Fogging | Turbine technology
The grid needs more power – fogging can produce it rapidly
Fogging – which produces billions of water droplets per second with an average diameter below 10 microns – is a proven cooling technique for application in gas turbine inlet air cooling and wet compression. Both of these technologies are highly effective in increasing the capacity and efficiency of existing gas turbines, with huge potential for speedily increasing output from the existing gas turbine fleet – much needed at a time of rapidly escalating power demand projections and lengthening lead times for gas fired new build
Thomas Mee III CEO, Mee Industries
Global electricity demand projections by the International Energy Agency (IEA) indicate that annual growth of 3.5% can be expected at least until the end of the decade. This is being driven by electrification of various industries, increased usage of electric vehicles, construction of massive AI data centres, and broader use of air conditioning. By 2030, the growth in power generation will amount to the equivalent of adding the entire energy consumption of the European Union twice over.
Where is that additional power going to come from? It takes years for a new conventional power plant, wind farm, or solar energy plant to come online. Anyone trying to order gas turbines right now is in for a rude awakening. Some models are back ordered until the end of the decade – well beyond for larger machines. One effective way to augment existing power capacity is through inlet air fogging and its sister technology wet compression. Together, they can add up to as much as 25% more power from a gas turbine-based facility. That’s a lot of additional power when you consider that there are as many as 2 TW of operating gas turbines worldwide as of 2025.
Inlet air fogging
Cooling the inlet air of a gas turbine via evaporative fogging is an established way to increase gas turbine power output and improve fuel efficiency. It performs well in humid tropical regions as well as dry climates. How does it work? The output of a gas turbine depends on the mass of air that enters the compressor. As the inlet air temperature rises, the quantity of mass lowers and this reduces the amount of power that can be produced. When evaporative fogging is applied to the inlet air, its temperature drops. As cooler air is denser, more air mass flows through the compressor and power output rises. Further, cooler inlet air reduces the work required by the compressor, helping to improve overall efficiency.
An example of inlet air fogging in practice is provided by Midland Cogeneration Venture in Michigan, which needed a cost-effective way to boost output at its facility. Its new owners wanted to generate additional
Location of nozzles for gas turbine fogging applications
Inlet air fogging nozzles. Can be either upstream or downstream of the air filters.
Wet compression nozzles. Installed just upstream of the compressor inlet.
More than 1000 gas turbine fogging projects have been carried out by Mee at sites throughout North America and worldwide. The majority have fog nozzles installed downstream of the air filters, but recently there has been a revival of interest in placing the fogging arrays upstream of the air filters. Mee’s first installation of gas turbine inlet air fogging was at Harbor Cogen in Southern
California in 1991 on a GE 7EA turbine, where it continues to be used for power augmentation to this day. The fogging arrays were placed upstream of the air filters. For wet compression applications, which consists of spraying fog into the compressor
where it evaporates and gives an intercooling effect, fogging is installed just before the compressor bell mouth. Image: Mee Industries
revenue from twelve ABB11NM gas turbines by increasing their output, particularly during warm summer days when temperatures could reach 90°F at 40% relative humidity. Turbine output suffered badly. The owners evaluated chilling and media-type evaporative cooling before choosing to install inlet air fogging, which turned out to be much cheaper than chilling and far more efficient than media-type evaporative cooling.
The facility initially added fogging on six units. Installation included a fog pump skid, nozzle manifolds, 726 fog nozzles, and seven stages of cooling that could provide a combined cooling capacity of up to 29°F. Demineralised water at 2000 psi and at
a flow rate 33 gpm produces fog droplet averaging eight microns in diameter. Power requirements of the fog pumps are 55 hp. After fogging was introduced, each turbine increased its output by as much as 12 MW. As a result, fogging was added to another six turbines. In another example, NV Energy’s Las Vegas generating station in North Las Vegas experienced a major fall off of power output from its GE LM6000 gas turbine during long, hot, and dry summers. Previously, the company used a steam absorption chiller to cool the inlet air and boost power output. However, operators were unable to cool the inlet air to its dew point during periods of high ambient temperatures.
www.modernpowersystems.com | July/August 2026 | 29
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