Coal fired clouds

So, is cloud is really green and should you move all your IT into the cloud because it is much more efficient than running it yourself? If I am procuring IT services and one of my objectives is to manage the environmental impact of our IT then what can I do? I can’t use the CRC, I can’t use PUE and I definitely can’t rely on supplier marketing.

What we need is to replace “my PUE is wonderful” with some alternative measure of the carbon cost of the delivered service which is actually useful to the customer. Here I will propose the carbon intensity of the power delivered to the IT equipment as an interim measure.

What’s wrong with just using PUE?

Actually we might be better off asking “what’s right with using PUE?”. PUE is a reporting metric, it gives you a specific measure of the performance of the mechanical and electrical plant in a data centre over the measured time period. It does not tell you how the data centre will perform in the future or how efficiently the IT equipment used the IT electrical power delivered.

Importantly, selecting based on PUE assumes that all IT electrical load is good and that all IT equipment is operated at the same efficiency which is not true.

My low PUE data centre is coal fired

A provider may have built a very efficient data centre but if they have built it in an area with high grid carbon intensity we have to think again.

Carbon intensity is a measure used to express the amount of CO2 released at the generating plant to deliver each unit of electricity at the data centre. In the UK this is published by DEFRA and is currently 0.53 kg CO2 per kWh. (http://efficient-products.defra.gov.uk/spm/download/document/id/785)

So, if I have a data centre with a PUE of, say 1.5 in an area with a relatively normal mix of energy supply such as the UK I may have a carbon intensity of 0.5kg of CO2 for every kWh of supplied electricity. Taking this through my PUE that would become 0.75kg CO2 for every kWh delivered to the IT equipment.

To understand how this stacks up we can compare this fairly decent data centre with a very efficient data centre in a coal fired state and an inefficient data centre in a state which has a high proportion of renewables such as hydro electric or Nuclear (in France).

So, clearly if I am seeking the lowest carbon I should be buying service from the data centre with the worst PUE as it has the best overall carbon per kWh delivered to the IT equipment.

Note that the EPA are considering part of this in the Energy Star for data centers programme in the US through the use of their source energy use methodology (http://www.energystar.gov/ia/business/evaluate_performance/site_source.pdf ) but that this does not distinguish the mix of power on the local grid.

Greenpeace

Greenpeace recently released a call to “make clouds green” which identified some of these issues in sourcing of energy for cloud computing and called on cloud operators to purchase renewable energy. http://www.greenpeace.org/raw/content/international/press/reports/make-it-green-cloud-computing.pdf The argument being that not only would it make cloud resources greener but also as industrial scale consumers of electricity the cloud providers would actually create sufficient demand to increase investment in renewable generation. Facebook were the identified villain of the piece with their coal powered data centre in Oregon

Report the IT power carbon intensity

What the Greenpeace paper stopped short of was suggesting that we combine PUE with the carbon intensity of the energy sourced for our data centres to provide a more useful environmental measure than PUE. Whilst carbon is not the only factor in most users selection of data centres or services if we are to consider it then we need some comparable and meaningful measure, PUE is clearly not able to provide this.

Smart grids and demand management

If we have a well instrumented data centre which is able to track our energy use and efficiency in real time we have a number of options. We can connect to data sources such as Realtime carbon, http://realtimecarbon.org/ and report our delivered IT carbon intensity through the day based on both our PUE and the carbon intensity of our supply.

This would allow customers to make more informed assessments of providers’ environmental credentials at the time of selection but as cloud advances customers may choose to run jobs when “greener” power is available. As the cost of energy rises and more active demand management measures are put into place we may even see the commodity cloud market move towards dynamic pricing of energy and thus data centre output.