Here is a compilation of essays on ‘Energy Audit’ for class 9, 10, 11 and 12. Find paragraphs, long and short essays on ‘Energy Audit’ especially written for school and college students.
Essay on Energy Audit
- Essay on the Introduction to Energy Management
- Essay on the Need for Energy Audit
- Essay on the Types of Energy Audit
- Essay on Energy Audit Team
- Essay on Energy Audit Methodology
- Essay on the Process Flow Diagram of Energy Audit
- Essay on Energy Audit Reporting Format
- Essay on Energy Audit Instruments
- Essay on Energy Audit for Buildings
Essay # 1. Introduction to Energy Management:
An energy audit is an inspection, survey and analysis of energy flows in a building, process or system with the objective of understanding the energy dynamics of the system under study. Typically an energy audit is conducted to seek opportunities to reduce the amount of energy input into the system without negatively affecting the output(s).
When the object of study is an occupied building then reducing energy consumption while maintaining or improving human comfort, health and safety are of primary concern. Beyond simply identifying the sources of energy use, an energy audit seeks to prioritize the energy uses according to the greatest to least cost effective opportunities for energy savings.
An energy audit of a home may involve recording various characteristics of the building envelope including the walls, ceilings, floors, doors, windows and skylights. For each of these components the area and resistance to heat flow (R-value) is measured or estimated.
The leakage rate or infiltration of air through the building envelope is of concern which are strongly affected by window construction and quality of door seals such as weather-stripping. The goal of this exercise is to quantify the building’s overall thermal performance. The audit may also assess the efficiency, physical condition and programming of mechanical systems such as the heating, ventilation, air conditioning equipment and thermostat.
A home energy audit may include a written report estimating energy use given local climate criteria, thermostat settings, roof overhang and solar orientation. This could show energy use for a given time period, say a year and the impact of any suggested improvements per year. The accuracy of energy estimates are greatly improved when the homeowner’s billing history is available showing the quantities of electricity, natural gas, fuel oil, or other energy sources consumed over a one or two-year period.
Increasingly in the last several decades, industrial and agricultural energy audits have exploded as the demand to lower increasingly expensive energy costs and move towards a sustainable future have made energy audit important.
Energy-audit is the basic tool by which a rational energy management programme can be developed in any sector using energy. Until an assessment has been carried out on how the energy flows within an establishment, areas where wastage occurs cannot be highlighted and the scope for improvements identified.
Energy audit is similar to the financial audit. It involves brief on site survey and analysis of the systems concerned. It can be defined as the technique for assessing the energy conservation potential. Energy audit is the key to a systematic approach for decision-making in the area of energy management. It attempts to balance the total energy inputs with its use and serves to identify all the energy streams in a facility. It quantifies energy usage according to its discrete functions. Industrial energy audit is an effective tool in defining and pursuing comprehensive energy management programme.
As per the Energy Conservation Act, 2001, energy audit is defined as “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.”
Essay # 2. Need for Energy Audit:
In any industry, the three top operating expenses are often found to be energy (both electrical and thermal), labour and materials. If one were to relate to the manageability of the cost or potential cost savings in each of the above components, energy would invariably emerge as a top ranker and thus energy management function constitutes a strategic area for cost reduction. Energy audit will help to understand more about the ways energy and fuel are used in any industry and help in identifying the areas where waste can occur and where scope for improvement exists.
The energy audit would give a positive orientation to the energy cost reduction, preventive maintenance and quality control programmes which are vital for production and utility activities. Such an audit programme will help to keep focus on variations which occur in the energy costs, availability and reliability of supply of energy, decide on appropriate energy mix, identify energy conservation technologies, retrofit for energy conservation equipment, etc.
In general, energy audit is the translation of conservation ideas into realities by lending technically feasible solutions with economic and other organizational considerations within a specified time frame.
The primary objective of energy audit is to determine ways to reduce energy consumption per unit of product output or to lower operating costs. Energy audit provides a “bench-mark” (reference point) for managing energy in the organization and also provides the basis for planning a more effective use of energy throughout the organization.
Energy audit study helps an industry to understand and analyse its energy utilisation and identify areas of energy wastage, decide how to budget its energy use, plan and practice feasible energy conservation methods that will enhance their energy efficiency, curtail energy wastage and substantially reduce energy costs.
The energy audit serves to identify all the energy streams in a facility, qualify energy usage with its discrete functions, in an attempt to balance the total energy input with its use. Energy audit is thus the key to a systematic approach for decision-making in the area of energy management. As a result, the energy audit study becomes an effective tool in defining and pursuing comprehensive Energy Management Programme (EMP).
Energy audit of a group of similar type of industries will help generate vital information on different energy utilisation patterns and practices followed and single out best practices in particular industrial sector. Group energy audit will generate greater awareness energy efficiency and help small industries to operate more profitably.
Energy Audit Study Should Be Directed Towards:
i. Identifying cost-effective measures to improve the efficiency of energy use,
ii. Estimates of potential energy saving, implementation costs and payback periods for each recommended action, and
iii. Documenting results and vital information generated through these activities.
An Energy Audit Study Includes:
i. Auditing of energy consumption (including any heat and power generated).
ii. General examination of work place (including physical condition of organisation, its processes, occupancy time and variations in ambient temperature and energy consumption pattern, etc.).
iii. Measurement of all energy flows, (including testing of boiler or steam raising, heating equipment, refrigeration, etc.).
iv. Analysis and appraisal of energy usage (e.g., specific fuel consumption, energy-product interrelationship).
v. Energy management procedures and methodology.
vi. Identification of energy improvement opportunities and recommendations for energy efficiency measures and quantification of implementation costs and paybacks.
vii. Identification of possible usage of co-generation, renewable sources of energy and recommendations for implementation, wherever possible, with cost benefit analysis.
Essay # 3. Types of Energy Audit:
The term energy audit is commonly used to describe a broad spectrum of energy studies ranging from a quick walk-through of a facility to identify major problem areas to a comprehensive analysis of the implications of alternative energy efficiency measures sufficient to satisfy the financial criteria of sophisticated investors.
The type of energy audit to be performed depends on:
i. Function and type of industry,
ii. Depth to which final audit is needed, and
iii. Potential and magnitude of cost reduction desired.
Thus energy audit can be classified into the following types:
(i) Preliminary audit
(ii) Mini audit or general audit
(iii) Detailed audit or comprehensive audit/investment grade audit.
i. Preliminary Audit:
The preliminary audit (alternatively called a simple audit, screening audit or walk-through audit) is the simplest and quickest type of audit. It involves minimal interviews with site-operating personnel, a brief review of facility utility bills and other operating data and a walk-through of the facility to become familiar with the building operation and to identify any glaring areas of energy waste or inefficiency.
Typically, only major problem areas will be uncovered during this type of audit. Corrective measures are briefly described and quick estimates of implementation cost, potential operating cost savings and simple payback periods are provided. The level of detail, while not sufficient for reaching a final decision on implementing a proposed measures, is adequate to prioritize energy-efficiency projects and to determine the need for a more detailed audit.
ii. General Audit or Mini Audit:
The general audit (alternatively called a mini-audit, site energy audit or complete site energy audit) expands on the preliminary audit described above by collecting more detailed information about facility operation and by performing a more detailed evaluation of energy conservation measures.
Utility bills are collected for a 12 to 36 month period to allow the auditor to evaluate the facility’s energy/demand rate structures and energy usage profiles. If interval meter data is available, the detailed energy profiles that such data makes possible will typically be analysed for signs of energy waste.
Additional metering of specific energy-consuming systems is often performed to supplement utility data. In -depth interviews with facility operating personnel are conducted to provide a better understanding of major energy consuming systems and to gain insight into short and longer term energy consumption patterns.
This type of audit will be able to identify all energy-conservation measures appropriate for the facility, given its operating parameters. A detailed financial analysis is performed for each measure based on detailed implementation cost estimates, site-specific operating cost savings and the customer’s investment criteria. Sufficient detail is provided to justify project implementation.
iii. Investment-Grade Audit/Comprehensive Audit:
In most corporate settings, upgrades to a facility’s energy infrastructure must compete for capital funding with non-energy-related investments. Both energy and non-energy investments are rated on a single set of financial criteria that generally stress the expected return on investment (ROI). The projected operating savings from the implementation of energy projects must be developed such that they provide a high level of confidence. In fact, investors often demand guaranteed savings.
The investment-grade audit (alternatively called a comprehensive audit, detailed audit, maxi audit or technical analysis audit) expands on the general audit described above by providing a dynamic model of energy-use characteristics of both the existing facility and all energy conservation measures identified.
The building model is calibrated against actual utility data to provide a realistic baseline against which to compute operating savings for proposed measures. Extensive attention is given to understanding not only the operating characteristics of all energy consuming systems, but also situations that cause load profile variations on short and longer term bases (e.g., daily, weekly, monthly, annual). Existing utility data is supplemented with sub-metering of major energy consuming systems and monitoring of system operating characteristics.
It involves preparation of total energy balance sheet, drawing energy-flow charts etc. as shown in Fig. 7.1.
Essay # 4. Energy Audit Team:
In any establishment, in order for an energy audit to be successful, a multi-disciplinary team is required covering all technical, safety, accountancy and management aspects. This is best accomplished by involving site personnel of suitable rank specialising in these aspects. An essential part of energy auditing is to establish a sound working relationship with site personnel.
The audit team normally consists of:
(i) Technical manpower,
(ii) Floor manager/supervisor, and
(iii) Audit personnel along with a person called energy-manager as team leader.
The team leader should necessarily have general technical knowledge with-lot of managerial skill. The technical manpower may consists of electrical, mechanical, electronics, instrumentation and civil engineers. The floor manager/supervisor may also have a draftsman in their team. The energy-audit-team may be shown diagrammatically as depicted in Fig. 7.2.
Essay # 5. Energy Audit Methodology:
Energy audit methodology includes the various phases and steps involved in carrying out energy audit.
Preliminary Energy Audit Methodology:
Preliminary energy audit is a relatively quick exercise to:
i. Establish energy consumption in the organisation.
ii. Estimate the scope for saving.
iii. Identify the most likely (and the easiest areas for attention).
iv. Identify immediate (especially no-/low-cost) improvements/savings.
v. Set a ‘reference point’.
vi. Identify areas for more detailed study/measurement.
vii. Preliminary energy audit uses existing or easily obtained data.
Detailed Energy Audit Methodology:
A comprehensive audit provides a detailed energy project implementation plan for a facility, since it evaluates all major energy using systems.
This type of audit offers the most accurate estimate of energy savings and cost. It considers the interactive effects of all projects, accounts for the energy use of all major equipment and includes detailed energy cost saving calculations and project cost.
In a comprehensive audit, one of the key elements is the energy balance. This is based on an inventory of energy using systems, assumptions of current operating conditions and calculations of energy use. This estimate use is then compared to utility bill charges.
Detailed energy auditing is carried out in three phases:
Phase I – Pre-audit phase
Phase II – Audit phase
Phase III – Post-audit phase
Industry-to-industry, the methodology of energy audits needs to be flexible.
A comprehensive ten-step methodology for conduct of energy audit at field level is presented below. Energy manager and energy auditor may follow these steps to start with and add/change as per their needs and industry types.
The detail of activities of various phases of audit is as follows:
Phase I: Pre Audit Phase Activities:
A structured methodology to carry out an energy audit is necessary for efficient working. An initial study of the site should always be carried out, as the planning of the procedures necessary for an audit is most important.
Initial site visit and preparation required for detailed auditing: An initial site visit may take one day and gives the energy auditor/engineer an opportunity to meet the personnel concerned, to familiarise him with the site and to assess the procedures necessary to carry out the energy audit.
During the initial site visit the energy auditor/engineer should carry out the following actions:
i. Discuss with the site’s senior management the aims of the energy audit.
ii. Discuss economic guidelines associated with the recommendations of the audit.
iii. Analyse the major energy consumption data with the relevant personnel.
iv. Obtain site drawings where available — building layout, steam distribution, compressed air distribution, electricity distribution, etc.
v. Tour the site accompanied by engineering/production.
The main aims of this visit are:
i. To finalise energy audit team.
ii. To identify the main energy consuming areas/plant items to be surveyed during the audit.
iii. To identify any existing instrumentation/additional metering required.
iv. To decide whether any meters will have to be installed prior to the audit, e.g., kWh, steam, oil or gas meters.
v. To identify the instrumentation required for carrying out the audit.
vi. To plan with time frame.
vii. To collect macro data on plant energy resources, major energy consuming centers.
viii. To create awareness through meetings/programme.
Phase II: Detailed Energy Audit Activities:
Depending on the nature and complexity of the site, a comprehensive audit can take from several weeks to several months to complete. Detailed studies to establish and investigate, energy and material balances for specific plant departments or items of process equipment are carried out.
Whenever possible, checks of plant operations are carried out over extended periods of time, at nights and at weekends as well as during normal daytime working hours, to ensure that nothing is overlooked.
The audit report will include a description of energy inputs and product outputs by major department or by major processing function and will evaluate the efficiency of each step of the manufacturing process. Means of improving these efficiencies will be listed and at least a preliminary assessment of the cost of the improvements will be made to indicate the expected payback on any capital investment needed. The audit report should conclude with specific recommendations for detailed engineering studies and feasibility analyses, which must then be performed to justify the implementation of those conservation measures that require investments.
The information to be collected during the detailed audit includes:
1. Energy consumption by type of energy, by department, by major items of process equipment, by end-use.
2. Material balance data (raw materials, intermediate and final products, recycled materials, use of scrap or waste products, production of by-products for re-use in other industries, etc.)
3. Energy cost and tariff data.
4. Process and material flow diagrams.
5. Generation and distribution of site services (e.g., compressed air, steam).
6. Sources of energy supply (e.g., electricity from the grid or self-generation).
7. Potential of fuel substitution, process modifications and the use of co-generation systems (combined heat and power generation).
8. Energy management procedures and energy awareness training programmes within the establishment.
Existing baseline information and reports are useful to get consumption pattern, production cost and productivity levels in terms of product per raw material inputs.
The audit team should collect the following baseline data:
i. Technology, processes used and equipment details.
ii. Capacity utilisation.
iii. Amount and type of input materials used.
iv. Water consumption.
v. Fuel consumption.
vi. Electrical energy consumption.
vii. Steam consumption.
viii. Other inputs such as compressed air, cooling, water, etc.
ix. Quantity and type of wastes generated.
x. Percentage rejection/reprocessing.
Data Collection Hints:
It is important to plan additional data gathering carefully.
Here are some basic tips to avoid wasting time and effort:
i. Measurement systems should be easy to use and provide the information to the accuracy that is needed, not the accuracy that is technically possible.
ii. Measurement equipment can be inexpensive (flow rates using a bucket and stopwatch).
iii. The quality of the data must be such that the correct conclusions are drawn (what grade of product is on, is the production normal etc.).
iv. Define how frequent data collection should be to account for process variations.
v. Measurement exercises over abnormal workload periods (such as startup and shutdowns).
vi. Design values can be taken where measurements are difficult (cooling water through heat exchanger).
Essay # 6. Process Flow Diagram of Energy Audit:
Draw process flow diagram and list process steps; identify waste streams and obvious energy wastage:
An overview of unit operations, important process steps, areas of material and energy use and sources of waste generation should be gathered and should be represented in a flowchart as shown in the Fig. 7.3 below. Existing drawings, records and shop floor walk through will help in making this flowchart. Simultaneously the team should identify the various inputs and outputs streams at each process step.
A flowchart of Penicillin-G manufacturing is given in the Fig. 7.3 below. Note that waste stream (Mycelium) and obvious energy wastes such as condensate drained and steam leakages have been identified in this flowchart.
The audit focus area depends on several issues like consumption of input resources, energy efficiency potential, impact of process step on entire process or intensity of waste generation/energy consumption. In the above process, the unit operations such as germinator, prefermentor, fermentor and extraction are the major conservation potential areas identified.
Essay # 7. Energy Audit Reporting Format:
After successfully carried out energy audit energy manager/energy auditor should report to the top management for effective communication and implementation. A typical energy audit reporting contents and format are given below. The following format is applicable for most of the industries. However the format can be suitably modified for specific requirement applicable for a particular type of industry.
Detailed Energy Audit
Table of Contents:
(ii) Executive summary
Energy audit options at a glance and recommendations
Introduction about the plant:
1. General plant details and descriptions.
2. Energy audit team.
3. Component of production cost (Raw materials, energy, chemicals, manpower, overhead, others).
4. Major energy use and areas.
Production Process Description:
1. Brief description of manufacturing process
2. Process flow diagram and major unit operations
3. Major raw material inputs, quantity and costs
Energy and Utility System Description:
1. List of utilities
2. Brief description of each utility
iv. Compressed air
v. Chilled water
vi. Cooling water
The following worksheets (refer Table 7.3 and Table 7.4) can be used as guidance for energy audit assessment and reporting:
Reporting Format for Energy Conservation Recommendations:
(A) Title of Recommendation:
Combine DG set cooling tower with main cooling tower, (say; example)
(B) Description of Existing System and its Operation:
Main cooling tower is operating with 30% of its capacity. The rated cooling water flow is 5000 m3 /hr. Two cooling water pumps are in operation continuously with 50% of its rated capacity. A separate cooling tower is also operating for DG set operation continuously.
(C) Description of Proposed System and its Operation:
The DG set cooling water flow is only 240 m3 /h. By adding this flow into the main cooling tower will eliminate the need for a separate cooling tower operation for DG set, besides improving the % loading of main cooling tower. It is suggested to stop the DG set cooling tower operation.
(D) Energy Saving Calculations:
Essay # 8. Energy Audit Instruments:
The requirement for an energy audit such as identification and quantification of energy necessitates measurements; these measurements require the use of instruments. These instruments must be portable, durable, easy to operate and relatively inexpensive.
The parameters generally monitored during energy audit may include the following:
Basic electrical parameters in AC and DC systems : Voltage (V), Current (I), Power factor, Active power (kW), apparent power (demand) (kVA), Reactive power (kVAr), Energy consumption (kWh), Frequency (Hz), Harmonics, etc.
Parameters of importance other than electrical such as temperature and heat flow, radiation, air and gas flow, liquid flow, revolutions per minute (RPM), air velocity, noise and vibration, dust concentration, Total Dissolved Solids (TDS), pH, moisture content, relative humidity, flue gas analysis – CO2, O2, CO, SOx, NOx, combustion efficiency, etc.
Key instruments for energy audit are listed below:
The operating instructions for all instruments must be understood and staff should familiarise themselves with the instruments and their operation prior to actual audit use.
Audit Meters and Instruments:
The following is a suggested list of meters and instruments for undertaking energy-audit:
Most of these instruments can be used in conducting an energy audit.
These instruments and audit tools should be supplemented with the performance charts /tables of energy consuming equipment operating in the establishment. If not available on site, copies should be requested from its original suppliers or from its manufacturers.
The brief description of some of these instrument is as follows:
Essay # 9. Energy Audit for Buildings:
The energy audit in a building is a feasibility study. For it not only serves to identify energy use among the various services and to identify opportunities for energy conservation, but it is also a crucial first step in establishing an energy management programme. The audit will produce the data on which such a programme is based. The study should reveal to the owner, manager or management team of the building the options available for reducing energy waste, the costs involved and the benefits achievable from implementing those energy-conserving opportunities (ECOs).
The energy management, programme is a systematic on-going strategy for controlling a building’s energy consumption pattern. It is to reduce waste to energy and money to the minimum permitted by the climate the building is located, its functions, occupancy schedules and other factors. It establishes and maintains an efficiency balance between a building’s annual functional energy requirements and its annual actual energy consumption.
Stages in Energy Programme for Buildings:
The energy audit may range from a simple walk-through survey at one extreme to one that may span several phases. These phases include a simple walk-through survey, followed by monitoring of energy use in the building services and then model analysis using computer simulation of building operation. The complexity of the audit is therefore directly related to the stages or degree of sophistication of the energy management programme and the cost of the audit exercise.
The first stage is to reduce energy use in areas where energy is wasted and reductions will not cause disruptions to the various functions. The level of service must not be compromised by the reduction in energy consumed. It begins with a detailed, step-by-step analysis of the building’s energy use factors and costs, such as insulation values, occupancy schedules, chiller efficiencies, lighting levels and records of utility and fuel expenditures. It includes the identification of specific ECOs, along with the cost-effective benefits of each one.
The completed study would provide the building owner with a thorough and detailed basis for deciding which ECOs to implement, the magnitude of savings to be expected and the energy conservation goals to be established and achieved in the energy management programme. However, the ECOs may yield modest gains.
The second stage is to improve efficiency of energy conversion equipment and to reduce energy use by proper operations and maintenance. For this reason, it is necessary to reduce the number of operating machines and operating hours according to the demands of the load and fully optimise equipment operations.
Hence the ECOs would include the following:
i. Building equipment operation,
ii. Building envelope,
iii. Air-conditioning and mechanical ventilation equipment and systems,
iv. Lighting systems,
v. Power systems, and
vi. Miscellaneous services.
The first two stages can be implemented without remodelling buildings and existing facilities.
The third stage would require changes to the underlying functions of buildings by remodelling rebuilding or introducing further control upgrades to the building. This requires some investment.
The last stage is to carry out large-scale energy reducing measures when existing facilities have past their useful life or require extensive repairs or replacement because of obsolescence. In this case higher energy savings may be achieved. For these last two stages, the audit may be more extensive in order to identify more ECOs for evaluation, but at an increased need for heavier capital expenditure to realise these opportunities.
Surveying the Building:
A walk-through survey of a building may reveal several ECOs to the experienced eye of the auditor. The survey could be divided into three parts.
Prior to the walk-through survey, the auditor may need to know the building and the way it is used.
The information can be obtained from:
i. Architectural blueprints,
ii. Air-conditioning blueprints,
iii. Electrical lighting and power blueprints,
iv. Utility bills and operation logs for the year preceding the audit,
v. Air-conditioning manuals and system data, and
vi. Building and plant operation schedules.
Thus having familiarised with the building, the walk-through process could be relatively straightforward, if the blueprints and other preliminary information available describes the building and its operation accurately. The process could begin with a walk around the building to study the building envelope. Building features such as building wall colour, external sun-shading devices, window screens and tint and so on are noted as possible ECOs.
If a model analysis is included in the study, the building must be divided into zones of analysis. The survey inside the building would include confirmed that the air-conditioning system is as indicated on plans. Additions and alterations would be noted. The type and condition of the windows, effectiveness of window seals, typical lighting and power requirements, occupancy and space usage are noted. This information could be compared against the recommendations in the relevant codes of practices.
System and plant data could be obtained by a visit to the mechanical rooms and plant room. Nameplate data could be compared against those in the building’s documents and spot readings of the current indicating panels for pumps and chillers recorded for estimating the load on the system.
The auditor may discuss with the building maintenance staff further on the operating schedules and seek clarification on any unusual pattern in the trend of the utility bills. Unusual patterns such as sudden increase or decrease in utility bills could be caused by changes in occupancy in the building or change in use by existing tenants. It is not uncommon for tenants to expand their computing operations that may increase the energy use significantly.
At this stage, ECOs could be found in measures such as:
i. Reduce system operating hours,
ii. Adjust space temperature and humidity,
iii. Reduce building envelope gain,
iv. Adjust space ventilation rates and building exfiltration,
v. Review system air and water distribution,
vi. Adjust chiller water temperatures, and
vii. Review chiller operations.
The benefit from adopting each ECO should be compared against cost of implementation. Caution should be exercised in the cost-benefit analysis given the wider range of certainty of the projections made. However, a survey at this level may be sufficient for small buildings.
The capability of the energy auditor and the scope of an audit could be extended by the use of in place instrumentation and temporary monitoring equipment. In-place instrumentation refers to existing utility metering, air-conditioning control instrumentation and energy management systems (EMS).
The use of in-place utility metering and temporary monitoring equipment in energy auditing can yield valuable information about the building systems such as:
i. Energy signature and end-use consumption analysis,
ii. Discovery and identification of ECOs,
iii. Quantification of energy use and misuse,
iv. Establishing bounds for potential energy reduction, and
v. Data acquisition for further calculation and analysis.
Existing instrumentation such as utility meter readings and energy billings could be used to establish energy consumption patterns for the building. The regularity of consumption pattern is an indicator that no significant change in consumption occurred prior to the audit. This can also be used to check the validity of projections based on extrapolated short-term monitored data. Utility data could be used to establish useful indices such as kWh/m /year to compare relative energy performance of buildings.
Air-conditioning control instrumentation such as chilled water temperature probes, water flow meters could be used to estimate cooling load demand and plant operation. For example, chilled water temperature outside the designed range may indicate that cooling coils may be operating under off-design conditions.
Short Term Monitoring:
The building may not be equipped for monitoring energy consumption and it may be necessary to install temporary measurement devices such as instantaneous recorders (strip chart, data loggers etc.) and totalizing recorders (kWh meters) to obtain data over the period of a week for the study.
Monitored data is also useful for completing the energy model of a building for use in some building energy simulation software. For example the total building energy consumption would include energy used in the vertical transportation system and potable water pumps which are not modelled in the software.
An estimate for annual consumption is extrapolated from the typical week consumption profile. Regularity of the weekly consumption profile means that the annual consumption could be estimated with confidence and the value used to cross check with the annual energy bills.
Building energy consumption in simplest terms is just the product of rate of consumption of a system and the period of operation. In lighting systems, its energy consumption could be
determined manually with precision as it does not interact with other consumption variables. Energy consumption of cooling systems, however, is many times more complicated as it is affected by the internal heat again within a building as well as weather variables, which varies in a complex manner over time.
Building model analysis using computers offers several improvements over manual calculations.
i. Precise schedule of building parameters,
ii. Precise determination of weather impact,
iii. Specification of part load performance of plant and equipment, and
iv. Consideration of parameter interactions such as lighting load on air-conditioning consumption.
Some software permit hour-by-hour calculations of building consumption for the entire 8760 hours of the year, but require thorough knowledge of the software to carry out accurate and meaningful analysis. Simplified software based on consumption analysis on characteristic days may also be considered.
However, the improvements in computational power of the desktop PC has introduced several powerful features and user-friendly graphical interface possible in more recent versions of such software making it more accessible to the practicing engineer.
The general procedure for an analysis would be to establish a model giving an annual consumption within 10% of the measured data. This establishes the base model. The impact of ECOs on energy consumption would be compared against the base model. ECOs could be considered singly or in combinations to determine the interactions between them.
The results of the energy savings in each analysis should not be taken as absolute but rather taken to be relative to the base run so as to give an indication of the order of magnitude of savings. Thus those ECOs which shows significant gains would be implemented.
The objective of energy audit is to identify the end use of energy in building and its ECOs and as a feasibility study leading to implementation of an energy management programme. The audit procedures can be expanded as needed in the various phases of the energy programme with the application of each succeeding phase yielding more information on energy use and more opportunities for raising energy efficiency.