The Tower Of Cool Goes To School
One of the areas that RTKL specializes in is data center design. When two RTKL employees in Baltimore started seeing the densities of computer equipment in data centers appear to outstrip the ability of the conventional design to cool the equipment, they began thinking of better ways to keep the equipment cool.
Their brainstorming led to the creation of the "Tower of Cool" solution, whose concept is really quite simple: deliver air directly to the cabinet and extract the heat from the cabinet without using the room as a cooling medium for the equipment. The concept was especially appealing to researchers at the University of Maryland, who recently decided to work in conjunction with RTKL in order to test the patented Tower of Cool data center cooling technology.
Brainstorming BreakthroughSteve Spinazzola, P.E. and Dennis Peltz, P.E. are the two RTKL employees who worked together to come up with the Tower of Cool. In January 2000, Spinazzola and Peltz started talking about a better way to cool equipment in data centers. They were spurred on by the fact that data center design had not changed appreciably in the last 30 years, but that computer equipment had changed drastically.
As Spinazzola notes, "Cooling the entire room to cool the equipment does not remove the heat from the computer cabinets fast enough. Today's computers dissipate heat at up to ten times faster than what was produced just three years ago. The result is persistent hot spots and equipment failure."
Both Spinazzola and Peltz had backgrounds in the design of lab space, and they started thinking about how in a lab, fume hoods are used to collect heat and then exhaust it outside. That thought process led to a whole series of questions and answers, culminating in the realization that it might be possible to cool the data center equipment itself rather than the whole room in which the equipment is housed. Based on that concept, Spinazzola and Peltz submitted their first Tower of Cool patent application in March 2000.
The Tower of Cool solution does not do away entirely with the existing data center design; in fact, it basically improves upon what's already in place. Most data centers are usually designed in the same fashion; that is, all electronic equipment is placed in racks or cabinets sitting on a raised floor. The raised floor usually acts as a supply plenum to deliver conditioned air into the room to cool the equipment. Air conditioning units also sit on the raised floor and provide cool air into the raised floor plenum to cool the room. The units' return air is taken directly from the room.
The Tower of Cool is basically a cabinet in which there are three fans at the base and three fans at the top. The three fans at the base extract the cold air from the raised floor plenum and direct the air across the inlets to the servers. A back door is designed to extract the heat from the equipment uniformly. The three fans at the top of the cabinet in the back blow the hot air up into the return ceiling plenum.
Spinazzola notes that there are several ways to discharge the heat, including putting return grilles in the ceiling above the cabinets' discharge fans. "In data center design, there are process cooling units that return air from the room. In our applications, you actually sleeve the unit to the ceiling so the room is not the supply or return path anymore. The underfloor raised floor plenum is the supply duct, the ceiling is the return duct, and the space is just where you walk to service the equipment."
From Patent to PrototypeSince RTKL is a design firm, it had no ability to make the Tower of Cool, so a decision was made to partner with a company called Wright Line, which manufactures enclosures for computer equipment. Wright Line liked the product and took it from an idea to a prototype in January 2001.
That prototype was tested at three customer sites, and the results were very encouraging. "The whole concept is cool the equipment, not the room, and that results in a substantial increase in the efficiency of the air conditioning system. The savings are in the operating costs," said Spinazzola.
Spinazzola's calculations show that using the Tower of Cool can reduce the airflow requirements of a data center by 50%. "If you reduce the airflow by 50%, you double the efficiency of the cooling equipment, then you can reduce the fan horsepower by 50%," Spinazzola said, which is significant because a data center's fan horsepower is 28% to 50% of the total cooling plant energy. "If you can reduce the fans by half," Spinazzola continues, "you're looking at a 14% to 25% reduction in the cooling plant load, which results in about a 6% savings on total data center operation. That's the least amount that will be saved."
Saving energy is extremely important to data centers, because they are notoriously expensive to operate. When Spinazzola talks to data center staff about what concerns they have, the answers usually come in three forms:
- We can't afford to build the facility because it's so expensive;
- We can't afford to operate it; or,
- We're really concerned about keeping our equipment online because we've got chronic overheating problems.
"The old approach of moving enough air through the space to get the heat out is extremely inefficient," said Spinazzola. "The inefficiency comes from the fact that most of the air does not go through and extract heat from the equipment; it gets recirculated back to the air conditioning unit without doing any work. What we're doing is reducing the amount of air required by half. And it's directed: it goes in once, out once, and back. We've also eliminated the thermal issues inside the cabinet, which affect the performance of the equipment."
In fact, Spinazzola's research showed that elevated temperatures can actually decrease the lifespan of servers and disk drives. He found that if it's possible to maintain computing equipment at lower constant temperatures, they last longer, and hence are more reliable.
But the one thing that amazed Spinazzola most during the research process was that the Tower of Cool can effectively double the capacity of any chilled water unit. "We realized that every chilled water cooling unit in America that's made or already installed will automatically double its capacity when air is returned at 95 degrees F. That was a major realization."
Change in the HVAC industry is never usually embraced immediately, so it's not surprising that data centers aren't exactly banging down the door to install Tower of Cool equipment in their facilities. In fact, the biggest hurdle Spinazzola has right now is telling data center operators all over the United States that what they've been doing for the last 30 years doesn't work anymore. "It's like telling kids there's no Santa Claus. They've got this multimillion dollar investment in cooling technology, and we're telling them we've hit the wall."
The Tower of Cool can be retrofitted into existing data centers on a cabinet-by-cabinet basis, so it can be phased in over time. Spinazzola said he's starting to see a trend in which customers install the Tower of Cool when they purchase new equipment. Right now, RTKL is the only design firm capable of designing around the Tower of Cool system; however, Wright Line is offering to educate other design professionals about how to design a Tower of Cool system.
Off for ResearchOne entity that definitely was interested in Tower of Cool was the University of Maryland's Industrial Partnerships Program (MIPS). The competitive program, which seeks to nurture Maryland industrial growth through the expedition of research and development and commercialization of technology-driven products and/or processes, provides grantees with a faculty research partner and up to $100,000 a year in matching funds.
RTKL was awarded a $30,000 research grant in October 2002 and is working on the project with Dr. Reinhard Radermacher from the Department of Mechanical Engineering at the University of Maryland, College Park. Radermacher has conducted heat transfer measurements for a wide range of fluids under a wide range of conditions and operates jointly with his colleagues at the Center for Environmental Energy Engineering.
"This project is part of a series of projects that are being conducted jointly with the Georgia Institute of Technology and a number of companies within the framework of a research consortium named CEETHERM (Consortium for Energy Efficient Thermal Management) with an emphasis on least-energy data centers," said Radermacher.
He notes that the R&D project will demonstrate the performance potential of the Tower of Cool. In order to analyze the equipment, a prototype unit has been installed in a University of Maryland data center for testing. It is equipped with simulated servers of variable heat loads and with a number of probes to measure temperatures, airflow distribution, and overall system performance.
The Tower of Cool will be tested for approximately six months, at which time a final report will be issued by researchers. "It is too early to say what information our final report will provide, since the data are not yet measured," said Radermacher. "But it will contain a thorough assessment of the performance envelope of the Tower of Cool, and possibly application suggestions."ES
For more information on the Tower of Cool, download the white paper found at: www.rtkl.com/services/applied_technology/bluequarkfinal.pdf.
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