It is estimated that the data storage sector consumed about 61 billion kilowatt-hours (kWh) in 2006 (1.5% of total U.S. consumption, or roughly equivalent to the amount consumed by 5.8 million average U.S. households). These numbers are only expected to grow.

The energy used by the nation’s servers and data centers is growing at an unsustainable rate. Not only that, but web servers are notoriously inefficient. For example, computer servers are used at only 6 percent of their capacity on average, while data center facilities operate at roughly 65% to 75% efficiency, meaning that 25% to 35% of all the energy consumed by servers is wasted (converted to heat).

If we are to even consider reducing our energy consumption and carbon footprint, the growing demands generated by our web servers must be near the top of the list of possible improvements. And the Department of Energy agrees.

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AC-DC?

For electricity flowing all the way from power plants to the wall socket, alternating current is far superior. But for the short transmissions inside those computers DC power prevails. The search for ways to convert AC to DC more efficiently is leading some data center companies to consider a DC-centric approach.

It’s easier to transmit AC over long distances; DC requires thick copper cables or bars, instead of comparatively lightweight wires. But DC becomes a more serious possibility for power once AC reaches a building.

Converting from one form of power to another in a computing environment may not be performed efficiently, especially at the server level, and even then, the resulting waste heat may be deposited in the rack or computer room at a point that requires further effort to dispose of it with the air handlers. Unfortunately, there is disagreement in the community over how to address these inefficiencies.

• DC advocates argue that plugging servers into AC power is inefficient, and switching systems to DC would cut down on waste heat and component failure.
• Proponents argue that using DC outside the server removes some of the inefficiencies of power supplies that convert AC electricity to DC. Servers without such power supplies don’t have to contend with as much waste heat and attendant component failure.

But according to NPPL, substituting DC power in data centers as a replacement for conventional AC power has not yet made significant inroads into many data centers because the technology is unfamiliar to many facility engineers.

Despite the wide-spread use of DC power in telecommunications, there is reluctance within the computer industry to switch to new technologies without field experience showing that the switch could be done safely and would have operational and economic benefits without causing unanticipated problems.

If DC would in fact be a more efficient type of power within servers themselves, might it be possible to site server farms to take advantage of the DC provided by integrated renewable energy generating systems such as solar PV and wind?

Photos:1.© Eimantas Buzas | Dreamstime.com; 2. Versageek via Flickr under a Creative Commons License

Impact Lab
NREL
PNNL

The efficiency development model helps servers that used to be assigned to only one task to now multitask and move between tasks as needed. In other words, the servers can now meet the fluctuating demand that the internet has more quickly. This model reduces the chance that a website gets overwhelmed with demand and locks up. It is also said to increase efficiency and service by 20 percent.

Georgia Tech professor Craig Tovey was struck with a curiosity of honeybee behavior in the early 80s. He realized through conversations with a colleague from the University of Oxford that “bees and servers had strikingly similar barriers to efficiency.” Bees have very inconsistent resources. Sometimes there is an abundance of nectar to collect and sometimes there is very little. Year after year the supply is different and the location of the nectar oasis’s change. Yet somehow, they always seem to maintain a fairly consistent supply of nectar in the hive. Tovey saw this as a stimulating intricacy in the natural environment that yielded very effective results. Tovey among other colleagues conducted research for decades on how they work and how to use their brilliance in our built environment.

The greatest breakthrough was the discovery of the waggle dance. Australian zoologist Karl con Frisch won a Nobel Prize for this. When bees that hit an oasis return to the hive, they do a dance at the hive floor, wagging their tail back and forth. Each movement of the dance indicates location, scent, sound and gives other foragers clues about where the oasis of nectar is.

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