Business Green: Just days after finally securing planning permission for the first offshore wind farm in the US, developer Cape Wind revealed that it has pulled in its first customer in the form of grid operator National Grid. In what has been described as a "landmark move", National Grid and Cape Wind will today file a contract with the Massachusetts Department of Public Utilities that will see the UK-based grid operator buy half the wind farm’s output for 20.7 cents per kilowatt hour, including …