The Los Vientos II project will be located in Willacy County, 20 miles inland from the Gulf of Mexico.
Duke has a 25-year power purchase agreement in place for the project with Austin Energy.
The project is expected to be commissioned by the end of 2012 and is the second phase of a 402MW project. Los Vientos I was announced in August.
Other Duke projects announced this year include two projects in Kansas — 168MW Ironwood project in Ford County, 131MW Cimarron II in Gray County.
It is building the 69MW Laurel Hill project in Lycoming County, Pennsylvania and the 20MW Shirley development Glenmore, Wisconsin. The latter project is already in operation.