re: Ann: Innamincka Data Centre - Feasibility... From...

re: Ann: Innamincka Data Centre - Feasibility... From Wikipedia:

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Though the numbers are not publicly known, some people estimate that Google maintains over 450,000 servers, arranged in racks located in clusters in cities around the world, with major centers in Mountain View, California; Council Bluffs, Iowa; Herndon, Virginia; Lenoir, North Carolina; Atlanta, Georgia; Dublin, Ireland; Saint-Ghislain, Belgium; Zürich, Switzerland; Tokyo, Japan; Beijing, China; and new facilities constructed in The Dalles, Oregon. In 2009 Google is planning one of its first sites in the upper midwest to open in Council Bluffs, Iowa close to abundant wind power resources for fulfilling green energy objectives and proximity to fiber optic communications links.

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and

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Servers are commodity-class x86 PCs running customized versions of Linux. The goal is to purchase CPU generations that offer the best performance per dollar, not absolute performance. Estimates of the power required for over 450,000 servers range upwards of 20 megawatts, which cost on the order of US$2 million per month in electricity charges.
Specifications:
Upwards of 15,000 servers ranging from 533 MHz Intel Celeron to dual 1.4 GHz Intel Pentium III (as of 2003). A 2005 estimate by Paul Strassmann has 200,000 servers, while unspecified sources claimed this number to be upwards of 450,000 in 2006.
One or more 80GB hard disks per server (2003)
2–4 GB of memory per machine (2004)
The exact size and whereabouts of the data centers Google uses are unknown, and official figures remain intentionally vague. In a 2000 estimate, Google's server farm consisted of 6000 processors, 12,000 common IDE disks (2 per machine, and one processor per machine), at four sites: two in Silicon Valley, California and one in Virginia. Each site had an OC-48 (2488 Mbit/s) internet connection and an OC-12 (622 Mbit/s) connection to other Google sites. The connections are eventually routed down to 4 x 1 Gbit/s lines connecting up to 64 racks, each rack holding 80 machines and two ethernet switches. The servers run custom server software called Google Web Server.

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and from another site:

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So you now know one single Google search query consumes 2 to 8 watt-hours of energy. To put this on a scale, Google processes petabytes of information on a daily basis while indexing the web and doing other various things. If we average this out to 4.5 watt hours per query, and consider Google is easily handling 400 million queries a day based on comScore metrics, then we can see 1,800,000,000 (1.8 billion) watt-hours of energy being used daily just for basic search queries. The Google Complex itself uses the amount of power as 3,333 California homes.

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That seems a little larger than I expected but having worked primarily with very large mainframe systems in the past I do know that the power engineering of the machine rooms was a constant preoccupation going back 30 years or so - which means that the modern approach of racks and racks of servers is likely just as problematic.