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Case Study: How MeeFog improved gas turbine cooling efficiency in extreme heat for General Electric Company of......
MeeFog System Still Going Strong After Three Decades
Gas Turbine
Las Vegas Generating Station Boosts Efficiency with MeeFog System
Location: North Las Vegas, Nevada
NV Energy owns the Las Vegas Generating Station in North Las Vegas, which now includes the former Las Vegas Cogen plant. The company provides a wide range of energy services to more than 1.5 million customers across Nevada, including the typical annual tourist population of 54 million. NV Energy, Inc. is a holding company whose principal subsidiaries, Nevada Power Company and Sierra Pacific Power Company, both operate under the NV Energy brand. The company is headquartered in Las Vegas, Nevada.
The Challenge:
During Nevada’s long, hot, and dry summers, output at the Las Vegas Cogen plant (now part of the Las Vegas Generating Station) would often drop sharply. To address this, the facility needed a way to boost output while reducing energy consumption as part of an ongoing efficiency initiative.
The Solution:
Las Vegas Cogen operated a GE LM6000 gas turbine and initially used a steam absorption chiller to cool the inlet air and boost power output. However, plant operators found that they were unable to cool the inlet air to its dew point during periods of high ambient temperatures. As a result, management decided to install a MeeFog system to provide additional cooling and ensure the plant could meet its contracted output of 45 MW during hot summer days.
The Results:
- 15°F of cooling during the hot summer months, equating to an addition 5 MW of power.
- Lowered energy usage.
- The facility meets its contracted plant output even during hot, dry days.
- Minimal maintenance in nearly 30 years.
The Physical Site:
The plant’s initial power block is a “one-on-one” 48-megawatt combined-cycle resource that was commissioned in 1994. It uses a General Electric LM6000 turbine generator to produce electricity and a Foster Wheeler Heat Recovery Steam Generator to convert the turbine’s hot exhaust gases to steam. The steam is then used to generate additional electricity with a Dresser Rand steam turbine generator.
In 2003, two additional “two-on-one” combined-cycle power blocks were added. Each 112-megawatt power block consists of two General Electric gas turbine generators that use Innovation Steam Technology. This technology converts the hot exhaust gases from the turbines into steam, which is then used to generate additional electricity through a Dresser Rand steam turbine generator. This conversion process enhances the efficiency of the power generation, benefiting NV Energy’s customers.
The Installation:
The MeeFog system was positioned upstream of the inlet air filters and chiller coil to act as a pre-cooler. The fog system consists of 240 nozzles installed in
three stages. The first cooling stage achieves 7°F of cooling, two stages deliver 12°F, and all three provide 15°F. Operating pressure is 2,000 psi. Water is converted into microfine droplets by Mee Industries’ patented impaction pin nozzle. These nozzles are designed to prevent the formation of large droplets and to ensure that droplet sizes are maintained below 20 microns. The fogging arrays were placed outside of the filter house to eliminate the downtime required to install the system.
As it took time for the chillers to come online, high-pressure inlet fogging was used initially to achieve maximum power output. Fog alone is used when the ambient temperature is below 70°F, while the steam absorption chiller is brought online at temperatures above 70°F, with both systems operating together in such cases.
The Benefits of MeeFog:
The MeeFog system with Las Vegas Cogen provides an additional 5 MW of power output. As maintenance work is negligible, the system has paid for itself many times over. Pressure drop associated with the fog nozzle manifold is nominal. The existing heating coil and pad- type prefilters are used as fog droplet filters to remove any unevaporated fog. Although this prevents wetting of the primary air filters, water collects on the cooling coil and prefilter and is drained off, slightly reducing the amount of cooling accomplished by the fog system. Even though the fog system is upstream of the filters, the final barrier filters remain dry and the filters stay cleaner due to the scrubbing effects of the fog.
“MeeFog has built a quality product which has required minimal maintenance and has performed well above expectations. Despite losing the use of our aging chillers, we have lost minimal output from the plant even with no inlet chilling.”
-Dan Unten, plant operator at Las Vegas Generating Station
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