– Mark Silnes, Marketing Manager-Cooling, Emerson Network Power, Liebert Services, says:
In my previous two (1, 2) articles, I discussed the importance of taking a holistic approach to making cooling system improvements, instead of making disparate adjustments. This approach allows you to make changes that complement each other while improving overall performance, availability and capacity. Ultimately, it saves money, achieves better return on investment, and improves decision making for future expansion.
This holistic approach, highlighted in “Thermal Management: Realizing Efficiency without Compromising Availability,” starts with getting a professional cooling assessment to find out the actual conditions in your data center. Another element is varying the cooling unit fan speed by employing electrically commutated (EC) fan or variable speed drives (VSD), as discussed in “Implementing Fan Technology for Greater Energy Efficiency.”
In this article, we look at a third element: using optimized intelligent controls to bring high-level supervision to multiple cooling units. Additionally, I’ll highlight how coupling intelligent controls with fan technology results in greater energy efficiency than using either intelligent controls or variable speed fans alone. In fact, pairing the two will provide the biggest reduction in cooling system energy consumption for most data centers.
Integrating intelligent control capabilities into data center cooling allows up to 32 units to work together as a single system to optimize room environments and drive data center infrastructure performance. A unified cooling environment can improve efficiency by 28 to 40 percent, depending on data center specifications and existing equipment.
Intelligent controls let you shift from cooling control based on return air temperature to control based on conditions at the servers, which is essential to optimizing efficiency. The controls ensure the optimum combination of compressor/chiller capacity and airflow, and they also often allow temperatures in the cold aisle to be raised closer to the safe operating threshold recommended by American Society of Heating, Refrigerating and Air-Conditioning Engineers (max 80.5 degrees Fahrenheit; 27 degrees Celsius) for class A1-A4 data centers. According to an Emerson Network Power study, a 10 degree Fahrenheit (5.6 degree Celsius) increase in cold-aisle temperature can generate a 20 percent reduction in cooling system energy usage.
Additionally, an advanced system such as the Liebert® iCOM™ control can ensure all cooling fan technology works together to provide optimum efficiency and shift workload to units operating at peak efficiency while preventing units in different locations from working at cross-purposes. Without this type of system, a unit in one area of the data center may add humidity to the room at the same time another unit is extracting humidity from the room (unit “fighting”). The control system provides visibility into conditions across the room and the intelligence to determine whether humidification, dehumidification or no action is required to maintain conditions at target levels and match airflow to the load. In fact, Liebert iCOM controls offer multiple teamwork modes for different data center sizes and operating conditions.
Intelligent controls allow you to recover hours of energy that would be wasted due to unit “fighting” which amounts to significant annual savings. The energy efficiency case study below represents a customer with 32 cooling units operating as a single zone by utilizing the Liebert iCOM control teamwork mode (assuming $.10/kW energy cost).
% of Operating Time with Unit Fighting
Coupling Intelligent Controls with Variable Speed Fans
The Liebert iCOM control system featured on Liebert perimeter or row-based precision cooling products is available with Optimized Aisle Control algorithms to provide enhanced airflow management and cost savings to data centers with row-based infrastructures. Liebert iCOM with Optimized Aisle Control “decouples” the compressor and fan operation. These components operate independently to match the IT load and the airflow requirements but are coordinated to maximize the efficiency of each component. Matching operation to room requirements results in warmer air returning to the cooling units—allowing the fan and the mechanical cooling to operate more efficiently, which eliminates overcooling and saves energy.
Each unit within the Liebert iCOM system operates both independently and as a team providing optimal control and redundancy. If communication is ever lost, the units will operate independently to cool the heat load as efficiently as possible.
Each controller supports multiple rack temperature sensors, as well as sensors for supply air temperature, return temperature and humidity in order to optimize operation based on user-defined temperature and humidity targets. Liebert iCOM leverages the variable capacity fans and compressors in Liebert cooling systems, which allows the units to dynamically adjust capacity based on changing conditions and control airflow based on conditions at the rack.
Cooling Control Optimization
Today’s cooling units are designed to be energy efficient. But to make sure you get the best performance from a cooling unit, it must be optimized to the load and room conditions once it’s been installed. A technician who is data-center focused and factory-trained by the original equipment manufacturer knows the technology and works with it every day. While some service providers may have the knowledge required to install precision cooling equipment, they do not necessarily have the expertise needed to assure optimum performance of these systems after they are installed.
The first step in cooling control optimization is a consultation with the technician, who needs to understand the critical infrastructure goals and priorities. He then will walk through the data center with you to review various cooling controls and make recommendations based on what he finds. The technician will also describe how recommended changes will affect equipment performance and listen to your feedback before making changes. Specific cooling controls that may be optimized, depending on your cooling system, include:
- Temperature and humidity set points/settings – IT systems are critically sensitive to extreme variations in temperature and humidity. High heat or humidity can cause failure, degrade performance and shorten equipment life. Too low humidity can cause static electricity to build up and discharge (electrostatic discharge), which can shut down electronic equipment, possibly damaging it and/or causing data loss.
- Networking and teamwork mode controls – Rising equipment densities have increased diversity within the data center. Rack densities are rarely uniform across a facility, which can create cooling inefficiencies. But this issue is resolved by control coordination and optimization.
- Optimized Aisle Control mode – A unit-to-unit network set to operate in Optimized Aisle Control mode can utilize a teamwork mode to share sensory data and provide coordinated cooling and humidity control among cooling units.
It takes knowledge and time to set up the most advanced features of modern cooling systems, and while it’s advantageous to optimize cooling controls at any time, working with a factory-trained technician when new equipment is installed may be the best choice.
Like control optimization, you’ve learned throughout this series how each change made to a data center cooling infrastructure provides incremental energy and cost saves. However, I hope you’ve also learned that a robust and holistic approach is ideal.
For example, variable speed fans improve the energy consumption of just the fan. However, integrating variable speed fans into the controller is key to ensuring the best performance of the fan itself, individual units, and the data center as a whole. This integration ensures ideal cooling with the least energy usage by the fans and compressors. Adding in teamwork functionality and optimizing other cooling control settings then allows you to get the most from your entire infrastructure—maximizing efficiency and reducing costs.