Short Answer:

The disadvantages of gas turbine plants mainly include lower efficiency at part loads, high operating temperatures, high maintenance cost of components, and the need for clean fuel and air. Gas turbines are less efficient than steam plants at low power output and require expensive materials to withstand high temperatures.

In simple words, gas turbine plants, though compact and fast, face challenges like high fuel consumption, costly maintenance, and sensitivity to dust or impurities. Their performance reduces under unfavorable weather conditions, making them less suitable for continuous base-load operation compared to other power plants.

Detailed Explanation :

Disadvantages of Gas Turbine Plants

A gas turbine plant is a type of power generation system that operates on the Brayton cycle, using compressed air and fuel to produce high-temperature gases that drive a turbine. Although gas turbines are known for their compactness, quick start-up, and high power-to-weight ratio, they also have certain limitations.

These disadvantages are mainly related to their operating temperature limits, fuel requirements, maintenance costs, and efficiency variations under different conditions. Understanding these drawbacks is essential for improving turbine design and operation.

Low Efficiency at Part Load

The efficiency of a gas turbine decreases significantly when it operates at part load or below its rated capacity.
Gas turbines are most efficient when running at full load because the compressor and turbine are designed for optimal air-fuel ratios at specific conditions.
At part loads, the temperature and pressure ratios reduce, causing incomplete combustion and higher specific fuel consumption.
This makes them less suitable for applications where the load changes frequently, such as in variable-demand power plants.

Example:
A gas turbine operating at 50% of its rated power may have a drastic drop in efficiency compared to full-load operation.

High Operating Temperature

Gas turbine plants operate at extremely high temperatures, typically between 1000°C and 1500°C.
These high temperatures are necessary to achieve good efficiency, but they cause thermal stresses on turbine components.
Special high-temperature-resistant materials such as nickel-chromium alloys are required for turbine blades, which are very expensive.
Continuous exposure to high temperatures also leads to oxidation, corrosion, and material fatigue, reducing the life of components.

Thus, maintaining and replacing high-temperature parts increases operational costs and downtime.

High Maintenance and Repair Cost

Although gas turbines have fewer moving parts than steam engines, their components, especially turbine blades and combustion chambers, operate under extreme conditions.
This results in frequent inspection, cleaning, and replacement of parts.
The maintenance cost per kilowatt-hour is often higher compared to steam or diesel plants.
Modern gas turbines require precision maintenance and skilled labor, which adds to the cost.

Example:
Deposits from fuel or impurities can damage turbine blades, requiring frequent cleaning or even complete replacement after a few thousand hours of operation.

Requirement of Clean Fuel and Air

Gas turbines are highly sensitive to dust, dirt, and impurities in both fuel and air.
If dust or foreign particles enter the compressor, they erode and damage the blades, leading to reduced efficiency and mechanical failure.
Similarly, impure fuels containing ash, sulfur, or moisture can corrode combustion chambers and turbine blades.
Hence, filters and purifiers are needed to clean air and fuel, increasing installation and maintenance costs.

This requirement makes gas turbines less suitable for dusty or polluted environments unless equipped with advanced filtration systems.

Poor Efficiency at Low Temperatures

The performance of gas turbines is affected by ambient air temperature.
At high ambient temperatures, the density of air decreases, leading to lower mass flow through the compressor and reduced power output.
Therefore, gas turbines produce less power and become less efficient in hot weather.
To overcome this, inlet air cooling systems are used, but they increase the cost and complexity of operation.

Example:
In tropical climates, the output of a gas turbine may reduce by 10–15% due to high ambient temperatures.

High Fuel Consumption

Gas turbines consume more fuel compared to steam or diesel power plants for the same power output, especially when operating at partial load.
The specific fuel consumption (SFC) is high because of the large energy required to drive the air compressor.
Since about 50–60% of the turbine power is used just to run the compressor, the net power output is relatively low.

This makes gas turbine plants more costly to operate in terms of fuel expenses, especially when fuel prices are high.

High Initial Cost of Installation

Gas turbine plants require expensive materials and high-precision manufacturing techniques to withstand high pressures and temperatures.
The initial investment for advanced materials, cooling systems, and control systems is high.
While the overall plant is compact, the cost per megawatt can be higher than that of a conventional steam plant, especially for small-capacity units.

This high cost makes them less suitable for low-budget or small-scale power projects.

Shorter Life of Components

Due to high operating speeds and thermal stresses, turbine blades, nozzles, and combustion liners have a limited life.
The frequent expansion and contraction of metals due to temperature variations lead to metal fatigue and creep.
This requires regular monitoring and part replacement to prevent breakdowns.

Therefore, the life expectancy of a gas turbine plant is shorter compared to a steam turbine plant of similar capacity.

Noise and Vibration Problems

Gas turbines produce a high level of noise during operation because of high-speed exhaust gases and rapid combustion.
Additional silencers or enclosures are required to reduce the noise to acceptable limits.
The compressor and turbine rotation at high speed also cause vibrations, which may require special foundation and balancing arrangements.

This adds to the installation and maintenance cost, especially in urban or residential areas.

Difficulty in Starting Under Cold Conditions

In cold weather, the starting of a gas turbine becomes difficult because the viscosity of lubricating oil increases, and combustion may not occur properly.
This problem is more severe in small turbines that lack advanced starting systems.
Auxiliary systems such as electric starters or heaters are often needed to assist the initial ignition and rotation.

This increases complexity and delays startup in cold environments.

Summary of Main Disadvantages

Low efficiency at part loads.
High temperature operation requires costly materials.
High maintenance and inspection needs.
Requires clean fuel and air for operation.
Sensitive to ambient temperature changes.
High fuel consumption and cost.
Shorter life span of components.

Conclusion

In conclusion, the disadvantages of gas turbine plants include high fuel consumption, expensive maintenance, sensitivity to environmental conditions, and reduced efficiency at part loads. They require clean fuels and advanced materials to withstand high temperatures, which increases overall cost. Despite these drawbacks, gas turbines remain important in aviation, power generation, and industrial applications due to their compact size, quick start, and reliability. Ongoing technological improvements in materials, cooling systems, and combined-cycle designs continue to reduce these disadvantages and enhance their performance and efficiency.