Sustainable cloud computing

How can data centers use 100% renewable electricity?

If we still generate energy from non-renewable sources, how can a data center be 100% renewable?

Oboke, Japan

Data centers have a range of components which make up their energy footprint, but electricity is the primary energy input in daily operations. All the equipment — servers, storage, networking — is powered by electricity, which means the environmentally impact of a data center is largely dependent on where that electricity comes from.

A large proportion of data center usage today is through the cloud. It is estimated that 53% of all servers will be located in hyperscale cloud data centers by 2021. This basically means AWS, Google Cloud or Microsoft Azure.

Global data center energy end use (IEA, 2020).

Whilst non-renewables continue to make up a large part of the source of that electricity, a transition is in progress to clean up the grid.

The UK has been rapidly decarbonising but global progress varies widely.

Renewables share of power generation by region (BP, 2019).

Most data centers plug directly into the local electricity grid and in most countries, non-renewables still make up a significant part of the electricity mix. This is relevant to data center electricity usage because it is not possible to guarantee 100% renewables if their electricity is sourced from the grid. When renewables are not generating, electricity must be sourced from other means and utilities have to make up their commitments through offsets or purchases of renewables elsewhere.

Cloud data center renewable electricity today

Google and Microsoft are are both carbon neutral companies. This is different from “net zero”, which Microsoft explains well on their blog:

Given common usage, companies have typically said they’re “carbon neutral” if they offset their emissions with payments either to avoid a reduction in emissions or remove carbon from the atmosphere. But these are two very different things. For example, one way to avoid a reduction in emissions is to pay someone not to cut down the trees on the land they own. This is a good thing, but in effect it pays someone not to do something that would have a negative impact. It doesn’t lead to planting more trees that would have a positive impact by removing carbon.

In contrast, “net zero” means that a company actually removes as much carbon as it emits. The reason the phrase is “net zero” and not just “zero” is because there are still carbon emissions, but these are equal to carbon removal. And “carbon negative” means that a company is removing more carbon than it emits each year.

- Microsoft Blog, 2020.

When a data center is connected to a grid with a varying mix, operators currently have two options:

  1. Purchase offsets by making payments to projects to match your total emissions.
  2. Contract energy from renewables sources to match your total energy consumption, even if those sources are elsewhere on the grid (or even in different countries).

The first of these options is what Google has been doing since 2007 and Microsoft since 2012. This makes them carbon neutral.

The next step is to match like-for-like rather than matching emissions for emissions e.g. buy renewable energy to match all your energy usage. Google has been doing this since 2017 and Microsoft has pledged to do this by 2025. Microsoft is actually already doing this for electricity, but not for energy ( In FY2018 391,047 MWh still came from other fuels such as jet fuel, natural gas, diesel, etc).

Amazon is more difficult to assess because they provide only limited environmental reporting. 5 of their 22 cloud regions are carbon neutral. They have a goal to be completely carbon neutral as a business by 2040, claim to use more than 50% of renewables as of 2018, and are aiming to be 100% renewables by 2030.

Overall, this second option has resulted in the tech industry being the largest corporate purchaser of renewable energy.

Top corporate renewables off-takers (IEA, 2019).

A third option — 24/7 local renewables

The problem with contracting energy is it is sort of cheating. Whilst renewable energy is being generated somewhere, that may not be where your data center is. The third option is to fix this — deploy renewable sources of energy on the local grid providing power 24/7, so the data center will actually consume renewables at all times.

This is much more difficult because of the varying location of data centers. Some facilities are located in regions with abundant wind, solar and/or hydro. Others are not.

Google started work achieve 24/7 renewables in 2018. It is approaching this through construction of its own, or contracting with 3rd parties for, renewable sources of energy that go directly into the local grid. Google published a paper about their approach which includes some interesting visualisations of the concept.

For example, compare a theoretical 24/7 100% renewables data center:

Every hour of electricity use at a 24×7 carbon-free data center (Google, 2018).

With an actual data centre in Finland which is able to source 97% renewables:

Every hour of electricity use at Finland data center (Google, 2018).

And an actual data center in The Netherlands with 69% renewables, and a solar source of energy added part-way through the year.

Every hour of electricity use at Netherlands data center (Google, 2018).

The goal of 24/7 100% renewables is informing how Google procures energy. Having contracted for 350MW of solar energy at a new data center being constructed in Las Vegas, Google has also bought 250–280MW of storage. This means Google can store renewably generated energy that is available on-demand when renewables are not available locally.

How can data centers use 100% renewable electricity?

As a result of these various activities, the answer to this question has progressed over time.

The first step has been to offset. This is followed by matching usage with like-for-like energy purchases somewhere. The final stage is direct consumption of locally generated renewables, either in real time or stored from recent generation.

So the next time you see a tech company announcing a huge renewables project, you should look to see exactly what that mean and where that energy will really go. New renewables are good, but whether that energy is actually powering the company operations directly is another question.

For more on this, this episode of the The Interchange podcast discusses the details.

Originally published at on February 6, 2020.

Co-founder — the best tools for developers. Researching sustainable computing at Uptime Institute.

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store