Apple is building something at its Maiden, North Carolina, data center, but the uber-secretive company won't say what it is.

So Wired took to the skies to find out.

These overhead photos – captured last month – show Apple's $1 billion data center and two adjacent areas where Apple has started new construction. Rumors have suggested that Apple is building a second data center beside the first, but judging from these photos – and county building permits – it appears that this is not the case. In all likelihood, the two construction areas will house the new-age biogas fuel cell plant and the massive solar array Apple will use to help power the original facility.

The Maiden data center is home to Apple's iCloud service, a way for consumers and businesses to store files, photos, and other data on the web and use it across a wide array of devices. The data facility itself cost $500 million, but Apple has pledged to spend $1 billion on the site over the next decade. Opened for business around the beginning of the year, the Maiden center is just one of the many custom-designed data centers the giants of the web are building to supply their ever-growing array of web services. Google has built several of its own dedicated data centers across the world, and the likes of Microsoft, Facebook, and Yahoo aren't far behind.

The iCloud has been growing like gangbusters since it was introduced last fall, and when Apple pulled a few construction permits early last month, that prompted speculation that the company may be doubling down and building a second data center on the site. But clearly, that's not the case – though Apple is starting to build a new data center on the other side of the country, right next door to Facebook's massive facility in Prineville, Oregon.

To power its data center, Apple is building both a biogas fuel cell plant and a solar array. Photo: Garrett Fisher/Wired

Apple's North Carolina permits describe a 21,030-square-foot building. That's bigger than your typical Apple Store, but not nearly big enough for the sort of data center Apple would build. The company's existing Maiden facility is 500,000 square feet.

More likely, the new building will house the 24-200 kilowatt fuel cell systems that could be partially operational as soon as June. This plant is noteworthy, as it will be one of the largest such plants in the U.S. and it's the biggest such project built by a data-center operator.

But judging from our photos, even when the biogas plant goes live, Apple will still have room to squeeze a second massive data center into the spot – should the need arise. Maiden Town Planner Todd Herms told us where the solar array was being installed, but he didn't know if the new building next to the data center was the biogas plant or not.

A second, somewhat sobering observation is that Apple had to mow down an awful lot of trees in order to build its environmentally friendly 100-acre solar array, right across the street from its data center. You can see the before and after photos here:

Before construction, there were 100 green acres on the other side of Maiden's Startown Road. Image: Google Earth

Now it's been razed, to make way for Apple's solar array Photo: Garrett Fisher/Wired

Apple solar array effort has already come under fire from a data center guru James Hamilton at rival Amazon, who said last month that it just may not make sense to use so much land for a solar array that may end up generating a fairly small fraction of the data center's power. Apple bills its solar farm as a 20-megawatt array, but that represents the solar farm's peak capacity on a sunny day. In reality, it will probably produce less power than the 4.8-megawatt biogas facility, according to Gary Cook, an IT analyst at Greenpeace.

Apple didn't respond to our request for comment on this story. It's working hard to lose its reputation as a builder of environmentally unfriendly data centers, and according to Todd Herms, Apple went out of its way to meet or exceed environmental regulations every step of the way. For example, when the town told them they had to build a retention pond to protect the nearby river from storm water runoff, Apple didn't use any of the standard techniques to push back on the project. They simply did what they were asked to do. "That made my life easier," he says. "It was just so much easier dealing with them."

But Apple finds itself in this situation because it's trying to reduce its reliance on the environmentally unfriendly energy sources – primarily coal and nuclear – that power the Duke Energy grid that Apple uses, says Greenpeace's Cook. "They're trying to do what they can onsite to reduce their emissions footprint," he says. "It's a very dirty energy grid – North Carolina is 60 percent coal, and this is one way to try to reduce that load."

Because of Apple's secrecy, there's already a fine history of Maiden flyovers. Wired wasn't the first to do it. And, no doubt, we won't be the last.