Cool Returns

Hospital Owner Taps Geothermal to Save $1 Million Annually

by Tudor Van Hampton

Just a few years ago, using alternative energy to heat and cool buildings seemed like a good idea, but it didn’t always make financial sense.

Today, rising energy prices and conservation concerns have owners crunching the numbers again, and some are finding that green technology, such as geothermal energy, can easily generate cold cash. Even in a chilly climate like Chicago, the economics of heat pumps are showing some sizzle.

Sherman Health, owner of a new 255-bed hospital in Elgin, says it will save more than $1 million a year by tapping into a 15-acre, 17-ft-deep geothermal lake—engineers believe it to be one of the world’s largest—that will provide heating and cooling for the 650,000-sq-ft facility.

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The decision to go geothermal for the $310-million project, which broke ground in June 2006 and is scheduled to open in late 2009, was a “fiscally responsible choice,” says Sherman Health on a Web site it built to educate the community about the project’s green benefits.

Geothermal lakes can be attractive for commercial buildings, and hospitals, with their X-ray equipment, computers and bright lights, are an ideal installation, says Jim Bose, executive director of the Stillwater, Okla.-based International Ground Source Heat Pump Association, which develops standards for geothermal systems.

“A pond can just gobble up energy,” he says. “Every time the wind blows, it just puts energy right into the environment.”

When the building needs cool air, heat pumps remove heat from inside and transfer it to the lake. When the building needs warm air, the pumps draw heat from the lake and transfer it into the building.

Geothermal Growing But Rare

The geothermal market in the U.S. has been growing at a steady 30% clip year over year, but it still represents only 1% of total share, says John Kelly, executive director of the Washington, D.C.-based Geothermal Heat Pump Consortium Inc., a national trade group.

Upfront costs are a huge factor. Loops buried in the ground require equipment and labor, and not everyone has space to build a pond.

“As a general rule, the geothermal heat pump unit is roughly the same cost as a conventional furnace,” Kelly says. “The additional cost is burying the piping in the ground.”

That investment—up to double that of conventional heating, ventilation and air-conditioning systems—can pay off faster if a pond already exists onsite.

“Around here, we say that if you have a pond out in the back of the house, that’s just like stealing from the bank,” Bose says.

In Elgin, Sherman Health knew that it needed to build a small retention pond on its 154-acre site.

“Obviously, they have plenty of ground,” says Warren Lloyd, project manager with Rock Island, Ill.-based KJWW Engineering Consultants PC, the structural/MEP engineer “But the ground was $160,000 an acre. If we are going to make a 15-acre lake, it is going to be part of an economic analysis.” Using the lake as part of the geothermal system was seen as saving operating costs on the building through reduced heating and cooling.

KJWW had already designed the second-largest lake loop in the country, a 13-acre exchanger for Great River Medical Center in West Burlington, Iowa, which opened in 2000.

Lloyd says that Sherman officials “kicked the tires” of the Iowa facility and in the end determined that the lake loop would cost $4.5 million to install. Add to that the extra $1.6 million for the land, and the owner was looking at a $6.1-million upfront cost over a traditional HVAC system. But at a savings of over $1 million per year, it wouldn’t take long to pay off, according to Sherman Health.

“Without the land, it was 4.82 years,” Lloyd adds. “Payback with the land is 6.52 years.”

The savings are probably more today. “Over the last two years, design prices have only escalated,” says Dawn Stoner, a spokeswoman for Sherman. “We see this as a great savings for the hospital.”

Getting Loopy

Installing the lake loop, which provides heat exchange for the hospital’s 2,450-ton-capacity HVAC system, took a learning curve.

“It is simple in theory, but you are talking about thousands of feet of pipe,” says Selena Worster, project manager for Hillside, Ill.-based Mechanical Inc. In total, the system sports 150 mi of high-density, polyethylene tubing; 175 underwater heat exchangers; and 750 water-to-air heat pumps within the building. A water-methanol solution, which engineers say is nontoxic, flows through the system. Experts say the tubing lasts at least 50 years, and the heat pumps, with sealed refrigerant lines, require little maintenance save routine filter changes.

Resting at the bottom of the lake are the heat exchangers. Fabricated onsite, the 30- by 8-ft PVC frames hold 14 coils of 3/4-in. tubing supplied by Fort Wayne, Ind.,-based Loop Group Inc. Workers map out a grid according to plans and float the exchangers above their predetermined parking spots. Then, fluid is added to the units, and they sink to the bottom.

Supplying the “rafts,” as workers call them, are 275,000 ft of 2-in. tubing headers that carry the antifreeze solution into a manifold room. There, building engineers can control the flow of each of the 350 supply lines running out to the lake.

When maintenance is required on a raft, engineers can drain the system with a flip of a ball valve in a drop line and pump in air. The raft floats back to the surface. The contractor preferred the “wet” installation because placing the rafts before filling the lake would disturb its clay bottom, Worster says.

Four variable-speed pumps circulate the fluid through the system. Solenoid valves can also carry fluid from hot rooms needing cooling to other parts of the building needing heat.

Overall, the system provides about a 35% efficiency increase over traditional HVACs, Lloyd says. The building is designed with code-required boilers to heat the loop water, in case the system fails. The boilers also provide water heat and steam for sterilization.

Unlike drilled geothermal wells, however, lake loops do not remain at a constant temperature.

“The lake temperature is going to vary from 39° in the wintertime to the mid-80s in the summertime,” Lloyd says. But because the hospital will be cooling nearly year-round, the lake effectively “is like a 15-acre cooling tower.”

Worster says the lake is already getting green marks. “I think it’ll help bring geothermal more to the forefront and show that it can be done using what you are already planning on your site,” she says.

The lake will even be stocked with fish for ambiance, but there will be no fishing.

“We don’t want people catching their hooks on our stuff,” Lloyd says.

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