by Carter Palmer, Power Systems Specialist, Forecast International.
For the first time, combined-cycle power plants (CCPPs) have surpassed coal-fired power plants in power generation in the U.S. Installed combined-cycle capacity now stands at 264 GW, whereas coal-fired production is at 243 GW. Although gas overtook coal in the 2000s, this is the first time a specific technology – combined-cycle – topped coal.
Gas turbines were developed in the 1930s and combined-cycle technology has been around since the 1950s. A combined-cycle plant utilizes the hot exhaust from gas turbines to heat water, produce steam and, in turn, power a steam turbine. The configuration can be one gas turbine and one steam turbine (1×1) or two gas turbines and one steam turbine (2×1). By utilizing heat that would otherwise be wasted, combined-cycle plants are more efficient than simple-cycle (i.e., a stand-alone gas turbine) layouts.
The news comes during a downturn in the overall gas turbine market. The downturn is due to a few factors, including strong renewable competition. Electricity produced by renewables is now competitive with that produced by traditional fossil fuel means. Nevertheless, gas turbines still have a place – they can produce power at any time, whereas solar and wind power are dependent on forces of nature. Another factor of this downturn is overcapacity: there are more turbines than needed. One example of this is a combined-cycle plant in Bavaria, Germany. Once the most efficient CCPP in the world, the Irsching Power Station has been idled now for a third year due to low profitability.
Despite the slump in the gas turbine market, energy demands continue to increase worldwide. The fact that combined-cycle applications have out-performed coal is indicative of environmental trends affecting the industry. Coal is not as environmentally friendly as other technologies. Gas turbines, on the other hand, are seemingly here to stay.
