Hospital Design

Advocate Sherman Hospital: Largest lake-coupled geothermal system paying off


By Warren L. Lloyd PE, LEED AP

Just four years after Advocate Sherman Hospital opened the doors to its new US$230,000,000 greenfield campus outside Chicago, it is nearly half way to paying back the $6.1 million investment that provided it with the largest lake-coupled geothermal system in the world.

The success of the system and its relatively short payback show what can be achieved – and saved –with geothermal at a healthcare facility given the right combination of resources and commitment. “Based on current utility rates, the payback has been a little slower, since the price of gas has gone way down since the facility opened,” said Ray Diehl, chief engineer for Advocate Sherman.

“But we’re still on track for payback in potentially four to six years. By the end of this year, we will be at $3.5 million (of the payback).” The hospital’s decision to build a new campus was driven by its need for an updated and enlarged facility; by 2005 its then-100-year-old, 5-hectare campus was outdated and landlocked in downtown Elgin, Illinois. Fortunately, the hospital had had the foresight to purchase a nearby 62-hectare cornfield overlooking a 10-hectare forest preserve – plenty of room for a new 60,000-square-meter replacement hospital.

As work on the master plan for the new campus began, hospital officials asked the design team – led by architects Shepley Bulfinch Richardson Abbott of Boston – to provide both a healing environment for patients and follow the principles of sustainable development.

The available land, coupled with the size of the project, motivated KJWW Engineering Consultants to suggest the incorporation of a geothermal lake system. A detention pond already was required for the site, and it easily could be enlarged to accommodate the needs of the system.

Furthermore, KJWW could provide the know-how, having previously designed the world’s first lake-coupled geothermal system for healthcare in 2000 at Great River Medical Center in Burlington, Iowa. Geothermal systems can have substantial additional upfront costs, however, so Advocate Sherman proceeded cautiously.

Their lake-coupled system was estimated to cost an extra $6.1 million – $3.5 million to install (above the cost of a conventional gas-fired mechanical plant), $1.6 million for the additional 4 hectares of land needed to expand the detention pond, and $1 million to excavate the pond. With annual energy savings estimated at $1.1 million, however, the hospital would be able to recoup the cost of the system in just six years. Advocate Sherman officials visited Great River to tour that facility’s lakecoupled system and talk to that hospital’s administrators, who gave the design glowing reports.

Great River’s success with, and endorsement of, the system – coupled with the long-term savings and relatively quick return on investment – convinced Advocate Sherman to adopt the geothermal system for its facility. Ground broke in June 2006, and the geothermal system was installed in the lake in the spring and summer of 2008. On December 15, 2009, patients and staff moved in to the facility, which features a six-floor, 255-inpatient-bed tower; a Level II trauma center; emergency department; cancer center; cardiac care center, radiology; woman’s diagnostic center, and kitchen and cafeteria.

The parameters of the geothermal lake required for the campus were determined by a limnologist retained by the design team. The complex task involved sizing the lake and arranging the heat exchangers to derive maximum heat transfer; water depth and temperature gain also were studied to ensure the lake would support wildlife and not become choked with weeds or algae.

To help maintain a consistent water level, the 5.5-meter-deep lake is lined with a 1-meter-thick layer of clay reclaimed from the lake excavation material. The water level is maintained by storm water runoff; two wells serve as a backup but to date never have been used.

The geothermal system itself consists of relatively few different components. Lying in the water 4.5 meters below the surface are 175 geothermal grids (each 9 meters by 2.5 meters) which serve as heat exchangers.

The grids are made of 240 kilometers of polypropylene pipe and are the only structure in the lake. Should a grid need maintenance, it can be filled with air and floated to the surface.

Each grid sends a nontoxic mixture of water and methanol through a pair of flexible 5-centimeter pipes to a manifold room inside the hospital. From there the fluid is transferred to the main 60-centimeter supply and return pipes that fan out to individual heat pumps. Since a hospital operates around the clock and heating and cooling needs vary on a room-by-room basis, every patient room or group of offices has its own thermostat.

At Advocate Sherman, that means about 1,000 waterto- air heat pumps are located throughout the building. For ease of access and routine maintenance, the pumps are located in small closets along the patient corridor. Back-up boilers are available to heat the loop’s fluids if the system ever fails for any reason.

And while the geothermal system heats and cools the critical life areas (emergency department, inpatient surgery and ICU), conventional air handlers provide the high volume of ventilation and filtration required in these areas. The entire geothermal system relies on the lake water to cool the fluid in the warmer months and heat the fluid in the colder months.

The fluid also redistributes energy throughout the building in the winter, absorbing interior ambient heat (generated by people, lights and machinery) and releasing it in outer rooms before returning to the lake, which acts like a 6-hectare cooling tower. Because of the large amount of ambient heat produced inside hospitals, Advocate Sherman’s geothermal system actually works in cooling mode 10 months of the year – even in Chicago’s northern climate.

Besides huge energy savings for the hospital, the lake-coupled geothermal system provides many other benefits. The system is quieter than a conventional HVAC system and eliminates the need for large, unsightly and noisy cooling towers. The mechanical plant size is reduced, and shaft sizes are 10% smaller than conventional ducted heating and cooling systems since a portion of the energy is supplied hydronically. Maintenance is simpler and can be done on individual heat pumps, eliminating the shutdown of an entire system.

The system also is flexible and can be expanded to meet the future growth needs of the campus. (Currently the system provides 2,400 tons of cooling, with the ability to expand to 3,400 tons.)

The system also provides the hospital with an avenue for educating the public on its environmental stewardship: Visitors entering the lower level from the parking lot pass through an enclosed concourse overlooking the lake on one side and the piping and pumps in the manifold room on the other. Educational signs describe how the geothermal system works.

“We have done much education with our local community college, high school and middle schools,” said Diehl. “Science classes come here and they teach the students about sustainability and energy efficiency, and they teach them about how the geothermal system works. It has been very well received by the community, and especially the schools.”

From a natural healing standpoint, the lake-coupled geothermal system dovetails nicely with the tranquil and therapeutic environment that is the hallmark of the Advocate Sherman campus.

The lake provides habitat for fish, ducks and native wetland plants, and is ringed by a 1.2-kilometer bike/walk path, providing a place for outdoor exercise. It is an integral part of the campus’s natural setting, which faces a forest preserve and also includes healing gardens, a prairie restoration, a variety of plantings and no-mow grasses. This connection between nature and healing continues on the interior of the hospital, starting at the lake-level entry.

A stunning, four-story atrium features a 21-meter-diameter central support nicknamed the “Tree of Life,” its eight structural columns curving outward and upward like tree limbs. Additionally, 75% of the inpatient rooms feature a window with a calming lake view. The economic, aesthetic, therapeutic and environmental benefits of the lake-coupled geothermal system easily justify the added investment required. In just a few more years the system will have paid for itself, and the hospital will begin to realize the substantial energy savings year after year. “It all comes down to Btu per square feet,” said Diehl.

“The old hospital used 352 kBtu per square foot (3,787 kBtu per square meter) per year. Now we’re at 192 kBtu per square foot (2,076 kBtu per square meter) per year.” Compared to the old campus, Advocate Sherman now uses 80% less natural gas, 15% more electricity, and 72% less water.

The geothermal system heating and cooling the campus saves the hospital upward of 30% in space conditioning costs each year, making Advocate Sherman one of the most energy-efficient healthcare facilities in the world. Although the hospital did not pursue LEED certification, it has nonetheless provided a presentation on its highly energy-efficient system at the request of the U.S. Green Building Council, the purveyor of LEED accreditation. It also has been visited by several other healthcare organizations.

Like Great River before it, Advocate Sherman now serves as an example of what can be accomplished with geothermal in a healthcare facility, given the desire for sustainability, willingness to invest and the right resources – the primary factor being the availability of a lake, wells, or the ability to dig deep into the earth. “Going ‘green’ is more than a geothermal system, and other healthcare institutions often times aren’t as lucky to have the land to dedicate for such a system,” said Dawn Stoner, project coordinator for Advocate Sherman. “I think we serve as an example in that we were able to think ‘outside the box.’ ”

For more information on Advocate Sherman Hospital’s geothermal lake, visit:

About the author

 Warren L. Lloyd, PE, LEED AP, is vice president and a client executive for KJWW Engineering Consultants, a recognized expert in high performance design, sustainability and LEED. KJWW provides mechanical, electrical, structural, technology and acoustical engineering services as well as architectural lighting, medical equipment planning, energy modeling and commissioning. It serves the markets of healthcare, education, industrial, corporate, commercial, sports and recreation and government. The U.S.-based company has 14 office locations, including Dubai, UAE, and Ahmedabad, India.

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 Date of upload: 20th Nov 2013


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