The Editorial Team at Qarnot.
Qarnot's QBx is a computer cluster optimized for both high performance computing and energy efficiency. Each module integrates 12 to 24 processors whose intensive computing heats water: up to 95% of computer waste heat is reused thanks to this technology.

District heating and data centers: the future of energy transition?

February 22, 2024 - Edito, Green IT


At the start of 2024, France was hit by a cold wave, the most significant since 2018.At the same time, Bruno Le Maire, the French Minister of Economy, Finance, and Energy, announced an approximately 10% increase in electricity prices. This increase comes after the end of the price shield implemented in 2022.

This cold wave led to a spike in energy consumption, putting more strain on urban energy grids. Amid a global energy crisis and rising electricity demand, competition for energy supply is intensifying between cities and digital infrastructures, particularly data centers. These facilities, crucial to our digitized societies, consumed nearly 460 TWh in 2022, accounting for 2% of global electricity demand. 
They are not only significant energy consumers, but also producers of waste heat, a potentially wasted energy source. In a European context where half of the energy consumption is dedicated to heating,1 the waste heat from data centers represents an underutilized opportunity for energy optimization and decarbonizing of heating.

Saturated energy grids in cities: priority for residents or data centers


Energy crisis: increasing energy demand


The explosion in energy demand for data centers


In its latest report, the International Energy Agency announced that global electricity consumption by data centers could reach more than 1000 TWh in 2026, equivalent to the electricity consumption of Japan.

In its 2023 data center forecast report, the Uptime Institute had anticipated the increase in demand for computing and storage capacity and its significant impact on data centers' energy consumption. This energy consumption is not just costly; it also generates enormous carbon emissions and pressures the electrical grid.


In Europe, the rapid growth of data centers has led several cities to adopt moratoriums and new regulations to control the establishment of data centers in response to the saturation of electrical infrastructures in certain areas. For example, Amsterdam established a moratorium in 2019 on new data center construction until 2020. Today, the city allows the construction of new data centers provided that operators can demonstrate a positive contribution to the city and satisfy strict new environmental standards. [See the article on the city of Amsterdam and data centers]


In Ireland, according to IEA estimates, data centers' electricity demand could represent 30% of the national demand by 2026. To preserve the stability and reliability of the Irish electricity system, Ireland’s Commission for Regulation of Utilities set new conditions for connecting data centers to the electrical grid at the end of 2021. These requirements are based on three criteria: the location of data centers based on network constraints, their ability to produce or store the energy needed for their operation, and their consumption flexibility. These measures aim to encourage more efficient use of the grid and the integration of renewable energies, reflecting the government's commitment to decarbonization. 
These measures are particularly significant considering that in June of last year, the Irish electrical system issued an alert regarding the risk of electricity production falling short of meeting demand.2


Permanently supplied with electricity, data centers rank among the world's largest energy consumers. Their energy consumption is mainly divided into two categories:servers’ computation and their cooling (air conditioning, chilled water, immersion cooling, evaporative cooling). Indeed, as they operate, servers generate heat that must be evacuated. Cooling accounts for an average of nearly 40% of a data center's electricity consumption.3


As data centers' energy consumption is a major issue, a question arises: how to transform heat, perceived as waste, into a valuable resource?Is it even possible to harness data center heat where it is needed?

Increasing need for heating in Cities


Since the start of the conflict in Ukraine, numerous crises have disrupted the global energy market. In France, the country's energy bill doubled between 2021 and 2022, despite the protection of the tariff shield. And the primary energy consumption, ahead of transportation, is heating. Considering that energy consumption for heating accounts for nearly half of final energy consumption in France4 and is still heavily dominated by fossil fuels, reusing waste heat presents a promising path to decarbonize the sector.


Waste for data centers, resource for heating networks: what to do with excess heat?


Heating networks, a virtuous solution for exploiting waste heat

Heating networks represent an innovative and sustainable solution for recovering and utilizing the waste heat produced by data centers. Waste heat from data centers can be connected to district heating networks to heat buildings and other facilities, making them more sustainable and providing an economical alternative to traditional heating systems.

Heating networks are widespread in Nordic countries. For example, the city of Stockholm uses the heat from data centers to power its urban heating network. This system, which provides hot water for heating and domestic hot water, significantly reduces dependence on fossil fuels, CO2 emissions, and offers cost stability for consumers.
The heating network is currently the only massive vector for decarbonizing heat in housing at a competitive price.

Heating Networks: France in search of progress?


In France, heating networks account for only 5% of the heat consumed in 2023.5 Yet, they offer numerous advantages and are particularly effective in contributing to the energy transition:
1 - Unlike gas and electricity prices, which have fluctuated significantly since 2021, the prices of heating networks remain more stable.
2 - Heating networks are powered by at least 50% renewable energies or recovery. In 2021, 62.5% of the energy entering heating networks was from renewable energy and energy recovery (ENR&R). According to Fedene, using ENR&R beyond 65% allows for low-carbon, sustainable, and local heat.
3 - They also play a key role in the circular economy by recovering and distributing heat that would otherwise be lost, enhancing the competitiveness of territories.6


State of Heating Networks in France:7



To meet France's ambitions in terms of reducing energy consumption, using renewable energies, and reducing greenhouse gas emissions, the National Low-Carbon Strategy aims to reduce individual consumption of housing and triple the number of homes connected to heating networks by 2035. Indeed, the National Low-Carbon Strategy advocates for “developing urban heating networks and directing production towards renewable heat and recovering waste heat.” In 2019, the Ministry of Ecological Transition launched twenty-five actions to accelerate the deployment of renewable heating and cooling networks.


Why is it so difficult for data centers to reuse the excess heat? 


European regulations are pushing new data centers towards sustainability, with directives like the European Directive on energy efficiency mandating that data centers with a total rated energy input exceeding 1 MW utilise the waste heat or other waste heat recovery applications unless they can show that it is not technically or economically feasible. However, such initiatives are still rare and costly.


Reusing this heat is not simple for several reasons:

First, installation costs are significant for large-scale reuse projects.
Next, the waste heat emitted by servers rarely exceeds 30°C, a temperature too low to be exploited. Therefore, a costly heat pump is required to elevate this heat for transportation.
Moreover, data centers are often located far from heat consumer sites. As heat does not transport well, conveying it over long distances proves relatively inefficient.

Despite the technical and financial challenges related to reusing data centers' waste heat, innovative solutions are emerging.

The Qarnot model: sharing one energy source for two use


Changing the paradigm of traditional data centers 

To address the colossal energy consumption of traditional data centers, Qarnot has developed a distributed and sustainable alternative by deploying its servers directly where IT waste heat can be valorized: near major heat consumer sites.

The Qarnot model has been designed with the aim of optimizing data center energy consumption, considering it not only as a consumer but rather as an energy producer. Qarnot deploys next-generation data centers and scale up waste heat recovery from IT infrastructures.
The solution, that can be compared to a computing rack module, incorporates a patented direct water cooling technology that densifies servers and processors while optimizing their cooling. The clusters take the form of digital boilers (QBx) and can heat water up to 65°C to produce heat for heat-consuming sites (heating networks, swimming pools, businesses...).



Since the heat is captured in the water, Qarnot consumes neither water nor energy to maintain the servers' temperature. The model operates in a closed circuit, and all the water used, rather than being wasted, ultimately serves to heat swimming pools, showers, or industrial sites.
This highly innovative and patented direct water cooling technology allows for the recovery of up to 95% of the heat emitted by computer servers.

Qarnot: How does it work? 


The QBx computing clusters, which integrate 12 to 24 processors, are cooled by a water circuit that collects the heat emitted during computing. Patented heat exchangers passively dissipate the heat emitted by the processors, heating the circulating water. The water go through large-diameter copper pipes and warms up in contact with the heat released by the computing activity. On exit, the water temperature rises up to 65°C and feeds a continuous water circuit. The installations are sized to valorize the heat all year round, the hot water load consumption, regardless of the installation site and scenario (loop, preheating...), with no impact of seasonality on computing capacity.


The model operates in a closed circuit, and all the water used, rather than being evaporated and wasted, ultimately serves to heat heat-consuming sites. Qarnot's computing clusters are already installed in heating networks, municipal swimming pools, and industrial sites. 




Europe's path to decarbonization


As heating and cooling account for over half of the European Union's total final energy consumption, (which is dominated by fossil fuels), the potential of disctrict heating networks emerges as a promising avenue for energy transition. In France, the Energy Transition Law of 2015 aimed to multiply by five the amount of renewable and recovered heat and cold delivered compared to 2012.

In light of these challenges, repurposing the waste heat from data centers to feed these heating networks can contribute to the energy transition, address the challenges of the climate crisis, and promote a circular and sustainable economy.


Moreover, regulations and technological improvements, including efficiency measures, will be crucial to curb the rise in energy consumption of data centers. The European Commission's revised Energy Efficiency Directive, adopted in July 2023, aims to enhance transparency and accountability of data center operators to optimize electricity demand management. Starting in 2024, operators will be subject to reporting obligations related to their energy performance. Data centers with a total rated energy input exceeding 1 MW should utilize the waste heat or engage in other waste heat recovery applications unless they can demonstrate that it is not technically or economically feasible.







(3) ibid.





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