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Is UV the answer to liquid cooling concerns?

Wayne Powell

Wayne Powell

Regional Sales Manager at Evoqua Water Technologies
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Image credit: klyaksun / Shutterstock.com


Look at a photo on your phone. The chances are, this photo is not stored locally on your device, but on a hyperscaler cloud, pulled up from a data centre.

Compared to running physical infrastructure in dedicated facilities, cloud storage is relatively energy efficient. But the processing of this interaction does have a by-product: heat. Heat affects performance and increases risk in the data centre, so it is often mitigated with water cooling. 

Studies referenced in the Nature Portfolio Journal show that a single medium-sized data centre currently uses around the same amount of water as three hospitals. Data centre cooling towers ‘consume’, or lose, water through evaporation, blowdown, and drift.

Evaporation from heat removed from the condenser water loop accounts for around 1% of the cooling tower water flow rate. Blowdown is estimated to make up 0.5% of the condenser water flow rate and drift around 0.005%. The system needs a source of fresh water to make up for these losses. When combined, this means a 1MW data centre using water cooling will use about 6.75 million gallons of water per year.

And as much information as we currently draw from data centres, AI and the Internet of Things (IoT) is about to create exponential growth in the data processed by data centres. Think back to that photo. The 10 billion devices used directly by people are dwarfed by the 29.3 billion devices expected online by 2030; devices, connected via the IoT, communicating, accessing information, and generating heat.

With no operators needed to transact information, the data centre industry is facing an explosion in demand just as water resources become scarcer and public scrutiny on how they obtain and use these resources grows stronger.

In fact, data centre water consumption is already under scrutiny. This is caused in part by factors that make certain locations ideal for data centre placements. The primary concerns have historically always been capital expenditure (CapEx), access to energy, and regulation.

Data centres thrive in dry climates. It’s easier to remove heat from dry air, regardless of the initial temperature. They also need flat, open spaces in areas at low risk of natural disasters. All these factors mean data centres are often found in arid, desert or scrubland locations. Areas that happen to have low access to sustainable sources of water for cooling.

This led to some data centre operators drawing more than half of their water from potable sources – in some of the world’s most water-stressed areas. 

With an impending explosion in usage and questions of their water use gathering pace, finding sustainable and low-cost water treatment for data centre cooling is an absolute imperative.

Effective water treatment can reduce water consumption in growing data centres 

As water is cycled through evaporative units, minerals build up to a level that requires replacement with fresh water.

Disinfection and filtration can be major contributing factors in reducing the consumption of fresh water. Water treatment helps to remove scale-forming minerals allowing water to be re-used in more cycles. Increasing these ‘cycles of concentration’ reduces the water intake needed to cool data centres. Disinfection and filtration help reduce the water consumption in existing centres with relatively low cost or operational impact or physical footprint.

Meta is one company that has already committed to ‘Recycling water multiple times through our cooling and humidification system in all of our data centres.’ A pledge that will require some level of water treatment and filtering – with its own environmental impact.
 
UV as a sustainable solution

UV disinfection prevents harmful microbial growth that poses a danger to employees and can also disrupt the performance of the cooling system.

Ultraviolet light has a wavelength of 253.7 nanometres which, if used according to manufacturers’ specifications, can neutralise bacteria, viruses, moulds, algae and other microorganisms, preventing them from multiplying. 

The combination of a high-efficiency media filtration system and UV can remove contaminants before they disrupt the operation or lead to harmful levels of bacteria in the water supply.

In fact, modern, high-capacity UV systems, when used with a separator, can deliver a high dose of UV to the cooling loop and turn over the entire reservoir frequently.

When looking at the needs of data centres, and their growing demand for efficient, high-capacity water treatment, UV has a remarkable set of advantages. UV is environmentally safe. It is effective on a wide range of pathogens without the need for chemicals. It provides continuous operation at low operating costs and no operator licensing is required. There is a low maintenance requirement, and it significantly lowers the need for biocides. In a data centre example from Evoqua, continuous UV treatment reduced the need for biocide by 75%.

On-site hypochlorite generation system for lower operation impact

Effective water treatment often relies on a combination of multiple systems or technology. Some chemical dosing may still be required. In these cases, implementing a sustainable solution relies on limiting the exposure, use, and transport of materials that can be considered hazardous to the environment.

On-site hypochlorite generating systems can be used to treat water with a sodium hypochlorite solution using monopolar electrode technology. At Evoqua, for example, we provide OSEC systems that generate a <1% sodium hypochlorite solution through the electrolysis of brine, consuming only water, salt, and electricity. Producing hypochlorite on-site and on-demand, the system provides treatment without the need for commercial chlorine suppliers and transporting or handling chemicals and their by-products.

When compared to bulk hypochlorite, this has been shown to reduce vendor deliveries by about 66%. This means fewer trucks on the road, lower emissions, lower community impact, and total carbon footprint.

The use of on-site hypochlorite generation furthers efforts towards sustainable management and contributes to overall safety of your water profile. But OSEC systems can also significantly lower operating costs as the operation is completely automatic. This makes these systems ideally suited for remote or low-staffed data centre use.

Sustainable choices need to be made now

As the information revolution, brought on by the IoT, cluster computing, and more connected people than ever, the sustainability of every stage of the process will come under examination.

As well as self-imposed reporting and accountability from hyperscalers, regulation will also make changes a question of ‘when’ rather than ‘if’.

The Green Grid (TGG) has already joined forces with the US Environmental Protection Agency (EPA) to survey data centre energy and water use to issue a US EPA’s 1-100 ENERGY STAR score for data centres OSEC systems based on their sustainability.

After measurement, the next step will be more enforced measures, aimed at limiting this impact. UV treatment and OSEC systems are a long-lasting, low-impact way to decrease water use

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