Can the earth’s heat power a data center? Part 1 of a 2: Geothermal Energy.
I’m old enough to remember the Arab Oil Embargoes of 1973 (the first time every U.S. citizen heard of OPEC) and 1979. In the first incident oil rose from $3 to $12 per barrel, virtually free by today’s standards but over $50 per barrel in 2008 dollars according to Wikipedia. (Link to Source) In the 1979 event oil increased to almost $40 per barrel, almost $100 in 2008 dollars. I won’t go into the politics behind the actions but the impact on the U.S. economy is well documented.
Photos from 1973 and 1979 Oil Embargo Crisis: Left: Gas lines (Link to Source), Right (Link to Source) U.S. interstate highway system speed limit lowered to 55 mph to save fuel.
What I recall is not only waiting in gasoline station lines and a quadrupling of home heating oil prices prompting making my home better insulated, but reading about an individual in Canada who heated his house with the heat below the ground. The documentary describing the heating system described the installation of a commercial grade refrigeration compressor and running copper tubing around the yard at a depth of about five feet. At this depth, from my increasingly faulty memory, the average year round temperature was 55ᐤF. While this is too cool for home heating, passing freon through the pipe and extracting the heat in the compressor resulted in a seven-fold energy gain. This means for every unit of electrical energy going into the compressor, seven times as much heat equivalent energy was received. And because the system was a closed loop, the freon could be continually recirculated without concern that the ground heat would be exhausted. Today’s modern Geothermal systems are based on this concept.
Can heat from the earth power a data center’s HVAC system? The short answer is yes. It’s being done today, but not in the way described above. For data center power requirements Iceland’s efforts are probably the best examples of using geothermal energy to power a data center. Because the heat from the earth is very close to the surface in Iceland, a country with numerous active volcanoes and hot springs, the ability to extract a large amount of heat energy relatively cheaply is possible. That heat energy in the form of steam is piped to a steam turbine and used to power an electrical generator. Iceland’s five commercial geothermal power plants each produce from 60 MW to over 300 MW of electrical power.
Iceland’s modern, commercial geothermal power plants produce over 50% of the nation’s overall energy supply including 90% of home heating demand and 25% in the form of electricity. (Link to Source) Left: 60 MW Krafla power plant (Link to Source), Right 150 MW Reykjanes power plant (Link to Source).
How does this stack up against data center power requirements? A quick search of recent data center announcements shows from 10 MW to 100 MW data center designs being built, the largest ones by companies such as Facebook, Google and Apple. To put this in perspective, 100 MW is about 20% of a large coal fired 500 MW power plant’s output, and is the equivalent of the power usage of 80,000 U.S. homes. (Link to Source). The average output of Iceland’s five geothermal power plants is a little more than 140 MW, the total output a little over 700 MW. One can easily understand that even in a country with very accessible geothermal resources there is not enough power to run the world’s data centers.
Apple Facilities, Environmental Footprint Report, Fiscal 2012 shows data center energy growth to over 200 M kWh, largely due to new data centers coming online. (Link to Source)
A publication titled Apple Facilities, Environmental Footprint Report, Fiscal 2012 shows a graph describing the company’s total electricity usage for its three data centers as 217 M kWh. Combined with the company’s corporate offices and retail stores the total corporate usage is 608 M kWh, meaning Iceland’s total geothermal generated electricity would service only Apple and a city with 80,000 homes. Clearly this is not sufficient to operate the world’s data centers.
The final piece in this two-part piece will look at the rest of the world to provide a complete look at the question of whether or not geothermal powered data centers are possible.