Sept. 28, 2020 — The US Department of Energy’s (DOE’s) Oak Ridge National Laboratory (ORNL) is poised to deliver Frontier, its first exascale supercomputer, next year. Exascale systems are capable of operating at 1 quintillion calculations per second, requiring a significant amount of power and generating substantial amounts of heat.
Before the engineers working on the Frontier supercomputer could bring new hardware into the building that used to house the Oak Ridge Leadership Computing Facility’s (OLCF’s) Cray XK7 Titan supercomputer, they first had to install a 2.5-mile-long power line from one of the laboratory’s nearby electrical substations all the way to the computer room.
“We put in new power poles and ran additional electrical feeders from the substation,” said Justin Whitt, project director for Frontier at the OLCF, a DOE Office of Science User Facility at ORNL. “We needed to provide about 40 megawatts of power and cooling to the Frontier data center.”
The project began last fall with design work and a field survey of the entire right of way—the path of the transmission line—with multiple divisions in ORNL to ensure that wildlife and habitat wouldn’t be impacted in the construction process. More than a dozen species of bats reside on the Oak Ridge Reservation today, including an endangered Indiana bat. Most of the bats in Tennessee spend their winters in Tennessee caves and migrate to warmer, forested habitats—like those at the laboratory—in the summer. This restricts construction in the area during the summer months.
ORNL plant ecologist Jamie Herold, technical professional Kitty McCracken of the laboratory’s Environmental Sciences Division, and clean water act compliance specialist Todd North in the Environmental Protection Services Division all took part in the survey.
After the environmental issues were identified and permits were issued, the Roads and Grounds Crew led by ORNL’s Matt Powell and Zackary Moore of the Logistical Services Division began carving out roads to prepare for the power line installation. With fencing to be torn down, trees to be cleared, gravel to be spread, and a ridge and lake to be crossed, the project would be no easy feat.
“Roads and Grounds works with our environmental groups and understands the environmental rules and regulations,” said Jack Wilkinson, a project manager in ORNL’s Laboratory Modernization Division. “November to March is the only time they have to actually clear trees because the bats migrate here in the summer.”
After the roads were installed, Wright Construction completed an approvals process that involved the Tennessee Valley Authority, the Tennessee Department of Environment & Conservation, and the Army Corps of Engineers to ensure environmental and safety regulations were followed during the installation. Then, Wilkinson’s team began the daunting task of installing the power line, beginning at the substation. The project was massive.
“Some of the rolls of wire had about 8,000 feet on them and weighed around 8,800 pounds,” Wilkinson said. “We had to run 12 conductors a total of 2.5 miles for about 160,000 feet of large wire overhead. There were about 50 employees on the project scattered throughout the area at any given time.”
The project also required staff to dig 10-foot-deep trenches in the substation and under roads to install banks of electrical conduit, and the rain the area experienced at the beginning of the year proved to be one of the biggest challenges, Wilkinson said.
“In January and February, we had at least double the amount of rain we normally do,” Wilkinson said. “We needed dirt to backfill these trenches, but since it was wet, we couldn’t pack it down enough, so we had to fill the trenches with gravel instead.” Wilkinson applauded the determination of the construction workers in completing the project. The team, overseen by ORNL field construction manager Ken Brown, consistently persevered through muddy, cold, and otherwise unfavorable outdoor conditions to meet project deadlines.
The end result was more than 2.5 miles of 13.8-kilovolt electrical cables running along 84 new power poles down Ramsey Drive and Melton Valley Drive and across Haw Ridge.
The design of the lines takes into account snowfall, wind conditions, temperature conditions, and the rate of expansion, resulting in the ideal amount of sag and tension on the lines.
Multiple access pads across Haw Ridge link the lines straight from Melton Valley Drive to White Oak Avenue and the 5600-5700-5800 complex where the OLCF’s supercomputers live.
Next on the team’s agenda is the transformers that will be installed just outside of the Frontier data center to step down the power. A team will then further distribute the electricity inside of the Frontier data center itself by making connections available for the new system.
Throughout the project, safety was at the core of the team’s work, said Justin Whitt. Over time, the teams working on the project have developed processes that use electromagnetic scanning and ground-penetrating radar to determine the locations of electrical conduit underneath the floors of buildings.
“You don’t want to be chipping away at the floor and hit a power line beneath,” Whitt said. “The ‘as-built’ drawings should reflect every power line that’s laid, but from a safety standpoint, we want to be sure there’s no existing electrical conduit in the area we are about to make penetrations into. If there is any doubt, we have to shut off power to the area, which can be disruptive inside an operating building.”
In addition to the power line installation, a team led by ORNL high-performance computing mechanical engineer David Grant also built a new mechanical plant that will provide cooling to the Frontier data center. The team converted existing laboratory space into mechanical space and ran steel piping from the cooling plant to the data center.
Frontier’s cooling system pushes the boundaries of warm water cooling to save the laboratory on operating costs and is expected to be 30 to 40 percent more efficient than the cooling system for Summit, the OLCF’s flagship supercomputer. Because the Frontier cooling system could face load swings of 10 megawatts or larger within minutes, the team working on the project designed it to anticipate near-term heat-load swings. When not in use, the cooling system capacity will cool other data center loads.
Source: Rachel Harken, ORNL