Everyone needs megawatts! Throughout America and the world, power demands are rising due to data centers which sometimes steal power from residential and commercial grids. Unfortunately, the gas turbine original equipment manufacturers (OEM’s) are booked solid for 2-3 years and installation of a new engine is fraught with greenfield permitting and financial risks. Besides, maybe a new power plant is not needed, rather, just a strong power increase? So how do you increase gas turbine power output this year and not years in the future? Inlet water augmentation will provide up to 15% increase in gas turbine power and is deliverable within 40 weeks of purchase.
Caldwell Energy is a well-established manufacturing company hidden in the bourbon belt of Louisville, Kentucky USA. Don Shepherd began its operations in 1995 and the company quickly found its niche building and installing gas turbine power augmentation equipment by using Wet Compression and Fogging.
Quick Facts
- Increase Energy output up to 15%
- Only technology with consistent power gains regardless of ambient conditions
- Costs less per installed KW than any other Inlet Cooling Technology
- Complimentary to PowerChill®, PowerStor® and PowerFog®
Performance
Caldwell Wet Compression Technology (CWCT)™ is the next step to increasing output and efficiency of combustion turbines. Output on most turbines is targeted at a 15% increase with an improvement in heat rate of 1.5%. Since the improvement in the heat rate is across the total output of the combustion turbine (CT), the incremental heat rate improvement is 11.5%. The following table illustrates CWCT performance effects on a 100 MW Frame Class Turbine operating in simple cycle.
Water Mechanisms
When air is cooler, it is denser, and when it is hotter, it is less dense. Accordingly, in hot weather, gas turbine power is reduced and much of this lost power can be recovered by installing fogging and/or wet compression.
How it Works
There are basically three effects produced by the injection of fog into the bellmouth region of a combustion turbine. They are:
01
Reduction of inlet air temperature to near wet bulb temperature
02
Mass flow enhancement augmenting power output
03
Increased efficiency of the compressor, resulting in output increase and improved efficiency
Fogging vs Wet Compression
Fogging works by introducing a fine mist of water into the inlet airstream far enough upstream of the engine that the water has time to evaporate into the incoming air. The humidified air is now full of water and the evaporation has made it cooler, so, to the denser air, more fuel can be added increasing the power output of the gas turbine. Fogging power increases depend on the relative humidity of the ambient air, but in dry locations, up to 6% increase in power can be had.
Inlet humidity for fogging must be tightly controlled. Too much water, using techniques labeled “overspray” or “high fogging” oversaturates the air turning the fine droplets into large slugs of water that either stick to inlet ductwork and run, wasted, out the drain, or enter the compressor as large slugs and erode the compressor blades. Inlet Fogging increases power by up to 6% depending on ambient relative humidity.
But if more power is needed, Wet Compression can deliver. Wet compression works by intentionally introducing liquid water, in very fine drops, into the compressor of the engine. When this water evaporates, the latent heat of vaporization cools the air which reduces its volume. The evaporative cooling (also known as compressor intercooling) helps the compressor do its job and the saved work is then available to turn the generator. Also, the extra mass flow through the engine is combusted with more fuel to make additional power. In total, wet compression increases gas turbine output by up to 15%.
Technology
Caldwell Wet Compression Technology™ stands poised to revolutionize power augmentation technology. CWCT systems properly inject micron sized fog droplets into the compressor section of the CT. These are not upsized fogging systems. CWCT systems typically inject four times the amount of water that a fogging system does into a cross-sectional area one-eighth the size. In order to achieve this, a very robust nozzle rack with multi-orifice nozzle holders are used to achieve the required flow with minimum droplet size. The high pressure water supply is generated by industrial grade positive displacement pumps with maintenance intervals similar to combustion turbines. Typical mass flow injection rates are equal to 2% of the air flow at ISO conditions, similar to the flow rates of NOx water injection systems. To minimize the effect of thermal stresses on a combustion turbine, the spray flow is staged up and down during startup and shutdown of the system in an engineered manner. Many other safety features are incorporated into the system to protect both the turbine and the CWCT system.
Benefits
Wet Compression generally increases power output by up to 15% depending on the engine and ambient conditions.
Scope
The main component of fogging and/or wet compression equipment consists of a skid which mounts the long-lasting, smooth running, easily maintained, axial positive displacement pumps, (no belts or vibration) AC motors, filters, valves, variable frequency drives, and programmable logic controller. The skid itself is made of painted structural steel and mounted on a customer- supplied concrete pad outside the enclosure. The other main component is the nozzle spray rack which is mounted inside the gas turbine inlet duct. Water delivery happens through these nozzles.
To generate a firm proposal, Caldwell typically arranges a site visit to perform a 3D scan of the inlet ductwork. This scan is used along with engine air mass flow to create computational fluid dynamics (CFD) models which determine nozzle quantity and locations in the inlet duct. Next, finite element analysis (FEA) is used to perform stress analysis on the modeled spray rack structure to ensure integrity and long life. Components are ordered and assembled, and complete unit operational wet testing happens at Caldwell’s factory before delivery. Specialized crews perform the installation in little more than a week, then commissioning and testing is supported.
Operation and Risks
Wet compression is only operated above 50°F with the engine at base load. There are usually two stages of flow and they are ramped up to the maximum water flow. Also, the engine OEM may recommend specific actions after a turbine trip, and there may be hours limitations per service interval. Always consult your engine OEM when applying water augmentation.
But water augmentation is not without risks! Demineralized (demin) water must be used to maintain clean compressor surfaces, otherwise corrosion starts and will not only cause pitting on blades and vanes but could also impede disassembly on some engines. Demin water also keeps the spray nozzles free of deposits that would spoil the fine droplet size and turn the mist into large slugs of water that will either stick to inlet ductwork and run, wasted, out the drain, or impact the compressor blades and quickly cause severe erosion.
Things to Look Out For:
01
It is well known that CO emissions will go up if WetC is used at the same time as duct firing, so permitting actions for CO emissions may need to be addressed.
02
Plant water usage will increase, and permitting actions may be necessary for that, also.
03
Using demineralized water is mandatory, so holding tanks will need to be constructed.
04
Inspections must be conducted on the spray rack to ensure there are no dirty or loose nozzles or structure.
05
In some applications, the engine OEM may restrict hours and/or require coatings or replacement of the early stages of the compressor or outright replacement of these blades and vanes at each major. Consult your engine manufacturer for those specific recommendations.
Case Studies
In 2025, Caldwell Energy completed installation of wet compression on a Mitsubishi JAC frame, achieving 38MW added at 156 gpm of injected demineralized water. Also, between 2021 and 2023, Caldwell Energy installed first-time-applications on several 60Hz Siemens frames, with F5: 26MW added, F5EE: 26MW added, F4: 33MW added, 5000G 28MW added, 4000F 26MW added, 2000E 13.5MW added, and soon to be 6-8000H anticipating over 30MW added.
Looking forward
To accommodate increasing business and stretch our legs, Caldwell Energy has constructed a new manufacturing plant in Shelbyville, KY that was opened in May 2026.
Conclusion
In hot and/or dry areas, water augmentation has proven itself. And since 1995, Caldwell Energy has installed over 6.2GW of increased capacity between fogging and wet compression.
When contemplating pricing, it's instructive to put the benefits of wet compression into perspective in dollars per kilowatt ($/kW). Prices for a new plant are around 1,500-2,000 $/kW, which, many times, is too much and takes too long, so most power providers go to the OEM for a traditional blade and vane gas turbine modernization. These generally are on the order of 500-600 $/kW. This would put the price of a 22MW GT Modernization from the OEM at around $13,000,000 and it would still require an 18-month leadtime, and a rotor-out major to implement. Additionally, at last check, OEM’s generally sell wet compression at around $125/kW. Compare those figures with the current proposal pricing and see that Caldwell wet compression is the single most cost-effective way to add power to gas turbines.
Also, compared to blade, vane, and combustor upgrades, water augmentation has multiple advantages. An engine cover lift is not required. Unlike a firing temperature increase, water augmentation does not burn up hot parts, change service intervals, or increase NOx. The install time is about 2 weeks including commissioning and testing. Installed cost is far lower than turbine modernizations and has a much shorter leadtime.
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Contact us today to enhance your power plant's efficiency and reliability with Caldwell Energy.
