The data center industry’s rapid expansion in recent years is well documented and shows no sign of abating. A recent report suggests that by 2025, data centers will consume one-fifth of all the electricity in the world.
Stats like this have served to bring the sector under the spotlight and it has come under increasing pressure in recent years to reduce its carbon footprint and operate more efficiently.
Primary Source Cooling
The primary source of energy consumption in most data centers is cooling. This energy usage mainly comes from large industrial equipment such as pumps, chillers, and cooling towers, which are used to regulate data center temperature. It is important for the air conditioning industry to take its energy efficiency responsibilities seriously. Power Usage Effectiveness has helped steer the industry down a greener path
Power Usage Effectiveness (PUE)
Measures like Power Usage Effectiveness (PUE) have helped steer the industry down a greener path and technological strides have been made in order to increase efficiencies, but PUE doesn’t tell the whole story.
The use of water in data centers is increasingly coming under the microscope.
Global Water Crisis
We live on a blue planet…yet only 1% of the world’s water is useable. Growing populations, intensive urbanization, and industrialization are putting strains on this 1% like never before.
In 2015 the World Economic Forum in Davos listed water crises for the first time as the world’s leading threat and this is not a crisis limited to developing countries. As an industry, we cannot ignore this.
Air-Side Optimization
Around ten years ago, the optimization of air temperatures was introduced as the latest way for data centers to increase efficiencies.
At the time, many data centers ran at 20°C to 22°C. However, as server technology advanced, data centers were able to run at higher temperatures which reduced the cooling requirement and provided more opportunity to utilize free-cooling.
Airedale International pioneered this with the introduction of chillers specifically designed to take advantage of the free-cooling opportunity, resulting in a lower cost of ownership for operators.
Adiabatic Cooling Systems
Air-side optimization has been built on with the introduction of adiabatic cooling systems In recent years, air-side optimization has been built on with the introduction of adiabatic cooling systems. This technique incorporates both evaporation and air cooling into a single system.
Process
The evaporation of water, usually in the form of a mist or spray, is used to pre-cool the ambient air to within a few degrees of the wet bulb, allowing cooler and more efficient operation.
The use of spray or mist means water use is significantly lower than with more traditional evaporative systems, but a conservative water usage estimate for a modern data center employing an adiabatic cooling system would still be 500,000 liters /1MW/Annum.
Water Shortage Concern
As data centers grow larger, this becomes a real concern, particularly in regions where water shortages have been identified as a threat. To put the figures in context, a typical 50MW data center employing adiabatic cooling would use approximately 25,000,000 liters per year, about the same as 152 UK houses.
Storage And Treatment
The water usage itself is not even the whole story. This water still has to be stored and treated which increases capital costs and as with any mechanical equipment exposed to continuous water contact, the cooling plant has been seen to suffer from increased degradation, putting a strain on OPEX costs too.
Water Side Optimization
Airedale developed an innovative approach to data center cooling Having recognized the need for cooling systems that provide something close to the efficiencies that can be achieved with adiabatic cooling, but with a more sensitive approach to water conservation, Airedale developed an innovative approach to data center cooling, that takes the philosophy behind air side optimization and evolves it further.
Airedale calls this Water Side Optimization. And Water Side optimization is proving its worth in many of the world’s leading data centers already.
Deliver Free-Cooling
The philosophy of water side optimization is based on taking an optimized air environment and looking at what other variables can be adjusted in order to deliver more free-cooling.
Assuming that the air within the data center white space stays at the same temperature, the next step was to reduce the approach temperature whilst opening the difference between water supply and water return.
Temperature Difference
Implementing innovations within the plant equipment means the supply and return air remain as before, but supply and return water temperatures are higher, thus the approach temperature is reduced.
We see a fixed temperature difference of 12°C TD on the airside with the fluid side being opened out to 10°C and the approach temperature closing from 6°C to 4°C.
Features Of The Approach
- Higher water temperatures, meaning less mechanical cooling
- Lower fan speeds
- Lower pump power
- High cooling surface area
Air Path
Air is introduced directly to space via sidewall diffusion, minimizing air side pressure drops To achieve this, free-cooling chillers are matched to large surface area chilled water coils in either indoor CRAC units or fan walls.
The air path is simplified using hot aisle containment, creating a pressure differential that draws cool air through the servers and out of the white space via ducts and back to the air conditioning plant via a common plenum. The air is introduced directly to space via sidewall diffusion, minimizing air side pressure drops.
Benefits
- Less mechanical cooling meaning more efficient chiller operation.
- Lower fan speeds meaning more efficient indoor unit operation.
- Lower pump power meaning more efficient water transfer.
- Large coil surface leads to increased cooling for less footprint (more cooling capacity per m.)
This is all managed with an intelligent controls platform that monitors fluctuating demand within the white space and dynamically operates the system at its most efficient operating point.
Concurrent Cooling
Based on average temperatures for London, an extra 2°C creates many more hours of free cooling.
14% more free cooling (59% in total) can be achieved with Water Side Optimization, with all but 1% of the rest of the year being covered by concurrent cooling (a combination of free cooling and mechanical), giving huge benefits in terms of chiller efficiency.
This system could provide free cooling for over 50% of the year in all of Europe’s major data center hubs (London, Frankfurt, Amsterdam, Paris, Dublin).
