Power-saving motors

Written by fe Bureau | Updated: May 30 2011, 06:50am hrs
Electric motor-driven systems (EMDS) account for 43-46% of global electricity consumption and emit 6,040 megatonnes (Mt) of carbon. This is by far the largest source of electricity use, easily outstripping lighting, which takes up 19% of the worlds demand. Unless comprehensive and effective energy efficiency policy measures are put in place by 2030, energy consumption from electric motors will rise to 13,360 terawatt-hours (TWh) per year, and carbon emissions to 8,570 Mt per year, more than one-and-a-half times the US annual carbon emissions in 2008, says the International Energy Agency in a recent report.

End-users now spend $565 billion per year on electricity used in EDMS. By 2030, that could rise to almost 900 billion, says the report, 'Energy-efficiency policy opportunities for electric motor-driven systems', which is the first ever analysis of the energy consumption of EMDS by the global energy watchdog.

Electric motors are used in a wide range of industrial systems, other than in applications such as pumps and compressors in the commercial, residential, agricultural and transportation sectors. For example, motors are used in these sectors in heating, ventilating, air conditioning, fans, lifts, etc.

Electric motors and the systems they drive are the largest single electricity end-use. Huge energy efficiency potential was found untapped in EMDS-around 25% of EMDS electricity use could be saved cost-effectively, reducing total global electricity demand by about 10%.

The best available motors will typically save about 4% to 5% of energy consumption. Linking these motors with electromechanical solutions that are cost-optimised for the end-user will typically save another 15% to 25%. The potential exists to costeffectively improve energy efficiency of motor systems by roughly 20% to 30%, which would reduce total global electricity demand by about 10%.

Regulatory measures should not necessarily be confined to devices and components that directly consume power; policies could eventually target the large potential energy savings from improved energy performance of mechanical components such as gears and drive belts. Certain common technologies like worm drives and V-belts are fundamentally inefficient and could potentially be regulated out of the market in favour of more efficient options.

As some aspects of motor-system energy use do not lend themselves to simple regulatory approaches, softer policy measures can be beneficial. It is especially important to strengthen market awareness through educational efforts targeting multiple decision-making levelsOEM (original equipment manufacturer), system specifier, plant manager, energy manager and senior manager/executive level. This would include user-friendly technical assistance through enhanced technical standards, system specification and operational/energy management tools and services. There is also a need to better align fiscal and financial incentives throughout the value chain, which could be complemented by well-targetted economic assistance to encourage the uptake of energy-efficient EMDS.

To help realise the tremendous potential for cost-effective energy savings in electric motor-driven systems, governments should consider, as a first measure, adopting mandatory MEPS (minimum energy performance standards) for electric motors, in line with international best practices.

These standards should apply to as many types of electric motors as feasible, and be set at no lower than the least life-cycle cost. Even larger energy savings can be achieved by using VFDs (variable frequency drives), which dynamically match the output power of motor systems to the power demanded by the drive train.

Further savings can be achieved by using efficient transmission and gear systems, and by better sizing and management of electric motor-driven systems.