energy efficiency of industrial utilities-pratap jung rai

Energy Efficiency of Industrial Utilities

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1. ENERGY EFFICIENCY OF INDUSTRIAL UTILITIES

1.1 Introduction

Increasing Energy Efficiency is the quickest and least costly way of addressing energy security,

economic and environmental challenges. Energy cost is one of the major components in an industry

operation which carries utmost cost in industries run. With the advantages of energy efficiency

practices and technologies, it is possible to cut down energy cost significantly in the industries

without reducing the productivity of industrial utilities.

An energy audit (Energy Efficiency) is an inspection, survey and analysis of energy for energy

conservation in an industry, building, process or system to reduce the amount of energy input to the

system without negatively affect the output. Industrial Energy Audit is fundamental to a

comprehensive energy management programme and is defined in EC Act 2001 as follows:

“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.”

An Energy Audit is a package of services that delivers the following benefits to customers:

a) Increase the goodwill of industries which will raise the health, comfort, safety and prolong

the durability of the property.

b) It helps to protect the environment by reducing unnecessary waste, carbon footprint and

pollution.

c) Undergone awareness regarding energy usage and conservation energy opportunities.

1.2 Objectives of Energy Efficiency of Industrial Utilities

Saving of unnecessary energy consumption is a kind of energy generation, there are several

objectives which is as follows:

To minimize energy costs/waste without affecting production and quality.

Minimize energy, production costs and utilities related risk.

To achieve and maintain optimum energy procurement and utilization, throughout the

industry.

Enhance environmental performance and minimize greenhouse gas emissions.

Reduce exposure to rising energy prices and energy shortages.

Improve reputation with customers, government and public.

1.3 Methodology

Study Area and Field Study

The Study Area of this research paper is Energy Efficiency of Industrial Utilities. Most of the study

of industrial utilities was conducted in Unilever Nepal Limited, Hetauda, Makwanpur. Ganga Soap

and Chemical Pvt. Ltd. And National Soap Industries Pvt. Ltd. Hetauda, Makwanpur in three

month OJT period. Where most of the energy efficiency of industrial utilities technique was known

such as Electric motors, Boiler, Pumps and Pumping system, Compressor and Compressed Air

System. And some utilities such as HVAC system was conducted in Nepal Telecom, Chhauni,

Kathmandu. And furnace in Thapathali Campus, Thapathali under the guidance of Exports. Using

following procedure I was prepared my research paper:

Communication with Energy Audit Exports


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The study had been conducted and research paper was prepared under the direct communication

with Energy Efficiency related Exports; Prof. Dr. Govinda Raj Pokharel, Executive Director of

Alternative Energy Promotion Center, Khumaltar, Kathmandu. Mr. Sanjaya Kumar Yadav,

Electrical Officer, UNL. Mr. Ramesh Yadav, Technical Executive, UNL. Er. Sanjeev Pudasaini,

Technical Officer, UNL, Mr. Shambhu Yadav, HOD of Industrial Engineering, Thapathali Campus

(Trainee of Trainers for energy audit) and Er. Govinda Tiwari, Consultant, SEED Nepal.

Internet and senior reports

Factual data of industrial utilities and its energy consumption scenario, energy losses and core

subject of industrial utilities are taken through internet. And format and some data are taken place

from energy efficiency related senior reports.

Books and energy related newspaper

Most of the calculation parts are extracted from Text Book of Energy Audit, Energy Efficiency

Guide for Industry in Asia, UNEP report. Bureau of Energy Efficiency, India. And Energy

efficiency related newspapers.

1.4 Scope of research on Energy Efficiency of Utilities of Industry

The following are the research areas envisaged under Research paper on “Energy Efficiency of

Basic Utilities of Industry” where includes only the basic industrial utilities of energy performance

assessment.

To calculate the energy performance assessment of industrial utilities.

To know how about the basic parameters of energy efficiency of industrial utilities.

To know condition of industrial utilities energy consumption.

To know the efficiency of industrial utilities.

Identify the financial analysis of industrial utilities and its cost benefit analysis.

1.5 Energy Consumption Scenario of Nepalese Industries

In different parts of Nepal, there are different kinds of industries are running which is shown in fig

(a) (location vs % of industries) and these industries have been using different types of fuel for

different industrial purpose. Which is given in pie chart, the coal is highest amount consumable

fuel; 58.7% and L diesel is least amount consumable fuel; 0.1%.

According to census of manufacturing establishments Nepal 2006-2007 based on number of

establishments of main energy consuming sectors data shows that potential energy consuming

Industrial Energy Consumption by Fuel type 2008/2009 (Source: DOI 2009/10; DCSI 2009/10), Total final energy consumption 13.4 MGJ


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districts are Parsa, Sunsari, Rupandehi, Bara and Morang consumes 7.76%, 7.37%, 7.21%, 6.59%

and 6.15% respectively.


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Fig. (a) location vs % of industries

Are there efficient uses of energy sources (fuel)? How much efficient uses of energy sources? These are the most important questions for

different energy users to know the condition of energy consumption. To know how about the condition of energy consumption and condition

of industrial utilities, Energy audit of industrial utilities is indispensible assessment to know the condition of energy consumption and

condition of industrial utilities. Only Industries can improve their energy consumption through perfect energy audit.

Kathmandu,13.93%

Bhaktapur,3.84%

Lalitpur,5.47%

Kanchanpur,2.89%

Morang,8.46%

Jhapa,3.98% Parsa,6.36%

Rupandehi,6.33%

Sunsari,6.28%

Bara,5.41%

Kaski,4.12%

Kailali,3.31%

Chitwan,2.89%

Banke,2.72%

Nawalparasi,2.13%

Dang,1.51%

Kapilbastu,1.49% Makwanpur,1.60%

Saptari,1.74%

Dhanusha,1.93%

Main Manufacturing Industry Distribution in the Country (Source: www.doind.gov.np)

100 % = 3446 Industry Establishments Source: Census of Manufacturing Establishments Nepal 2006-2007


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1.6 Methodology of Energy Audit of Industries (Source: UNEP)

Basically Industries can improve their energy efficiency through a 6-step Cleaner Production approach.

The ultimate purpose is to keep improving energy efficiency, and this methodology can help companies

do this. But the methodology should be applied flexibly and depending on the company’s situation,

because each company is different: country, sector, size, organizational structure, production processes,

existing energy management systems, and so on.

There are basic steps to carry out energy audit inside the industries

task 6a: Prepare proposal to continue with energy efficiency for top management approval

Step 6: Continuous Improvement

task 4a: Technical, economic and environmental evaluation of options

task 4b: Rank feasible options for implementation

task 4c: Prepare implementation and monitoring proposal for top management approval

Step 4: Feasibility Analysis of Options

task 5a: Implement options and monitor results

task 5b: Evaluation meeting with top management

Step 5: Implementation and Monitoring of Options

task 1a: Meeting with top management

task 1b: Form a Team and inform staff

task 1c: Pre-assessment to collect general information

task 1d: Select focus areas

task 1e: Prepare assessment proposal for top management approval

Step 1: Planning and Organization

task 2a: Staff meeting and training

task 2b: Prepare focus area flow charts

task 2c: Walkthrough of focus areas

task 2d: Quantify inputs and outputs and costs to establish a seline

task 2e: Quantify losses through a material and energy balance

Step 2: Assessment

task 3a: Determine causes of losses

task 3b: Identify possible options

task 3c: Screen options for feasibility analysis

Step 3: Identification of Options


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1.7 Types of Energy Audit and Approach

The type of energy audit to be performed depends on the type of industry, the depth to which Final

Audit is needed, and the potential and magnitude of cost reduction desired. Type of energy audit chosen

depends on:

Function and type of industry

Depth to which final audit is needed

Potential and magnitude of cost reduction desired

Types of energy audit

1) Preliminary energy audit

2) Targeted Energy Audit

3) Detailed energy audit

1) Preliminary Energy Audit

Shortly, called Walk-Through Audit, screening audit and Diagnostic Audit. it is a relatively quick

exercise and uses existing, or easily obtained data. The walk-through audit, as its name implies, is a tour

of the facility to visually inspect each of the energy using systems.it includes an evaluation of energy

consumption data analyze energy use quantities and patterns as well as provide comparison to industry

averages or benchmarks for similar facilities. It is least costly audit but can yield a preliminary estimate

to saving potential and provide a list of low cost saving opportunities via improvements in operational

maintenance practices.

1) Targeted Energy Audit

It often results from preliminary audits. They provide data and detailed analysis on specified target

projects. For example, industries may target its lighting system or boiler system or steam system or

compressed air system with a view of effecting energy savings. Targeted audits therefore involve

detailed surveys of the target subjects and analysis of the energy flows and cost associated with the

targets. Final outcome is the recommendations regarding actions to be taken.

2) Detailed Energy Audit

It is a comprehensive audit and results in a detailed energy project implementation plan for a facility,

since it accounts for the energy use of all major equipment. It considers the interactive effects of various

projects and offers the most accurate estimate of energy saving and cost. Ti includes detailed energy

cost saving calculations and project implementation costs. One of the key elements in a detailed energy

audit is the energy balance. This is based on an inventory of energy-using systems, assumptions of

current operating conditions, measurements and calculations of energy use.

Detailed energy auditing is carried out in three phases

o Pre-audit Phase

o Audit Phase

o Post-Audit

A comprehensive ten step methodology for conducting detailed energy audit is suggested as follows.

However, methodology is flexible and can be adapted depending upon company’s situation, because

each company is different: country, sector, size, organizational structure, production processes, existing

energy management systems, and so on.


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Ten Steps Methodology for Detailed Audit

Step Plan of Action Purpose/ Results

1 Phase I –Pre Audit Phase

Plan and organise

Walk through Audit

Informal Interview with

Energy Manager, Production /

Plant Manager

Resource planning, Establish/organize an Energy audit

team

Organize Instruments & time frame

Macro Data collection (suitable to type of industry.)

Familiarization of process/plant activities

First hand observation & Assessment of current level

operation and practices

2 Conduct of brief meeting /

awareness programme with all

divisional heads and persons

concerned (2-3 hrs.)

Building up cooperation

Issue questionnaire for each department

Orientation, awareness creation

3 Phase II –Audit Phase

Primary data gathering,

Process Flow Diagram, &

Energy Utility Diagram

Historic data analysis, Baseline data collection

Prepare process flow charts

All service utilities system diagram (Example: Single

line power distribution diagram, water, compressed air

& steam distribution.

Design, operating data and schedule of operation

Annual Energy Bill and energy consumption pattern

(Refer manual, log sheet, name plate, interview)

4 Conduct survey and

monitoring

Measurements :

Motor survey, Insulation, and Lighting survey with

portable instruments for collection of more and accurate

data. Confirm and compare operating data with design

data.

5 Conduct of detailed trials /

experiments for selected

energy guzzlers

Trials/Experiments:

- 24 hours power monitoring (MD, PF, kWh

etc.).

- Load variations trends in pumps, fan

compressors etc.

- Boiler/Efficiency trials for (4 – 8 hours)

- Furnace Efficiency trials

Equipments Performance experiments etc.

6 Analysis of energy use Energy and Material balance

Energy loss/waste analysis

7 Identification and development

of Energy Conservation

(ENCON) opportunities

Energy and Material balance & energy loss/waste

analysis

Identification & Consolidation ENCON measures

Conceive, develop, and refine ideas

Review the previous ideas suggested by unit personal

Review the previous ideas suggested by energy audit if

any

Use brainstorming and value analysis techniques

Contact vendors for new/efficient technology


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8 Cost benefit analysis Assess technical feasibility, economic viability and

prioritization of ENCON options for implementation

Select the most promising projects

Prioritise by low, medium, long term measures

9 Reporting & Presentation to

the Top Management Documentation, Report Presentation to the top

Management.

10 Phase III –Post Audit phase

Implementation and Follow-up

Assist and Implement ENCON recommendation measures

and Monitor the performance

Action plan, Schedule for implementation

Follow-up and periodic review

(Reference: General Aspects of Energy Management and Energy Audit, Guide Book for National

Certification Examination for Energy Managers and Energy Auditors)

1.8 Monitoring Equipment for Energy Efficiency

Without monitoring equipments impossible to quantify the condition of Energy Efficiency of Industry,

building, process or systems so it plays vital role to determine and measure the actual operating

parameters of various utilities of industry and compare them with the design parameters to determine if

energy efficiency can be improved or leave them as is it. Parameters that are often monitored during an

energy assessment are:

Basic electrical parameters in AC & DC systems: current (I), voltage (V), power factor (PF),

active power (kW), reactive power (kVAr), energy consumption (kWh), maximum demand

(kVA), frequency (Hz), harmonics, etc.

Other non-electrical parameters: radiation, air and gas flow, liquid flow, emperature C) and

heat flow, revolutions per minute (RPM), noise and vibration, air velocity, dust concentration,

total dissolved solids (TDS), pH, moisture content, relative humidity, flue gas analysis (CO2,

O2, CO, SOx, NOx), combustion efficiency, etc.

Considering above parameter provides information for various monitoring equipment that are often used

during energy assessments in industry, namely as follows:

1. Electrical measuring instruments

2. Combustion analyzer

3. Thermometers

4. Manometers and Pitot tube

5. Water flow meters

6. Psychrometer

7. Tachometers / Stroboscopes

8. Leak detectors

9. Lux meters

10. Thermography

11. Smart Energy Meter

Under here the equipments for industrial utilities audit.


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1 Electrical Measuring Instrument: it includes Clamp-on or power analyzers instrument which

actually measures the power, basically these instruments are applied on-line i.e. on running

motors without any need to stop the motors.

Clamp-on Meter

Clamp-on or power analyzers and are used to measure

main electrical parameters such as KVA, kW, PF, Hertz,

KVAr, Amps and Volts. Some of these instruments also

measure harmonics. Instant measurements can be taken

with hand- held meters, while more advanced ones

facilitates cumulative readings with print outs at specified

intervals.

2 Combustion Analyzer: it is used to measure the composition of flue gases after combustion

has taken place. Basically it measures the percentage of oxygen (O2), or carbon dioxide (CO2)

in the exit flue gases and it calculates the combustion efficiency if required.it usually used to

determine the composition of flue gases in the duct. The duct is the large piping arrangement of

rectangular configuration and is used to flush out the combusted gases to the chimney.

Fuel Efficiency Monitor

Normally, it measures oxygen and temperature of flue

gas. Calorific values of common fuels are fed into the

microprocessor which calculates the combustion

efficiency.

Fyrite

A hand bellow pump draws the flue gas sample into a

solution inside the fyrite. A chemical reaction changes the

liquid volume revealing the amount of gas. The

percentage oxygen or CO2 can be read from the scale.

The unique feature of the fyrite is that the absorbing fluid

is also used as the indicating fluid so that one vessel taken

the place of both measuring burette and absorption

pipette.

Combustion Gas Analyzer

It builds with chemical cells which measure various gases

such as CO2, CO, NOX, SOX etc. it quite flexible in what

must be measured depending on the requirements of the

users.

Basically, it has specific sensors sealed inside the

equipment that can be changed to measure the different

components in the gas. But because a maximum of two

sensors can be connected, only two or three parameters

can be measured at one time.


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3 Thermometer: it is an instrument used to measure the temperature of fluids, surfaces or gases.

Basically, it is used to measure the thermal energy losses or to make a thermal energy balance.

Temperature measurements are taken for the audit of air conditioning units, boilers, furnaces,

steam system, waste heat recovery systems, heat exchanges etc. thermometers are classified as

contact thermometer or non-contact thermometers.

Contact Thermometer

It is simply thermometer which measures the temperature with

physically contact between the thermometer and the object of

which the temperature is determined. It consists of two

dissimilar metals, joined together at one end. The thermocouple

metal alloys are commonly available as wire. A thermocouple is

available in different combinations of metals or calibrations.

Non-contact or infrared

Thermometer

A non-contact or infrared thermometer allows the measurement

of temperatures without physical contact between the

thermometer and the object of which the temperature is

determined. The thermometer is directed at the surface and

immediately gives a temperature reading. This instrument is

useful for measuring hot spots in furnaces, surface temperatures

etc.

infrared thermometer calculates the amount of thermal radiation

emitted from the object and the amount of infrared energy

emitted by object, the object’s temperature can be determined.

4 Manometer: It is widely used instrument in energy audit for measuring the differential

pressure across two pints. In a duct carrying exhaust gases or air. The pressure differential is

then used to calculate the velocity of flow in the duct using the Bernoulli’s equation.

Manometer

Pitot Tube

Digital flexible membrane manometer is used for measuring

pressures in air ducts carrying exhaust flue gases or air from

fans and blowers.

To measure pressure in air pipes, manometers must be in

combination with a pitot tube.

Attach flexible rubber tubes to the ends of the pitot tube

Attach these two tube to the ends to the pitot tube

Make a 6 cm monitoring hole in the duct or pipeline

Insert the pitot tube into the monitoring hole.


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5 Water flow Meter: A flow meter is an instrument used measure the linear, nonlinear, mass or

volumetric flow rate of liquid or a gas. There are many varieties of flow meters and having its

functioning of each model differs from the other. However the basic principle of all remains

same.

Ultrasonic Flowmeter

It is commonly used in dirty applications such as wastewater and

other dirty fluids and slurries which ordinarily cause damage to

conventional sensors. The basic principle of operation employs

the frequency shift (Doppler Effect) of an ultrasonic signal when

it is reflected by suspended particles or gas bubbles in motion.

Spring & Piston Flowmeter

Piston-type flow meters use an annular orifice formed by a

piston and a tapered cone. The piston is held in place at the base

of the cone (in the "no flow position") by a calibrated spring.

Scales are based on specific gravities of 0.84 for oil meters and

1.0 for water meters. Their simple design and the ease with

which they can be equipped to transmit electrical signal has

made them an economical alternative to rotameters for flow rate

indication and control.

6 Psychrometer: A psychrometer is a device used to measure relative humidity of a certain area.

The temperature difference between the dry bulb and wet-bulb temperatures is noted. Then

each is used on a chart to find the relative humidity of that temperature and area. A small

difference between the temperatures of the bulbs shows a high relative humidity coming from a

low evaporation rate. In dry air, evaporation happens faster showing a large difference in

temperature thus giving you a low relative humidity.

Psychrometer

A sling psyshrometer consists of two thermometers mounted

together with a handle. One measures dry bulb temperature and

other measures wet bulb temperature. When reading is to be

taken the psychrometer is whirled around. The water evaporates

from the wick, cooling the wet bulb thermometer. Then the

temperatures of both dry, more moisture evaporates from the

wick, cooling the wet-bulb thermometer more, so there is a

greater difference between the temperatures of the two

thermometers. By using these temperatures the humidity is

computed.

7 Tachometers / Stroboscopes: In any audit exercise speed measurements of for example

motors are critical as they may change with frequency, belt slip and loading. There are two

main types of speed measurement instruments: the tachometer and the stroboscope.

Tachometer

Stroboscope

A simple tachometer is a contact type instrument, which can be

used to measure speeds where direct access is possible.

Sophisticated and safer instruments to measure speed are non-

contact instruments, such as stroboscopes. A stroboscope is a

source of flashing light that can be synchronized with any fast,

repetitive motion so that a rapidly moving device seems to stand

still, or to move slowly.


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8 Leak detector: As the name implies, ultrasonic leak detectors detect the ultrasonic sound of a

leak. You are probably familiar with the hissing sound a large leak makes. Smaller leaks also

emit a sound, however the frequency is too high for our ears to detect it. An ultrasonic leak

detector transforms the ultrasonic hissing sound to a sound that humans can hear, and thus

leads to the source of the leak. Basically it is used for detecting the leak of compressed air,

pneumatic system. Compressed air is one of the most expensive energy used in industries.

Leak Detector

Ultrasonic leak detectors are used to detect leaks of compressed

air and other gases which are normally not possible to detect

with the human ear. No leak detector will find every leak, every

time. It is often a combination of several available methods

which will insure the highest rate of success.

9 Lux Meter: Lux meters are used to measure illumination levels in offices, factories etc. most

of lux meter consists of a body, a sensor with a photo cell, and display panel. The sensor is

placed under the light source. The light that falls on the photo cell has energy, which is

transferred by the photo cell into electric current. The more light is absorbed by cell, the higher

the generated current. The meter reads the electrical current and calculates the approx. value of

either Lux or Foot candles. This is shown in display panel.

Lux Meter

A light sensitive cell measures the incident light and evaluates

that against the human daylight sensitivity curve. The resulting

value is the measurement result in lux. This works well but it

requires a different correction factor for every light spectrum.

10 Thermography: It is an instrument which is used to measure thermal energy radiation from

hot/cold surfaces of an object and provides input for assessing health of equipment and

predictive maintenance. This is remarkable instruments creates pictures of heat. They measure

infrared (IR) energy and convert the data to images corresponding to the temperature.

Thermal Imager

It consists thermal camera unit converts electromagnetic thermal

energy radiated from an object into electronic video signals.

These signals are amplified and transmitted via interconnected

cable to a display monitor where the resulting image is analyzed

and interpreted for hot/cold spots

11 Smart Energy Meter: It is an instrument which is referred to electric meter which keep

detailed statistics on usage, but it can be used for fuels or water applications as well performing

the same job.

Smart Energy Meter

Primary purpose of it is to provide information on how end users

use their electricity on a real-time basis. It helps to track the

electricity consumption and thus save both electricity and

money. It is advanced metering unit which can be controlled via

mobile or internet.


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2. ENERGY EFFICIENCY OF INDUSTRIAL UTILITIES

2.1 BOILERS

A Boiler is an enclosed vessel that provides a means for combustion heat to be transferred to water unit

it becomes heated water or steam. The hot water or steam under pressure is then usable for transferring

the heat to a process. Water is a useful and inexpensive medium for transferring heat to a process. When

water at atmospheric pressure is boiled into steam its volume increases about 1,600 times, producing a

force that is almost as explosive as gunpowder. This causes the boiler to be equipment that must be

treated with utmost care.

Fuel

2.1.1 Objectives of Boiler performance Assessment

Objective of boiler performance assessment is to know how about condition of boiler using in industry

and documentation of improvement loophole opportunities of boiler through the calculation of

following headings.

Find out Boiler efficiency

Find out the evaporative ratio

Know about Fuel consumption scenario

2.1.2 Performance Evaluation of Boiler

The boiler efficiency and evaporation ratio reduces with time due to following causes:

1. Poor combustion

2. Heat transfer fouling

3. Poor operation and maintenance

4. Fuel quality

5. Water quality

So Energy/ heat balance helps us to identify avoidable and unavoidable heat losses. Boiler efficiency

tests help us to find out the deviation of boiler efficiency from the best efficiency and target problem

area for corrective action. Boiler combustion process can be described in the form of an energy flow

The boiler system comprises of: a

feed water system, steam system and

fuel system. The feed water system

provides water to the boiler and

regulates it automatically to meet the

steam demand. Various valves

provide access for maintenance and

repair. The steam system collects and

controls the steam produced in the

boiler. Steam is directed through a

piping system to the point of use.

Throughout the system, steam

pressure is regulated using valves

and checked with steam pressure

gauges. The fuel system includes all

equipment used to provide fuel to

generate the necessary heat. The

equipment required in the fuel

system depends on the type of fuel

used in the system.

Softeners

Boiler

Water

Deaertor

Vent

Pumps

Stack

Exhaust gas

Steam to

Process

Fuel

Chemical feed

Economizer

Blow Down

Separator

Vent

Fig: Schematic diagram of a Boiler Room


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diagram. Meanwhile steam is generated from fuel it is transformed into various heat and energy losses

which is shown in fig below.

Fig: Energy balance Diagram of a Boiler

The heat balance is an attempt to balance the total energy entering a boiler against that leaving the boiler

in different forms. Basically energy losses can be divided into unavoidable and avoidable losses (excess

air, stack gas temperature, blow down, condensate, convection and radiation). Only avoidable energy

losses must be reduced.

Fig: Typical Losses from Coal Fired Boiler (Reference: UNEP)

2.1.3 Energy Efficiency Opportunities in Boiler

Energy efficiency opportunities related to combustion, heat transfer, avoidable losses, auxiliary power

consumption, water quality and blow down. The various energy efficiency opportunities in a boiler

system can be related to:

1) Stack temperature control

2) Feed water preheating using economizers

3) Combustion air pre-heating

4) Excess air control

5) Radiation and convection heat loss avoidance

6) Incomplete combustion minimization

7) Reduction of scaling and soot losses

8) Automatic blow down control

9) Reduction of boiler steam pressure

Heat loss due to moisture in fuel

Heat loss due to moisture in air

Heat loss due to unburnts in residue

Heat loss due to radiation & other

unaccounted losses

Heat in Steam

Heat loss due to dry flue gas

Heat loss due to steam in flue gas

12.7 %

1.0 %

73.8 %

1.7 %

8.1 %

0.3 %

2.4 %

Fuel 100 %

BOILER

Ash

and

Un

bu

rnt

part o

f fuel in

ash

Blo

w D

ow

n

Co

nvectio

n &

Rad

iation

Steam Output Fuel Input 100% + Air

Stack Gas + Unburnt Air


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10) Proper boiler scheduling

Definitely, above opportunities help us to reduce the losses of boiler for enhancing the efficiency of

boiler.

2.1.4 Boiler Efficiency

Boiler efficiency is defined as “percentage of energy heat) input that is effectively useful in the

generated steam.”

There are two methods of assessing boiler efficiency:

1) The Direct Method: the energy gain of the working fluid (water and steam) is compared with the

energy content of the boiler fuel.

2) The Indirect Method: the efficiency is the difference between the losses and the energy input

1) The Direct Method Testing

This is simply input output method due to the fact that it needs only the useful output (steam) and the

heat input (fuel) for evaluating the efficiency.

Boiler Efficiency η) =

100 &

=

100

= ( – )

Example

Find out the efficiency of boiler by direct method with the data given below:

Type of boiler: Coal fired

Quantity of steam (dry) generated: 14 TPH

Steam pressure (gauge) / temp: kg cm g) C

Quantity of coal consumed: 2.75 TPH

Feed water temperature: C

GCV of coal: 4000 kcal/kg

Enthalpy of steam at 10 kg/cm2 pressure: 665 kcal/kg (saturated)

Enthalpy of feed water: 85 kcal/kg

Calculation

Boiler Efficiency η) =

100 = 73.81 %

Evaporation Ratio = 14 Tonne of steam/ 2.75 Tonne of coal = 5.09

2) Indirect Method Testing The efficiency can be measured easily by measuring all the losses occurring in the boilers. The

disadvantages of direct method can be overcome by this method, which calculates the various heat

losses associated with boiler.

Boiler Flue gas

Steam Output

Efficiency = 100 – (i + ii + iii + iv + v + vi + vii)

Air

Fuel Input, 100%

i. Dry Flue gas loss

ii. H2 loss

iii. Moisture in fuel

iv. Moisture in air

v. Fly ash loss

vii. Surface loss

vi. Unborn fuel loss


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Methodology

The reference standards for Boiler Testing at Site using the indirect method are the British Standard, BS

845:1987 and the USA Standard ASME PTC-4-1 Power Test Code Steam

Generating Units

The indirect method is also called the heat loss method. The efficiency can be calculated by subtracting

the heat loss fractions from 100 as follows:

Efficiency of boiler (n) = 100 - (i + ii + iii + iv + v + vi + vii)

Whereby the principle losses that occur in a boiler are loss of heat due to:

I. Dry flue gas

II. Evaporation of water formed due to H2 in fuel

III. Evaporation of moisture in fuel

IV. Moisture present in combustion air

V. Unburnt fuel in fly ash

VI. Unburnt fuel in bottom ash

VII. Radiation and other unaccounted losses

Losses due to moisture in fuel and due to combustion of hydrogen are dependent on the fuel, and cannot

be controlled by design.

The data required for calculation of boiler efficiency using the indirect method are:

Ultimate analysis of fuel (H2, O2, S, C, moisture content, ash content)

Percentage of oxygen or CO2 in the flue gas

Flue gas temperature in C f)

Ambient temperature in C a) and humidity of air in kg kg of dry air

GCV of fuel in kcal/kg

Percentage combustible in ash (in case of solid fuels)

GCV of ash in kcal/kg (in case of solid fuels)

A detailed procedure for calculating boiler efficiency using the indirect method is given below.

However, practicing energy managers in industry usually prefer simpler calculation procedures.

Step 1: Calculate the theoretical air requirement

= [(11.43 x C) + {34.5 x (H2 – O2/8)} + (4.32 x S)]/100 kg/kg of fuel

Step 2: Calculate the percent excess air supplied (EA)

Step 3: Calculate actual mass of air supplied/ kg of fuel (AAS)

= {1 + EA/100} x theoretical air

Step 4: Estimate all heat losses

i. Percentage heat loss due to dry flue gas

=

Where,

m = mass of dry flue gas in kg/kg of fuel

m = (mass of dry products of combustion / kg of fuel) + (mass of N2 in fuel on 1 kg basis) + (mass of

N2 in actual mass of air we are supplying).

Cp = Specific heat of flue gas (0.23 kcal/kg )


17

ii. Percentage heat loss due to evaporation of water formed due to H2 in fuel

=

Where, H2 = percentage of H2 in 1 kg of fuel

Cp = specific heat of superheated steam (0.45 kcal/kg)

iii. Percentage heat loss due to evaporation of moisture present in fuel

Where,

M = Percent moisture in 1kg of fuel

Cp = Specific heat of superheated steam (0.45 kcal/kg)

iv. Percentage heat loss due to moisture present in air

=

Where,

Cp = Specific heat of superheated steam (0.45 kcal/kg)

v. Percentage heat loss due to unburnt fuel in fly ash

=

vi. Percentage heat loss due to unburnt fuel in bottom ash

=

vii. Percentage heat loss due to radiation and other unaccounted loss

The actual radiation and convection losses are difficult to assess because of particular emissivity

of various surfaces, its inclination, airflow patterns etc. In a relatively small boiler, with a capacity of 10

MW, the radiation and unaccounted losses could amount to between 1 percent and 2 percent of the gross

calorific value of the fuel, while in a 500 MW boiler, values between 0.2 percent to 1 percent are

typical. The loss may be assumed appropriately depending on the surface condition.

Step 5: Calculate boiler efficiency and boiler evaporation ratio


Evaporation Ratio = Heat utilized for steam generation/Heat addition to the steam

Evaporation ratio means kilogram of steam generated per kilogram of fuel consumed. Typical

Examples are:

Coal fired boiler: 5 (i.e. 1 kg of coal can generate 5 kg of steam)

Oil fired boiler: 13 (i.e. 1 kg of oil can generate 13 kg of steam)

However, the evaporation ratio will depend upon type of boiler, calorific value of the fuel and

associated efficiencies.

Example

The soap manufacture company uses the oil fire boiler, from the data measurement following data are

collected, calculate the boiler efficiency and evaporative ratio.


18

Type of boiler: Oil fired

Ultimate analysis of Oil

C: 84 %

H2: 12.0 %

S: 3.0 %

O2: 1 %

GCV of Oil: 10200 kcal/kg

% of O2 in flue gas by volume: 7%

% of CO2 in flue gas by volume: 11 %

Flue gas temperature (Tf): 220C

Ambient temperature (Ta): 27 C

Humidity of air : 0.018 kg/kg of dry air

Step-1: Calculate the theoretical air requirement

= [(11.43 x C) + [{34.5 x (H2 – O2/8)} + (4.32 x S)]/100 kg/kg of oil

= [(11.43 x 84) + [{34.5 x (12 – 1/8)} + (4.32 x 3)]/100 kg/kg of oil

= 13.82 kg of air/kg of oil

Step-2: Calculate the percent excess air supplied (EA)

Excess air supplied (EA)

= (O2 x 100)/(21-O2)

= (7 x 100)/(21-7)

= 50 %

Step 3: Calculate actual mass of air supplied/ kg of fuel (AAS)

AAS/kg fuel = [1 + EA/100] x Theo. Air (AAS)

= [1 + 50/100] x 13.82

= 1.5 x 13.82

= 20.74 kg of air/kg of oil

Step 4: Estimate all heat losses

i. Percentage heat loss due to dry flue gas

=

m = mass of CO2 + mass of SO2 + mass of N2 + mass of O2

0.84 x 44 0.03 x 64 20.74 x 77

m = ------------- +---- ---------- + --------------- (0.07 x 32)

12 32 100

m = 21.35 kg / kg of oil

21.35 x 0.23 x (220 – 27)

= ------------------------------- x 100

10200

= 9.29 percent

A simpler method can also be used: Percentage heat loss due to dry flue gas

=

m (total mass of flue gas) = mass of actual air supplied + mass of fuel supplied

= 20.19 + 1 = 21.19

21.19 x 0.23 x (220-27)

= ------------------------------- x 100

10200

= 9.22 %


19

ii. Heat loss due to evaporation of water formed due to H2 in fuel

=

where H2 = percentage of H2 in fuel

9 x 12 {584+0.45(220-27)}

= -------------------------------- =7.10%

10200

iii. Heat loss due to moisture present in air

=

= [20.74 x 0.018 x 0.45 x (220-27) x 100]/10200

= 0.317%

iv. Heat loss due to radiation and other unaccounted losses

For a small boiler it is estimated to be 2 percent

Step 5: Calculate boiler efficiency and boiler evaporation ratio


I. Heat loss due to dry flue gas : 9.29 percent

II. Heat loss due to evaporation of water formed due to H2 in fuel : 7.10 percent

III. Heat loss due to moisture present in air : 0.317 percent

IV. Heat loss due to radiation and other unaccounted losses : 2 percent

= 100- [9.29+7.10+0.317+2]

= 100 –18.421 = 81.58 % (approximate)

Evaporation Ratio = Heat utilized for steam generation/Heat addition to the steam

= 10200 x 0.83 / (660-60)

= 14.11 (compared to 13 for a typical oil fired boiler)

2.1.5 Findings

According to research, approximately 15% to 20% fuel consumption can be saved if

economizer used properly.

Approximately 26.2 % of heat losses in boiler while working condition in different headings.

Only 73.8 % of heat converts into steam.

Heat loss due to dry flue gas and heat loss due to steam in flue gas contributes highest degree of

losses in boiler operation.

Superheater can be used to increase temperature at constant pressure which access to maximize

the efficiency of boiler.

2.1.6 Recommendation

Here is an additional option which helps to improve efficiency and evaporation ratio of boiler:

Periodic tasks and checks outside of the boiler

Extra items for steam raising and hot water boilers

Boiler rooms and plant rooms ventilation should be proper for ventilation

Feed water always should be treated by chemical

Blow down (BD) procedure always applied while blow down

Always obey the SOP while operating boiler


20

2.2 FURNACE

A furnace is equipment used to melt metals for casting or to heat materials to change shape or

properties. Basically, furnace is device used to heat the materials.

2.2.1 Objectives of Furnace Performance Assessment

Objectives of furnace performance assessment are to find out the condition of furnace and energy

opportunities of furnace through following headings:

Find out various losses in furnace Find out the heat balance of furnace

Find out the efficiency of the furnace Find out the specific energy consumption

2.2.2 Performance Evaluation of Furnace

Due to the following causes efficiency and specific energy consumption of furnace is decreased with

time.

Provide low efficiency.

o Heat lost via exhaust gases

o Moisture and Hydrogen in fuel

o Heat loss via furnace walls and hearth

o Heat loss via radiation and convection from outer surface of wall

o Heat loss through gases leaking via cracks, opening of doors

Evaluating the furnace efficiency can be calculated from heat balance. Its efficiency can be calculated

after subtracting sensible heat loss in flue gas, heat loss due to opening of door, loss due to moisture in

flue gas, and other unaccounted losses from the heat input to the furnace.

Fig: Heat losses in Fuel Fired Furnace (Source: BEE)

Exhaust gas flue

Furnace

Chamber

Burner

Discharge

Door

Hearth Stock Charge

Door Fig: Industrial Heating Furnace

In furnace, flue gases come from

direct contact with the materials,

suitable fuel chosen is important. For

example, some materials will not

tolerate sulphur in the fuel. Solid

fuels generate particulate matter,

which will interfere the materials

placed inside the furnace, proper fuel

selection play vital role in every

aspect even in efficiency and specific

energy consumption.

Fuel Input 100% Useful heat in stock

(30-50%)

Wall lo

ss (3 -1

0 %

)

Flue lo

ss

20

-50

%

Op

enin

g loss

(1-2

%)

Co

olin

g loss (5

-

10

%)

Stored

heat (2

-

5 %

)

Oth

er

loss

Recycled heat (10-30%)

Furnace


21

There are many loopholes for heat losses of furnace so should be reduced to enhance the efficiency of

furnace.

2.2.3 Energy Efficiency Opportunities

There is various energy saving opportunities in furnaces. Typical energy efficiency measures for an

industry with furnace are:

1. Minimum refractory losses 2. Operation at the optimum furnace

temperature

3 Proper heat distribution 4. Reducing heat losses from furnace openings

5 Complete combustion with minimum excess air 6. Maintaining correct amount of furnace draft

7 Waste heat recovery from the flue gases 8. Selecting the right refractories

9 Optimum capacity utilization 10. Use of ceramic coatings

If above activities are clearly addressed in furnace operation, definitely efficiency of furnace can be

improved. Definitely, above opportunities help us to reduce the losses of furnace for enhancing the

efficiency of furnace.

2.2.4 Furnace Efficiency

A furnace’s efficiency increases when the percentage of heat that is transferred to the stock. he

efficiency of furnace is the ratio of useful heat output to heat input. The efficiency of the furnace can be

calculated in two ways; direct method and indirect method.

1) Direct Method:

The quantity of heat (Q) that will be transferred to stock can be calculated with this equation:

Q = m x Cp Δ i.e Δ =(t1

– t2)

Where, Q = Quantity of heat of stock in kCal

m = Weight of the stock in kg Cp= Mean specific heat of stock in kCal/kg

t1= Final temperature of stock in

t2= Initial temperature of the stock before it enters the furnace in

Example:

Suppose, A steel industry is using the continuous reheating furnace; heat input is 435 liters per hour.

The specific gravity of fuel is used to convert this into kg.

Therefore: 435 l/hr x 0.92 kg/l = 400 kg/hr, t1 = 1540

o

C & t2 = 37

o

C

The heat output is calculated as follows:

Q = m x Cp x Δ

= 6000 kg x 0.12 x (1540 – 37)

= 1082160 kCal

The efficiency is:

= (heat output / heat input) x 100

= [(1082160 / (400 x 10000)] x 100 = 27.054 %

The approximate heat loss is 100% – 27.054% = 72.946%

2) Indirect Method:

Calculate the efficiency of an oil-fired reheating furnace with the direct and indirect method using the data

below.

Operating temperature: 1340

Exit flue gas temperature after preheater: 750

Ambient temperature: 40


22

Preheated air temperature: 190

Specific gravity of fuel oil: 0.92

Average fuel oil consumption: 400 liters / hr = 400 x 0.92 =368 kg/hr

Calorific value of oil: 10000 kCal/kg

Average O2 percentage in flue gas: 12 %

Moisture in 1 kg of fuel oil: 0.15 kg

H2 in 1 kg of fuel oil: 0.1123 kg

Theoretical air required to burn 1 kg of oil: 14 kg

Weight of stock: 6000 kg/hr

Specific heat of billet: 0.12 kCal/kg/

Furnace wall thickness (D): 460 mm

Billet extraction outlet (X): 1 m x 1 m

Average surface temperature of heating + soaking zone: 122

Area of heating + soaking zone: 70.18 m2

Area other than heating and soaking zone: 12.6 m2

Average surface temperature of area other than heating and soaking zone: 80

The different heat losses are calculated below.

a) Heat loss in flue gas

= 12 / (21 – 12)

= 133 %

Mass of air supplied

= (1 + EA/100) x Theoretical air

= (1+ 1.13) x 14

= 32.62 kg/kg fuel oil

Mass of air supplied

= (1 + EA/100) x Theoretical air

= (1+ 1.13) x 14

= 32.62 kg/kg fuel oil

% Heat loss in flue gas =

Where,

m = weight of flue gas (air + fuel) = 32.62 + 1.0 = 33.62 kg/kg oil

Cp = specific heat

Δ = temperature difference

% Heat loss = {33.62 x 0.24 x (750 – 40)} x 100 = 57.29%

10000

b) Heat loss from moisture in fuel

% heat loss from moisture in fuel =

Where,

M = kg of moisture in 1 kg of fuel oil

f = Flue gas temperature C

amb= Ambient temperature C

GCV = Gross Calorific Value of fuel, kCal/kg

% Heat loss = 0.15 x {584 + 0.45 (750 – 40)} x 100 = 1.36%

10000


23

c) Loss due to hydrogen in fuel

Where,

H2 = kg of H

2 in 1 kg of fuel oil (= 0.1123 kg/kg of fuel oil)

% Heat loss = 9 x 0.1123 x {584 + 0.45 (750 – 40)} x 100 = 9.13%

10000

d) Heat loss due to openings in furnace

The factor of radiation through openings and the black body radiation factor can be obtained from standard

graphs.

Factor of radiation = 0.71

Black body radiation at 1340 0

C = 36 kCal/kg/cm2/hr

The area of the opening is 100 cm x 100 cm = 10000 cm2

Emissivity = 0.8

% Heat loss from furnace openings = 36 x 0.8 x 0.71 x 10000 x 100 = 5.56%

368 x 10000

e) Heat loss through furnace skin

To determine the heat loss through the furnace skin, first the heat loss through the roof and sidewalls and

through other areas must be calculated separately.

i). Heat loss through roof/ceiling and sidewalls (= heating and soaking zone):

Total average surface temperature = 122o

C

Heat loss at 122o

C (Refer Figure 14) = 1252 kCal /m2

hr

Total area of heating + soaking zone = 70.18 m2

Total heat loss i = 1252 kCal / m2

hr x 70.18 m2

= 87865 kCal/hr

ii) Heat lost from area other than heating and soaking zone

Total average surface temperature = 80 C

Heat loss at 80o

C (Refer Figure 14) = 740 kCal / m2

hr

Total area = 12.6 m2

Total heat loss ii = 740 kCal / m2

hr x 12.6 m2

= 9324 kCal/hr


24

% Heat loss through furnace skin = (87865 kCal/hr + 9324 kCal/hr) x 100 = 2.64%

10000 kCal/kg x 368 kg/hr

f) Unaccounted losses

The unaccounted losses cannot be calculated unless the other types of losses are known.

Furnace efficiency

Adding the losses gives the total losses:

a) Flue gas loss = 57.29 %

b) Loss due to moisture in fuel = 1.36 %

c) Loss due to H2 in fuel = 9.13 %

d) Loss due to openings in furnace = 5.56 %

e) Loss through furnace skin = 2.64 %

Total losses = (57.29+1.36+9.13+5.56+2.64) = 75.98 %

The furnace efficiency calculated through the indirect method = 100 – 75.98 = 24.02%

2.2.5 Findings

Only the 30-50% of energy is converted into usable heat.

Heat loss due to flue gas is utmost losses; 20-50% loss contributes by flue gas loss.

If proper insulation is used 3-7% of wall loss can be reduced.

Calorific value of furnace oil should be high regarding fuel cost

2.2.6 Recommendations

It is difficult to make a recommendation of general options for furnaces, because options to improve

energy efficiency vary between furnaces. But the main options that are applicable to most furnaces are:

Monitor O2 /CO2/CO and control excess air to the optimum level

Check against infiltration of air: use doors or air curtains

Retrofit with heat recovery device

Investigate cycle times and reduce

Provide temperature controllers

Ensure that flame does not touch the stock

Improve burner design, combustion control and instrumentation

Ensure that the furnace combustion chamber is under slight positive pressure

Use ceramic fibers in the case of batch operations

Match the load to the furnace capacity


25

2.3 ELECTRIC MOTORS AND VARIABLE DRIVES

An electric motor is an electromechanical device that converts electrical energy to mechanical energy.

Generally, electric motors are used in most industrial systems where mechanical energy is needed. It

converts electrical energy into rotary mechanical energy. This then is further converted to finally

provide the needed use-energy. That means it is ever one of the important component using in industries

to develop motion. Electric motors are sometime called “Inductive load” of industry because of it needs

some of the power which comes down the supply line temporarily to create magnetic field and

sometimes called the “work horses” of industry because it is estimated that motors use about % of the

total electrical load in industry. So that there are two important parameters one is efficiency and other is

power factor that should be addressed while executing energy audit of electric motors.

Inside industry, needed different mechanical energy for different works which is provided via electrical

motors that consumed more than 70 % of electric energy in different headings which is expressed in

above pie chart. If minimum-minimum amount of losses occurred in every headings become huge losses

in the whole electricity consumption which is unnecessary overhead of electricity consumption. But

proper utilization of different systems can be minimized the unnecessary electricity consumption.

2.3.1 Objectives of performance assessment of Electric motor and its drive

Only the objectives to electric motor assessment is to know how the condition of motors and motor

related devices and its energy consumption through following tests.

Efficiency test

No Load test

Stator and Rotor losses

Stray load losses

Motor Loading

Input power measurement

Line current measurement

Slip method

2.3.2 Energy Efficiency opportunities

There are several loophole or factors affecting electric motor performance, minimization of all these

factors may be the potential opportunities for energy efficiency of electric motors.

1 Reduce under-loading (and avoid over-sized motors) 2 Sizing to variable load

3 Replace standard motors with energy efficient motors 4 Rewinding

5 Power factor correction by installing capacitors 6 Improving maintenance

7 Reduce the under load condition 8 Improving power quality

9 Speed control of induction motor

Fig: Induction Motor

Fig: Share of different motor systems of total

electricity use by Industrial motor system


26

a) Multi-speed motors

b) Variable speed drives (VSDs)

c) Direct current drives (DC)

d) Wound rotor AC motor drives (slip ring induction motors)

There are different kinds of losses occurred in motor operation which is shown in below figure

Types of Losses in an Induction Motor (Source: Bureau of Energy Efficiency (BEE) India, 2004)

2.3.3 Terminology and definition

a) Motor speed The speed of a motor is the number of revolution in a given time frame, typically revolution per

minute (RPM). The speed of an AC motor depends on frequency of input power and the number of

poles for which the motor is wound,

The actual speed, with which the motor operates, will be less than the synchronous speed. The

difference between synchronous and full load speed is called slip and is measured in percent.

As part relation stated above, the speed of an AC motor is determined by the number of motor poles

and by the input frequency.

b) Power Factor

Power factor is relevant to AC transmission is given as: Cos𝞥 =

=

As the load on the motor comes down the magnitude of the active current reduces. However, there

is no corresponding reduction in the magnetizing current, which is proportional to supply voltage

with the result that the motor power factor reduces, with a reduction in applied load. Induction

motor, especially those operating below their rated capacity, is the main reason for low power factor

in electric system.

Reactive Power (KVAr) Total or real power (KVA)

Active Power (KW)


27

2.3.4 Assessment of Electric Motors

Efficiency of Eclectic Motor Testing

While input power measurements are fairly simple, measurement of output or losses need a laborious

exercise with extensive testing facilities. The following are the testing standards of widely used.

a) Field tests for Determining Efficiency

Efficiency of motor (𝜂) =

=

Where, Pout = Output power of the motor

Pin = Input power of the motor

P loss =Losses occurring in motor

Various losses in the motor are determined as follows:

No load Test:

The motor is run at rated voltage and frequency without any shaft load. Input power,

current, frequency and voltage are noted. The no load P.F is quite low and hence low PF

watt meters are required. From the input power, stator I2R losses under no load are

subtracted to give the sump of friction and windage (F&W) and core losses. To separate

core and F&W losses, test is repeated at variable voltages

Core losses =

Stator and Rotor I2 R losses:

The stator winding resistance is directly measured by a bridge or volt amp method. The

resistance must be corrected to the operating temperature. Tor modern motors, the operating

temperature is likely to be in the range of 100 to 120 and necessary correction should

be made. Correction to 75 may be inaccurate. The correction factor is given as follows:

=

Where, t1= ambient temperature t2= operating temperature

The rotor resistance can be determined from locked rotor test at reduced frequency, but

rotor I2R losses are measured from measurement of rotor slip.

Stary load loss:

These losses are difficult ot measure with any accuracy. IEEE satandard 112 gives a

complicated method, which is rarely used on shop floor. IS and IEC standards take a fixed

value as 0.5% of output. It must be remarked that actual value of stray losses is likely to be

more. IEEE-112 specifies values from 0.9 to 1.8%.

Motor Rating Stary Losses

1-125 HP 1.8%

126-500HP 1.5%

501-2499HP 1.2%

25000 and above 0.9%

b) Determining Motor Loading Input power measurements:

Step 1: Determine the input power using the following equation:

Pi =

Where,

Pi = Three phase power in kW I = RMS current, mean of 3 phases


28

V = RMS voltage, mean line to line of 3 phases PF = Power factor as a decimal

Step 2: Determine the rated power by taking the nameplate value or by using the following

equation:

Where,

Pr = Input power at full-rated load in kW HP = Nameplate rated horse power

𝜂r = Efficiency at full-rated load (name plate value or from motor efficiency tables)

Step 3: Determine the percentage load using the following equation:

Where,

Pr = Input power at full-rated load in kW Pi = Measured three phase power in kW

Load = Output power as a % of rated power

Example

The following power measurement observations were made for a 50 kW three phase induction

motor with 85% full load efficiency.

V = 420 Volt

I =32 Amp

PF = 0.87

Calculate the load

Calculation:

Input Power = (1.732 x 420 x 32 x 0.87)/1000 = 20.25 kW

% Loading = [20.25 /(50/0.85)] x 100 = 34.425 %

2.3.5 Findings

About 70% of electricity is consumed by only motor for different purpose.

As much as possible don’t use re-winded motor which efficiency is decreased under the 50 % to

60% efficiency if re-winding is carried out.

Always maintain PF more than 0.9 which saved the electric cost.

Stator loss is the main potential loss source which contributes 34% loss out of 7.6 % power loss


Here is a list of most important energy efficiency options for electric motors.

Maintain supply voltage level with a maximum deviation of 5% from the nameplate value.

Minimize phase unbalance within 1% to avoid derating of the motor.

Maintain high power factor by installing capacitors as close to the motor as possible

Select proper motor size to avoid inefficiencies and poor power factor

Use variable speed drives (VSD) or two-speed systems wherever applicable

Replace oversized, undersized and failed motors with energy efficiency motors

Get burnt out motors rewound by a qualified expert

Optimize transmission efficiency by proper installation and maintenance of shafts, belts, chains,

and gears

Control the ambient temperature to maximize insulation life and motor reliability, e.g. by

avoiding exposure to the sun, locating them in well-ventilated areas, and keeping them clean

Lubricate the motor according to manufacturers’ specifications and apply high-quality greases

or oils to prevent contamination with dirt or water.


29

2.4 PUMPS & PUMPING SYSTEM

Pump is the device that helps to transport the fluid from one point to another, transporting system called

pumping system is the process of addition of kinetic and potential energy to a liquid for the purpose of

moving it from one point to another. Basically under the Dynamic, positive displacement and others

types of pumps there are different kind of pumps are using in industry to transport. According to the US

DOE, survey on 4 pumping systems account for nearly % of the world’s electrical energy

demand and range from 25 – 50 % of the energy usage in certain industrial plant operation. Basically

installation of pumps in industry is two purposes for:

Transport of liquid from one point to another place

Circulate liquid around the system

Fig: Centrifugal pump Fig: Pump operating pint

Matching of the pumps to load plays the critical role for energy efficiency in pumping system. Wrong

selection of pumps and deposition in impellers decreases efficiency of pumps. Hence performance

assessment of pumps and pumping system should be done in order to take corrective action.

2.4.1 Objectives of Performance Assessment

Energy audit may help to determine the efficiency of pump during operating condition and saving of

unwanted overhead of pumping system. Not only this much it also helps to determine the system

resistance and operating duty point of the pump and compare the same with design.

2.4.2 Terms and Definition

Pump Capacity, Q = Volume of liquid delivered by pump per unit time, m3/hr or m3/sec. Q is

proportional to rotational speed of the pump

Total developed head, H = the difference of discharge and suction pressure. The pump head represents

the net work done on unit weights of a liquid in passing from inlet of the pump to the discharge of the

pump. There are two heads in common use in pumps namely:

1. Static head = difference in height between source and destination of the liquid

2. Friction head = this is loss due to friction in pipes, valves and fitting, joints varies as function of

capacity flow through the system.

System resistance: the sum of frictional head in resistance and total static head

Pump performance

curve Pump

operating point

System curve

Head

Flow

Static head


30

Pump Efficiency: Fluid power and useful work done by the pump divided by the power input in the

shaft.

2.4.3 Energy Efficiency Opportunities of pump and pumping system

There are several main areas for improving pumps and pumping systems efficiency and its energy

conservation. The main areas for energy conservation include:

1. Selecting the right pump 2. Controlling the flow rate by speed variation

2.1 Explaining the effect of speed

2.2 Using variable speed drive (VSD)

3. Pumps in parallel to meet varying demand 4. Eliminating flow control valve

4. Eliminating by-pass control 6. Start/stop control of pump

7. Impeller trimming

If the industry followed and addressed the above significant area for improving the pumping system and

Its efficiency. Finally, increases the machine productivity and decreases unnecessary energy

consumption

2.4.4 Difficulties of pumps assessment

In practice, it is more difficult to assess pump performance. Some important reasons are:

Absence of pump specification data

Difficulty in flow measurement

Improper calibration of pressure gauges and measuring instruments

2.4.5 Assessment of Pumps

The work performed by a pump is a function of the total head and of the weight of the liquid pumped in

a given time period. Pump shaft power (Ps) is the actual horsepower delivered to the pump shaft, and

can be calculated as follows:

=

Pump output, water horsepower or hydraulic horsepower (hp) is the liquid horsepower delivered by the

pump, and can be calculated as follows:

Where,

Q = flow rate (m3/sec) hd = discharge head (m)

hs = suction head (m) ρ = density of the fluid kg m3)

g = acceleration due to gravity (m/s2)

Example

A personal care industry operates a cooling water pump for process cooling and refrigeration

applications. During the performance testing the following operating parameters were measured.

Measured Data:

Pump flow (Q) = 0.52 m3/sec Power absorbed (P) = 380 kW

Suction head (tower basin level, h1) = +1 m Delivery head (h2) = 60 m

Height of cooling tower = 5 m Motor efficiency = 87 %

Type of drive = Direct coupled Density of water = 996 kg/m3


31

Solution

= 299.76 kW

𝜂

= 78.89 %

2.4.6 Findings

Almost 20% of electricity energy accounted out of world’s electrical energy demand and range

from 25 – 50 % of the energy usage in certain industrial plant operation. Fitting and bending are played vital role in pumping system losses.

Always addressed static loss and frictional loss that played vital role in efficiency.

For industrial purpose, most of the industry uses centrifugal pumps.

Selection of pumps depends upon requirement of quantity flow/hr.

2.4.7 Recommendations

Here is additional option to improve energy efficiency of pumps and pumping systems.

Operate pumps near their best efficiency point (BEP)

Ensure adequate Net positive suction head (NPSH) at site of installation

Modify pumping system and pumps losses to minimize throttling.

Ensure availability of basic instruments at pumps like pressure gauges, flow meters

Adapt to wide load variation with variable speed drives or sequenced control of multiple units

Avoid operating more than one pump for the same application

Use booster pumps for small loads requiring higher pressures

To improve the performance of heat exchangers, reduce the difference in temperature between

the inlet and outlet rather than increasing the flow rate

Repair seals and packing to minimize water loss by dripping

Balance the system to minimize flows and reduce pump power requirements

Avoid pumping head with a free-fall return (gravity), and use the siphon effect

Conduct a water balance to minimize water consumption, thus optimum pump operation

Avoid cooling water re-circulation in DG sets, air compressors, refrigeration systems, cooling

towers feed water pumps, condenser pumps and process pumps

In multiple pump operations, carefully combine the operation of pumps to avoid throttling

Replace old pumps with energy efficient pumps

T improve the efficiency of oversized pumps, install variable speed drive, downsize /replace

impeller, or replace with a smaller pump

Optimize the number of stages in multi-stage pump if margins in pressure exist

Reduce the system resistance by pressure drop assessment and pipe size optimization


32

2.5 COMPRESSOR AND COMPRESSED AIR SYSTEM

Most of the industrial plants are using compressed air throughout their production operation which is

produced by compressed air units ranging from 5 to over 50000 hp. So compressed air system is not

only an energy intensive utility but also one of the least energy efficient but compressed air is most

expensive energy source using in industries. Due to different causes like poor maintenance, wear and

tear etc. efficiency of compressed air drastically reduces with period of time. So a periodic performance

assessment is essential to minimize the cost of compressed air.

Fig: Cost components in a typical compressed air system (eCompressed Air)

From this above figure, only the minimum amount of energy is used for end use, most of the energy

converts into heat loss and there are many loopholes for effective cost saving.

2.5.1 Objectives of Compressor Performance Assessment

Objectives of compressor performance assessment are to identify about condition of compressor using

in industry and find out the potential opportunities of compressor and compressed air system.

Find out Volumetric efficiency

Find out Specific power requirement

Find out Actual Free Air Delivery (FAD) of compressor

Find out Isothermal power required

Find out compression ratio

The actual performance of the plant is to be compared with design/standard values for assessing the

plant energy efficiency. Under the Dynamic and positive displacement type of compressor there are

various types of compressor and different compressor performance opportunities.

Electricity

consumed by

compressor

Simple, cost effective measures 30% savings (Generation, Treatment, Distribution, Misuse)

Heat loss

Delivered compressed

air 10% approx..

Fig: Shauky Diagram for Compressed Air system (Source: Mckane and Medaris, 2003)


33


There are different opportunities which may be the potential insight strength for the minimization of

losses in Compressor and Compressed air system which are as follows:

1. Location of Compressor 2. Air Intake Temperature

3. Pressure drops in Air Filter 4. Elevation

5. Inter and after coolers 6. Pressure Setting

7. Minimizing leakage 8. Condensate Removal

9. Controlled Usage of Compressed 10.Compressor Controlled

11. Maintenance Practices

Strictly addressed the above opportunities, the efficiency of compressor and its air system can be

improved.

2.5.3 Assessment of Compressors and Compressed Air System

1. Capacity of a Compressor

The capacity of a compressor is the full rated volume of flow of gas compressed and delivered

under conditions of total temperature, total pressure, and composition prevailing at the compressor

inlet. It sometimes means actual flow rate, rather than rated volume of flow. This is also called free

air delivery (FAD)

Actual Free Air Delivery

Nm3/min

Where,

P2 = Final Pressure after filling (kg/cm2 a)

P1 = Initial Pressure (kg/cm2 a) after bleeding

P0 = Atmospheric Pressure (kg/cm2 a)

V = Storage volume in m3 which includes receiver, after coller, and delivery piping

T = Time take to build up pressure to P2 in minutes

The above equation is relevant where the compressed air temperature is the same as the ambient air

temperature, i.e., perfect isothermal compression. In case the actual compressed air temperature at

discharge, say t2 C is higher than ambient air temperature say t1 0C (as is usual case), the FAD is to

be corrected by a factor (273 + t1) / (273 + t2).

2. Compressor Efficiency

Under compressor efficiency there are different measures that compressor efficiency are commonly

used to measure compressor efficiency: volumetric efficiency, adiabatic efficiency, isothermal

efficiency and mechanical efficiency.

2.1 Free air delivered

Free air delivered Qf,

Where, = Flow coefficient as per IS D = Nozzle diameter M

= Absolute inlet temperature P1 = Absolute inlet pressure kg/cm2

P3 = Absolute pressure before nozzle kg/cm2 Ra = Gas constant for air 287.1 j/kg k

3 = Absolute temperature before nozzle k

P3-P4 = Differential pressure across the nozzle kg/cm2

2.2 Isothermal efficiency

Isothermal efficiency =


34

Isothermal power (kW) =

Where, P1 = Absolute intake pressure kg/ cm2

Q1= Free air delivered m3/hr.

r = Pressure ratio or compression ratio P2/P1

The calculation of isothermal power does not include power needed to overcome friction and

generally gives an efficiency that is lower than adiabatic efficiency. The reported value of efficiency

is normally the isothermal efficiency. This is an important consideration when selecting

compressors based on reported values of efficiency.

2.3 Volumetric Efficiency

Compressor Displacement =

Where D = Cylinder bore, meter L = Cylinder stroke, meter

S = Compressor speed rpm n = No. of cylinders

= 1 for single acting and

2 for double acting cylinders

For practical purposes, the most effective guide in comparing compressor efficiencies is the specific

power consumption, i.e. kW/volume flow rate, for different compressors that would provide

identical duty.

2.4 Specific power consumption at rated discharge pressure

Specific power consumption at rated discharge pressure =

Example

A FMCG Company is using the screw compressor for production operation. This has been following

Specification; calculate volumetric flow rate, isothermal efficiency, specific power requirement and

Actual Free air delivered.

Given, for Actual Free Air Delivered

Piston displacement = 16.88 m3/min

Theoretical compressor capacity = 14.75 m3/min

Receiver volume = 7.79 m3

Initial pressure (P1) = 0.5 kg/cm2

Final pressure (P2) = 7.03 kg/cm2

Atmospheric pressure (P0) = 1.026 kg/cm2 a

Compressor rated rpm 750 = 1445 motor rated rpm

Total volume = 8.332 m3

Compressor output (m3/min) =

= 13.739 m3/min

Capacity shortfall with respect to 14.74 m3/min rating is 1.011 m3/min i.e. 6.85%, which indicates

performance of compressor needs to be investigated further.

For Free air delivered, Given:

Flow coefficient (k) = 1 (assume) Nozzle diameter (d) = 0.08 meter

Receiver pressure (P2) = 3.5 kg/cm2 (a) Inlet pressure (P1) = 1.04 kg/cm2 (a)

Inlet air temperature (T1) = 303 k Pressure before nozzle (P3) = 1.08 kg/cm2

Temperature before nozzle (T3) = 313 k Gas constant (Ra) = 278 J/kg K

Motor input = 100 kW Motor and drive efficiency = 86 %


35

Compression ratio (r) =

= 3.36 Pressure drop across the nozzle (P3 – P4) = 0.036 kg/cm2

Compressor input power = 86 kW

Free air delivered = 1

= 0.384 m3/sec

= 1385.511 m3/hr

Now,

Isothermal power (kW) =

= 47.58 kW

Isothermal Efficiency =

=

= 55.32 %

And, specific power consumption =

=

= 0.0721 kW/m3/hr

2.5.4 Findings

Compressed air is most expensive energy among the industry.

Compressor only near about 10% of compressed air delivered and other energy is converted into

heat (i.e. heat losses)

According to research a pinpoint leakage of compressed air per year takes Rs. 1,12,000.

Piping system is played vital role for compressed air deliver losses.

Efficiency of compressor also depends up on altitude.


Here are recommendations help to enhance the efficiency of compressor

Reduction of the use of air hoists, and air motors.

Find and fix current compressed air leaks and try to prevent the same. Check for leaks and

pressure losses throughout the system regularly (monthly).

Avoid the improper, yet common practice of cracking drains in an effort to insure moisture free

performance at a particular point-of- use.

Shut off the air supply to "off- line" production equipment.

Ensure the entire system is monitored by good housekeeping practices.

Ensure condensation can be removed swiftly from the distribution network, or does not occur.

Check that receivers are sized to store air for short heavy demands.

Use high efficiency motors in place of standard motors.

Consider multiple staged compressors.

Understand the requirements for clean- up equipment.

Use the drying technology that gives you the maximum allowable pressure dew point.

Choose "best in class" products for all compressor parts in case of replacements.

Use waste heat off the compressor to help the rest of the plant save energy.

Avoid delivering higher pressure to the entire plant just to meet the requirements of one user.

Understand multiple compressor system controls.

Adopt a systematic preventive maintenance strategy for your compressor.


36

2.6 HVAC System

HVAC system is heating ventilation and Air conditioning system installed in factory for maintaining the

temperature as per required of system it consumes significant amount of energy which varies with load

change, season, operation and maintenance and ambient conditions etc. so its performance evaluation

should be take to extent possible all these factors. Here we only concerned in industrial HVAC system.

Fig: General Refrigeration cycle Fig: Schematic representation of refrigeration system

Refrigeration system is used in industry for chilling the products or preserving the products for long

time. Basically, Refrigeration systems are used in Dairy industry, Cold storage, brewery and shipping

the products. Air Conditioning system is also similar to the refrigeration system but some operationally

use of system is quite different. Air conditioning system is used to maintain temperature as required

quantity of system and it can be used for human comfort. Basically, HVAC systems are used in big

hotel, Tele communication and those industries which needed high temperature lift.

Basically in HVAC system comprises; Compression process, Condensation process, Expansion process

and Evaporation process. This system takes the compressor (for Vapour Compression Refrigeration

system) or absorber and generator (for vapour absorption refrigeration system) which consumes

significant amount of electricity compared to other system.

2.6.1 Objectives of HVAC system Assessment

The objective of HVAC system assessment is to verify the performance of HVAC system by using field

measurements. The test will measure net cooling capacity (TR) and energy requirements, at the actual

operating conditions. The objective of test is to estimate the energy consumption at actual load verses

design conditions.

2.6.2 Terminology and definition

a) Tons of refrigeration (TR): the amount of cooling obtained by one ton of ice melting in 24 hour:

210 kJ/min, 12000 Btu, 3.5 kW or 3024 kCal/hr.

b) Net Refrigerating Capacity: It is mass flow rate of the evaporator water multiplied by the

difference in enthalpy of water entering and leaving the cooler, expressed in kCal/h or TR.

c) Coefficient of Performance (COP): It is the ratio of heat extracted in the refrigerator to the work

done on the refrigerant. It refers to heating efficiency of an air conditioner.

d) kW/Tons rating: Commonly referred to as efficiency, but actually power input to compressor

motor divided by tons of cooling produced, or kilowatts per ton

e) Energy Efficiency Ratio (EER): performance of smaller chillers and rooftop units is frequently

measured in EER rather than kWton. EER is calculated by dividing a chiller’s cooling capacity in

watts) by its power input (in watts) at full-load conditions.

High Temperature Reservoir

Low Temperature

Reservoir

R

Work (W)

Condenser

Evaporator

H C

High pressure, Temperature side

Low pressure,

temperature side

Compressor

Expansion valve

Q1

Q2= Q1+W


37

2.6.3 Components of HVAC System

The various components of HVAC systems are

1) Chiller plant

a) Evaporator unit

b) Compressor unit

c) Condenser unit (air cooled/water cooled and condenser fan/cooling tower fan)

2) Air handling unit (with fans/blowers)

3) Primary and secondary chilled/cooling water pumps


There are many potential opportunities which help for energy conservation in HVAC system which is as

follows:

1. Optimization of Process Heat Exchangers 2. Maintenance of Heat Exchanger Surfaces

3 Multi-staging for Efficiency 4. Matching Capacity to System load

5 Capacity control and Energy Efficiency 6. Multi-level Refrigeration for Plant Needs

7 Chilled water storage 8 System Design Features

Strictly addressed the above actives energy conservation may enhance and increase the COP of

system with saving huge amount of capital.

2.6.5 Assessment of HVAC System

For executing the HVAC system assessment, at first establish the steady-state conditions then three sets

of data shall be taken, preferably at a minimum of five minute interval. To minimize the effects of

transient conditions, test readings should be taken simultaneously to the extent possible in all

components of HVAC system.

Performance evaluation of Refrigeration system:

1) Net Refrigeration Capacity (TR)= –

Where, Q = Mass flow rate of coolant in kg/hr

Cp = Coolant specific heat in kCal /kg

Ti = Inlet, temperature of coolant to evaporator (chiller) in

To = Outlet temperature of coolant from evaporator (chiller) in .

1 TR = 3024 kCal/hr heat rejected

2) Compressor Power (kW)

Power (kW) =

3) Heat rejected at the condenser

Heat rejected at condenser = cooling load + work done by compressor

Heat rejected (TR) = (Evaporator TR) +

Heat rejected (TR) =

The shaft power kW absorbed (work done) by the compressor can be derived by measuring the

motor input power multiplied by motor operating efficiency.

Heat rejected at condenser can be measured as under:

Water cooled condenser: measure the water quantity flow through condenser coil

Mc = Mass flow rate of cooling water, kg/hr


38

Cp = Coolant specific heat in kCal kg C

wi = Inlet, temperature of coolant to evaporator chiller) in C

wo = Outlet temperature of coolant from evaporator chiller) in C.

Air cooled condenser: measure the air quantity flow through the condenser coil

Heat rejected (TR) =

Ma = Mass flow rate of air, kg/hr

Cpa = Coolant specific heat of air, kCal kg C

ai = Inlet, temperature of cooling air in C

ao = Outlet temperature of cooling air in C.

Coefficient of Performance (COP) =

=

or

or

Where, Q1 = heat taken from evaporator (kJ/min)

Q2 = heat delivery to condenser (kJ/min)

W = work done (kJ/sec)

Te = Evaporator temperature in

c = condenser temperature in

Energy efficiency ratio (EER) =

Power per Ton (kW/ton) =

Performance Evaluation of Air Conditioning For air conditioning units, the airflow at the Fan Coil Units (FCU) or the Air Handling Units (AHU)

can be measured with an anemometer. Dry bulb and wet bulb temperatures are measured by

psychrometer at the inlet and outlet of the AHU or the FCU. While assessing AC performance

should be considered followings bullets:

Accuracy of flow and temperature measurements

Integrated part load value (IPLV)

Heat load (TR) =

Where, Q = the air flow in m3/h

= density of air kg/m3

hin = enthalpy of inlet air kCal/kg

hout = enthalpy of outlet air kCal/kg

Use of psychometric charts can help to calculate hin and hout from dry bulb and wet bulb

temperature values which are measured during trials by a whirling psychrometer. Power

measurements at compressor, pumps, AHU fans, cooling tower fans can be taken with a portable

load analyzer.

Example 1

Suppose, a brewery company planning to estimate the performance for an air conditioning system

which has direct expansion type air handling unit. As per given parameter calculate heat load

Given,

Air flow (m) = 25000 m3/hr Air density ( = 1.29 kg/m3

Air DB temperature at evap. inlet = 3 C Air WB temperature evap. inlet = C

Air DB temperature at evap. outlet = C Air WB temperature evap. Outlet = C


39

Enthalpy of air at evap. inlet(hin) = 60 kJ/kg Enthalpy of air at evap. Outlet (hout) =

47kJ/kg

Calculation:

Heat load (TR) =

= 13.86 TR

Example 2

A Dairy Company collected data during the energy audit of chilled water system. Find out the Net

refrigeration capacity, COP, and kW/TR

Power drawn by compressor motor = 90 kW Motor efficiency = 87 %

Compressor circuit- 2 A loading = 61 % Compressor circuit -2B loading = 59 %

Primary pump power = 9 kW Secondary pump power = 2 kW

Chilled water temp. Outlet of evap. = 7.2 Chilled water temp. Inlet to evap. = 9

Chilled water flow via the primary circuit = 148 m3/hr

Calculations:

Net refrigeration capacity (TR) = –

= 88.09 TR

KW/ton rating =

=

=0.89 kW/TR

Coefficient of Performance (COP) =

= 3.95

2.6.6 Findings

It is also one of the costly utilities used in industry.

Refrigerant used in compressor is harmful for man environment if exposed outside

surroundings.

Compressor consumed more electricity for operation rather than other electric utilities.

HVAC system consists many devices so there are several loophole for losses, similarly there are

several energy saving opportunities

HVAC system measures in TR.


Here are recommendation energy efficiency options of HVAC system:

Install a programmable thermostat unit, if you do not have one. You can save as much as 10 to

15% on your cooling bill by simply turning your thermostat back 10 to 15 degrees for 8 hours.

Building Heat Loads Minimization: minimize the air conditioning loads by measures such as

roof cooling, roof painting, efficient lighting, pre-cooling of fresh air by air- to-air heat

exchangers, variable volume air system, optimal thermo-static setting of temperature of air

conditioned spaces, sun film applications, etc.

Replace or clean the filter and clean the evaporator and condenser coils regularly, for the air

conditioner to cool efficiently.

A good air filter will extend the life of your air conditioner because the important parts, like the

blower assembly, the cooling coil, and other inner parts will stay cleaner, operate more

efficiently and last longer.

Avoid frequent opening of doors/windows. A door kept open can result in doubling the power

consumption of your AC.


40

3. Conclusion

With poor practice of energy efficiency measurement in most of the industries, heavy energy cost

is switched on through energy losses. With the advantage of energy efficiency practices and

technologies, it is possible to cut down energy cost significantly in the industries without reducing the

productivity of industrial utilities.

But there are several constrains for energy auditing in industries which significantly affects in

energy audit works, auditor should be addressed each and every problems. According my study

there are many losses associated with industrial utilities can be minimized by small efforts of

stakeholder which may be huge economic value. So that, through this paper I have tried to address

those losses which can be eliminated or reduced. In Universe, there are list of countries which

regularly executed energy efficiency work in their industries. Specially, I am talking about my

country, there are no mandatory rule and regulation for energy efficiency of industries. Not only

this much but also here is lack of energy efficiency related experts.

Evidently, my research paper has tried to address different opportunities, losses associated with industrial

utilities and finding and recommendation also provided to enhance energy efficiency of industrial utilities. I

believe that this research paper may help as a small milestone in coming days in the sector of energy

efficiency of industrial utilities.

4. Bibliography

www.unep.fr

Energy Guide Industry Asia, (UNEP)

www.moi.gov.np

www.doind.gov.np

www.energy-efficiency.gov.uk

www.aepc.gov.np

www.nea.org.np

www.un.org/millenniumgoals/

Bureau of Energy Efficiency India, 2004

Federation of Nepalese Chamber of Commerce and Industry (FNCCI)

Nepal Energy Efficiency Program (NEEP)

Energy Efficiency Center (EEC)

Old Reports

Competitiveness and sustainability unit European IPPC Bureau

A text book of Industrial Energy Efficiency, office of technology assessment, congress of US

http://www.unep.fr/

http://www.moi.gov.np/

http://www.doind.gov.np/

http://www.energy-efficiency.gov.uk/

http://www.aepc.gov.np/

http://www.nea.org.np/

energy efficiency of industrial utilities-pratap jung rai

Engineering

energy audit energy

analysis of energy

energy conservation

energy security

energy usage

energy prices

energy costswaste

energy shortages