Las Vegas Cogen Slashes Cooling Costs and Boosts Output by 5 MW with MeeFog Technology

Installation Specifications:

As well as being upstream of the chiller coil, the fog system was positioned upstream of the air filters. The main advantage of this positioning was that installation could be accomplished without outage time.

“As it takes time for our chillers to get online, we also use high-pressure inlet fogging of demineralized water to achieve maximum power right away,” said RD Dawkins, Operations Supervisor, Las Vegas Cogen. “We use fog exclusively when we first start our combustion turbine and also when it’s below 70 degrees outside. Above that, we also bring on a steam absorption chiller in combination, and the fogging system eliminates the need for a second chiller.”

The fog system consists of 240 nozzles installed in three stages. Operating pressure is 2,000 psi, fog water flow rate is 10.8 gpm and a total of three 5 hp high-pressure pump units were installed. Pressure drop associated with the fog nozzle manifold was nominal. The existing heating coil and pad-type pre-filters were used as fog droplet filters to remove any unevaporated fog. Although this prevented wetting of the primary air filters, water collected on the cooling coil and pre-filter and was drained off, reducing the amount of cooling accomplished by the fog system.

“The MeeFog system is low maintenance and very reliable,” said Dawkins. “Even though our fog system is upsteam of the filters, our final barrier filters remain dry and the filters stay cleaner due to the scrubbing effects of the fog.”

Results:

Las Vegas Cogen found it far more economical to exclusively use fog under certain conditions. When the outside temperature is below 70°F fog alone is used for cooling. If temperatures rise above 70°F, the steam absorption chiller is used exclusively. But because it takes time for the chillers to come on-line, the cogen facility uses high-pressure inlet fogging to provide maximum power instantly. And again as a precooler to augment the chiller when ambient temperatures exceed 100°F. Although the fog system was installed upstream of the air filters, the final barrier filters remain dry and these filters stay cleaner due to the scrubbing effects of the mist. At Las Vegas Cogen, the first cooling stage achieves 7°F of cooling, two stages deliver 12°F and all three provide 15°F. The overall result of fogging is an additional 5 MW of power output.