Sub-metering – the time is right
May 1st 2004

With the relentless downward pressure on costs, liberally sprinkled with the constant threat of more competition from offshore lower-wage economies, UK manufacturing can ill afford to leave any stone unturned in the battle to become ever more efficient. This situation, combined with a sharpening of focus due to the Climate Change Levy and government backed publicity such as the Carbon Trust’s recent ‘lifeblood’ television campaign, has put energy efficiency firmly into the spotlight

Most manufacturing businesses are considerably more energy efficient than they were twenty years ago, and few have failed to embrace the relevant technology

High efficiency boilers and electric motors, variable speed drives and low energy lighting are just a few of the items contributing to lower energy consumption and stronger profits, but despite these improvements there are further substantial savings to be made without major additional investment. There are many ways to save energy on a factory site, but in fundamental terms if comes down to just two main issues: the plant itself – (the machines, equipment etc) and the way in which this plant is used – a crucially different matter

In the first category the nettle has been firmly grasped, as already discussed, by installing more efficient machinery, but in the second it seems there is some fear of getting stung, but in fact this is where the additional savings lie. At the risk of oversimplifying a complex subject, if we take standard 50kW electric motor and replace it with a high-efficiency 50kW motor it is reasonable to assume a predicted saving in energy consumption will occur, and all other things being equal, it will. That’s why high-efficiency plant is installed in the first place – it makes economic sense to do so. But what if our imaginary motor is motor, turned it off when it wasn’t needed, and as a result saved a lot more money

There are compressor motors (to name but one category) the length and breadth of the country that fall into this category

However, before I upset every motor manufacturer in the land, let’s be clear – energy efficient plant is indispensable in a competitive manufacturing environment but improving the way that plant is used can now offer huge savings for relatively low investment, and this is a nettle that can now be grasped without pain

The critical factor here is information

Not much can be done to manage a process in terms of energy efficiency without this priceless commodity

Continuing with the compressor example, unless the demand profile of the motor is known, and can be compared with the real requirement for air, the wasteful operation will continue. The answer (rather given away by the title of this piece) is sub-metering, but not, to quote a phrase, “as we know it”

Sub-metering is not at all new, and the logic behind it is plain enough, but with some historical justification it is still perceived by many to be expensive and unreliable – certainly hard to make a business case for. The truth, happily, is now rather different

Something clearly must have changed in the world of submetering for this to be the case, and indeed it has. In fact virtually everything has changed. The biggest difference is Automatic Meter Reading (AMR), that replaces daily or weekly manual reads with fully automatic reads every half an hour, generally displayed on a simple barchart. This changes the game completely, now consumption can be assessed not just in terms of “how much” but “how much” and “when”. If the compressors are still running after the shift has ended, AMR 30 minute data will show this immediately. Hey presto – instant saving! Even without this example (not as far fetched as you might think) it’s easy to see the potential of 30 minute or ‘interval’ data (to use the industry jargon) as a tool for eliminating waste. Modern sub-metering systems all offer AMR, along with a host of other improvements compared to the days of the clipboard and the weekly trudge round the site. In fact, the term ‘sub-metering’ sells such systems rather short, so the industry decided that a new name was needed which, after much discussion turned out to be ‘aM&T’ (automatic Monitoring & Targeting). This evolution has been achieved through better meters, better networking, better data acquisition and better software all of which combine to deliver a massively improved performance at ever lower first cost

New microelectronics has revolutionised the humble electricity meter, provided low cost radio transceivers and pulse data loggers as well as seamless links to existing systems and networking. This in turn makes both the hardware and the installation costs lower than ever before. Advances in software provide a user interface that includes alarms and exceptions reporting to actually help the operator to make savings quickly, and statistical analysis functions to maintain improved efficiency into the future. It all combines to make aM&T systems simple, effective, and above all, cheap to install

The overall result is that managing the way that plant is used, rather than simply ensuring that the plant itself is as efficient as it can reasonably be, is now substantially easier to do, and this can produce huge benefits. It is significant that while an energy-saving light bulb can reasonably be guaranteed to save energy, there is a well defined limit as to how much energy it can save. aM&T on the other hand, while achieving nothing on its own, is constrained by no such upper limit in the contribution it can make, if the information it provides is acted upon

aM&T may not be quite as simple as changing the proverbial light bulb, but the potential impact is far greater. Genuine savings of 3-5% are achieved on large sites according to the latest information from the Carbon Trust (much more on smaller sites) and the author has first hand experience of several locations where annual savings in excess of £50k have been realised virtually immediately through waste elimination

Whether the plant itself is state of the art or ‘getting on a bit’ makes no difference

All of it can be used more efficiently if an aM&T system is in place – and it’s not just the author that thinks so! Such systems were granted ‘ECA’ (Enhanced Capital Allowance) status in the 2003 budget, which equates to a 6% discount in real terms, which at least makes a believer of Mr Brown, but rather more importantly applies a badge of credibility to the product that cannot be obtained by any means other than proven performance.

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