A gas turbine is an engine that burns fuel in a stream of compressed air, then uses the hot, expanding gases to spin a turbine and produce power. It’s the same core technology behind jet engines, helicopter rotors, and many of the power plants that keep electrical grids running. Gas turbines range from compact units producing a few megawatts to massive machines generating over 500 MW, and they operate at internal temperatures reaching 1,430°C.
How a Gas Turbine Works
Every gas turbine follows the same four-step process, known as the Brayton cycle. Air enters through an intake, gets squeezed to high pressure, mixes with fuel and ignites, then blasts through a turbine that extracts the energy. That’s the entire principle, whether the turbine is bolted to a power plant floor or hanging under an airplane wing.
In the first stage, air is drawn into the engine and slowed down, which raises its pressure slightly before it reaches the compressor. The compressor, a series of spinning blade-studded discs, then squeezes the air further, raising both its pressure and temperature significantly. This compressed air flows into a combustion chamber where fuel is injected and ignited. The burning fuel heats the air to extreme temperatures, but the pressure stays roughly constant. Finally, the superheated gas rushes through the turbine section, spinning blades connected to a central shaft. That shaft drives the compressor (keeping the cycle going) and, depending on the application, also drives a generator or propels an aircraft.
One key detail: the turbine and compressor sit on the same shaft, so the turbine’s job is partly just powering the compressor. The useful energy, the part that generates electricity or thrust, comes from whatever is left over. In a jet engine, the remaining energy accelerates exhaust gases out a nozzle to produce thrust. In a power plant, a separate power turbine captures that energy and spins a generator.
Simple Cycle vs. Combined Cycle
A gas turbine running on its own is called a simple cycle setup. It’s fast and responsive but wastes a lot of heat. A simple cycle gas turbine converts roughly 34.5% of the fuel’s energy into electricity, meaning nearly two-thirds escapes as hot exhaust.
Combined cycle plants solve this by adding a second stage. The hot exhaust from the gas turbine passes through a heat recovery system that generates steam, which then drives a separate steam turbine to produce additional electricity from the same fuel. This pushes overall efficiency past 60%, with modern plants achieving around 62.5%. That near-doubling of efficiency is why combined cycle plants dominate new natural gas power generation worldwide.
Types of Gas Turbines for Power Generation
Industrial gas turbines split into two broad families: aeroderivative and heavy-duty (sometimes called “frame” machines). The differences matter because they determine how a turbine fits into an electrical grid.
Aeroderivative turbines evolved directly from jet engines. They’re lighter, more compact, and built for flexibility. A modern aeroderivative unit can go from a cold stop to full power in about 5 to 10 minutes. That speed makes them ideal for backing up wind and solar farms, handling peak demand, powering remote grids or islands, and providing fast-start resilience for data centers.
Heavy-duty turbines are purpose-built for stationary power at enormous scale. They’re designed to run for long stretches at high output, prioritizing durability and efficiency over startup speed. In combined cycle mode, a heavy-duty plant typically needs around 30 to 40 minutes for a hot start because the steam side of the system has to heat up gradually. These machines shine in baseload power generation (running around the clock), large industrial facilities like refineries, and mega-projects exceeding 400 MW where economies of scale drive down the cost of each unit of electricity.
Gas Turbines in Aviation
The same Brayton cycle powers virtually every commercial and military aircraft. Aviation gas turbines come in several forms, each optimized for different flight conditions.
Turbojets, the original design, are the simplest. All the energy goes into producing a high-speed exhaust jet. They excel at very high speeds but burn fuel fast and are extremely loud, which is why they’ve largely been replaced in commercial aviation.
Turbofans, the engines on most airliners today, add a large fan at the front that pushes a big volume of air around the core engine. Only part of the air goes through the combustion process. The rest bypasses it, producing thrust more quietly and efficiently at typical cruising speeds.
Turboprops connect the turbine to a propeller through a gearbox. The turbine spins a shaft, the gearbox converts that rotation to the right speed for the propeller, and the propeller pulls the aircraft forward. They’re fuel-efficient at lower speeds and common on regional aircraft. Turboshaft engines use the same principle but drive a helicopter rotor or industrial equipment instead of a propeller, offering a much higher power-to-weight ratio than traditional piston engines.
Fuel Flexibility and Hydrogen Blending
Gas turbines run primarily on natural gas or liquid fuels like diesel and kerosene, but they can burn a surprisingly wide range of fuels. This flexibility is becoming increasingly important as the energy industry explores lower-carbon options.
Hydrogen blending is the most active area of development. Many current turbines can handle 5 to 10% hydrogen by volume mixed into natural gas without any modifications. Newer models push much higher. Several large turbines from major manufacturers already support 30 to 50% hydrogen blending with existing low-emission combustion systems. Some models go further: certain GE aeroderivative units are rated for 85% hydrogen, and some older-design GE turbines can handle 100% hydrogen using diffusion flame combustion. Siemens offers medium-sized industrial turbines rated for up to 75% hydrogen.
The challenge with hydrogen is that it burns hotter and faster than natural gas, which can increase the formation of nitrogen oxides (a harmful pollutant). Manufacturers are developing advanced combustor designs to manage this tradeoff, aiming to burn high concentrations of hydrogen while keeping emissions low.
Emissions and Environmental Controls
The primary environmental concern with gas turbines is nitrogen oxide emissions, which form when air is heated to very high temperatures during combustion. Modern turbines use several strategies to keep these emissions in check.
The most common approach is called dry low-emission combustion. Instead of injecting fuel directly into the flame, these systems premix a lean fuel-air mixture before it enters the combustion zone. This lowers the peak flame temperature, which dramatically reduces nitrogen oxide formation at the source. Ultra-low-emission designs take the same concept further with even more thorough fuel-air mixing.
An older but still-used method involves injecting water or steam into the combustion zone. The water absorbs heat, lowering flame temperatures and cutting emissions. For the tightest regulations, plants add a post-combustion treatment called selective catalytic reduction, where ammonia reacts with nitrogen oxides in the exhaust stream, converting them into harmless nitrogen gas and water. This system is now standard on most new gas turbine installations.
Maintenance and Lifespan
Gas turbines are high-performance machines operating under extreme heat and rotational stress, so they follow strict maintenance schedules. The standard interval for a major overhaul is around 30,000 operating hours, which translates to roughly 3 to 5 years of continuous baseload operation or much longer for units that run intermittently. A major overhaul essentially resets the clock, permitting another 30,000 hours of operation.
Between major overhauls, operators perform annual internal inspections to catch problems early. Every startup subjects the turbine to thermal stress as components heat rapidly from ambient temperature to over a thousand degrees, so units that start and stop frequently may need attention sooner than the hour threshold suggests. This is one reason peaking plants, which cycle on and off daily, face different maintenance economics than baseload plants running steadily.
A Brief Origin
The first gas turbine built for power generation was installed in 1939 in Neuchâtel, Switzerland, by the Brown Boveri Company. It was a landmark proof of concept. In the decades since, gas turbines have become one of the most widely deployed power technologies on Earth, and their role is expanding as grids integrate more renewable energy and need fast, flexible backup generation to fill the gaps.