Energy audit definition and process

Energy audit

Energy audit is the verification, monitoring and analysis of energy use in a plant, including submission of a technical report with recommendations for improving energy efficiency, together with cost-benefit analysis and an action plan to reduce energy consumption.

Process of carrying out an energy audit

Phase I – Pre-audit (planning)

1. Meet top management; decide scope, objectives, budget and time.
2. Form the audit team (electrical, mechanical, process staff).
3. Collect historical data: electricity and fuel bills (1–3 years), production data, single-line diagram, list of equipment with ratings.
4. Walk-through survey to understand the process and identify major energy users and obvious wastes.
5. Plan measurements and arrange instruments.

Phase II – Audit (execution) 6. Detailed measurements: power analyser (kW, kVA, pf, harmonics), clamp meters, lux meter, thermal camera, flue gas analyser, flow/pressure/temperature meters, ultrasonic leak detector. 7. Energy and material balance: find how much energy each section and equipment uses and the losses. 8. Compute specific energy consumption (kWh per unit product) and compare with benchmarks. 9. Identify energy conservation opportunities (ECOs): pf correction, efficient motors, VFDs, LED lighting, leak repair, waste heat recovery, load management. 10. Techno-economic analysis of each ECO: annual savings, investment, simple payback = investment/annual saving, NPV or IRR.

Phase III – Post-audit (implementation & follow-up) 11. Prepare the audit report: summary, present consumption, ECOs ranked as no-cost / low-cost / high-investment, action plan. 12. Present to management, implement selected measures. 13. Monitor and verify savings (M&V) and repeat the audit periodically.

 Pre-audit ──► Walk-through ──► Measurement
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 Report ◄── Cost-benefit ◄── Energy balance & ECOs
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     └──► Implementation ──► Monitoring & verification