Cape Wind Associates has been given the green light on a project to build a data-collection tower that could lead to the largest renewable-energy plant in the United States — 170 windmills off the coast of Cape Cod, Mass. The collection tower, opposed by locals for its possible harm to tourism and the environment, will collect information on air and water turbulence, the direction and velocity of wind, wave heights, and currents; data from the testing pole will be used for engineering studies and an environmental impact statement for the proposed renewable-energy project. An attorney representing Ten Taxpayers, the citizens group that filed a restraining order against the project, called the tower a “Machiavellian attempt by Cape Wind to pierce the Continental Shelf” and “get a foot in the door.”