Earlier this year I wrote in the blog entry “Yet another data center performance energy metric” about the initiative of the Japan’s Green IT Promotion Council (JGIPC) to improve on PUE with its own metric: the data center performance per energy (DPPE). One of the important things the JGIPC energy metric takes into account in comparison with the PUE metric is that they look at the quality of energy or in other words how much green energy is used. A good data center energy metric should not handle energy efficiency only, a good metric must also address the quality of the energy that is being used.
Last week, on the Power and Cooling conference in London, Eirikur Hrafnsson CEO of greenqloud held a provocative presentation on this matter. According to him many times the PUE metric is misused for green marketing or “green washing”. He came up with an alternative definition of the PUE metric to better see which data centers are truly green in the sense that they indirectly cause the least amount of CO2 to be emitted by their use of dirty or clean energy.
The definition for the GPUE is as follow:
GPUE = G x PUE
G is the Green factor and it is a simple calculated value:
G = Weighed Sum of energy sources and their life cycle Kg CO2/KWh
G =∑( %EnergySource x ( 1 + weight) )
PUE= 1.20 and the energy sources used are 50% Coal and 50% Hydro.
G = 0.5*(1+1.050) + 0.5*(1+0.013)
G = 1.531, GPUE = 1.84
Kg CO2 per usable KWh = (G-1) x PUE = 0.64 Kg
The weights are taken from the 2008 Sovacool Study.
The GPUE metric is a simple and pragmatic enhancement of the current PUE metric and service its goal to get rid of the distort green view you get from the current PUE.
Take a look at the greenqloud blog.