Because data centers account for an increasing percentage of the world’s energy consumption, alternative energy sources (particularly if they are less expensive than the current energy mix) are of interest to the industry. Most data centers today rely on coal-based energy, along with a smattering of nuclear, hydroelectric, solar and wind sources. A few facilities have the benefit of even more-novel sources like geothermal energy. But coal is king; does any other energy source—whether now or in the future—stand a fighting chance? Here’s a brief look at what’s out there and what might be on the horizon.
- Coal. Sitting at the top of the heap is the energy source with the poorest PR rating (with the possible exception of nuclear power). Pluses: Coal is fairly abundant, and extensive infrastructure is already in place to generate power from it. It is also safe to handle, posing little direct risk, and it enables continuous energy production. Minuses: Coal mining is dangerous or environmentally destructive (or both), and burning coal produces a variety of emissions.
- Nuclear. Following the Fukushima disaster, nuclear energy has fallen more than a couple notches in its palatability to the general public. But it is perhaps the only energy source that currently stands a fighting chance to replace coal. Pluses: Nuclear reactors use relatively small amounts of fuel to produce large amounts of energy. Like coal, it enables a continuous supply of energy proportional to demand. Emissions are negligible, assuming containment of the nuclear materials is maintained. Potential also exists for development of safer reactors, such as those that use thorium. Minuses: Standard nuclear reactors use radioactive fuel, which also leaves behind radioactive waste products that must be carefully disposed of. Attacks or accidents—such as occurred at Fukushima—can wreak extensive damage on people and the environment. And if you want to explore alternative nuclear technologies, be sure not to offend the thorium cheerleaders, or they’ll beat you with their pom-poms.
- Solar. Solar offers a number of advantages, and some data centers (such as Apple’s Maiden, North Carolina facility, which is under construction) employ their own solar infrastructure. It is the most accessible energy source for direct power generation by individuals and small companies. Pluses: The sun is a virtually inexhaustible supply of energy, and it is available to everyone, free of charge. Conversion of light into electricity produces no emissions, and the infrastructure is safe and can be implemented on scale ranging from very small to fairly large. Minuses: The sun shines on average for only about half the day, meaning energy production is limited to half time. For nighttime use, daytime energy must be stored, requiring battery banks. Furthermore, a significant area of solar panels is needed to meet all the energy needs of a typical home or business, and data centers would require even more, owing to their energy appetites. Factors such as seasons and weather also cause variation in the amount of energy produced, making solar power unable to act as a constant energy source. In addition, solar panels are fairly expensive, and the recent Solyndra debacle inspires little confidence in the economic feasibility of solar.
- Wind. Wind is about on par with solar, offering a tempting alternative, but one that has little potential to compete on a large scale with coal and nuclear. Pluses: Like solar, wind relies an a safe, abundant energy source: air movement. Harnessing wind produces no waste products, and it can also be implemented in a variety of scales. Minuses: Obviously, wind energy is only available when the wind is blowing, and these conditions can vary from minute to minute. Wind is therefore not a reliable source of energy, although it is not limited to daylight hours, as solar is. Mining practices for the magnetic materials used in wind turbines also raises some environmental concerns, as do the effects of these turbines on birds and even the aesthetics of the land or ocean. Wind energy, like solar, can be a good supplement to a more consistent energy source like coal or nuclear, but it cannot alone meet the world’s power demands.
- Hydroelectric. By relying on gravity and the natural movement of water by atmospheric processes, energy can be extracted from rivers. Some data centers are intentionally located near sources of hydroelectric power. Pluses: As long as the river is flowing, hydroelectric turbines will keep running. Thus, they provide a fairly consistent energy supply without producing emissions and without needing large amounts of area like wind or solar farms. Minuses: The construction of dams for hydroelectric power purposes often necessitates flooding of a large area of land. Furthermore, these dams can disrupt water ecologies owing to the obstruction of waterways and to the heating of water. Seasonal or longer-term variations in water level can also affect energy production, and failure of a dam can result in catastrophic flooding of surrounding (often populated) areas. Generally, hydroelectric requires fairly large-scale infrastructure that’s accessible only to fairly large energy companies.
- Geothermal. Geothermal energy is abundant in some places, and it can even provide a broader means of supplying small amounts of energy for certain uses. Iceland offers a unique location for data centers, as it has a relatively cold climate (good for cooling) and abundant geothermal energy (to help power the facility). Pluses: Geothermal energy is simply heat contained in the Earth, and using it doesn’t produce emissions or other harmful waste products. Even in average locations bearing no resemblance to Yellowstone Park, the relatively constant temperature of the ground can provide a means of heating in the winter and cooling in the summer. Minuses: Locations with abundant geothermal energy are also often subject to geological threats such as earthquakes and volcanoes. Geothermal thus offers a novel source of energy in some isolated cases, but pending some new technology for harnessing it in a larger-scale manner for electricity, it has little chance of competing with some of the other technologies listed above.
- Fusion. This energy source moves closer to the realm of science fiction. Fusion is a real process, and can yield large amounts of energy—the problem is employing it in a manner that both yields abundant energy and is economically feasible (the bane of many an energy source). Pluses: Fusion is something of a holy grail in science and engineering. It offers the potential for a continuous, large-scale energy source that produces no harmful wastes, which could make it a competitor with coal and nuclear. Minuses: Achieving fusion at low (i.e., manageable) temperatures is challenging, and the means to enable controlled, large-scale fusion have yet to be demonstrated in both a technically and economically feasible manner. Fusion offers many potential benefits, but its usefulness as an energy source may have to remain science fiction.
- Biofuel. Ethanol is the standard-bearer for biofuels. You may even remember having seen an ADM (Archer Daniels Midland) commercial about how obtaining ethanol for fuel simply requires growing more corn—a tempting prospect. Pluses: On the surface, biofuels seem like a no-brainer. Let some organisms (plants, bacteria or whatever) do all the work, then simply reap the energy rewards. Of course, some refinement is generally required, but in principle, the system is feasible. Minuses: What do you get when you combine propaganda, government money and a hugely subsidized farming industry? Ethanol. Presumably, ethanol reduces the need to drill for oil (along with its associated hazards), but apart from its harmful effects on engines, ethanol reduces gas mileage in automobiles and is arguably just a gimmick intended to further subsidize agribusiness. The idea of simply growing energy sounds great—until you realize that producing corn requires vast amounts of (petroleum-based) fertilizer to supplement the soil, which has already largely been stripped of nutrients by overfarming. Biofuels are generally overhyped, and although they may have some application, they are unlikely to offer an energy source of any major consequence.
- Other sources. Star Trek fans might ask about antimatter. Yes, antimatter and matter combine to create a relatively large amount of energy (E = mc2), but antimatter is rare. Furthermore, containment of antimatter is problematic—as Federation starships discovered in numerous TV episodes. Even more-exotic energy sources, like zero-point energy, are controversial with regard to their usability. They are fascinating because of their hints at virtually limitless free energy, making us wonder how much better life would become, but they have yet to see practical application. This isn’t to say that some marvelous new form of usable energy won’t be discovered, but neither is it intended to provoke excessive optimism.
Given the present status of science and technology, a mix of energy sources seems to be the most likely prescription for the future. No one source meets global energy demand without some drawbacks. For data centers in particular, a mix of coal, nuclear, hydroelectric and solar seems to be the most likely energy diet for at least the next decade, although nuclear seems to have a precarious future. These facilities will generally remain “on the grid,” as home-generated power sources have yet to advance to the point that they can provide sufficient energy to meet requirements. This is particularly true in urban areas, where space limitations prevent installation of company-owned power-generation infrastructure. No doubt, however, the progress of energy science will be interesting to observe.
Photo courtesy of Marcel Oosterwijk