TransAlta Corporation is an electricity power generator and wholesale marketing company headquartered in Calgary, Alberta, Canada. It is a privately owned corporation and its shares are traded publicly. It operates 76 power plants in Canada, the United States, and Australia. TransAlta operates wind, hydro, natural gas, and coal power generation facilities. The company has been recognized for its leadership in sustainability by the Dow Jones Sustainability North America Index, the FTSE4Good Index, and the Jantzi Social Index. TransAlta is Canada's largest investor-owned renewable energy provider. The company is not without controversy, as the Alberta Utility Commission ruled in 2015 that TransAlta manipulated the price of electricity when it took outages at its Alberta coal-fired generating units in late 2010 and early 2011. TransAlta operated Canada's largest surface strip coal mine from 1970 until 2021 through its subsidiary company Sunhills Mining. The 12,600 hectare mine produced 13 million tonnes of thermal grade coal a year. The company announced that it would be decommission the Highvale mine by 2021. Wikipedia