Intelligent Data Centres Issue 30 | Page 41

HOW ENERGY IS STORED ON-SITE AND OFF-SITE HAS THE POTENTIAL TO RADICALLY SHAKE UP DATA CENTRE POWER CHAIN DESIGN AND OPERATION . www . intelligentdatacentres . com
EXPERT OPINION
While questions remain about how sustainable Li-ion is when measured across its entire life cycle , from sourcing raw materials to operation , disposal and recycling , the use of Li-ion battery banks in data centres of all sizes will continue to grow in the near term .
The UTI says : ‘ There are now dozens of companies with Li-ion recycling services or technologies ’ and it advises that ‘ the best way for data centre operators to reduce the impact of Li-ion use will be to open a serious dialogue with suppliers .’
Meanwhile , large deployments are being planned . In late 2020 , Google said : “ In Belgium , we ’ ll soon install the first ever battery-based system for replacing generators at a hyperscale data centre … batteries are multi-talented team players : when we ’ re not using them , they ’ ll be available as an asset that strengthens the broader electric grid .”
In every sector , data centres already make use of tens of thousands of cells in battery systems – they may also need to renew thousands of them each year .
Lithium is not the only battery technology option available . More sustainable battery types , with high enough energy densities , are being developed and some may start to compete as they become more costeffective ; these include flow batteries , zinc nickel and sodium-ion .
Using a less expensive and more common element than Lithium , Sodiumion cells can be recharged in around a fifth of the time . The technology is costeffective and sustainable , which includes using local bio-based energy sources in the battery supply chain .
2 . Kinetic
Flywheels have been used to store energy for thousands of years . Today , in data centres across the world , tens of thousands of flywheels are used for shortterm energy backup power .
Kinetic energy , as the name suggests , is energy generated via motion of an object . In classical mechanics , Kinetic Energy ( KE ) is equal to half of an object ’ s mass multiplied by the velocity squared . Kinetic energy = ½ ( mass )*( velocity ) 2 .
A flywheel system stores energy mechanically in the form of kinetic energy by spinning a mass at high speed . Electrical or mechanical inputs spin the flywheel rotor and keep it spinning until called upon to release the stored energy .
The amount of energy available and its duration are governed by the mass and speed of the flywheel .
Kinetic flywheels have seen success as energy storage components in the UPS power infrastructure . These systems indirectly provide electrical energy for the data centre from low- and highspeed flywheels .
3 . Compressed gas storage
Liquid air energy storage
Liquid air energy storage ( LAES ) stores liquid air inside a tank which is then heated to its gaseous form , the gas is then used to rotate a turbine . Compressed gas systems have high reliability and a long life span that can extend to over 30 years .
LAES , also referred to as Cryogenic Energy Storage ( CES ), is a long duration , large-scale energy storage technology that can be located at the point of demand . The working fluid is liquefied air or liquid nitrogen (~ 78 % of air ). LAES systems share performance characteristics with pumped hydro and can harness industrial low-grade waste heat / waste cold from colocated processes . Size extends from around 5MW to 100 + MWs and , with capacity and energy being decoupled , the systems are well suited to long duration applications .
Adiabatic Compressed Air Energy Storage
An Adiabatic Compressed Air Energy Storage ( A-CAES ) System is an energy storage system based on air compression and air storage in geological underground voids . During operation , the available electricity is used to compress air into a cavern at depths of hundreds of metres and at pressures up to 100 bar . The heat produced during the compression

HOW ENERGY IS STORED ON-SITE AND OFF-SITE HAS THE POTENTIAL TO RADICALLY SHAKE UP DATA CENTRE POWER CHAIN DESIGN AND OPERATION . www . intelligentdatacentres . com

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