The power plant began operations ahead of schedule in May 2019. Credit: Entergy Corporation.
The electricity generated from the power station meets the needs of approximately 675,000 homes in Louisiana, US. Credit: McDermott International.

The St Charles Power Station is a 980MW combined-cycle gas turbine (CCGT) power plant located in St Charles Parish, approximately 48km west of New Orleans, Louisiana, US.

The power plant is one of the cleanest and most efficient power plants operated by Entergy Louisiana and will allow customers to save more than $1.3bn over the plant’s projected 30 years lifespan. The CCGT units emit approximately 40% less CO₂ than the company’s older natural gas-powered units.

The ground breaking ceremony for the St Charles Power Station was held in January 2017. The plant generates enough electricity to meet the needs of approximately 675,000 typical Louisiana households.

The construction of the St Charles power station created 2,000 direct and indirect jobs each year, with 955 temporary jobs during the peak construction period.

McDermott completed the development of the power plant ahead of schedule and began commercial operations in May 2019. The company turned over the power plant to the owner, Entergy Louisiana, in June 2019.

Entergy Louisiana hired 31 people, including 20 production technicians, to operate the plant. The plant increased the revenue of Louisiana businesses by $1.4bn and household net income by $476.8m.

St Charles Power Station background

The project was envisaged by Entergy Louisiana, a subsidiary of Entergy Corporation, to increase its electricity generation capacity to meet the power requirements of its customers. Following extensive analysis, a 20-acre site next to Entergy Louisiana’ existing Little Gypsy power plant was selected to build the new power plant.

The site allowed for the rapid deployment of work force and equipment for construction and commissioning of the power plant. It also offered high accessibility to waterborne transportation and transmission facilities, as well as existing river water inlet and gas pipeline infrastructure.

The preferred location offers the lowest reasonable cost alternative to provide electricity to the supply-constrained Amite South region of southeast Louisiana.

Plant make-up

The power plant is installed with two Mitsubishi Hitachi Power Systems (MHPS) M501GAC gas turbines, two Nooter Eriksen heat recovery steam generators (HRSGs) and a Toshiba steam turbine and generator (STG) in 2×1 CCGT configuration.

The M501GAC, which is the air-cooled variant of the MHPS G-Series turbines, develops higher power output and efficiency than the MHPS F-class gas turbines. It also offers more flexibility than a steam-cooled unit, while ensuring rapid start-up and lower emissions.

The combustion system of the gas turbine delivers higher power output and efficiency, as well as more flexibility and lower emissions, when compared with the steam-cooled unit. The natural gas-fired plant is digitally enhanced to further increase the plant’s performance.

The heat recovery steam generators (HRSGs) extract exhaust heat from the gas turbines to create steam that is piped to the steam turbine. The steam generated by the HRSGs is utilised to drive a steam turbine rotating another generator, while the remaining exhaust gas is transferred through the exhaust stack. The operator continuously monitors the emissions to meet air quality regulations.

Cooling water required for the plant is sourced from the Mississippi River. The small amount of leftover water from the steam is dispatched after it leaves the steam turbine and is piped to the cooling tower, where large fans blow air to cool the water.

The power station employs a closed-loop system, which reuses the water and only requires a small amount of make-up water from the river to offset evaporated water.

The power plant also includes three step-up transformers that increase the power voltage of the generator and feed the output into the grid network.

Contractors involved with the St Charles CCGT power plant

CB&I was awarded a contract by Entergy Louisiana for the engineering, procurement and construction (EPC) of the power plant in the second quarter of 2015.

MHPS was selected to supply two M501GAC gas turbines for the St Charles Power Station in January 2017.

Toshiba America Energy Systems supplied a steam turbine and generator for the power plant.