I am continually shocked that CIOs, data center design teams, infrastructure managers, and data center operators ignore the lack of cooling control systems in data centers. Data centers are mission critical facilities that require 100% uptime. Their cooling infrastructure requires continuous vigilant surveillance.
The cooling infrastructure for buildings, which are not mission critical facilities and can afford an hour or two of downtime, has been developed to monitor, control, and alarm when conditions become sub-optimal. Compared to the sophistication of building cooling infrastructure, data center cooling control systems are practically non-existent. In other words, if building cooling control systems just graduated with a PhD, data center cooling control systems would be stuffing envelopes as a college intern.
The PhD (Buildings)
The purpose of providing a Heating Ventilation and Air Conditioning (HVAC) system in a building is to condition the internal environment so that the occupants are comfortable. The complexity of HVAC systems varies from building to building, and that variability usually depends on location. In San Francisco, opening vents and ventilating outside air through the building is enough to accomplish tenant comfort throughout most of the year. Special equipment for heating or cooling is not always required.
In the northeast however, significant heating is required during the frigid winter months while significant cooling is required during the warm humid summer months. The equipment required for heating and cooling usually resides within a building and is controlled based on those wall-mounted thermostats we’re all familiar with. Providing comfort cooling for tenants is not easy. First of all, we all want to set our own temperature (hence the wall-mounted thermostats). You can’t just set the entire building to 70°F, you have to give control to each person in each space. Secondly, conditions change throughout the day as the sun moves from one side of the building to the other or as people cram in a conference room with a projector and 10 laptops. The cooling loads are constantly changing in a building and the HVAC equipment must keep up. And, the outdoor weather changes hour by hour and season to season. A decision needs to be made on when to cool or heat and how much to cool or heat at every moment in time. Managing that decision-making process is too complex for a single human operator. Luckily, the HVAC industry has made enormous technological strides over the past 20 years in control systems that automate this process. Siemens, Johnson Controls, and Honeywell are the big control vendors in the industry. They have been very successful at creating control systems that automatically and dynamically manage the heating and cooling equipment in a building to ensure tenant comfort is adequate at all times. These controls systems not only meet the goal of providing tenant comfort, but they do so utilizing as little energy as possible. Quite an amazing accomplishment. Let’s turn to data centers now and make a comparison.
The Intern (Data Centers)
The purpose of providing HVAC systems in data centers is to remove the heat produced by IT equipment. Compared with buildings, the HVAC requirements in data centers are actually quite a bit simpler for the following reasons:
1. Data centers do not require heating, just cooling.
2. Most data centers do not need individual temperature control like people do in buildings. Its ok to condition the entire facility to 75°F
3. The cooling load in a data center is constant compared to drastic ups and downs throughout the day evident in buildings.
So why, given the relative complexity of control systems in buildings versus data centers, do so few data center operators optimize for cooling control? The reason is because the number one responsibility of a data center operator is to make sure the IT equipment has 0% downtime. A minute of downtown could cost them their jobs. As expected, they err on the side of safety and leave all cooling units on all the time. But as data centers expand, and more IT equipment is loaded into the same footprint, managing cooling is becoming a necessity….a necessity that requires assistance from automated and dynamic control that knows exactly which cooling units to turn on and off without affecting uptime. While cooling control for data centers is simpler than it is for buildings, it does come with its own set of challenges. Come back for Part 2 on cooling control to see what those challenge are and how to overcome them.