IDA COUNTY— MidAmerican Energy says it will build its next two wind farms in northwest Iowa. The company says there will be 134 generators at the Ida County site and 104 at the site in O’Brien County, providing a combined capacity of 552 megawatts. The estimated investment for the two projects is $900 million. By the end of the year, more of the company’s electricity will come from wind than from any other single source.