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To perform an energy audit, several tasks are typically carried out depending on the type of the audit and the size and function of the building. Some of the tasks may have to be repeated, reduced in scope, or even eliminated based on the findings of other tasks. Therefore, the execution of an energy audit is often not a linear process and is rather iterative. However, a general procedure can be outlined for most buildings.

Step 1: Building and Utility Data Analysis

The main purpose of this step is to evaluate the characteristics of the energy systems and the patterns of energy use for the building. The building characteristics can be collected from the architectural/ mechanical/electrical drawings and/or from discussions with building operators. The energy use patterns can be obtained from a compilation of utility bills over several years. Analysis of the historical variation of the utility bills allows the energy auditor to determine any seasonal and weather effects on the building energy usage. Some of the tasks that can be performed in this step are presented below, with the key goals expected from each task noted in italics:

• Collect at least 3 years of records of utility data [to identify a historical energy use pattern]

• Identify the fuel types used (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

• Perform utility energy use analysis by building type and size (building signature can be determined including energy use per unit area [to compare against typical indices]

Step 2: Walk-Through Survey

This step should identify potential energy savings measures. The results of this step are important since they determine if the building warrants any further energy auditing work. Some of the tasks involved in this step are

• Identify the customer’s 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)

Step 3: Baseline for Building Energy Use

The main purpose of this step is to develop a base-case model that represents the existing energy use and operating conditions for the building. This model will be used as a reference to estimate the energy savings due to appropriately selected energy conservation measures. The major tasks to be performed during this step are

• 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

Step 4: Evaluation of Energy-Saving Measures

In this step, a list of cost-effective energy conservation measures is determined using both energy savings and economic analysis. 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 by using the baseline energy use simulation model developed in Step 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)

Tables 4.6.1 and 4.6.2 provide summaries of the energy audit procedure recommended, respectively, for commercial buildings and for industrial facilities. Energy audits for thermal and electrical systems are separated since they are typically subject to different utility rates.

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About Gopal MishraVerified

Gopal Mishra is a Civil Engineer from NIT Calicut and has more than 10 years of experience in Civil Engineering and Construction. He is the founder of The Constructor.