energy audit (ea)

Energy Audit (EA)

Md. Mizanur Rahman, PhD

Certified Energy Manager

What is an energy audit?

• An energy audit is a periodic examination of an energy system (or part of the system) to ensure the most appropriate sources of energy are employed, and this energy is used as efficiently as possible.

• Energy Audit - the periodic survey, measurement, reporting, analysis and examination of an energy system (or part of the energy system)

• An energy audit involves an analysis of a facility to determine the forms of energy used, the quantities and costs of the various forms of energy used, the purposes for which the energy is being used, and the identification of energy conservation opportunities

• An energy audit serves the purpose of identifying where a building or plant facility uses energy and identifies energy conservation opportunities

• a detailed analysis ... of the productivities of energy in the various subsystems, and the deficiencies observed ... [which] should, if properly designed, lead to proposals for correcting the deficiencies, cost effectively

• a systematic assessment of where, why and how energy

is used in buildings and how well this energy is controlled

An energy audit comprises a detailed analysis of the energy performance of an organization, equipment, system(s) or process(es).

It is based on appropriate measurement and observation of energy use, energy efficiency and consumption.

Energy audits are planned and conducted as part of the identification and prioritization of opportunities to improve energy performance, reduce energy waste and obtain related environmental benefits.

Audit outputs include information on current use and performance and they provide ranked recommendations for improvement in terms of energy performance and financial benefits

2

EA is a top-down initiative – its effectiveness relies on the resources that should be allocated to energy audit by the management

Commitment on energy conservation and environmental protection

Anticipation on the energy savings achievable Aspiration of the improvement to corporate image by promoting energy efficiency and conservation

3

Objectives of EA

The less energy is consumed the less fossil

fuels will be burnt

Thus building owners and power producers will generate relatively less pollutants and by-products

Therefore all parties contribute to conserve the environment

and to enhance sustainable development

4

Why conduct EA? To develop database

To determine if energy is being used efficiently

Identify opportunities for saving energy

Identify cost savings

Highlight potential improvements to existing systems

Assist in planning for future expansion

Who would benefit?

Everybody - through conserving energy and protecting the environment

Commercial building owners • longevity of plant and equipment

Building and facility managers

• reduced operating costs

Site engineering and maintenance staff

• increased plant efficiencies

What are the benefits of EA?

Energy savings

Avoiding power factor penalties

Quality improvements

Productivity improvements

Reduced maintenance

Fewer breakdown

Better safety and protection

7

EA types

• Energy audits are the first step to improve the energy efficiency of buildings and industrial facilities.

• Energy audit is one of the tools of energy management

• Generally, four types of energy audits can be distinguished as briefly described below:

i. Walk-through energy audit

ii. Audit of historical data

iii. Standard energy audit

iv. detailed energy audit

11

1. Walk-through audit

Consists typically of a short on-site visit of the facility to identify areas where simple and inexpensive actions (typically operating and maintenance measures) can provide immediate energy-use and/or operating cost savings.

2. Historical data audit

A careful evaluation of metered energy-uses and operating costs of the facility. Typically, the utility data over several years are evaluated to identify the patterns of energy-use, peak demand, weather effects, and potential for energy savings.

12

3. Standard energy audit

Consists of a comprehensive energy analysis for the energy systems of the facility. It includes the development of a baseline for the energy-use of the facility, the evaluation of the energy savings, and the cost-effectiveness of appropriately selected energy conservation measures

4. Detailed energy audit

It is most comprehensive but also time-consuming energy audit type. It measures energy-use for the whole facility. Sophisticated computer simulation programs are typically considered

13

Energy audit can also be classified as:

Preliminary audit

Detailed audit

Investment audit

Preliminary Audit

Allows the overall energy consumption of the facility to be

evaluated.

Gives an overview, providing a rough estimate of savings

and costs.

Designed to determine if the level of energy use in the

building has been reasonable or excessive. It provides

initial benchmarks of the building.

Preliminary Audit

Scope of work for preliminary audit is as follows:

Gather building wide energy use on monthly and/or annual basis

Derive performance indicator (kWh/m2/year for building, kW/ton for air- conditioning unit, W/m2 for lighting load)

Broad conclusions and recommendations

Written report.

Data Collection One of the key tasks in energy auditing is the collection of all

energy related data, which allows the Energy Manager or

Energy Auditor to apportion the total facility energy

consumption to various energy end-uses and build a reliable

picture of where, how much and at what cost energy is being

used at various end-uses.

Data collection is one of the most laborious tasks in energy

auditing and the inability to collect the required data will lead

to unreliable energy audit results.

Desktop Data Collection

It is advisable to start the desktop data collection by

gathering the overall energy related data for the audited

facility. Questionnaires are prepared for data collection for

manufacturing and building facilities. Before the start of an

energy audit, the facility engineer should complete the

questionnaire(s). This is to save the Auditor time.

Desktop data collection includes gathering all data related to

audited facilities, processes and/or energy end-uses. This

includes all facility drawings, electricity supply, metering,

energy consumption and production details (if it is relevant).

Using desktop and field data, the Auditor should be

able to estimate the annual energy consumption of

various energy end-uses.

The total annual energy of end-uses should match the

actual annual energy consumption of the whole facility.

It is normal to find discrepancies between the

estimated and actual annual energy consumption.

The high level of discrepancy indicates to the Auditor

that there are errors in calculations or used

assumptions in calculating the annual energy

consumption. In this case the Auditor should review all

calculations until he or she is satisfied with the result.

Detailed Audit

Identifies the source of energy to a building, the amount supplied and what the energy is used for.

Identifies areas where savings may be achieved, recommends measures to be taken and provides a statement of costs and potential savings.

Involves short term metering and logging.

Detailed Audit Scope of work

Follow-up from preliminary audit and report where available Detailed building and system’s energy input and energy use Reconciliation of energy accounts with loads Variation of energy on month-to-month basis Energy performance indicators Recommend improvement work with indicative cost and saving Written report and presentation.

Field Data Collection The field data collection is a critical

step in Energy Auditing. Through this process the Energy Auditor is able to:

Complete the missing data not available to the Auditor during the desktop data collection process. Verify certain data collected during desktop data collection process. Understand closely certain manufacturing processes, make observations about energy wastes and maintenance status in the facilities. Carry out necessary field measurements required to build energy and mass balance of the audited facilities.

Data Logging

• Using energy data logging equipment, the Energy Auditor can monitor the distribution of energy between various parts of the audited facilities. To capture the pattern of energy uses in the audited facility, the daily load curves should be obtained for a number of days, i.e. 2 days to a week or more.

• Using the recorded daily load curves, the Auditor should be able to estimate the total annual energy end- uses of the whole audited facility. The estimated annual energy consumption of the whole facility should be equal to the actual facility annual energy consumption.

Investment Audit

Provides a detailed analysis of energy usage, the savings

that can be made, and the cost of achieving those savings

May cover the whole building or may concentrate on an

individual item and/or system

Involves long term detailed metering and data logging.

Investment Audit

Scope of work

Detailed metering down to half-hourly interval where required Derive target energy use and develop baseline model where relevant Detailed recommendations including costs, savings and accuracy of estimates Detailed investment plan Written report and presentation

Electrical energy audit

Areas covered under electrical audit:

• Electrical system

• Electrical distribution system (substation and feeders only)

• PF improvement • Transformer optimization • Cable sizing and loss reduction • Motor loading survey • Lighting system

2

1

Areas covered under mechanical audit:

Fans and blowers

Exhaust and ventilation system

Pumps and pumping system

Compressed air system

Air conditioning and refrigeration system

Cooling tower system

2

2

Mechanical systems

Thermal system

Areas covered under thermal energy audit:

Steam generation boilers

Steam audit

Steam trap survey Condensate recovery system

Insulation survey

Heat exchanger

Waste heat recovery

2

3

Stages of EA

2

4

General Procedure for Energy Audit

• Several tasks are typically carried out depending on the type of the audit and the size and function of the audited building

• Some of the tasks may have to be repeated, reduced in scope, or even eliminated based on the findings of other tasks

• The execution of an energy audit is often not a linear process and is rather iterative

• A general procedure can be outlined for most facilities

30

Step 1: Facility and Utility Data Analysis.

The main purpose of this step is to evaluate the characteristics of the energy systems

Some of the tasks in this step

• Collect at least three years of utility data (to identify a historical energy-use pattern).

• Identify the fuel types used such as electricity, natural gas, oil, etc. (to determine the fuel type that accounts for the largest energy-use).

• Determine the patterns of fuel use by fuel type (to identify the peak demand for energy-use by fuel type).

• Understand utility rate structure (energy and demand rates) (to evaluate if the building is penalized for peak demand and if cheaper fuel can be purchased).

• Analyze the effect of weather on fuel consumption (to pinpoint any variations of energy-use related to extreme weather conditions).

31

General Procedure for a Detailed Energy Audit

Step 2: Walk-Through Survey.

From this step, potential energy savings measures should be identified.

Some of the tasks involved in this step are:

• Identify the customer concerns and needs.

• Check the current operating and maintenance procedures.

• Determine the existing operating conditions of major energy-use equipment (lighting, HVAC systems, motors, etc.).

• Estimate the occupancy, equipment, and lighting (energy-use density and hours of operation).

32


Step 3: Baseline for Building Energy-Use The main purpose of this step is to develop a base-case model

This model is to be used as a reference

The major tasks to be performed during this step are as follows:

• Obtain and review architectural, mechanical, electrical, and control drawings.

• Inspect, test, and evaluate building equipment for efficiency, performance, and reliability.

• Obtain all occupancy and operating schedules for equipment (including lighting and HVAC systems).

• Develop a baseline model for building energy-use.

• Calibrate the baseline model using the utility data and/or metered data.

33


Step 4: Evaluation of Energy Savings Measures.

To achieve this goal, the following tasks are recommended:

• Prepare a comprehensive list of energy conservation measures (using the information collected in the walk-through survey).

• Determine the energy savings due to the various energy conservation measures pertinent to the building using the baseline energy-use simulation model developed in phase 3.

• Estimate the initial costs required to implement the energy conservation measures.

• Evaluate the cost-effectiveness of each energy conservation measure using an economical analysis method (simple payback or life cycle cost analysis).

34

Energy Audit Report

The energy audit report should present in sufficient details:

Executive Summary Description of the audited premise/manufacturing process. The historical energy use related to the audited premise occupancy or productions of the manufacturing facilities. The current energy use apportioned by end uses.

The energy saving measures including their implementation costs and estimated savings. The list of names of suppliers and contractors that the client can approach when he/she decides to implement the energy audit recommendation should be included. Strategy for implementing the recommended energy saving measures. Achieved savings after implementation.

Resources for Energy Audit

Computers

and

software

tools

Energy

records

Auditors

Company staff or

external

consultants

Instruments

Permanent and

portable

Budget and

time

Information Required For Audits

Monthly electricity bills, purchase of energy

Log-books with daily, weekly or monthly records

Details of equipment – purchase date, rating, manuals

M&E and structural drawings of building

Records of daily characteristics for electricity consumption

Co-operation with in-house staff is indispensable

for auditing and even more important during

implementation

Required Measurements

temperatures and pressures

combustion gas analysis

flow rates

relative humidity

water conductivity

lighting intensity

electricity system measurements

Typical Instruments

contact temperature measurement – digital electronic

temperature indicators, and range of detachable probes

(insertion probes, contact probes for surface temperatures)

non-contact temperature measurement – infrared and

disappearing filament pyrometers for surface temperatures

pressure – electronic pressure gauges and manometers

gas analyser – electronic analyser for measuring oxygen,

carbon monoxide and stack gas temperature, with automatic

calculation of combustion efficiency.

pitot tube – for measuring air flow rates to boilers and

furnaces.

temperature & humidity – hand held electronic instrument.

conductivity – electronic instrument with combined

conductivity/temperature probe for monitoring the quality

of boiler feedwater and blowdown.

photocell light meter

electricity – clip – on meters for measuring voltage,

current, resistance, power factor, load (kW), consumption

(kWh); often combined within one multimeter with

computerized memory and printer for making permanent

records.

data recording – from strip chart recorders to

microcomputer data loggers with multiple channels.

Output of Energy Audits

Report containing

Energy Saving measures

(‘IDEAS’) proposals and

recommendations !!!!!

Provide evidence of profitability with simple

calculations !!!!

Summarise results for decision makers !!!!

Potential Saving Measures

Reporting (Analysis of Current Performance)

a breakdown of the energy consumption by use and

source;

energy uses accounting for substantial energy

consumption;

where available and comparable, comparison with

reference values of similar processes;

a historical pattern of energy performance;

expected improvements for energy performance;

where appropriate, relationships between energy

performance and relevant variables;

an evaluation of the existing energy performance

indicators and, if necessary, proposals for new energy

performance indicators.

Reporting

(Identification of improvement opportunities)

based on auditors competency and expertise;

evaluation of the design and configuration options to

address the system needs;

the operating lifetime, condition, operation and level of

maintenance of the audited objects;

the technology of existing energy uses in comparison to

the most efficient on the market;

best practices, including operational controls and

behaviours;

future energy use and changes in operation.

Reporting

(Evaluation of improvement opportunities)

energy savings over an agreed time period or expected

operating lifetime;

financial savings anticipated from each improvement

opportunity;

necessary investments;

agreed economic and other criteria identified in the energy

audit planning;

other non-energy gains (such as productivity or

maintenance);

the ranking of energy performance opportunities;

potential interactions between various opportunities.

Classification of Energy Efficiency Measures

Short Term :

(Measurement, Control and Maintenance)

Thermal System (Maintenance and Control)

Boilers and steam distribution network

combustion control (air-fuel ratio) blowdown control periodic cleaning of exchanger surfaces maintenance of insulation on the hot utility network make-up water quality control check steam leaks

Electrical System (Maintenance And Control)

Electrical Supply And Distribution Network

Matching of transformer with the load Proper ventilation of transformer room Operation of standby generators during the peak hours Use of suitable electric tariff Use of daylighting and switching off unnecessary lighting Load control and sharing/duty cycling to reduce the maximum demand

Chiller/Air-conditioning system

Accurate temperature and humidity control to suit the need

Maintenance of condenser/evaporator coils

Adjustment of chilled water temperature

Improve performance of cooling towers

Use of timers in specific zones

Prevent infiltration of warm air in the conditioned space

Reduction in mixing of supply and return streams

Duty cycling of air handling units for peak load management


Adjust supply pressure to suit the required use

Matching of compressors with the loads

Supply of air at the lowest temperature

Adequate inter-stage cooling of compressed air

Provision for evacuation of condensate water from

the line

Check leaks in the distribution circuits

Medium Term : (Utilities and Process Improvements)

Thermal system (utilities and networks) Boilers and steam distribution network

Replacement of burners Combustion efficiency controller Flue gas heat recovery using preheater/economizer Blowdown sensible and latent heat recovery Appropriate insulation of boiler, steam piping, joints and flanges Steam piping sizing to minimize thermal losses Installation of suitable steam traps Flash steam recovery from the condensate Generation of low pressure steam from high pressure condensate Use of steam-ejector for recovering low pressure vapour or heat from low temperature condensate Heat recovery from high temperature effluent for preheating make- up water

Electrical system (utilities and networks)

Electricity supply and distribution network

load factor improvement to reduce specific

electricity cost

power factor improvement using capacitor banks

installation of maximum demand controller

greater use of cheap off-peak electricity for

specific applications

replacement of inefficient lights by efficient ones

Chiller/Air conditioning system

Optimization of multiple chiller’s operation Variation of chilled water flow rate according to the load Variable air volume (VAV) system Enthalpy control (intake of ambient air instead of return air) Option of ice/chilled water storage for peak demand management


Optimization of compressed air distribution network

Decentralized supply of compressed air at a far-away site

Use of multi-stage compressor with intercooling

Provision for compressed air storage to handle fluctuation

load

Process Improvements

Switch from batch process to continuous process

Replacement of inefficient motor by an efficient one

Choice of variable speed drives for varying loads

Heat integration through energy recovery and thermal

cascading

Long Term : (New Technologies And Processes)

New Technologies Combined heat and power generation (cogeneration by steam turbine, gas turbine and diesel engine)

Install generator for use during peak period

Efficient boilers, compressors, chillers, transformers, etc.

New alloys reducing thermal inertia and losses

Absorption chiller operating in cogeneration mode

Heat pump for drying, simultaneous heating and cooling applications

Technologies related to fuel substitution (oil, gas, electricity)

Use of renewable sources of energy

Step 1: Facility

and Utility Data

Analysis.

Step 2: Walk-

Through

Survey

Step 3:

Baseline for

Building

Energy-Use.

Step 4:

Evaluation of

Energy

Savings

Measures

Energy audit result sheet

Summary • An energy audit will:

– Determine where energy is being used, in what form, in what quantities

– Relate energy use to output of products or services

– Highlight areas of significant energy use

– Provide estimates of potential energy savings

– Establish a base

– Report

– Suggested measures

Discuss with your peer (5 minutes) 1. What actually energy audit is?

2. Why is Energy audit necessary?

3. Can I perform some sort of Energy audit in my

facility (e.g. house, shop, office etc)?

4. What are the steps?

5. How to make audit report?

63

energy audit (ea)

Documents