Why a piecemeal approach to energy saving is not enough.

Whatever the scenario, maximum energy efficiency comes from taking a view of the complete picture. In industry, senior management and plant engineers must learn to talk if comprehensive energy efficiency is to be achieved. In no other sector is the communication gap wider than between those charged with making energy decisions in industry, and those who actually know how energy can be saved.

Responsible equipment manufacturers are continually developing more efficient products. However, while for the most part the efficiency of the equipment is a fair representation of its energy saving potential – say, in the example of a domestic washing machine or refrigerator – it is not always the case in industrial and commercial equipment.

In many cases the overall energy performance of the system is what really counts. Put simply, if an energy saving device is left permanently on stand-by it can be less efficient than a higher consuming device that is always switched off when not in use.

Holistic approach

It is also important that all the elements in a system combine to bring about the maximum energy efficiency possible. For example, it is well understood that energy efficient (Eff-1) AC electric motors save significant amounts of energy. Some argue that such efficient motors are more expensive, but the purchase price of such equipment is a very small part of the true costs. For example, the lifetime energy costs in running an Eff-1 or lower rated AC motor is often 100 times its purchase price over a lifetime expectancy of 13 years (average). An 11kW motor costing perhaps 400 euros to buy can consume in its lifetime up to 80,000 euros at current electricity prices.

But, once coupled with a variable speed drive (AC inverter) savings can be multiplied many fold. Indeed, savings are typically three times greater for a high efficiency motor fitted with a VSD rather than using ordinary fixed speed starters. Adopting Eff-1 motors can be considered a passive response to energy efficiency, while using VSDs represents an active approach.

Managing energy in industry

Energy intensive industries such as metals manufacturing, glass and plastics processing and food and beverage production understand the need for energy management because their processes involve great amounts of heat. These businesses have traditionally sought ways to maximise their return on investment from the energy used in their primary processes. However, even these energy aware businesses often fail to realise how much more can be saved through building controls and a company-wide energy policy.

All industries can benefit from energy policy, but it must extend beyond the production environment and into every aspect of the sites. Offices, for example, stand to save just as much as in the commercial sector.

While in many countries industrial energy use has now been slightly outweighed by that consumed by commercial and residential buildings, it is a fact that industry consumes huge amounts of electrical power. About two thirds of that is typically consumed powering electric motors. Of these, an overwhelming majority can be made significantly more energy efficient by controlling their switching on and off or by controlling their speed.

This is a relatively simple task of equipment retrofitting, yet it is clear that most manufacturing and process plants fail to take the step. The reason is often because those that control the costs of an industrial operation are not communicating with those charged with the management of the production processes.

For example, if a painting plant uses hundreds of AC motors on fans, pumps and compressors (continuous duty applications) it could readily benefit from the use of variable speed drives. However, while the plant manager, as an engineer, understands this, he or she is invariable responsible only for improving productivity or output and not for the overhead costs. Higher management is concerned with paying the overheads but remains unaware that such a saving could be made because it is never on the agenda in engineering meetings.

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