Siemens said it would supply 65 2.3MW turbines and 67 transformers to the site, with installation expected to begin. The project is due for completion in early 2016. The contract also includes a servicing deal.
Amazon Web Services, owned by the online retailer Amazon, agreed a 13-year power purchase agreement with the project in January. It also changed the name of the project from Fowler Ridge.
As part of the deal with Pattern Energy, Siemens' financial services unit, will provide $150 million in construction financing.
AWS has pledged to power its entire infrastructure using renewable energy, which is becoming an increasingly popular source of power for data centres.