From the ground up: Geoexchange uses Earth's energy efficientlygreenspun.com : LUSENET : Grassroots Information Coordination Center (GICC) : One Thread
FROM THE GROUND UP
Geoexchange uses Earth's energy to efficiently heat and cool homes
Saturday, July 14, 2001, ©2001 San Francisco Chronicle
Sure, we all want to cut fossil fuel use, but who wants to look at ugly forests of windmills or acres of solar panels?
Then consider a system that cuts up to 50 percent of your heating and cooling costs and is hidden from sight. Not only that, but it works night and day, rain or shine, whether it's windy or not, on the hottest days of summer and the coldest chills of winter.
A new high-tech marvel, you ask?
Yes and no. The principle has been understood for quite a while - the earliest cave-dwellers probably grasped it - but the technology to efficiently exploit this energy source has matured only recently.
The system is called geoexchange, and it's based on the fact that regardless of the weather on the surface, a few yards down the Earth maintains a stable temperature ranging between 55 degrees in northern latitudes to 70 degrees in tropical regions. On the surface an ice storm may be raging, or the sun may be scorching, but underground all is calm and comfortable.
Geoexchange systems simply exploit this geothermal energy source, extracting heat from the ground in winter and dumping excess heat back into it during summer. The equipment - a heat pump and buried pipes filled with circulating water - is straightforward. Heat pulled out of the Earth in winter is transferred into a home's standard HVAC (heating, ventilation, air conditioning) system; in summer, the process is reversed.
Geoexchange dream home
Bill Johnson and his wife Donna had already spent several years planning their dream house on the family vineyard south of Livermore when a chance meeting at a San Francisco home show led them to consider a geoexchange heating and cooling system.
Accompanied by their architect, they were researching radiant floor heating systems when they met Mike Ericksen of Earth Energy Systems, a Calistoga-based geothermal contractor. Ericksen's explanation of the concept "made a lot of sense," says Johnson, and their continuing dialogue resulted in the Johnsons hiring Ericksen to install a geoexchange system that provides all of the home's hot water, ducted cooling and radiant floor heating.
Since moving into their new home last December, the Johnsons have monitored the system during the chill of winter and the heat of summer, and have nothing but praise for both the comfort level and cost savings.
"The temperature comfort is fantastic," Johnson says, noting that the four- zone climate control for the cooling and room-by-room control of the heating allows for easy temperature adjustment throughout the 5,600-square-foot home.
Johnson also appreciates another benefit of not having a gas furnace or air conditioner: The system is much quieter than standard HVAC equipment, needing only localized fans, a pump - to distribute the cool air in the ducting and hot water through the radiant heating piping - and the heat pump/exchanger at the heart of the system.
Environmental, cost benefits
The geoexchange system was also a good fit with the Johnsons' goal of building an energy-efficient home. To cut electricity usage, they installed low-voltage lighting, eschewing energy-hog incandescent bulbs altogether. The geoexchange system completely replaces the standard energy-hungry water heater, air conditioner and furnace; the only gas appliance in their home is a cooking stove supplied by a small 10-gallon propane tank.
The system's heat pump uses electricity, of course, as does the home's duct fan, and so the Johnsons are still vulnerable to the rising cost of kilowatts. But the overall energy savings are substantial, ranging from 25 to 50 percent, depending on the current cost of natural gas and electricity.
In rural areas without natural gas service, such as the Johnsons' neighborhood outside Livermore, the alternative is propane, and the cost savings of geoexchange over propane are even higher, estimated at 60 to 70 percent.
The reductions in energy usage from geoexchange are also long-lasting; the system is warranted for 25 years, while the payback period - the time it will take for the savings to pay for the extra cost of the system over a conventional HVAC system - is between five and eight years. Given the prospect of ever-rising energy costs, that translates into as much as 20 years of savings - up to 50 percent off utility bills every month.
A long-term interest pays off
Mike Ericksen first became interested in geothermal heating and cooling back in 1977, shortly after the first big Energy Crunch in 1973-74, when the system components weren't as refined as they are now. As a mechanical contractor in Portland, Ore., Ericksen kept tabs on the nascent geoexchange industry as it grew in reliability and efficiency, observing its growing popularity in the frigid Northeastern states and Europe in the late '80s. In 1994, he sold his business and moved to Northern California to pursue his interest full time.
His firm, Earth Energy Systems, currently installs about 50 systems annually, ranging from large installations for a winery to smaller projects for homes and even an artist's studio. The technology is flexible enough, Ericksen says, to be appropriate for a wide range of settings and soil types. He has recently installed systems in small-lot, residential Palo Alto as well as in more rural North Bay settings.
How it's installed
Ericksen explains how the system is installed with the easy confidence of someone who's been through the drill many times. In this case, the drill is literal; his firm deploys specially designed rigs to drill holes 4Ç inches in diameter several hundred feet straight down.
Flexible heat-fused polyethylene pipes are then inserted into the holes, and, if the soil is sandy enough to be a poor conductor of heat, packed in with a clay-based compound. Water circulating in a closed loop through the pipes extracts the warmth from the earth for winter heating, or dumps the heat collected during summer back into the cooler ground via the heat pump/exchanger, which works much like a refrigerator.
Surprisingly, Ericksen says that rock - even hard granite - poses no installation problem. In fact, because rock is an excellent conductor of heat, it's actually preferable to loamy, sandy soils. Each rig grinds out two or three holes a day; a geoexchange system for a 2, 000-square-foot home might require six holes, where a large commercial project might need several dozen.
There's quite a bit of flexibility in where the tubing is placed; in urban residential settings, Ericksen says that the small vertical holes can be drilled right through a home's driveway. In some cases, depending on the amount of land available and the soil type, it's better and/or cheaper to dig long trenches and lay the pipes horizontally.
Ericksen says that since water is an excellent thermal conductor, he's also run the system's pipes along the bottom of large ponds or reservoirs.
The biggest challenge in urban settings can be removal of the soil extracted from the holes. If there's no place to spread the soil, it's emptied into bags and hauled off. The one topology that can limit installation options is a hillside; although it's generally possible to put a system in even on a sloping lot, the cost may be higher than a flatland project.
Seismic and cost factors
While the systems he's installed have yet to be tested by a major earthquake, Ericksen is confident that the rugged heat-fused joints of the flexible tubing he installs will remain intact. If a house shifts off its foundations, then any ground-to-house connection may well snap. But even in that worst-case scenario, Ericksen points out that the only substance in a geoexchange system is clean water, posing no hazard.
The cost of a geoexchange system that takes care of all the hot water, heating and cooling needs in a 2,000-square-foot home is around $20,000 to $25, 000, or roughly $10,000 more than a high-efficiency conventional HVAC setup. This additional capital investment may give some homeowners pause, but Ericksen reports that most of his customers "have done their homework," selecting geothermal only after weighing all the environmental, energy- reduction and cost factors.
Because the geothermally heated and cooled home is virtually all-electric, with only a stove possibly running on gas, owners may need to contact their utility companies to adjust their electrical and gas baselines.
The bigger picture
The environmental benefits of geoexchange systems are obvious: Less burning of fossil fuels means cleaner air, fewer greenhouse emissions and less demand for energy, both globally and locally. Public resources are now focused on huge natural-gas-powered plants capable of supplying the electrical needs of tens of thousands of homes. Imagine if this same electricity could be replaced by thousands of small-scale, completely invisible geoexchange systems in homes, schools and small businesses.
Ericksen says that geoexchange systems also offer a significant advantage for utilities. Unlike conventional air conditioners, which must work harder to overcome rising temperatures outside, creating peak-demand spikes in the power grid, geoexchange systems don't require any more juice in the hottest hours of the day than they do in the morning. Where a standard AC unit struggles to transfer the heat from the interior into the blistering air outside, the geoexchange system is sending that heat down into the constant cool "heat sink" of the earth.
So Earth to California: It's time to wake up to the fact that geoexchange systems are hot - and cool.
Some geoexchange advantages
-- Around 50 percent savings on utility bills, plus possibility of further rebates from your utility.
-- Superior reliability to conventional heating/cooling systems.
-- Longer life - no parts to rust or corrode.
-- Safer - no carbon monoxide or possibilities for combustion. No risk of explosion after an earthquake.
-- Quieter than conventional heating/cooling systems.
-- Better able to maintain a constant temperature in the home.
-- More ecological - Earth's existing geothermal energy is utilized.
-- Lower humidity in summer.
-- Higher humidity in winter.
For more information, visit www.earthenergysystems.com or www.geoexchange.org, the Web site of the Geothermal Heat Pump Consortium, Inc., 701 Pennsylvania Ave. N.W., Washington, D.C. 2004; (202) 508-5500.
©2001 San Francisco Chronicle Page WB - 1
-- Swissrose (firstname.lastname@example.org), July 15, 2001
I worked for a company, McQuay International, that has made ground- source heat pumps for years. They are the most efficient heating/cooling units made. They just need electricity to power a fan and a compressor.
They also make air-to-air heat pumps and air-to-water heat pumps. These are only good for heating to about 30 degrees F. 50 degree earth will heat just fine all winter long.
-- John Littmann (email@example.com), July 17, 2001.