Solar power offers an enticing alternative to traditional energy sources, especially for an industry that is becoming increasingly notorious for its huge and growing power appetite. Apple’s Maiden, North Carolina, data center will be powered in part by a huge solar array, but is this solar energy project showing a glimpse of a solar-powered future, or is it just a marketing tactic for the computer giant?
Apple’s Solar Plant
According to DatacenterDynamics (“Apple confirms solar farm at Maiden data center”), Apple’s Maiden campus will include a 100-acre solar array with a peak output of 20MW, producing about 42 million kWh per year. Doing a little math, the yearly output translates to an average output of a little less than 5MW. (If you double that to very roughly account for nighttime hours, the array will provide an average of between 9MW and 10MW during daylight hours.) According to the U.K.’s Register (“Apple slaps mega-solar panel field on new ENORMO data centre”), the Maiden data center will consume on the order of 50MW to 60MW; some wilder estimates even put it as high as 100MW. In either event, the solar array—as huge as it is—will only cover a maximum of about 10% of this consumption.
Nevertheless, even though the solar array accounts for a relatively small percentage of the facility’s expected power needs, it is still significant and will no doubt provide some insight into the feasibility of the sun as a practical large-scale energy source. Apple’s addition of the solar array in North Carolina no doubt scores it some marketing points by enabling it to boast of concern for the environment—and there’s no reason to think the company wants to “destroy the planet.” But ultimately, making money is what drives business, so Apple is no doubt exploring the potential of solar power as a means of lowering its energy costs. After all, sunlight is free. The infrastructure has an associated cost, as well as maintenance expenses, but the investment offers significant potential returns in the long term.
An important question remains, however: does solar energy really have the potential to meet the data center industry’s (or world’s) power needs?
Solar Power’s Potential
Let’s do some more math. Electromagnetic solar radiation (all frequencies, including visible light) constitutes about 1,350 watts per square meter—the solar constant. This number simply means that if you held up a solar panel that is one square meter in area, you could theoretically get 1350 watts of power—enough to power about thirteen 100-watt light bulbs. But this number is the solar incidence just outside the atmosphere; what’s received at ground level is less, owing to losses as the radiation propagates through air (these losses include scattering, such as off clouds, as well as absorption/heating). Atmospheric factors affecting the solar constant are manifold, but let’s assume about a 25% average loss, bringing the potential power to about 1,000 watts per square meter. To account for nighttime hours, cut that power number in half (and that’s being generous): 500 watts per square meter. Now, assume a solar cell can turn half of what it receives into usable power: we’re now down to 250 watts per square meter. Thus, a solar panel measuring one meter by one meter (about 10 square feet) would—assuming 12 hours of full daylight and a system to ensure the panel is always directed toward the sun—provide enough power to on average run two or three light bulbs continuously. Not bad, but not great.
Using this math, a 50MW data center would require roughly 50 acres of solar panels. Not 50 acres of land—the required land to support that much solar panel area would need to be much more, particularly if it is flat. Calculating numbers for the case of trying to tackle a large portion of the overall power consumption of the entire world is left as an exercise for the reader.
Solar Power: Not as Ideal as It Seems
Aside from the infrastructure aspects (such as manufacturing and maintaining all the solar panels and power distribution equipment to collect and supply all this power), there is the question of whether the disturbance of large portions of land, and the creatures that inhabit it, to create mega solar farms is warranted.
A blog article by James Hamilton offers a similar perspective. Hamilton notes that according to at least one model, Apple’s 20MW array “has an average output of 15.8% which yields 3.2MW.” So, needless to say, complete reliance on solar power would consume much more land area (again, Apple’s solar array will consume about 100 acres); as such, this approach isn’t practical for facilities located in urban areas or where weather conditions hamper efficiency. “I’m personally not crazy about clearing 171 acres in order to supply only 4% of the power at this facility. There are many ways to radically reduce aggregate data center environmental impact without as much land consumption,” Hamilton said in his blog.
For those concerned about carbon emissions, note that clearing land for a solar array also involves destruction of trees, which convert carbon dioxide into oxygen. The energy produced by the solar plant may outweigh the emissions of a coal plant for a similar amount of energy, but an exchange is made: solar power is not purely beneficial in this case.
Some market observers cite falling prices of solar infrastructure as an indication that it will become a more widespread and economically feasible means of supplying power. A GigaOM article (“5 reasons why Apple is embracing clean power for its data center”) notes that “Prices of solar panels and cells have plummeted recently... That’s bad news for the solar manufacturers — and has led to a wave of solar maker bankruptcies — but that’s good news for companies, utilities and home owners that are buying solar panels.”
The problem, however, is that if prices are so low that companies cannot sustain their manufacturing operations, then prices are being manipulated. Look no further than Solyndra for evidence—a highly subsidized company (to the tune of more than $500 million) went under, bringing to light the U.S. federal government’s manipulation of the solar industry. Hamilton’s blog article hits this point head on: “Looking more deeply at the Solar Array at Apple Maiden, the panels are built by SunPower. Sunpower is reportedly carrying $820m in debt and has received a $1.2B federal government loan guarantee. The panels are built on taxpayer guarantees and installed using tax payer funded tax incentives.”
Given the government’s current fiscal status—as well as its obvious penchant for manipulating markets with floods of money (from taxes or the printing press)—the economic feasibility of solar power cannot be judged on the basis of recent cost trends.
So, is Apple just pursuing the best interests of the environment, or is it pursuing its own financial interests? Probably a mix of both, and that’s perfectly understandable. The company’s solar farm at its Maiden data center site, however, will likely turn out to be more of a marketing gimmick than a true proof of concept for workable large-scale solar power. Reliance on the sun for energy will likely expand, but it seems most beneficial for small-scale supplementation (e.g., residential use) rather than a large-scale energy solution. For data centers—and, in particular, those in urban areas—solar power (especially private solar farms) is practically a non-starter as a significant source of energy.
Photo courtesy of h080