Managing energy through measurement
By Jonathan Nally
Tuesday, 10 October, 2017
The old adage that you can’t manage what you can’t measure is nowhere more apt than in data centre energy consumption.
Energy management is one of the top priorities for data centre operators. Australia has roughly 50,000 data centres of all sizes, with around 100 of them considered to be large or enterprise-sized. Put together, they are responsible for around 4% of the nation’s electricity usage — 7.3 TWh in 2014 figures. In 2006–07 it was 2 to 3 TWh, and about 1.5% of total consumption.
It’s no wonder, then, that operators are keen to reduce their electricity consumption and concomitant power bills. One way to do that is to keep up with the latest storage, server and cooling technologies. Metronode’s data centres, for example, consumed 40 GWh of energy in 2016, with an associated CO2 emission generation of 37 kT. But those numbers would have been 56 GWh and 52 kT, had the company not employed BladeRoom technology and innovative designs.
According to the NABERS Energy standards, there are three relevant ratings for data centres: IT equipment, infrastructure and whole facility.
The IT equipment rating (according to NABERS’ Reducing the Energy Consumption of Data Centres document) “is for organisations who own or manage their IT equipment (including servers, storage devices, network equipment), who have no control over the data centre support services such as air conditioning, lighting and security, or only wish to measure their IT equipment. It benchmarks the greenhouse gas emissions associated with the energy consumed by the IT equipment and allows organisations to determine their equipment efficiency by comparing energy consumption with the capacity to compute and store data — the productive output.”
The infrastructure rating “is for data centre owners and managers. It allows them to determine their facility’s energy efficiency in supplying the infrastructure services to the IT equipment housed in the data centre. This rating is suitable for co-location centres where the operators do not have control of any tenant IT equipment but provide the cooling and power delivery systems.”
And the whole facility rating “combines both the IT Equipment and Infrastructure tools and is designed for organisations that both manage and occupy their data centre or where internal metering arrangements do not permit a separate IT Equipment or Infrastructure rating”.
Of course, the ability to achieve energy efficiency goals and comply with standards depends on reliable and accurate measurement of consumption. And that’s where metering technology comes in.
According to Ron Davis, managing director of energy management specialists SATEC (Australia), many operators assume the data received from their energy management meters is correct, whereas in his opinion a high percentage of readings may not have been correctly validated.
“Correct validation starts with ensuring the devices have been programmed properly — it’s garbage in, garbage out,” Davis said. “Beyond this, the validation process should ensure the readings are accurate with respect to power, vector relationships, phase angles and so on to ensure the meter and the building management system (BMS) and/or SCADA are both reading correctly with respect to one another. The biggest error made is that the majority of validation is completed only by checking AC current loads and not considering the errors where the AC power is being measured.”
Davis said the NABERS standards for data centres, as well as NMI-approved devices for sub-metering billing, have influenced metering and technology, with performance and KPI criteria enhanced. “The key benefits ensure the data made available is accurate and provides improved confidence in the information received,” he said.
“However, this is still heavily dependent on referring back to the programming and validation process,” he added. “These increased objectives add costs but also are designed for the integrity of the measurement data. ISO17025 certification under the NMI rules has added further performance metrics for meter manufacturers that are willing to make the investment.”
According to Davis, it is important that operators can have confidence not only in the data, but also that the data provides valuable information to confidently make informed decisions.
“Regardless of the KPI agenda, unless the data is accurate there can be no confidence with the information,” he said. “Furthermore, where data centres are involved with energy consumption for billing purposes, it is important that this ‘cash register’ is measuring correctly. This is where NMI-approved metering provides the confidence of measurement. Furthermore, meters used for NABERS that have been certified with ISO17025 can only add further confidence for data centre operators.”
So what type of metering devices and capabilities are we talking about?
“Generally for data centres, metering devices will include multiple applications such as NABERS ratings, NMI Energy Billing and devices to measure the quality of the incoming power to the facility,” Davis said. “These devices should, as a minimum, incorporate interval data logging, event logs and real-time clocks to ensure no data is lost in the event of a power loss and/or communication loss, ensuring data is retained.”
How important is validation in maintaining compliance with NABERS and other standards?
“Without correct validation processes, all metering data becomes irrelevant,” Davis said. “It is not uncommon for many data centre operators — including at industrial and commercial sites — to find that the data they have been recording/reading from the meter for many years is incorrect.
“Again, this breaks down to the process of the validation and programming procedure completed on commissioning — not only of the meter, but verifying correctly the interface to the BMS and/or SCADA.”
According to Davis, well-designed meters can last for many years, but technological changes and regulatory requirements can have significant effects. “Ensuring the metering deployed has functions and features to meet changes and challenges for the future is important,” he said.
Things to consider include warranties, accuracy, whether the meter has event logs, interval logs and a real-time clock, and whether it supports Ethernet communication.
“Ensuring these basic features are covered will help reduce meter churn for the future,” Davis said.
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