The purpose of an energy audit is to reduce operating costs by reducing energy consumption and the government has estimated that most companies can reduce their energy consumption by 10% to 20%. Energy audits carried out by BPMA members have shown that savings from 30 to 50% are not unusual.With the Climate Change Levy increasing most companies' energy costs by 13% or more, energy efficiency is even more important now than it was in the past. Experience shows that these savings are usually best achieved by performing an energy audit.

When deciding whether or not to carry out an energy audit a good starting point is to assume that you will save at least 10% of your current energy consumption. By reviewing Utility bills you can get an indication of the savings to be made and investment that you should be prepared to put into the auditing process.

In most industrial sites about two-thirds of the energy is consumed by electric motors. In its lifetime the cost of energy consumed by an electric motor may be 100 times its purchase cost. So the reduction of losses in the motor itself is very important and modern electric motor design can reduce the energy loss in the motor by up to 30%. Many pumps and motors are operated at full power constantly, irrespective of process needs, and in some sites this offers the potential of large cost reductions. It is also frequently true that power factor correction equipment does not adequately compensate for inductive loads at all times. In some energy supply agreements surcharges arise from poor power factor correction.

An energy audit will identify all these issues and calculate the potential savings to be made. An energy audit is a significant investment and many manhours will be needed to find out where energy is being consumed in a building, production plant or utility facility. It is important that a thorough log of consumptions on each spur is made because excessive energy is sometimes used in the most unlikely places. In the case of fluctuating work or process loads, the monitoring of each energy consuming piece of plant may require several days to complete.

An energy audit should identify the savings to be made by resizing or retrofitting pumps which are operating away from their best efficiency point or the savings to be made by installing variable speed motors in place of motors driven at full power irrespective of need. A good energy audit will calculate from the process requirements what energy consumption should be needed and compare this with actual energy consumption. By ensuring that every pump and motor is working at the maximum efficiency great savings can be made.

To carry out an audit, the performance data for the equipment as originally supplied will be required or alternately published manufacturers curves. In some cases there may not be a list of pumps installed and an initial walk through will be required to identify these. Many pumps have name plates so data from these should be recorded. Determining actual flows and pressures can sometimes be difficult where pressure gauges and flowmeters are not fitted and power readings on site can often be inaccurate. However the variations from the originally specified duty is usually so large that estimated actual performance from data that is available is often sufficient to guide actions for energy reduction. Saving Energy may be as simple as turning a pump off rather than recycling flow. The cost of trimming a pump Impeller instead of throttling can be recovered in a few days.

For large pumps where the savings can be very high, it is often worth employing a specialist who can install temporary instrumentation to accurately measure performance with the cost of this being quickly repaid.

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