The Covid-19 pandemic added 20% growth to data centres in the first three months, with lockdown meaning more adults are working from home and families are streaming more content during the day. The implementation of 5G and streaming video is rapidly driving data growth and with users unlikely to reduce their energy usage, actions such as reducing cooling losses at data centres are important, with better pumps and more efficient controls are a key enabler in facilitating this.
There is increasing pressure from the EU for data centres to be
powered by renewable energy, however the first step of this is to reduce the
power consumed by the data centre infrastructure.
The Green Grid, innovator of the Power
Usage Effectiveness (PUE) metric, has
recently proposed the introduction of a new data-centre metric – WUF, Water
Usage Factor and as PUE’s drive lower, data-centres are now being judged for
water consumption as well as electrical energy use.
80% of all data centres utilise chilled-water systems for cooling,
15% use direct-expansion refrigeration systems and just 5% use air based
evaporative or adiabatic cooling systems.
Consulting Engineer, Ian Bitterlin, who carried out the research,
chilled-water systems (the dominant technology used to date) have continued to
evolve technically with better controls, heat-exchanger technology, variable
speed compressors, fans and pumps and operationally, with flow water
temperatures rising from the legacy 6°C to 18°C (and higher) enabling high percentages of
free-cooling in suitable climates, an older technology has recently proved more
popular – that of evaporative or adiabatic cooling.
“In pursuit of achieving an ever lower PUE,
the advent of fresh-air cooling solutions
brought along with it adiabatic cooling solutions, where water is used
to take advantage of the wet-bulb ambient temperature and crucially
humidification of high volumes of fresh-air.
Perhaps for the first time in Europe, water consumption in data-centres is
a growing issue.”
Evaporative and Adiabatic cooling technology,
known before Roman times in high-status dwellings, use water to increase the
humidity of warm dry air and reduce its temperature from the dry-bulb to the
wet-bulb value. For example, in the UK
when the external ambient is near the record high of 35°C dry-bulb, the
addition of water vapour can get the air-stream temperature down to 23°C wet-bulb and
then use that to cool the data centre.
Evaporative and Adiabatic cooling
systems potentially save 20-30% data centre energy (compared to chilled water
systems) and do not use pumps. However, they have not proven to be universally
popular as they need a lot of space and use a lot of water.
Bitterlin comments: “Despite the potential energy saving of Evaporative
and Adiabatic cooling systems, chilled-water systems are, in my opinion, the way
forward as they use hardly any water compared to the ‘modern’
competition of evaporative cooling technology. The performance of chilled water systems is
much improved by high-quality variable-speed pumps and chillers fitted with Evaporative
or Adiabatic cooling offering total control of internal air temperature and
“The majority of enterprise and
colocation data centres have partial load, typically <50% at maturity,
rarely high and never 100% – this means that for energy saving reasons the
chilled water pumps must be; designed for variable speed drives, optimised for
operation at 40-50% – like modern power systems (UPS) .
“A pump designed for 100% flow but only
having 30% load uses 100% power but the same pump running at 30% flow rate only
consumes 2.7% of the energy.”
David Williamson, Director of Wilo UK, comments: “Data centre cooling plants with Wilo pumps provide an opportunity to improve on past performance with partial load and variable speed pumping and offer a high level on control to meet a wide range of systems.”
of the hydraulic system and measurement of power performance of existing and
legacy cooling systems we are able to select replacement pumps that can achieve
the desired system performance whilst reducing energy use. Often such upgrades
further increase data centre resilience and availability.”
The Wilo GIGA range of pumps is
extensive, covering all applications within the Data Centre environment. The
Atmos GIGA Series has recently been upgraded to provide greater efficiency and
the Stratos GIGA leads the industry in high efficiency providing performance
greater than IE5 through EC motor technology up to 22kW.
Far from the perception that evaporative or
adiabatic are modules taking over the market, the sales of chilled-water
systems have proven to be increasingly resilient, aided considerably by an
offshoot of the adiabatic technology; the air-cooled chiller enabled with
adiabatic sprayed free-cooling coils.
With the ability to have compact cooling
units in the room of 3.5m3/100kW, using water to transport heat far
more effectively than air, advanced micro-channel heat exchangers, higher range
chilled water temperatures, free-cooling and the opportunity in hot/dry ambient
conditions to use water spray to reduce the PUE to a, location dependent, range
of 1.06 in London, 1.07 in Madrid or Frankfurt and 1.18 in Dubai.
If engineered correctly, chilled water cooling
can no longer be considered as wasteful of energy achieving an overall PUE at
full load, with all the other systems included, of 1.2 in northern European
The final piece of the puzzle is to cater for
the endemic partial load and here is where the chilled water pump, allied to
variable speed pumps and electronic proportional valves, come into their
own. The product that, with the chiller,
was most threatened by air-based direct and indirect adiabatic or evaporative
cooling can look forward to a successful future in the data centre industry
that we have all come to rely on so much.