Business Green: Plans for the largest wind farm in the southern hemisphere took a leap forward today when Australian firm AGL Energy inked a deal with New Zealand-based renewable energy developer Meridian Energy to build a 420MW facility. The $1bn wind farm near Hamilton, 260km west of Melbourne, is due to be completed in early 2013. The site will consist of 140 Vestas turbines and will have the capacity to power more than 220,000 homes. AGL said the development would help to cut carbon …