In a recent blog post, James Hamilton writes that he couldn’t “make the math work” for the completed solar array at Facebook’s Prinevill, Ore., facility or the proposed system at Apple’s iDataCenter in Maiden, N.C., and questioned whether the solar farms’ environmental impact was “purely optical.”
Facebook’s 100 kW array was installed at a 25 MW facility meaning, according to Hamilton, that it potentially provides just 0.4 percent of the facility’s overall power.
Digging deeper, Hamilton uses a solar panel output estimator, and data on the array’s geographic location, to suggest that the actual electricity generated might be closer to 0.055 percent of facility power – enough to run the lights at the data center but have “no measurable impact” on the facility’s energy consumption, Hamilton writes.
A similar story is evident in North Carolina, Hamilton, says. He conservatively estimates that the Apple data center should have a critical load of around 60 MW. At a moderate Power Usage Efficiency of 1.3, the Maiden facility would be at 78 MW of total power, Hamilton says. The huge 20 MW solar array, when adjusted for location and altitude using the estimator, would have an average output of about 15.8 percent of its capacity – or 3.2 MW.
Using this rationale, Hamilton argues that a solar facility big enough to power the whole data center would need to be 181 million square feet. Each square foot of data center would require 362 square feet of land taken up by solar panels, Hamilton argues. When federal incentives and high set-up costs are taken into account, Hamilton doesn’t think that solar projects are cost effective either.
“As much as I like data centers, I’m not convinced that tax payers should be paying to power them,” he writes.