My long and winding path through the selection of the best heating and cooling system began six months ago and culminated with the selection of a geothermal system, which is right for us for so many reasons.
Kimberly Lancaster | greenlifesmartlife
Day 1 of Geothermal: Why We’re Doing It
When I mentioned to my parents (among others) that we were installing a geothermal system in our new house, they had blank stares. “What does that mean?”
My long and winding path through the selection of the best heating and cooling system began six months ago and culminated with the selection of a geothermal system, which is right for us for so many reasons.
The process I went through was extensive and included everything from a tour of the Viessmann US headquarters located here in RI to interviewing the top HVAC (heating venting and air conditioning) installers in the state. I analyzed the cost to own both for the short and long term, the carbon emissions, the fossil fuels and the overall equipment impact – even the landscaping needs of both systems. I have to say thanks to Hazard Stewart at Newport Geothermal of Newport, RI for his patience, education and incredible graciousness in standing with me in 50 mph winds and freezing temperatures as I questioned and questioned him on the system. I also owe an incredible thank you to the team of Jeanne and Dennis Reddy at Reddy Piping of Narragansett, RI who designed and installed the interior portion of the system including all of the ductwork, piping, tanks and EVRs for a HVAC system. The system, on its blower test, scored an impressive > 2% leakage rate in zones 3 & 4 of the house! (Note: Zones 1 &2 had a wet glue issue and zone 5 is cooling only and wasn’t in yet.)
Today’s post is the first in a four-part series on why we chose geothermal and what it is. Tomorrow is a list of FAQs accompanied by the first round of photos to help readers understand what the equipment looks like and what it takes to install a geothermal heat pump. Part three will run on Thursday and, along with more photos, will cover the drilling of the well. Friday I am going to share my cost analysis graph including our upfront costs, comparison cost to gas and oil systems, payoff time and our tax rebates. I don’t have all the numbers yet but when I do I will share the impact of the system on our HERS rating, our ENERGY STAR score and ultimately how many LEED points it helped us get.
One of the top reasons we selected a geothermal system is that it will rely primarily on the Earth’s natural thermal energy, a renewable resource, to heat or cool our house. Geothermal exchange systems work on a different principle than an ordinary furnace/air conditioning system. Furnaces must create heat by burning a fuel–typically natural gas, propane, or fuel oil. With geothermal systems, there’s no need to create heat, hence no need for chemical combustion. Instead, the Earth’s natural heat is collected in winter through a series of pipes, called a loop, installed below the surface of the ground in a well expected to run 800 feet deep in our case. Water circulating in the loop carries this heat to the home. A geothermal system then uses electrically-driven compressors and heat exchangers in a vapor compression cycle–the same principle employed in a refrigerator–to concentrate the Earth’s energy and release it inside the home at a higher temperature. (A temperature, I might add, that is significantly cooler than the hot, dry air found in boiler systems that most people find too hot when blowing and incredibly drying.)
In summer, the process is reversed in order to cool the home. Excess heat is drawn from the home, expelled to the loop, and absorbed by the Earth. Geothermal systems provide cooling in the same way that a refrigerator keeps its contents cool–by drawing heat from the interior, not by injecting cold air. A refrigerator transfers heat in only one direction. A geothermal heat pump can transfer heat in two directions, thereby heating or cooling the space. Most heat pumps heat or cool the air. Some heat pumps heat or chill water. An additional component, a reversing valve, is added to a heat pump, which allows the refrigerant to change direction, allowing the space that was being cooled to be heated.
A geothermal heat pump has a compressor, a condenser, an expansion device and an evaporator like a refrigerator; but also includes a reversing valve to allow both heating and cooling. The big difference between a refrigerator (or traditional AC) and a geothermal heat pump is the way heat is transferred. A geothermal heat pump transfers heat between the refrigerant circuit and the ground instead of between the refrigerant circuit and the air. The ground is a much milder heat source, since temperature changes very little over the course of the year. The outside air temperature, however, varies significantly over the year, making a geothermal heat pump much more energy efficient that a traditional air conditioner. A geothermal heat pump compressor also operates at lower pressures because of the milder heat source/heat sink (the ground), helping provide longer life expectancies.Our system has been set up with dual domestic hot water tanks, one of which is a holding tank that stores additional hot water for when we need it whether that is for heat or hot water.
All of our equipment is in for the interior part of the project (see pictures). You’ll see the dual Rheem Marathon hot water tanks, two of the air handlers for the house (the first and second floor) and the unit for the wine cellar. You’ll see all of our ductwork is sealed with cement and insulated to an R-6 for the greatest performance and efficiency of the system. The piping then runs our through a hole cored in the foundation and back to the ground source heat pump connected to our closed loop system and our well.
The well and exterior piping takes approximately four days to install so each day the rest of this week we have a new story and new photos posting on the project. Wish us luck, we start at 9 AM eastern time Tuesday with final location and the digging of the slurry pit.
Day 2 of Geothermal: Frequently Asked Questions
Deciding to go with a geothermal system over the gas fired boiler was an education process. I really had to understand how it worked. I struggled at first with the concept of heating a home from a constant lower temperature and cooling a home by removing hot air as opposed to adding cold air. There were so many new terms and lots of new vernacular for me to grasp, so I started a list of FAQs that helped me understand each of the parts of the system. We’ve included our own photo display to accompany this blog so it helps put it into perspective.
This is part of our effort to lower our home’s operating costs over its lifecycle.
FAQs
Q: What is a geothermal heat pump?
A: A geothermal or “ground-source” heat pump is an electrically-powered device that uses the natural heat storage ability of the earth and/or the earth’s groundwater to heat and cool your home.
Q: How does it work?
A: Like any type of heat pump, it simply moves heat energy from one place to another. Your refrigerator works using the same principle. By using refrigeration, the geothermal heat pump removes heat energy stored in the earth and/or the earth’s groundwater and transfers it to the home.
Q: How is heat transferred between the earth and the home?
A: The earth has the ability to absorb and store heat energy. To use that stored energy, heat is extracted from the earth through a liquid medium (in our case, water) and is pumped to the heat pump heat exchanger. There, the heat is used to heat your home. In summer the process is reversed and indoor heat is extracted from your home and transferred to the earth through the liquid.
Q: You mentioned heating and cooling. Does it do both?
A: One of the things that makes a heat pump so versatile is its ability to be a heating and cooling system in one. You can change from one mode to another with a simple flick of a switch on your indoor thermostat. Plus, a geothermal heat pump can assist in heating hot water year-round.
Q: Do I need separate ground loops for heating and cooling?
A: No. The same loop works for both. All that happens when changing from heating to cooling, orvice versa, is that the flow of heat is reversed inside the unit.Q: What types of loops are available?
A: There are two main types: open and closed. We’re installing a closed loop system
Q: Does the underground pipe system really work?
A: The buried pipe, or “ground loop”, is the biggest technical advancement in heat pump technology to date. The idea to bury pipe in the ground to gather heat energy began in the 1940s. But it’s only been in the last twenty-five years that new heat pump designs and improved pipe materials have been combined to make geothermal heat pumps the most efficient heating and cooling systems available.
Q: What is a closed-loop system?
A: The term “closed-loop” is used to describe a geothermal heat pump system that uses a continuous loop of special buried plastic pipe as a heat exchanger. The pipe is connected to the indoor heat pump to form a sealed, underground loop through which water or an anti-freeze solution – depending on where you live – is circulated. Unlike an open-loop system that consumes water from a well, a closed-loop system continuously circulates its heat transferring solution in pressurized pipe.
Q: Where can this loop be located?
A: That depends on land availability and terrain. Closed-loops are trended horizontally in yards adjacent to the home if the yard is large enough. Or, for smaller yards, the loops can be installed vertically using a drill rig, much like a water well installation. We are installing vertically and expect our well to go as far as 800 feet deep to reach water.
Q: How deep and long will my horizontal trenches be?
A: Trenches are normally four to six feet deep [1/2 – 1.8 meters]. One of the advantages of a horizontal loop system is being able to lay the trenches according to the shape of the land. As a rule of thumb, 125-300 feet of trench are required per ton of heat pump capacity [11-27 meters per kW of capacity].
Q: How many pipes are in a trench?
A: Anywhere from 1 to 6 pipes pre trench may be used, depending upon the optimal design for the yard. More pipe per trench shortens the total amount of trench required.
Q: What if I don’t have enough room for a horizontal loop?
A: Closed loop systems can also be vertical. Holes are bored to about 150 – 300 feet per ton of heat pump capacity [13 – 27 meters per kW of capacity]. U-shaped loops of pipe are inserted in the holes. The holes are then back-filled with a sealing solution (grouting material).
Q: How long will the loop pipe last?
A: Closed-loop systems should only be installed using the appropriate high-density polyethylene pipe. Properly installed these pipes will last over 50 years. They are inert to chemicals normally found in soil and have good heat conducting properties. PVC pipe should not be used under any circumstances.
Q: How are the buried pipe sections of the loop joined?
A: The only acceptable method to connect pipe sections is by thermal fusion. Pipe connections are heated and fused together to form a joint stronger than the original pipe. Mechanical joining of underground pipe for an earth loop is never an accepted practice. The use of barbed fittings, clamps and glued joints is certain to result in loop failure due to leaks.
Q: Will an earth loop affect my lawn or landscape?
A: No. Research has proven that loops have no adverse effect on grass, trees or shrubs. Most horizontal loop installations use trenches about 3 feet [1 meter] or less wide. This, of course, will leave temporary bare areas that can be restored with grass seed or sod. Vertical loops require little space and result in minimal lawn damage.
Q: Can I reclaim heat from my septic system disposal field?
A: No. Depending upon your geographic location, an earth loop will reach temperatures below freezing during extreme conditions and may freeze your septic system. Such usage is banned in many areas.
Q: Can I use water from my geothermal well for other applications?
A: It depends. You cannot in most states, including RI, use the same well for heating and for your drinking supply. You can however, divert water externally to fill a rainwater harvesting tank, as we are doing in our home. When the float in our tank gets too low, it will call to the well for a refill. This will allow us to use only our well water and our rainwater supply for irrigation, not municipal water will be used at all.
Q: If the loop falls below freezing, will it hurt my system?
A: No. The antifreeze solution used in loops that operate at low temperatures will keep it from freezing down to about 15F [-9C] fluid temperature. In the U.S. and Canada, three types of antifreeze solution are acceptable: propylene glycol, methyl alcohol, and ethyl alcohol. Some states/provinces may require one type over another.
Q: I have a pond near my home. Can I put a loop in it?
A: Yes, if it’s deep enough and large enough. A minimum of 8 – 10 feet [2.5 0 3 meters] in depth at its lowest level during the year is needed for a pond to be considered. In pond loops, polyethylene pipe must be used. Generally, a minimum of ½ acre [0.2 hectare] pond is required to provide adequate surface area for heat transfer.
Q: Can a geothermal heat pump also heat water for my home?
A: Yes. Using what’s called a Hot Water Generator (HWG), some types of geothermal heat pumps can save you up to 50% on your water heating bill by pre-heating tank water. We installed the Geothermal Superheater for a mere $400.
Q: Is a geothermal heat pump difficult to install?
A: Most units are easy to install, especially when they are replacing another forced-air system. They can be installed in areas unsuitable for fossil fuel furnaces because there is no combustion, thus, no need to vent exhaust gases.
Q: Do I need to increase the size of my electric service?
A: Geothermal heat pumps don’t use large amounts of resistance heat, so your existing service may be adequate. Generally, a 200-amp service will have enough capacity, and smaller amp services may be large enough in some cases. Your electric utility or contractor can determine your service needs.
Q: How efficient is a geothermal heat pump?
A: Geothermal heat pumps are 3.5 – 5 times as efficient as the most efficient fossil fuel furnace. Instead of burning a combustible fuel to make heat, they simply move heat that already exists. By doing so, they provide 3.5 – 5 units of energy for every unit used to power the heat-pump system.
Q: What about comfort?
A: In winter, a geothermal heat pump system moves warm air (90 – 105F) throughout your home via a standard duct network. Typically, a very even comfort level is found throughout the home. This is because the warm air is moved in slightly higher volumes and, therefore, saturates the home with warmth more evenly. This even helps out hot or cold spots and eliminates the hot air blasts common with fossil fuel furnaces.
In summer, cool, dehumidified air is dispersed through the same duct network.
Q: Can I get a tax credit for installing this system?
A: It depends on where you live. Some states do have tax credits for installing geothermal systems. There are federal tax credits for 2009 and 2010.
Day 3 of Geothermal: Installation, Well Drilling and a Look at Equipment
Installing a geothermal system is a massive coordination. In addition to the homeowner (coordinated all of these people and negotiated pricing), the project has included: the Geothermal company (all equipment and specs, overseeing it all), the well driller (the well), the excavator (trenches and backfill), the plumber (piping and connections, domestic hot water tank), the HVAC installer (duct work, blowers and all related interior vents, EVRs, etc), the electrician (wiring it all up), the landscape architect (making the well look nice), the civil engineer (location) and the Green Rater (LEED).
Here’s a photo gallery of our project the past three days.
Here’s our slurry pit. That’s clean water running out. We had to dig two pits, 15 feet deep by ten feet wide to collect any water overflow. It just figures but our well was pumping water faster than the ground wanted could absorb it.
Here’s the well rig.
That’s Hazard Stewart, he owns Newport Geothermal. Hi Hazard!
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That’s me, Kim (the owner) looking worried about the noise and disturbing her neighbors. All went well though, not a single complaint. All that preparation paid off!
I admit, I was also worried about the term slurry pit.
That’s the well. We dug to 1,000 feet in just two days.
Here is where we hit water. The well was “making” very little water at 300’, the same till about 800’, about 1.5 gpm. The well driller achieved 8-10 gpm at a 1000’. Basically, we have a very good well for geothermal; and very little bleeding of the well water to the drywells will be required. Furthermore, the added water that we found around 800’ will allow for some irrigation.
That’s the water source heat pump being installed. The well pump will also go into the basement but that is next week. The connections and final trenching is scheduled for next week.
The trench to the house will be dug on Friday and we’ll do another quick post showing the final connections. We also have our next blower test for LEED and ENERGY STAR on Thursday June 11th and we’ll make sure all the connections are tight. We’re going for a <.4 leakage rate.
That’s it. We have our system. Check out our Photo Gallery for more great shots of the Geothermal system being installed!
Day 4 of Geothermal: What Does a Geothermal System Cost?
The most popular question I am asked in building a green home is “what does it cost?” Everyone makes the immediate assumption that it will always cost more to go green. Our geothermal system has proven this theory wrong.
A geothermal system for the home will cost more upfront than if you bought a separate forced-air gas-fired or oil-fired furnace and central air conditioning system, but not as much as you might think. Out initial outlay is going to NET around $6k more upfront than comparative systems but will cost us less after our tax rebates and the system offers long term savings for us as well.
One of the greatest advantages of our geothermal system is its ability to lower the monthly out-of-pocket expense for the life cycle of our house. The current trend of lowering a home’s operating costs is one that is only going to continue. As the U.S. looks to build a smart grid over the next ten years and increase our renewable energy supplies, geothermal systems will be a key element in making a home comfortable and efficient.
In our cost analysis we compared three systems covering approximately 4500 sq/ft:
System A: Five-zone hydro air heating (85% efficient) and cooling system (11 EER) using oil boiler and tankless on demand water tanks and dual Environmental Recovery Ventilators (ERVs) COST: $118,750.00
System B: Five zone Viessman hydro air heating (95% efficiency) and cooling system (13 EER) using propane gas boiler and two 85-gallon domestic hot water tanks and dual ERVs COST: $129,200.00 (NOTE: We do not have natural gas in our neighborhood, we had to look at propane, this was an added cost to this system both upfront and in the long run. That said; oil was never an option for us. We did look at radiant heat as well but the cost increase was significant.)
System C: Five zone Geothermal hydro air heating (3.5 COP (this is equivalent to a 99% efficiency rating)) and cooling system (16.9 EER) using ground source heat pump, dual EVRs and a Superheater COST: $135,501.00
If you are looking into this for your home, to get an accurate comparison of the costs, I also suggest you consider the following:
- Payback, or how long it takes to recover the difference in costs between the two systems using energy savings. Payback for most geothermal heat pump systems runs three to five years. We have no payback time once we get our tax credit.
- Energy efficiency of the two systems. To get an accurate picture, make sure efficiency claims are substantiated. Your lifestyle and how well your home is insulated affect how economical a system will be. Our geothermal system has a 3.5 COP and 16.9 EER, this is higher than any competitive system on the market, so we are also getting higher efficiency for less money.
- Total operating savings from heating, cooling and domestic hot water must be combined to get an accurate picture of total energy savings. (See our table.)
- Energy costs and availability, both present and future. (We didn’t use this for payback because we didn’t need to, but you can safely assume a 4% rise in oil and gas and 2% for electricity.)
- Maintenance costs and system reliability. (We have a 2 year parts and labor warranty. And the system maintenance is equivalent to that of any boiler.)
- System lifespan – with a 25 year expected lifespan
- Other uses, in our case we are tapping into the geothermal well to fill our rainwater harvesting tank when it is low. This completely eliminates the need for our irrigation system to use municipal water.
If you look at the three systems outlined in TABLE 1.0 you can see the heating source, the cost per unit for installation. You can also see the listing for the cost of the plumbing system for each since it impacts domestic hot water. TABLE 2.0 then takes what you spend per year on oil or gas and then compares it to the geothermal system for heating, cooling and DHW. The annual cost to run the geothermal system is averaged at nearly $5k per year less than a propane gas system.
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TABLE 1.0
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GEOTHERMAL
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PROPANE GAS
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PROPANE GAS WITH RADIANT
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OIL
|
|
EQUIPMENT AND DUCTWORK
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$91,280.00
|
$98,350.00
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$128,200.00
|
$92,850.00
|
|
DHW/PLUMBING
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$23,500.00
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$25,900.00
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$25,900.00
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$25,900.00
|
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EXCAVATION
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|
|
|
|
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TRENCHES
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$480.00
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$450.00
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$450.00
|
|
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WELL
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$20,241.00
|
|
|
|
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GAS TANK
|
|
$4,500.00
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$4,500.00
|
|
|
SUB TOTAL
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$135,501.00
|
$129,200.00
|
$159,050.00
|
$118,750.00
|
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REBATES
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|
|
|
|
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STATE
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$1,750.00
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|
|
|
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FED
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$40,650.30
|
|
|
|
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ENERGY STAR
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$500.00
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$500.00
|
|
|
|
REBATES SUBTOTAL
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$42,900.30
|
$500.00
|
|
|
|
TOTAL SYSTEM
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$92,600.70
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$128,700.00
|
$159,050.00
|
$118,750.00
|
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DIFFERENCE VS GEOTHERMAL
|
|
$36,099.30
|
$66,449.30
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$26,149.30
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|
|
|
|
|
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TABLE 2.0 ANNUAL COSTS
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GEOTHERMAL
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PROPANE GAS
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PROPANE GAS WITH RADIANT
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OIL
|
|
HEAT
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$3,129.00
|
$8,376.00
|
$8,376.00
|
$5,597.00
|
|
COOL
|
$331.00
|
$466.00
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$466.00
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$509.00
|
|
HOT WATER
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$367.00
|
$970.00
|
$970.00
|
$648.00
|
|
SUBOTOTAL OF WHAT THE SYSTEM COSTS ANNUALY TO RUN
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$3,827.00
|
$9,812.00
|
$9,812.00
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$6,754.00
|
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GEOTHERMAL ANNUAL SAVINGS COMPARED TO GAS/OIL
|
|
$5,985.00
|
|
$2,927.00
|
As noted, we also have substantial tax rebates. According to the language, the Geothermal System is defined as a system that produces and stores energy to heat buildings, cool buildings or produces hot water. Our system does all of these things so our deductions include 30% federal (which totals all materials, equipment and labor) and 25% state (capped at an assumed max system cost of $7000, so this is a $1750 state rebate), plus our ENERGY STAR rebate on the total cost of our system. This totals $42,900 (approximately) and can be carried to following years on our federal returns if unused.
So in looking at what we paid, the initial upfront cost was $6301 higher, but with our tax rebates it is easily the least expensive system. We also save $5985 estimated per year on costs for fuel and to run the system. We will never have a bill for oil or natural gas. We will have a system that does not fry and dry my homes air, it will be comfortable. We have a system that eliminates the need to use municipal water for our landscaping but backs up our rainwater harvesting system. And finally, our family will eliminate 19.6 tons of carbon dioxide from entering the atmosphere annually.
If you are looking to build new or replace a system, geothermal is an excellent option. You can easily add solar thermal and PV to the system as well, all option we are including in our long term path once we put money back in our savings account.
The content & opinions in this article are the author’s and do not necessarily represent the views of AltEnergyMag
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