The cost of the expansion is estimated at $123-million, the Calgary-based company said in a statement. Construction is scheduled to start next year and power generation in the first quarter of 2010.
A growing population and increased industrial demand, partly from rising tar-sands output in Alberta, are forecast to boost electricity demand 3% a year over the next two decades, according to the agency that oversees the province's power industry.
TransAlta said it also may develop another 500 megawatts of wind generation in southern Alberta in the next five years.
The planned expansion of Summerview will boost generating capacity at the wind farm near Pincher Creek to 136 megawatts, enough power for about 55,000 homes and offsetting 257,000 metric tons of carbon-dioxide emissions, the statement said.
The company, the largest publicly traded power producer in Canada, derives about 62% of its net generation capacity from coal plants, according to the company's annual report.
TransAlta emitted 39.2 million metric tons of greenhouse gas emissions including carbon dioxide in 2007, up 4% from the previous year, said the company's annual report.