Walmart WMT is taking a big step toward fulfilling its long-term ambition of being wholly supplied by renewable energy with a new deal to buy more than half of the electricity generated by a new wind power facility in Texas for the next ten years. The world’s largest company will buy 58% of the expected output of Pattern Energy Group’s PEGI 200 megawatt Logan’s Gap Wind facility in Comanche County, Texas (150 miles southwest of…