A turbine’s main function is to convert the energy of a moving fluid into mechanical energy, specifically rotational motion. That fluid can be water, steam, combustion gas, or wind. In most applications, the spinning shaft of a turbine connects to a generator that produces electricity, making turbines the core technology behind roughly 90% of the world’s power generation.
How a Turbine Converts Energy
Every turbine works on the same basic principle: a fluid pushes against a set of blades mounted on a central shaft, and the force of that fluid causes the shaft to spin. The energy starts as kinetic energy (the motion of the fluid) or thermal energy (heat and pressure in steam or gas), and the turbine transforms it into mechanical energy you can use to drive a generator, a pump, or a compressor.
Inside the turbine, rows of blades alternate between two types. The rotor blades are attached to the central shaft and spin with it. Between them sit stator blades, which are fixed in place. The stators redirect the flow of fluid so it hits the next set of rotor blades at the optimal angle, preventing the flow from spiraling uselessly around the shaft. This alternating arrangement extracts energy from the fluid in stages, squeezing more work out of each pass.
Impulse vs. Reaction Turbines
Turbines fall into two broad mechanical categories based on how the fluid interacts with the blades.
In an impulse turbine, the fluid is first accelerated through a stationary nozzle, converting pressure into a high-speed jet. That jet strikes bucket-shaped blades on the rotor, transferring its kinetic energy into rotation. The pressure drop happens entirely in the nozzle, not on the blades themselves. Pelton wheel hydroelectric turbines are a classic example: a jet of water strikes cup-shaped buckets at high velocity.
In a reaction turbine, the rotor blades themselves are shaped like small nozzles. The fluid expands and accelerates as it passes through both the stationary and moving blades, creating a push similar to air escaping a balloon. That continuous reaction force drives the rotor. Most modern steam turbines and the turbines inside jet engines use reaction designs, sometimes combined with impulse stages at the front end.
Types of Turbines by Fluid
Steam Turbines
Steam turbines are the workhorses of electricity generation. Burning fuel (coal, natural gas, biomass) or harnessing nuclear reactions heats water into high-pressure steam, which expands through the turbine to spin the shaft. But the heat source doesn’t have to be conventional. Geothermal plants use underground steam or hot water. Waste-heat recovery systems capture energy from industrial processes like cement kilns or steel blast furnaces. Some facilities burn wood chips, used tires, or sugarcane fiber (bagasse) to produce steam, making them a form of biomass power generation.
One advantage of steam turbines is their flexibility. They can pair with virtually any heat source capable of boiling water, and extracted steam from the turbine can be rerouted to preheat boiler water or supply heat directly to industrial manufacturing processes. This dual use of steam for both electricity and process heat significantly improves overall plant efficiency.
Gas Turbines
Gas turbines burn fuel (typically natural gas or jet fuel) in a combustion chamber, and the hot, expanding exhaust gases spin the turbine directly. They’re the engines behind jet aircraft and a growing share of grid electricity. On their own, gas turbines convert about 35 to 40% of their fuel’s energy into electricity. But in combined-cycle power plants, the hot exhaust from the gas turbine generates steam to drive a second steam turbine, capturing energy that would otherwise be wasted.
This combined approach pushes efficiency dramatically higher. A combined-cycle plant built in Bouchain, France, using a GE gas turbine, set a Guinness record in 2016 by reaching 62.22% net electrical efficiency. Current engineering designs using steam cooling of the gas turbine and optimized compression ratios have pushed net efficiencies above 63%, with theoretical configurations exceeding 65%. For context, a traditional coal plant typically converts only about 33% of its fuel energy into electricity, so combined-cycle gas turbines represent a major leap.
Hydraulic (Water) Turbines
Hydroelectric turbines convert the energy of falling or flowing water into rotation. A dam creates a height difference, giving water gravitational potential energy. As the water drops through a penstock and hits the turbine blades, that energy becomes mechanical rotation. Hydroelectric turbines are among the most efficient energy converters available, often exceeding 90% efficiency, because water is dense and transfers its energy to the blades with very little waste.
Wind Turbines
Wind turbines capture the kinetic energy of moving air. As wind pushes against the angled blades, they rotate a shaft connected to a generator inside the nacelle (the housing at the top of the tower). Onshore wind turbines typically produce between 2 and 5 megawatts each. Offshore turbines, benefiting from stronger and more consistent winds over open water, are scaling up rapidly. The South Fork Wind Farm off the coast of New York, fully commissioned in March 2024, generates 132 megawatts as the first commercial-scale offshore wind farm in the United States. Individual offshore turbines now reach 15 megawatts or more.
Wind turbines face a theoretical ceiling called the Betz limit: no turbine can capture more than about 59% of the wind’s kinetic energy, because some air must continue moving past the blades. Modern designs capture around 35 to 45% in practice.
Why Turbines Dominate Power Generation
Turbines are so widespread because rotational energy is the easiest form of mechanical energy to convert into electricity. A spinning shaft connected to a generator is a simple, reliable setup that scales from a few kilowatts to over a gigawatt. Solar panels and fuel cells generate electricity through entirely different mechanisms, but for any energy source that involves heat, pressure, or fluid motion, a turbine remains the most practical way to bridge the gap between raw energy and usable power.
Beyond electricity, turbines drive mechanical loads directly. Industrial steam turbines power compressors in chemical plants, pumps in oil refineries, and blowers in steel mills. Gas turbines propel ships and aircraft. The function is always the same: take a moving fluid and turn it into rotation that does useful work.