At certain times of the year, a California cogeneration plant relies on a money-saving supplemental system to cool its turbines.

Calpine Gilroy Cogen, LP of Gilroy, Calif., operates a cogeneration plant that supplies 120 MW to PG&E and provides steam to a nearby garlic plant. The plant uses chillers to cool turbine air regardless of ambient temperature, but running costs made it desirable to supplement its chillers with a cheaper system during certain times.

At first, Calpine tried media-type evaporative cooling, but water entered the airstream and fouled the compressor. As a result, turbines had to be washed regularly, the water pumps required extra maintenance, and media needed frequent replacement. Finally, the company decided to drop evaporative coolers, retain chillers and supplement with high-pressure fogging.

Calpine uses stainless steel supply pipes and pulsation dampeners to avoid pump vibration, now standard features on fogging systems, according to Mee Industries, Monrovia, Calif., a maker of humidification fogging systems. Calpine operates its thermal energy chillers during periods of peak power demand and otherwise relies on its fogging system. The cogeneration plant reduced its cooling costs after switching to high-pressure fog and realized a 3 to 6MW power increase.

For more information, contact Mee Industries at (626) 359-4550 or