Power plants create electricity by one of several means. Two common elements used to create electricity are steam and gas, each of which require a different apparatus and operating condition to maximize performance. Here’s a brief guide to the difference between steam and gas turbines that provides their key distinguishing factors.
First, gas turbines receive power from a combustion reaction. Fossil fuels meet compressed air and combust to produce extremely hot exhaust gases. These gases contact turbine blades, revolving them to produce electricity. This cycle of energy-creation from compressed air and fuel is the Brayton or Joule Cycle. Air taken into a gas turbine for combustion often creates significant noise, which facility managers mitigate by installing inlet silencers. On its way out, exhaust also creates noise which specialized exhaust silencers address. Important components in gas turbines include the upstream air compressor, the combustion system where the reaction takes place, and the turbine blades that rotate as hot gas travels downstream. The combustion reaction produces exhaust gases as hot as 1,500 degrees Celsius, which is significantly hotter than a steam turbine’s operating temperature. One benefit over steam turbines is, because water is not central to the process, there is no risk of your operation coming to a halt as a result of internal freezing. On the other hand, because gas turbines require fossil fuels, the combustion process inherently creates pollutants such as nitrogen oxide.
The primary difference between steam and gas turbines is the fact that steam turbines receive power from expanding steam. Fuels such as natural gas can heat condensed water in a boiler, but it’s also possible to utilize renewable thermal energy for this heating. This heated water evaporates into steam, which rotates turbine blades to create power. The internal temperature only reaches 500 to 650 degrees Celsius, less than half of the temperature of gas turbine reactions. This water-based cycle is the Rankine Cycle. Unlike gas turbines, steam turbines don’t have an air compressor or combustion system, but rather a boiler, rotors that transfer thermal energy into mechanical energy, and a casing area that ensures the steam contacts the blades under pressure. The centrality of water means there is a risk of freezing, but steam turbines do allow for clean energy creation if renewable energy initially heats the turbine’s cycling water.