Energy Audit is important for industries and benefits of Energy Audit

Increasingly in the last several decades, industrial energy audits have exploded as the demand to lower increasingly expensive energy costs and move towards a sustainable future have made energy audits greatly important. Their importance is magnified since energy spending is a major expense to industrial companies (energy spending accounts for ~ 20% of the average manufacturer’s expenses). This growing trend should only continue as energy costs continue to rise.

Here are some benefits conducting energy audit

  • Energy audits will evaluate your facility “as a whole”, their goal is not to evaluate single measures but to consider a wide range of available alternatives (Electrical, Mechanical, Envelope and Water).
  • The audit will not only inform you of opportunities but provide you with financial analysis. This will enable prioritization based on financial benefit and return on investment.
  • Provide you with solid, easy to understand technical information regarding the proposed energy conservation measures.
  • A good quality audit will analyze your historical energy use and find potential issues using statistical methods.
  • Provide you with emissions analysis to help you understand the benefits of your decisions from an environmental standpoint.
  • Understand where energy is used and which areas are worth focusing on the most (energy hogs).
  • Provide you with benchmark information to help you understand your energy use performance compared to others in your field and area.
  • The cost-benefit analysis of the audit report would help decision makers prioritize opportunities and evaluate them as investments. These indicators would include, rate of return, net present value, cash flow analysis and payback.

Types of Energy Audit

The type of industrial energy audit conducted depends on the function, size, and type of the industry, the depth to which the energy audit is needed, and the potential and magnitude of energy savings and cost reduction desired. Based on these criteria, an industrial energy audit and its types can be classified into two types: Preliminary Energy Audit (Walk-through Energy Audit) and a Detailed Energy Audit (Diagnostic Energy Audit).

    1. Preliminary Energy Audit (Walk-through audit): In a preliminary energy audit, readily-available data are mostly used for a simple analysis of energy use and performance of the plant. This type of audit does not require a lot of measurement and data collection. These audits take a relatively short time and the results are more general, providing common opportunities for energy efficiency. The economic analysis is typically limited to calculation of the simple payback period, or the time required paying back the initial capital investment through realized energy savings.
    2. Detailed Energy Audit (Diagnostic Energy Audit): For detailed (or diagnostic) energy audits, more detailed data and information are required. Measurements and a data inventory are usually conducted and different energy systems (pump, fan, compressed air, steam, process heating, etc.) are assessed in detail. Hence, the time required for this type of audit is longer than that of preliminary audits. The results of these audits are more comprehensive and useful since they give a more accurate picture of the energy performance of the plant and more specific recommendation for improvements. The economic analysis conducted for the efficiency measures recommended typically go beyond the simple payback period and usually include the calculation of an Internal Rate of Return (IRR), Net Present Value (NPV), and often also Life Cycle Cost (LCC).

Procedures involved in Energy Audit

Preparation for energy audit

  • Defining the audit criteria
  • Defining the audit scope
  • Selection of energy audit team
  • Making an audit plan
  • Preparing an audit checklist
  • Conducting the initial walk-through visit
  • Collecting energy bills and available data and information
  • Conducting the preliminary analysis

Analyzing energy bills

  • Electricity bills
  • Calculating electricity use per day (kWh/day)
  • Calculating the Load Factor (LF)
  • Natural gas bills
  • Coal and fuel oil bills
  • Graphical analysis of historical energy use

Inventory and measurement of energy use
The most common data measured during the auditing process are:

  • Liquid and gas fuel flows
  • Electrical measurements, such as the voltage, current intensity and power, as well as power factor
  • Temperatures of solid and liquid surfaces
  • Pressure of fluids in pipes, furnaces or vessels
  • Exhaust gases emissions (CO2, CO, O2 and smoke)
  • Relative humidity
  • Luminance levels
  • Electrical load inventory
  • Thermal energy use inventory
  • Energy system-specific measurements
  • Energy balance

Analyzing energy use and production patterns

  • Load/Demand profile
  • Scatter diagram for presenting the dynamics of the energy-production relationship
  • Interpretation of energy-production data pattern on a scatter diagram

Benchmarking and comparative energy performance analysis

Identifying energy efficiency and energy cost reduction opportunities

  • Electrical demand control
  • Cross-cutting energy-efficiency improvement options
  • Sector-specific energy-efficiency improvement opportunities for selected industrial sectors

Cost-benefit analysis of energy-efficiency opportunities

  • Life-cycle cost analysis (LCCA)
  • Life cycle cost (LCC) method
  • Net present value (NPV) method
  • Internal rate of return (IRR) method
  • Simple payback period (SPP) method

Preparing an energy audit report
Some key issues that should be kept in mind while writing an audit report are:

  • The audit report should be written in a way that provides suitable information to the potential readers of the report which could be the CEO or plant manager, the supervisor of engineering or maintenance, and the plant shift supervisor.
  • The audit report should be concise and precise and use direct language that is easy to understand.
  • Use more graphs rather than tables for the presentation of data, results and trends.
  • The recommendation section should be specific, clear and with adequate detail.
  • Assumptions made in the analysis should be explained clearly. How changes in the key assumptions can influence the results should also be explained. A sensitivity analysis is a very helpful tool for this.
  • The auditors should do their best to avoid mistakes and errors in the report especially in the results. Even a few errors could damage the credibility of the audit.
  • The energy audit report should be consistent in structure and terminology used.
  • The calculations made in the analysis work should be explained clearly.

Post-audit activities

  • Create an action plan for the implementation of energy-efficiency measures
  • Implement the action plan
  • Evaluate Progress