Efficient motors reduce lifetime costs

Edited by the Engineeringtalk editorial team Jul 19, 2007

Andy Glover explains how WIMES specification high efficiency motors are reducing whole life costs in the water industry.

WIMES - the Water Industry Mechanical and Electrical Specification - is one of the key tools used by the UK water industry in its continuing drive to improve efficiency and reduce operating costs.

The UK water industry is one of the largest consumers of industrial electricity, due, in the main, to its wide use of pumping systems.

Some water companies have calculated that approximately 90% of their annual energy consumption is attributable to the pumping of water.

However, studies have shown that using higher efficiency drive systems could save 30% to 50% of this energy.

Originally introduced to reduce costs across the water industry by providing a common standard, WIMES is also a means of reducing the whole life costs of equipment such as low-voltage electric motors.

WIMES achieves this by specifying minimum criteria for features such as energy efficiency, power factor, build quality and environmental protection, all of which can affect a company's profitability.

The WIMES standard lays down minimum efficiencies for two, four, six and eight-pole electric motors at 3/4 and full load in the range from 1.1kW to 400kW.

The efficiencies it considers for two and four-pole motors in the range 1.1kW to 90kW are also the values determined by CEMEP, the European Committee of Manufacturers of Electric Machines and Power Electronics, for high-efficiency EFF1 motors.

Up to and including 90kW, on two and four-pole motors, CEMEP values are used for the purposes of determining enhanced capital allowances.

Over 90kW, or where energy efficiency for six and eight-pole motors (5.5-315kW) is concerned, then WIMES is the benchmark standard in the UK.

The importance of WIMES as a whole life cost reduction tool is clear when the ratio of the initial cost of low-voltage motors is compared to their operating costs.

It has been calculated that in high-use cases - and the water industry has many of these - the purchase cost of a LV motor can represent as little as 1% of the motor's lifetime cost.

The remaining 99% being attributable to the motor's energy consumption.

The supply of a highly efficient wastewater-pumping package, by Enegenica to Thames Water, is a good example of how the longer- term equipment policy encapsulated in WIMES is being actively applied in the water industry.

The Hidrostal pump and WEG W21 Premium Efficiency motor package replaced the original pumping facilities at Blake's Lock, on the banks of the River Kennet in the centre of Reading.

It has been supplied under a framework agreement that takes into account the whole life costs of the machinery; providing a high-quality pumping solution that has very low maintenance costs and a long service life.

The pumpset packages, weighing-in at over 4 tonnes each, comprise five 200kW, Premium Efficiency EFF1 WEG motors working in conjunction with Hidrostal energy-saving centrifugal screw impeller pumps.

The W21 WEG motors complement the screw centrifugal impeller design in the Hidrostal pumps, which offers high peak efficiency to minimise energy consumption, and also features an adjustable impeller clearance to maintain high operating efficiency over prolonged periods.

The impeller design also provides a patented solution to the problems of effectively handling bulky solids, sludge and slurries.

It features a single blade, axially extended at the inlet and developed around its axis, much like a corkscrew.

This arrangement results in an impeller, which will pass solids of 220mm diameter and inlet geometry optimised to handle rags and fibre without blockage; an important requirement on sewage pump stations like Blake's Lock.

The 200kW WEG Premium Efficiency motors used in the project meet the standards set by WIMES for six-pole electric motors, including quality standards and efficiency ratings.

As such, they each qualify for GBP 16,400 on installation, offsetting the capital cost of the project considerably.

The whole life cost of any equipment is the total "lifetime" cost to purchase, install, operate, maintain, and dispose of that equipment.

The components of a life cycle cost analysis typically include initial costs, installation and commissioning costs, energy costs, operation costs, maintenance and repair costs, down time costs, environmental costs, and decommissioning and disposal costs.