Energy Audit

The excessive use of energy in residential, commercial and industrial sectors necessitates the decision maker to always question on how the energy is being used efficiently. Energy used for lighting in a medium industry counts for almost 20% of the total energy used. The small percentage of energy use reduction relates to the lower product cost and higher profit margins.
Therefore, it is important to the decision makers of an industry to have a proper method to audit the building plant and to come up with the practical actions needed in optimizing the use of energy, while at the same time to improve the comfort and product quality. This report shows the data mining application for lighting energy audit that can be used in a typical industrial site.
'Energy Audit' means the verification, monitoring and analysis of use of energy including submission of technical report containing recommendations for improving energy efficiency with cost benefit analysis and an action plan to reduce energy consumption. Energy audit is an important process to be carried out for energy conservation. In energy conservation, the thrust is given on the saving of energy while carrying out the required work. Some amount of energy is always required to carry out the required work which may be associated with inherent losses which cannot be eliminated. For example, in case of an induction motor, to operate it is necessary to pass the current through its winding with generates an alternating flux. This flux is responsible for an iron loss in the machine. The current causes the copper loss and since it is necessary to operate the motor, these losses cannot be eliminated. However, there are some additional losses such as bearing, fictional losses etc which are inherent, that can be reduced. These types of losses and their amount can be located using the technique of energy audit. The reduction of the losses located in energy audit, is done in energy conservation



1.2 Energy Saving 11
1.2 Distribution System 16
3.1 Power Vs Demand Interval 23
3.2 Contract Demand Variation Chart 29
3.3 P.F. Variation Chart 29
4.1 kW Loss Vs % of rated Capacity 33
5.1 % Efficiency Vs % Load 38
5.2 Efficiency/P.F Vs Load 39
5.3 Full Load P.F At Various Speeds 40
5.4 Standard Vs High Efficiency Motor 41
5.5 Components Of Variable Speed Drive 45
5.6 Example Of An Excellent Speed Drive 48
5.7 Example Of Poor Variable Speed Drive 48
6.1 Phasor Form For P.F 55
6.2 Capacitor Locations 58



3.1 Purchased Electrical Energy Trend 24
3.2 G.E.B. BILL 27
3.3 Contract Demand Variation Analysis-I 28
3.4 Contract Demand Variation Analysis-II 28
4.1 Transformers Name Plate Data 34
4.2 Loading Details of Transformer 34
4.3 Transformer Efficiency 35
4.4 Transformer Rationalization 35
5.1 Motor Rating Vs Stray Losses-IEEE 40
5.2 P.F. Correction Table 51
5.3 Loading Details of Drive 53
5.4 Saving by using ESCSS 54
6.1 Health of Capacitor 65
6.2 P.F Improvement At Various Plant 66
7.1 Effect Of Harmonics 72
7.2 Analysis Of Harmonics 73
7.3 Voltage Distortion 73
8.1 Summary 75







1.1 Definition & Objectives of Energy Audit 11
1.2 Need for Energy Audit 12
1.3 Type of Energy Audit 13
1.3.1 Preliminary Energy Audit Methodology 13
1.3.2 Detailed Energy Audit Methodology 13
1.4 Cascade Efficiency 14
1.5 Industrial End User 16


2.1 About The Group N.R. Agarwal Ind. Ltd.
(NRAIL) 17
2.1.1 Profile of Group 17
2.1.2 Profile of Company 17
2.2 Energy Sources 18
2.2.1 Metering System 18
2.2.2 Energy Details 18

2.2.3 Energy Bill 19
2.3 About The Analysis And Calculations 20
2.4 Previous Work 21
2.4.1 Present Work 21


3.1 Electricity Billing 22
3.2 Load Factor 25
3.3 Demand Factor 26
3.4 Conclusion 30


4.1 Introduction 31
4.1.1 Rating Of Transformer 31
4.1.2 Location Of Transformer 31
4.2 Transformer Losses And Efficiency 32
4.3 Analysis In The Industry 34
4.3.1 Present Status 36
4.3.2 Saving Potential 36
4.3.3 Conclusion 36


5.1 Introduction 37
5.2 Motor Efficiency 39
5.3 Energy-Efficient Motors 41
5.4 Motor loading 42
5.4.1 Determining Motor Loading 42
5.5 Variable Frequency Drive 44
5.5.1 VSD Power Conversion 45
5.5.2 Factors For Successful Implementation Of VSD 45
5.5.3 Information Needed To Evaluate Energy
Savings For Variable Speed Application 49
5.6 Power Factor Correction 50
5.7 Energy Saving Devices Cum Soft Starter (ESCSS) 52
5.8 Analysis In The Industry 53
5.8.1 Present Status 54
5.8.2 Saving Potential 54
5.8.3 Conclusion 54


6.1 Introduction 55
6.2 Cost Benefits Of Pf Improvement 57
6.3 Location Of Capacitors 58
6.4 Performance Assessment Of P.F Capacitors 60
6.4.1 Voltage Effects 60
6.4.2 Material Of Capacitors 60
6.4.3 Connections 60
6.4.4 Operational Performance Of Capacitors 61
6.5 Instruments Used For Controlling Pf 62
6.5.1 Automatic Power Factor Control Relay 62
6.5.2 Intelligent Power Factor Controller (IPFC) 63
6.6 Analysis In The Industry 65
6.6.1 Installed Capacity 65
6.6.2 Improving Power Factor 66
6.6.3 Saving Potential 67
6.6.4 Conclusion 67

7.1 Introduction 68
7.2 Major Causes Of Harmonics 70
7.2.1 Electronic Switching Power Converters 70
7.2.2 Arcing Devices 70
7.2.3 Ferromagnetic Devices 70
7.2.4 Appliances 70
7.3 Effects Of Harmonics 72
7.4 Overcoming Harmonics 74
7.4.1 Conclusion 74


8.1 Summary 75
8.2 Recommendations 76
8.2.1 Electricity 76
8.2.2 Motors 76
8.2.3 Drives 77
8.2.4 Buildings 77
8.2.5 Miscellaneous 78
8.2.6 Solar Energy 78
8.2.7 Solar Electricity Generation 79




The fundamental goal of energy management is to produce goods and provide services with the least cost and least environmental effect.

The term energy audit means many things to many people. One definition of energy audit is:

"The judicious and effective use of energy to maximize profits (minimize
costs) and enhance competitive positions"

Another comprehensive definition is:

"The strategy of adjusting and optimizing energy, using systems and procedures so as to reduce energy requirements per unit of output while holding constant or reducing total costs of producing the output from these systems"

The objectives of Energy Audit are:

' To achieve and maintain optimum energy procurement and utilisation, throughout the organization
' To minimise energy costs / waste without affecting production & quality
' To minimise environmental effects.

Fig 1.1 Energy Saving


' In any industry, the three top operating expenses are often found to be energy (both electrical and thermal), labour and materials. If one were to relate to the manageability of the cost or potential cost savings in each of the above components, energy would invariably emerge as a top ranker, and thus energy management function constitutes a strategic area for cost reduction.

' Energy Audit will help to understand more about the ways energy and fuel are used in any industry, and help in identifying the areas where waste can occur and where scope for improvement exists. The Energy Audit would give a positive orientation to the energy cost reduction, preventive maintenance and quality control programmes which are vital for production and utility activities. Such an audit programme will help to keep focus on variations which occur in the energy costs, availability and reliability of supply of energy, decide on appropriate energy mix, identify energy conservation technologies, retrofit for energy conservation equipment etc.

' In general, Energy Audit is the translation of conservation ideas into realities, by lending technically feasible solutions with economic and other organizational considerations within a specified time frame. The primary objective of Energy Audit is to determine ways to reduce energy consumption per unit of product output or to lower operating costs. Energy Audit provides a " bench-mark" (Reference point) for managing energy in the organization and also provides the basis for planning a more effective use of energy throughout the organization.


The type of Energy Audit to be performed depends on:

- Function and type of industry
- Depth to which final audit is needed, and
- Potential and magnitude of cost reduction desired

Thus Energy Audit can be classified into the following two types.

i) Preliminary Audit

ii) Detailed Audit

1.3.1 Preliminary Energy Audit Methodology

Preliminary energy audit is a relatively quick exercise to:

' Establish energy consumption in the organization
' Estimate the scope for saving
' Identify the most likely (and the easiest areas for attention
' Identify immediate (especially no-/low-cost) improvements/ savings
' Set a 'reference point'
' Identify areas for more detailed study/measurement
' Preliminary energy audit uses existing, or easily obtained data

1.3.2 Detailed Energy Audit Methodology

A comprehensive audit provides a detailed energy project implementation plan for a facility, since it evaluates all major energy using systems. This type of audit offers the most accurate estimate of energy savings and cost. It considers the interactive effects of all projects, accounts for the energy use of all major equipment, and includes detailed energy cost saving calculations and project cost.

In a comprehensive audit, one of the key elements is the energy balance. This is based on an inventory of energy using systems, assumptions of current operating conditions and calculations of energy use. This estimated use is then compared to utility bill charges.


' The primary function of transmission and distribution equipment is to transfer power economically and reliably from one location to another.

' Conductors in the form of wires and cables strung on towers and poles carry the high-voltage, AC electric current. A large number of copper or aluminium conductors are used to form the transmission path. The resistance of the long-distance transmission conductors is to be minimized. Energy loss in transmission lines is wasted in the form of I2R losses.

' Capacitors are used to correct power factor by causing the current to lead the voltage. When the AC currents are kept in phase with the voltage, operating efficiency of the system is maintained at a high level.

' Circuit-interrupting devices are switches, relays, circuit breakers, and fuses. Each of these
devices is designed to carry and interrupt certain levels of current. Making and breaking the
current carrying conductors in the transmission path with a minimum of arcing is one of the
most important characteristics of this device. Relays sense abnormal voltages, currents, and
frequency and operate to protect the system.

' Transformers are placed at strategic locations throughout the system to minimize power
losses in the T&D system. They are used to change the voltage level from low-to-high in
step-up transformers and from high-to-low in step-down units.

' The power source to end user energy efficiency link is a key factor, which influences the
energy input at the source of supply.
' If we consider the electricity flow from generation to the user in terms of cascade energy efficiency, typical cascade efficiency profile from generation to 11 ' 33 kV user industry will be as below:

' The cascade efficiency in the T&D system from output of the power plant to the end use is 87% (i.e. 0.995 x 0.99 x 0.975 x 0.96 x 0.995 x 0.95 = 87%) as shown on the next page..

A typical plant single line diagram of electrical distribution system is shown

Fig. 1.2 Distribution System
After power generation at the plant it is transmitted and distributed over a wide network.
The standard technical losses are around 17 % in India (Efficiency = 83%). But the figures
for many of the states show T & D losses ranging from 17 ' 50 %. All these may not
constitute technical losses, since un-metered and pilferage are also accounted in this loss.

' When the power reaches the industry, it meets the transformer. The energy efficiency of the transformer is generally very high. Next, it goes to the motor through internal plant distribution network. A typical distribution network efficiency including transformer is 95% and motor efficiency is about 90%. Another 30 % (Efficiency =70%)is lost in the mechanical system which includes coupling/ drive train, a driven equipment such as pump and flow control valves/throttling etc. Thus the overall energy efficiency becomes 50%. (0.83 x 0.95x 0.9 x 0.70 = 0.50, i.e. 50% efficiency)

' Hence one unit saved in the end user is equivalent to two units generated in the power plant. (1Unit / 0.5Eff = 2 Units)


2.1 ABOUT THE GROUP N.R. Agarwal Ind. Ltd. (NRAIL):

' M/s. N.R. Agrawal Ind. Ltd. is one of the leading manufacturers of high quality papers & hard boards.

' Certain areas are identified where there is a potential for saving in energy.

2.1.1 Profile of Group:

' The N.R. Agarwal Group is engaged in manufacturing of almost all varieties of paper viz, Duplex Board, Kraft papers & News print papers. The foundation of N.R. Agarwal Group dates back to the early 1970s. Under the dynamic leadership of Shri N.R. Agarwal, the group intensified its presence in the Paper Industry. Over a period of two decades, the group has constantly and progressively increased its capacity and upgraded its products keeping in pace with the market requirements. As a result of sustained hard work and foresightedness of Shri N.R. Agarwal, the Group today is the largest manufacturer of recycling of paper product in Asia having a combined capacity of 1,50,000 M.T. of paper per annum and turnover of Rs. 200 Crores for the year ended 31st March 2000.

' As on date, the Group has 6 companies, which are engaged in manufacturing of various qualities of paper, and all units are situated in GIDC, Vapi Gujarat.

2.1.2 Profile of Company:

' M/s. N.R. Agarwal Industries Limited is a public limited company was set up in 1993 for the manufacturing of duplex board with an installed capacity of 15,000 MTPA and then thereafter in 1998 the company diversified into Newsprint paper for production of 30,000 MTPA of Newsprint papers.


' Power is available to the plant from GEB at 11 kV voltage level. There are 2 no. of transformers, 1500 kVA & another is of 1250 kVA.

' Total 3 Nos. DG sets are installed. These DG sets are operating Furnace Oil. Each is having capacity of 1000 kW (@0.8 PF lagging power & @ 60 Hz). The DG set power is being used as a 'base load' and GEB power is being used as a peak load in normal condition.

2.2.1 Metering System:

' The consumption of the power is being recorded at 'Incoming Panel' for GEB metering purpose & type of tariff is HTP 1 GEB Service No. is HT 37560.

2.2.2 Energy Details:

' The transformers are stepping down the 11 kV power.

' GEB power is coming through overhead line. HT OCB is installed to receive the GEB power.

' The contract Demand is 1700 KVA.
' The Actual Maximum Demand was observed 1692 kVA in Aug. 2013.
' The average power factor is 0.986 at metering point.
' The maximum energy consumption was 1000260 kWh in June 2013.

' The profile of the load distribution is as under:

' Illumination 16 kW approx.
' Motive power Load 2475 kW approx.

' The Profile of load distribution of the plant is as per Chart no. 3.1.

2.2.3 Energy Bill:

' The general observation is as under.

Item Monthly Average
Consumption in kWh 5.64 lacs approx
Unit cost for GEB power approx. 565 paise
Unit cost for DG power approx. 400 paise
P.F. 0.986
Max. Demand in KVA in Aug. 13 1692
Contract demand in kW 1700


' We have taken data and references for analysis and calculations of the professionally audited N.R. Agarwal Group by professional Energy Auditors.

' Our report comprises the details of observations along with appropriate also identification of the areas where energy could be saved by employing suitable techno-economic measures recommendation with supporting calculations.

' We hope, with implementation of the finding would certainly bring down the energy consumption of the plant to the lowest possible.

' Our report is based on present operating status of the plant & the recommendations are based on various operational parameters examined, measured data, information furnished to us.

' The executive summary exhibits at a glance, the anticipated recurring annual saving & techno-economical feasibility of recommendation.

' In the previous semester we had completed our work in the LIGHTING area. We had identified the areas where energy audit was needed. We had then worked on the same and we came upon the following conclusions :

' The saving potential by using the ELECTRONICS BALLAST : The annual saving is worked out Rs. 56,900 with the payback period of 13.9 months.

' The saving potential by using the VOLTAGE STABILIZER : The annual saving is worked out Rs. 72000 with the payback period of 6~8 months and investment of Rs.40000.

' The saving potential by using the LED : The annual saving is worked out Rs. 21 lacs with the payback period of 7.1 years.

' The saving potential by using the RETROFIT : The annual saving is worked out Rs. 1.1 lacs with the payback period of 21.6 months.

2.4.1 Present Work:
' The working areas are :

' Bill Analysis

' Transformer Rationalisation

' Motor Loading

' PF Improvement

' Harmonics

' The electricity billing by utilities for medium & large enterprises, in High Tension (HT) category, is often done on two-part tariff structure, i.e. one part for capacity (or demand) drawn and the second part for actual energy drawn during the billing cycle.

' Capacity or demand is in kVA (apparent power) or kW terms. The reactive energy (i.e. kVArh) drawn by the service is also recorded and billed for in some utilities, because this would affect the load on the utility.

' Accordingly, utility charges for maximum demand, active energy and reactive power drawn (as reflected by the power factor) in its billing structure. In addition, other fixed and variable
expenses are also levied.
' The tariff structure generally includes the following components:
a) Maximum demand Charges. These charges relate to maximum demand registered during
month/billing period and corresponding rate of utility.

b) Energy Charges. These charges relate to energy (kilowatt hours) consumed during month /
billing period and corresponding rates, often levied in slabs of use rates. Some utilities now
charge on the basis of apparent energy (kVAh), which is a vector sum of kWh and kVArh.

c) Power factor penalty or bonus rates, as levied by most utilities, are to contain reactive
power drawn from grid.

d) Fuel cost adjustment charges as levied by some utilities are to adjust the increasing fuel
expenses over a base reference value.

e) Electricity duty charges levied with respect to units consumed.

f) Meter rentals

g) Lighting and fan power consumption is often at higher rates, levied sometimes on slab
basis or on actual metering basis.

h) Time Of Day (TOD) rates like peak and non-peak hours are also prevalent in tariff
structure provisions of some utilities.

i) Penalty for exceeding contract demand

j) Surcharge if metering is at LT side in some of the utilities

k) Contract Demand. Contract demand is the amount of electric power that a customer demands
from utility in a specified interval. Unit used is kVA or kW. It is the amount of electric power
that the consumer agreed upon with the utility. This would mean that utility has to plan for the
specified capacity.

' Analysis of utility bill data and monitoring its trends helps energy manager to identify ways
for electricity bill reduction through available provisions in tariff framework, apart from
energy budgeting.
' The utility employs an electromagnetic or electronic trivector meter, for billing purposes.

' It is important to note that while maximum demand is recorded, it is not the instantaneous
demand drawn, as is often misunderstood, but the time integrated demand over the
predefined recording cycle.

' The month's maximum demand will be the highest among such demand values recorded over the month. The meter registers only if the value exceeds the previous maximum demand value and thus, even if, average maximum demand is low, the industry / facility has to pay for the maximum demand charges for the highest value registered during the month, even if it occurs for just one recording cycle duration i.e., 30 minutes during whole of the month. A typical demand curve is shown

Fig. 3.1 Power Vs Demand Interval

' As can be seen from the Figure above the demand varies from time to time. The demand
is measured over predetermined time interval and averaged out for that interval as shown by
the horizontal dotted line.

' Of late most electricity boards have changed over from conventional electromechanical
Trivector meters to electronic meters, which have some excellent provisions that can help the utility as well as the industry. These provisions include:

' Substantial memory for logging and recording all relevant events
' High accuracy up to 0.2 class
' Amenability to time of day tariffs
' Tamper detection /recording
' Measurement of harmonics and Total Harmonic Distortion (THD)
' Long service life due to absence of moving parts
' Amenability for remote data access/downloads

' Some utilities charge Maximum Demand on the basis of minimum billing demand, which may be between 75 to 100% of the contract demand or actual recorded demand whichever is higher.

Table 3.1 Purchased Electrical Energy Trend


' In electrical engineering the load factor is defined as the average load divided by the peak load in a specified time period.

' Typical example of a large commercial electrical bill: KW Demand = 436, KWH Use = 57,200, Number of days in billing cycle = 32

Load Factor % = (57,200 KWH / (32 days X 24 hours per day)) / 436 KW X 100% = 17.08%

' It can be derived from the load profile of the specific device or system of devices. Its value is always less than one because maximum demand is always more than average demand since we will not connect all the loads at a time and that to we will not operate its full capacity. A high load factor means power usage is relatively constant. Low load factor shows that occasionally a high demand is set. To service that peak, capacity is sitting idle for long periods, thereby imposing higher costs on the system. Electrical rates are designed so that customers with high load factor are charged less overall per kWh. This process along with others is called load balancing or peak shaving.
' The load factor can also be defined as the ratio of the energy consumed during a given period to the energy, which would have been used if the maximum load had been maintained throughout that period. For example, load factor for a day (24 hours) will be given by:

' The load factor is closely related to and often confused with the demand factor.

' The major difference to note is that the denominator in the demand factor is fixed depending on the system. Because of this, the demand factor cannot be derived from the load profile but needs the addition of the full load of the system in question.

' In telecommunication, electronics and the electrical power industry, the term demand factor is used to refer to the fractional amount of some quantity being used relative to the maximum amount that could be used by the same system. The demand factor is always less than or equal to one. As the amount of demand is a time dependant quantity so is the demand factor.

' Example: If a residence has equipment which would draw 6,000 W when all equipment was drawing a full load draw a maximum of 3,000 W in a specified time,
then the demand factor = 3,000 W / 6,000 W = 0.5
' This quantity is relevant when trying to establish the amount of load a system should be rated for. In the above example it would be unlikely that the system would be rated to 6,000 W even though there may be a slight possibility that this amount of power many be drawn. This is closely related to the load factor which is the average load divided by the peak load in a specified time period.

TABLE NO:- 3.2
G.E.B. BILL FOR YEAR 2013-14
N.R. Agarwal Ind. Ltd.
Contract Demand- 1700 kVA
MONTH DISCRIPTION Mar-13 Apr-13 May-13 Jun-13 Jul-13 Aug-13 Sep-13 Oct-13 Nov-13 Dec-13 Jan-14 Feb-14 Average MAX & MONTH MIN & MONTH
Total Cons.(kWH) 955555 927480 877720 1000260 891540 393500 351160 279620 324020 305900 242100 219800 564054.6 1000260 Jun-13 219800 Feb-14
Night Hrs. kWH 332340 317920 309360 339520 305160 138000 118220 94120 113020 105900 81800 77380 194395 339520 Jun-13 77380 Feb-14
Time of Use kWH 314255 305440 289220 328460 298820 132940 120000 97180 106980 98600 79800 70660 186862.9 328460 Jun-13 70660 Feb-14
Actual M.D.(kVA) 1625 1655 1652 1683 1686 1692 1588 1592 1053 1136 1058 999 1451.583 1692 Aug-13 999 Feb-14
Billing M.D.(kVA) 1625 1655 1652 1683 1686 1692 1588 1592 1445 1445 1445 1445 1579.417 1692 Aug-13 1445 Nov-13
P.F. 0.986 0.988 0.986 0.937 0.988 0.982 0.993 0.996 0.992 0.99 0.996 0.996 0.986 0.996 Oct-13 0.937 Jun-13
Demand Charges 215000 220400 219860 225440 225980 227060 208340 209060 182600 182600 182600 182600 206795 227060 Aug-13 182600 Nov-13
Energy Charges 3815309 3705540 3502487 3997990 3562170 1570583 1404057 1118023 1293573 1221633 967850 877143.5 2253029.8 3997990 Jun-13 877144 Feb-14
P.F.Adjustment Charges/Rebate -145091 -149186 -134004 -156267 -143950 -57524 -69333 -61045 -61999 -56169 -52921 -48748.19 -94686.3

Time of Use Charges 235691 229080 216915 246345 224115 99705 90000 72885 80235 73950 59850 52995 140147 246345 Jun-13 52995 Feb-14
Total Cons. Charges 4120909 4005834 3805257 4313508 3868315 1839823 1633063 1338922 1494409 1422014 1157379.31 1063990.31 2505285.3 4313508 Jun-13 1063990 Feb-14
Tax on sale 164836 160233 152210 172540 154732 73592 65322 53557 59776 56880.56 46295.17 42559.61 100211.1 172540 Jun-13 42560 Feb-14
Electricity duty 826019 802877 761970 863670 775581 369956 328389 269805 300939 286383 234047.82 214976.39 502884 863670 Jun-13 214976 Feb-14
Meter Charges 750 750 750 750 750 750 750 750 750 750 750 750 750.0
Current month Bill 5112514 4969695 4720187 5350469 4799379 2284123 2027525 1663034 1855874 1766027 1438472.3 1322276.31 3109131.3 5350469 Jun-13 1322276 Feb-14
Avg. Paise/KWH 5.35 5.36 5.38 5.35 5.38 5.80 5.77 5.95 5.73 5.77 5.94 6.02 5.650 6.02 Feb-14 5.35 Jun-13
Avg. Unit Charge/Year 5.65

Table 3.3: Contract Demand Variation Analysis-I
Table No: - 3.3
N.R. Agarwal Ind. Ltd.
C.D. = 1700 kVA Proposed CD = 1200 kVA
Nov-13 1445 1053 392 1020 1053 0
Dec-13 1445 1136 309 1020 1136 0
Jan-14 1445 1058 387 1020 1058 0
Feb-14 1445 999 446 1020 1020 21
Excess MD per Month average 384 5
Excess MD per year approx. 4602 63
Saving without Taxes & Duty 817020
Saving with Taxes & Duty 196085
Saving by Reducing MD in Rs. /year 1013105

Table 3.4: Contract Demand Variation Analysis-II
Table No: - 3.4
N.R. Agarwal Ind. Ltd.
C.D. = 1700 kVA Proposed CD = 1500 kVA

Nov-13 1445 1053 392 1275 1275 222
Dec-13 1445 1136 309 1275 1275 139
Jan-14 1445 1058 387 1275 1275 217
Feb-14 1445 999 446 1275 1275 276
Excess MD per Month average 384 214
Excess MD per year approx. 4602 2562
Saving without Taxes & Duty 367200
Saving with Taxes & Duty 88128
Saving by Reducing MD in Rs. /year 455328

Fig. 3.2: Contract Demand Variation Chart

Fig. 3.3: P.F. Variation Chart

' The total consumption of entire plant is being recorded at 'Supply Point' of Precision Casting by Trivector meter. The energy bills of last 12 months have been summarized in Table No. 3.2.

' Table No. 3.3 shows the saving of Rs. 10.13 lacs can be achieved by revising the Contract Demand of 1200 kVA.

' Table No. 3.4 shows the saving of Rs. 4.55 lacs can be achieved by revising the Contract Demand of 1500 kVA.

' P.F. variation is shown in Fig. No: 3.3. It is observed that the avg. Power factor is 0.986, which is good; there is no further scope for improvement.



' A transformer can accept energy at one voltage and deliver it at another voltage. This permits electrical energy to be generated at relatively low voltages and transmitted at high voltages and low currents, thus reducing line losses and voltage drop.

' Voltage regulation of a transformer is the percent increase in voltage from full load to no load.

' Power transformer is a static equipment & is having efficiency is around 98% & above depending upon the manufactures & their design.

4.1.1 Rating Of Transformer:

' Rating 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 arrive at the kVA rating of the Transformer.

' Diversity factor is defined as the ratio of overall maximum demand of the plant to the sum of individual maximum demand of various equipment.

' Diversity factor varies from industry to industry and depends on various factors such as
individual loads, load factor and future expansion needs of the plant.

' Diversity factor will always be less than one.

4.1.2 Location Of Transformer:

' Location of the transformer is very important as far as distribution loss is concerned. 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 optimization needs for centralized control, operational flexibility etc. This will bring down the distribution loss in cables.


' The efficiency varies anywhere between 96 to 99 percent. The efficiency of the transformers not only depends on the design, but also, on the effective operating load.

' There are two types of losses in transformer:
' Iron losses, which is assumed to be a constant
' Copper losses/ load losses is I2R losses.

' The load losses are affected by loading cycle & power factor. The maximum efficiency of transformer is generally observed at nearly 50% load & not at 100% load.

' Load loss (also called copper loss) is associated with full-load current flow in the trans- former windings. Copper loss is power lost in the primary and secondary windings of a transformer due to the ohmic resistance of the windings. Copper loss varies with the square of the load current. (P = I2R).

' No-load loss (also called core loss) is the power consumed to sustain the magnetic field in the transformer's steel core. Core loss occurs whenever the transformer is energized; core loss does not vary with load. Core losses are caused by two factors: hysteresis and eddy current losses.

' Hysteresis loss is that energy lost by reversing the magnetic field in the core as the magnetizing AC rises and falls and reverses direction.

' Eddy current loss is a result of induced currents circulating in the core.

' Transformer losses as a percentage of load is given in the Figure 1.12.

' For a given transformer, the manufacturer can supply values for no-load loss, PNO-LOAD, and load loss, PLOAD. The total transformer loss, PTOTAL, at any load level can then be calculated from:
PTOTAL = PNO-LOAD + (% Load/100)2 x PLOAD

Fig. 4.1: kW Loss Vs % of rated Capacity

' Where transformer loading is known, the actual transformers loss at given load can be computed as:

' Most energy loss in dry-type transformers occurs through heat or vibration from the core. The new high-efficiency transformers minimise these losses. The conventional transformer is made up of a silicon alloyed iron (grain oriented) core. The iron loss of any transformer depends on the type of core used in the transformer.

' However the latest technology is to use amorphous material - a metallic glass alloy for the core. 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 type of transformers have increased efficiencies
even at low loads ' 98.5% efficiency at 35% load.

' Electrical distribution transformers made with amorphous metal cores provide excellent opportunity to conserve energy right from the installation. Though these transformers are a little costlier than conventional iron core transformers, the overall benefit towards energy savings will compensate for the higher initial investment. At present amorphous metal core transformers are available up to 1600 kVA.

TABLE 4.1: Transformers Name Plate Data
N.R. Agarwal Ind. Ltd.
Specifications : TR - NO.1 TR - NO.2
Sr. No. JN 3251
Make Volt amp Volt amp
kVA Rating 1500 1250
Voltage HV 11000 11000
LV 433 433
Ampere HV 78.73 63.6
LV 2000 1666.64
Vector Group Dyn11 Dyn11
% Impedance Voltage 5.04 2.03
Frequency Hz 50 50

TABLE 4.2: Loading Details of Transformer
N.R. Agarwal Ind. Ltd.
Sr. No. Drive Name V I kW P.F. kVAR kVA Hz
1 Main Incomer from GEB at H.T. OCB Not possible P.T. not available
2 Main incomer from 1500 kVA TR 431 382 280 1 55.2 285 50
3 Main incomer from 1250 kVA TR Not in operation

Table 4.3: Transformer Efficiency
Rated Kva 1500
Actual kVA 285
% Loading 19
Full load Cu Loss in kW 26
Cu loss at actual load 0.94
No load loss in kW 3
Total loss @ actual load 3.94
Operating P.F 0.99
Transformer loading in kW 282.2
Efficiency in % 98.62

Table 4.4: Transformer Rationalization
Rated kVA 1250
Full load Cu. Losses in kW 18
No load loss in kW 1.85
Running hours 24
No. of days / year 365
Unit cost in Rs. 5.65
Saving in Rs./year 91564
Losses assumed as per the IS standard.

' The present installed capacity of transformer is as under.
(1) Transformer No. TR # 1, 1500 KVA, 11kV /433 volt.
(2) Transformer No. TR # 2, 1250 KVA, 11kV /433 volt.

' The details of the rating are as per Table No. 4.1.

' Table No. 4.2 shows the details of % loading & other measurement of Transformers.

' It is observed that the transformer no. 1 is loaded 19 % which is very less of the installed capacity. Table No. 4.3 shows the efficiency of the transformer, which is found 98.62%.
4.3.2 Saving Potential:
' M/s. N.R. Agarwal Ind. Ltd. is already operating one transformer out of two, thus they are saving the no load losses of 1250 kVA transformer. The same is worked out as per Table No.4.4.
4.3.3 Conclusion:

' By Transformer Rationalization, the saving of Rs. 0.92 lacs is achieved as they have already implemented.


' Motor load accounts for about 93 % of power consumption and majority of this is continuous load. A careful study is required for determining performance as in case of motors running cost is vital than capital cost. Measurements of various parameters are taken for the major drives only.

' The efficiency of induction motors varies in directly proportion to their loading hence the motor running at less than 65% load must be having scope for improving their efficiency for reduction in watt losses. It also reduces the power factor & resulting in to higher losses.

' Interchangeability by proper size of motor will increase the efficiency. It is desire to replace with proper size of motors when rewinding is required.

' The efficiency of motor is also reduces by 2 to 5 % by repeated rewinding.

' When motor is lightly loaded, changing the delta winding in to star will reduced voltage by 1/ '3 of applied voltage. Since torque is directly proportional to square of voltage, it will be 1/3 of rated value. This will reduce rpm by about 2 to 3 % in normal motor Use of an electronic device with built in feature for load sensing circuit which sense the status of load and operates the or in star and delta mode in accordance with the load.

' If reduced voltage is given to lowered loaded motor, it reduces the level of magnetization current and flux hence there will be reduction in losses.

' The torque of motor is directory proportional to the square of voltage.

' Motors convert electrical energy into mechanical energy by the interaction between the magnetic fields set up in the stator and rotor windings.

' Industrial electric motors can be broadly classified as induction motors, direct current motors or synchronous motors.

' All motor types have the same four operating components: stator (stationary windings), rotor (rotating windings), bearings, and frame (enclosure).

' The two parameters of importance in a motor are efficiency and power factor.

' The efficiencies of induction motors remain almost constant between 50% to 100% loading.

' With motors designed to perform this function efficiently; the opportunity for savings with motors rests primarily in their selection and use.

' When a motor has a higher rating than that required by the equipment, motor operates at part load. In this state, the efficiency of the motor is reduced.

' Replacement of under loaded motors with smaller motors will allow a fully loaded smaller motor to operate at a higher efficiency.

' This arrangement is generally most economical for larger motors, and only when they are operating at less than one-third to one-half capacity, depending on their size.

FIG. 5.1 % Efficiency Vs % Load


' Two important attributes relating to efficiency of electricity use by A.C. Induction motors are efficiency (??), defined as the ratio of the mechanical energy delivered at the rotating shaft to the electrical energy input at its terminals, and power factor (PF). Motors, like other inductive loads, are characterized by power factors less than one.

' As a result, the total current draw needed to deliver the same real power is higher than for a load characterized by a higher PF.

' An important effect of operating with a PF less than one is that resistance losses in wiring upstream of the motor will be higher, since these are proportional to the square of the current.

' Thus, both a high value for ?? and a PF close to unity are desired for efficient overall operation in a plant.

' Squirrel cage motors are normally more efficient than slip-ring motors, and higher-speed
motors are normally more efficient than lower-speed motors. Efficiency is also a function of motor temperature.

FIG 5.2:Efficiency/P.F Vs Load

FIG 5.3: F.L. P.F At Various Speeds

TABLE 5.1: Motor Rating Vs Stray Losses-IEEE


' Energy-efficient motors (EEM) are the ones in which, design improvements are incorporated specifically to increase operating efficiency over motors of standard design.
' Design improvements focus on reducing intrinsic motor losses.
' Improvements include the use of lower-loss silicon steel, a longer core (to increase active material), thicker wires (to reduce resistance), thinner laminations, smaller air gap between stator and rotor, copper instead of aluminum bars in the rotor, superior bearings and a smaller fan, etc.
' Energy-efficient motors now available in India operate with efficiencies that are typically to 4 percentage points higher than standard motors.
' In keeping with the stipulations of the BIS,energy-efficient motors are designed to operate without loss in efficiency at loads between 75 % and 100 % of rated capacity. This may result in major benefits in varying load applications.
' The power factor is about the same or may be higher than for standard motors. Furthermore, energy- efficient motors have lower operating temperatures and noise levels, greater ability to accelerate higher-inertia loads, and are less affected by supply voltage fluctuations.

FIG 5.4: Standard Vs High Efficiency Motor


5.4.1 Determining Motor Loading

1. By Input Power Measurements

' '''First measure input power Pi with a hand held or in-line power meter
Pi = Three-phase power in kW
' ''Note the rated kW and efficiency from the motor name plate
''''''''''''''''''''''''The figures of kW mentioned in the name plate is for output conditions.
' So corresponding input power at full-rated load

Nameplate full rated kW
Pir = ''''''''''
nfl = Efficiency at full-rated load
Pir = Input power at full-rated load in kW

' 'The percentage loading can now be calculated as follows
Load = Pi/Pir x 100%

2. By Line Current Measurements

' The line current load estimation method is used when input power cannot be measured and only amperage measurements are possible.

' The amperage draw of a motor varies approximately linearly with respect to load, down to about 75% of full load.

' Below the 75% load point, power factor degrades and the amperage curve becomes increasingly non-linear.

' In the low load region, current measurements are not a useful indicator of load. However, this method may be used only as a preliminary method just for the purpose of identification of oversized motors.

% Load =Input load current / Input load current *100 (Valid up to 75% loading)

3. Slip Method

' In the absence of a power meter, the slip method can be used which requires a tachometer.

' This method also does not give the exact loading on the motors.
Load =(Slip / Ss'Sr ) *100%
Load = Output power as a % of rated power
Slip = Synchronous speed - Measured speed in rpm
Ss = Synchronous speed in rpm at the operating frequency
Sr = Nameplate full-load speed

' Slip also varies inversely with respect to the motor terminal voltage squared. A voltage correction factor can, also, be inserted into the slip load equation.

' The voltage compensated load can be calculated as shown

Load = Output power as a % of rated power
Slip = Synchronous speed - Measured speed in rpm
Ss = Synchronous speed in rpm
Sr = Nameplate full-load speed
V = RMS voltage, mean line to line of 3 phases
Vr = Nameplate rated voltage

' Variable frequency drive saves energy compared to damper control and throttling & help in modifying the pump & fan performance characteristic to match the system requirement. Normally, to reduce the system flow, the outlet damper is partially closed to reduce the available input pressure to the system.

' At the same time, it is blocking the output of the fan and creating backpressure. This backpressure reduces the volume that can be supplied.

' The power required varies as the square of the pressure, and the cube of the flow. The variation of flow, head & power with speed is having following relation ship (i) Flow ?? speed (ii) head ?? speed2 (iii) power ?? speed3.

' Although there are many methods of varying the speeds of the driven equipment such as
hydraulic coupling, gear box, variable pulley etc., the most possible method is one of
varying the motor speed itself by varying the frequency and voltage by a variable frequency drive.

' The speed of an induction motor is proportional to the frequency of the AC voltage applied to it, as well as the number of poles in the motor stator. This is expressed by the equation: RPM = (f x 120) / p. Where f is the frequency in Hz, and p is the number of poles in any multiple of 2.

' Therefore, if the frequency applied to the motor is changed, the motor speed changes in direct proportion to the frequency change.

' The control of frequency applied to the motor is the job given to the VSD. The VSD's basic principle of operation is to convert the electrical system frequency and voltage to the frequency and voltage required to drive a motor at a speed other than its rated speed.

' The two most basic functions of a VSD are to provide power conversion from one frequency to another, and to enable control of the output frequency.


' As illustrated by Figure 5.5, there are two basic components, a rectifier and an inverter, to accomplish power conversion.

' The rectifier receives the 50-Hz AC voltage and converts it to direct current (DC) voltage.

' A DC bus inside the VSD functions as a "parking lot" for the DC voltage.

' The DC bus energizes the inverter, which converts it back to AC voltage again.

' The inverter can be controlled to produce an output frequency of the proper value for the desired motor shaft speed.

FIG 5.5: Components Of Variable Speed Drive


a) Load Type for Variable Frequency Drives

' The main consideration is whether the variable frequency drive application require a variable torque or constant torque drive.
' If the equipment being driven is centrifugal, such as a fan or pump, then a variable torque drive will be more appropriate.

' Energy savings are usually the primary motivation for installing variable torque drives for centrifugal applications.

' For example, a fan needs less torque when running at 50% speed than it does when running at full speed.

' Variable torque operation allows the motor to apply only the torque needed, which results in reduced energy consumption. Conveyors, positive displacement pumps, punch presses, extruders, and other similar type applications require constant level of torque at all speeds.

' In which case, constant torque variable frequency drives would be more appropriate for the job. A constant torque drive should have an overload current capacity of 150% or more for one minute.

' Variable torque variable frequency drives need only an overload current capacity of 120% for one minute since centrifugal applications rarely exceed the rated current.

' If tight process control is needed, then you may need to utilize a sensor less vector, or flux vector variable frequency drive, which allow a high level of accuracy in controlling speed, torque, and positioning.

b) Motor Information

' Full Load Amperage Rating. Using a motor's horsepower is an inaccurate way to size variable frequency drives.

' Speed Range. Generally, a motor should not be run at any speed less than 20% of its specified maximum speed allowed. If it is run at a speed less than this without auxiliary motor cooling, the motor will overheat. Auxiliary motor cooling should be used if the motor must be operated at very slow speeds.

' Multiple Motors. To size a variable frequency drive that will control more than one motor, add together the full-load amp ratings of each of the motors. All motors controlled by a single drive must have an equal voltage rating.

c) Efficiency and Power Factor

' The variable frequency drive should have an efficiency rating of 95% or better at full load.

' Variable frequency drives should also offer a true system power factor of 0.95 or better across the operational speed range, to save on demand charges, and to protect the equipment (especially motors).

d) Protection and Power Quality

' Motor overload protection for instantaneous trip and motor over current.

' Additional Protection: Over and under voltage, over temperature, ground fault, control or microprocessor fault. These protective circuits should provide an orderly shutdown of the VFD, provide indication of the fault condition, and require a manual reset (except under voltage) before restart.

' Under voltage from a power loss shall be set to automatically restart after return to normal.

' The history of the previous three faults shall remain in memory for future review.

' If a built-up system is required, there should also be externally-operated short circuit protection, door-interlocked fused disconnect and circuit breaker or motor circuit protector (MCP)

' To determine if the equipment under consideration is the right choice for a variable speed drive:

' The load patterns should be thoroughly studied before exercising the option of VSD. In effect the load should be of a varying nature to demand a VSD ( refer figure 5.6 & 5.7).

' The first step is to identify the number of operating hours of the equipment at various load conditions.

' This can be done by using a Power analyzer with continuous data storage or by a simple energy meter with periodic reading being taken.

FIG 5.6 Example Of An Excellent Speed Drive

FIG 5.7 Example Of Poor Variable Speed Drive


1. Method of flow control to which adjustable speed is compared:
' Output Throttling (Pump) Or Dampers (Fan)
' Recirculation (Pump) Or Unrestrained Flow (Fan)
' Adjustable-Speed Coupling (Eddy Current Coupling)
' Inlet Guide Vanes Or Inlet Dampers (Fan Only)
' Two-Speed Motor.

2. Pump or fan data:
' Head vs flow curve for every different type of liquid (pump) or gas (fan) that is handled
' Pump efficiency curves.

3. Process information:
' Specific gravity (for pumps) or specific density of products (for fans)
' System resistance head/flow curve
' Equipment duty cycle, i.e. Flow levels and time duration.

4. Efficiency information on all relevant electrical system apparatus:
' Motors, Constant And Variable Speed
' Variable Speed Drives
' Gears
' Transformers.

' If we do not have precise information for all of the above, we can make reasonable assumptions for points 2 and 4.


' As noted earlier, induction motors are characterized by power factors less than unity, leading to lower overall efficiency (and higher overall operating cost) associated with a plant's electrical system.

' Capacitors connected in parallel (shunted) with the motor are typically used to improve the power factor.

' The impacts of PF correction include reduced kVA demand (and hence reduced utility demand charges), reduced I2R losses in cables upstream of the capacitor (and hence reduced energy charges), reduced voltage drop in the cables (leading to improved voltage regulation), and an increase in the overall efficiency of the plant electrical system.

' It should be noted that PF capacitor improves power factor from the point of installation back to the generating side.

' It means that, if a PF capacitor is installed at the starter terminals of the motor, it won't improve the operating PF of the motor, but the PF from starter terminals to the power generating side will improve, i.e., the benefits of PF would be only on upstream side.

' The size of capacitor required for a particular motor depends upon the no-load reactive kVA (kVAR) drawn by the motor, which can be determined only from no-load testing of the motor.

' In general, the capacitor is then selected to not exceed 90 % of the no-load kVAR of the motor. (Higher capacitors could result in over-voltages and motor burn-outs).

' Alternatively, typical power factors of standard motors can provide the basis for conservative estimates of capacitor ratings to use for different size motors.

' The capacitor rating for power connection by direct connection to induction motors is shown in Table 5.2.

TABLE 5.2: P.F. Correction Table

' From the above table, it may be noted that required capacitive kVAr increases with decrease in speed of the motor, as the magnetizing current requirement of a low speed motor is more in comparison to the high speed motor for the same HP of the motor. Since a reduction in line current, and associated energy efficiency gains, are reflected backwards from the point of application of the capacitor, the maximum improvement in overall system efficiency is achieved when the capacitor is connected across the motor terminals, as compared to somewhere further upstream in the plant's electrical system.

' However, economies of scale associated with the cost of capacitors and the labor required to install them will place an economic limit on the lowest desirable capacitor size.


' Microprocessor based soft starters are available which continuously monitor the efficiency of the motor by utilizing micro computer and ensures the input power to the motor corresponding to the load requirement. This control releases the power smoothly, and steplessly to the motor as per the requirement.

' A soft start and soft stop facility eliminates the high inrush current during starting in turn reduces the contract demand considerably. It also improve the power factor thus reduce the cable losses and improve the overall power factor. Because of soft start, it reduces the mechanical stresses on gear, chain, belt etc.

' The saving to the tune of 40~50% is achievable in certain applications where frequent load ~ unload conditions are developed such as in air compressors, conveyers. Some of the drives which are operated at partial loading, or with variable load where saving to the tune of 25~40% can be achieved, such as in case of agitators motor, lathe machines, pulpers, grinders, crushers, fans etc.

Table 5.3: Loading Details of Drive
Table No:- 5.3
N.R. Agarwal Ind. Ltd.
Sr.No. Drive Name H.P. kW V I kW P.F. %Loading
1 Vaccum pump No-4 120 89.52 421 111 68 0.84 76.0
2 Agitator No-6 20 14.92 411 15.5 6.68 0.68 44.8
3 M/C fresh water 20 14.92 408 26.9 15.7 0.78 105.2
4 P/L power screen-1 15 11.19 409 17.9 10.6 0.8 94.7
5 P/L power screen-2 15 11.19 410 21.5 10.5 0.88 93.8
6 Chest pump No-14 15 11.19 425 14.1 8.39 0.8 75.0
7 Chest pump No-9 15 11.19 412 13.9 8.64 0.82 77.2
8 Chest pump No-16 15 11.19 417 14.3 8.03 0.77 71.8
9 Agitator No-15(VFD) 20 14.92 401 6.45 4.97 0.97 33.3
10 Agitator No-16 20 14.92 407 15.2 8.64 0.73 57.9
11 Agitator No-13(VFD) 20 14.92 410 3.57 3.02 0.99 20.2
12 Agitator No-14 15 11.19 405 18.2 10.8 0.84 96.5
13 Agitator No-12 15 11.19 415 16.2 7.2 0.63 64.3
14 Agitator No-11 15 11.19 419 9.78 2.62 0.34 23.4
15 Agitator No-5 15 11.19 409 13.1 5.83 0.57 52.1
16 M.G. blower 30 22.38 415 31.3 16.5 0.77 73.7
17 Fan pump No-1 30 22.38 415 31.3 16.5 0.77 73.7
18 Fan pump No-3 30 22.38 415 31 19.1 0.86 85.3
19 Vacuum Pump No-1 75 55.95 414 78.1 50 0.9 89.4
20 M.G. blower 60 44.76 414 78.1 50 0.9 111.7
21 Coating Blower 30 22.38 412 27.6 16.3 0.82 72.8
22 Mould Blower 30 22.38 419 13.3 6.51 0.85 29.1
23 Chest pump No-12 20 14.92 418 16.4 9.66 0.79 64.7
24 Line shaft main motor D.C. 200 149.2 414 181 96.1 0.76 64.4
25 B/L premium C/C pump (VFD) 75 55.95 414 81.5 60 1 107.2
26 Chest pump No-1 30 22.38 396 44.1 27.6 0.91 123.3
27 Chest pump No-3 20 14.92 415 14.8 8.14 0.77 54.6
28 Air Comp No-1 30 22.38 397 22.5 12.1 0.77 54.1
29 Air Comp No-3 20 14.92 396 24.4 14 0.84 93.8

Table 5.4: Saving by using ESCSS
Table No:-5.4
N.R. Agarwal Ind. Ltd.
Saving by using ESCSS
Sr.No. Drive Name kW V (Volt) I (Amp) kW P.F. kVAR kVA Hz % Loading
1 Agitator No-11 11.19 419 9.78 2.62 0.34 23.4 4.18 49.5 23.41
2 Agitator No-5 11.19 409 13.1 5.83 0.57 52.1 5.14 50 52.10
3 Rating of the drive 11.19
4 No. of drives 2
5 Measured consumption 8.45
6 Expected saving by use of ESCSS 25%

7 Saving in kW for total 2.1125
8 Running hours 24
9 No. of days / year 365
10 Unit cost in Rs. 4
11 Saving in Rs./year 74022
12 Cost of soft starter in Rs. 150000
13 Depreciation available @ 35% 52500
14 Net cost of soft starter in Rs. 97500
15 Payback period in month 16

5.8.1 Present Status:

' We have measured the parameters of the various drives & the same is shown as per Table No: - 5.3.
5.8.2 Saving Potential:
' Based on the measurement & evaluation of efficiency of the various drives we propose to use microprocessor based Energy Saver Cum Soft Starter (ESCSS) for some of the drives. The details of the drives needs microprocessor based energy saver cum soft starter along with the propose investment & saving are indicated in Table No: - 5.4.
5.8.3 Conclusion:

' The saving of Rs.74022 can be achieved by using ESCSS for various drives with an investment of Rs. 97500 having payback period of 16 months.

' Various Electrical devices such as Induction motors, Power & Welding Transformers, Induction furnaces, electromagnetic choke of fluorescent lamps disturb the waveform as it draws large quantity of reactive power & this system operates at low power factor.

' The power factor is the ratio of the actual power being used in the system (in kW), to the power (in kVA), which is apparently being drawn.

' The actual/active (in kW) power does the work & due to poor power factor for given kW. The higher current will be drawn from the transformers, in turn from transmission line. Due to higher current drawn from system, the I2R losses will be increased, therefore need to over size the conductor & capacity of equipment by installing appropriate size of capacitors, which correct the power factor, which is disturbed by Inductive load, & can bring nearer to the unity Power Factor.

' Total Power is measured in kVA (Kilo Volts-Amperes) (See Figure 6.1).

FIG. 6.1: Phasor Form For P.F

' The active power (shaft power required or true power required) in kW and the reactive power required (kVAr) are 90?? apart vectorically in a pure inductive circuit i.e., reactive power kVAr lagging the active kW.

' The vector sum of the two is called the apparent power or kVA, as illustrated above and the kVA reflects the actual electrical load on distribution system.

' The ratio of kW to kVA is called the power factor, which is always less than or equal to unity.

' Theoretically, when electric utilities supply power, if all loads have unity power factor, maximum power can be transferred for the same distribution system capacity. However, as the loads are inductive in nature, with the power factor ranging from 0.2 to 0.9, the electrical distribution network is stressed for capacity at low power factors.


(1) Reactive component of the network is reduced and so also the total current in the system from the source end I2R power losses are reduced in the system because of reduction in current.

(2) Voltage level at the load end is increased.

(3) kVA loading on the source generators as also on the transformers and lines upto the capacitors reduces giving capacity relief.

(4) A high power factor can help in utilising the full capacity of your electrical system.


' While costs of PF improvement are in terms of investment needs for capacitor addition the benefits to be quantified for feasibility analysis are:

' Reduced kVA (Maximum demand) charges in utility bill

' Reduced distribution losses (KWH) within the plant network

' Better voltage at motor terminals and improved performance of motors

' A high power factor eliminates penalty charges imposed when operating with a low power factor

' Investment on system facilities such as transformers, cables, switchgears etc for delivering load is reduced.


' The primary purpose of capacitors is to reduce the maximum demand. Additional benefits are derived by capacitor location. The Figure 6.2 indicates typical capacitor locations.

FIG. 6.2: Capacitor Locations

' Maximum benefit of capacitors is derived by locating them as close as possible to the load.

' At this location, its kVAr are confined to the smallest possible segment, decreasing the load current. This, in turn, will reduce power losses of the system substantially. Power losses are proportional to the square of the current.

' When power losses are reduced, voltage at the motor increases; thus, motor performance also increases. Locations C1A, C1B and C1C of Figure 1.9indicate three different arrangements at the load.

' Note that in all three locations extra switches are not required, since the capacitor is either switched with the motor starter or the breaker before the starter.

' Case C1A is recommended for new installation, since the maximum benefit is derived and the size of the motor thermal protector is reduced.

' In Case C1B, as in Case C1A, the capacitor is energized only when the motor is in operation. Case C1B is recommended in cases where the installation already exists and the thermal protector does not need to be re-sized. In position C1C, the capacitor is permanently connected to the circuit but does not require a separate switch, since capacitor can be disconnected by the breaker before the starter.

' It should be noted that the rating of the capacitor should not be greater than the no-load magnetizing kVAr of the motor. If this condition exists, damaging over voltage or transient torques can occur. This is why most motor manufacturers specify maximum capacitor ratings to be applied to specific motors.

' The next preference for capacitor locations as illustrated by Figure 1.9 is at locations C2 and C3. In these locations, a breaker or switch will be required. Location C4 requires a high voltage breaker.

' The advantage of locating capacitors at power centres or feeders is that they canbe grouped together. When several motors are running intermittently, the capacitors are permitted to be on line all the time, reducing the total power regardless of load.

' From energy efficiency point of view, capacitor location at receiving substation only helps the utility in loss reduction. Locating capacitors at tail end will help to reduce loss reduction within the plants distribution network as well and directly benefit the user by reduced consumption.

' Reduction in the distribution loss % in kWh when tail end power factor is raised from PF1 to a new power factor PF2, will be proportional to


6.4.1 Voltage Effects:

' Ideally capacitor voltage rating is to match the supply voltage.

' If the supply voltage is lower, the reactive kVAr produced will be the ratio V1 /V2 where V1 is the actual supply voltage & V2 is the rated voltage.

' On the other hand, if the supply voltage exceeds rated voltage, the life of the capacitor is adversely affected.

6.4.2 Material Of Capacitors:

' Power factor capacitors are available in various types by dielectric material used as; paper/ polypropylene etc.

' The watt loss per kVAr as well as life vary with respect to the choice of the dielectric material and hence is a factor to be considered while selection.

6.4.3 Connections:

' Shunt capacitor connections are adopted for almost all industry/ end user applications, while series capacitors are adopted for voltage boosting in distribution networks.


' This can be made by monitoring capacitor charging current vis- a- vis the rated charging current. Capacity of fused elements can be replenished as per requirements.

' Portable analyzers can be used for measuring kVAr delivered as well as charging current.

' Capacitors consume 0.2 to 6.0 Watt per kVAr, which is negligible in comparison to benefits.

' Some checks that need to be adopted in use of capacitors are :
i) Nameplates can be misleading with respect to ratings. It is good to check by
charging currents.

ii) Capacitor boxes may contain only insulated compound and insulated
terminals with no capacitor elements inside.

iii) Capacitors for single phase motor starting and those used for lighting
circuits for voltage boost, are not power factor capacitor units and these



' It controls the power factor of the installation by giving signals to switch on or off power factor correction capacitors. Relay is the brain of control circuit and needs ors of appropriate rating for switching on/off the capacitors.

' There is a built-in power factor transducer, which measures the power factor of the installation and converts it to a DC voltage of appropriate polarity.

' This is compared with a reference voltage, which can be set by means of a knob calibrated in terms of power factor

' When the power factor falls below setting, the capacitors are switched on in sequence.

' The relays are provided with First in First out (FIFO) and First in Last Out (FILO) sequence.

' The capacitors controlled by the relay must be of the same rating and they are switched on/off in linear sequence.

' To prevent over correction hunting, a dead band is provided.

' This setting determines the range of phase angle over which the relay does not respond; only when the PF goes beyond this range, the relay acts.

' When the load is low, the effect of the capacitors is more pronounced and may lead to hunting.

' Under current blocking (low current cut out) shuts off the relay, switching off all capacitors one by one in sequence, when load current is below setting.

' Special timing sequences ensure that capacitors are fully discharged before they are switched in.

' This avoids dangerous over voltage transient. The solid state indicating lamps (LEDS) display various functions that the operator should know and also and indicate each capacitor switching stage.


' This controller determines the rating of capacitance connected in each step during the first hour of its operation and stores them in memory.

' Based on this measurement, the IPFC switches on the most appropriate steps, thus eliminating the hunting problems normally associated with capacitor switching.

' Intelligent Features

' Three phase sensing

' Intelligent Power Factor Controlling based on the capacitor bank

' Switching history (No of operations, ON time) improves the capacitor life time

' 6 or 8 or 12 switching relay outputs

' Automatic or manual control (manual control with power backup option)

' User programmable:

' Star/Delta
' Lead and lag limits
' PT and CT ratios
' CT secondary
' Minimum switching time (1-99 seconds)
' Minimum discharge time (1-99 seconds)
' Minimum capacitor on time (1-99 seconds)
' Minimum sensing current for controlling operation 100mA - 500mA
' User programmable capacitor value

' Fault detection (Over compensation, Under compensation, Over voltage, Over current, Under voltage, Over harmonics for voltage and current)

' Displays Amps (Average and phase wise) Frequency, W, PF, VAR(Total and Phase wise)

' Four quadrant operation

' Advantages

' Three phase sensing gives accurate measurement of PF

' Fault Detection (Over compensation, Under compensation, Over voltage, Over current, Under voltage, Over harmonics for voltage and current)

' Automatic or Manual Control (manual control with power backup option)

' Intelligent operation

' Applications

' In all Incomers Fixed power factor corrections individual (e.g. motor, transformers, lighting, etc.)

' Group fixed power factor correction (several equipments connected in a group)

' Harmonic trap applications (e.g. UPS, Frequency Drives and Converters, etc.)


6.6.1 Installed Capacity:
Table 6.1: Health of Capacitor
Table No: - 6.1
Location: - Capacitor Panel (650 kVAr)
Health of Capacitor
kVAr Rated output Amp.
(440 V rating) Amp. Remark
20 26.2 17 21 17 needs checking
25 32.8 20 22 27 needs checking
25 32.8 32 32 30 Healthy
25 32.8 30 30 30 Healthy
20 26.2 29 28 28 Healthy
25 32.8 34 32 32 Healthy
25 32.8 28 30 32 Healthy
25 32.8 33 33 32 Healthy
12.5 16.4 17 18 17 Healthy
25 32.8 35 31 32 Healthy
25 32.8 31 32 32 Healthy
25 32.8 25 31 29 needs checking
25 32.8 32 30 32 Healthy
25 32.8 33 34 34 Healthy
25 32.8 34 34 34 Healthy
12.5 16.4 18 17 17 Healthy
10 13.1 10 9 11 needs checking
50 65.5 55 60 56 needs checking
50 65.5 61 63 63 Healthy
50 65.5 64 64 63 Healthy
50 65.5 54 64 55 needs checking
25 32.8 30 21 24 Healthy
25 32.8 17 16 18 needs checking
25 32.8 11 12 13 needs checking

NOTE : If Ampere Of R-Phase <= Rated output Ampere then that capacitor NEEDS
CHECKING or else it is HEALTHY.

' M/s. N.R. Agarwal Ind. Ltd. has installed the capacitors. The total installed capacity of capacitors is 650 kVAr. An APFC Panel with 200 kVAr capacitors is provided. Table No. 6.1 shows the health of the capacitors. It is found that some of the capacitors needs replacement and the APFC panel needs maintenance for active operation.

6.6.2 Improving Power Factor

TABLE 6.2: P.F Improvement At Various Plant
Table No: - 6.2
P.F. Improvement At Various Plant
Name of the plant A/c plant panel M/c.shope panel Wax shelling tool room panel Melting miscellaneous panel

Present load current (A) 82 22 90 15
Measured PF 0.92 0.7 0.9 0.87
Proposed PF 0.99 0.99 0.99 0.99
Length of the cable 50 40 75 30
Operating hours/day 20 20 20 20
Saving in kWh/day 0.58 0.15 2.4 0.045
Working days/year 300 300 300 300
Saving in kWh/year 174 45 720 13.5
Cost of unit 4.91 4.91 4.91 4.91
Saving in Rs./year 854.34 220.95 3535.2 66.285
Proposed kVAr 25 10 30 5
Cost of the capacitor @RS.200 5000 2000 6000 1000
Payback period in months 70 109 20 181

6.6.3 Saving Potential

' The capacitor at load/motor end will reduce line current requirement for motor for the same output. Due to reduction in line current there will be a lesser voltage drop & reduction in losses, therefore, it will increase the life of cables & machines.

' Also, because of improved voltage profile, the system efficiency will increase and overall system performance will improve.

' A typical calculation at various plants is attached herewith as per table no. 6.2, which exhibit effect on demand with variation in PF.

' The best position for installation of capacitor banks is at or nearer to motor terminals, however due to the space limitation and working environment, the feasibility is to be checked to connect the same in existing set up. Therefore, we suggest to connecting them at respective centers, which will yield maximum benefits.

' Certain load centers are operating on low p.f this causes increased line losses, which can be reduced by improving p.f .

6.6.4 Conclusion

By installing APFC panel for P.F. improvement M/s. N.R. Agarwal Ind. Ltd. can save as per table 6.2 with an investment as shown having payback period as calculated as per Table No. 6.2.

Section-7: HARMONICS

' The harmonic study is conducted in major areas to find out its magnitude & its effect.

' Harmonics is nothing but a distortion of fundamental waveform due to superimposed of an integral multiple of fundamental frequency periodic waveform component. This is caused by nonlinear load.

' Due to superimposition of odd harmonics on the main frequency, higher amount of current will flow. It leads to heating because of skin effect & Eddy current effect. By skin effect losses, increases as the frequency increases & the effective area of conductor is getting reduced due to flow of current near to the outer age of conductor.

' While Eddy current is a circulating current that is induced in metallic part of the system due to magnetic field generated by current carrying conductor & which is proportional to square of the frequency.

' In any alternating current network, flow of current depends upon the voltage applied and the impedance (resistance to AC) provided by elements like resistances, reactance of inductive and capacitive nature.

' As the value of impedance in above devices is constant, they are called linear whereby the voltage and current relation is of linear nature.

' However in real life situation, various devices like diodes, silicon controlled rectifiers, PWM systems, thyristors, voltage & current chopping saturated core reactors, induction & arc furnaces are also deployed for various requirements and due to their varying impedance characteristic, these NON LINEAR devices cause distortion in voltage and current waveforms which is of increasing concern in recent times.

' Harmonics occurs as spikes at intervals which are multiples of the mains (supply) frequency and these distort the pure sine wave form of the supply voltage & current.

' Harmonics are multiples of the fundamental frequency of an electrical power system. If, for example, the fundamental frequency is 50 Hz, then the 5th harmonic is five times that frequency, or 250 Hz. Likewise, the 7th harmonic is seven times the fundamental or 350 Hz, and so on for higher order harmonics.

' Harmonics can be discussed in terms of current or voltage.

' A 5th harmonic current is simply a current flowing at 250 Hz on a 50 Hz system. The 5th harmonic current flowing through the system impedance creates a 5th harmonic voltage.

' Total Harmonic Distortion (THD) express the amount of harmonics.

' The following is the formula for calculating the THD for current: When harmonic currents flow in a power system, they are known as 'poor power quality' or 'dirty power'.

' Other causes of poor power quality include transients such as voltage spikes, surges, sags, and ringing. Because they repeat every cycle, harmonics are regarded as a steady state cause of poor power quality.


' Devices that draw non-sinusoidal currents when a sinusoidal voltage is applied create harmonics.
' Frequently these are devices that convert AC to DC. Some of these devices are listed below:

7.2.1 Electronic Switching Power Converters:
' Computers, Uninterruptible power supplies (UPS), Solid-state rectifiers
' Electronic process control equipment, PLC's, etc
' Electronic lighting ballasts, including light dimmer
' Reduced voltage motor controllers

7.2.2 Arcing Devices
' Discharge lighting, e.g. Fluorescent, Sodium and Mercury vapour
' Arc furnaces, Welding equipment, Electrical traction system

7.2.3 Ferromagnetic Devices
' Transformers operating near saturation level
' Magnetic ballasts (Saturated Iron core)
' Induction heating equipment, Chokes, Motors

7.2.4 Appliances

' TV sets, air conditioners, washing machines, microwave ovens Fax machines, photocopiers, printers. These devices use power electronics like SCRs, diodes, and thyristors, which are a growing percentage of the load in industrial power systems.

' The majority use a 6-pulse converter.

' Most loads which produce harmonics, do so as a steady-state phenomenon. A snapshot reading of an operating load that is suspected to be non-linear can determine if it is producing harmonics.

' Normally each load would manifest a specific harmonic spectrum. Many problems can arise from harmonic currents in a power system. Some problems are easy to detect; others exist and persist because harmonics are not suspected.

' Higher RMS current and voltage in the system are caused by harmonic currents, which can result in any of the problems listed below:

1. Blinking of Incandescent Lights - Transformer Saturation
2. Capacitor Failure - Harmonic Resonance
3. Circuit Breakers Tripping - Inductive Heating and Overload
4. Conductor Failure - Inductive Heating
5. Electronic Equipment Shutting down - Voltage Distortion
6. Flickering of Fluorescent Lights - Transformer Saturation
7. Fuses Blowing for No Apparent Reason - Inductive Heating and Overload
8. Motor Failures (overheating) - Voltage Drop
9. Neutral Conductor and Terminal Failures - Additive Triplen Currents
10. Electromagnetic Load Failures - Inductive Heating
11. Overheating of Metal Enclosures - Inductive Heating
12. Power Interference on Voice Communication - Harmonic Noise
13. Transformer Failures - Inductive Heating


' The ill effects of harmonics are over hearting of conductor, false tripping of circuit breaker, higher flow of current in neutral conductor, over heating of Induction motor, transformer, panel board, & increase hysteresis losses & copper losses.

' Failure of capacitor, error in humming in KW & KVAR meter, disturbance in telecommunication equipment & relays, premature failure of fuses derating the generator, failure of ballast in lighting humming in fan motors etc.

TABLE 7.1: Effect Of Harmonics

1. Transformer Decrease the rating of the transformer as kVA rating of the transformer is designed based on the 50 Hz liner load. It also increase the stress in insulation which cause the failure / break down it also increase the iron losses & eddy current losses hence increase the temperature and noise level.
2. Capacitor & Reactor Capacitor impedance is inversely proportional to frequency. So it offers low impedance to harmonic current. Hence draw the more current than the normal, which over load the capacitor and cause the resonance in the system.
3. Cable Due to skin effect, the effective cross section area for cable / conductor is reduced, hence it increases the I2R losses in turn increase the temperature also.
4. Motors The Copper losses are increases due to skin effect and Iron losses are increases as it is proportional to the square of frequency. This result in to the overheating of the motor. This will de-rate the motor.
5. Circuit breaker Non-liner needs high pick current during stating which can cause for striping.
6. Power Fuses Due to skin effect, the effective cross section area for fuse element reduces, hence the fuse will blow below the rated value of the current.
7. Relays Many electronics relays are sensitive to the frequency and mal function because of harmonics.

' The study covers following areas.

TABLE 7.2: Analysis Of Harmonics

Table No: 7.2
Harmonics at various locations
N.R. Agarwal Ind. Ltd.
Sr. No. Location THD (%) Harmonics (%)
V I 3rd 5th 7th
1 GEB Main Incomer 2.88 9.48 6.94 - - - 1.03 7.53
2 Vacuum pump no. 4 4.79 4.5 1.89 2.28 1.91 2.9 1.03 7.53
3 Agitator No. 15 3.53 70.6 1.12 55.9 2.67 55.3 0.74 2.42
4 Line Shaft Main Motor DC 1.65 2.1 1.69 5.59 0.99 31.1 0.47 7.74
5 I.D. Fan 0.37 - 0.8 8.54 1.13 39.5 0.59 -
6 F.D. Fan 4.77 1.22 0.8 8.54 1.13 39.5 0.59 -
THD = Total Harmonic Distortion

TABLE 7.3: Voltage Distortion
Bus voltage at PCC Individual Voltage
Distortion ( %) TOTAL Voltage
Distortion THD ( %)
Up to 69000 Volt 3.0 5.0
69001 to 161000 Volt 1.5 2.5
161000 above 1.0 1.5


' Tuned Harmonic filters consisting of a capacitor bank and reactor in series are designed and adopted for suppressing harmonics, by providing low impedance path for harmonic component.

' The Harmonic filters connected suitably near the equipment generating harmonics help to reduce THD to acceptable limits.

' In present Indian context where no Electro Magnetic Compatibility regulations exist as a application of Harmonic filters is very relevant for industries having diesel power generation sets and co-generation units.

7.4.1 Conclusion:

' It is observed that harmonic level is found within permissible limit.

TABLE 8.1: Summary
Sr. No. Area / Method Saving in Rs/year Proposed Investment in lacs Payback in month Remark
1 Saving in Energy Bill 17.06 Nil Immediate In Sec. 3
- By reducing CD

2 Saving in Transformer 0.92 Nil Immediate In Sec. 4
- By transformer rationalization

3 Saving in Motor 0.74 0.98 16 In Sec. 5
- By using ESCSS

Total Saving 18.72 0.98 1

8.2.1 Electricity:

' Optimise the tariff structure with utility supplier
' Schedule your operations to maintain a high load factor
' Shift loads to off-peak times if possible.
' Minimise maximum demand by tripping loads through a demand controller
' Stagger start-up times for equipment with large starting currents to minimize load peaking.
' Use standby electric generation equipment for on-peak high load periods.
' Correct power factor to at least 0.90 under rated load conditions.
' Relocate transformers close to main loads.
' Set transformer taps to optimum settings.
' Disconnect primary power to transformers that do not serve any active loads
' Consider on-site electric generation or cogeneration.
' Export power to grid if you have any sur in your captive generation
' Check utility electric meter with your own meter.
' Shut off unnecessary computers, printers, and copiers at night.

8.2.2 Motors:

' Properly size to the load for optimum efficiency.
(High efficiency motors offer of 4 ' 5% higher efficiency than standard motors)
' Use energy-efficient motors where economical.
' Use synchronous motors to improve power factor.
' Check alignment.
' Provide proper ventilation
(For every 10??C increase in motor operating temperature over recommended peak, the motor life is estimated to be halved)
' Check for under-voltage and over-voltage conditions.
' Balance the three-phase power supply.
(An Imbalanced voltage can reduce 3 ' 5% in motor input power)
' Demand efficiency restoration after motor rewinding.
(If rewinding is not done properly, the efficiency can be reduced by 5 ' 8%)

8.2.3 Drives:

' Use variable-speed drives for large variable loads.
' Use high-efficiency gear sets.
' Use precision alignment.
' Check belt tension regularly.
' Eliminate variable-pitch pulleys.
' Use flat belts as alternatives to v-belts.
' Use synthetic lubricants for large gearboxes.
' Eliminate eddy current couplings.
' Shut them off when not needed.

8.2.4 Buildings:

' Seal exterior cracks/openings/gaps with caulk, gasketing, weather-stripping, etc.
' Consider new thermal doors, thermal windows, roofing insulation, etc.
' Install windbreaks near exterior doors.
' Replace single-pane glass with insulating glass.
' Consider covering some window and skylight areas with insulated wall panels inside the building.
' If visibility is not required but light is required, consider replacing exterior windows with insulated glass block.
' Consider tinted glass, reflective glass, coatings, awnings, overhangs, draperies, blinds, and shades for sunlit exterior windows.
' Use landscaping to advantage.
' Add vestibules or revolving doors to primary exterior personnel doors.
' Consider automatic doors, air curtains, strip doors, etc. at high-traffic passages between conditioned and non-conditioned spaces. Use self-closing doors if possible.
' Use intermediate doors in stairways and vertical passages to minimize building stack effect.
' Use dock seals at shipping and receiving doors.
' Bring cleaning personnel in during the working day or as soon after as possible to minimize lighting and HVAC costs.

8.2.5 Miscellaneous:

' Meter any unmetered utilities. Know what is normal efficient use. Track down causes of deviations.
' Shut down spare, idling, or unneeded equipment.
' Make sure that all of the utilities to redundant areas are turned off -- including utilities like compressed air and cooling water.
' Install automatic control to efficiently coordinate multiple air compressors, chillers, cooling tower cells, boilers, etc.
' Renegotiate utilities contracts to reflect current loads and variations.
' Consider buying utilities from neighbours, particularly to handle peaks.

8.2.6 Solar Energy:
' Solar energy is the most readily available and free source of energy since prehistoric times. It is estimated that solar energy equivalent to over 15,000 times the world's annual commercial energy consumption reaches the earth every year.

' India receives solar energy in the region of 5 to 7 kWh/m2 for 300 to 330 days in a year. This energy is sufficient to set up 20 MW solar power plant per square kilometre land area.

' Solar energy can be utilised through two different routes, as solar thermal route and solar
electric (solar photovoltaic) routes. Solar thermal route uses the sun's heat to produce hot
water or air, cook food, drying materials etc. Solar photovoltaic uses sun's heat to produce
electricity for lighting home and building, running motors, pumps, electric appliances, and

' In solar thermal route, solar energy can be converted into thermal energy with the help of solar collectors and receivers known as solar thermal devices.

' The Solar-Thermal devices can be classified into three categories:

' Low-Grade Heating Devices - up to the temperature of 100??C.
' Medium-Grade Heating Devices -up to the temperature of 100??-300??C
' High-Grade Heating Devices -above temperature of 300??C

' Low-grade solar thermal devices are used in solar water heaters, air-heaters, solar cookers
and solar dryers for domestic and industrial applications.
8.2.7 Solar Electricity Generation:

' Solar Photovoltaic (PV): Photovoltaic is the technical term for solar electric. Photo means "light" and voltaic means "electric". PV cells are usually made of silicon, an element that naturally releases electrons when exposed to light. Amount of electrons released from silicon cells depend upon intensity of light incident on it. The silicon cell is covered with a grid of metal that directs the electrons to flow in a path to create an electric current. This current is guided into a wire that is connected to a battery or DC appliance.

' Typically, one cell produces about 1.5 watts of power. Individual cells are connected together to form a solar panel or module, capable of producing 3 to 110 Watts power. Panels can be connected together in series and parallel to make a solar array, which can produce any amount of Wattage as space will allow. Modules are usually designed to supply electricity at 12 Volts. PV modules are rated by their peak Watt output at solar noon on a clear day.

' Solar electric power systems can offer independence from the utility grid and offer protection during extended power failures. Solar PV systems are found to be economical especially in the hilly and far flung areas where conventional grid power supply will be expensive to reach.

' PV tracking systems is an alternative to the fixed, stationary PV panels. PV tracking systems are mounted and provided with tracking mechanisms to follow the sun as it moves through the sky. These tracking systems run entirely on their own power and can increase output by 40%.

' Back-up systems are necessary since PV systems only generate electricity when the sun is shining. The two most common methods of backing up solar electric systems are connecting the system to the utility grid or storing excess electricity in batteries for use at night or on cloudy days.

' Performance. The performance of a solar cell is measured in terms of its efficiency at converting sunlight into electricity. Only sunlight of certain energy will work efficiently to create electricity, and much of it is reflected or absorbed by the material that make up the cell. Because of this, a typical commercial solar cell has an efficiency of 15%'only about one-sixth of the sunlight striking the cell generates electricity. Low efficiencies mean that larger arrays are needed, and higher investment costs. It should be noted that the first solar cells, built in the 1950s, had efficiencies of less than 4%.


' Bureau of Energy Efficiency
' Various Energy Audit reports presented by professional Energy Auditors.
' NPC energy audit manual and reports
' Energy management handbook, John Wiley and Sons - Wayne C. Turner

Source: ChinaStones -

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