Energy Audit

By Qazi Arsalan Hamid

What is Energy Audit?

An energy audit is key to developing an energy management program.

•data collection and review

•plant surveys and system measurements

•observation and review of operating practices

•data analysis

Systems Approach to Energy Auditing

• Define the system being considered

• Measure energy flows into and out of the system

•select convenient units of measurement that can be converted to one Unit

•know how to calculate the energy contained in material flows such as hot water to drain, cooled air to vent, intrinsic energy in processed materials, etc.

•know how to calculate heat from various precursor energy forms, such as electricity converted to heat through the operation of an electric motor

The macro-audit starts at a relatively high level in the structure of energy-consuming systems – perhaps the entire site or facility

The micro-audit, which has a narrower scope, often begins where the macro-audit ends and works through analysis to measure levels of greater detail

•Condition Survey

•Audit Mandate

•Audit Scope

•Analyze Energy Consumption

•Comparative Analysis

•Profile Energy use Pattern

•Inventory Energy Use

•Identify EMOs

•Assess the Cost and Benefit

•Report the Auditor Findings for Action

Initial walk through tour need to explore

•where energy is obviously being wasted

•where repair or maintenance work is needed

•where capital investment may be needed in order to improve energy efficiency

•Audit mandate – this should make the audit’s goals and objectives clear and outline the key constraints that will apply when the audit’s recommendations are implemented

Audit scope(Scope of Work) – the physical extent of the audit’s focus should be specified, and the kinds of information and analytical approaches that will comprise the auditor’s work should be identified

•Define the System to Be Audited

•Identify Energy Inputs and Outputs

•Identify Subsystems

Information in energy billings and cost records can lead to EMOs, especially when it is analysed with key energy use drivers such as production. You should analyse energy consumption and costs before comparing energy performance with internal and external benchmarks. Tabulating historical energy consumption records provides a summary of annual consumption at a glance. EMOs identified in this step may involve the reduction of energy consumption and/or cost, both of which are important outcomes.

•Purchased Energy Sources •Purchasing Electrical Energy •Tabulating Energy Purchase Data(Load Factor , Power Factor, Utilization Factor)

Percent of energy consumed relative to the maximum energy that could have been consumed if the maximum demand had been constantly maintained throughout the billing period

LF is inversely proportional to the average cost per kWh for similar facilities on the same rate

The utilization factor (UF) is the percent of use (occupancy, production, etc.) of a facility. For comparative purposes, it should be calculated over the same period of time as the electrical LF (24 hours, one week, one month, etc.)

•Internally – period to period, site to site and/or production unit to production unit

•Externally – to standards of performance established in the relevant industrial sub-sectors

STEPS

1. Tabulate Data(Identify Factors, Data analysis, Benchmark Comparison by Calculating Specific Energy Consumption(Specific Energy Consumption is the Ratio of Energy consumed to energy produced))

2. Internal Comparison by Energy Monitoring(determine when and why energy consumption is deviating from an established pattern )

•Collect and record

•Regression Analysis

•Cumulative Sum

•Target

The functional relationship between production and energy consumption can usually be determined by linear regression, i.e. by finding the best fit of a straight line using the least squares method to the plot of energy consumption vs. production.

CUSUM stands for “Cumulative SUM of differences,” where “differences” refers to the discrepancy between actual consumption and the consumption expected in light of an established pattern

•Performance Benchmarks

•Normalized Performance Indicator (NPI)

Specific Energy Consumption

This time record of energy consumption shows electrical loads operating at any time and the aggregate demand represented by those loads. In addition, a demand profile can reveal loads that are operating when they don’t need to be and identify systems that are inappropriately sized. Because the cost of electricity is determined in part by the maximum demand drawn, reducing that demand can significantly lower your energy costs.

Obtaining a Demand Profile

1. periodic utility meter readings2. recording clip-on ammeter measurements3. basic and multi-channel recording power meters4. facility energy management system 5. dedicated monitoring system

Making a list or inventory of all loads in a facility answers two important questions:

Where is the electricity used?

How much and how fast is electricity used in each category?

Match Usage to Requirement

Maximize System Efficiencies

Optimize the Energy Supply

Cost Considerations

Energy consumption can be reduced in two general ways:

1. changing the operation of the existing systems and equipment

2. changing the system or equipment technology

Benefits

•direct energy savings

•indirect energy savings

•comfort/productivity increases

•operating and maintenance cost reductions

•Environmental impact reduction

Costs

•direct implementation costs

•direct energy costs

•indirect energy costs

•operating and maintenance (O&M) cost increases

Know your Reader

Thank You