; use of timers in specific zones; prevent infiltration of warm in the conditioned space; reduction in mixing of supply and return streams; and duty cycling of air handling units for peak load management. Optimization of multiple chiller’s operation; variation of chilled water flow rate according to the load; variable air volume (VAV) system; enthalpy control (intake of ambient air instead of return air); and option of ice/chilled water storage for peak demand management. 

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9.0 New Processes

Numerous opportunities exist for development of industrial processes with greater efficiency through waste energy reduction, improved energy productivity and industrial cogeneration. The Pacific Northwest Laboratory estimates that up to 3 quads of low-temperature waste heat are recoverable through heat pump technology and as many as 3 quads of high-temperature waste heat are recoverable by advanced heat exchangers with improved design and materials. Ongoing R&D is necessary to tap this full potential.

The Bonneville Power Administration found sizable energy savings available from properly sizing pumps and piping systems for moving water. These are used heavily in food processing, pulp and paper, chemical processing and petroleum processing, as well as for aluminum manufacturing, in high technology plants for maintaining clean rooms, in lumber mills and generally in all industries for cooling air compressors and supplying feed water to boilers. Improved energy productivity encompasses opportunities that range from improving sensors and control systems and reducing the number of processing steps, to such options as membrane separation technologies (chemicals), electrolysis techniques (aluminum, chlorine, magnesium), improved materials (steelmaking), drying (paper) and grinding (cement) and coating methods (solvents on metals).

The measures may cover: use of plasma torches (e.g. metal cutting, welding, acetylene production, reheating of blast furnaces top gas, water disposal); mechanical recompression of vapor for concentration of agro-food and chemical products, effluent stream depollution; membranes application for reverse osmosis (concentration of fluids, sea/brackish water desalination), ultra filtration (paint recovery, enzyme purification) and tangential micro-filtration (pre-treatment of water); induction heating of ferrous and non-ferrous metals, heat treatment, heating of thermal fluids, etc.; infrared drying, dehydration, surface treatment, heating of thermal fluids, etc.; ultra-violet radiation for sterilization, surface treatment of plastic materials prior to painting; high and ultra-high frequency installation for cooking, de-freezing, drying, and sterilization of products; ceramic regenerative burners, radiant tube self-recuperator, jet and radiant burners; ceramic radiating panel; radiating catalytic panel for utilization in zones inflammable vapors.

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10.0 Energy Efficient Equipment

Mandatory Products

Frost Free (non frost) Refrigerators
Tubular Fluorescent Lamps
Room Air Conditioners
Distribution Transformers

Voluntary Products

Direct Cool Refrigerators
Energy Efficient Induction Motors-Three Phase Squirrel Cage
Pump Sets
Ceiling Fans
Washing Machines
Color Televisions
Stationary Storage Type Water Heaters

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11.0 References

BEE (Bureau of Energy Efficiency) Standard Labeling Program

Guidebooks for National certification Examination for energy Managers and Energy Auditors, BEE
Sidler O.: "An End-Use Measurement Campaign in the Domestic Sector in France" Report for the Commission of the European Community (4.1031/93.58) & for ADEME, France. September 1996
www.energymanagertraining.com

American Council for an Energy Efficient Economy (ACEEE) (www.aceee.org) is dedicated to advancing energy efficiency as a means of promoting both economic prosperity and environmental protection.

Energy Star (www.energystar.gov) is a U.S. government Programme that helps businesses and individuals protect the environment through superior energy efficiency.