Cooling Optimisation

26-04-2012 - John Hatcher

Data centres have always had stringent requirements relating to heating and cooling.  The gap between the lowest and highest temperatures at which a data centre can operate efficiently has always been carefully controlled to ensure optimum working conditions. Although the efficiency of equipment is improving and power requirements to equipment are reducing, there has actually been a negative effect in terms of cooling. Here, the cooling requirement is increasing and we have therefore had to re-think the way we address this issue in data centres.

As the capacity of data centre’s increase, clients are therefore looking for ever more efficient ways of maintaining this optimum operational environment.

Set against this is the 24/7 nature of the industry, which means that any upgrade to existing data centre’s has to minimize disruption and also offer more efficient, greener solutions. 

With data centre’s having consistent demands on power, regular reviews of energy systems are essential to avoid spiralling energy costs and this is the reason why many data centres have been subject to recent refurbishments. 

Another key focus for data centres is the Government’s Carbon Reduction Commitment Energy Efficiency Scheme, which will mean significant penalties for large organizations that are heavy users of electricity.

On a positive note, the power requirements to equipment are reducing as technology becomes more advanced, which is helping to reduce the overall energy cost for a business.  However, as heating systems have become more efficient, cooling mechanisms have struggled to cope with the sheer increase in size and capacity of data centre’s.

Meeting cooling needs
Cooling systems have been one of the reasons why energy management specialists have been brought in by many data centres to analyse their systems and make recommendations on the ways they could improve their effectiveness and energy efficiency.  Specialist energy management techniques may mean being able to reduce electrical requirements by more than 75 per cent.   One of the most popular methods of doing this is by non-indirect cooling from fresh air, using evaporative cooling methods.  This can replace chilled water systems and Direct Expansion (DX) systems, depending on the plant and space availability. 

Energy reduction can take the form of integration of IMOP units - inductive motor optimisation panels to regulate the motor controls for pumps and fans.  This can help data centres to use energy more efficiently, which ultimately may mean a reduction in the levy which will be imposed as part of the Carbon Reduction Commitment Energy Efficiency Scheme.  

The IMOP is installed close to the motors or electrical equipment, where it stores reactive energy within the IMOP unit itself and this supplies the motors with the same energy that it needs to run. This means there is no longer a requirement for all the electricity to be provided by the grid.   As a result of the power not being pushed through an electrical infrastructure and wasted within a facility, it can achieve close to 100% efficiency.

This results in a more efficient cooler distribution system where heat is no longer being lost in the form of watts and can account for a reduction of between 6% — 25% electricity use - therefore optimising the power factor.

There is also no longer the need for excess power to be supplied to a system - instead, it can be constantly stored and recycled between the IMOP and the motors, with the IMOP allowing a more intelligent approach to electricity consumption. 

Other technologies are often addressed during our work within data centre’s,  these, including looking at the electricity consumption used for lighting.  Replacement energy saving LED lighting can be used instead of fluorescent lamps, which can reduce energy consumption by up to 50% plus and heat output by up to 60%, subject to applications.

It is often recommended that data centres install lighting control systems with Passive Infra Red (PIR) motion, which enable reduced usage and do not rely on operators switching off lights.  The infra-red sensors and circuits receive a signal from their sensors corresponding to a person moving in the field of view, therefore offering a high level of efficiency.

Uninterrupted power
When considering upgrading the heating and cooling of a data centre, the main challenge is to ensure that it can remain operational of at all times.  This can only be achieved through consultation with the end-user and careful planning of the schedule of works.  Within normal 24/7 activities, any works to be carried out will require precise planning and tight timelines to ensure the system is capable of maintaining non-interruption to normal operations.

One way this can be done is by the installation of temporary containerised generator systems, which need to be fully commissioned on site prior to any changeover of sub-main cables.  These systems can be pre-installed and available for final connection and testing to reduce the changeover time.  The same applies to AC units and UPS systems, where anything is possible with careful planning and understanding of the client’s requirements and a commitment by the contractor to flexible working arrangements.
Uninterrupted Power Supply (UPS) systems are generally N+ 1 or +2, which relates to standby power redundancy, which can be extended to +2 or even +3 configurations to cover ultra-critical systems and provide almost 100% guaranteed power cover..
Redundancy of power is essential for critical applications, such as data centers or in demanding environments such as industrial process control, where any downtime represents loss  of Data or Critical information is a costly and unwelcome interruption.  
Incorporating this provides the facility for maintaining the system and, subject to load levels, the UPS modules can be isolated independently for maintenance and replacement of equipment and batteries, .subject to the configuration of the system External wrap around facilities are required on the Input/Output panels.

On many projects, it makes sense to transfer to the data centre’s in-house generator system, which provides a stable supply, without any external influences on main interruptions or power dips, which can be reinstated on completion of the works.  This then allows the UPS to be taken offline for the required task.

Many larger generator systems have G59 compliance, so that they are able to synchronise with the local supply network and provide an invisible changeover both forward and backward, so the data centre does not experience any interruptions to the supply.
A recent data centre upgrade we completed included addressing the whole infrastructure of the data centre to provide greater

expansion of the data centre halls and internal IT equipment.  This included the introduction of a blade server and similar IT equipment, as the availability of power and cooling on the base build was not sufficient to support power and cooling requirements of new technology equipment.

A new external heating and ventilation supply on the premises was installed.  This included new HV Switch Rooms, two of which included 3MVA with 11000/415v transformers, which were installed on package substations to provide an alternative source of power.

A recent data centre refurbishment
We installed, tested and commissioned temporary containerised generators, which allowed controlled changeovers of supplies to existing electrical distribution switchboards. Upon completion of the transfer of supplies, the existing base build generators were isolated and removed from service and new low voltage generators were installed and commissioned prior to transfer back.

At the same time, we installed new UPS systems and cooling was increased with new 60Kw cooling units within the data centres and UPS rooms, switch rooms and static switch intelligent Power Distribution Units (PDUs).  These help to distribute electrical power in data centres and comprise transformers and circuit breakers which may be optionally monitored by controllers.  Each PDU is capable of supplying a large number of racks and rows of equipment either as floor standing or wall mounted, to suit requirements.

Upon completion of these works, the system was fully commissioned and was connected to the electrical distribution system to provide an A&B system for all major plant and equipment.  As part of the refurbishment, the data centre was completely rewired with A&B supplies to all IT cabinets provided for dual cord equipment.

Major projects of this type require careful planning with the client to ensure non interruption of power supply.  The main transfers of supplies and interconnections can only be carried out “out of hours” at set times to ensure minimal disruption to the client.

With the increasing requirement for large organisations to reduce their energy usage, combined with rising energy costs, it is little surprise that many data centres are looking to review their energy management systems.  With specialists m&e contractors able to advise on the integration of greener solutions, such as fresh air cooling systems and energy efficient lighting controls, this means data centre managers can clearly see the benefits of upgrading their systems.  Selection of equipment with a greater life expectancy is also an important part of this and this will also mean lower maintenance, as part of an overall sustainable approach.