How to recognise a green data center?

Keeping our digital society running is energy-intensive. Very much so. Data centers – the physical location of the internet – account for approximately three percent of the global annual energy consumption. This is more or less at the same level as the energy consumption of the aviation sector. By 2030, the consumption is expected to rise over ten percent. Therefore, the importance of using green energy in data centers and doing this as efficiently as possible is clear.

Greenergy Data Center in summer. Photo by: Tõnu Tunnel.

Even though the sustainability of data centers has become an important issue in the last few years and progress has also been made, the planning, development, and operating of completely green data centers still remains a huge challenge. The transition to carbon-free data management calls for changes in the planning and construction of the infrastructure.

How to measure the energy efficiency of a data center?

Data centers and server rooms must comply with high energy efficiency standards related to the PUE, or the power usage effectiveness coefficient. The lower the PUE, the better. New data centers in Europe which have committed to the Climate Neutral Data Centre Pact are required to achieve a certain PUE target by 2025, which is 1.3 in the case of a cool climate.

What does this mean? If the PUE is less than 1.3, each kWh used directly for the functioning of the IT equipment is accompanied by less than 30% of 1 kWh for cooling the equipment, communication, security, and for ensuring reliability. In 2021, the respective global figure was 57%, on average.

In a warm climate, a target of 1.4 has been set – cooling is inevitably more energy-intensive in warm conditions compared to cold ones. The same targets apply to existing data centers, but for 2030.

The data center of Greenergy Data Centers (GDC) in Hüüru in the vicinity of Tallinn, opened this winter, has set a target PUE of 1.2 or less. This means electricity consumption which is by a quarter lower of that in an average data center. GDC aims to use electricity as efficiently as possible.

Ideally, every organisation should be aware of its ecological footprint. It is not important if the servers of the organisation are located in an office, in a cloud, or in a data center. This footprint is probably the easiest to calculate in a data center.

Data centers are thirstier than you would think

Several factors play a part in the environmental footprint of a data center. Energy consumption has an important role, but it is not the only one. Data centers also consume water and the amounts required probably exceed what we would expect. For example, in the financial year of 2018, Google used 15.79 billion litres of water and Microsoft 3.5 billion litres, the majority of which was consumed by data centers.

It is hardly a surprise that access to water is a serious issue in the context of climate change, especially in the so-called third-world countries. Global water consumption has increased six times in the past one hundred years and is growing by 1% every year. It would therefore be good if the water consumption could be cut down. There is a separate coefficient used to express the effectiveness of water consumption – WUE (Water Usage Effectiveness).

What is all this water used for?

The problem is that the majority of data centers use water for cooling, which means constant water consumption (as well as energy consumption, as the water must first be cooled). Cooling water is sprayed in the air or vaporised to carry the heat efficiently away from the servers. In the latter case, the water must be heated for it to vaporise, which also requires electricity. The research-based website The Conversation writes that a relatively small 1 MW data center uses 26 million litres of water per year, on average, for cooling. The hotter the climate in which the data center is located, the more cooling is required.

The GDC data center in Estonia leads the way with a different solution – no water is consumed for cooling, as the building is equipped with free air cooling. This means that the WUE of the GDC data center is already almost zero (many other places work very hard to lower this figure).

We also have our cold climate to thank for this, as the Estonian climate is exactly right for the data center. Data centers may not be in too hot or cold conditions – an optimum range is needed, with no cooling or heating required year-round. In Estonia, the free air cooling only needs additional support for a few hundred hours over an entire year, on average. The cooling systems of the GDC data center and their contribution to ensuring reliability have been discussed in the blog before.

Reuse of thermal energy

The work of the IT devices in the data center turns electricity into heat. This heat can be reused. In practice, this means leading the residual heat to a nearby heating plant, for example, which distributes it to households. This saves a lot of the energy usually needed to increase the temperature in residential premises. For example, the Facebook data center in Odense, the third largest city in Denmark, should be enough to heat 6,900 local households for an entire year.

The GDC data center in Estonia has a similar capability and the thermal energy consumed there can be reused once a sufficient capacity is achieved.

Electricity must come from renewable energy sources

It has become a standard today that data centers run (or at least should run) on certified green energy. Pursuant to the aforementioned Climate Neutral Data Centre Pact, the energy consumption of data centers must be covered by renewable or hourly carbon-free energy in the extent of 75% by the end of 2025. By the end of 2030, this percentage should be 100%. GDC, the largest data center in the Baltic States, is already only using certified green energy.

Conclusively, data centers have an increasing role in achieving ambitious global climate targets. The more energy is needed for supporting our digital lifestyle, the bigger the economic footprint of data centers. The choice of the customers is also significant here – the more energy-efficient data centers are preferred, the more such centers are built.