Apple is planning to build a second mid-size data center on its property in Maiden, North Carolina, which currently has one 500,000 sq ft facility and a smaller, 21,000 sq ft one.

The company has filed papers for a permit with Catawba County that describes a 14,000 sq ft data center at the site, Hickory Record reported. Plans in the paperwork include a building with office and other ancillary space and a data hall cooled by 11 air conditioning units.

Apple's Maiden data center campus is famous for a unique approach to sourcing energy. Using a mix of fuel cells, solar panels and renewable energy credits, Apple claims the facility is 100% carbon-neutral.

The company has built a 100-acre 20MW solar array next to the data center and another 20MW array in the vicinity. It has also bought 10MW of fuel-cell generation capacity from Bloom Energy.

In March 2013, Apple announced that it had reached 100% renewable energy across all of its data centers, including, in addition to Maiden, facilities in California, Texas, Ireland and Germany.

Like other famous technology companies with massive data center requirements, Apple has been under pressure to clean up its power supply, reducing reliance on coal in favor for more environmentally friendly alternatives.

Companies like Facebook, Microsoft, Google and Twitter have been under similar pressure, thanks in part to Greenpeace, which started a campaign several years ago to publicize the role of coal power in operations of companies whose products and services have permeated everyday life.