To achieve carbon neutrality by 2050 – a primary goal of the European Parliament – we must significantly reduce CO₂ emissions, particularly in high-impact areas like data center cooling and household heating. Simultaneously, as electricity demand grows faster than renewable energy production, it’s vital to reduce consumption through more efficient systems.

In conversation with DCD, Pier Mattia Barina, senior product manager for chillers and heat pumps at HiRef, shares views on how heat recovery from data centers can achieve both environmental and economic benefits.

Barina explains how this innovative approach can replace traditional heating methods, such as gas boilers and conventional heat pumps, by providing low-cost heating solutions for local communities, placing efficient heat recovery as a central function in lowering emissions.

What is heat recovery anyway?

Setting the scene for our conversation, Barina outlines the potential of heat recovery to achieve the benefits of a symbiotic relationship, whereby data center operators can sell excess heat to nearby communities. Residents, particularly during winter, benefit from this waste heat, which offers a more affordable alternative to traditional heating methods like gas boilers or air-to-water heat pumps. All together, it exemplifies the principles of a circular economy.

“Northern European countries, which depend heavily on district heating, are leading efforts to reduce emissions due to their colder winters,” Barina explains. “With new technologies, they are upgrading systems with modern heat pumps and refrigeration units that have the lowest possible global warming potential (GWP), minimizing CO₂ emissions from electricity production and consumption.”

HiRef, as a leading provider of IT cooling and heat recovery technologies, manufactures chillers, heat pumps, and precision control units for data centers, is exploring various applications for heat recovery, whether for district heating, utility providers, or industrial use, with heating needs ranging from 70 to 120 degrees. Moreover, HiRef is working on developing a new high-temperature heat pump prototype to reach up to 160 degrees Celsius hot water production with its R&D department, increasing the industrial sectors in which to use heat recovery technology.

Why should I care?

For many, exploring sustainable solutions in heating and cooling can seem daunting. While heat recovery technology exists, its potential is meaningless if people are unaware of it. Barina emphasizes the importance of raising public awareness about heat recovery as a viable sustainable heating option:

"In northern European countries, where temperatures fluctuate more dramatically than in southern regions, district heating systems may reach up to 80-90 degrees, but drop as low as -25 in the winter.

“In this symbiotic relationship, communities benefit from lower heating costs as data centers generate residual heat year-round. There is even potential to store heat during the summer, providing increased heating and domestic hot water in the colder months. This recovered heat has broad applications, from heating offices and buildings to warming swimming pools and supporting farming operations.”

Beyond the environmental and economic advantages, Barina illustrates that heat recovery can also play a role in reducing noise pollution. By replacing individual household heat pumps with centralized district heating, the collective noise from residential units is eliminated, offering a quieter urban environment. This presents a valuable opportunity for collaboration between data center owners and municipalities, particularly in city centers where noise reduction is most impactful.

Energy communities as a concept

Building on the idea of heat recovery, the term “energy community” is becoming increasingly common in sustainability discussions. Barina defines an energy community as a network of stakeholders – including data center colocators, residents, industry owners, and others – who benefit from shared heating resources across various applications. This concept revolves around an “energy loop,” which facilitates a flexible exchange of energy between utilities using a shared reserve.

“In this system, when one utility needs additional heat, it can draw from the network, while another utility focused on cooling can release its excess heat into the loop,” Barina explains. “This creates a shared energy pool that ensures efficient use and distribution. The future of energy will rely on this model of energy sharing.”

By fostering such energy communities, we can maximize the benefits of heat recovery, making sustainable solutions more accessible and effective for local communities.

Technological considerations: How does it work in practice?

As data centers scale up to meet today's demands, with cooling capacities reaching up to 250MW, they have the potential to yield around 350MW of recoverable heat.

To enhance data center efficiency, reduce electricity consumption, and curb CO₂ emissions, liquid cooling is becoming a pivotal technology. A notable trend that Barina has observed is the rising temperature of cooling water, driven by the growing adoption of direct-to-chip liquid cooling. This method targets individual chips, allowing for higher water temperatures compared with those when cooling an entire rack. Higher water temperatures enable more efficient heat production, which can be used for the various industrial applications previously mentioned.

“Still, around 20 percent of heat dissipates into the air, so the future will likely involve a hybrid approach – primarily liquid cooling with some traditional air cooling,” Barina explains.

To help visualize the efficiency and environmental benefits of heat recovery, Barina offers a simulation:

• A medium-sized data center with 20MW power consumption
• Cooling system flow temperature set to 20 degrees Celsius
• Transitioning from air-based cooling to water chillers using “free cooling” (without active refrigeration) for over 60 percent of the year in northern Europe, reducing compressor usage
• Upgrading to more efficient water-to-water heat pumps could recover around 65GWh of heat annually, enough to heat approximately 6,000 homes, equating to a small town of 12,000 people
• Electricity savings of about 3.2GWh per year and CO2 emission reductions of 600-650 tons annually.

Barina notes that while the simulation focuses on a 20MW data center, this approach can easily be scaled up for larger facilities. “For instance, a 250MW data center in Copenhagen, situated within a 50km radius of the city center, has the potential to supply heat to approximately 20 percent of the city’s homes,” he explains. This highlights a growing trend of relocating data centers from rural areas to more populated urban centers to maximize their heat recovery capabilities.

Becoming best-in-class in heat recovery

Having explored the ‘what, why, and how’ of heat recovery in data centers, we turn to Barina for his insights on the key characteristics that define a best-in-class facility. Understandably, a significant aspect of this is leveraging the latest heat recovery technologies, which effectively reduce electricity consumption.

Integrating low global warming potential (GWP) refrigerants that comply with the EU F-Gas Regulation also enhances the compatibility of data centers with district heating networks, further promoting sustainable energy systems.

Looking ahead, Barina emphasizes the importance of designing data centers with redundancy in mind. This ensures that heating and cooling remain unaffected in the event of a system failure: “Round-the-clock monitoring to detect and address potential issues before they escalate will be key to maintaining a robust and redundant design.”

He points out that the most common failures in cooling systems involve electronic components like pumps, fans, compressors, and control valves. While these failures may only reduce cooling capacity by five to 10 percent, having redundancy is critical for restoring full capacity quickly. “Data centers cannot afford any cooling interruptions, as downtime leads to financial losses for both operators and their clients,” Barina notes.

Finally, designing for scalability is essential to accommodate the growing demand for IT capacity, ensuring that facilities can support increasing power requirements.

All the gear and the idea

Throughout the conversation, Barina emphasizes the need to demonstrate the benefits of heat recovery to municipalities, communities, and the public. He argues that data centers can fulfill a dual purpose: providing essential IT infrastructure while also supplying heat, especially in underutilized areas such as vacant land near towns.

HiRef has successfully implemented several district heating projects and is set to launch its first heat recovery initiative from a data center in Milan in 2025. The company plans to develop specialized heat pumps tailored for various applications, such as district heating and industrial use, rather than offering a one-size-fits-all solution. It seems it would be wise to keep an eye on HiRef as it positions itself as a leader in the industry.

Ultimately, the conversation highlights the strong potential of heat recovery in data centers to deliver significant advantages to surrounding communities, particularly in terms of environmental sustainability and energy savings.

HiRef's XVA K and KVW heat pumps can serve a variety of heat recovery applications by harnessing residual or low-temperature thermal energy for useful purposes, helping to enhance the overall energy efficiency of the system. Visit our website hiref.com to learn more!