Switching On the On-site Power
Staff -- Consulting-Specifying Engineer, 2/1/2003 1:00:00 AM
From the late 1980s into the early 1990s, Kuntz Electroplating, Kitchener, Ontario, saw its electricity costs rise rapidly. In fact, the company experienced as many as 15 utility power outages per year.
A power event lasting only seconds was long enough to stop electroplating production for an hour. After each outage, solution pumps had to be restarted and effective filtration re-established before plating could resume.
Lower cost, higher reliability
Founded in 1948 and employing more than 700 people, Kuntz operates one of North America's largest and most diverse polishing and plating facilities for steel and aluminum wheels, bumpers and other motor vehicle components. The firm's plant, which operates for two 12-hour shifts six days per week, creates a continuous 6.5-megawatt (MW) electric power demand.
Beginning in the late '80s, the local electric utility began raising its rates by up to 10% per year. Also, Kuntz was expanding and was about to be classified as a "large user," which would have increased the company's rates even more.
Company management began investigating on-site power generating systems. Considering fluctuating natural gas and electricity prices, a natural-gas-fueled cogeneration system was selected as it would also produce steam for process heating.
On-site power solution
Kuntz engineers decided on a system that incorporates five heat-recovery-equipped engine-driven generator sets with a combined capacity of 4.075 MW. Operating around the clock and providing electricity for 600,000 sq. ft. of production space and process heat for parts-cleaning and electroplating tanks, the gen sets also deliver quality power, minimizing voltage fluctuations that used to damage solid-state rectifier controls.
The company selected the gensets primarily for the availability of high-temperature, solid-water, ebullient cooling systems able to produce low-pressure steam for process heating. In such systems, engine jacket water circulates under pressure at 260° F, and engine cooling is accomplished by using the heat of vaporization. The hot engine-jacket water is flashed to steam by releasing the pressure from the water in the heat-recovery vessel. This form of heat recovery is simple and inexpensive, as it eliminates the radiator and allows recovery of virtually all engine heat rejected to the jacket water.
The gensets together produce continuous 13,800-volt, three-phase power in parallel with the utility grid. When operating at rated load, the units carry roughly 65% of total plant electric load.
The gensets are configured to ensure process continuity regardless of events on the utility grid. In case of utility power interruption, the control switchgear is configured so that non-critical plant loads are shed while the gensets operate the critical process loads in an island mode, isolated from the grid. When utility power is restored, the gensets automatically resynchronize with the grid and the utility breaker closes.
The company reports the equipment has achieved 98% to 99% reliability. The engines on the original three units have recorded 43,000 operating hours each, yet have required only one top-end overhaul per unit and no major overhauls.
Kuntz originally projected a 5- to 5.5-year simple payback, but actual payback is now projected at six years, as utility rates have remained level since 1994, and gas prices have increased somewhat more rapidly than projected. The payback calculations do not include the economic benefits of eliminating process downtime caused by outages and power quality concerns.
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