Data center CO2 emissions

There have been some debate about the source of electricity a data center is using and the CO2 emissions it is causing.

Recently some interesting figures came available by the International Energy Agency. These are the CO2 emissions per kWh electricity generation. Published in the 2013 edition of “CO2 emissions from fuel combustion – Highlights”.

It isn’t easy to find consistent and complete time series. A lot of the data that can be found is using different definitions and/or different time periods what makes it difficult to aggregate these figures. IEA has published time series for the period 1990 – 2011.

To make some comparisons a selection from different parts of the world is showed in table 1. Remarkable differences in CO2 emissions can be found. Some countries show a huge decrease of CO2/kwH emission during the period 1990 – 2011 whereas others show an increase. Also within a region the differences are considerable. Zooming in on the E.U. countries with Tier 1 data center markets; United Kingdom, France, Germany and The Netherlands, (with the DC hubs London, Paris, Frankfurt and Amsterdam) we see a CO2/kwH reduction of 34.4%, 41.9%, 21.4% and 33.4%. Differences in emissions and emissions trends are caused by different energy policies and different compositions of the power plant fleet.

Table 1. CO2 emission per kWh from electricity generation, source IEA.

  2011kg CO2 /kwH Difference 1990 -2011

%

E.U. 0.352 -21.4
United Kingdom 0.441 -34.4
France 0.061 -41.9
Germany 0.477 -21.4
The Netherlands 0.404 -33.4
Russian Federation 0.437 7.6
U.S.A. 0.503 -13.6
Canada 0.167 -14.8
Australia 0.823 0.7
Singapore 0.500 -44.9
Japan 0.497 14.3
Korea 0.545 4.8
India 0.856 5.4
China 0.764 -14.5

 

The figures that are showed are averages. The CO2 emission of a data center depends on the power plants that are really used to deliver electricity to the data center. Depending on the electricity demand the power supplier will assign different power plants. The assignment of power plants is according to their production efficiencies (short-run marginal costs of production) and capacity and this production mix will influence the CO2 emission per kwH.

CO2 emission per server

To get an impression of the CO2 emission per server in different parts of the world we making use of the report ”Estimating total power consumption by servers in the U.S. and the world” of J.G. Koomey of Stanford University, the power usage of low, mid and high range server are estimated on 180, 420, and 4800 Watt. This will lead to the figures in table 2 based on a 24 hours x 365 days usage.

Table 2. Yearly CO2 emission per server.

Kg CO2/year Low range server Medium range server High range server
E.U. 555 1295 14801
United Kingdom 695 1623 18543
France 96 224 2565
Germany 752 1755 20057
The Netherlands 637 1486 16987
Russian Federation 689 1608 18375
U.S.A. 793 1851 21150
Canada 263 614 7022
Australia 1298 3028 34606
Singapore 788 1840 21024
Japan 784 1829 20898
Korea 859 2005 22916
India 1350 3149 35993
China 1205 2811 32125

 

Data center use case

What do all these figures mean for a data center? Lets take for example a data center of 1000 servers with a PUE of 1.8. In this case we use a server mix of 95% low range, 4% mid range and 1% high range servers. Besides servers the data center will also use storage and network components. The ratio of the energy use of servers versus the energy use of storage and network components is set to 75:15:10.

We can define a worst-case scenario when electricity is created with conventional coal combustion; in that case 1kW of electricity is equivalent to 1 kg CO2 emission. For the data center in this use case, that would be an upper limit of 4957 ton CO2 per year. In reality power suppliers are using a mix of different energy sources. As we can see in table 3, the lowest emission is 302 ton and the highest emission is 4244 ton. A difference with a factor 14!

Table 3. CO2 emission of a data center.

Metric ton CO2/year Servers Storage Network Data center
E.U. 727 145 97 1745
United Kingdom 911 182 121 2186
France 126 25 17 302
Germany 985 197 131 2365
The Netherlands 835 167 111 2003
Russian Federation 903 181 120 2166
U.S.A. 1039 208 139 2494
Canada 345 69 46 828
Australia 1700 340 227 4080
Singapore 1033 207 138 2479
Japan 1027 205 137 2464
Korea 1126 225 150 2702
India 1768 354 236 4244
China 1578 316 210 3787

 

Zero emission

There is of course the alternative case of zero CO2 emissions if the electricity supply is completely based on nuclear, hydro or renewable energy. Some countries like Iceland, Norway, Sweden and Switzerland have extreme low CO2/kwH emission (1, 13, 17 and 30 gram).

 

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