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
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
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outdated and landlocked in downtown Elgin,
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
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
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
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.
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
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
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
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.
system also is flexible and can be expanded to meet the future growth needs of
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.
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
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.
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.
For more information,
of upload: 20th Nov 2013