Feature Energy management

To save more energy, look at the whole story

If you really want to minimise your energy usage, adopting a piecemeal approach simply isn’t good enough, says

Phil George of Eaton’s Electrical Sector, you have to

consider your plant as a whole - an approach that is increasingly being referred to as powerchain management

tional essential energy information via a communications network. Monitoring currents directly from

motor circuit breakers, conveniently connected via the Darwin network, show up inefficiencies in the mechan- ics such as motor bearing wear. With the information gathered, a detailed utility consumption analysis can be drawn which paves the way for accu- rately targeting energy saving measures.

Step two

F

it a variable speed drive to one of your air conditioning fans and a time switch to the lights in your car park and you’ll certainly get

energy savings. Rather than pat your- self on the back and bask in the glory of a job well done, however, you should be asking how much more energy you could save if you looked at the whole of your plant and took advantage of all the opportunities that exist for improving efficiency and reducing losses. That may sound like a daunting

task, but the truth is that with the aid of modern technology, it’s not so diffi- cult. In fact, it’s a process with just three steps.

Step one

Firstly, as with all efficient automation systems, it all starts with precise sens- ing and measurement devices to give accurate information on system status. This status information, for example knowing that loaves are ready to be baked, will be useful later. If the infor- mation doesn’t exist within the system already, it’s possible to install addi- tional remote inputs and outputs (I/O) such as Eaton’s XION product, conve- niently located next to the plant or meters to be measured, then connected via an existing Ethernet network. Reading kWh information from drives and multifunction meters, such as those in the Powerware Series Power Xpert range from Eaton, provide addi-

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Unless your plant was designed with energy efficiency in mind, there will be numerous opportu- nities for reducing energy usage

INSET: Phil George of Eaton’s Electrical Sector

Monitoring currents directly from motor circuit breakers will show up inefficien- cies in the mechan- ics such as motor bearing wear

The second step is to implement effec- tive control and maintenance. In truth, a lot of energy really is just wasted. It’s still common, for example, to see ovens operating at working tempera- ture even when there is no demand for product to be baked. Additionally plant maintenance can slip, creating an increasing demand for power, to overcome wear in such things as gear- boxes and motors. Fitting variable speed drives, especially to fans and pumps is another measure that has the potential to deliver large energy sav- ings. In the ‘bad old days’ when no one cared much about energy consump- tion, it was common practice to fit an on/off starter to all motors, the motor was either stopped or it was running at full speed. This can be very wasteful when a motor is oversized or sized for the worst case. A fan on a process refrigeration condenser, for example, may only really need to run at full speed for the few hottest days of the year, so for the rest of the time it’s using more energy than it should be. And it’s not just a small amount of

energy that’s being wasted. The energy consumed by a fan motor varies as the cube of the speed, so a fan running at half speed consumes only one-eighth of the energy of the same fan running at full speed. A bonus is that modern variable speed drives like Eaton’s Moeller series of M-Max units are easy to fit. They’re compact self-contained units easily accommodated in existing control panels.

Step three

The third step is to close the loop by recording and distributing energy saving information amongst production and energy managers. Eaton’s Moeller series of XV and XP HMI’s and Industrial PCs can be added to existing fieldbus or Industrial Ethernet networks within the plant. Files can be created by these devices that can be sent by e-mail directly to specific people. It is then easy to use these automatic reports to confirm savings and make a case for fur- ther savings to be made. To summarise, unless your plant

was designed with energy efficiency in mind, there will be numerous oppor- tunities for reducing energy usage, often with surprisingly little effort and expenditure. To find and address these opportunities remember to look at your whole plant, and to follow the three steps outlined in this article: monitor and measure plant status and energy usage, improve control strate- gies and report results by specifying modern equipment that’s intrinsically energy efficient.

Eaton Electrical Group T: 0161 655 8900 www.eaton.com/uk

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