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No talk about Geothermal heat pumps

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by dfergx, Feb 25, 2008.

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  1. dfergx

    dfergx New Member

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    It seems the consensus around here is they cost to much for what you get out of it. I am very concerned about electrical power consumption. It is hard to find the power use on either a gasifier or a heat pump. Anyone have any idea how they would compare? I have 240 acers so wood is not a problem. we are building with ifc so the building will stay pretty cool in the summer. propsed building is 3300, we have been told that we would need about a 4 or 5 ton system, but what the heck does that mean. I would just like to hear some exchange on geo vs. gasify.

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  2. wdc1160

    wdc1160 New Member

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    I have done considerable looking into this topic. Here are my findings: Right now for me geo is the cheapest heating alternative, when all things are considered into the cost. However,
    1. Electric in Indiana is cheap but will become deregulated soon.
    9.5 cents per KWH will become 15 soon
    2. It is very ungreen.
    Electric in Indiana uses domestic/foreign fossil fuels.
    3. Doesn’t lend itself well to hydronics.
    Maximum temperatures I can get from 50F water often to limits at about 130F. to get the water over 130 I loose a lot of efficiency.

    4. The colder it is. The less efficient the Heat pump gets.
    As it gets to cold for the heat pump to put out heat it switches to electric resistance heat.

    I have an ideal open loop geo setup. I would require a larger pump and a slightly different electrical setup, but I couldn’t justify it for my purposes.
  3. dfergx

    dfergx New Member

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    I am on a PUD that uses dams. Our juice is 3.2 cents per kwh. But we need like a 1600 amp service, the PUD will only provide 800 on single phase (three phase is like $150,000 to bring in). Why is it that geo themal came in lower then gasifier? aren't these systems like $30,000? so are you saying that a geothermal unit will consume less watts compared to a gasifier of the same btu capacity?
  4. SE Iowa

    SE Iowa New Member

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    I do not know much about geo-thermal systems but I do know a little about icf homes. I personally built a 4700+/- sf icf home with full radiant floor heat (hydronic). The home is 3 levels; basement (1750sf), 1st floor (1750 sf) and 2nd story (1200sf).

    As far as heating goes, we are using natural gas right now. We have gas water heater (instantaneous) and cook on gas and keep our house at 69 degrees. The average temperature (per the gas company charts) was 11F here last month. That is an average of the 30 days in the cycle. I do not know how that compares to where you live, but our gas bill stated that we use 149 therms total. The most we ever used was 164 therms in one month. I am told that is very good for a house of this size. I will admit that we do not use the unfinished basement yet and the temp down there is usually 67-68 degrees.

    As far as AC, we actually have 2 separate high velocity units; a 1.5ton unit in the attic (which I am told is the smallest central unit you can buy, equivalent to a large window unit) and a 2.5 ton unit in the basement. I can say that the attic unit keeps the house conditioned at ~73 degrees all summer except that 2 weeks in august where it is 95 F and sunny every day. I think that the brick siding and shingles are too dark and once they heat up in the sun, it takes awhile to cool down in after the sun goes down.

    I hope this gives you an idea of the size of unit you may need. I am quite astonished at just how low it cost to condition my house (not that it couldn't be better though. I wonder if a 4 to 5 ton unit of geo-thermal is the same as a 4-5 ton conventional AC unit, etc? Maybe one of the experts could chime in.

    One question I have is how you convert a therm into btu's/hour. I here you guys talk about a 60,000 btu/hr output. Is it correct to think that if I use 150 therms per month and that equals, lets say, 1,500,000 btu's, that I use on average 1,500,000 divided by 30 days = 50,000 btu's/day?
  5. Como

    Como Minister of Fire

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    Geo seems to have the sexy appeal at the moment along with PV.

    For it to work, my investigations suggested you need:

    1. Land, that can be easily accessed and dug.

    2. A heating and cooling need.

    3. A heating system designed to use relatively low temperature heat.

    2 did it for us. Just worked out too expensive, and you are still using a lot of electricty.
  6. SciGuy

    SciGuy New Member

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    I think that your decimal point is off one place. Since a therm = 100,000BTUs, then 150 therms equal 15,000,000BTUs. Divide that by 30 gives 500,000 BTUs per day or 20,833 per hour.

    Hugh
  7. wdc1160

    wdc1160 New Member

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    I am not sure what PUD is? Public Util distric? 3.2 cents is as good as it gets.
    And, since gasifiers burn wood, and only use electric for fans and control, then yes gasifier uses less electric. I would say that geothermal in my location is cheaper overall then wood all things considered. I don't understand all of what your saying though.
    Bio, I have a similar size heating space. But, its a ranch and is less efficient. Although I have significant solar gain in the winter. 1 therm = 100K btu. Also 4-5 geo is better than 4-5 ton conventional ac without question. But, larger expense upfront.
  8. Jersey Bill

    Jersey Bill Member

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    check out aquaproducts. They make reverse cycle chillers- air source on the outside, water on the inside.
    I had a few long conversations with John from Aqua products. (http://www.aquaproducts.us/rcc/index.shtml) . They claim that they're reverse cycle chillers "are more economical than a ground source system". It seemed hard for me to believe at first. After thinking about it for quite sometime, the 2 systems are probably close inefficiencys, but the geo system is far more to install because the wells have to be drilled.

    They claim that their efficiency beats a geo system in the summer, and looses in the winter, but over the season, they claim to be slightly better.
    Its still electric though. For me the COP would have to be above 3 to beat using gas. my gas boiler has an COP of about 0.8, and electric is 3 times the price here. It would have to be really high, probably out of range, to beat wood because my wood gets dropped off by a tree guy for free.
    But with the flip of a switch the heat comes on.
  9. begreen

    begreen Mooderator Staff Member

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    This is not quite correct and very regional. A large part of the country does not get as cold as the northeast. Some areas, like TVA and PacNW are largely hydro power. Heat pumps are much more green than some alternatives. Hydronics can be designed for the lower temps, especially in floor hydronics. We're designing such a system now for a friend. Cold only affects air exchange heat pumps, not ground water exchange heat pumps, especially in milder climates. The ground 5 ft down in our region never varies much from about 55 degrees.

    Our house (1924 farmhouse) is now on its second year with a forced air, 2 stage heatpump. I didn't go geothermal, ours is an air to air system. Our heating bills have gone from $3400 equiv. in propane (2005 dollars) to about $270 using the heat pump and wood supplement. This is in a modestly insulated old house with lots of glass. It's far exceeded my best expectations.
  10. Jersey Bill

    Jersey Bill Member

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    the trick with heat pumps is they have to be sized for the winter load, not summer.
    Also, they will be more efficient in milder climates.
  11. begreen

    begreen Mooderator Staff Member

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    Exactly. We've used it for AC only once, but it is on for heating all winter long. It is carrying the heating load unless I don't have a fire going. Many geothermal units are used exclusively for heating.

    I have a question for my friend's system. Can a good hybrid hydronic system be designed that works well with both geothermal and wood gasifier heat?
  12. dfergx

    dfergx New Member

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    what I meant by explaining the PUD and the amps I need was just to illustrate the need to lower my power consumption, not because of the rates but because I have a limited supply and my propsed need for exceeds that. So what I really want to know is how much power does a geothermal heat pump actually consume? from what I heard the gasifier only uses electric for some fans and controls so I am guessing that that is very low like under 5 amps at 120. I still cant figure out how the gasifiers manage to make the super heated flame, it mixes smoke with air and then super heats it to combustion? How does it achieve the super heating? I would think it needs a secondary fuel like oil or resistance but I haven't seen that anywhere.
  13. dfergx

    dfergx New Member

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    Ok Gooserider just explained the some of the operation on a different thread, the combustible gasses go into a gasification chamber and are ignited. That I get. but what ignites them, if they wouldn't combuste by the heat of the wood fire what makes them ignite in the gasification chamber?
  14. Telco

    Telco New Member

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    One important thing to check with on geothermal, ask your dealer how many warranty repairs they have to make on the lines in your area. Some places, they have problems with the ground loops breaking every couple of years. Also, make sure to ask what sort of LABOR warranty goes along with a line break. I was very interested in a geothermal heat pump until I spoke to an installer who advised that his customers who go with a ground loop have to replace the line due to a break, and labor isn't covered under the 50 year warranty the loop has. A 20 SEER air exchange unit is pretty close to being as efficient as a ground loop job, and a secondary heat system like wood would eliminate the need for the resistive strips. The HVAC tech I spoke to advised that the geo setup costs about the same as the best air exchange units when the installation costs are taken into account.

    I'm not necessarily trying to turn you against a geothermal unit, but to give extra info to consider along with it. I love the concept. If you have a deep enough pond nearby, they can run the coils inside the pond as well, and is almost as efficient as the in-the-ground loop with much lower installation costs.
  15. Eric Johnson

    Eric Johnson Mod Emeritus

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    Goose gave a good general description of the process, but he failed to mention that some designs, specifically the Greenwood/Seton, and to some extent the Garn, only have one firebox (refractory lined) which accomplishes both primary and secondary combustion. With the refractory lining (or in the case of the Greenwood/Seton, a cast refractory firebox), you can obtain high enough temps to light off secondary combustion without the benefit of a nozzle.

    But getting back to your question about the standard Euro downdraft design (Tarm, EKO, BioMax, AHS Wood Gun, Econoburn, etc.), the secondary air is introduced to the nozzles after passing through the hot refractory mass making up the bottom of the primary combustion chamber. In the EKO, it's two steel tubes passing through the hot refractory. By the time the air gets to the nozzle, it's pretty hot, though I don't think it's technically "super heated." There it mixes with the wood gas being pushed down through the nozzle, where it ignites and is blown down into the secondary combustion chamber, where it exits through the heat exchange tubes at the rear of the boiler. The spark that ignites the gas in the nozzle comes from the bed of red hot coals sitting on top of the nozzle, which is also red hot. No catalyst or fossil fuel jumpstart is needed. All you need is sufficient heat and air for the thing to work. Typically, that can be accomplished within about 15 minutes of a cold start, with full gasification taking place shortly thereafter.

    With a good bed of coals in the morning, I can get a clean burn and good gasification immediately by putting dry wood onto the bed of coals and closing the bypass damper. The only time you might get some smoke, other than startup, is when the thing goes into idle. The fan stops and if it's early in the burn cycle, smoke gets through the nozzle and up the stack. If the refractory and nozzle are hot enough, it will gasify without the benefit of the blower, at least until everything cools down.
  16. wdc1160

    wdc1160 New Member

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    Eric, did you mean to post the above somewhere else? It seems off topic

    Anyways.
    My research indicates that this approach will dramatically oversize the the system for your ac needs. This causes several problems -- basically making the AC side unusable ((I never found out how to overcome). Further, the manufacturers of these systems advise to size the hottest possible summer.

    Yes green varies by location, but it is still artificially price capped. Ask a large(> 600000KWH per month) business what they pay in electric a year. Large business lost their price cap protection a couple years back. They are paying for our electric usage. This of course is a prediction, but I expect >30% in electric prices in the next 5 -10 years.

    I am only talking geo thermal. I was trying to mention the size limitations to heatpumps. Installers and Manufactuterers don't want them over-sized- they determine from summer cooling budget.

    If they size a geo too big, they can literally make it rain in your house. Correct sizing removes moisture from the air. Oversizing causes rain and other problems.
  17. kimko

    kimko New Member

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    I install both gasification and geothermal systems , the costs are not that far apart, the biggest difference in the 2 is you are a slave to the wood pile the other set it ,forget it and use that time to have a life. I know woods free but your time should be worth something add that with all the incidental expenses geo is pretty sweet its like having your own oil well in your back yard and yes that energy is free , geo is 300% + efficient ,it is unique.
    Wood is great for large loads $/btu.
  18. MarcM

    MarcM New Member

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    1) Some of us enjoy cutting wood in our free time- I like the exercise and have always thought of being an arborist or land clearer if I weren't an engineer... plus you can always buy wood cut and split and even have it stacked and still cheaper than burning oil (in most cases).

    2) The heat energy is free, true, but it's not "300% efficient." This is why heat pumps are rated with a coefficient of performance instead of efficiency... because they don't generate any heat, the just move it from the ground to your house against a temperature differential, which requires a work input... the energy for which is most definitely not free. They are technically, like electrical resistance heating, 100% efficient if the compressor is in an area you desire to heat, since the waste heat it generates is not actually wasted, however, this is only the efficiency of incoming electricity converted to useable heat. Factor in transmission losses and whatever was used to generate the electricity for a more accurate figure.

    3) The cost difference is not great, but if you decide to install both, you've doubled your cost.

    Not saying ground source HP's are bad.... they're right for some heating situations, and not for others. You just have to figure out what, of the availalbe optoins, works best in your particular case.
  19. Eric Johnson

    Eric Johnson Mod Emeritus

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    On the question of being a slave to firewood--it's true. But some of us would that to being a slave to a second job required to pay the oil or gas bill. Coming from a largely rural background, I've always gained a great deal of satisfaction from planning ahead and doing the physical work needed to ensure that my family's resource needs are met. Heating with wood is a multi-faceted effort, and not for everyone, obviously. But it does have its rewards.
  20. kimko

    kimko New Member

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    Definitions of efficiency on the Web:

    the ratio of the output to the input of any system
    skillfulness in avoiding wasted time and effort; "she did the work with great efficiency"
    wordnet.princeton.edu/perl/webwn

    Efficiency as a technical term may refer to: * Energy efficiency, useful work per quantity of energy** Energy conversion efficiency, desired energy output per energy input** Energy conservation, reducing the use of energy** Electrical efficiency, useful power output per electrical power consumed ...
    en.wikipedia.org/wiki/Efficiency

    Sorry if I seem a little negative on wood ,I used to own a O.D.B. ,still burn a cord a yr. in my f.a. fireplace.
  21. brad068

    brad068 Feeling the Heat

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    Eric, I couldn't agree more. I think with the obese problem facing our nation these days, gathering up wood is a win win situation. People getting exercise and supplying themselves with a renewable, clean burning fuel and saving themselves money. It also can be quality family time too.
  22. kimko

    kimko New Member

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    Family AXERSIZE, lol,reminds me of the chain gang I was on as a kid with my brothers,we had a big hungry bon-fire goin in the basement and dad was showing signs of obsession with all the free labor. lol Thanks for the reminiss.
  23. Jersey Bill

    Jersey Bill Member

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    I take issue with that 300%+ efficiency number. Its for salesmen to push around.
    A correct statement would be "spot efficiencies could get to over 300%, given the right conditions" More efficient systems have more wells to keep the delta t down. This drives up the up front cost.

    A COP of 3 (300%) doesn't really excite me because in my area electric is 3 times the cost of natural gas, so thats only the break even point.

    In my experience, geothermal (well system) has a reasonable payback only when used for heating AND cooling. Also, the milder the climate, the better the payback because less wells are needed. If there is an open source available its a different story.

    For geo- In very cold climates more wells are needed for winter heating, and very little summer cooling is needed, so it doesn't really payback (IMHO)

    the refrigeration equipment for air source heat pumps cost about the same as a geo system without the wells. these will have the best payback in the middle climates where it doesn't get too cold, AND summer cooling is required.

    There are too many possibilities to discuss this topic generally. Its really a site specific discussion. Variables include the size of the system, the local climate, the geological conditions, cost of drilling, number of wells, cost of energy, and more.
  24. kimko

    kimko New Member

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    Actually a properly designed geo system will have a cop of 3 24/7 365 days of the year ,in Canada we have to design systems with entering water temps @ 32 F. Air source doesn't work here and I only install closed loop system,open systems can be a real can of worms. Interested in your elec rates ?, local rate here about 10cent/kwh.
  25. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    Given electric rates here, and costs of cordwood, geothermal is even in cost per btu.

    However, install costs of geothermal in most of NH are so high that the return on investment is well into the distant future, as a result of the cost of doing anything sub-surface in the Granite State.

    If I were building new, I'd go with passive geothermal, though - underground houses are fun!

    Joe
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