Energy Auditing and Performance Assessment

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Energy audits are investigations of energy use in a defined area or site. They enable an identification of energy use and costs, from which energy cost and consumption control measures can be implemented and reviewed. Energy audits play an essential role in energy retrofit programmes by identifying areas with energy saving potential and provide the information needed in building performance assessment.
Energy audits vary in range and depth, and usually include the following steps:

  • Collect and analyse historical energy use.
  • Study the building and its operational characteristics.
  • Identify potential modifications that will reduce the energy use and/or cost.
  • Perform an engineering and economic analysis of potential modifications.
  • Prepare a rank-ordered list of appropriate modifications.
  • Prepare a report to document the analysis process and results.

The key elements of a commercial building energy audits/analysis are as follows: 1. Analysis of at least one year of utility consumption and cost, review of building plans, and a walk-through of the building itself to establish:

  • Type of building, principal use, and area.
  • Annual energy use.
  • Cost index.
  • Breakdown of various spaces within the building by function, hours of use, and area.
  • Determine if efficiency may be affected by building functions that differ from the original functional intent of the building.
  • Determine if any maintenance problems or practices may affect efficiency.
  • Assessment of a building’s energy cost and efficiency. Comparison of energy and cost indices of the building with one or more databases.
  • Identify and provide a savings and cost analysis of low-cost/no-cost measures.

2. Description and analysis of the energy-using systems of the building, resulting from on-site observation, measurement, and engineering calculations, including:

  • Envelope
  • Lighting
  • HVAC
  • Other systems

3. As a result of engineering analysis and economic calculations, develop:

  • Breakdown of the components of annual energy use and cost.
  • Recommended energy conservation measures, including predicted savings and implementation cost. Comparison of current recommendations to ultimate target.
  • A description and cost estimate of repairs that are needed to make energy conservation measures be effective.
  • A description and cost estimate of measurement and verification methods needed to determine the actual effectiveness of measures.

The engineering energy audit should also provide the owner/operator with all information needed to commit necessary resources to reduce the building’s energy use and/or cost. This includes outlining any changes in the facility’s operation and maintenance, including different personnel requirements, as well as presenting an economic analysis of any capital improvement projects. The engineering analyst is encouraged to follow a systematic approach in identifying, selecting, and ranking recommended measures. However, the appropriateness of a measure depends not only on technical issues but also on institutional and organizational issues, such as the regulatory environment, financing options, and occupant requirements. Therefore, a modification to a piece of equipment or an activity that is highly effective under some conditions may have little or no effect under others.

Simulation models
There are a number of studies that have highlighted the importance of energy audits in sustainable building retrofits,,. In those studies, it has been pointed out that retrofit technologies reflect new equipment, new energy resources, new energy audit technologies, etc. Since energy audits can help better understanding the energy performance of a building and its services systems, potential retrofit opportunities can be identified based on the information collected during energy audit. In order to reliably predict energy savings from a set of proposed retrofit measures, the parameters of the simulation models can be calibrated through the use of energy audit data.
A key piece in the sustainable building retrofitting analysis are the building performance simulation models. These models are set up in order to be aligned with the real energy consumption and obtain reliable performance assessments, used to benchmark building energy use, identify system operational problems, and find energy conservation opportunities. Several software are available for this purpose: Ansys Fluent, eQUEST, Therm, TRNSYS, EnergyPlus, MATLAB SIMULINK, etc. Further information about these tools can be found on the document “Appendix 9. Building performance assessment tools”.