Appendix
Carbon emissions model
This model was created to calculate the carbon emissions associated with public cloud, private cloud and traditional dedicated IT deployment scenarios. It captures emissions from the data center as well as the embedded server emissions and emissions from data transportation. The key assumptions included in the model are detailed below the schematic.
Number of servers
Emissions from data centers
Server energy used Data center PUE
Pn = (Pmax - Pidle)* n/100 + Pidle
Number of servers Emissions
Deployment scenario*
*Deployment scenarios are public cloud, private cloud and dedicated IT.
Size of firm
Different inputs are used around the number of servers required (related to extent of virtualization), server utilization rates and data center PUE according to the deployment scenario.
Key assumptions in the carbon emissions model Data center PUEs (Source: US EPA18
and interviews)
Public cloud Private cloud Dedicated IT
2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 1.5 1.8
1.45 1.75
2 1.95
1.4 1.7 1.9
Server utilization rates (Source: Study interviews) - Public cloud: 65% - Private cloud: 40% - Dedicated IT: 15%
Electricty price (Source: US Energy Information Administration19
- $0.099/kWh Metric tons of CO2 / kWh (Source: US EPA20
- 0.00069 tons of CO2 / kWh ) )
18.
http://www.energystar.gov/ia/partners/prod_development/ downloads/DataCenters_GreenGrid02042010.pdf
19.
http://www.eia.gov/cneaf/electricity/epm/table5_6_a.html 20.
http://www.epa.gov/cleanenergy/energy-resources/refs.html
1.37 1.66 1.85
1.34 1.62 1.79
1.31 1.58 1.75
1.29 1.55 1.72
1.27 1.53 1.69
1.26 1.51 1.67
1.25 1.5
1.65
Emissions from data transportation
Energy used per transaction
Embedded emissions from servers
Embedded energy of server
Pn is the power consumption at n percentage CPU utilization Pmax is the maximum power draw Pidle is the power draw at idle
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