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Student Design Team Helps Save $2 Million a Year in Utility Costs
A MechSE student design team recently helped design a cooling system for the data center that will house the world's most powerful supercomputer. The novel cooling system is expected to save $2 million a year in utility costs. It will reduce the amount of chilled water needed to cool the computer's new data center through the use of on-site cooling towers. Cooling towers deliver water that is cooled by evaporation at a fraction of the cost of typical vapor-compression based chilled water systems. Like the cooling towers present in most chilled water systems, they require water and use electricity to run pumps and fans, yet they do not have the compressors that use significantly more power.
When it comes online in 2011, the Blue Waters petascale supercomputer at the University of Illinois is expected to be the most powerful computer dedicated to scientific research. It will also require lots of cooling power, as its many processors generate vast amounts of heat. While most supercomputing systems are air-cooled, the heat from Blue Waters will be cooled by the university's central chilled water system. Delivering chilled water directly to the processors will avoid the inefficiencies associated with the intermediate step of using chilled water to cool air, and is expected to reduce energy consumption by approximately 40 percent.
Economizers that involve cooling towers are currently used in data centers, but cooling water-cooled supercomputers on such a large scale is a new application. For this unique application, the most cost-effective design was not evident and required detailed modeling to determine. The larger the economizer system, which mainly consists of cooling towers, heat exchangers, pumps and piping, the greater the energy savings, but also the greater the initial cost. The optimum design lies where the sum of the initial and operating cost over the predicted life of the data center is a minimum, or has the least "lifecycle cost." So, while the Chicago-based engineering consulting firm hired to design the Blue Waters' data center designed the waterside economizer systems, the National Center for Supercomputing Applications (NCSA) challenged students at the College of Engineering to provide them with a second opinion. Four seniors in the Department of Mechanical Science and Engineering's senior design program answered the challenge. Their goal: To design a waterside economizer system with a cooling tower that would minimize life cycle costs.
"We could have easily have spent $20,000 to hire a firm to validate the design, but we thought it would be nice to get some of our own engineering students involved in helping us solve a real problem at their alma mater," said John Melchi, senior associate director, administration directorate at the National Center for Supercomputing Applications. "It was a great chance for undergraduates to work on such a national scale, visible project."
After identifying the design constraints, the senior design team worked under the guidance of senior design project coordinator Emad Jassim to develop their own design. The students used a model that they had developed to simulate the operation of multiple economizer designs involving different tower and component sizes on an hourly basis for an entire year using local weather data. They predicted the total annual chilled water reduction and total annual cooling cost associated with each design. They estimated the initial cost required to implement each design. Finally, they conducted a life-cycle cost analysis to determine which design is optimal (has the least lifecycle cost), and they estimated the payback period.
The students' analysis provided valuable guidance in the design process. It indicated that the annual operating cost of the system initially proposed by the consulting firm could be reduced by an additional $1 million. In the end, the design the students proposed was very similar to the one proposed by the consulting firm, which gave everyone involved a high degree of confidence that they had arrived at the optimal system. Once implemented, the cooling system is expected to reduce the annual chilled water usage substantially, saving NCSA a predicted $2 million a year in operating costs. At an estimated initial cost of just over $3 million, it is expected to pay for itself in approximately one and a half years.
"The cooling towers will save millions of dollars in operating costs in a relatively short time," according to facilities engineer Mark Washburn. "Emad Jassim's expertise and the results of the design project were used to push the design engineers to provide the best cooling tower system we can afford."
He explained that the university already uses cooling towers as part of the central chilled water system, but that the on-site system will help the data center to maximize the use of free cooling for a larger percentage of the year, as the required water temperature is much higher.
Stanley Berent, an alumnus who worked on the project and now works at Wash Construction, an engineering contract firm in Chicago, was inspired by both the project's size and scope. "It was very satisfying to know that our design could save the University so much money and that we had contributed to a petascale data center that will help scientists and engineers solve so many important problems," he said.
When it is finally in operation, Blue Waters will give scientists and engineers the capability to process one quadrillion calculations per second at a sustained rate That will make it possible for them to do science on scales never seen before and to work on problems that couldn't be solved previously, and it may very well lead to more accurate predictions in severe weather events, enhance pharmaceutical design, assist in the design of new materials, and help answer astrophysics questions.
"The project showed us how important energy is, because if you can save on power consumption, you can spend the money on other things," Berent said.
The experience Andrew Thacker gained from working on the design project relates directly to the work he does now as a project engineer at Conoco Phillips. "Everything we designed into the system is used in a refinery, so what I learned will be very beneficial if I ever have to install a cooling tower or heat exchanger," he said.
Jassim couldn't be more thrilled with the way the students took ownership of the project. "They not only optimized the design of the tower, but they also optimized the components," he said. "By doing so they demonstrated that mechanical engineers at Illinois are trained not just to produce a design, but to produce the best and most energy-efficient design-and that it's possible to tie real dollars to that skill."
The senior design team's success at validating the design for Blue Waters' cooling system has inspired a round of new energy-related projects on campus. "Next year, MechSE seniors will use their knowledge to reduce utility costs in the Mechanical Engineering Laboratory," Jassim said.