VSDs - still delivering the best energy-saving solutions
12 November 2013
Every day we see a new invention that promises greater energy efficiency. However, a big part of a genuine solution has been staring us in the face for more than two decades. Steve Brambley, deputy director of GAMBICA, explains how technologies that are already at our disposal, such as variable speed drives, can still deliver huge energy savings.
In the emerging low carbon economy, there are many voices suggesting different ways of keeping the energy supply secure and sustainable. As a result, the simple variable speed drive (VSD) message is in danger of being smothered by renewable energy debates, nuclear generation concerns, smart grids, feed-in tariffs and a pethora of blue-sky, out-of-the-box, wheel-reinventions.
There is no doubt that we need to develop sustainable forms of generation, whatever the source. In fact, developing new technology is fundamental to providing innovative solutions to the global energy problem. However, as well as finding ways to keep the lights on, we should start by turning lights off when are not needed. With the serious threat of energy rationing on the 10 year horizon in the UK, using less energy is a smart move from both a cost and continuity perspective.
Installing a variable speed drive on industrial motors remains one of the best and most straightforward ways of reducing energy usage, particularly when driving pumps and fans. VSDs can cut the energy bill on an application or system by more than their own capital cost in a relatively short period.
As electricity prices continue to rise, the return on investment (ROI) on a VSD application increases in proportion to the bill. Furthermore, because the cost of a VSD has actually remained stable over the last decade, payback can be more quickly achieved, often in less than a year.
To demonstrate this, GAMBICA has launched a simple calculator that estimates the energy savings that can be achieved. It comes in the form of a Microsoft Excel file and is available to download for free from GAMBICA’s website at www.gambica.org.uk.
Considering lifetime costs
It is worth remembering that 90% of the lifetime cost of an electric motor comes from its energy consumption. This can be illustrated by the fact that if just half of Britain’s electric motors were reduced in speed by 10%, it would have the net effect of mitigating for the carbon emissions of 9.8 million executive saloon cars every year.
So, the energy cost of a system should be the first thing a buying team looks for in a quote as it may well be the single item that most effects the bottom line over time. This is particularly true in process applications, where pumps and fans are widely used for liquid and air movement. Turning their speed down by 20% can translate to a 50% energy saving in a fan.
Energy consumption is exacerbated by the fact that motors are often over specified in process industries, so they can cope with worst case scenarios. Adding a VSD will not remove this ability to manage in extremes, it will just reduce its cost on a day to day basis.
The cost of energy is important, but its security and continuity is crucial for sectors such as oil, sewage or petrochemicals. Maintaining a reliable energy supply requires both businesses and individuals to consume less – and this is exactly what VSDs can help process companies achieve.
Recent EU regulations concerning energy efficiency should also play an important role in changing the way manufacturers think. The Eco-Design Directive, which was originally called the Energy Using Products Directive, for example, is a framework that sets minimum standards of efficiency for specific products. Since July 2011, there has been a requirement that motors must meet the IE2 standard. From 2015, motors from 7.5kW to 375kW must meet IE3. For a 1kW motor, roughly 8% of its input energy is saved by going from IE1 to IE2, and by going from IE1 to IE3, around 11% is saved. The typical efficiency of an IE2 1kW motor is 80%, while similarly sized IE3 motors exceed this significantly. The requirements will extend down to 0.75kW from 2017.
The June 2011 implementation has already raised the bar in terms of environmental and economical prerequisites. So it is reasonable to assume that the subsequent Directive developments planned for 2015 and 2017 will increase them further.
It must also be borne in mind that VSDs are not the panacea to all problems. They are not suitable for all types of motor applications, so engineers should always consult the GAMBICA website or other specialist resources provided by the supplier when specifying a VSD.
If you are part of a buying team, or working at management level for a process company that uses substantial amounts of energy, VSDs could be a viable solution for many motor applications. Do give them due consideration.
GAMBICA is the Trade Association for Instrumentation, Control, Automation and Laboratory Technology in the UK.
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