Solar Power at Data Center Scale

Solar power has finally reached data center scale. Phoenix IT infrastructure provider i/o Data Centers is installing a huge array of solar panels on the 11-acre roof of its new Phoenix ONE data center. The company says the photovoltaic panels will generate up to 4.5 megawatts of power to supplement the energy needs of the massive facility.

The installation planned for Phoenix ONE will dwarf all previous efforts to integrate solar power into a working data center. Its output will be nearly three times the 1.6 megawatts produced by the solar panels covering the roof of the Googleplex.

The first phase of 5,000 solar panels in Phoenix is scheduled to be operational in January, and will generate 500 kilowatt-peak (kWp), the company says. The array will be expanded in four additional phases during 2010 to reach a total capacity of 4.5 megawatts-peak.

That’s just a fraction of the 80 megawatts of power capacity that the 538,000 square foot Phoenix ONE data center will need upon completion. The solar power is also expensive, costing about 18 cents per kilowatt hour to generate in a market where grid power is 7 cents.

Time-Shifted Cooling
But Phoenix ONE plan capitalizes on another wrinkle in power pricing: the differential between the daytime and overnight rates. The solar plant will be combined with an on-site thermal storage facility to create a time-shifted energy efficiency system.

i/o Data Centers will run its chillers at night when power is cheap, and then tap the thermal storage “battery” to provide much of the facility’s cooling during the day, reducing its power usage when electricity is most expensive. The solar power panels will further rlower Phoenix ONE’s reliance on utility power during peak hours.

“If we can generate 3 megawatts during the day, combined with our thermal storage, we can shave our power costs by about 50 percent,” said George Slessman, the CEO of i/o Data Centers. “Anything I can do to move my power consumption to off-peak hours is going to save a lot of money. Solar is the renewable approach that works best during peak daytime power pricing.”

The Challenges of Solar
Solar power hasn’t been widely used in data centers because of the large amounts of energy required to power the servers and cooling equipment in modern mission-critical facilities. It requires a very large installation of photovoltaic (PV) solar panels to produce even a fraction of the energy required by most data centers.

The only data center currently powered entirely by PV solar power is AISO (Affordable Internet Services Online), which operates a 1,500 square foot facility in Romoland, California. Intel and Sun Microsystems have tested solar power systems generating 10 kilowatts to partially power data center containers.

PV solar is also much more expensive than grid power. Microsoft has discussed plans to install solar panels at its San Antonio data center, but said such a system wouldn’t be economically feasible in the near future. “As solar technology advances, we anticipate that solar may become a more viable option within a few years,” the company said.