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The electrical transmission and distribution industry has learned some unwelcome lessons since the turn of the 21st century. The industry’s three big grid security and operations lessons came from the attacks on Sept. 11, 2001; the Northeast blackout in August 2003; and Hurricanes Katrina and Rita in August 2005. The unstable (but seemingly always rising) energy prices have taught the need for efficiency to reduce costs. In addition, the growing warnings of global warming are highlighting the need for utilities to use green technology to be environmentally responsible.
Those lessons have convinced Austin Energy—the community-owned electric utility in the city of Austin, Texas—to consider new ways of doing business in central Texas. One of those ways has been to partner with the not-for-profit Seton Healthcare Network to build a combined heat and power (CHP) energy plant at Seton’s new Dell Children’s Medical Center in the city.
Austin Energy serves 360,000 customers and a population of more than 800,000, making it the nation’s 10th largest community-owned electric utility. Seton’s new Dell Children’s Medical Center is a 475,000-square-foot, 170-bed, $200 million facility that will replace and dwarf by three times Seton’s current Children’s Hospital of Austin. The new medical center opened in June 2007.
Energy plant mechanical and electrical
Austin Energy selected the engineering firm Burns & McDonnell to provide the $18 million design/build turnkey installation of the on-site CHP energy plant, which will generate more than 100 percent of the hospital’s energy requirements. The excess electricity already is being exported to the existing utility grid, and the excess thermal energy (chilled water cooling and steam heating) is distributed through a network of underground pipes to neighboring buildings.
This project was a partnership of all of the stakeholders from the onset. Burns & McDonnell functioned as both engineer and general contractor and gathered its team for this project, which included Spur Electric of Austin.
“We had worked with Burns & McDonnell on other projects, and we were really pleased with the quality and thoroughness that we delivered,” said Jerry Gilbreath, owner of Spur Electric. “I guess that [Burns & McDonnell] felt that way, too, because they asked us to help with both the design and construction phases of this project.”
Once the Burns & McDonnell design/build team won the contract for the CHP project, it needed to move quickly. Construction began in November 2005 while portions of the design were still in process. In April 2006, just under six months from the start of construction, the plant began initial startup operations. Final wrap-up construction was completed in time for the medical center’s June opening. “That [tight schedule] made good working relationships crucial,” Gilbreath said.
The energy plant includes multiple pre-engineered modular components that arrived on large skids and were put into place by the mechanical contractor, 5F Mechanical Group Inc. of Austin. At that point, the Spur Electric crew performed the interconnect wiring and electrical power connections to both the components as well as to control and instrumentation devices. And, in many cases, Spur Electric determined the electrical raceways, conduit and/or cable tray layouts for that wiring.
In addition to the CHP system, the pre-engineered modular components included a 1,500-ton electrical duplex centrifugal packaged chiller plant complete with cooling tower and condenser water pumps; a 20,000 PPH natural-gas-fired standby packaged boiler; deareator, surge tank and blowdown separator; primary and secondary chilled water pump skids; a 1,500-kW emergency diesel engine generator; an 8,000 ton-hour chilled water thermal energy storage tank with packaged pump skid; and chemical treatment skids.
Spur Electric’s installation responsibility also included one 12,470- to 4,160V substation, two 12,470- to 480V substations, draw-out circuit breakers and bus grounds. Spur Electric also installed the electrical panels, transformers and the manual transfer switches for the distribution of power throughout the facility. It installed a Chalfant cable tray system for power and control cabling and rigid conduit for the 15-kV feeders.
The CHP energy center is capable of producing up to 4.3 MW of on-site generation at a simple heat-rate efficiency of 38 percent and guaranteed nitrogen oxide emissions of five parts per million without catalyst. The exhaust from the combustion turbine is ducted through a bypass diverter valve to a heat recovery steam generator (HSRG) that produces up to 13,000 pounds per hour of saturated steam. The HSRG produces enough steam for hospital process heating, including a nominal 900 tons of chilled water from a two-stage absorption chiller. By recycling the exhaust heat into useful thermal energy, the overall CHP system efficiency can reach a remarkable 75 percent.
The CHP system’s exceptionally low emissions exceed Texas Commission on Environmental Quality standards permitting threshold for carbon dioxide, oxides of nitrogen and sulfur dioxide for this area of Texas, which is designated by the Environmental Protection Agency as “near non-attainment [of the standard]” for air pollutants.
Connected both inside and outside
In addition to the higher-voltage electrical work, Spur Electric also installed low-voltage cabling in the CHP energy center. The programmable logic controller (PLC) panel is connected by approximately 15,000 feet of 14- to 16-gauge, 12-conductor control cable to nine computerized control panels and about 50 sensors throughout the electrical plant. The PLC panel then is interconnected to and managed by a computer data network that runs over Category 5e shielded and unshielded twisted pair cable.
Outside the plant, the CHP energy center is connected by 12,470V feeders to both the medical center as well as to two independent substations on the power distribution grid.
“A remarkable element of this facility is its ability to coexist peacefully on the power distribution grid,” said Cliff Braddock, Austin Energy’s director of Energy Business Development. “It’s a major accomplishment to have this energy center function as an integral part of the power generation resource on the grid in the middle of an urban setting.”
On-site energy system
Under normal circumstances, the medical center runs in parallel with the electrical grid with two existing electric feeders providing backup electric service whenever the on-site energy system is not in operation. In the event of a grid disturbance or outage, the on-site CHP energy center can disconnect from the grid and “island” or independently provide power to the medical center and its other clients without any disruption of service. Recent American disasters have demonstrated that many people—including those who are healthy—will seek sanctuary at hospitals during extended power outages, believing that hospitals will maintain the ability to function during such times. The on-site CHP energy center will help the Dell Children’s Medical Center prepare for such an influx in the event of a disaster in Austin. It will be one of the first hospitals in Texas with an on-site energy system as a possible primary means to meet its energy needs, treating the grid as a backup.
The Dell Children’s Medical Center CHP energy center demonstrates that Austin Energy has delivered on the lessons that its industry has learned this decade. The plant’s ability to “island” makes it able to withstand grid security and operations difficulties that traditional facilities cannot withstand. And, the plant has impressively high energy efficiency to battle high energy costs and equally impressive low emissions to be “green friendly.”
Gilbreath knows on every job—regardless of the specifications—everything always comes down to quality work and good customer service.
“Doing good work and doing our best is our business plan,” Gilbreath said. That plan works well for Spur Electric, with the bulk of its projects coming from word of mouth and repeat customers—such as Burns & McDonnell’s Dell Children’s Medical Center CHP energy plant project.
“You’ve got to make people want to do business with you,” he said. EC
MUNYAN is a freelance writer in the Kansas City, Kan., area, specializing in technical and business writing. He can be reached at www.russwrites.com.