As any data center operator will tell you, data centers use large amounts of power. In fact, one data center can use enough energy to power 180,000 homes.
What with the costs and the eco-issues with fossil fuels, there's a race on to try to find better ways of powering these cathedrals to digital life.
Many heavy data center users are looking to place their centers near sources of renewable power, for example. Facebook has opened one in Sweden that's near a hydro-electric plant.
Solar is also pretty good, and wind-power turbines are another alternative power source attracting knee-jerk exuberance, despite their disadvantages, like uneven supply.

Pumped storage

All of these options have disadvantages, though. It may be that we need to take a step back in time for fresh answers.
An underused power-generating technology, implemented haphazardly in the 1960's, called pumped storage, is attracting interest from energy pundits. It can now be used with solar. Data centers should take note.

The problem

Solar systems obviously only create power during the daytime, but power use also occurs at night.
So a solar system needs some kind of storage mechanism for the daytime-created power. Batteries are commonly used in current systems.
However, batteries aren't very efficient, and they're heavy to transport, expensive to make, are not particularly tree-hugger-friendly. They also expend over time and consume building-space, among other problems.
Some say we need an alternative to batteries for solar.

Two lakes

An aging power plant in New Jersey might hold the answer. Prior to the days of solar, back in 1965, the innovative Yards Creek Pumped Storage Electric Generating Station opened in Blairstown, New Jersey.
The idea behind its revolutionary technology was simple. Two lakes are separated by a vertical distance. When power is cheap during the day, the water from the lower lake is pumped uphill to the top reservoir. At night, when power is expensive and is in more demand from the community, water is flowed downhill, through electricity-creating turbines to make cheap power.
This nighttime "harvesting," as Stephanie Matteson called it in an EnergyCollective article about solar storage issues and pumped storage, lets power plants be more evenly loaded.
Even though it uses more power to pump the water uphill than the power it gains by the turbines, time-of-day manipulation of energy rates creates savings.
And although it wasn't a very important issue at the time, using the same water each day helps with eco-concerns.

Solar storage

Fast forward a few generations and the idea conceivably could be perfect for solar, too. Solar systems, just like the western New Jersey grid, and other conurbations' power systems, need more even loading.

Why solar for data centers

Solar, overall, is a good energy solution for data centers for a few reasons.
Cost is stable, whereas fossil fuel costs are variable and unknown; solar is self-contained, and self-managed, so it is not susceptible to spikes and brownouts; it provides secured capacity; and as an added benefit, it's a not-inconsiderable public relations tool.
Both Apple and Google find it hard to stop plugging their renewable energy sources, for example. Apple says its data centers are 100% powered by renewable energy.

Solar storage

Germany is now using solar to power pumped storage, says Matteson. Low-cost solar is used in the afternoon to prime upper reservoirs.
Already, the pumped storage power plants operating in Germany have a combined output of about 7 gigawatts. For comparison, total nuclear power output in the U.S. is 98 gigawatts.
Add the likelihood that you'll be able to picnic, hike, view wildlife, and maybe swim with your future digital energy consumption should this take off, if nothing else, just think of the rhetoric Apple, Google, et al will be able to bombast.