Data Centre Operations Blog

Air-side free-cooling – direct or indirect systems and their impact on PUE

There is a general perception that direct air systems are more cost efficient and hence the default option. However, providing the design incorporates good air segregation, recommended ASHRAE equipment environmental conditions and adiabatic cooling of the outdoor air, for most cities warmer than London, the indirect air systems are considerably more efficient than the direct air systems. This is because many more hours of free cooling can be achieved with adiabatic cooling without affecting the indoor conditions. Furthermore, zero-refrigeration in most of the world is possible with this solution. For cooler climates, direct systems are only marginally more efficient.

Often when data centre free cooling is discussed, people assume this means direct fresh air cooling. However, in climates warmer than London, indirect air systems are more efficient than direct air systems and can allow refrigeration to be eliminated and considerably reduce the electrical plant sizing requirements. Use of adiabatic evaporative cooling on the outdoor airstream allows free cooling to be achieved for many more hours in the year when there are hot, dry conditions. Further detail on the application for free cooling in data centres is available in our technical papers.

PUE move over for the LCA. Part 1: Environmental Impact of Data Centres

At Operational Intelligence we believe the data centre industry is starting to recognise that its focus must go beyond energy consumption. Single-issue metrics such as PUE only consider the operational phase, omitting impacts from other issues and during other stages a facilities lifetime. No single-metric has the capacity to capture fully the interlinked nature of the data centre system. Using single metrics is dangerous as improvement in one area can adversely affect a totally different area with the operator remaining oblivious. Using operational efficiency as a proxy for sustainability has to stop. Beth’s Whiteheads publication explains exactly why.

Complexity and The Human Element

Operational Intelligence was founded on the understanding that significant risk and energy reduction within the data center environment could only be achieved through an active engagement with operations teams across all disciplines. Risk and energy reduction may be the responsibility of an individual, but it can only be delivered if there is commitment from all stakeholders.

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Integrated Systems Test (IST) & Missed Opportunities

Based on feedback from Operational Intelligence Ltd’s Optimisation Workshops, David Cameron offers some feedback on the missed opportunity for knowledge transfer at the completion of the construction phase of a project and how the traditional structure of project teams is limiting the transfer of essential knowledge to the operations team. He claims that the industry is aware of this problem but perceives very little is being done to improve the situation due to the need for all stakeholders to work together.

Two modifications to the existing process are proposed:

  1. Prepare a Concept Design or Basis of Design document at the outset of the project and update this regularly throughout the design, construction and commissioning process. This should then form part of the handover documentation and will provide the reader a very clear overview of the purpose and limitations of the facility. This should also be used as the reference point for future upgrades and there should be an obligation on the operations team to keep it up to date.
  2. Change the final milestone from ‘project handover/completion’ to ‘design and construction knowledge transfer’ which provides a better description and focus. There are contractual definitions for Practical and Project Completion however provided that knowledge transfer is stated as a key deliverable of practical completion there should be no contradiction.

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Data Centre Air Segregation Efficiency

Data centres consumer large amounts of energy, most of all in IT equipment and cooling systems. They are also rapidly growing in size and numbers. Inefficient air segregation can cost facilities a lot of energy through wastage and increases risk of downtime. Previously, it has been difficult to quantify the efficiency of air separation.

Thus, we introduce a metric is that helps data centre operators calculate total air segregation efficiency. The tool is robust and scalable. It does not need any complicated software or an abundance of data. What you choose to do with the metric is under your control and its validity relies on the accuracy of your measurements. This is vital. However, the tool is extremely powerful and can provide the platform from which many improvements can be identified. To read on download the latest technical paper: Please follow the link

Data Centre Energy Efficiency – How We Saved $1.7 Million

Data centres continue to grow in size, number and consumption; and as they do, approaches to their design have evolved. Low energy operation has become a design requirement, and the focus has shifted away from highly redundant mechanical and electrical infrastructure topologies to include both criteria. Many new data centre designs have a target PUE of 1.2 or below, whereas legacy facilities might achieve of PUE of 2.0 or above, and the industry has become more aware of its environmental impact. With raised temperatures and improved air management, free cooling has become possible across the globe, increasing the potential for zero refrigeration.

This case study looks at the efforts made by a global financial services firm in their legacy facility to reduce PUE from 2.29 to 1.49, and their annual electricity bill by $1.7M.

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Zero Refrigeration in the USA

In many USA climates 100% free cooling is possible. Significant operational and capital cost savings can be realised. With segregation of hot and cold air streams by hot aisle, cold aisle or exhaust containment systems, zero refrigeration is possible. As temperatures get hotter, the benefits of indirect cooling systems are greater. If you’re interested in where, why and how zero refrigeration in the USA is possible, click: link

Meeting Climate Change Targets in the UK

Dr Beth Whitehead, Sustainability Engineer at OI, describes how facilities can work towards reducing their non-IT energy consumption by 30%.

Four years ago, the process began to establish a climate change agreement (CCA) for data centres. The agreement, which enables continued sector growth, provides a reduction in CCL (climate change levy) taxes and exemption from the CRC (climate reduction commitment) in return for efficient energy consumption. Achievement of this milestone is recognition that the government understands the importance of the data centre sector to the UK economy.

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