Data Center Dynamics


Solar Sums

A roof of solar panels wont power your site, but it could payoff, discovers
Michael Kassner

Plenty of data centers use solar power. Apple has been buying it up wholesale. But do the numbers really add up? Alongside the positive stories, there has been some skepticism, in particular from James Hamilton, data center guru, and vice president and distinguished engineer at Amazon Web Services, who wrote a blog in 2012. An entry entitled ‘I Love Solar Power But .. .’ asked some tough questions, and is still making waves today. “I love solar power,” wrote Hamilton, “but in reflecting carefully on a couple
of high-profile data center deployments of solar power, I’m developing serious reservations that this is the path to reducing data center environmental impact.”

Hamilton’s primary concern was, and still is, the way solar-array power capacities are advertised. All too often, reports simply quote the maximum output of a solar array, without taking into account two real-world variables that reduce the array’s capacity (see box).

Hamilton’s post got attention because he used Apple’s Maiden, North Carolina, data center and Facebook’s Prineville, Oregon, data center as examples. When Hamilton included the variables – location and altitude – in the capacity calculations, the output from the solar arrays at Prineville and Maiden barely made a dent in the power requirements for either data center. Regarding Apple’s Maiden data center, Hamilton’s calculations suggested that a solar array that supplied all of the data center’s power would have to cover over 4,000 acres.

Since 2012 things have obviously changed, and I was curious if Hamilton had any further thoughts. Via shipboard email, he wrote:
“Both Apple and Facebook continue to invest in renewable energy, but it is still hard to fathom just how much space is required to fully power a large data center.”

It is evident that solar needs a lot of space: First Solar, a provider of photovoltaic solar energy solutions, affords us an idea with its California Flats solar project. The 280-megawatt solar array occupies around 2,900 acres in southeast Monterey County, California. finances: “As I work through the numbers … they just don’t seem to balance out, unless tax incentives are included. I’m not convinced having the tax base fund data center deployments is
a scalable solution. And even if it could be shown that this will eventually become tax-neutral, I’m not sure we want to see data center deployments consuming hundreds of acres of land on power generation.”

Hamilton’s original post also generated some thought-provoking comments. “Your analysis seems mostly correct, but I have an alternate proposal,” Dave Anderson responded on the blog. “Solar plus data center is not an answer to how I power my data center. It is an answer to the question: I just built this huge building, what do I do with the roof?”

If there is enough solar energy to make a solar array cost-effective, there are actually other benefits, argued Anderson. The panels will also shade the roof and reduce heat build-up – a win-win situation. “In Dave’s approach, we don’t get a substantial change in the grid power consumption, but we reduce the heat load while getting 0.25 percent of the building’s power requirement,” responded Hamilton. “I think it could work. It’s worth thinking through more carefully.”

I followed this thought on a recent visit to Fort Myers, Florida. One of my stops was Synergy Networks, a local ISP that also provides colocation and  hosting services. My contact at Synergy did not know it, but I had an ulterior motive for my visit. Synergy Networks has a data center and a roof-mounted solar array. As Ken Boyd, vice president of finance and business development, showed me around, he noticed my interest in a large conference room monitor that was tracking the solar array’s performance.

Boyd showed me a picture of the building’s roof. It’s stuffed full of solar panels. The array consists of Trina Solar 60 cell, 250-watt, 15.6 percent maximum-efficiency panels that are wired together using micro-inverters, and management software from Enphase Energy. The total array outputs 44kW.

ls it cost effective? Boyd gave me the numbers. An average week nets 1.5-megawatt hours from the array, and it replaces on average $500 worth of grid electricity each month, giving a five-year payback. Boyd made it clear that this installation makes sense, but he agrees with Hamilton: solar-energy projects are not viable without incentives, and in Synergy Networks’ case, the federal government’s Solar Investment Tax Credit and the Florida Power and Light (FPL) solar rebate.

The federal tax credit amounts to a reduction of the organization’s tax obligation equal to 30 percent of the out-of-pocket cost of the system. Boyd said applying for the tax credit was just a matter of filling out paperwork. However, the FPL solar rebate is not quite that simple. At the designated time and date, the FPL solar rebate application website goes live. Within seconds, those interested in getting a rebate start entering data as fast as they can. It is first come first served, and when the designated amount of money runs out, the site closes.

Boyd said he practiced entering the information just to make sure Synergy Networks’ application made it. The year Boyd applied (2013) the website closed after one hour. The 2015 rebate application was even more of a race. Alissa Jean Schafer, marketing and media director at US Solar Institute, said: “Residential solar rebate funds were all claimed within the first 30 seconds. Business solar rebates followed suit and were completely claimed in the next three minutes.”

It is easy to see why. Without $75,000 from the FPL rebate program and the federal tax credit, Boyd said the company’s payback would grow from five years to 25 years.

Commenting on the Synergy Networks installation, Hamilton said he still likes the idea of a rooftop solar array as an additive source of renewable energy: “It’s clearly a good business decision in many jurisdictions with favorable tax benefits, but it will not meet the total power needs of the facility.”

There are also intangible benefits from using a renewable resource such as solar power. It allows positive marketing. Boyd agreed, telling me clients are impressed the company is dedicated to renewable resources.

It’s also important to Synergy staff. ‘The fact that Synergy is helping reduce its impact on the environment by using solar power makes me proud to work here,” said Logan Tygart, senior system administrator. “It’s interesting to see how much electricity the array is producing at different times of the day.”•

Hamilton asked us to mention that the opinions expressed here are his own and do not necessarily represent those of his employer.


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