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This is how we reduce data centers’ carbon footprint

Datacenter serverDo you think of crypto currencies and streaming services when you hear the word “data center”? You’re not alone. But they are so much more than that.

Yes, they are the home of your favorite Netflix show. But video-meetings, autonomous vehicles, smart cities, online banking services and health journals are just a few examples of products and services that require computational power, handled in data centers around the world.

Over the past decade the demand for computing power has increased exponentially, making data centers a fast-growing industry. They are a huge part of what allows us to live our modern, digitized lives. And they are important enablers for more efficient services and the transition to a green economy. For instance, reducing traveling by facilitating an increased use of e-meetings, and enabling smart technologies making our lives both greener and more comfortable.

Data center data traffic exponential development

But there is a flipside to the coin: data centers use immense amounts of energy.

They already use more than 2% of the world’s electricity, and contribute to 2% of world’s CO2 emissions. That’s equivalent to the world’s entire airline industry. This is in great contrast to the European Green Deal’s goal to make data centers climate neutral by 2030.

Data centers must reduce their climate footprint if we are to mitigate climate change. And many eyes look to Norway as a place that has both the infrastructure and natural resources to do that.

What is a data center?

A data center is essentially a dedicated space used to house computer systems for processing, distribution and storage of data. The typical data center consists of IT equipment like servers, networking equipment such as routers and switches, and storage systems.

This is typically organized in the form of severs racks, which are arranged in aisles as in the picture below. In addition, data centers houses cooling and ventilation systems, backup power supply, security, fire protection and monitoring.

 

How can data centers become more energy efficient than they are today?

Just as the device you are reading this article on, data centers need electricity to work. They just need A LOT more of it. And just as your computer has a fan to prevent it from overheating, data centers need a cooling system.

From a climate footprint perspective, the need for energy and cooling are not problems in and of themselves. The problem is most data centers’ cooling systems are inefficient, using unnecessary amounts of energy. And the heat removed by the cooling system can be a valuable resource, but is rarely used for anything.

On top of that, most data centers use non-renewable electricity sources meaning there is a good chance your next video meeting is powered by coal, oil or gas. Even if you attend the meeting on a mobile device or computer powered by e.g. water, wind or solar energy.

But what if the video meeting was streamed from a server powered by water or wind electricity, had more energy efficient cooling and utilized its waste heat? Let’s take a closer look at how data centers can change from climate-foe to climate-friend, and why many think Norway might be the perfect place to build them.

Advantages and challenges with data centers in Norway

Norway’s geography and natural resources has led it to become a large producer of renewable energy. In fact, 98% of Norway’s electrical production is renewable, and it has one of the lowest electricity prices in Europe. In addition, the cool climate allows for both very efficient cooling and brings a large potential for waste heat utilization.

These advantages have not gone by unnoticed by the industry, attracting leading data center companies such as Microsoft and Facebook. This may facilitate a new Norwegian industry.

But a growth in the data centers industry in Norway will not come without challenges, and Norway would have to do more than just rely on its natural resources.

The need for more renewable energy production will increase: The Norwegian Water Resources and Energy Directorate estimates that the electricity consumption from data centers will grow from 0.8 TWh in 2019 to between 3 – 11 TWh in 2040.  More data centers will also cause challenges to the capacity in the electrical grid. Increased demand from various consumers such as new emerging land-based industries such as battery production, electrification of offshore oil and gas platforms and increased demand from households from e.g. electric car charging is causing the need to scale-up the electrical capacity. In this aspect, data centers represent a large share of the increased demand: between 2018 and 2019, about 50% of new requests to connect to the electrical grid came from data centers.

So why are data centers so energy intensive?

The simple answer is computational power and cooling.

The servers require large amounts of energy for computing. This energy is dissipated as heat within a relatively small area. And because the IT equipment is sensitive to high temperatures, the heat must be continuously removed.

As illustrated in figure above, the energy requirement for cooling typically accounts for a large share of the overall energy consumption in data centers.

The energy requirement for cooling depends on several factors, for example the cooling solution and where the data center is located. I.e., colder climates lead to reduced energy demand from cooling.

Power Usage Effectiveness (PUE)

A metric that is often used to describe the efficiency of data centers. It relates the total energy consumption of a data centers to the energy consumption of the IT equipment:
PUE=(total data center energy consumption)/(energy consumption of IT equipment)

 

The efficiency of data centers is often described by their PUE-values. Efficient data centers can achieve PUE values below 1.2. However, it is easier to achieve low values when the ambient temperature is lower, since little or no energy needs to be spent on mechanical refrigeration systems. This means that data centers located in Nordic countries have a natural advantage.

Still, a study showed that Nordic data centers achieve on average a PUE of 1.71, which indicates that there are still significant room to improve the energy efficiency. This can be done by choosing more efficient cooling technologies.

How the choice of cooling technology can reduce data centers’ climate footprint

Cooling technology plays an important role in the effort towards making data more energy efficient. Not only does an efficient cooling system reduce the energy consumption, but it can improve the potential for utilizing the waste heat by capturing it at even higher temperatures.

The choice of cooling technologies is usually driven by investment costs and the need for high heat flux from the servers.

Overview of different cooling systems for data centers

Air based cooling systems
In these systems, cool air is supplied to the server rooms. The server racks are often arranged in so called ‘cold’ and ‘hot’ aisles, to control the airflow and eliminate mixing of cold and hot air.

Due to low heat capacity and heat transfer coefficient, air is not a very good medium to transfer heat, which results in high energy consumption, limitations to how compact the servers can be placed and a relatively low waste heat temperature.

Liquid based cooling systems use a liquid such as water to dissipate heat. This can be done by circulating water in micro channels and exchanging heat in cold plate heat exchangers which are in direct contact with the server components.

Water and liquids in general have significantly better heat transfer properties compared to air. Liquid based cooling systems allows for more compact datacenters, reduced energy use for cooling and higher waste heat temperatures.

Two-phase cooling is an emerging form of data center cooling technology. Here, the liquid coolant evaporates in the cold plate heat exchanger and the dissipated energy is stored as latent heat. This allows for even greater heat fluxes, and coolant return temperature and makes systems with even higher computational densities possible.

 

Most data centers use conventional air-based cooling systems, which are simple and cheap. The downside is that is not an efficient way of removing heat and therefore results in a high energy consumption and low waste heat temperatures.

However, the market’s push towards building even more computationally intensive data centers has resulted in cooling methods which can remove more heat per area.

Examples of this are liquid based cooling systems which have already been commercialized, and two-phase cooling systems which is an emerging technology. These new cooling systems can deliver heat at 60-80°C. This is heat we can utilize directly for many purposes.

From an overall energy efficiency perspective, the choice of cooling technology should not just be based on cost and heat dissipation rates, but also on the potential for waste heat utilization.

Waste heat utilization – what are the possibilities?

No matter how energy efficient a data center is, inevitably almost all its electricity consumption turns into waste heat in the end. Today, this heat is usually not used for anything. But it can actually be a very valuable resource if it is harnessed and used properly.

The challenge is that the heat has low temperature levels, making it difficult to utilize. However, as we have seen, the choice of cooling technology will improve to potential to make use of it.

In general, there are two ways to utilize the waste heat: Direct use, or conversion to other energy forms or temperature levels, such as:

  • Increasing the temperature – for example with a heat pump
  • Produce cooling – for example with sorption cooling
  • Convert to electrical power – for example with an Organic Rankine cycle

As seen in the table below there are several potential applications that can benefit from data center waste heat. The choice of more efficient cooling technologies opens up for even more applications.

  Cooling technology and waste heat temperatures
  Air-cooled Water-cooled Two-phase cooled
Technology   15-45°C 60°C 75°C
HVAC/domestic hot water Yes Yes Yes
District heating Need heat pump Need heat pump Need heat pump
Boiler feedwater preheating No Yes Yes
Sorption refrigeration No Yes Yes
Organic Rankine Cycle No Yes Yes
Desalination No Yes Yes
Biomass processing Yes Yes Yes
Food production Yes Yes Yes

Urban areas

In urban areas there is a great potential to use waste heat from data centers for district heating, as heat pump technology can lift the waste heat to the required temperature level. This potential has gained traction in the industry and several initiatives and projects are now being realized for this purpose, such as the use of data center waste heat for district heating in Oslo. In this context SINTEF is working with how urban heat sources, such as data centers, can play the role of “urban heatplants” and provide heat to local energy grids. 

Other application areas are building heating and domestic hot water heating which can be achieved without the use of heat pumps.

Rural areas

In many situations it is advantageous for data centers to be located in rural areas due to the availability of space, electric power, and the potential to use the geography to achieve efficient cooling methods such as free cooling in mountains, or access to rivers or sea water. The downside of this is that the lack of potential urban heat recipients makes waste heat utilisation challenging.

Here, there is a need to create awareness among data center operators, industry and local authorities of the waste heat potential from data centers. The establishment of data centers in co-location together with relevant industry that can make use of the waste heat, can lead to considerable energy and emissions savings. Examples of potential waste heat utilisation for industrial purposes include biomass processing, greenhouse food production and land-based fish farms.

The role of data centers in the future

The growing industry of data centers will play ever greater part in the society in the future. And even with measures to improve their energy efficiency it is likely that their share of the global energy consumption will grow in the years to come.

A potential key role for data centers as large energy consumers today, is to become the energy hubs of tomorrow. As energy hubs data centers can produce, consume and store energy, and come to good use for example by load-balancing the electrical grid to cope with peak demand, and integrate electrical and thermal energy demands, and shift between these demands depending on seasonal changes. For example, in the winter a shift to heat can be made to accommodate increased demand for district heating, while during summer a higher fraction of electricity is delivered.

How can SINTEF contribute?

SINTEF Energy Research has great experience when it comes to improving energy efficiency and utilization of waste heat. In for instance the FME HighEFF research centre, SINTEF scientists are working on how to achieve optimal integration of thermal energy storage for waste heat utilization, and industrial heat pump technology to efficiently upgrade the waste heat to higher temperatures with the smallest climate footprint possible. One of the technologies HighEFF is working on is to use CO2 as a refrigerant. How can that reduce a climate footprint? Watch the video to find out.

In FME ZEN, SINTEF is studying the integration between electricity and district heating and in FME CINELDI scientists are looking for solutions to improve the electricity grid capacity in a cost-efficient way, which will be important to get enough power to the data centers.

4 comments on “This is how we reduce data centers’ carbon footprint

  1. Excellent overview of the challenges–and opportunities–with data center efficiency. Is there a path to return on investment for private data centers as incentive to move to two-phase cooling and heat capture technologies? In other words, can the operators sell the heat or reduce costs significantly?

    • Ole Marius Moen

      Thank you! Yes, we believe there is. Today, there are examples of datacenters that have made agreements with district heating providers. For example, the infrastructure costs related to heat removal can be shared, or the district heating supplier can deliver cooling to the datacenter in exchange for heat.

  2. Ole, that was a fascinating read! According to Science Magazine, data centers currently consume 1% of total global energy consumption. However, I believe that utilizing waste heat generated in the production of electricity or simply for heating purposes is an excellent solution.

  3. Ashley, IEA also supports your point that data centers constitutes 1% of global energy consumption:
    https://www.iea.org/reports/data-centres-and-data-transmission-networks

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