Energy efficiency rules
With EU legislation on the efficiency of electric motors starting to come into effect, and continuing to do so for the next six years, we look at the implications for pumps
Electric motors are huge users of electrical power throughout the EU, with a total consumption of 1067 TWh (T is tera, 1012, or a mega-mega). Energy-efficient motors such as those enshrined in EU legislation can make a sizable dent in that figure, with eco-design legislation estimated to achieve annual savings of 135 TWh by 2020, 12.7%. That huge figure is equivalent to the annual electrical consumption of a country like Sweden.
A large slice of that energy is used by pumps, as we discovered from David Considine, technical product manager with Grundfos Pumps. He explains that motors are responsible for 30% of electrical power consumption in the EU and that 20% of those motors drive pumps.
Industry is the biggest user of energy for pumps at 163 TWh. The tertiary sector uses 46 TWh a year and the domestic sector 50 TWh — a total of 259 TWh.
As part of the EU’s Energy Using Products Directive long-term goal to reduce the EU’s electrical consumption by 5%, there is a focus on electric motors, with a timetable for using more efficient motors.
The first stage was 16 June 2011, with a requirement for all electric motors meeting the IE2 efficiency level.
There have been standards for the efficiency of electric motors for 15 years, initially expressed as EFF classes and more recently in the context of EU legislation as IE classes.
The old method of measuring energy efficiency dates from an IEC standard of 1996 and defined three levels of efficiency. The least efficient was EFF3, working up through EFF2 to EFF1 as the best.
With motors continuing to become more efficient, a new method of measuring their efficiency was devised based on the 2007 update of the IEC standard. The numbering sequence has been reversed to give the possibility of adding more classes later, but probably not many more as the efficiency of motors, like much other equipment used in building-services engineering, is well over 90% — especially for larger motors.
The least efficient motors in the new scheme are Class IE1, rising through IE2 and peaking with IE3. An approximate comparison is the EFF2 corresponds to IE1 and EFF1 corresponds to IE2 — but the test methods are different so there is not a direct comparison.
The next key date for implementing more efficient motors in the EU is 1 January 2015, when electric motors from 7.5 to 375 kW will meet IE3, or IE2 if they have a variable-frequency drive.
The final date is 1 January 2017, with the requirements extending down to motors of 750 W.
But there is much more to achieving energy efficiency in practice than simply specifying energy-efficient products. Indeed, more energy can be saved by less-efficient products installed into efficient systems that are effectively controlled. That much is recognised in the regulations, which require only IE3 motors to be used from 2015 or IE2 if combined with a variable-speed drive.
Grundfos, however, makes no such compromise and is ready now with the first IE3 motors — over three years ahead of the legislative requirement — and will have a full range of IE3 motors by January 2012.
The company has long supported the concept of energy-efficiency for pumps. A notable initiative is its active support of the creation of the European energy-labelling scheme for domestic-heating circulators, which was introduced in 2005.
This scheme follows the familiar A to G labelling, with A being the most efficient and G the least efficient. There are still 100 million D-labelled circulators installed in Europe and they use up to five times more energy than A-labelled circulators. There is the further suggestion that an A-rated circulator will enable the average European household to reduce its total electricity consumption by up to 10%.
If you like big numbers, the introduction of A-rated circulators by Grundfos four years ago has helped to create an annual energy saving of over 536 GWh.
However, the potential energy savings from motors that are more efficient is falling off. The improvement from IE1 to IE2 is eight percentage points for smaller motors and less for larger motors. The improvement from IE2 to IE3 is only two to three percentage points. There is a further gain with IE3, however, in that their efficiency with pumps is maintained as the flow is reduced.
So, as in every other area of building-services engineering, the key is to use efficient products in efficient systems — and pumps are no exception.
Reflect on these three facts from David Considine.
• 90% of pumps could be more efficient.
• Most pumps only need to run at full speed 5% of the time.
• Two thirds of pumps could save 60% of energy with a variable-frequency drive.
At full load, inverter drives reduce the efficiency of a pump by 3 to 4%, but almost as soon as the frequency is reduced to slow the speed of the pump overall savings are made. Indeed, the extra cost of a variable-speed drive can be repaid in 18 months by energy savings, with the further benefit that the control elements of a system will function better.
Underpinning Grundfos’s response to European legislation is its Blueflux technology for motors from 750 W to 375 kW, all of which will be available from January 2012, three years ahead of legislation for motors above 7.5 kW and five years ahead for motors down to 750 W. Pumps with these energy-efficient motors do not cost more, as Grundfos is absorbing the extra cost.
Blueflux motors and variable-speed drives are designed to operate with each other, and both are specifically designed for pumps.
There is considerable potential for variable-speed drives. ‘VSDs are now almost standard on large building-services projects,’ says David Considine, ‘ but they ought to be more widely applied. Currently 25 to 30% of pump motors have VSDs — but the proportion ought to be much higher.
‘Variable-speed drives give the ability to reduce the energy consumption of pumps. The key is understanding how to use them to save energy. M&E engineers and system designers need to understand this so they can design systems that are capable of benefiting from variable-speed drives.
‘Variable-speed drives are much more important than the efficiency of the pump motor in reducing energy consumption, but the legislation is primarily directed at motor efficiency.’