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.

An aerial view reveals the full scope of the massive solar array in East Windsor, N.J. (Photo: McGraw-Hill)

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.

The McGraw-Hill data center occupies 180,000 square feet of the 360,000-square-foot facility and uses about 4 megawatts of power. When the array is operating, surplus energy is shared with JCP&L through a net metering agreement. Net metering allow consumers to generate electricity at their premises, interconnect with the local power grid, and use their on-site generation to offset electricity purchased from the local utility.

The solar field is operated by New Jersey Resources, which invested $60 million to build the facility in 2011. QTS owns the land and data center, which were acquired from McGraw-Hill last year for $75 million. The McGraw-Hill facility is maintained by global IT outsourcing firm Atos, which is leasing the space from QTS. The arrangement marks the debut of the QTS Critical Facilities Management service offering, in which it manages entire data centers for enterprise companies and service providers.

The solar array is located about a quarter-mile from the data center, with two 34.5kV power feeds running back to the data center, providing A and B feeds for redundancy. The 50-acre solar farm is dotted with 12 transformers and 24 inverters.

Some of the more than 57,000 solar panels at the QTS Princeton data center campus. (Photo: Rich Miller)

The output of the array declines in the winter, when days are shorter. There's also the snow, which is an issue since the photovoltaic panels are ground-mounted. New Jersey averages about 26 inches of snow a year, but was hit with a brutal 54 inches of snow last winter. Fortunately, the arrays are designed to continue to generate power even if the lower portion of the panel is snow-covered - a condition which rarely lasts long, as the panels warm in the sunlight and melt the snow.

QTS has experience with on-site solar arrays. In 2012 the company announced plans to install 1 megawatt of photovoltaic generation at its campuses in Richmond, Virginia and Atlanta Metro.

Is solar the best path to a renewable cloud?

The data center industry’s commitment to renewable energy has come under fire from the environmental group Greenpeace. The emergence of these huge solar farms has blunted some of those critiques, but there’s been an active debate among data center thought leaders about the value of these huge solar installations, with some questioning the tradeoff of cutting down trees to make room for solar panels (as Apple did in North Carolina).

There's also the cost of solar energy. The price of photovoltaic panels has declined in recent years but remains well above "grid parity" where it can match the cost model of utility generation. That's why many large projects rely upon incentives to make the economics work. The initial McGraw-Hill project benefitted from a 30-percent federal investment tax credit, and its output is eligible for Solar Renewable Energy Certificates (SRECs), which can be sold to Load Serving Entities in New Jersey to meet their renewable energy requirements.

Having just assumed ownership of the facility, QTS is still studying the financial impact of the solar generation at the East Windsor site. "I definitely think there will be a case study about the benefits of (the solar array)," QTS Vice President of Operations and Critical Facility Management Danny Crocker said.

In the meantime, New Jersey is gaining a reputation as a haven for data center solar projects. In addition to the QTS Princeton facility, DuPont Fabros maintains a 2-megawatt solar energy system on the rooftop of its huge data center in Piscataway.

An aerial view of the massive solar power array on the roof of the DuPont Fabros NJ1 data center in Piscataway, New Jersey (Photo: DuPont Fabros Technology.)