Feature sponsored by Test & measurement


variability, so it is important that there are sufficient numbers of temperature sensors to ensure that all servers are monitored. Some servers may be close to a cooling unit and others may be further away; some may be at the bottom of a rack, and others higher up, so there is potential for three- dimensional variability. In addition to a sufficient number of sensors, it is also therefore important for air flow and cooling to be optimally distributed throughout the server room. By a combination of proper design and monitoring, it is possible to efficiently control cooling and air flow to meet the required specification.


In order to evaluate the effects of different variables on average annual energy usage, Munters has modelled their system operating with three different control regimes at three different locations; each with a one-megawatt ITE load data centre (see image below):


The base case scenario has a design supply temperature of 24°C, and a return temperature of 35°C (delta-T = 11°C).


In the second case, the supply and return temperatures were lowered by 1°C (delta-T maintained).


In the third case, just the return temperature was lowered by 1°C (delta-T reduced).


The results showed lower energy usage in all three scenarios at the milder climate location. Scenario #2 showed one to two per cent additional energy usage by lowering the supply and return temperatures by just one degree. Scenario #3 showed the most significant increase in energy usage; by lowering the return temperature by just 1°C (and thereby the delta-T), energy usage increased by eight to nine per cent in all three locations. This large effect from a small deviation in temperature highlights the importance of both delta-T and sensor accuracy. Whatever cooling methods are employed, it is crucially important to control HVAC processes and indoor conditions in a reliable manner. To achieve this, data centre managers need to be able to depend on continuous accurate measurements,


because the control loop can only be as good as the measurements. For this reason, high quality sensors are enablers of efficiently controlled HVAC processes and a stable indoor environment. However, sensor specification at the time of installation is not necessarily an indicator of long- term performance reliability. The real value of a sensor is derived over its entire lifecycle, because frequent requirements for maintenance can be costly, and as outlined in the Munters models, even small deviations in accuracy can lead to inflated energy costs.


In most cases, the value of the data in the IT


infrastructure is extremely high, and often mission-critical, so it would make no sense to deploy low-cost sensors if that results in high maintenance costs, or risks to high-value data. Users should therefore seek durable measurement devices that are able to deliver reliable, stable readings in the long run, because it is that lifelong reliability that really matters. A focus on the accuracy, reliability and stability of measurement devices has been a key brand value for Vaisala since its foundation over 86 years ago. These features are therefore fundamental components of the design remit for every Vaisala product. Demonstrating the advantages of these features, Vaisala sensors have been operating on the planet Mars for over eight years, delivering problem-free data in harsh conditions aboard NASA’s Curiosity rover, and more recently on the Perseverance rover. Data centres represent a less challenging environment than outer space, but reliable sensors are equally important given the essential service that data centres provide to businesses, economies and societies world-wide.


FACTORS AFFECTING THE CHOICE OF SENSOR 1. Reliability


The accuracy of the sensor at the point of installation is obviously important, but it is vital that the sensor remains accurate in the long- term delivering stable readings. Given the high value of data centres, and frequently their remote location, the lifetime of the transmitters should be well above the norm. The manufacturer should therefore have experience


in the sector, coupled with a reputation for reliable measurement in critical environments. Traceable calibration certificates provide assurance that sensors were performing correctly before leaving the factory, and proven reliability means that this level of accuracy can be maintained in the long-term.


2. Maintenance


Sensors with a high maintenance requirement should be avoided; not just because of the costs involved, but also because such sensors incur higher risks of failure. In addition, sensors that drift or lose accuracy can result in enormous energy costs, as explained above. The high levels of uptime required by data centres means that any maintenance operations for monitoring equipment should not disturb the operation of the data centre. Consequently, instruments such as Vaisala’s with exchangeable measurement probes or modules are advantageous; not least because they allow sensors to be removed and calibrated off-line. Importantly, if a measurement probe or module is exchanged, the calibration certificate should also be updated. Ideally, it should be possible to undertake maintenance operations on-site with tools from the instrument provider, and this work should be undertaken as part of a scheduled maintenance program.


3. Sustainability From a sensor perspective, the latest technologies allow users to upgrade just the measurement part of a sensor instead of changing or scrapping the whole transmitter; thereby helping to avoid unnecessary waste.


The environmental and sustainability credentials of suppliers should be taken into consideration when making buying decisions. This enables sustainability to cascade down supply chains and creates a driver for all businesses, large or small. Sustainability is at the heart of both Munters


and Vaisala. Munters, for example, has over 1.5 gigawatts of data centre cooling equipment installed globally: delivering energy savings equivalent to two percent of Sweden’s annual energy consumption. Vaisala was recently listed in the Financial Times’ Top 5 European Climate Leaders 2022. The list includes European companies that achieved the greatest reduction in their greenhouse gas emissions between 2015 and 2020.


SUMMARY With critical data worth billions of dollars being processed and stored at data centres, power- hungry servers must be maintained in ideal temperature and humidity conditions to prevent downtime. At the same time, there are urgent demands for lower greenhouse gas emissions, improved energy efficiency, lower energy costs and better PUE measures; all at a time of spiraling energy costs. This ‘perfect storm’ of drivers means that the accurate control and optimisation of HVAC processes is extremely important.


Vaisala 30 www.vaisala.com March 2023 Instrumentation Monthly


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82