Facebook has agreed a deal to purchase the energy produced by a planned wind farm in Co Tipperary.

The social media firm has signed a Corporate Power Purchase Agreement with Brookfield Renewable Partners, which is to build its 28.8 megawatt 'Lisheen III' wind farm over the next two years.

When completed it will be capable of producing enough energy to power 20,000 homes, offering a potential reduction in Co2 of 32,000 tonnes each year.

The deal is part of a wider plan by Facebook to become wholly-reliant on renewable energy this year, while reducing its greenhouse gas emissions by 75%.

It said its Irish operations - which include its international headquarters in Dublin and a data centre in Clonee, Co Meath, are already entirely powered by wind energy.

Major companies are increasingly using Corporate Power Purchase Agreements to secure access to a long-term supply of renewable energy.

They also appeal to wind farm operators as they can ensure there is demand for the new supply before having to incur the cost of construction.

In some cases the agreement can also involve the buyer putting forward an advance to help fund the project.

Brookfield said the agreement with Facebook is what has made the development of Lisheen III possible.