Energy Audit

The primary objective of Energy Audit is to determine ways to reduce energy consumption per unit of product output or to lower operating costs. Energy Audit provides a “bench-mark” (Reference point) for managing energy in the organization and also provides the basis for planning a more effective use of energy throughout the organization. It aims at:

• Identifying the quantity and cost of various energy inputs;
• Assessing the present pattern of energy consumption in different cost centers of operations;
• Relating energy inputs and production outputs;
• Identifying potential areas of thermal & electrical energy economics;
• Highlighting wastages in major areas;
• Fixing of energy saving potential targets for individual cost centers;
• Implementation of measures for energy conservation & realization of savings.

Types of Energy Audit

There are generally 3 types of energy audit:

• Preliminary Audit or Walk Through Energy Audit  (Level I)
• Detailed Energy Audit (Level II)
•  Investment Grade Energy Audit (Level III)

Preliminary or Walk Through Energy Audit

The preliminary or a walk-through energy; audit is the simplest and quickest type of audit. It involves minimal interviews with site-operating personnel, a brief review of facility utility bills and other operating data, and a walk-through of the facility to become familiar with the building operation and to identify any glaring areas of energy waste or inefficiency. Typically, only major problem areas will be covered during this type of audit. Corrective measures are briefly described, and quick estimates of implementation cost, potential operating cost savings, and simple payback periods are provided. A list of energy conservation measures (ECMs) or energy conservation opportunities ( ECOs) requiring further consideration is also provided. This level of detail, while not sufficient for reaching a final decision on implementing proposed measure, is adequate to prioritize energy-efficiency projects and to determine the need for a more detailed audit.

Detailed Energy Audit

The detailed energy audit expands on the preliminary audit by collecting more detailed information about facility operation and by performing a more detailed evaluation of energy conservation measures. Utility bills are collected for a 12 to 36 month period to allow the auditor to evaluate the facility’s energy demand rate structures and energy usage profiles. If interval meter data is available, the detailed energy profiles that such data makes possible will typically be analyzed for signs of energy waste. Additional metering of specific energy-consuming systems is often performed to supplement utility data. In-depth interviews with facility operating personnel are conducted to provide a better understanding of major energy consuming systems and to gain insight into short and longer term energy consumption patterns i.e. insight into variations in daily and annual energy consumption and demand. This type of audit will be able to identify all energy-conservation measures appropriate for the facility, given its operating parameters. A detailed financial analysis is performed for each measure based on detailed implementation cost estimates; site-specific operating cost savings, and the customer’s investment criteria. Sufficient detail is provided to justify project implementation.

Identification of Energy Conservation Measure

In medium and big sized industries in Bangladesh, there are opportunities in improving energy efficiency and implementing energy conservation measures in the following fields:

Steam System: Identifying efficiency opportunities in steam generation in the boilers, controlling excess air combustion in boilers, insulation of steam lines & steam using equipment, stoppage of steam leaks, installation of steam traps, condensate recovery etc.

Energy Generation: Identifying efficiency opportunities in energy conversion equipment/utility such as captive power generation, optimal loading of DG sets, optimizing existing efficiencies, efficient energy conversion equipment, Co-generation etc.

Energy Distribution: Identifying efficiency opportunities in transformers, cables, switchgears and power factor improvement in electrical system, chilled water, cooling water, hot water, compressed air etc.

Energy Usage by processes: This is where there are some major opportunity for improvement and many of them are hidden. Process analysis is useful tool for process integration measures.

Fuel substitution: Identifying the appropriate fuel for efficient energy conversion and also sometimes cost savings.   

Technical and Economic feasibility: The technical feasibility should address the following issues

• Technology availability, space, skilled manpower, reliability, service etc.

• The impact of energy efficiency measure on safety, quality, production or process.

• The maintenance requirements and spares availability

The Economic viability often becomes the key parameter for the management acceptance. The economic analysis can be conducted by using a variety of methods. Example: Pay back method, Internal Rate of Return method, Net Present Value method etc. For low investment short duration measures, which have attractive economic viability, simplest of the methods, payback is usually sufficient.

Classification of Energy Conservation Measures

Based on energy audit and analyses of the plant, a number of potential energy saving projects may be identified. These may be classified into three categories:

1. Low cost – high return

2. Medium cost – medium return

3. High cost – high return

Normally the low cost – high return projects receive the highest priority. Other projects have to be analyzed, engineered and budgeted for implementation in a phased manner.  Projects relating to energy cascading and process changes almost always involve high costs coupled with high returns, and may require careful scrutiny before funds can be committed. These projects are generally complex and may require long lead times before they can be implemented.

Scope of Audit:

Energy audit can be done on a wide range of systems including but not limited to:

• Building envelope
• HVAC & Chiller system
• Electrical supply system
• Lighting
• Boiler and steam system
• Hot water system
• Compressed air system
• Motors and drives
• Special purpose process equipment

The scope of the audit will depend upon the nature of the business and the goals that clients want to accomplish.