A leisure center in Exmouth, Devon, is using a small Edge data center, dubbed a "digital boiler" to provide some of the energy needed to heat its swimming pool. The system has been installed by a UK startup, Deep Green, which says its system could help with the energy crisis facing thousands of British swimming pools.

Deep Green installed a 28kW system that runs an HPC cluster available to cloud customers. The system, based on Deep Green's own immersion cooling tubs, uses oil to remove heat from the servers, which is then passed through a heat exchanger to heat the pool. Deep Green pays for the electricity it uses and gives the heat free to the Exmouth Leisure Centre.

Mark Bjornsgaard of Deep Green – Deep Green

Deep Green says its heat donation will cut the pool’s gas requirements by 62 percent and save £20,000 ($24,000) per year while reducing carbon emissions by 25.8 tonnes.

Total immersion for swimmers?

"This could be an absolute game changer for us," said Jane Nickerson, CEO of Swim England, in a BBC radio interview. "We know that swimming pools save the NHS and care services a minimum of £357 million ($435m) every single year, and with energy costs spiraling we've been panicked - with the number of pools that could have to close, and what they need to do to become more energy efficient. We have to become a much more sustainable industry."

Swimming pools and leisure centers promote fitness, meaning that fewer people need treatment and other care.

Deep Green CEO Mark Bjornsgaard told the BBC that his company originally had a target of installing digital boilers in seven swimming pools in 2023, but has upgraded that to 20 in response to demand. The company would like to put a data center under "any pool" he said: "Companies that have green ambitions and want to support their local pool - please get in touch."

The company already has further projects signed in Bristol and Manchester.

Around 79 percent of pools in England face closure, and around 1,500 pools could benefit from free heat, Deep Green says. Energy costs for pools have increased 150 percent since 2019, according to pressure group UK Active. The technology could also be used in any business which has a need for heat, such as bakeries, distilleries, or laundrettes, adds Deep Green.

Digital boilers have been proposed for some years, by companies including Qarnot in France which was founded in 2010, and has been offering this service for around eight years. Qarnot still offers digital boilers to homes and businesses, using second-user servers provided by ITRenew, and has also adopted oil-based immersion cooling from European immersion cooling company Asperitas. Another French firm, Stimergy, heated a swimming pool in Paris in 2017 but does not appear to be currently active. UK firm Heata is also offering compute-based water heaters and recently partnered with cloud service provider Civo.

Other companies in the field have included Germany's Cloud&Heat, which has moved away from digital boilers to efficient Edge data centers. Nerdalize of the Netherlands disappeared, as did Exergy of New York.

deep green digital boiler.jfif
A picture of the Deep Green boiler tweeted by CEO Mark Bjornsgaard – Deep Green

Deep Green seems to have been operating quietly till today's launch, but Bjornsgaard has been leading the project for six years, according to his LinkedIn page, while CTO Matt Craggs joined in December 2021.

What tech does Deep Green use?

Deep Green's site has branding from Dell, Nvidia, and US immersion cooling specialist GRC but apparently builds its own tanks, which could reach a capacity of 40kW, the company said. Craggs told DCD by email: "We have been working with our own tubs at the moment but are in conversations with GRC and Submer about utilizing their kit for future installations."

The tubs contain AMD Epyc single CPU servers from Dell, each configured with four A100 80Gb PCIe GPUs and 4TB of SSD, Craggs said. The servers are installed on an "open chassis, to ensure the most efficient heat transfer."

Overall, the HPC cluster at Exmouth has 12 four-CPU cards, CEO Bjornsgaard told DCD. The servers are being used for AI training and machine learning workloads at the moment but could be configured for cloud services and video rendering in the future.

"At this early stage, we're renting the compute bare metal to AI/machine learning people through the aggregators," said Bjornsgaard, adding that the company is hopeful that media coverage of the story will attract direct compute customers in the future.

The Exmouth Leisure Centre has a 25m swimming pool as well as a children's pool which needs around 222,000 kWh per year to heat. "Our expected heat transfer from the kit is 139,284 kWh a year, equivalent to 62 percent of the pool’s heat needs," said Craggs. There is room in the compute tub for extra servers that could extend this to 70 or 80 percent of the pool's heating needs.

The installation would help Exmouth Leisure Centre "continue to be a key asset for the local community," said Peter Gilpin, CEO of the center's operator, LED Community Leisure. "We are already seeing the benefit. I’m certain this will transform leisure centers up and down the country for the better."

Deep Green's site offers to supply, install, and maintain digital boilers for free, including the costs of connecting pipework. The electricity they use is paid for upfront, based on the hourly charge currently paid by the customer.

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