Energy Management
Take control when it comes to energy saving options
We are constantly being urged to fit inverter drives and save energy. But Jeff Whiting says we should not overlook their sister technology – controls.
Constantemente se insiste en que instalemos inversores y ahorremos energía. Pero Jeff Whiting señala que no deberíamos pasar por alto su tecnología hermana: la de controles.
Wir werden ständig angehalten, Frequenzumrichter-Antriebe einzubauen und Energie zu sparen. Doch sollten wir, so Jeff Whiting, nicht deren Schwestertechnologie vergessen: die Steuerung.
D
isciplines we learn in one field can sometimes be applied in other areas and yield really useful results. In recent weeks, for instance, I have been focused
on the latest Machinery Directive to identify some of the design requirement of industrial equipment to minimise risk and make the equipment safe. Te standard process is well defined and I feel that some of the assessment approach outlined could be modified and apply to minimising energy within our processes. BS EN ISO 14121 (Risk Assessment) encourages a three-stage process to safety. First, design out as many safety problems as possible; then those that cannot be removed through mechanical and control design are brought under control with a safety solution – a light curtain, guard or similar. Te final approach is through user information, such as instructions, limitations of use and training. Tis process is very sensible and in principle could be applied to energy engineering. Te assessment process would then become, to design out energy consumption where possible through the mechanical and control philosophy. Secondly to apply energy saving technologies such as inverter drives. Finally, to provide user information and training to minimise any other energy requirements that may require localised input. More and more people are
recognising the value of energy saving technologies, stage two
Fig. 1. A few well chosen sensors will say switch off empty conveyors, power down HMIs and lighting when there is nobody present, control temperatures to set levels.
in my analogy, but what about designing out unnecessary losses in the first place? When you think about it, many elements of a machine are left running for major parts of their duty cycle without any useful function taking place. In a lot of cases it would be possible to switch them off when they are not actually operating; powering them up just before they are actually needed.
Te main culprits for running unnecessarily include lights, fans and pumps. To this you can add HMIs and other unmanned display/control panels, possibly chillers or air conditioning, conveyors, etc. At first it may feel like the level of energy savings will not warrant the effort required. But some rough calculations on the back of an old envelope make well change your mind rather quickly.
When designing a machine engineers primarily think functionally: what are we making, how can we do that, what processes are involved? Energy considerations, where they are considered, usually come somewhere low down the list of goals. But it costs nothing to think about energy as an primary part of the project brief. If heat is involved, can a smaller amount be applied more accurately; if cooling is required, can this be done intermittently rather than constantly; can the length of conveyor runs be reduced; can conveyor speeds be slowed without impacting overall productivity; would reversing a plant’s layout change lifting operations into lowering ones; how many lights on the machine could be left off for long periods of time? Many of these questions could also be asked of existing machinery, but this brings up a universal problem. People generally don’t like change. Tey would rather muddle on as they are, using the well known mantra, “If it ain’t broke… Don’t fix it!”
Creative efforts are often reserved for things
perceived as new and exciting. People easily come up with also sorts of reasons for not undertaking
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