Data centers have been trying to become more energy efficient for 20 years. They continue to look for ways to reduce energy usage, cool more effectively, and reduce operating costs. The latest frontier in this never-ending quest is waste heat recovery and reuse.
In data centers, the amount of waste heat will only increase as AI applications are added and the use of liquid cooling increases. This growing trend highlights the need for data centers to adopt waste heat reuse solutions to not only increase energy efficiency but also reduce environmental impact and operational costs.Top of form
“Isolating heat from the chips to the facility remains difficult,” said Peter de Bock, program director of the ARPA-E COOLERCHIPS program.
Extracting waste heat outside the facility is one approach, but it is much more efficient and environmentally friendly to use waste heat to generate electricity, steam, heat, and even cool. This is an active area of research.
“Facilities can reduce their cost burden and carbon footprint by finding ways to harness waste heat,” said Kyle Mangini, who manages all laboratory and mechanical systems at the Amherst College Science Center. Masu.
Multifunctional campus
Brian Rener, mission critical leader at SmithGroup, believes there are many opportunities for sustainability and efficiency when data centers are located in multifunctional buildings or campuses. Because data centers require continuous cooling, servers and other equipment emit large amounts of waste heat. These waste heat can be utilized in various ways to reduce overall energy consumption and further reduce power usage efficiency (PUE).
“With data center power consumption expected to double in the coming years, most data centers have the option of relocating to more northerly locations to take advantage of cooler outside air as a way to improve sustainability. There is no,” Renner said. . “Alternatively, it can be co-located in mixed-use environments on campus or further integrated into local communities to derive value from waste heat.”
build smarter
In the movie Field of Dreams, Ray Kinsella (Kevin Costner) is told, “If you build it, they will come.” He did it in the middle of a cornfield in Iowa. While it may have worked in the movie, Renner doesn't think it's the best location for a data center. Such locations make it difficult to maximize the value of waste heat. Instead, his advice is to explore the larger community and make data centers part of a broader energy solution.
Renner backs up his claim by citing data from the U.S. Energy Information Administration (EIA) that shows heating is the largest single energy end use in commercial buildings at 32%. The cooling was only 9%, but that number would be even higher in southern states. One large building consumes 1 MW for heating. 25 city blocks require 10 MW, and an 8,500,000 square foot commercial facility requires 100 MW for heating alone.
Next, consider data center density. High-performance computing (HPC) and AI are increasing rack densities to 100 kW and beyond. The aisles are packed with more powerful processors than ever before.
“All processors are getting bigger and more powerful,” said Shen Wang, principal analyst at Omdia. “Since 2000, processor power consumption has increased 4.6 times.”
This certainly causes serious problems in terms of power and cooling. But opportunities also arise because chips and servers emit large amounts of hot waste heat.
University campus cooling
The Milwaukee School of Technology provides a useful example of waste heat reuse. A computer science building was added with a supercomputer inside it known as Rosie. This her Nvidia GPU-accelerated supercomputer helps students learn her AI, drones, robotics, and self-driving cars. The supercomputer room takes up only 1,500 square feet of the 65,000 square foot building, but consumes more than 60 percent of its energy. Therefore, the system needed to be seamlessly integrated into the building and mechanical/electrical/piping infrastructure. Data centers are designed with N+1 redundancy, allowing them to remain functional even in the event of a single component failure thanks to multiple backup generators and cooling units.
The engineering team developed a symbiotic relationship between the academic building's energy system and supercomputer system. For example, computer labs and academic buildings use the same cooling system during the summer. During the summer, the facility's cold water return line is used to supply the data center. By increasing the return of chilled water, the overall cooling efficiency of the building has been improved. During the winter months, when mechanical cooling is no longer required in academic buildings, the computer facilities utilize cold outside air through dedicated air-cooled rooftop condensers and integrated free cooling circuits.
“Harnessing waste heat is key to increasing the efficiency of data centers and buildings,” said Jamison Caldwell, Principal Mechanical Engineer at Smith Group.
In addition to finding ways to harness waste heat from hot aisles, he pointed out that liquid cooling equipment also emits radiant heat. He is working on the energy reuse factor, which is calculated as a function of the recycled energy relative to the total energy consumed.
“There are many opportunities to utilize waste heat at the campus level,” Caldwell said.
NREL Energy Recovery Loop
The National Renewable Energy Laboratory (NREL) is building an Energy Systems Integration Facility (ESIF) designed to match the heating needs of laboratories and offices with a supercomputer-based data center, increasing overall building energy efficiency. Did. It has achieved a PUE of 1.04, making it one of the most efficient data centers in the world.
“The office is heated 100% by waste heat reuse, and water usage has been cut in half,” Caldwell said. “If you suddenly need more heat, you can use campus steam.”
This is made possible thanks to an energy recovery water loop that spans the campus' heating and cooling systems, supercomputing systems, and legacy IT systems, collecting waste heat from both liquid and air cooling systems. Caldwell characterized this as building-level energy exchange.
“Liquid cooling allows for higher grade hot water heat recovery,” he said.
incremental gain
Liquid cooling can make a huge difference in data center cooling efficiency, resulting in significant reductions in PUE. Or at least prevent PUE from increasing as rack density increases. However, Jason Mattson, Vice President of Customer Solutions Architecture at Iceotope, said waste in a variety of areas, including lack of hot air containment, missing blanking panels, and failure to replace power consumption, led to potential losses from liquid cooling. He pointed out that significant profits could be wasted. fans etc.
“Most data centers have a lot of waste that can be eliminated,” Mattson says.