Qarnot, a French high performance computing (HPC) cloud provider, is using the heat from its servers to warm district heating or water for day-to-day use in buildings. The energy-intensive processes that power the cloud now offer steamy water to residents and allow swimmers to exercise in temperate pools.
By Richard Pallardy
High performance computing (HPC) systems perform thousands of calculations per second. They are crucial to simulation, mechanical engineering and artificial intelligence (AI) programmes, for example, directing huge amounts of data between multiple graphics processing units and other types of chips in order to complete highly complex operations. The energy expenditure is high and most of the excess energy is released as heat.
Liquid cooling systems have become an increasingly popular option for remediating this heat, which can be damaging to the equipment if it rises above 85 degrees Celsius. Traditional air cooling is often not sufficient for these computing systems; liquid is far more efficient at absorbing heat than air. Passing cool water through plates adjacent to the chips that power these systems can channel excess heat away and allow them to continue their work uninterrupted.
But the water heat is often wasted. Qarnot aims to change that by channelling the hot water resulting from its HPC operations to other uses. Not only does the heated water have a renewed purpose, it also reduces external energy costs. Gas and electricity that might otherwise be used to heat water for cleaning and bathing, for example, are conserved.
“We manage the full stack of our services from basic energy needs to the software,” says Nicholas Sainthérant, innovation manager at Qarnot.
Qarnot founders, Paul Benoit and Miroslav Sviezeny, originally aimed to use the waste heat from their servers to warm buildings. In 2010, they rolled out a sleek, innovative new product: a server that could be installed in a residential unit but also serve as a radiator. So, rather than siting their servers in a centralised data centre, with associated costs for cooling, they pursued a distributed model that positioned them in individual apartments.
The servers were cooled by the ambient air in the residences before the air was then returned to the environment at comfortable temperatures, a concept known as passive cooling. However, this solution suffered from seasonality with lower computing resources during summer due to lack of heat needs. The radiators were ultimately discontinued in 2023.
However, hot water is a constant need. Qarnot turned to using liquid cooling technology on their servers and circulating waste heat on a larger scale. This aligned with Qarnot’s move towards HPC applications, which necessitated denser concentrations of servers.
The QBx modules designed by Qarnot are capable of producing up to 11kW of computing power depending on the processor. As many as 24 processors in each unit release heat into aluminium cold plates. Up to 95% of that heat is transferred to the system that heats the water for a given establishment: a pool, a residential unit, an office, a hotel or a district heating system.
The system uses standard water from the tap. “All we need to do is filter out dust and other pollutants,” Sainthérant says.
The heat released can bring water to temperatures of up to 65 degrees Celsius, well within the parameters required for basic hot water needs.
In 2020, Qarnot established a data centre in Kankaanpää, Finland, that produces 100kW of computing power and provides district heating to around 10,000 households. The company now operates some 30 sites across Europe in countries including France, Finland and Greece. New operations will soon be established in Italy and Belgium. All told, Qarnot now offers some 1MW of compute.
Qarnot’s heating system is certified by Title V in France; it is exempt from the thermal regulations enacted in 2012 to improve the energy efficiency of heating systems. Because it uses waste heat rather than primary electricity, it is exempt from being penalised.
In 2023, the company partnered with Inria to launch a programme called PULSE, which stands for PUshing Low-carbon Services towards the Edge. Qarnot’s technology emphasises edge computing. Just as its original space heaters represented a distributed model, so too, its water heating model is diffused. Qarnot distributes data centres across locations where their waste heat can be useful, obviating the need for energy-intensive standalone facilities.
“We deploy infrastructure only where the heat will be useful. We make sure that the computing clients and the heating needs are matched. You can move data without any loss, but you can’t move heat in the same way,” Sainthérant notes.
This model thus represents an improvement on both energy-intensive data centres and heat generation for consumers: it reduces carbon expenditures on both ends.
“There is a lot of traction for decarbonisation in Europe,” Sainthérant enthuses. “Consumers are looking for solutions and we provide one that can actually be implemented tomorrow.”
Qarnot is quick to emphasise that, at its heart, it is a cloud computing solutions provider. Its heating services are sustainable and offer cost savings to consumers. But its actual cloud services are useful too.
Qarnot uses its proprietary Q.ware software to direct data operations to where they are most useful. For example, if an establishment requires more heat, operations are directed there. If it requires less, they are bounced to other locations where Qarnot servers are operating using lightning-quick fibre connections.
Their cloud solution offers something different from traditional data centres or large cloud providers. “Companies need to buy servers, cool servers and install every part of the necessary configuration,” Sainthérant explains. “That is possible for large companies. Then you have cloud providers, such as Amazon Web Services, Azure or Google, that provide computing services. You can avoid cooling considerations, for example, but there is still some complexity.”
Qarnot offers direct access to HPC without either the technical nightmare of establishing custom data setups or the messy payment structures of mainstream data service providers.
In 2021, Adobe Substance partnered with Qarnot to support its 3D renderings platform, for example, indicating that its technology is trusted by established organisations. The company is sensitive to the security risks posed by transmitting proprietary data and uses end-to-end encryption to ensure that it cannot be accessed by bad actors.
The company plans to continue scaling its operations and offering both data and heating services to additional locations. In 2023, it closed a 35 million euro funding round led by Société Générale Ventures and several other major investors, including the European Investment Bank.
Sainthérant is optimistic about the increasing potential for the technology. “One of the problems in the future will be to demonstrate that you can associate sustainability and compatibility and performance without any drawbacks,” he says. “And I'm sure we can.”
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