Geothermal Heating: An Option for Maine Homeowners?
Thursday, February 07, 2013 7:17 AM
"Maine citizens are nearly 80 percent dependent on oil to heat their homes and are increasingly vulnerable to rapid price escalations, fossil fuel supply curtailments and infrastructure disruptions," states a 2011 report from the Governor's Energy Office (formerly known as the Governor's Office on Energy Independence and Security) titled Residential Geothermal Heating and Cooling Systems in Maine. "In addition, combustion of fossil fuels for heating purposes damages the environment, threatens public health and undermines the state's economic vitality."
Bill Morgner of Midcoast Energy Systems in Damariscotta demonstrating how the company’s geothermal heating system works.
In the same report, the LePage administration stated its intent to offset this trend by throwing its support behind a renewable heating source that is right beneath our feet -geo-
thermal. Often when we think of geothermal heating, we picture energy that is harvested deep within the earth where volcanic activity rises near tectonic plate boundaries. However, even in Maine, by using a ground source heat pump, heat can be extracted from up to 1,000 feet down, where stored energy from the sun keeps the temperature at a steady 45 to 50 degrees. This "solar battery" can be used to not only heat, but also to air condition, a building.
Martin Orio, president of the New England Geothermal Professionals Association, describes the geothermal heat pump as a "solar energy management device," which acts very similarly to a refrigerator.
"We don't make the inside of the refrigerator cold, we remove the heat from it," said Orio at a recent presentation sponsored by the Environmental and Energy Technology Council of Maine (E2Tech). "So think of the inside of the refrigerator like the earth underground. In the wintertime, we use the geothermal heat pump to take stored solar energy out of the ground. In the summertime, we use the heat pump in the other direction to take unwanted solar gain and store it under the property."
Geothermal heating has been available in Maine since the 1970s, and in recent years more and more companies have offered installation services. It's estimated that currently there are over 500 residential geothermal installations in the state, while it has been most commonly installed in large commercial and public facilities, including Camden Hills Regional High School and Knox County Regional Airport.
Although the system requires a substantial upfront cost, according to the Environmental Protection Agency (EPA), geothermal systems can save 30 to 70 percent in heating costs and 20 to 50 percent in cooling costs compared to conventional systems. Those numbers are reflected in the basic equation for geoexchange systems, which requires only one unit of electric energy to power the heat pump which compresses four units of energy from the earth into heat. Unlike electric resistance heaters, which convert kilowatts to heat, and furnaces, which make heat by burning fuel, geo-thermal systems don't create heat. As the GeoExchange Association, the geothermal heating industry's trade organization, explains, they merely "collect, concentrate, and distribute it."
Also, depending on whatever power source is producing the homeowner's electricity, geothermal is potentially carbon neutral. Since the electricity used is a refrigeration load, it does consume a fair amount of power, but geothermal has been found to cut carbon emissions substantially. According to GeoExchange, with over 750,000 geoexchange systems installed in the U.S., it is equivalent to reducing the importation of over 16.1 million barrels of crude oil per year or taking 971,000 cars off the road.
Open- and Closed-Loop Systems
The geothermal system is made up of three elements, including the piping which is laid in the ground (i.e., "earth coupling"), the heat pump inside the house, and the distribution system.
There are different methods of extracting the heat from the ground, but geoexchange systems, like air conditioners and refrigerators, all involve moving the heat from the ground through a vapor-compression refrigeration cycle in the heat pump. There are two basic types of earth coupling - the closed loop and the open loop. For closed loops, the pipes can either be buried horizontally in four-foot trenches spread out across the property or in deeper vertical holes if there isn't enough land. Water and the antifreeze solution is then circulated through the pipes. A conductive heat exchange is made through the plastic wall in the pipe, which is grouted with bentonite, through the circulation of the solution. In the summer, the energy flow is reversed. Closed loops can also be run through the bottom of a pond or other small body of water.
Last year, Midcoast Energy Systems in Damariscotta, an installer of geoexchange systems, installed a vertical closed-loop system for their buildings. According to company president Bill Morgner, this involved drilling two 400-foot wells to accommodate the 60,000 BTUs (British thermal units) needed to heat and cool the 7,000-square-foot facility. According to GeoExchange, the average house requires between 30,000 and 42,000 BTUs per hour to heat and cool.
Unlike the closed-loop systems, which circulate the same solution over and over, open-loop systems use groundwater pumped from an aquifer, which is then circulated through the heat pump's heat exchanger where the heat is compressed to heat and cool. The water is then discharged back into the ground. Open-loop systems are reportedly more efficient than closed-loop systems because they don't have to make a thermal exchange through a plastic wall, but water quality issues can pose a problem.For the Average Homeowner?
George Terrien, a Rockland architect, is now in his ninth year with an open-loop geoexchange heating system. On a blustery, snowy afternoon he invites me into his renovated 1850 farmhouse on Broadway. The radiant heating in the floors is on, and the air inside is well ventilated and warm. Terrien does not supplement the system with any other heating source. There are just the three heat pumps in the basement, though he only uses one unless the temperature drops too low and then another one comes on. With one 425-foot well, he is able to heat and air condition 5,000 square feet. Terrien says he decided to use his farmhouse as an experiment to determine whether it would make more environmental and economic sense to renovate old Maine homes or simply demolish them and start over.
"As an architect, I've always concentrated on being environmentally aware," explains Terrien. "If it didn't make sense to refurbish an old house, then I'd want to tell my clients."
Terrien emphasizes the importance of using "aggressive energy conservation measures" before installing geothermal. After tightening up his home using state-of-the-art weatherizing techniques, Terrien finally hooked up his geoexchange system in November 2003.
"I used geothermal because the science is absolutely sound," says Terrien. "The technology is off the shelf, and any mechanic who can keep a system going in a convenience store can work on the heat pumps here."
After nine years, Terrien says he's very pleased with the heating system, which has not only provided heating and cooling for the house, but also cheap hot water. From an energy-efficiency standpoint, Terrien says that he's decided that upgrading old homes, which are the least energy efficient, makes more sense than tearing them down and starting over. According to his calculations, it would take half the oil in Prudhoe Bay, Alaska, just to demolish and replace all of such houses in the U.S.
Costs & Cautions
By far, the biggest drawback to geothermal heating is simply the cost, which usually ranges from $25,000 to $30,000, mostly because of the siting, surveying and drilling of the ground loops. However, due to the superior efficiency of geothermal systems, according to the Department of Energy, homeowners can recoup their initial investment within 10 years. As part of the American Recovery and Reinvestment Act of 2009, there is currently a 30-percent federal tax credit for qualified geothermal heating systems installed until December 2016. Often, homeowners finance the installation through a mortgage.
Terrien says the best way to calculate costs of a geoexchange system is by figuring in the debt service of the loan, along with the maintenance costs (such as flushing the coils yearly), eventual replacement of the heat pump, and then the cost of electricity to run the system. Then you divide that amount by the amount of oil you would have used. If the number is less than the price of fuel oil (currently around $3.60 a gallon), then you're making money. By Terrien's calculations, he's paying the equivalent of $1.38 a gallon of fuel. Using a formula that includes a 3-percent annual rise in electricity costs compared to a 5-percent increase in fuel oil, based on historic prices, along with a 5-percent interest rate on a loan, Bill Morgner of Midcoast Energy estimates that the average homeowner can save up to $60,000 after 20 years.
However, Terrien strikes a cautionary tone when it comes to recommending geothermal to others. Depending on the house and the soil conditions, every residence is different in terms of what that investment will be.
"If a client says, 'I want to do geothermal,' I'll say, 'Don't do it expecting to be able to budget how much it's going to cost," says Terrien. "Do it the same way you would buy a BMW or a pool or granite countertops. Do it because you're committed to wanting to do it."
Knox County Regional Airport Manager Jeff Northgraves says it's also important to remember that geothermal heating systems are more electronically complex than a conventional furnace or boiler.
"For anybody who is putting [geothermal] in, my advice is to make sure you get the follow-on preventive maintenance and agreements in place so that you have folks who are familiar with geo-
thermal systems and the electronic controls that go with them," says Northgraves.
Another common complaint about geoexchange systems is that some have not performed as advertised, which is why industry specialists stress the importance of proper installation. According to Orio, of the Geothermal Professionals Assoc., often systems have failed because either they were improperly installed or the contractor undersized the earth coupling, which leads some homeowners to supplement the geothermal with less-efficient resistance heaters.
"The biggest problem I see is that when we rate these units, we rate them based on the deltas of temperature in a laboratory environment that are supposed to mimic what's out in the field, and they do when they're applied properly," says Orio. "If you're interested in getting it done right, you're going to pay attention to those deltas of temperature and pressure."
The Future of Geothermal
Despite incentives to encourage homeowners to adopt geo-
thermal heating, such as various state-subsidized loan programs, Efficiency Maine Executive Director Michael Stoddard says that Mainers have not taken advantage of the technology.
"Geothermal has been a challenge," said Stoddard.
The long-term nature of the cost savings can be a real obstacle for cash-strapped homeowners.
"Most consumers in Maine shop price and are unaccustomed to shopping value, and are even less accustomed to shopping value over time," the Governor's Energy Office report quotes Tom Myette, co-owner of Newcastle geothermal installer Midnight Energy.
As an alternative, Terrien of Rockland has touted the idea of a "neighborhood approach" to bringing geothermal to developed areas of the region. Rather than each house putting in their own individual geoexchange system, a neighborhood could get together and create a public utility that sources geothermal heating.
In spite of the barriers to geothermal, Terrien does believe that the technology will eventually pass the early adopter stage and become a mainstream option for homeowners.
"There's no question in my mind that we'll get there," he says. "It's a very effective way to transform electrical energy into extraction of heat and it's very low-grade heat because you don't have to heat it up much."