Natural gas is the most widely used energy source for electricity generation in the United States. Of the 491 GW of natural gas-fired power generation capacity in the country, more than half (280 GW) is combined cycle systems that include both steam turbines and combustion turbines. The predominant configuration for combined cycle systems includes two combustion turbines and one steam turbine (2×1).
Natural gas power plants use simple cycle or combined cycle energy conversion. Simple-cycle systems consume natural gas in a single conversion system, such as a combustion turbine, a boiler with a steam turbine, or an internal combustion engine. In these systems, the primary conversion exhaust heat energy is lost and not sent to another turbine. Combined cycle systems send exhaust heat from the combustion turbine to a heat recovery steam generator, pressurizing the steam for one or more steam turbines which generate additional electrical power.
Combined cycle systems tend to be more efficient at converting a unit of natural gas (measured in Btu) to a unit of electricity (kWh). Combined cycle systems have an average operating heat rate of 7,146 Btu/kWh compared to single cycle systems, which consume approximately 10,000 Btu to generate 1 kWh, based on 2020 averages. efficiency, combined cycle systems typically operate at higher capacity factors than single cycle systems. As a result, combined cycle systems typically serve base and intermediate grid loads, while single cycle systems typically serve peak load.
The EIA’s Annual Electric Power Survey collected a unit code identifier to group combined cycle components into power supplies. Power block configurations vary widely, including configurations such as multiple combustion turbines supporting one or more steam turbines. Most combined cycle power packs have combustion and steam turbine components each connected to a generator. However, 13 GW of combined cycle capacity are single shaft systems in which the combustion and steam turbines drive a common generator on one shaft.
In terms of generating capacity, the largest natural gas-fired combined-cycle power plant in the United States is Florida Power & Light’s West County Energy Center. The West County Energy Center consists of three 3×1 power packs, making a total of 12 combustion and steam turbines. Each of the three power blocks is rated at 1259 MW, giving the plant a total generating capacity of 3777 MW. The West County Energy Center generated 20.3 TWh of electricity in 2021; only five nuclear power stations and one coal-fired power station produced more electricity in 2021.
Combined cycle power packs have increased in average capacity since 2015, when a new class of combustion turbines became more common. These new combustion turbines allow combined cycle power blocks to have greater capacities and improved efficiencies. The average capacity of a 2×1 power block has increased from 500 MW for those built before 2015 to over 700 MW for those built after 2015.
Read the article online at: https://www.hydrocarbonengineering.com/gas-processing/26042022/eia-natural-gas-is-the-most-prevalent-energy-source-for-electricity-generation-in- the- we/