High humidity can significantly impact power plant performance in several ways:
Reduced gas turbine efficiency and power output
Humid air is less dense than dry air because the molecular weight of water vapor is less than that of dry air.
This lower density leads to a reduction in the mass flow of air through the compressor, which directly impacts the power output and efficiency of the gas turbine.
Additionally, high humidity can decrease compressor efficiency.
For example, a change from 60% to 100% relative humidity at 59°F can result in a decrease in power output of about 0.05% and an increase in heat rate (decreased efficiency) of about 0.17%.
Condensation and corrosion
High humidity increases the likelihood of condensation within power plant equipment, especially when humid air is cooled below its dew point.
This condensation can lead to corrosion and rust in turbines, boilers, generators, and other components.
Corrosion can significantly reduce the lifespan of equipment and potentially lead to malfunctions or breakdowns.
The U.S. power industry reportedly experiences billions of dollars in plant repairs and increased downtime due to corrosion annually, according to the Polygon Group.
Cooling tower performance
Cooling towers rely on evaporative cooling, which is less efficient in humid environments as the air has a reduced capacity to absorb moisture.
High humidity can also promote the growth of algae, bacteria, and fungi in cooling towers, which can form biofilms, restrict water flow, and further decrease efficiency.
Maintenance challenges
High moisture environments pose challenges for maintaining equipment in optimal condition.
Regular inspection and cleaning are necessary to prevent corrosion and biological growth.
Lubrication and protective coatings can help prevent rust, while dehumidification systems can be employed to control humidity levels in power plants, particularly during periods of inactivity or storage.
Potential impact on workers
Operating in high-humidity and high-temperature environments can pose health risks for workers, including heat stress and heat stroke, notes the Polygon Group.
In essence, while the direct impact on efficiency for short-term humidity fluctuations might seem minor, the overall cumulative effects of high humidity, encompassing corrosion, maintenance issues, and potential health concerns, can significantly impact power plant performance, reliability, and operating costs in the long run
The root cause of high humidity is high global temperatures, which hold more moisture. My Master of Science thesis was on the subject of power plant cooling towers and their performance in different weather conditions. Cooling tower performance is degraded in high humidity because the evaporation rate is degraded. Degraded cooling tower performance means less electricity generated. The driving force for thermal power plants (coal, gas, nuclear and geothermal) is the temperature difference between the steam going into the turbine-generator and the cold water return from the condenser (cooling towers cool the condenser).
Higher relative humidity (RH) negatively impacts cooling tower performance by reducing the air’s ability to absorb water through evaporation, which is the primary cooling mechanism. Conversely, lower inlet RH allows for greater evaporation and more effective heat rejection, meaning a lower inlet RH leads to better cooling. When RH reaches 100%, evaporation ceases, eliminating the evaporative cooling effect and greatly reducing the tower’s capacity. The wet-bulb temperature, which is directly influenced by relative humidity, is the most critical parameter for cooling tower performance, as it dictates the lowest possible water temperature achievable through evaporation.
The reason I asked is that you also wrote that “The root cause of high humidity is high global temperatures, which hold more moisture.”
However, while there are local variations the global relative humidity is pretty much constant. From Douville et al.
Global warming at near-constant tropospheric relative humidity is supported by observations https://www.nature.com/articles/s43247-022-00561-z Moreover, global warming is generally assumed to occur at near-constant relative humidity…all global climate models support the constant tropospheric relative humidity hypothesis…
As stated in my previous post, the efficiency of cooling towers is degraded with increasing wet bulb temperatures.
Climate change is causing a rise in wet bulb temperatures in high humidity land and water areas (not in low humidity areas such a deserts and arid areas).
My guess would be no based on the study saying less than 0.2% loss for very high humidity. Doubtful you could install, maintain and operate a dehumidifier for that small delta.
OTOH, if it extended the life of the equipment or maintenance intervals at the same time due to less corrosion, then maybe yes.
Combustion air water injection systems are quite common in places with low relative humidity. This technique can be effective in higher humidity areas during regimes of lower relative humidity at the air inlet system. In the below figure, the water injection system would be placed in the blue ducting ahead of the GT inlet (pink).
Separately, and relevant to the OP, evaporation cooling tower efficiency and effectiveness are impacted quite significantly by relative humidity in the air. Critically, the venturi design in these towers is specifically built to enhance performance in ANY circumstance.
