A common belief is that if plant is equipped with efficient machines it runs efficiently. Unfortunately, this is not always true.
Efficiency of components does not equate to efficiency of the whole plant.
Common reason for utility waste by efficient machines:
- Misuse: compressed air used instead of blowers or for cooling, oversized motors, excessive lighting/cooling/heating/ventilation
- Inadequate controls: broken, temporarily bypassed and forgotten, turned off, set incorrectly
- ‘Value-engineered installation’: pipes or ducts are too small or too short, pipes are scaled inside, connections leak
- Lack of maintenance: partial equipment failure is compensated by higher energy use
Here are several discoveries made during a utility audit at different manufacturing plants that used modern efficient equipment:
- Efficient boiler used 120% of water needed for production process due to uncontrolled overflows.
- Water chilled by an efficient chiller had to be reheated to meet technological requirements due to inadequate piping and controls
- Make up air supplied by efficient fans entered plant within 2 meters from exhaust intake – ducts were short, causing cool air to cycle. In winter people could literally see snowflakes flying from supply to exhaust.
- Rooftop AC unit run without coolant or with a broken belt – plenty of noise and energy use, but no cooling
- Efficient VFD air compressor struggled to keep up with demand because pipes were too small and network design was inadequate. Shortage of air caused high scrap rate.
- Industrial baking oven over baked bread and burned extra natural gas because thermal sensors were out of calibration
- Refrigeration compressor could not keep with cooling demand while trying to overcome ‘always on’ metal halide lighting within freezer
- Sprinkler system was connected after main valve – no utility waste here, but a fire code violation with risk of plant closure
In all these cases machines were modern and highly efficient. Although plant management believed that they run efficient operation, audit has uncovered recoverable energy waste.