EIA：天然气是美国最普遍的发电能源

据碳氢化合物工程4月26日消息，天然气是美国最普遍的发电能源。在该国491吉瓦的天然气发电容量中，超过一半（280吉瓦）是包括蒸汽轮机和燃烧式涡轮机的联合循环系统。联合循环系统的主要配置包括两台燃烧式涡轮机和一台蒸汽轮机。

天然气发电厂利用简单循环或联合循环能量转换。简单循环系统在单个转换系统中消耗天然气，例如燃烧式涡轮机、带有蒸汽轮机的锅炉或内燃机。在这些系统中，来自一次转换排气热的能量会损失掉，并且不会发送到另一个涡轮机。联合循环系统将燃烧式涡轮机排出的热量输送到热回收蒸汽发生器，为一个或多个产生额外电力的蒸汽轮机加压。

联合循环系统在将单位天然气转换为单位电力方面往往更有效。由于效率的提高，联合循环系统通常以比简单循环系统更高的容量因数运行。因此，联合循环系统通常服务于电网的基本和中间负荷，而简单循环系统通常服务于峰值负荷。

EIA的电力年度调查收集了一个单元代码标识符，将联合循环部件分组到功率块中。功率块配置差异很大，包括多个燃烧式涡轮机支持一个或多个蒸汽轮机等配置。大多数联合循环发电机组都有燃烧和蒸汽轮机部件，每个部件都与发电机相连。然而，13吉瓦的联合循环容量是单轴系统，其中燃烧和蒸汽涡轮机在一根轴上驱动一个公共发电机。

就发电量而言，美国最大的天然气联合循环发电厂是佛罗里达电力与照明公司的西县能源中心。西县能源中心由三个3x1 发电机机组组成，或总共12个燃烧和蒸汽涡轮机。三个发电机组中的额定功率均为1259兆瓦，使该工厂的总装机容量达到3777兆瓦。西县能源中心2021 年发电量20.3太瓦；到2021年，只有5座核电厂和1座燃煤电厂发电量增加。

自2015年以来，联合循环发电机组的平均容量有所增加，当时一种新型燃烧式涡轮机变得更加普遍。这些较新的燃烧式涡轮机允许联合循环发电机组具有更大的容量和更高的效率。2x1发电机组的平均容量从2015年之前建造的500兆瓦增加到2015年之后建造的超过700兆瓦。

祝精燕 摘译自 碳氢化合物工程

原文如下：

EIA: natural gas is the most prevalent energy source for electricity generation in the US

Natural gas is the most prevalent energy source used for electricity generation in the US. Of the 491 GW of natural gas-fired electric-generating capacity in the country, more than half (280 GW) are combined-cycle systems that include both steam turbines and combustion turbines. The predominant configuration for combined-cycle systems involves two combustion turbines and one steam turbine (2x1).

Natural gas-fired electric power plants utilise either simple-cycle or combined-cycle energy conversion. Simple-cycle systems consume natural gas in a single conversion system, such as a combustion turbine, boiler with a steam turbine, or internal combustion engine. In these systems, energy from the primary conversion exhaust heat is lost and not sent to another turbine. Combined-cycle systems send combustion turbine exhaust heat to a heat recovery steam generator, pressurising steam for one or more steam turbines that generate additional electric 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 7146 Btu/kWh compared with simple-cycle systems, which consume approximately 10 000 Btu to generate 1 kWh, based on 2020 averages. Because of the efficiency gains, combined-cycle systems generally operate at higher capacity factors than simple-cycle systems. As a result, combined-cycle systems generally serve base and intermediate loads to the grid, while simple-cycle systems generally serve peak load.

The EIA's Electric Power Annual survey collected a unit code identifier to group combined-cycle components into power blocks. Power block configurations vary widely, including configurations such as multiple combustion turbines supporting one or more steam turbines. Most combined-cycle power blocks have combustion and steam turbine components each connected with a generator. However, 13 GW of combined-cycle capacity are single-shaft systems in which both the combustion and steam turbines drive a common generator on one shaft.

In terms of generating capacity, the largest natural gas combined-cycle power plant in the US is Florida Power & Light’s West County Energy Center. The West County Energy Center consists of three 3x1 power blocks, or a total of 12 combustion and steam turbines. Each of the three power blocks is rated at 1259 MW, giving the plant 3777 MW of total generating capacity. The West County Energy Center generated 20.3 TWh of electricity in 2021; only five nuclear power plants and one coal-fired plant generated more electricity in 2021.

Combined-cycle power blocks have increased in average capacity since 2015, when a new class of combustion turbines became more common. These newer combustion turbines allow combined-cycle power blocks to have larger capacities and improved efficiencies. The average capacity of a 2x1 power block increased from 500 MW for those built before 2015 to over 700 MW for those built after 2015.