Touted as the perfect renewable energy source for Idaho, geothermal systems fire up proponents in the Wood River Valley. Affordable housing and schools are doing it.Should you?
By Trevon Milliard. Photo by David N. Seelig.
Tim Flaherty’s home uses the ground beneath it to heat its water, forced-air and radiant heating systems, driveway snowmelt and even the outdoor pool. And not a single hot spring flows through his Gimlet property.
The ground that Flaherty’s large house sits on has no special qualities. It absorbs and retains the sun’s energy in the same way all earth does, maintaining a warmer temperature than the air in the winter, and a cooler temperature in the summer.
Just eight feet beneath the earth’s surface the temperature ranges between 45 and 75 degrees Fahrenheit year-round, depending on latitude. In the Wood River Valley, it averages about 50 degrees. By tapping into that heat, water coming out of Flaherty’s faucets can reach a toasty 120 degrees. “That’s where the magic of the ground-source heat pump comes in,” said Evan Lawler of Western States Geothermal, the year-old Ketchum company that installed Flaherty’s geothermal system. The heat pump enables water to go from 50 degrees to whatever temperature is required. And it doesn’t stop there—geothermal heat pumps can also provide heating (and cooling) for forced air, radiant heat, air conditioning, pools, snowmelt and spas.
The best analogy, according to Lawler, is a refrigerator. The common household appliance also uses a heat pump, which doesn’t put cold into the unit, but removes heat from the interior. Geothermal ground-source heat pumps similarly take heat out of the earth by flowing water or an antifreeze solution through a hose running underground in a closed loop. The liquid never leaves the hose but absorbs the earth’s surrounding heat and then transfers it to a heat pump inside the house. Once the liquid has done its job of heating, the now-cooled liquid cycles back underground to be rewarmed and used again.
A common alternative to this closed-loop system is an open loop. Widely used in this area, an open-loop system uses two hoses extending from the house down to the aquifer. One of the hoses pumps water out of the aquifer, acting like a straw. The ground water travels to the heat pump where it transfers its heat. Once the water’s heat is extracted, it is returned to the well through the second hose. “The water never sees the light of day,” Lawler said. “It isn’t contaminated or mixed with anything else. The temperature is just changed.”
The technology isn’t new, just improved. Mechanical engineer Brian Formusa of Thermal Temp has been installing heat-pump systems since the early 1980s. System glitches from back then have been fixed. “But it’s still an evolving science,” he said. For example, no simple equation exists for determining the length of hose needed in a closed-loop system. It’s usually overestimated to be safe. But the loop is the most expensive part of a geothermal system.
But how is groundwater entering Flaherty’s house at 50 degrees Fahrenheit able to heat tap water to 120 degrees? Another refrigerator analogy works best. To take the heat out of air inside a refrigerator, gas flows through a pipe, expanding when traveling inside the refrigerator and compressing when it’s outside. The expanding gas picks up heat from inside the refrigerator and carries it to the outside. This exponentially cools the inside of the refrigerator because expanding gas cools. An easy example: Spray an aerosol air freshener, and notice that the expanding gas causes the spray and container to become cold.
A ground-source heat pump does the opposite, using the 50-degree groundwater to heat a refrigerant that boils and evaporates at a low temperature. That gas is then condensed back into a liquid—the opposite process of an aerosol spray can—and heats to a high temperature in a closed system. This heats water or air passing over coils.
According to Lawler, the beauty of the system is that it can be reversed in the summer for air conditioning by “taking heat out of the home and putting it back into the earth,” which will now be cooler than the air. “And before you get rid of that heat, you can preheat your water,” he added.
Because it sounds complicated, people assume geothermal is expensive, requiring constant maintenance and attention. “Think about the last time that you did maintenance on your refrigerator,” Lawler said. “You see decade-old ones still chugging along.”
And there are no fancy geothermal gadgets to clutter one’s home. A standard heat pump takes the same space as a conventional water boiler, with the majority of equipment hidden underground. And it’s all controlled by a traditional thermostat system.
But (and there’s always a but), geothermal is an investment at the onset, costing 30 to 40 percent more than conventional water-heating boilers that depend on gas or electricity. But the payback comes quickly, especially with a federal tax credit reimbursing homeowners for 30 percent of the project’s cost. (Commercial buildings receive a 10 percent tax credit.)
Also, while a heat pump uses electricity, like a refrigerator, it does not require combustion or natural gas. “I got my gas bill,” Flaherty said, “and it was pennies of what it would be if I didn’t do it.” For every unit of electricity the heat pump uses, Lawler said, it provides about four units of equivalent “free” energy to heat whatever method is chosen (water or air or both), making it on average 400 percent efficient.
Because of this combination of payback and practicality, Idaho Office of Energy Resources Administrator Paul Kjellander said ground-source heat pumps have seen a spike in demand from Idaho homeowners over the last couple of years. “Besides saving money, it’s a way to avoid the volatility of gas prices,” he said.
Last year, Kjellander was part of the Idaho Strategic Energy Alliance board that oversaw a taskforce investigating the pros and cons of geothermal. The taskforce found geothermal technology to be highly beneficial in Idaho. “Idahoans have long used geothermal energy for direct-heating purposes, decreasing their use of other types of energy such as natural gas and electricity,” the taskforce reported. “Direct heating is still a key use for Idaho’s geothermal resources and should be encouraged and expanded.”
The Wood River Valley will soon see ground-source heat-pump applications in commercial-size buildings. Western States Geothermal will install a geothermal snowmelt system for affordable housing complex Northwood Place in Ketchum. Last November, the Blaine County School District received a $4 million matching-funds grant from the U.S. Department of Energy to use geothermal pumps to heat its school buildings.
School District Business Manager Mike Chatterton said construction will begin this summer in Carey, Bellevue and Hailey, and be finished next year. The rest of the county’s schools will see geothermal implementation after that.
Using the ground for heat isn’t a new idea. Thousands of years ago, people took advantage of the earth’s ability to retain the sun’s energy by living in caves.
The ground-source heat pump makes geothermal viable pretty much anywhere, and an easy choice for any homeowner. The components require the same space as a conventional boiler, and the energy-efficient technology doesn’t impart the aesthetic interruption that solar panels can. John Ashton, who is installing a system in his 4,600-square-foot Warm Springs home, considered solar panels but quickly turned toward geothermal. “This seems to be the most practical,” he said. “And I don’t have to put things sticking out of my roof.”
Why choose geothermal?
• The U.S. Environmental Protection Agency rates geothermal heat pumps as among the most efficient of heating and cooling technologies, with estimated energy savings of up to 70 percent.
• They don’t need gas to operate, so there is no combustion, flames or fumes and no chance of carbon monoxide poisoning.
• Geothermal heat pumps use 25 to 50 percent less electricity than conventional heating or cooling systems (source: U.S. Department of Energy).
What’s the cost?
Retrofit: To install geothermal forced-air or radiant heating into an existing 2,000-square-foot home runs between $25,000 and $30,000.
New construction: To install geothermal forced-air heating* into a 2,000-square-foot home during construction costs about $45,000. (This includes installing ductwork).
Tax credit: Either method is eligible for a 30 percent federal tax credit toward the $25,000-$30,000 geothermal unit. With new construction the credit can be extended to the $15,000 of ductwork.
More money back:
The additional cost of installing a geothermal system is returned in energy savings in five to 10 years (source: U.S. Department of Energy).