Lower energy costs and a fast payback make GSHPs a shrewd, down-to-earth investment.
By David Engle
Constant, free geothermal energy doesn’t need much of a delivery system; it’s sitting right under your feet, wherever you go. Easily tapped with a ground source-heat pump (GSHP), geothermal energy produces no combustion or emissions. Steadier and more reliable than solar or wind, available day or night, in all weather and seasons, it’s probably the best of all renewables. Heating and cooling alternately—or doing both at once in some cases—GSHP systems are also readily scalable for applications large and small. And, since its initial rollout in the United States in the early 1970s (and elsewhere thereafter), there’s now a broad base of successful GSHP applications, with decades of reference data.
Groundswell of Growth
All of this is now translating into booming growth that has averaged 12% annually since the mid-1990s, according to figures gathered by the Oregon Institute of Technology’s (OIT’s) Geo-Heat Center. Currently, in the United States, about 80,000 systems are being installed each year. Overseas, in about 30 other countries now, similar double-digit annual growth is also typical. Annual unit sales have soared tenfold in several nations of Europe and Scandinavia over the past decade.
In these green-conscious times, several key factors are poised to elevate GSHPs to the next level—that is, to adoption by builders and developers as the preferred option for heating and cooling.
One factor is that of higher energy costs (and concerns that market and supply instabilities will drive costs even higher). As Lisa McArthur, assistant director of the International Ground Source Heat Pump Association (IGSHPA), notes, “Without question, higher fuel prices are our best friend in the market.”
Environmental awareness is another important element. The seriousness of global warming has stirred a grassroots movement among architects, system designers, builders, and buyers favoring more conscientious investment in renewables. “People want to conserve energy and use green technology that helps the planet, for their children and grandchildren,” says McArthur. “The ‘boomer’ generation wants to leave a positive impact.” And the boomer generation is willing to pay for it.
A third factor, McArthur says, is a broadened skills base. “More experienced contractors with better knowledge, licensing of installers and designers, [and] technical conference” are increasing market accessibility and impact. “It’s been a process of building a reputation, a borehole at a time,” she says.
And finally, steadily improving technology is making the first cost cheaper, the payback quicker, and the hardware more productive and efficient. Examples include dual compressors, which allow for two operating modes: one for basic efficiency and the other an “overdrive” for an output boost on very warm or cold days. Also, there’s grouting to improve ground heat transfer, cheaper drilling methods to leave the surface undisturbed, and location-specific design options to ensure flexibility.
Cool Idea, Multitasking
OIT engineer Andrew Chiasson describes a recent geothermal project that integrates three chilling/heating services at once: GSHP icy refrigeration, comfort heating, and domestic hot water, all running simultaneously at an ice rink in South Caribou, BC. “Basically, the system shares two loads,” he explains. An icemaker rejects heat from the skating rink freezing coils directly into the arena seating area, adding to spectator comfort. Heat that isn’t needed in the seating area can be used to warm the locker-room showers. In addition to providing these benefits, the GSHP ground loop acts, he says, “as a storage mechanism, where heat is being shared as it’s rejected from the ice rink.” Excess heat goes down into the earth and is extracted later as needed. “You really cut down on the overall cost of a system when you can share loads like that,” he says.
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| Cut-away diagram of a house with a horizontal loop unit |
As for the breakdown of refrigeration or heat energy yielded: 84 tons freeze the ice rink; 20 tons provide dehumidification; 10 tons go for servicing hot water; and 48 tons heat or cool the arena, offices, lobby, and locker rooms.
What’s rather spectacular and extraordinary, too, in this design, is that the GSHP energy eliminates the need for a conventional, ammonia-based absorption chiller altogether. These are, Chiasson notes, “a bear” to run. “Operators must be hazardous-waste trained, and you have incredible maintenance costs”—including oil disposal, frequent compressor rebuilds, and monitoring—all of which have now been either eliminated or minimized by the heat pump’s relatively light maintenance need.
The new system uses nontoxic R404A at only 10% of the conventional volume and can operate down to 0°F on the evaporator and 125°F on the condenser side.
Better still, first cost for the hardware itself (not counting added loop installation) came to about $60,000—considerably less than the $110,000 price tag on a comparable conventional system.
“There are so many advantages in this,” he says. “The payback comes in about two years,” thanks to a federal incentive, without which the payback would take three.
Also, with that roaring success model, “Just about every new ice rink in Canada” is now demanding this wonder-working energy plant, he adds, and several established rinks are being evaluated for a retrofit.
Other candidates for this dual-action heat pump system might include any facilities that need heavy refrigeration and heating simultaneously, such as those found in supermarkets in cold climes. “All the heat [from the chilling system] has to be rejected somewhere,” Chiasson says. The obviously best use is to send it “back into building, into front door area ... That’s a tremendous energy saving, with or without a ground loop,” he adds; but a loop “acts as buffer zone, so if you have an excess amount of refrigeration load in one day, you can put it in the ground and then recover it later on during a cold spell.”
Foundation Tubes and Sewage Heat
Because drilling deep holes for GSHP does add considerable first cost, architects have also been contributing to the overall affordability effort by designing buildings with vertical loops—or “energy piles,” as they’re sometimes called—integrated into the foundation. “You’re already drilling holes for foundations,” Chiasson notes, “so why not take advantage of it to throw some loops in?” Becoming fairly commonplace in Japan, energy piles are slowly catching on in North America.
Another recent structural innovation, from Germany, is that of buildings that can use heat from adjacent sewers. At a temperature of about 70°F, sewage is usually much warmer than the ground, which may typically measure 50°F in colder climates. Large residential apartment complexes produce steady sewage that can be turned into a partial but constant energy source. “Heat pumps are used to amplify this heat,” Chiasson says. Systems must be controlled to avoid freezing the sewer as the heat is withdrawn. Newer concrete sewer pipe designs in Germany now incorporate copper conduits to serve as heat exchangers.
In a similar vein, although still experimental, heat-exchange coils are being routed under septic fields to capture the warmth from biodecay.
“District heating” represents yet another dimension of GSHP technology. Halcyon Meadows and Sun River are two housing developments in Chiliwak, BC, that share “community loops,” Chiasson says. These draw well water from a copious sand aquifer. Water is then piped into each home’s heat pump. After the heat exchange, the water discharges and percolate back through the highly permeable ground.
“Distributed” Geothermal Power
Besides providing the benefits of heating and cooling, the hot water produced by high underground temperatures can be converted into electricity by turbines. Such geothermal power has been tapped by power plants for decades, but now a quasi-experimental “mini” geothermal power system is under development by United Technologies (UTC). In August 2006, UTC fielded its first commercial demonstration—a 200-kW turbine at Chena Hot Springs in Alaska. What’s extraordinary and “groundbreaking” here is that electricity can be generated from sub-boiling temperatures as low as 162.5°F, and don’t require steam. Adjacent to the hot water are year-round springs maintaining a steady water temperature of 40°F. The sharp temperature differential between these two extremes enables efficient energy production from this “binary” turbine. Geothermal energy in the range of 160°F–169°F is fairly common. It can be found all over Alaska (and in many locales worldwide). According to the Fairbanks Daily News-Miner, the state’s geothermal resources in that range, if utilized with the new binary turbine, could provide energy independence for virtually every Alaskan village.
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UTC (which reportedly spent millions to develop the binary turbine) is aiming to make them affordable at $250,000, according to the News-Miner.
As for the Chena Hot Springs resort area, instead of spending $365,000 yearly for diesel fuel and generating power at 30 cents per kilowatt-hour, the town now obtains pristine energy at 5 to 7 cents per kilowatt-hour.
By November 2006, Chena’s prototype plant had already logged 2,000 operating hours, and a second plant was added by UTC in October.
Farther south, at OIT’s campus in Klamath Falls, OR—which already enjoys hot springs at 195°F to warm several buildings—Chiasson reports that OIT will soon try to replicate Chena’s binary turbine success.
Even further south, in Texas, oil and gas wells may also prove to be “hot prospects” for UTC’s onsite geogenerators. Maria Richards of the geothermal lab at Southern Methodist University (SMU) notes that Texas alone has more 600,000 of these. Some are working and some abandoned, but all have deep holes in the earth’s warm crust. Binary turbines are now being explored experimentally by SMU, she says, the aim being “to combine the fluids that are coming out of wells that produce oil and gas—or, to go back and open up wells that were previously abandoned and to flow those wells to generate electricity.”
Chiasson sums up: “All the technology is there, and there’s an array of geothermal opportunities—hindered only by whether the economics will work.” Increasingly, they’re working quite well.
Digging Breakthrough in Indiana
For residential GSHP systems that aim for simple heat exchange benefits, the big hurdle facing homeowner adoption, historically, has been installation cost. Tapping the ground requires extensive—and expensive—digging. For example, to supply one home with an embedded ground loop (the basic means for exchanging energy with the building interior), the loop contact area typically must extend several hundred linear feet—all of it usually trenched at a depth of 4 to 6 feet. This will snake across about one-third of an acre of property. Plastic piping is inserted to channel a flowing solution of water and brine (or methanol or other antifreeze). This will remain in the ground loop for decades. boveground there may be soil settling and, eventually, reparative landscaping. The high digging costs combined with leeriness over downside risks can easily give a buyer cold feet.
The cost of trenching the yard comes to about $800 per ton of eventual air-conditioning value, says GSHP contractor Todd Zeplin. Thus, a typical house needs 3 or 4 tons of air conditioning. This means $2,400–$3,200 in digging expenses on top of the hardware cost, notes Zeplin, co-owner of Colliers Heating and Air Conditioning near Fort Wayne, IN. His firm is a dealer for WaterFurnace International Inc. (also of Fort Wayne), a maker of residential geothermal systems. Payback eventually does come, he says. But until fairly recently the time frame could easily stretch a half-dozen years or more.
Before 2005, Zeplin was installing 60–80 GSHPs annually (nearly all in rural areas), he says, but in that year, WaterFurnace introduced a vastly preferable digging alternative. Zeplin’s business has since exploded. Rather than the constraint imposed by horizontal trenching alone, vertical boreholes work just as well performance-wise but allow loop installation in a space as small as 10 square feet. This has suddenly multiplied his market into residential neighborhoods. All that’s needed for a geothermal loop, he says, is a ground-area the size of a driveway or a patio.
Boreholes for GSHPs aren’t new but were prohibitively expensive because of the cost of the drilling rigs. Then, in 2005 WaterFurnace developed a compact drill that fits on a heavy-duty pickup truck. With that innovation, the price of a hole has fallen as low as $600 (although multiple holes may be needed, and there’s still a $500 charge for connections, Zeplin notes). Overall, he says, a modest $1,000 investment in drilling “is a thousand dollars that is still easily recoverable on the payback.”
Zeplin began advertising small-footprint GSHPs and has been deluged with inquiries. “Our market has grown tremendously,” he reports. Sales have nearly doubled in a year.
On top of this, in October 2006, WaterFurnace introduced a new high-performance GSHP. ated by the Air Conditioning and Refrigeration Institute (ARI) as the most efficient ground-loop system ever certified, it doubles the efficiency of conventional air conditioners and gives five times the efficiency of the best gas furnace.
Zeplin sums up: “We’ve caught people’s attention. Prices have come down. We’re getting better and faster. The technology is getting easier to install. It’s the new wave—in this area anyway.”
Still Some Challenges
Despite the industry’s advances, geothermal still has some ground to make up in the area of standardizing local skill sets. One surprisingly common source of performance problems has been underqualified contractors, notes the IGSHPA’s McArthur. Extra care and consideration should be taken when assessing GSHP vendor references and credentials, she suggests. Training and accreditation are still hit-or-miss in the industry.
Drilling boreholes correctly is also critical, of course. The authority here is the National Groundwater Association. Drillers must typically be licensed—and, occasionally, loop installers, too.
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| Diagram of a house with vertical loop system |
Richards would agree about the shortfall of qualified local vendors. Installer competencies range, she says, from “excellent” to “average” to “problematic.” The order backlog for GSHP installations in Texas is now anywhere from six to eight months.
Apart from mistakes on installations, improper design is another source of grief, says McArthur. Mechanical engineers who may be qualified for conventional HVAC often lack the specialization needed for heat pumps. “It’s a different air-flow system than in your standard system,” McArthur notes, and if the engineer doesn’t do it right “then the system won’t work properly, no matter how good your installer is.” On a larger commercial job especially, she advises, “look for a certified geoexchange designer.” The Association of Energy Engineers now provides bona fides. “We’re also learning that there needs to be more licensing of electrical engineers who are working with GSHP.”
Zeplin finds that complaints occasionally arise when customers receive electric bills that are higher than expected. Investigation of the problem usually reveals a home with inadequate insulation. This aspect should be considered in doing an initial evaluation. As for the equipment performance, he adds, the ARI rating system ensures that hardware itself can’t really be blamed.
On a final note, one recent and encouraging trend Zeplin sees is a willingness among developers to order GSHPs as standard equipment throughout a new community. As of late 2006, his firm had made deals to equip two nearby all-GSHP communities. The respective developers were both touting “green neighborhoods” in sales brochures and promoting homes on the appeal of “their environmental value and low utility costs,” says Zeplin. In a new home, the higher cost of a GSHP can be easily amortized in the mortgage; the buyer immediately realizes a lower net monthly payout by virtue of eliminating fuel bill. “In a new housing market,” he sums up, “if homeowners are given opportunity to pick a heating system, there’s no reason why they would not pick geothermal.” Not to mention the appeal of helping to solve global warming by investing in geothermal’s all-natural “global warmth.” It’s somehow fitting.
La Mesa, CA-based writer David Engle specializes in construction-related topics.
DE - March/April 2007
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