Oklahoma continues to be one of the nation's leaders in adding renewable energy, but it's getting tougher to get that power on the grid. The state was in the top-five for its additions of wind, solar and storage resources to power transmission systems across the nation during the third quarter, according to the American Clean Power Association. But developers are finding it difficult to secure the approval for the needed infrastructure to get power onto the grid that serves Oklahoma and parts or all of 13 other states across the Great Plains.