Can the earth’s heat power a data center? Part 2 of 2: Geothermal Energy
Part 1 in this series looked at Iceland’s geothermal power plants that have been making headlines in the data center industry lately. Although the electrical power generated is considerable, the country’s five plants that generate around 700 MW of electricity would be able to supply Apple’s data centers, corporate offices and retail stores and only have enough energy left for a US city with a population of around 100,000. Clearly there is not enough power. And in fact, most of the output of Iceland’s geothermal fields are used for heating, a much more efficient use of the resource.
To add to the capacity shortfall problem, there is concern in Iceland that extraction of geothermal energy does not provide an unlimited supply of power. A New York Times interview with Iceland’s Environmental Minister showed concerns about excessive tapping of geothermal energy (steam) can lead to temporary depletion of the geothermal field, meaning water is extracted faster than it can be naturally replaced. The minister noted complaints about smell as well as health concerns from the release of Hydrogen Sulfide (H2S) gas by Iceland’s residents in the southwestern part of the country where geothermal plants have been sited. (Link to Source) The issue of Hydrogen Sulfide issue was headlined in a study presented at Thirty-Sixth Workshop on Geothermal Reservoir Engineering held at Stanford University in 2011. The study conducted by Reykjavík Energy and Institute of Earth Sciences, University of Iceland begins, “The toxicity and foul smell of hydrogen sulfide creates one of the main environmental problems associated with geothermal utilization.” (Link to Source) This and subsequent studies look at reinjection of the H2S into the ground as one possible solution. (Link to Source)
So clearly there are technical and capacity challenges even in an area with abundant, often described as “unlimited” geothermal energy. And although while air and groundwater pollution is a concern just as it is with “fracking” for natural gas, capacity is the issue that defines the limits of data centers wholly powered by geothermal energy. Let’s move back to the example of our home heating system. In order to heat a home with today’s modern geothermal systems the field of heat extraction tubing is generally extensive, hundreds of feet. And while the heating or cooling needs of a single family home will not deplete the heat below the surface substantially enough to cause problems, the field needed for a closed loop heat exchanger that would be able to generate electricity would be massive, many times the footprint of the data center’s site.
Is there hope for geothermal power in data centers? The answer is a qualified yes. Iceland is not the only location with accessible geothermal resources: think Old Faithful in Yellowstone National Park. Of course we would not want to jeopardize the natural beauty of Yellowstone, but there are certainly many other locations where power plants like those in Iceland can be found.
Two residential closed loop geothermal field installation for a large home in Idaho (Left & Center, Link to Source) and modest Minnesota home (Right, Link to Source)
The U.S. has over 3,000 MW of geothermal electrical generation capacity not to mention hearing and other applications. California accounts for most of the installed electrical generation capacity with over 2,500 MW of capacity, followed by Nevada with 440 MW. (Link to Source) Wikipedia lists 66 geothermal fueled power stations over 50 MW operating or planned worldwide led by the US. Mexico, New Zealand and the Philippines are among the top five countries listed generating a total of over 7,500 MW of electrical power. (Link to Source)
Three New Zealand power plants demonstrate the capacity of geothermal energy with only one capable of powering a 100 MW data center. Output of the bottom two plants varies with time due to local depletion of heat and water. Reinjection and the addition of new wells can help overcome but may not eliminate this limitation. (Link to Source)
When we compare this to the 2012 global data center electrical power usage of 38 GW, current capacity is less than 20% of the demand. Still, that’s an impressive amount. The challenge can be seen in the other fact: global data center power usage rose by 14 GB between 2011 and 2012 due to the increasing use of the internet for everything, particularly the exponential rise of smartphones. (Link to Source).
New Zealand’s Wairakei geothermal power station (Left) and steam field collection piping (Right_ demonstrates the scope of the investment in land and equipment needed to generate 150 MW of electricity, enough to power 1.5 large, 100 MW data centers. This plant is being phased out and replaced by the Te Mihi power station which uses energy from the steam fields of the Wairakei power plant. Eleven smaller Wairakei generators will be replaced by two 83 MW steam turbines in the new $623 million Te Mihi plant. (Link to Source)
It is unlikely that geothermal electrical generating plants expanded as quickly, therefore even if all geothermally generated electrical energy was diverted to data centers, there is a long way to go. So what is the role of geothermal in supplying data center power? It’s part of the mix. While challenges exist such as source depletion, air and water pollution, technical solutions also exist. Locating data centers near geothermal plants can save transmission costs and losses, and with many sites in California, a state with a significant number of large data centers, this is happening naturally.
Top five geothermal countries show USA leading. and Iceland not on the list. ( Link to Source) US areas with the greatest potential for geothermal power are identified in an Arizona study show the greatest potential in the western third of the country. (Link to Source)
In the mean time, if the reader is considering replacing their home heating system, geothermal may make sense. Tax credits exist in some locations, and the ability to turn one unit of energy into six or seven can help pay for the system quickly. You’ll need an area where the collection field can be installed, but given the size of U.S. home lots that should not be an issue for many.