Energy efficiency

Case studies

  1. Introduction
  2. Case studies from the United States Motor Challenge Program
  3. Case studies from the international CADDET database
  4. Australian case studies developed for Motor Solutions Online

Case studies from the United States Motor Challenge program

These case studies have been gathered by the United States Department of Energy, Office of Industry Technology.

Type of plant Annual cost savings (US) Payback
(years)		 Savings as per cent of initial electricity usage

Laboratory facility

 $823 000 1.9 6%

Petroleum refining

 $700 000 2.0 30%
Primary aluminium $103 736 0.0 12%
Strand board $85 100 1.0 50%

Steel production

 $542 600 2.3 50%
Coal processing $6 230 2.5 20%
Municipal sewage $2 960 5.4 17%
Beer brewing $19 000 0.1 52%
Metal fabrication $68 000 1.5 38%
Stainless steel tubing $77 266 0.5 34%

These case studies reveal that, based on instantaneous load measurements of nearly 2 000 motors operating under reportedly normal conditions, 44 per cent were operating at loads of less than 40 per cent. For pump, fan and other fluid systems, low loads indicate that the entire system is operating at far below optimal efficiency.

Of the three fluid applications analysed, air compressors are most consistently fully loaded, with only 15 per cent under-loaded. In comparision, 30 per cent of the fan systems and 39 per cent of the pump systems measured were under-loaded. The high percentage of under-loaded motors in pump and fan systems suggests that significant savings can be had in systems by adjusting the system and downsizing of the drive motors.

Example: 3M motor systems case study

The 3M project sought to optimise the electric motor systems at its corporate headquarters in Maplewood, Maryland. A cross-company team was formed to review and evaluate more than 1 000 electric motor systems to comply with 3M's Corporate Energy Policy which was to 'improve energy consumption efficiency, reduce cost, decrease capital investment, reduce environmental emissions, and conserve natural resources.'

Using a systems approach, 3M made many modifications and improvements throughout the corporate campus. In particular, the case study showcases four upgrade/improvement projects:

  1. upgrading the pilot plant air handling system using variable frequency drives (VFDs), energy-efficient motors, and a direct digital control system
  2. upgrading the reheat water supply system using feedback sensors and VFDs
  3. upgrading the supply air fans
  4. optimising various motor systems with energy-efficient motors, sheave changes, downsizing motors, and other system improvements.

The four projects resulted in annual energy and cost savings of 939 400 kWh (a reduction of 41 per cent and $31 583).

If applied to all the buildings at the 3M Centre, this performance optimisation is estimated to save 10 821 MWh annually and reduce demand by 468 kW. With estimated annual savings of $823 000 and a net project cost of $1.6 million, the projects would have a net payback of 1.8 years.

Nearly two-thirds of all potential systems savings derive from system efficiency measures, such as substituting adjustable speed drives for throttling valves or bypass loops in pumping systems, or fixing leaks in compressed air systems. The specific system efficiency measures for which savings were estimated differ for each major application category. Savings attributable to the major industrial fluid systems - pumps, fans, and air compressors - provide between 45 and 62 per cent of the total savings opportunities, taking into account low and high estimates.

3M case study at a glance:

More information on the United States Office of Industry Technology, including its Motor Challenge program, is online at: http://www.energy.gov/

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