Geothermal Energy Systems Washington DC
Imagine finding free energy on your property, so much of it that you'd never run out no matter how much you ran your furnace and air conditioner. Now for a surprise: There's a bonanza like that beneath your home right now, courtesy of the sun and the earth's massive ability to store heat. It's called geothermal energy, and it can be pumped out of the ground almost anywhere in the country by anyone willing to spend a relatively small amount of money to do it. The real surprise is that so few Americans go to the trouble.
Only 1 to 1.5 percent of the nation's homes use geothermal heat pumps, according to the Geothermal Heat Pump Consortium (GHPC), a nonprofit group that encourages the use of the devices. But homeowners are catching on. Manufacturers say sales of such 'geo-exchange' systems - sometimes called ground-source heat pumps - are booming, and advocates say they are heartened by what they see as growing consumer awareness of the bounty beneath their back yards. Even former oilman George W. Bush uses one at his Texas ranch. 'Our sales have been fantastic this year,' said Al Fordeck, a regional sales manager for WaterFurnace, a maker of geothermal heat pumps in Fort Wayne, Ind. 'We've set records most months.' Tapping Earth's Power Anyone who has seen Yellowstone's Old Faithful has witnessed geothermal energy at its most spectacular.
Geysers and steam vents are found in many parts of the western United States, providing high-temperature water and steam that's used in many places to generate commercial electricity. Less dramatic but equally useful is the moderately hot water found near the earth's surface in some parts of the country, especially the West and South. This water, bubbling up from deep within the earth, is often used for commercial purposes like heating offices and greenhouses. But the most widespread source of geothermal potential - and the one most useful to homeowners - is the energy created in the ground virtually everywhere by solar radiation. The key to geo-exchange technology is the relatively constant temperature of the Earth just a few feet below the surface. That's due to the Earth's tremendous mass and, therefore, its capacity to hold heat. In fact, this thermal mass gives the ground a temperature 'flywheel' effect; the ground actually reaches its maximum temperature in October, four months after the start of summer.
There are two rules of thumb for estimating the ground temperature where you live. One is that it equals the annual average air temperature for the area. The other is that the ground temperature equals 90° F minus the latitude; in other words, the temperature beneath New York City, at 40° N, would be 50° F, while in Miami, latitude 20° N, it would be 70° F. This relatively constant temperature presents an opportunity. It means you can borrow heat from the ground when you need it and dump heat there when you don't. The best way to do that is with a geothermal heat pump. Such systems consist of two parts: The heat pump itself - a misnomer, really, since heat pumps can both heat and cool a home - and a collection system, a series of polyethylene pipes that run through the nearby ground. The pipes can be either buried (anywhere from 4 to 8 feet deep), placed vertically in drilled holes or submerged in a nearby body of water. A Familiar Technology The heat-pump component of a geo-exchange system uses the same technology as a conventional home heat pump. Both work by using vapor compression, the technology used by refrigerators and air conditioners. (See our related story on heat pumps.)
During the cold months, water or an antifreeze mixture circulating in the loop of pipes outside the house absorbs ground warmth and carries it into the heat pump, where the heat is concentrated and used to warm the home. The loop fluid then circulates back outside to gather more heat. When the weather is warm, the process works the other way. The heat pump collects heat from the house and pumps it outside, where the ground acts as a 'heat sink.' Geo-exchange systems cost more than conventional heating and cooling equipment - usually several thousand dollars more. Since most of the extra cost is for the loop system, the ground conditions of the site can make a big difference in cost. On the plus side, they are highly efficient, allowing homeowners to recoup the added cost in only a few years. In fact, some 70 percent of the energy used by a geo-exchange system is provided by the ground itself. That translates into lower energy bills.
The Environmental Protection Agency says that, compared to conventional equipment, geo-exchange systems save homeowners between 30 and 70 percent in heating costs and between 20 and 50 percent in cooling costs. While the savings vary according to the site and the energy efficiency of the house, 'We've never seen an installation produce less than a 25 percent savings,' said Conn Abnee, the executive director of the GHPC, whose members include utilities, manufacturers, architects and contractors. Abnee said sales of geothermal systems are growing at about 30 percent a year, and he predicted that in five years some 10 percent of American homes with be equipped with them - a level of use that would save 300 trillion BTUs a year. A Matter of Awareness If geothermal heat pumps are so cost effective, why have homeowners been slow to buy them? In many cases, they haven't been given a choice. Builders traditionally have more of an interest in keeping construction costs low than in reducing future energy expenses.
But homeowners themselves haven't had much interest either. 'The problem has been an awareness issue,' Abnee said. 'Many times the decision-makers have not been made aware of what it is, and as a consequence they rely on what they've done for the last 30 to 40 years.' Furthermore, installing the ground loop can be messy, requiring either digging trenches or drilling wells. That's not as big an issue in new construction, where excavation is already taking place, but owners of older homes may be less willing to wreak havoc on their lawns, even if it's only temporary. The biggest objection usually is to the higher initial cost. At an average of $2,500 per installed ton of capacity (a ton is 12,000 BTUs), geo-exchange systems are more expensive than conventional equipment.
But the cost objection can disappear once a homeowner takes a look at the payback. Geo-exchange systems can pay for themselves quickly, sometimes in five years or less, and in new houses the costs - amortized over the life of the mortgage - can be more than offset by the energy savings. That was the case for Charles Burger of Wamego, Kan., who built a 2,600-square-foot house equipped with a 2.5-ton WaterFurnace geo-exchange system and a horizontal ground loop totaling 1,710 feet. The loop, buried an average of 5 feet deep, is filled with a mixture of ethanol and water, and the system can heat the house without backup at temperatures as low as minus 7° F. (Many geo-exchange systems offer conventional electric backup heat as well.) The initial cost of the entire geo-exchange system was $10,245, more than double the $4,597 expense of an equivalent natural gas furnace and electric central air conditioner. But in its first year, the system's heating, cooling and water-heating costs totaled $432, while the energy cost of conventional systems would have been an estimated $1,174. The additional $5,648 for the geo-exchange system added $31 a month to the home's 30-year mortgage. Yet it produced $62 a month in energy savings.
'This is the only technology available today that can save you energy, be friendly to the environment and pay for itself quickly in a residential application,' Abnee said. Backers of geo-exchange systems say the technology has proven reliable. The polyethylene pipe and the loop installation often come with 50-year warranties. And because the heat pumps are housed inside and aren't subjected to the extreme operating temperatures endured by conventional heat pumps installed in the back yard, there is less wear and tear on them.
'Laughing to the Bank' Sue and Bob Hurd installed a geo-exchange system when they built their new house in Elk River, Minn., in 1997. They've had no problems with it in the four years since, said Sue Hurd. They first heard of geo-exchange through an acquaintance of Bob Hurd's. A short while later, they attended the Minneapolis Home and Garden Show and visited the booth of Econar Energy Systems, also of Elk River. After a three-hour discussion, they chose a geothermal heat pump. They decided on a 6-ton Econar with a horizontal loop field for their 3,000-square-foot house. Because the system was generously sized, the Hurds need no backup heat, despite Minnesota's reputation for frigid winters. Sue Hurd has nothing but praise for how the system works.
Even keeping the temperature between 70 and 72, she said, their highest electric bill last winter was $150 a month. That compares to combined energy bills of about $400 in comparably sized houses owned by acquaintances. The Hurds calculate that they reached the payback point on their system last winter, less than four years after installation. Given their experience, Sue Hurd said, 'It really surprises us that more people don't have this kind of system. 'It's been wonderful, considering the cost of home fuel last winter,' she said.
'My husband said that we were laughing all the way to the bank.' Given all the benefits that geothermal energy offers, what will it take for more homeowners to make the switch? 'We need to get them to understand what these systems are,' said Howard Newton, applications manager for Trane Co.'s Water-Source Heat Pump unit, 'and only time will do that.'