Energy audit
An energy audit is a systematic evaluation of energy flows and consumption within a building, process, or facility, aiming to identify opportunities for energy conservation and enhance overall efficiency. This process is crucial as energy costs represent a significant portion of operational expenses for both industrial and commercial entities. By pinpointing wasteful energy practices, an energy audit serves as a foundational tool for energy management, helping organizations to devise effective strategies for reducing energy use without compromising productivity.
The audit process can vary in complexity, ranging from a simple walkthrough to comprehensive assessments that include detailed analysis and suggestions for improvement. Typically, energy audits are categorized into three levels: the preliminary assessment identifies low-cost conservation measures; the comprehensive assessment provides a deeper analysis for developing energy efficiency programs; and the investment-grade audit offers a thorough examination of capital-intensive solutions, complete with financial implications.
Post-audit, benchmarking is utilized to compare a facility's energy performance against similar establishments or historical data, aiding in the evaluation of its operational efficiency. Successful implementation of audit recommendations relies on careful planning and maintenance, ensuring that projected energy savings are realized and sustained over time.
Subject Terms
Energy audit
Summary: An energy audit is one of the components of an energy management program, providing the information necessary to improve the efficiency of a process or system, which in turn lowers operating costs.
An energy audit is an analysis and evaluation of energy flows and consumption in a building, process, or facility. It is done in order to estimate the amount of energy that can be conserved in the input without affecting the output. In industry as well as commercial establishments, energy costs rank among the top operating costs. Energy audits identify wasteful uses of energy and possible options for improvement. Energy audits also provide a baseline, or reference point, for managing energy, which can serve as a basis for effective planning of energy use in the organization.
Performing an Energy Audit
An energy audit can range from a simple walkthrough of the plant or establishment to identify major areas of energy consumption (called a walkthrough audit) to a detailed analysis of a facility’s energy consumption with suggestions for measures to improve energy efficiency (an investment-grade audit).
It is important that before undertaking an energy audit, the owners of the building or facility identify their requirements. The first step is to determine whether to conduct the audit itself. Various factors qualify a facility for an energy audit. A series of self-evaluation questions will help owners understand what prompts the need for an energy audit.
The next stage is to collect data about the facility. Some of the important parameters to consider include the facility’s area (built-up area, carpeted area), load (in kilowatts) and demand (in kilovolt-amperes), installed capacity, annual electricity consumption (as purchased from utilities in kilowatt-hours), annual electricity consumption through diesel generating (DG) sets (in kilowatt-hours), annual cost of electricity purchased from utilities, annual cost of electricity generated through DG sets, lighting load (in kilowatts), peak load experienced, and installed capacity of the air-conditioning system.
The next step in the preliminary assessment is to ascertain which level of assessment is required for the facility. Energy service companies (ESCOs) provide a few questionnaires for building and plant owners to state their requirements. There are three levels of energy assessment. Each level is designed to meet the specific needs of the building or facility owner and has different requirement for resources and expertise. They are broadly classified as the following:
• Level I assessment: Also known as preliminary energy assessment, this is a simple assessment of the building’s energy efficiency to identify low-cost energy conservation measures. A baseline for energy consumption is created based on the previous months’ or years’ records. The primary activities in this type of assessment consist of physical inspection of the facility’s equipment, analysis of records of previous years’ energy consumption, and determination of the patterns in the facility’s energy use. Another important activity is to interview building staff and operators, which can provide important information for this and later assessment stages.
• Level II assessment: Also known as a comprehensive energy assessment, this is done in order to provide the owner of a facility detailed information to develop an energy efficiency program. It is a more detailed analysis of the facility to study all energy-saving measures and opportunities. The activities involved in this phase include studying building plans and facility equipment. This level is meant to identify major opportunities for energy conservation that can be incorporated into an energy conservation program. This level of analysis involves onsite measurements and can include computer simulations to evaluate energy consumption and potential savings.
• Level III assessment: Also known as an investment-grade audit, this consists of a detailed analysis of capital-intensive measures. It is used to give the owners information on the costs and benefits in implementing energy conservation measures, allowing them to make an informed decision on the measures identified in Level II. A detailed financial analysis of the energy conservation measure is conducted, often along with an energy service company (ESCO).
It is important to note that each level is inclusive of the previous levels. Therefore, a building owner performing a Level II assessment is utilizing the results of the Level I assessment as well, and the results of a Level III assessment incorporate the results of the first two assessments.
Benchmarking and Postassessment
Benchmarking of a facility’s energy use is a tool for comparison of a facility’s operation with similar facilities’ operations or over a time interval. Benchmarking, or establishing a baseline, is important from the point of view that it helps the owner ascertain the operating efficiency of the facility, whether it falls into an acceptable or unacceptable region of energy efficiency. It is a normalization exercise done to categorize all situations that might be encountered. The benchmarking of a facility is an important factor in determining whether further analysis is required. External benchmarking is done with data from various similar units, whereas internal benchmarking is done with past data and records of the concerned facility’s energy use.
Some of the data collected in conducting external benchmarking are the capacity of the plant or facility, the composition of raw materials and products, and the level of technology. In an internal audit, by contrast, the data normally collected include historical energy consumption, energy consumption by individual units, and trends in consumption.
Postassessment plans primarily include implementation of the recommendations of the assessment. Changes might be needed in the implementation, depending on the progress of the plan and feedback from the implementation team. The plan might be reevaluated based on changing requirements. The actual work could be carried out with the help of an ESCO, depending upon the capabilities of the organization housed by the plant or facility. Other aspects of the postassessment period are maintenance of the facility and verification of energy savings. Maintenance of the energy efficiency measures is important, for it ensures the predicted energy savings. Verification of energy savings is important in energy efficiency projects, since the energy savings must recover the capital costs incurred during the project or repay a loan from a financial institution. If an ESCO has been contracted, verification is generally a part of the ESCO contract.
Bibliography
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Krarti, Moncef. Energy Audit of Building Systems: An Engineering Approach. Boca Raton, FL: CRC Press, 2010.
Lawrence Berkeley National Laboratory. Industrial Energy Audit Guidebook: Guidelines for Conducting an Energy Audit in Industrial Facilities. Oak Ridge, TN: Office of Scientific and Technical Information, U.S. Dept. of Energy, 2010.
Maharjan, Indra K. Demand Side Management: Load Management, Load Profiling, Load Shifting, Residential and Industrial Consumer, Energy Audit, Reliability, Urban, Semi-Urban and Rural Setting. Saarbrücken, Germany: LAP Lambert, 2010.
"Professional Home Energy Assessments." Energy.gov, US Dept. of Energy, www.energy.gov/energysaver/professional-home-energy-assessments. Accessed 9 Aug. 2024.