Is wind energy just blowing in the face of datacentre cooling reality?

Using renewable energy such as wind energy for datacentre cooling may not address issues of carbon emissions as directly as suppliers claim

Google recently announced that it has signed an agreement to power its Oklahoma datacentre with 48MW of energy from a wind-farm that will be implemented later in 2012, bringing the company to a total renewable energy contracted level of 260MW, writes Clive Longbottom.

Great – at last, a major energy-guzzler is taking sustainability seriously and looking to renewable sources to power its datacentres.

But will using wind energy in datacentres really help address issues of carbon emissions?

It is pretty difficult to identify where a unit of power has come from. If a power socket or distribution system is plugged into a local or national grid system, the actual energy provided is from a pool of all generated power – and no differentiation can be made between energy that comes from renewables, gas, coal or nuclear. The only way to do this is to single-feed energy directly from the source.

The stated source for the wind power for Google is the Canadian Hills Wind Project. Its building started in May 2012 with a rated end capacity estimated at 300MW. But, rated capacity and real output is not the same.

The real output of a wind turbine is around 30% of its rated capacity, leaving the project with only about 100MW of output.

Why only 30%? The rated level assumes constant output with optimum wind speeds. This does not happen, anywhere – even in the windiest places. Imagine when there is a meteorological “high” over the region. With a high, winds are mild to non-existent, and energy will have to come in from elsewhere on the grid. Even if the wind blows enough to turn the turbines, with low wind speeds, datacentre energy efficiency is hit; optimum efficiency is only reached with wind speeds of around 34mph – the energy gap will have to be filled from elsewhere. 

At the other end of the scale, let us assume that there is a gale blowing. With winds above around 50mph, wind turbines have to be “parked” to prevent physical or electrical damage. While no energy is being generated from the wind turbines, then the needed energy has to come from elsewhere. The contracted energy is just being pulled from that pool of all types of power generation – it is not being provided specifically through wind power.

Google and datacentre power

The wind turbine Google is planning to use was to be used to power around 100,000 homes in the local area – this will now have to be done with just 52MW of realistic output, or a little over one half a kW per house. The US Energy Information Administration (EIA) estimates that an average US house requires 11.496 MWh per year. But if just 52MW are allotted across 100,000 homes, it adds up to just 4.56MWh per home over a full year – less than half of estimated requirement.

Just where is the rest of the energy for those homes going to come from? Is it just a case that Google has shifted the “dirty” power usage from itself to the nearby householders?

So, is renewable energy all just smoke and mirrors, or is there actually a case for using it?

If the idea is for your organisation just to use wind power, then only go for it as a marketing exercise. Datacentre managers can tick the box on the sustainability part of the corporate responsibility statement, and hope that no-one questions it too deeply. You can close your eyes and ears to reality and fall for the smooth talk of the energy vendor who says that you are signing up for a pure wind-based contract. 

Benefits of blending traditional power and renewable energy in datacentres

Any enterprise that is serious in its intention to use renewable energy must adopt a “blended” approach. 

Google uses hydro-power for its Dalles datacentre in Oregon and for the Mountain View datacentre, it has installed solar power. Google also owns two wind farms outright. Again, although solar power is not continuous, what Google is showing is a capability to blend its datacentre cooling approach – with the use of dams, hydroelectricity can be pretty much continuous, as the energy comes through water and gravity in a predictable manner. It is only in times of severe drought where hydro-power can run into problems. What Google cannot do is to use its solar output from very sunny days in California to power its Oklahoma datacentre in periods of low wind.

Google can be pretty choosy about who it signs contracts with and how these contracts are run. For an average organisation, this may not be the case.

Best practices for using renewable energy in datacentre cooling

Enterprises must ensure they pick an energy provider that can demonstrate that it has a blended energy generating capability. Mixing constant sources such as hydro or tidal with inconstant sources such as wind and solar means that there is a better chance of maximising the energy taken from sustainable sources and making datacentres more efficient and “green”.

IT executives must also read the small print carefully. Renewable energy bought under contract tends to be sold at a premium.

Investment in renewables is still expensive – and a lot of this is underwritten and underpinned by government initiatives. Make sure you understand what happens to that premium – is it for further investment in more renewables, or is a large chunk of it just for shareholder profits?

Will the supplier guarantee what proportion of energy supplied is generated from sustainable sources? For example, if the supplier has a total generating capability of 1,000MW, of which 500MW is wind, 100MW is solar and 400MW is hydro/tidal, the actual total is likely to be around 550MW or so of actual generated power capability when measured against rated capacity. This is an average capability – it may be capable of providing 600MW at some times, and as little as 350MW at others – the inconstancy of the power sources means predictability is difficult. If the totality of the supplier’s contracts comes to 1,000MW, it is short in real terms by 450MW – and each customer is only getting 55% of its energy from the supplier’s renewable sources. 

That then leaves the question of where is it bringing the extra power in from – other renewable suppliers (who will have the same problems) or from fossil fuel and nuclear sources?

Renewable energy is important and should be part of a datacentre’s power mix, but IT executives should not fall for the snake oil, smoke and mirrors and believe that everything signed up for will be from renewables. They must check the contract, make sure that the premium is reinvested in suitable new projects and that excess energy is sourced ethically and openly. 

Clive Longbottom is a Service Director at UK analyst Quocirca Ltd.

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