GROWTH OF GAS TURBINE TECHNOLOGY
The gas turbine was originally developed during the 1930s and 1940s as an aviation engine and it remained almost exclusively the preserve of the aviation industry until the end of the 1960s. The potential for gas turbines to be used in power generation began to be exploited during the 1970s and early 1980s when they entered service for standby and peak power support on national grids. These early aero-derivative gas turbines were broadly similar in design to the aero engines upon which they were based and shared many components. They were light, they could start up quickly, and they were able to change power output rapidly, making them ideal for a grid support role.
Recognizing the value of gas turbines to the power generation industry, some manufacturers began to design industrial gas turbines intended specifically for this market. These were heavier in construction than their aero-engine counterparts since weight was not an issue for stationary applications such as power generation. As their design evolved, and as their performance was tailored specifically for the power generation market, these industrial gas turbines moved further away from aero engines. At the same time, aero-derivative stationary engines remained in production alongside the new industrial ranges of products.
It was toward the end of the 1980s that the first big combined cycle power plants were built using gas turbines. These used one or more gas turbine generators to produce electricity, with the heat from the turbine exhaust utilized to raise steam in a special heat-recovery boiler. The steam was then used to generate more electrical power in a steam turbine generator. This combination led to a high-performance power plant configuration that, by 1990, was capable of around 50% energy conversion efficiency.
The market for combined cycle power plants grew rapidly during the 1990s, particularly in Europe and the United States where companies operating in the newly liberalized and deregulated electricity markets found the low cost of such plants appealing. Steep rises in the cost of natural gas toward the end of the decade blunted the appeal somewhat. Even so they continued to be popular during the first decade of the 21st century, although gas price volatility during the decade made their economics sometimes questionable. In the second decade of the century with gas availability predicted to rise and prices expected to stabilize, the economics of combined cycle generation look promising again.
To cater for the growing power generation market, the main manufacturers— and there are only a limited number of these because the gas turbine is a very specialized high-technology machine—quickly began to build bigger and more efficient engines. Today, single engines of up to 400 MW in capacity are available. Most of these are aimed at the combined cycle market and have efficiencies on their own between 38% and 42%. However, when used in a modern integrated combined cycle plant the latter should be capable of around 60% efficiency.