Case study: children’s hospital designed for speedy recoveries and power reliability
The bright, playful façade of Alberta Children’s Hospital in Calgary looks like a random stack of colored building blocks—and that’s how the kids who had a hand in its design wanted it. And even though the kids didn't design the standby power system, it is every bit as innovative.
The bright, playful fa%%CBOTTMDT%%ade of Alberta Children’s Hospital in Calgary looks like a random stack of colored building blocks—and that’s how the kids who had a hand in its design wanted it. The colorful exterior represents the goal of the new hospital—responding to children’s needs. This includes the 3.5-MW electrical needs of the 133-bed, 750,000-sq.-ft hospital.
During the early design stages of the hospital, which opened in September 2006, architects asked young patients what they thought a hospital for kids should look like. From these early concepts, the hospital is designed to be all about the children who go there for treatment. With a focus on family-centered care, the hospital includes sleeping facilities for parents in each patient room, a pet visitation room and healing gardens. However, most patients are treated on an outpatient basis and visit the hospital’s diagnosis, assessment and treatment clinics. This clinic-based program has been used as a worldwide model for outpatient care.
Building a hospital specifically for children drove and effected every part of the design. “Everyone on the design and construction team agreed that intangible factors—not just price—were important, because it is a children’s hospital,” said Gerry Stebnicki, electrical design team leader with Stebnicki + Partners in Calgary. “This made the whole approach unique. We sent a request for proposal to generator manufacturers stating our essential performance requirements rather than a complete design; all major components of the hospital were chosen that way. We chose … the best value of all the tendered proposals. Once they were chosen, they participated in the budget control and design decisions, working in concert with the rest of the group to make it happen. That’s a big reason why the project was so successful.”
Redundancy equals reliability
One example of the planning team’s quality-driven focus was the high reliability designed into the standby power system. The team created N+1 redundancy at all levels. “Although we initially recommended two 2-MW generators to serve the hospital’s 3.5-MW total load,” said Stebnicki, “hospital officials wanted to be able to run at full load even if one generator was down—so there are three generators.”
The three generators are housed in a building 1,312 ft from the main building to minimize noise and vibration in the hospital, allow ground-level access to the generators in an emergency, and simplify the design of the generator cooling system.
Because of the distance between the power building and the hospital, Stebnicki chose 4,160-V supply lines to the hospital rather than the Canadian standard of 600 V. “Increasing the voltage allowed us to deliver the same amount of power with smaller conductors,” he said. “We saved so much on the conductor costs that the overall standby system ultimately cost less.” The 4,160-volt lines run underground and then through a series of duct banks to the main building’s penthouse. From there, power is stepped down to 347/600 V.
The design team chose the PowerCommand digital master control (DMC) system from Cummins Power Generation for two reasons: complete integration with the generators and ability to meet interoperability requirements. There are two touch-screen control panels for the generators and transfer system, one in the generator building and another in the penthouse. They are linked by fiber-optics.
“The system can be controlled from either point–and changing anything on either screen updates the other screen in real-time,” said Steve Falk of Trotter & Morton, the project’s electrical construction manager. “It is also possible to control the system through a PC from anywhere, but the design team chose not to implement that capability, partly for security reasons and partly because qualified personnel are in the hospital at all times.”
According to Dave Drinkwater, the hospital’s maintenance and engineering manager, Calgary’s municipal power company, Enmax, is a highly reliable source of power. Outages are rare; in fact, there have been none since the hospital opened. ”In the rare event that Enmax needed to shed loads, we would be considered a high priority,” said Drinkwater.
The Canadian Standards Assn.’s Z-32-04 standard, ”Electrical Safety and Essential Electrical Systems in Health Care Facilities,” requires that generators be online within 12 seconds of utility outage. The system does much better than that, according to Stenicki. “The DMC has extensive capabilities. It enables operators to monitor all major loads in the building and provides history on the profiles of all those loads, which is a very effective planning tool. When the system detects a loss of normal voltage, the UPS takes over and can, theoretically, supply power for all critical needs for hours. But the UPS doesn’t have to supply power for that long; that isn’t necessary, because as soon as there’s a power outage, the system also sends a start signal to the generators.”
Once the generators are up to speed—which takes about 10 seconds—the system again transfers power smoothly to the generators. Then the system senses when the utility comes back online, and again makes a smooth, synchronous switch back to the utility power. Fuel capacity for the generators is 13,208 US gal.; depending on loading and the season, the generators could power the entire hospital for approximately 44 hours.
In a simpler system with one standby generator, the move from one power source to another would be accomplished through a transfer switch. “But since the hospital is much more complex—-three generators, UPS and feeds from two utility substations-—there actually are no transfer switches,” said Stebnicki. “Switching is done through the main breakers; the DMC software accomplishes seamless, synchronous switching.”
The new hospital also exceeds other requirements of Z-32-04. For example, the standard lists critical loads that must be connected to the emergency power system. For an acute care facility such as Alberta Children’s Hospital, that list includes operating rooms, the intensive care unit, trauma care and emergency facilities, stairway lights and power outlets around every patient. The list also includes ventilation fans—in both the operating rooms and patient rooms—that determine airflow direction and therefore help to control the spread of infection. However, since just two of the three 2 MW standby generators are needed to handle the hospital’s entire load, it is unlikely that the hierarchical system will be called upon. Drinkwater’s staff tests the generators and associated equipment weekly using actual hospital loads rather than a load bank.
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