Super-Sizing Solar Power for Data Centers

EAST WINDSOR, N.J. - Traveling east from Princeton, drivers can catch a brief glimpse of the panels, which are hidden by a series of high berms. It’s only when you walk around the edge of these grassy mounds of earth that the massive scale of the solar energy generation system is revealed.

And what a sight it is. The solar farm stretches nearly to the horizon, with blue and gray-green photovoltaic panels blanketing nearly 50 acres of New Jersey countryside. The system provides energy for the nearby QTS Princeton data center campus, more than 57,000 solar panels generating up to 14.1 megawatts of power. That’s more than enough to supply the daytime energy needs for McGraw-Hill’s electronic publishing operation, currently the sole tenant at the data center.

The QTS Princeton solar array symbolizes a new phase in the use of renewable energy in data centers. Massive arrays can now provide tens of megawatts of solar power for companies that can afford the land and the expense. As a handful of players pursue on-site solar farms, other cloud builders are opting for power purchasing agreements that subsidize new wind farms or tapping landfills for biofuels that can power fuel cells.

Scaling up for renewable energy

The use of solar power in data centers has come a long way since 2005, when AISO built the first fully solar-powered data center. The California hosting firm used 120 photovoltaic panels to provide all the power for a 2,000-square-foot data hall.

Solar power hasn’t been widely used in data centers because a very large installation of photovoltaic solar panels is required to produce even a fraction of the energy required by most data centers. An all-solar facility would either need to stay small or use thousands of solar panels deployed across dozens of acres of land.

Until recently, that type of large-scale solar array seemed impractical. Data center companies, under pressure from environmental groups like Greenpeace, opted instead for on-site arrays in the 100-to-200-kilowatt range that generated enough electricity to power office space within a facility. Companies adopting this approach included Facebook, Emerson and Cisco, among others.

In 2011 McGraw-Hill announced its ambitious plans for its East Windsor data center. The $60 million facility was built to support the data center on McGraw Hill’s nearby campus, which powers its Standard & Poor’s investment ratings, energy pricing services from Platt’s, and the Connect learning platform for higher education.

The company cited its focus on sustainable business practices as the motivation for the solar farm. By using the sun to power its data center during the day, McGraw-Hill said it achieved the same environmental impact as eliminating the carbon output for 1,580 homes or nearly 2,500 vehicles.

As large as it is, the QTS installation isn’t even the largest of new solar farms. Apple has built two 20-megawatt solar arrays near its campus in Maiden, North Carolina, and plans similar large solar fields to supports its new server farm in Reno, Nevada.

Even at cloud scale, solar power is a part-time solution — it’s only available when the sun is shining. Since most data centers are online around the clock, a solar-driven facility will need alternate power. When the sun goes down, QTS switches over to grid power from the local utility, Jersey Central Power & Light.