As global economies begin to regulate their water conservation efforts, it is only a matter of time before the data centre sector, alongside many others, is held accountable for its use of water. Tim Bound, Director for Transtherm Cooling Industries, a leading innovator in adiabatic cooling technology, encourages specifiers to move in favour of a water-conscious UK data centre sector sooner rather than later.
Electricity and water are the two main resources required for data centre operation, yet for the UK data centre market, the use of water remains of little concern compared to its counterpart sectors around the world.
A recent US Geological Survey has suggested that by 2020, data centres across the pond will consume around 660 billion litres of water per year, making the US data centre market one of the highest consumers of a rapidly depleting natural commodity. The statistics are on a similar scale for the UK, with data centres relying heavily on water in order to regulate and maintain internal temperature, especially in facilities using traditional cooling tower methods compared to more efficient hybrid or adiabatic systems.
In the US, water consumption (or lack of it) is a critical component in the specification of cooling equipment, even more so since California’s drought in the summer of 2015 shone a light on the commercial use of water. While it is arguable that weather variables make water more abundant in the UK and therefore make it less of an immediate concern, many manufacturers of water-conscious and highly efficient cooling equipment believe that saving water should be a moral decision in the same way recycling and reuse of other precious resources has become.
The conservation of water is a humanitarian issue and one which should rightfully cause political and social concern at a global level, not just in the countries which experience drought or have geographies which are synonymous with less abundant natural resources.
The latest statistics from the United Nations states that in industrialised nations, industry consumes 80% of water available for human consumption, with the World Health Organisation stating that half the world’s population will be living in ‘water-stressed’ areas by 2025.
These statistics – and many more like them – should make one of the world’s most progressive and technologically advanced industries sit up and take note of its consumption rates and, more importantly, what it can do to improve the environmental impact of its mission critical operational processes.
Cooling towers, hybrid and adiabatic technology – the truth about their water consumption
There are three common specification choices for data centre cooling; traditional cooling towers, hybrid coolers and adiabatic systems.
Cooling towers are most frequently specified for budget projects or those with severe space restrictions, whilst hybrid equipment has long been the habitual specification choice for data centre designers unsure of the true benefits of switching to adiabatic alternatives.
All three options will save significant amounts of energy when compared to typical compressor based chilled water systems and can achieve far higher Energy Efficiency Ratios (EER) and, as modern data centres are designed with higher supply air temperatures are increasingly used as the primary source of cooling rather than rejecting heat from chilled water plants.
Take the example of a typical compressor-based chiller which will consume 1kW of energy for every 3-4kW of cooling delivered. Compare this to an equivalent sized adiabatic solution, which for the same 1kW of energy consumed, will deliver up to 75kW of cooling.
In terms of EER, this difference translates as an approximate EER of 4 (4kWth/1kWe) for a conventional compressor solution and an impressive EER of around 75 (75kWh/1kWe) for the equivalent ambient cooling solution. This of course, translates to substantial energy and cost savings for energy-hungry mission critical environments.
But let’s concentrate on the water consumption. Given that cooling towers rely on evaporative cooling throughout the year, achieving little to no sensible cooling, and hybrid systems begin to evaporate water in ambient temperatures as low as 10°C, it will be no surprise that adiabatic coolers consume less than 1% of the water used by traditional cooling towers and approximately 2-4% of that used by wetted surface hybrid coolers.
Even when operating in wet mode, adiabatic systems automatically vary the amount of water used to minimise consumption whilst still hitting required water temperatures in varying ambient conditions.
If we examine those figures more closely, as water consumed in cubic meters over a one-year period for a 1000kW unit, an adiabatic cooler consumes 92 m³of water, compared to a wetted surface hybrid cooler which requires 8,647 m³ and a conventional cooling tower which is more in the region of a staggering 18,220 m³.
Latent heat of evaporation dictates that for every kW of heat that a cooling tower dissipates it must evaporate 1.6kg of water. On top of this, in order to stop cooling tower base tanks from being clogged with the residual scale left over from the evaporation process, an additional amount of water must be bled off and replenished from a mains water supply.
Depending on how hard the water is, this can add an additional 20% to 100% water consumption on top of the water evaporated. At a typical 30% increase this means that the total water consumed is 2.08kg per kW of cooling.
For a typical 1,000kW cooling system this gives a cooling tower water consumption of 2,080kg every hour. In contrast, adiabatic coolers, designed with water conservation in mind, would typically consume 350kg every hour and only for 3% of the year rather than 100% of the year.
Water-conscious specification
Specifiers, whether working on a large-scale data centre project or a smaller facility can uphold their moral obligation by working with manufacturers who innovate technologies which preserve both power and water.
Without a doubt, water is more abundant here in the UK and for the next few years, the importance of water conservation isn’t likely to reach critical levels for us.
But when specifying water-consuming plant designed to last in excess of a decade, it is vital that water consumption rates are taken into account now, in order to prevent expensive replacements further down the line, when the Government inevitably regulates water consumption in the data centre market.
