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Building Science

Is a Ground-Source Heat Pump a Renewable Energy System?

Grouping ground-source heat pumps with solar water heaters and photovoltaic systems for tax credits has led to confusion

Image 1 of 2
A vertical well for a ground-source heat pump.
Image Credit: Energy Vanguard
A vertical well for a ground-source heat pump.
Image Credit: Energy Vanguard
Diagram of the refrigeration cycle
Image Credit: Energy Vanguard

Here’s another rant that goes in my “drives me crazy” bin of articles. I’m in good company, too. Another article that ran at Green Building Advisor recently discussed making the choice between an air-source heat pump and a ground-source (a.k.a. “geothermal”) heat pump. At the end of the article, Peter Yost mentioned that ground-source heat pumps,“have been given quite the green ‘pass’ or ‘seal of approval’ because they are portrayed as using a ‘renewable’ energy source, and that makes me crazy.”

So there’s your answer to the question I asked in the title: No! Ground-source heat pumps are not a renewable energy source. Let’s all go out and have a productive day now.

Can a heat pump be classified as an energy source?

OK, I’ll say a bit more. Remember that article I wrote about how your air conditioner works? And the one before that about how air-source heat pumps get heat out of cold air to heat your home in winter? A ground-source heat pump does exactly the same thing, with one difference.

In an air-source heat pump or air conditioner, you’re pulling heat from the outside air and putting it into the home (heating mode) or putting heat from the home into the outside air (cooling mode). The diagram below shows what’s going on. The heat exchange with the outside is going on in the part labeled as the condenser coil. In an air-source heat pump or air conditioner, that coil surrounds the noisy metal box that sits outside your home. The fan inside the condensing unit pulls outdoor air across that coil, and the refrigerant running through the coil either gives up heat to the outside (cooling mode) or picks up heat from the outside (heating mode).

The only substantial difference with a ground-source heat pump is that you’re using the ground (or a body of water) instead of the outside air. The heat exchanger in a ground-source heat pump isn’t a coil but a loop of pipe carrying the working fluid. That loop of pipe can be horizontal or vertical (see the photo of a well, above), but its job is simply to exchange heat with the ground. It’s doing the job of the condenser coil above. (Actually, there are two closed loops and three heat exchanges going on, but I’ve taken the liberty of simplifying the process here, which doesn’t change anything regarding our original question.)

I’ve focused on air conditioners and heat pumps here, but the same analysis applies to refrigerators, which are just another kind of heat pump that uses the refrigeration cycle. All of these need an input source of energy to run the refrigerant through the system. In an air-source heat pump, you also need a blower to move air across the evaporator coil and through the duct system and another fan in the condensing unit. In a ground-source heat pump, the fan in the condensing unit is replaced with a pump for the working fluid in the ground loop.

So, is a refrigerator a renewable source of energy?

A poor choice of terminology

I think the main source of the confusion about ground-source heat pumps and renewable energy is the unfortunate use of the term “geothermal” in connection with these devices. When you hear the word “geothermal,” you think of lava or geysers, of volcanoes blowing their tops. You think of beautiful Icelandic maidens in steaming pools of hot water surrounded by snow. (Or is that just me?) You think of heat engines being driven and doing useful work by harnessing the heat from within the earth.

But that’s not what ground-source heat pumps are or do. They’re just like your regular air conditioner or heat pump except they use the ground instead of the air as the source or sink for heat. They still use electricity to power the pump that moves the working fluid through the loops. They still use electricity for the blower that moves the air through the duct system. They’re still using even more electricity to run the compressor, which is the pump for the refrigeration cycle. All that electricity generally comes from outside the home, often from a power plant that burns coal or natural gas. The last I heard, most folks don’t consider those fuels renewable.

Ah, but now that you mention Iceland, Allison, I hear you thinking, isn’t a ground-source heat pump doing the same thing they do when they pump heat from their numerous hot springs and use it in buildings? They’re using pumps to move the heat, too, just like a ground-source heat pump does? Well, yes and no. It appears at first to be the same thing, and we do indeed call the heat they’re using a “renewable” source of heat. The difference, though, is that they’re pumping high-grade heat that comes in at a temperature high enough to be used directly. They don’t have to “concentrate” it through the use of a refrigeration cycle as a ground-source heat pump does.

I don’t use the term “geothermal heat pump.” It’s too confusing. Even Thomas Friedman, the columnist for the New York Times who’s written some well-received books about the environment, is confused about this. He wrote in a column a few years ago that he’s using renewable energy in his home because he installed a “geothermal” heat pump.

Really now. If a ground-source heat pump is a renewable energy source, then so is a refrigerator. Can you see why this drives me crazy?

Allison Bailes of Decatur, Georgia, is a RESNET-accredited energy consultant, trainer, and the author of the Energy Vanguard blog.

72 Comments

  1. Shane Claflin | | #1

    active or passive
    A passive system utilizes existing heat. In an active system, heat is generated. Passive is a more accurate term for something that is "renewable". The heat pump would be renewable if powered by a solar PV system. minus the refrigerant as a pollutant.

  2. Aj Builder, Upstate NY Zone 6a | | #2

    Shane, pollutant? So is the
    Shane, pollutant? So is the rest of the machine then, the metal, the PVC plastic covered wiring. Doesn't matter what label you "actively" attach. The least polluting is no home and no inhabitant. All the rest is closer to being similar than not.

    This site is getting polluted.

  3. User avater GBA Editor
    Martin Holladay | | #3

    Response to Shane Claflin
    Shane,
    I don't think I agree with your definitions of "passive" and "active" -- namely that "a passive system uses existing heat" and "in an active system, heat is generated."

    As applied to solar equipment, "passive" usually refers to design elements that don't require electricity, pumps, or blowers to operate (for example, south-facing glazing and interior thermal mass). "Active" usually refers to equipment that includes pumps or blowers that use electricity.

  4. Lloyd Alter | | #4

    I have rarely taken so much
    I have rarely taken so much abuse as when I tried to do a jargon watch of geothermal vs GSHP. Commenters wrote "This strikes me as uninformed drive-by "journalism" if you can call it that."

    I love the refrigerator analogy. It makes it all so clear.

  5. Skip Harris | | #5

    Renewable or non-renewable? I think...neither.
    Seems to me that a GSHP is a way of leveraging, of getting more heat or cool for the joule. It seems less akin to PV than it is to insulation: one is a way of producing energy (and thus the label of "renewable" makes sense) while the other is a way of getting more use out of the energy from whatever source.

  6. Shane Claflin | | #6

    groggy
    Thanks for clarifying Martin, I was groggy this mornin. I was thinking more along the lines of passive energy. Something that doesn't require an input to produce heat or electricity. Solar PV, I would call a passive system, and solar hot water to capture heat, even with the pumps? is it semi-passive?

  7. Shane Claflin | | #7

    response to AJ
    The metal and plastics are recyclable. I think the refrigerant ends up as a hazardous waste. I could be wrong, I was wrong once.

  8. User avater
    James Morgan | | #8

    Heartily agree, Allison.
    GSHPs are wildly oversold: a greenwash product which would not exist in the market without tax credits. Hardly a promising sign of sustainability.

  9. User avater GBA Editor
    Martin Holladay | | #9

    More on passive and active
    Shane,
    I have never heard the adjective "passive" applied to a photovoltaic system. A solar hot water system is an example of an active solar system -- clearly it isn't passive like south-facing glazing or a dark-colored slab floor.

  10. User avater
    Danny Kelly | | #10

    So is ground source more efficient than air source
    Good article but still wondering about the big question. Most "geothermal" salesman will tell you about the COP being twice that as an air source heat pump. I believe there are still federal and state tax credits for these systems as well - is that warranted?

  11. User avater GBA Editor
    Martin Holladay | | #11

    Response to Danny Kelly
    Danny,
    Good data on the COP of installed residential ground-source heat pump systems are surprisingly rare. Manufacturers report COP data that omits electricity used by pumps, and this reported data is misleading.

    The best data I know of come from two researchers: Rob Aldrich of Steven Winter Associates, who measured the COP of a residential system in Connecticut (COP = 3.5), and from Andy Shapiro, who measured the COP of three residential systems in Vermont (average COP = 2.75). The data were reported in the April 2008 issue of Energy Design Update.

    Several researchers have calculated that a ground-source heat pump installation usually costs more to install than ductless minisplit air-source heat pumps plus a PV system to provide all of the electricity necessary for the air-source heat pumps. Even if the air-source heat pumps have a slightly lower COP than the ground-source heat pump, you still end up ahead.

  12. Robert Brown | | #12

    just because
    I can't let this go, I'll note for the record on this one more time;

    1. air source is better, in almost all cases.
    2. Still, the energy you are getting from GSHP IS renewable when you are heating. you are pulling energy from the ground. energy returns to the ground via natural means. When you are REJECTING heat, it's an air conditioner removing unwanted thermal energy from your home.
    3. The refrigerator is pulling energy from its source... the stuff in the box... and rejecting it to your house. bad analogy.
    4. the problem with the renewable energy you get in heating mode GSHP, is that the parasitic losses are high in the pumps that geo MFGs like to use because apparently they have no idea how to pump water efficiently. I say that with a little snark, but only a little... most geo guys are not high grade hydronicists, they are mostly air guys. so the ratio of energy gained compared to energy used isn't significantly enough better than air source (current gen tech at least) to justify the cost differentials. In some cases it can even be worse. Some are starting to use ECM pumps, which will reduce this problem. They also have to redesign their heat exchangers to be less restrictive....

  13. Chris Williams | | #13

    Missing the Point - Wrong Analogy
    I think this article is slightly missing the point, the heat pump itself IS NOT an energy source, just like a solar PV panel by itself, is not an energy source. However, where it's getting it's energy from IS an energy source. Solar PV = Sun, WaterSource Heat Pump = Ground. Oil Furnace = Oil.

    Saying the ground is not an energy source is like saying an oil tank filled with 400 gallons is not an energy source, it doesn't make any sense. Is the air an energy source, yes. It has energy in it.

    Regarding the ground source vs air source debate, let me gather some data and get back to you. Main issues when comparing the technology is 1) LCOE. Air source lasts for 15 years, Geo 30 years. Over the life of the system, air source BTUs are much more expensive 2) Any technically compacity that will make an air source unit better (compressor, fans) will also be applied to geo, because it's the same technically. If you get air source with a COP of 5, geo will be 7+, always.

  14. Chris Williams | | #14

    How Are you Defining Better
    Robert,

    How are you defining better for air-source?

    Chris

  15. User avater GBA Editor
    Martin Holladay | | #15

    Response to Chris Williams
    Chris,
    I understand that the COPs you cite are for illustrative purposes only. But these COPs ("air source with a COP of 5, geo will be 7+, always") are totally fanciful and unrealistic.

    Like I said, measured COPs of installed ground-source heat pump systems seem to be in the range of 2.75 to 3.5.

  16. Martin Orio | | #16

    Forest for the trees
    Groundsource heat pumps are a proven technology that extracts stored solar energy from the ground in winter and store solar gain in your property in winter. It is true that based on how they work they are not as easy to "classify".
    They are no less a "renewable" then solar PV or thermal. Those systems use circulators to move solar energy.
    So does a groundsource (aka geothermal) heat pump.
    Further, a GSHP installed to ASHRAE 90.1 standards (not always done sadly), is the most efficient form of heating (operating SYSTEM COPs of up to 5.3), and EERs (not SEERs) of up to 31.7 currently available.
    Although they do, by definition need to be connected to the earth, they are fully 2xs as efficient annually as their air-to-air cousins.
    People who install a geothermal heat pump properly reduce there personal carbon footprint by 50% on average, and create an even baseload for the kilowatts derived from PV, wind, biomass, etc. as well as the dirty fossil burning technologies that currently provide for some of our electric demand. They just use as little as 20% of what the same electric investment would be for straight resistance heat.
    Also, GSHPs used for cooling don't create a heat island by dumping solar gain back into the hot summer air, instead they store it underground (nature's clean battery) to be used the following winter for heating.
    Solar, wind, hydro, it's all good. Classify it as you might, but don't discount geo! Use those green kilowatts to power the most effective and efficient space conditioning!!!

  17. Harold Simansky | | #17

    Back-up Heat
    One point not to be lost is how the efficiency drops for air source heat pumps as the outside temperature becomes colder. Once the temp goes below 20 or so, depending on the model, you will need some sort of back-up heating system. For many it will be electric (ugh) for some maybe it will be a fireplace and for a few it may be an old oil system. At that point, the nod starts going to GSHP.

  18. User avater GBA Editor
    Martin Holladay | | #18

    Response to Harold Simansky
    Harold,
    Your information is out of date.

    Mitsubishi Mr. Slim Hyper-heat (P series) is rated down to -13 degrees F. These models exhibit 100% of rated heating capacity at 5°F and 87% at -4°F.

  19. Joshua Kresge | | #19

    What should GSHP systems be called?
    I can see how this drives you crazy. You have valid points. Heat Pumps are not sources of energy. The Sun is a source of energy, freely moving water is a source of energy.

    The ground however is source of stored energy which can be harvested by using a system - that system was unfortunately labeled a Geothermal Heat Pump System a long time ago. The name is the #1 source of confusion.

    "Geothermal? Cool lava in my backyard to generate heat" (Joe Homeowners first impression).

    This whole debate could give a class of law students a whole semester of expensive & useless discussion.

    The ground is a solar panel, a very big one. Its energy comes from the sun. The sun is renewable source of energy. Harnessing that energy is our mission - geothermal heat pump SYSTEMS extract energy from the ground in heating mode with the help of electricity (its source could be renewable or nonrenewable).

    So is a GHP on its own a renewable energy system? No - its piece of metal. Is a GHP hooked up to a ground loop and electric & pumps a renewable energy system? It can be PART of one.
    If the electricity used in the system were generated from a renewable source (like hydroelectric) the overall system could be considered "renewable", thus we'd have an expanded renewable energy system. If its electricity supply is a coal fired power plant than the overall system is technically non-renewable. Thats my take on it, but like Shane I have been wrong before.

    But enough about academic interpretations - lets get to the real point here.

    The point is that some believe the GHP industry has benefited from being portrayed as using a ‘renewable’ energy source.... and I agree. And whether or not you think it fits any definition the fact is that consumers think GREEN SAVE THE PLANT when they see geothermal portrayed as renewable. The message at our micro-level is incorrect, but the overall premise that geothermal is a more “green” system is correct. (by green I mean higher efficiency, lower impact on the environment, less expensive to operate).

    Lets try something new here - lets propose solutions instead of the usual everyone bash everyone else's product and beliefs. Geothermal Heat Pump is not the best name for a ground source heat pump system because of the confusion it creates - if you could rebrand "Geothermal Heat Pump System" to something else what would it be?

  20. User avater GBA Editor
    Martin Holladay | | #20

    Response to Joshua Kresge
    Joshua,
    Engineers and GBA have been calling these systems ground-source heat pumps for a long time.

  21. User avater GBA Editor
    Allison A. Bailes III, PhD | | #21

    Response to Robert Brown
    Rob, I disagree. A refrigerator and a GSHP do exactly the same thing. They use electricity to move heat. They also both do it with about the same coefficient of performance (COP). The only difference is where the heat is coming from and going to. The refrigerator, in fact, is a better analog than Iceland's pumping of heat from the ground, which is a true geothermal source.

  22. User avater GBA Editor
    Allison A. Bailes III, PhD | | #22

    Response to Chris Williams
    Yes, the ground can be a source (or sink) of heat. So can the air. The main reason it's not a renewable source of energy is because the input electricity has to do a lot of work through the refrigeration cycle to turn the heat into something usable.

  23. Joshua Kresge | | #23

    Response to Martin
    I'm aware that most in the industry correctly call them Ground-Source Heat Pumps - but if you were to re-brand the entire idea to avoid confusion for home owners could you come up with a new name that made sense and appealed to the masses? My point is that GSHPs need to be presented and sold as something completely different than just another heat pump - after all the equipment might be similar but the customer experience and expectations are entirely different.

    It wouldn't be "Renewable Heating Plant" or "Lava Comfort Generator" but it might be an "EcoPump System" or "GeoHeater" or "EarthPump" or "Heat PipeLine" or "Earth Radiator" or ????????

  24. User avater GBA Editor
    Martin Holladay | | #24

    Response to Joshua Kresge
    Joshua,
    You wrote, "My point is that GSHPs need to be presented and sold as something completely different than just another heat pump."

    Well, you are thinking like a marketer. I'm thinking like an engineer. I like to call things by their proper names.

    Your marketing efforts have a high hurdle, unfortunately, because in the eyes of many energy experts, a GSHP is just another heat pump -- although one that costs much more than equipment that makes more sense.

  25. User avater GBA Editor
    Martin Holladay | | #25

    About claims that GSHPs take advantage of solar hear
    Many GSHP marketers claim that their systems are a type of renewable energy system because they gather solar heat from the soil. This is silly.

    After all, the range of temperatures for the soil and air on this planet are usually in the range of -65°F to 140°F. That's a good thing. If the temperature of the earth's soil and air were near absolute zero (−459.6°F), we'd all be in trouble. Every house on the planet, whether heated by an oil furnace or solar energy, benefits from this fact.

    However, we don't usually call an oil furnace a "renewable energy system" just because it benefits from the fact that it doesn't have to operate in an absolute-zero environment. We take it for granted that the air and soil around our houses are temperate.

    So let's not allow GSHP manufacturers to make a big deal about the fact that the sun warms the soil. Of course it does! The sun also warms the air, and my roof. Thank goodness for that.

    A GSHP is a heating device operated by electricity.

  26. User avater GBA Editor
    Allison A. Bailes III, PhD | | #26

    It's not all solar!
    Thanks for pointing out the issue with the source of the heat for GSHPs, Martin. Indeed, much of what's stored at the surface does originate from the solar energy hitting the Earth, but a huge majority of the heat within our planet is left over from the formation of the Earth, which was due to gravitational energy. That energy is slowly dissipating over time, but we're at pretty much a steady-state temperature because that loss is being replaced by the heat from radioactive decay inside the Earth. Those two sources are where the true geothermal energy comes from.

  27. Joshua Kresge | | #27

    Sun warming soil
    Martin - correct me if I'm wrong here but isn't the whole purpose of a ground loop to take advantage of the constant temperature of the ground? (Which is constant because of the sun, my house isn't heated on a winter night by the sun). Isn't a geothermal heat pump more efficient than a regular heat pump throughout the winter because of the warmer climate in the earth as compared to the outside air? Are you telling us that air source heat pumps are superior to geothermal heat pumps in operation or the cost of geothermal never makes sense?

    It seems as if you are calling GEO b.s. because it uses electricity - is it not a real solution? Is it not a better option for homeowners burning fossil fuels like propane and oil?

    I truly respect your experience and opinion here, just trying to get a complete understanding.

  28. User avater GBA Editor
    Martin Holladay | | #28

    Thanks for the correction, Allison
    Allison,
    I appreciate your point, Allison -- but I assume that the additional facts that you provided aren't enough for you to give the GSHP industry a free ride on their "geothermal" claims...

  29. User avater GBA Editor
    Martin Holladay | | #29

    Response to Joshua Kresge
    Joshua,
    Sometimes it makes sense to heat with electricity -- especially if the electricity is produced by wind turbines, PV arrays, or hydro. It makes less sense to heat with electricity when the electricity is generated by a coal plant. If you live in an area of the country with coal generation, then natural gas heat makes more sense than electric heat.

    On average, ground-source heat pumps have a slight efficiency edge over air-source heat pumps, but not enough of an edge to justify their very high installation cost -- in most cases. If you can install one inexpensively, however, it might be a good choice.

  30. Ron Keagle | | #30

    Terminology
    I would divide geothermal heat into two categories:

    1) Heat below room temperature.
    2) Heat above room temperature.

    Item #2 is found in natural earth sources similar to hot springs or molten lava. Item #1is found in all the rest of the earth, including frozen ground. Both are geothermal.

    Item #2 can be used as is, and it is renewable.

    Item #1 is also renewable, but it requires compressing its mass to raise its temperature above room temperature. The compressing requires energy. That energy could be provided by a renewable or non-renewable source.

    So I would say that the term “geothermal heat pump” is just fine. What is needed is a term that distinguishes the two different categories of geothermal heat.

  31. Matt Davis | | #31

    Terminology and some new data
    The question of whether a source of energy is renewable should be based on whether the energy removed can be replenished over relatively short time scales. Whether additional energy is required for utilization goes to the question of performance, efficiency, and return on investment, but not renewability. The thermal energy in the ground to depths of several hundred feet is largely attributable to earth surface temperatures (solar energy). In systems that are properly designed and account for local conditions, the thermal energy extracted from the shallow subsurface is renewable.

    Regarding measured COPs, we have some unpublished (i.e. take it or leave it) data from 5 residential installations in New England this past spring. The COP calculations include the circulating pump as a non-thermal component but do not include hot-water generation. The average daily COPs range from 2.6 to 3.8. The lower COPs are older installations with single stage heat pumps. Newer installations with two-stage heat pumps with both closed and open loops have higher COPs, and the measured values line up well with manufacturer specifications. Open loop systems that use domestic water wells as the energy source have much lower installation costs, increasing the rate of return on investment.

  32. User avater GBA Editor
    Martin Holladay | | #32

    Average COPs
    Matt,
    Your average COPs of 2.6 to 3.8 are close to the figures I quoted (2.75 to 3.5). Sounds about right.

    So I guess that (according to your logic) air-source heat pumps are also renewable energy systems?

  33. Matt Davis | | #33

    Renewable Heat
    Martin,
    Yes, and it's not just my logic that leads to that conclusion. The UK has a new Renewable Heat Incentive in which both air source and ground source heat pumps are recognized as renewable energy systems. However, because of uncertainty in actual COPs, they are not yet providing financial incentives for air source heat pumps. Incentives for ground source heat pumps will initially be provided only for commercial systems that can demonstrate favorable COPs.

  34. User avater GBA Editor
    Martin Holladay | | #34

    Response to Matt Davis
    Matt,
    During the winter, when a heat pump lowers the temperature of the outdoor air, you are calling it a renewable energy system. I wonder, though: during the summer, when a heat pump raises the temperature of the outdoor air, is it still a renewable energy system? Or does the change in direction of the heat flow alter the characteristics of the equipment?

  35. Aj Builder, Upstate NY Zone 6a | | #35

    You guys are killing me!
    PV

    You guys are killing me!

    PV provides energy. Heat pumps use energy to move heat.

    GSHP and ASHP are both energy using heat pumps that move heat. Using the word renewable with these devices is nuts.

    I still have my perpetual motion engine for sale. Send $10,000 cash to Aj builder ny.

  36. Ed Lohrenz | | #36

    Ground coupled heat pumps
    ALLISON: Geothermal heat pumps (aka: geoexchange systems, ground source heat pumps, ground coupled heat pumps (GCHP), earth energy heat pumps, etc.) use electricity, whether it is produced by burning dirty coal, nuclear energy, wind generators, hydro-electric, or whatever, to gain access to a renewable energy source…the earth. The earth is a renewable source of energy. The energy stored in the earth gets there from several sources, primarily solar energy, but also energy from the deeper earth (true geothermal energy source), and also, energy recovered from waste heat sources (waste heat from air conditioning buildings, refrigeration systems, solar energy stored in the earth, waste energy from combined heat and power plants, etc.). In fact, the key difference between a GCHP system and other heat pumps (refrigerators, air conditioners, air source heat pumps) is that the earth STORES energy. An air source heat pump dissipates energy to the air outside and it blows away, and if the air is warm enough, it can extract energy from it…but only if it’s warm enough…if the air gets cooler the air source heat pump runs less and less efficiently till it finally reaches the point where electric heat is as efficient. A refrigerator, though the actual equipment works on exactly the same principle as a GCHP, does not take advantage of the renewable energy stored in the ground. It’s not the heat pump that is renewable…it’s the energy source…the ground.

    A common misperception about a GCHP, even among well-educated people, is that since it does not produce power that can be used to run lights and equipment, it’s not producing renewable energy. Photo-voltaic cells simply convert solar energy to electricity. Wind is created by the impact of thermal energy (sunshine) on the earth. Hydro-electric power is created when thermal energy evaporates water, creating rain that flows down rivers creating electricity when it flows through a generator. A GCHP simply uses thermal energy that is stored in the ground (solar energy and some energy from the deep earth) directly instead of producing electricity. Using this energy directly is actually more efficient than converting energy. The only reason a heat pump is needed to use it in our homes and buildings is to upgrade the energy…increasing the temperature from normal ground temperature (45 to 70F) to something warm enough to keep us comfortable. That does not mean that the energy stored in the ground is not renewable (as long as the sun is shining – and if it’s not we have other issues!)

    You also suggest in your response to Chris that “the main reason it’s not a renewable source of energy is because the input electricity has to do a lot of work through the refrigeration cycle to turn the heat into something useable.” Are you suggesting that because a piece of equipment (a heat pump) is needed to gain access to the energy in the ground that we shouldn’t use it? That’s like saying power generated by the wind is not renewable because we need a piece of equipment (the wind generator) to gain access to the electricity that is generated by it. Have you ever considered the energy that goes into maintaining a wind generator? Should that not be included in the equations?

    So is a refrigerator a renewable source of energy? ABSOLUTELY IT IS – IF you are circulating a source of renewable thermal energy through it for it to work with! Is the refrigerator itself a source of renewable energy? It’s a tool we can use to gain access to renewable energy exactly like a wind generator or a photo-voltaic cell.

    ROBERT: you say “air source is better, in almost all cases”. It depends on the climate you are working in. If the air temperature you are using as a heat source or sink is within the efficient operating range of the equipment you are using, an air source heat pump can be as efficient as a GCHP. The problem with that comment is that there are many places where people need heating and cooling that the air temperatures simply are not within the efficient operating range of the air source heat pump. I’m from an area where the temperature occasionally gets down to -40. Not many air source heat pumps out there that like those temperatures. The ground in my area is plus 45F all year round. That is well within the efficient operating range of a heat pump.

    You also suggest that “geo guys are not high grade hydronicists”. This is like saying those builders are not high grade architects. There are good and bad designers in any field of expertise, including yours I’m sure.

    MARTIN HOLLADAY: Mitsubishi Mr. Slim may by rated down to -13F. What is the efficiency at that temperature, and what is the life-expectancy of the equipment at that temperature? You also suggest “sometimes it makes sense to heat with electricity…especially if the electricity is produced by wind turbines, PV arrays, or hydro” and it makes less sense when it is generated by a coal plant”. Have you thought how much better it would be, even if the COP of a GCHP is only 3.0, to use one third of the electrical energy to take advantage of the renewable energy stored in the ground under the building. Then you only need one third of the wind generators, PV arrays, hydro plants or coal fired generators…and one third of the power lines that environmentalists like to bitch and complain about.

  37. User avater GBA Editor
    Martin Holladay | | #37

    Response to Ed Lohrenz
    Ed,
    You wrote, "A common misperception about a GCHP, even among well-educated people, is that since it does not produce power that can be used to run lights and equipment, it’s not producing renewable energy." I guess I plead guilty as charged. I have concluded that a ground-source heat pump is not producing renewable energy.

    You wrote, "Have you thought how much better it would be, even if the COP of a GCHP is only 3.0, to use one third of the electrical energy to take advantage of the renewable energy stored in the ground under the building?" Of course anyone who chooses to heat with electricity should use a heat pump. If you can attain a COP of 3 -- and that goal is attainable with either an air-source or a ground-source heat pump, although actual COPs can, of course, be a little lower or higher -- then you can just barely achieve parity (assuming that the electricity comes from a fossil-fuel-burning power plant operating at an efficiency of 33%) with a furnace in your home that burns the fuel directly.

  38. Aj Builder, Upstate NY Zone 6a | | #38

    Ed, come back to earth. Laws
    Ed, come back to earth. Laws of thermodynamics my man. PV, windmills produce energy to do work from sun energy streaming to earth. That is where we start to consider a device to be sourcing renewable energy. These devices produce energy that can produce work.

    Geothermal can also be tapped to produce work.

    Heat pumps that move heat energy to heat or cool our homes NEED ENERGY PUT IN TO MOVE THE HEAT. They CANNOT produce work Ed.

    This thread if harnessed might yield some heat energy but energy was put in to get it out.

  39. User avater GBA Editor
    Allison A. Bailes III, PhD | | #39

    Response to Ed Lohrenz
    You wrote, "A common misperception about a GCHP, even among well-educated people, is that since it does not produce power that can be used to run lights and equipment, it’s not producing renewable energy." I'd say that's not a misperception or misconception or misunderstanding or anything of the sort. A heat pump takes energy to move heat. That's not production in any sense of the word. Moving isn't the same as producing.

    A heat engine, on the other hand, takes heat and does work. If you hook up a device to pull heat out of the ground, do some work with it or turn it into electricity, and then dump the waste heat to a lower temperature sink, then I'd call that a renewable energy source.

    The key to this whole thing is the word pump.

  40. Ron Keagle | | #40

    Heat Pump Function
    My understanding is that a heat pump is acutally doing more than just moving heat, as would be the case with a circulator pump, for example.

    Doesn't a heat pump actually "process" the heat by reducing its mass and raising its temperature?

    I would conclude that the heat pump is not producing heat. But it is "processing" heat, and it is also moving heat. And the processing and moving are two different functions.

  41. Matt Davis | | #41

    Response to Martin Holladay
    Martin, You seem to have taken the intractable position that GSHP systems are not renewable (which is the topic of this discussion), so entering into a dialog about the renewable attributes of ASHPs seems to be of little benefit. Cheers.

  42. User avater GBA Editor
    Allison A. Bailes III, PhD | | #42

    Response to Ron Keagle
    Yes, the heat pump does indeed process the heat through the refrigeration cycle. That's where the real pumping action occurs, and that's what takes the work. Heat doesn't have mass since it's a form of energy. (I'm ignoring Einstein's mass-energy equivalence here, as given in his famous equation E=mc^2, since we're not crossing that border.) But yes, a heat pump does raise the temperature. See my article from last week, The Magic of Cold, which explains the refrigeration cycle.

  43. Ed Lohrenz | | #43

    MARTIN: Electricity is almost
    MARTIN: Electricity is almost always equated to the amount of GHG emissions from the source. A fossil fuel plant produces GHG's to produce electricity. What's the source of the energy. Try tracing back the source energy for oil or natural gas, including extracting gas and oil from the ground, process it, pipe it around the country, etc. That information is hard to find, and no one quotes figures on the GHG's from burning gas from the source. So if we consider only the GHG's that come into play when we burn gas, that's not entirely accurate. What about the energy to pump it to your home, extract it from the ground etc. So let's be fair and take into account the source of the gas and oil and then compare it to the source of electricity.

  44. Aj Builder, Upstate NY Zone 6a | | #44

    Ed, you're way far from
    Ed, you're way far from planet Earth. Come back come back. This subject is difficult enough for the PhDs but we are close to having some chime in that the moon landing was faked.

    Ron, seriously? We are not changing the mass of refrigerant, the mass is always the same. The pump is doing two things, circulating the refrigerant and compressing it so as to set it up to for two locations where we change it's phase from liquid to gas and back again.

    Give this up all... we are so far from reality that we will next have to splain the Kennedy assassination.

    Waht a massive thread, has me gasping for air and LOL. Of course I could be wrong on all my points too, but it sure has been a pleasure I tell yaa. Smiling in the ADKs.

  45. Ron Keagle | | #45

    Mass
    AJ, your point is well taken that the mass is always the same. I meant to refer to the compression of the mass so it becomes more dense. But then we have to deal with the contention that heat does not have mass.

  46. Aj Builder, Upstate NY Zone 6a | | #46

    We got to quit while we are behind Ron
    We got to quit while we are behind Ron. You meant compression of the refrigerant gas which does have mass. Heat Ron is not mass. Check out Wikipedia for heat. As to refrigerant, somewhere amongst some engineering books from long ago I have a fluid dynamics textbook that would cross your eyes in pain if you are not up to snuff with calculus, differential equations and physics. At that level I would really have to toss bull here to explain any of it. Compressible fluids and incompressible fluid flow modeling mathematically is for the birds... especially since they fly with the aid of a compressible fluid we call air and some in the past called ether. Going in deep to design a heat pump system is an engineering specialty. And that is where Allison comes in.

  47. Ron Keagle | | #47

    Heat Without Mass
    aj,

    This is an interesting point about heat and mass. I can understand the concept of how the two are separate, but I have difficulty in seeing the practical example. Can you give me an example of the existence of heat without mass?

    Heat in the form of radiation need not have mass, but heat in that form has no effect until it strikes mass. So tell me what heat without mass is like.

  48. Joshua Kresge | | #48

    To Geo or Not to Geo
    A GSHP leverages a renewable energy that is the thermal energy of the earth.

    The entire system is used to leverage a renewable energy source in an effective way that improves home comfort. A GSHP system is a more effective solution in terms of producing BTUs with a given input of energy.

    The real question is when does it make sense for one to install a ground source heat pump as opposed to a regular heat pump OR other comfort system.

    Could we come up with a formula or process that spit out the answer to "optimal comfort system" given the persons preferences? My feeling is that it can and should be done. Anyone interested in trying?

  49. Aj Builder, Upstate NY Zone 6a | | #49

    Heat as defined at Wikipedia
    Heat

    Heat generated from the nuclear fusion in the Sun, and transported to Earth as electromagnetic radiation, is one of the driving forces of life on Earth.

    Heat is energy transferred from one system to another by thermal interaction. In contrast to work, heat is always accompanied by a transfer of entropy. Heat flow is characteristic of macroscopic objects and systems, but its origin and properties can be understood in terms of their microscopic constituents.

    Heat flow from a high to a low temperature body occurs spontaneously. This flow of energy can be harnessed and partially converted into useful work by means of a heat engine. The second law of thermodynamics prohibits heat flow from a low to a high temperature body, but with the aid of a heat pump external work can be used to transport energy from low to the high temperature.

    In ordinary language, heat has a diversity of meanings, including temperature. In physics, "heat" is by definition a transfer of energy and is always associated with a process of some kind. "Heat" is used interchangeably with "heat flow" and "heat transfer". Heat transfer can occur in a variety of ways: by conduction radiation, convection, net mass transfer, friction or viscosity, and by chemical dissipation.

    The SI unit of heat is the joule. Heat can be measured by calorimetry, or determined indirectly by calculations based on other quantities, relying for instance on the first law of thermodynamics. In physics, especially in calorimetry, and in meteorology, the concepts of latent heat and of sensible heat are used. Latent heat is associated with phase changes, while sensible heat is associated with temperature change.

  50. Ron Keagle | | #50

    Origin of Ground Heat
    For heat pump extraction installations, I wonder how much of that geothermal heat originates from the sun warming the surface, versus originating from deep in the earth.

    I understand that heat originating in the earth’s core is caused by radioactive decay.

  51. Aj Builder, Upstate NY Zone 6a | | #51

    Ron, the train has left the
    Ron, the train has left the tracks my man.

  52. JP Jon Pierce | | #52

    WE DO LEVERAGE, PROCESS, "move" a renewable form of work
    Since I have had to sell over 70 systems myself alone, I have explained (to get the check, no matter what a contractor discusses) that no "we" do not really move any heat at all. --- [ within the "3-day right of rescission/cancellation" notification on every agreement (now that one customer used to withhold a significant balance, not seeing it on their agreement 3 months later) in/on every written agreement since 2008...]
    "We" did not create the movement of heat-energy, ever, as it does that simply/physics-ally by itself- in the presence of a difference in our DELIVERED/distributed different-temperature media/mass of fluid/air/refrigerant, whatever... Heat-Energy (k) moving within a calibration of existance- in what we refer to as time, is then equated to WORK (q)... for my sales discussion, that is quickly changed to noting the refrigerator or water-cooler , too: However, only as discussing moving warmer food in or warmer city- or well water into say the water cooler for a cool drink.

    GEO is renewable,
    and the THERMAL- if we know the mass is moving per time unit, is WORKING renew-ably within all about the Earth, -ground, inclusive, to our comfort in having hot water or hot air or cool air comforts..
    I have plenty of reason to present redundantly---

    JUST LIKE PASSIVE SOLAR, Earth tubes of air or water can , too, be positioned to use convection/radiation/conductive energy movement --- in a given convection-effect with any thing of a differing temperature. Yes, without pumps, even the GEO-ocean-water connected tubing to bridges can melt ice with appropriate fluids in a "geothermal" piping system in the bridge, routed back down to closed loops in the ocean water (in columns of concrete, whatever).

    Since we have had COP 4+ with GT GeoThermal Heat Pumps, (then heating only) since 1977 or earlier, - seems fairly sellable - the concept of
    RENEWABLE
    = 76% (and that's a nice number) to 80% of the energy that was created to move, moves when a fluid or air media is at a temperature difference and is made present by pump(s) and/or fan/blower, etc, etc... just as if you held the garden hose into the ice box, it would keep running to cool the 50-degree water to a cooler temp, and the coils get hotter in the back, then, trying to allow for the NATURAL ENERGY MOVEMENT INCREASE , ALLOWING US TOO USE the heat-Energy that has moved, in and then at the back - out of the refrigerator machine. We only then pay 20-cents to 24-cents on the dollar of say a big-toaster-like furnace of just expensive straight electric heat .
    ---
    I dunno, I know I could improve each year or each sales call, but closing over 85% of the buyers I present to , - just keeps me saying it like that. (huh , salesman AJ... :)

    GEOTHERMAL IS EARTH-HEAT-ENERGY- and in weather, whether air or ground or oceanic or crust or core or cosmic , hah! Shallow, deep, high above, if it is the Earth's and it is allowed to move as described, it is RENEWABLE, I have reason to believe.
    Considerings:
    Just like solar collectors there are Earth collectors (ECL's) that go to Heat Exchangers (radiators/water-coils,etc) in fresh air vents into buildings WITHOUT heat pumps, that are MORE RENEWABLE for Pre-Cooling as well as Pre-Heating fresh air than a solar-heating-only renewable energy comparison.

    solarbustering complete

  53. Aj Builder, Upstate NY Zone 6a | | #53

    Jon,off topic, is English
    Jon,off topic, is English your first language? I am pretty cryptic but you are harder to read than Sanskrit my man.

    Heat pumps are heat pumps. Let's just leave it at that shall we? We shall, I'll shall.

  54. JP Jon Pierce | | #54

    All the quicker... GEO RENEWABLE or SOLAR or AIR
    How can we just keep getting it all in place QUICKER and LESS-EXPENSIVELY:
    HW-GT-Air-HeatPumps or Solar- Air/Water, etc . ???

    Always living in the SunLight, or underground or Just bringing it to those wanting better.

  55. JP Jon Pierce | | #55

    AJ you can ask , but do you sell renewables?
    Let's focus on the subject and perhaps less personal commentary, shall we?

    Which paragraph could use your kind of english?

  56. JP Jon Pierce | | #56

    Some 1993 % of EPA then allows a view of renewable %
    See if this helps how much is renewable if since we know not all is.
    T's all for the great comments, solar and gt busters, too !
    (an indoors refrigerator example however, really is, if inside, - (out of) not in the envelope of directly "renewable" , I think, so I would use an outdoor ice bin at a convenient store or something else, more objectively., -if I misread something, ignore please.

    EPA 1993 GT HtP etc without comparing COP 5 units of HW-GTHP 100% On-Demand super advanced by comparing dual compressor and 3 staging with highest-speed up to 2 tons over-sized HX Coils, just not mentioned, but used since the early 1980's.
    [copy-paste into addr bar]:

    http://nepis.epa.gov/Exe/ZyNET.exe/9100NXOW.txt?ZyActionD=ZyDocument&Client=EPA&Index=1991%20Thru%201994&Docs=&Query=fname%3D%229100NXOW.TXT%22&Time=&EndTime=&SearchMethod=&TocRestrict=&Toc=&TocEntry=&QField=&QFieldYear=&QFieldMonth=&QFieldDay=&UseQField=&IntQFieldOp=0&ExtQFieldOp=0&XmlQuery=&File=D%3AZYFILESINDEX%20DATA91THRU94TXT00000249100NXOW.txt&User=ANONYMOUS&Password=anonymous&SortMethod=&MaximumDocuments=0&FuzzyDegree=-1&ImageQuality=r85g16/r85g16/x150y150g16/i500&Display=hpfrw&DefSeekPage=&SearchBack=ZyActionE&Back=ZyActionS&BackDesc=&MaximumPages=5&ZyEntry=13

  57. James Craig | | #57

    Late to the party...
    If a GSHP (or ASHP) working in heating mode has a net COP of 3.0, then only 1/3 of the energy that is used to heat the building comes from the grid (whether that energy be renewable solar or non-renewable coal). The other two thirds is harnessed from the subsurface – this energy is predominantly stored solar thermal energy, most certainly a renewable resource. Some unknown fraction of that energy may alternately come from waste heat that was previously stored during the summer months (which also predominantly comes from the sun). Because of this, in heating mode, calling these systems (either GSHPs or ASHPs) “renewable energy systems” is certainly justifiable, and likely warranted. Just because they require help to harness this renewable solar energy does not magically make it non-renewable. The net effect with either technology is that *for the same total thermal energy input* into the building less work energy (potentially sourced from non-renewable resources) was used. This distinguishes these systems from energy efficiency technologies, which reduce non-renewable energy used by reducing the total required energy input into the building. As the COP increases, a higher and higher percentage of this thermal energy input is renewable. At some point, even Allison should be able to accede that thermal energy that is 70% or 85% sourced from the sun (and can be replenished within a reasonable time frame) should be labeled renewable.

    In cooling mode, Allison’s argument holds a bit more weight- the ground may then be considered a battery for storing waste energy for later use, and it is more of a stretch to label GSHP or ASHP systems for use in warmer climates as “renewable energy systems”. It may be more appropriate to label heat pumps an energy efficiency technology in this context: here, they are reducing the amount of energy required to move heat from the building. However, the fact that, with GSHPs, some part of this heat is then recycled for the winter months blurs the line a bit…then we are taking the solar energy residing in the building itself to heat the home at a later date (again, renewable).

    Just to be fair, I don’t discriminate. If someone heated their home with an refrigerator with open doors facing out the window and the amount of heat energy generated by the refrigerator coils was reasonably greater than the electrical energy used, I would call that “renewable” as well. I might even put a beer in there to celebrate their contribution to renewable energy.

  58. James Craig | | #58

    Origin of Ground Heat
    In response to Ron's question, the deep geothermal component of energy pulled in by most GSHP installations in heating mode is negligible: ~0.05 W/m2 originating from geothermal gradient vs ~350 W/m2 from solar to heat a block of soil.

  59. Michael McCaughan | | #59

    Heat pump basics
    the author has a fundamental misunderstanding of how a heat pump works. A heat pump doesn't create any heat, it moves heat energy from a source to a sink. The amount of heat that it moves for a given energy input is dependent on a number of variables, including the rate of conductivity and the delta Temp between the working fluid and the source/sink. Because of the physics involved GSHPs move a lot more energy than ASHPs. Whether we are talking about an air source or a ground source heat pump, in heating or cooling mode, ALL of the heat energy moved IS renewable, because the source of the heat energy is ultimately the sun....period

  60. User avater GBA Editor
    Martin Holladay | | #60

    Response to Michael McCaughan
    Michael,
    You wrote, "the author has a fundamental misunderstanding of how a heat pump works. A heat pump doesn't create any heat, it moves heat energy from a source to a sink."

    I can assure you, Michael, that you are barking up the wrong tree. I know Allison, and Allison understands how heat pumps work.

  61. Aj Builder, Upstate NY Zone 6a | | #61

    PHDs beat rock paper scissors
    Work is required to move heat with a heat pump. I am also sticking with the PHD verses the sellers of systems with inflated marketing.

  62. Richard And Miranda Menzies | | #62

    GSHP and Energy
    After living with a GSHP and 4 KW grid tie solar PV system for a year in an area (snowy UT mountains, elevation 5500 feet) with 7000 dd heating and 300 dd cooling, we have $600 in gas and electric bills (for the whole year). All I can say is that this system works wonderfully well in our climate. While the house (3,500 ft2) is well insulated (2x6 studs with blown in insulation and 2 inches of extruded PS), the 4 ton system has successfully provided comfortable heat and cooling, and a lot of our hot water (including many house guests).
    We are believers, in this way of harnessing the solar energy stored in the ground. Input temperatures from our loops at 7 feet depth vary from 68 deg F in summer to 40 degF in Winter. We have polypropylene glycol solution in the loop, which goes out to the ground at 30 deg F, but ground loop is maintaining temperature.
    Its a really low carbon footprint approach, no matter what you call it.

  63. Jonathan Beers | | #63

    References for Ground Source Heat Pump studies
    Thanks, Martin Holladay, for the reference to Andy Shapiro's Vermont study as published in April 2008 Energy Design Update. I'm always looking for cold-climate fields studies, and had missed that one. Have you seen the Manitoba Hydro study by Rob Andrushuk w/ COPs of 2.2 to 3.2? See below.

    http://www.mge.com/home/appliances/heatpumps/basics.htm
    A 2009 analysis by the Energy Center of Wisconsin found: "In the residential and community/multifamily scenarios, CO2 emissions generally remained constant or increased slightly with inclusion of a geothermal heat pump system."

    This link includes field study references, including one from Manitoba Hydro:
    http://www.mge.com/home/appliances/heatpumps/

  64. Russell Higgins | | #64

    GSHP Just the facts m'am, just the facts
    Some fascinating comments in the article. I loved the one saying that seemed to say only high energy sources of renewable energy were valid. There goes the whole passive movement. The author also had problems with a system that concentrates energy to acheive higher temperatures. Hmmm, there goes all solar thermal systems.
    At any rate, heating or cooling IS coming from a renewable source, earth temperature, which is governed by radioactive decay in the core as well as solar gain at the earths surface. BOTH RENEWABLE. Is electricity used to extract it, move it, yes, as it is for all but passive designs. Yes, even PV systems need elec. to run the computerized circuits that monitor and convert light to electricity.
    I don't like calling GSHP's geothermal either, but, Xerox is pretty upset over every copy made being know as a Xerox. It's just people taking mental shortcuts.
    System costs are high, and I see more GSHP's going into high end buildings than low end, however, that is due to income / wealth distribution, NOT that a GSHP isn't a good option for most builidng heating and cooling. I've dealt with people far wealthier than I my whole life, and they don't fork out money unless it's going to make them money, unless it's for an ego boost like expensive cars, cigars, alchol, guns, etc or their arm candy, it is not their choice in HVAC systems. GSHP's aren't "popular" because you can't spend it, no matter what it will save, if you haven't got it to spend.
    System efficencies aren't always what they should be, as one commentator noted, due to installers lack of knowledge, of even basic system components as ECM motors for pumps. Under sizing systems and fields is a problem too and goes hand in hand with taking on buildings that just are not energy efficent enough. There should be an industry wide effort to "Brand" responsible installers and designers, which would ensure basic criteria be followed to avoid poorly performing systems, such as building BTU / SF load, safety factor in tonnage (when that backup resistance heating kicks in, there goes your efficencies), field capacity, etc..
    As with everything, you need to ck references on installers and designers, call a half dozen AT LEAST former clients, and ask pointed questions, happy sure, but what was your costs, what are they now, what did it cost to put in. If you can't get that info, you're flying in the dark.
    Finally, the end all to any discussion of the usefullness of GSHP's in conserving energy and reducing pollution is that the biggest installed base of GSHP's is THE US MILITARY, and big surprise, they use it to drastically cut COOLING costs. Google "Ground Source Heat Pumps at Department of Defense Facilities". Hefty reading, but data packed. If you want more links backing up GSHP's, ck out my web site http://www.roughdesigns.com.

  65. Bob Lemaire | | #65

    From the outside looking in
    There are a lot of different points of view here. My take is that the original question: Is a [Ground Source] heat pump a renewable energy system? Contains some terms that are pretty vague and various comments are taking them to mean different things. what is a renewable energy system?

    If you define it as my house in the winter, I think the answer is sort of. We keep the place at about 68-70 during the New England winter, pretty much regardless of the outside temperature. Because of that, during those six months or so, a lot of BTUs escape and have to be replaced in order to maintain matrimonial harmony.

    We burn some wood, and some oil. Roughly the BTU equivalent of what is escaping from our nest. Last winter we put in a mini-split heat pump. The wood use remained about the same - one cord, but heating oil use went down by more than 300 gallons to almost negligible levels (cold start boiler). The heat pump used 2,500 Kwh. 300 gallons of oil is equal to a little more than 12,000Kwh.

    The house lost the same amount of energy yet we used about 9,500 Kwh less wood, oil, and electricity to replace it. There are a lot of things going on with boiler efficiency, warm winter and stuff that can account for some of the difference, but I think we can agree that between the oil and electricity, a lot less energy was put into the SYSTEM. If I can remember the laws of thermodynamics, I think it starts out saying that energy can't be created or destroyed. So I didn't create a bunch of energy to replace what the house lost. What happened was we pumped in replacement heat from outside air.

    I expect that the outside air that was cooled in the process will be reheated (counting on that Global Warming), so to speak renewed, so that we can do it all over again next winter.

    So the ASHP did consume some electricity, and hence some non-renewable energy, but as a component of my shelter SYSTEM, it also delivered a bunch of heat from an outside renewable source. Do I think heat pumps are a renewable energy system? Sorta.

  66. User avater GBA Editor
    Martin Holladay | | #66

    Response to Bob Lemaire
    Bob,
    Leaving aside the question of whether an air-source heat pump is a renewable energy source (my own opinion: if it is, so is your refrigerator), I'm delighted to see your data comparing fuel oil use with electricity use for a ductless minisplit.

    Many other homeowners are reporting results similar to yours. Installing a ductless minisplit is a great way to lower your heating bills.

  67. Bob Lemaire | | #67

    Context is important
    Martin,

    I know, the best kept secret out there. I see people putting in mini-split AC all over the place when they could pay maybe 20% more for the HP version and pay for the upgrade the first year.

    But lets be clear. I said I though it was part of a renewable energy system, not a source. The heat pumps and refrigerators are machines. When I run the refrigerator inside my house, it is operating in a closed system. The heat that is rejected from the condenser into the house, in excess of the energy supplied from the plug, is heat that conducted through the walls of the appliance into the freezer compartment where the evaporator is located. It's a closed system with respect to heating my house. The only net gain is the heat that is produced from the electricity that the appliance consumes.

    My Heat Pump takes heat from OUTSIDE that closed system. I like the previous post that something like if you open the door of your refrigerator and jam it up against an open window, it may also be part of a renewable energy system.

  68. Scott Smith | | #68

    Late to this discusssion,
    Late to this discusssion, but... most people here would consider solar thermal, whether it's used for hot water or space heating to be a renewable energy or heating source. Where I live in central NY, the solar fraction of a decent solar thermal system might be between 50 and 70%. Let's say, for argument's sake, that it's 67% on a very good system. So, at the end of the year, 33% of the heat energy came from the backup source...let's say it is electric resistance.

    Compare that to a GSHP with a COP of 3. At the end of the year, 67% of the heat in the building came from solar energy stored in the ground, and 33% came from grid electricity. Somehow this system is not using renewable energy? Go figure.

    The bottom line is that solar thermal, while much more efficient when running, only gets it's energy when the sun is shining. Many times in central NY we forget what the sun looks like. A GSHP can pull its lower grade thermal energy 24-7. The ground is the solar collector and storage system in one. I have never understood the trashing that geo gets on this site. It's all good. It may not be the best financial purchase for some, but that's another argument.

  69. Melina Jefferson | | #69

    Comparing to a refrigerator?
    I agree that thermodynamically, heat pumps and refrigeration cycles are exactly the same thing... you only have to change your perspective. A heat pump is basically refrigerating the air/ground/water when it's extracting heat from it, and delivering it to a home. And a refrigerator is heating the surrounding room by taking heat from its contents and expelling it to the ambiant. They are one and the same.

    So, a household refrigerator's Qin (heat input) is from the food that goes into it, which is NOT renewable. Qin for a space or water heating heat pump is from the sun (renewable), via the heat sink that is earth itself. So I don't see any validity in stating, "If a ground-source heat pump is a renewable energy source, then so is a refrigerator. "

  70. Peter Crisp | | #70

    Head Spinning on Comments
    I just joined this group and I'm a bit baffled with some of the comments. First, a heat pump (air or ground source) clearly isn't a source of renewable energy, but because it is more efficient than electric baseboard heaters (the typical default in many cases) because it can move heat, it reduces the need for energy. All electricity generation - hydroelectric, natural gas, coal etc. - has some type of environmental impact, so as long as the operating benefits swamp the initial impacts in manufacturing and installing the unit, and I would be confident they do, then heat pumps make sense. It gets more tricky if you go from, say, natural gas heat to electric powered heat pumps, It really depends on the source of the electricity. From what I see, the best tradeoff on price/benefit - including GHG emissions - seems to be hybrid systems (natural gas or electric baseboard or oil fired with an air source heat pump). Even in many areas of Canada, we install AC units, so it's easy to use a heat pump instead. My limited experience with geoexchange is mixed - if they are sized right they work well, but we have a system that is undersized, so the strip heater kicks on more than it should, and I will be adding a ductless mini-split to fix the problem. I've heard many horror stories of bad installs for geoexchange and a bad install can be hard to fix. The point about longer life is well taken - geoexchange systems seem to last longer than ducted or ductless air source heat pumps. If I were to build my own house, I'd insulate really well and use good quality ductless units, at least in BC and probably use a hybrid system or ductless heat pumps or maybe geoexchange in colder areas if there's a good installer and I didn't plan to move. I can probably buy 2-3 sets of ductless units if I had to, and still come out ahead on cost vs. a geoexchange system so it's hard to justify the upfront capital costs of geoexchange.

  71. JP Jon Pierce | | #71

    When you say GEOTHERMAL ... (one declares) "you think"
    Thank you for such GEOTHERMAL discourse and intrusions on our thinking! Now : Good or off a bit?
    "When you hear the word “geothermal,” you think of lava or geysers, of volcanoes blowing their tops."

    I do not. My general neighborhood absolutely does not. Since the GEOTHERMAL hot bed of HVAC and energy transfer is in states like Ohio, from Dayton to Toledo to Cleveland and Youngstown and especially around the football hall of fame: GEO means EARTH, to us here, and Thermal means forms and use of HEAT. GEOTHERMAL like the word SPIRIT has many images and TRANSLITERATIONS as well as TRANSLATIONS and is (SPIRIT) confused with psyche or soul: as in "PEPSI-Spirit" or even "ESPRIT de CORPS" that are simply soulish and psychological and not (lat:) Spiritus transliterated SPIRIT for the grk: PNEUMA: like wind, breath, air but NOT the molecular substance...but we all can say Spirit-Tires, or Spirit-Lift for pneumatic tires and lifts, etc. Those "going crazy" over others not 'seeing' their private interpretations and semantics , etc, need to relax for the understanding: MASSES NEED TO UNDERSTAND the SIMPLICITY OF 76% sustainable and renewable energy available 6 feet deep in USA, at the least, SINCE IT WORKS, IT SELLS, IT SAVES ENERGY, ALLOWS COMFORT at CAN BE WELL-INSTALLED AT A LOWEST FIRST COST GUARANTEED IN CONTRACTS and MARKETING.
    GEOTHERMAL
    Earth Heat . 76% or more so today : RENEWABLE COMPLIMENT. And that will hold in any court of law. How? Already precidents established. So I believe it is time again to realize things like "Don't be a Martyr" have a little , but not much DIRECT resemblance to the definition: TO WIT, or WITNESS, or Leaving a Mark/ hitting the target... [ grk amartarse, in some renderings is "Missing the Mark/Target" in one understanding and translated: SIN= not witness/ not hit the mark/target]
    SO BE A MARTYR to GEOTHERMAL: attest the EARTH HEAT. and Earth Heat SINK as to SOURCE. Tangential (I believe) is all the surrounding second and third derivatives of say "it is solar" "it is ground heat from" etc, etc,....
    One can see who closes GEOTHERMAL SALES will not deliberate on much "drives me crazy" .. but rather DOES IT FIT BEST with the bucks and hours ya can contribute today. (ASK ME ANYTHING SOLAR and GEOTHERMAL. I TRAIN- and even answered Dr. Jim Bowes Q’s in 1996 IGSHPA Cert at Erie PA , and help PhD’s and ENGINEERS and have since 1980 and learned when to say 'I dunno' all that everyone pictures in their mind. One MENTOR: Dr John Jones, Dayton (deceased 1981) was the answer-man to Okalahoma and others, and $300. seminars in 1980, 3”thick manuals then have not changed on GeoThermal Heat Pumps ground loop applications but maybe 5%.

    Pre-Heating, Pre-Cooling, antifreeze bridges and barns floors can all be done with EARTH-COUPLED-HEAT-TRANSFER WITHOUT A HEAT PUMP FOR MORE THAN ANY SOLAR SUSTAINABILITY and RENEWABILITY DOLLAR FOR DOLLAR and works 24/7 year round. Done did it . Feel free to just ask more questions, please.
    I have reason to believe: GeoTube air-piping for HEATING and as well Fluid-GEO-Tubes are completely renewable and sustainable as for the available 24/7 UN-USED 99.99999% Earth-GEO-THERMAL 6ft deep energy that is NOT in the transfer.

  72. User avater GBA Editor
    Martin Holladay | | #72

    Response to Jon Pierce
    Jon,
    I sense a poem hidden in your comments:

    "GEOTHERMAL discourse and intrusions on our thinking,
    GEOTHERMAL hot bed of HVAC and energy transfer,
    GEOTHERMAL like the word SPIRIT,
    We all can say Spirit-Tires, or Spirit-Lift,
    Renewable energy available 6 feet deep,
    IT SELLS, GUARANTEED IN CONTRACTS and MARKETING,
    And that will hold in any court of law,
    SO BE A MARTYR to GEOTHERMAL,
    See who closes GEOTHERMAL SALES,
    ASK ME ANYTHING,
    Feel free to just ask more questions, please."

    Thanks, Jon.

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