Buffalo Gap 2, Texas, USA

AES has started commercial operation of the 233MW Buffalo Gap 2 wind farm expansion near Abilene, Texas. The project expands the company's 121MW Buffalo Gap wind farm which began operations near Abilene in 2006. It makes the project the third largest in the state, with a total wind power capacity of 354MW. This is enough to power around 100,000 homes.

Under a ten-year power purchase agreement, AES will sell the electricity to Texas retail electric provider Direct Energy at a fixed price. Financial terms of the project were not disclosed, but the expansion is thought to have cost around $200m. AES bought 155GE 1.5MW wind turbine generators for the project. D.H. Blattner & Sons, Inc. is the engineering, procurement and construction contractor.

AES has already announced plans to start constructing Buffalo Gap 3, a further wind farm of 170MW capacity. Expected to be complete by the middle of 2008, the project will increase total capacity to 524MW.

AES has bought 74 Siemens wind turbine generators for Buffalo Gap 3. A seven-year power purchase agreement will sell all the electricity produced to Direct Energy, a subsidiary of Centrica.

155GE 1.5MW TURBINES WITH WINDCONTROL

The 1.5MW wind turbine is active yaw and pitch regulated with power/torque control capability and an asynchronous generator. It uses a bedplate drive train design with all nacelle components joined on a common structure for durability. The generator and gearbox are supported by elastomeric elements to minimise noise emissions.

GE's WindCONTROL system regulates voltage and power in real time. Like a conventional power plant, the system supplies reactive power to the grid when it is needed, regulating system voltage and stabilising weak grids. GE provides a simple integrated system of VAR control by using the dynamic VAR capability inherent in the variable speed turbines as the main VAR source – others may need add-on capacitors or VAR compensators.

GE's WindCONTROL system can seamlessly integrate capacitor banks if greater VAR capability is required. The system also controls the power of the wind plant by using variable-speed technology. Each turbine maintains precise torque and pitch regulation, controlling power and speed during changing wind and grid conditions.

Conventional power plants include governor droop, controlled rates of change during power setpoint changes, and controlled shutdown and startup routines. Even with more than 100 turbines reacting to different wind conditions, GE's WindCONTROL system can make a wind power plant operate more like a conventional thermal one.

The WindCONTROL system also satisfies many emerging grid code requirements related to wind plant power response. Features include maximum power limits, power-frequency droop, power ramp rate limits, startup/shutdown, integrated capacitor/reactor bank control, line drop and voltage droop compensation.

TEXAS BOASTS HIGHEST WIND POWER OUTPUT IN US

The US is planning to install over 3GW of wind power capacity in 2007. Texas is likely to account for about two thirds of the new installations, according to the American Wind Energy Association (AWEA), largely due to its renewables portfolio standard and other incentives for renewable generation. Texas currently has the largest wind power output in operation in the US.

AES entered the wind generation business in 2004. Today, the company has more than 1GW of wind projects operating in the US and another 4GW in development throughout the world, primarily in the US and Europe. AES has plans to expand its wind business to other countries where it does business, including countries in Asia and Latin America. The company intends to more than triple its wind-generated power by 2011.

AES expanded its wind generation business to Europe with the acquisition of a majority stake in Wind Energy Ltd. (WEL) group companies, a UK-based wind development company. WEL currently has 640MW of wind generation projects under development throughout Scotland.

Direct Energy is part of the Centrica group of companies, one of the largest multi-state providers of deregulated retail energy services in North America, and the third largest retail energy provider in the state of Texas. The company has customers in nine US states and in Canada.