Basics of Energy audit and its types
The primary objective of Energy Audit is to determine ways to reduce energy consumption per unit of product output or to lower operating costs. An energy audit can be defined as a systematic analysis of energy use and energy consumption within a defined energy audit scope, in order to identify, quantify and report on the opportunities for improved energy performance. Energy Audit provides a benchmark (or a reference point) for managing energy in the organization and provides the basis for planning a more effective use of energy throughout the organization.
The first step to an energy audit is evaluating how much energy is being used to identify the improvements that need to be made in order to increase energy efficiency. Only once the faults in the energy system are recognized, can they be corrected. Correction of issues observed in the audit leads to saving energy which ends up a decreased energy bill and improved efficiency.
Energy Audit can be classified into the following two types.
- Walkthrough Audit or preliminary audit: It involves a walk-through of the facility to become familiar with operation and to identify any glaring areas of energy waste or inefficiency. It is the simplest and quickest type of audit. 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.
- Detailed Audit: A comprehensive audit provides a detailed energy project implementation plan for a facility, since it evaluates all major energy using systems. Typically involves certain process or equipment level measurements using specialised instruments (described briefly in the next section) usually not available with the industry or facility being audited. This type of audit offers the most accurate estimate of energy savings and cost. It considers the interactive effects of all efficiency measures proposed, accounts for the energy use of all major equipment, and includes detailed energy cost saving calculations and cost of investment in energy efficiency. In a comprehensive audit, one of the key elements is the energy balance. This is based on an inventory of energy using systems, assumptions of current operating conditions and calculations of energy use. This estimated use is then compared to utility bill charges.
For the identification and quantification of energy usage and losses, measurements are required through audit instruments. Some of the commonly used energy audit instruments are mentioned in below.
| Flue Gas Analyzers
|Used for measuring/monitoring the oxygen and CO levels in flue gas of boilers, furnaces etc. – helpful in improving combustion efficiency||Used for measuring temperatures from a distance using infrared technology – helpful in determining energy loss|
|Used for measurement of flow of liquids through pipelines of various sizes through ultrasonic sensors mounted on the pipelines – helpful in determining pumping and cooling system efficiencies.||Used for measurement and analysis of electrical Power – very useful for multiple electrical system / equipment (e.g. motors) assessments.|
|Used for measurement of current without Interrupting the connections – like a power analyser but for quick and instantaneous measurements||Used for measurement of illumination level – helpful in optimising lighting loads.|
Energy Management System (ISO 50001)
In order to improve energy-related performance and energy efficiency continuously, rather than just a one-off audit, and to identify energy reduction opportunities, the establishment of an energy management system is required. An EnMS integrates energy active management into everyday business systems and procedures. The goal is to enable an organizations to better manage their energy usage, to achieved operating cost savings, and to continuously improve energy efficiency. So, this systematic approach will help organizations to establish systems and processes. ISO 50001 is an international standard for Energy Management Systems, created by the International Organization for Standardization (ISO). The standard specifies the requirements for establishing, implementing, maintaining and improving an energy management system, whose purpose is to enable an organization to follow a systematic approach in achieving continual improvement of energy performance, including energy efficiency, energy security, energy use and consumption.
ISO 50001 provides a framework of requirements for organizations to:
- Develop a policy for more efficient use of energy
- Fix targets and objectives to meet the policy
- Use data to better understand and make decisions about energy use
- Measure the results and Continually improve energy management.
Establishing an ISO 50001-certified EnMS may also help increase promote foreign investors’ confidence in company management.
Some of the best practice on energy efficiency that are commonly applicable are:
- Plug all air, steam and oil leakage. Compressed air is one of the most expensive forms of energy – do not waste it! Leakage of one drop of oil per second amounts to a loss of over 2000 litres/year
- Recover & utilize waste heat from furnace flue gases for preheating of combustion air. Every 21°C rise in combustion air temperature results in 1% fuel oil savings.
- Control excess air in furnaces. A 10% drop in excess air amounts to 1% saving of fuel in furnaces. For an annual consumption of 3000 kl. of furnace oil. This means a saving of 16.5 million MMK (Cost of furnace oil-550 MMK per litre).
- Reduce heat losses through furnace openings. Observations show that a furnace operating at a temperature of 1000°C having an open door (1500 mm * 750 mm) results in a fuel loss of 10 lit/hr. For a 4000 hrs. furnace operation this translates into a loss of approx. 21 million MMK per year!
- In Boiler operation, recover heat from steam condensate. For every 6°C rise in boiler feed water temperature through condense return, there is 1% saving in fuel.
- To improve boiler efficiency. Boilers should be monitored for flue gas losses, radiation losses, incomplete combustion, blow down losses, excess air etc. Proper control can decrease the consumption up to 20%
- Improve power factor by installing capacitors, it can reduce KVA demand charges and also line losses within plant
- Undertake regular energy audits to identify opportunities to conserve energy and implement measures to improve the situation. Consider installing an energy management system for continual improvement of energy performance.