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Old 06-04-2007, 05:45 PM   #13
CM
 
Default Re: Energy savings from geothermal?

>>> If you want to use it for both summer cooling and winter
>>> heating, you must balance the thermal load to prevent the
>>> ground from icing up or overheating.

>
> Exactly what does that mean ,'balance the thermal load', and
> how do you do it? If it's winter, you're taking heat out,
> period. If it's summer, you're putting heat in, period.
> Either your heat sink area is sufficient to handle this,
> or it is not (an thus undersized).


Balanced over a full year's time. Unfortunately, there are few areas
where the total winter heating load matches the total summer
cooling load. That means that in most areas you must either add some
additional heat to the ground or remove some excess heat from the
ground.

>> Or, use separate areas of ground for heating and cooling.


> How exactly is that going to help anything ?
> Your'e still dumping all the heat in one place, and taking all
> your heat out from another.
> Sorry, your comment makes no sense.


A somewhat different approach, setting up one ground parcel to store
cold by circulating cold air or water or antifreeze during winter (or
night) to provide cooling during hot summer days, and setting up a
separate ground parcel to store summer warmth (perhaps from solar
collectors) for winter heating needs. More complicated and takes more
ground, but could achieve higher energy efficiency.

>> So, are you saying that the ground where you're doing this
>> can actually get iced up from the heat exchange process?


It can and it has.

>> Wouldn't that be a sure sign of an under-engineered loop?
>> Heat transfer spread over too small of an area, creating too
>> large of a temperature differential, and all that?

>
> Or perhaps that it's cold out :-)
> Obviously, yes. the loop is under-sized or miss-applied.


The ground is not an infinite source of heat, it is a reservoir. If
you keep removing more heat than is added, the reservoir will
eventually run empty. A larger reservoir simply delays the inevitable.

CM


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Old 06-04-2007, 05:45 PM   #14
CM
 
Default Re: Energy savings from geothermal?

>>> what are your general impressions of geothermal cooling
>>> systems, thermal experts?


>> Although it has considerable promise, there is hype and a lot of
>> misunderstanding on how it works.
>> Some people get the notion that the ground is mystically
>> maintained at a constant temperature no matter what, when
>> it is simply a matter of a very large thermal mass and some
>> insulation provided by the soil above. It is a thermal
>> reservoir. You put heat into the ground, the temperature will
>> go up. Draw heat out and the temperature will go down.


> wow


Basic physics. ;-)

>> If you want to use it for cooling only, you must remove the
>> excess heat from the ground when it is cold - at night, or
>> during winter.


> makes no sense.


Simple. Start with cold ground, and circulate your air through it,
cooling your house and slowly warming the ground. If that heat isn't
removed eventually, the ground with warm up too much to be of any use
in cooling. The best time to remove that stored heat is when it is
cold.

>> If you want to use it for heating only, you must replace
>> the heat that was removed by some means, or you will
>> eventually end up with a non-functioning permafrost ground.


> actually no.


If you dig deep enough, you can tap an enormous reservior that may
last centuries. But even that is not infinite.

Most geothermal heat pump systems are not that deep. If you keep
pumping heat out and not eventually replace that heat, the temperature
will drop, and eventually get too cold to efficiently extract any more
heat.

>> If you want to use it for both summer cooling and winter
>> heating, you must balance the thermal load to prevent the
>> ground from icing up or overheating. Or, use separate areas
>> of ground for heating and cooling.


> um, you seem to have proved your first point quite nicely,
> but not answered my question. I think you have no knowledge
> of this topic at all.


And your question was?
Oh, yes, "what are your general impressions of geothermal cooling
systems?" I did state my "general impressions".

Some of my "impressions" you wouldn't want to know.

CM



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Old 06-04-2007, 05:45 PM   #15
pjm@see_my_sig_for_address.com
 
Default Re: Energy savings from geothermal?

On Thu, 10 Jul 2003 21:04:15 GMT, "CM" <CM@CM.not.really> wrote:

>The ground is not an infinite source of heat, it is a reservoir. If
>you keep removing more heat than is added, the reservoir will
>eventually run empty. A larger reservoir simply delays the inevitable.
>
>CM


Unless you propose that a GSHP may cause the entire planet (
your ' reservoir' ) to freeze because you sucked all the heat up into
your living room, this is nonsense.

If it ever does, open the window and let the rest of us warm
up some :-0




Paul ( pjm @ pobox . com ) - remove spaces to email me
>~~>~~>~~>~~>~~>~~>~~>~~>~~>~~>~~>~~>~~>~~>~~>~~>~ ~>~~>~~


Coming soon - PMTherm version 2.0 !! http://pmilligan.net/pmtherm.htm
Free superheat charts for 38 Ref's online at http://pmilligan.net/pmtherm/
My personal site is at http://www.pmilligan.net ,
featuring free HVAC, psychrometric, stock market, and other software
http://helpthecritters.com/ is my domain for helping critters
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Old 06-04-2007, 05:45 PM   #16
pjm@see_my_sig_for_address.com
 
Default Re: Energy savings from geothermal?

On Thu, 10 Jul 2003 21:42:47 GMT, "CM" <CM@CM.not.really> wrote:

>If you dig deep enough, you can tap an enormous reservior that may
>last centuries. But even that is not infinite.


Yeh, but I'm pretty sure the pump will be out of warranty by
then anyway :-)

>Some of my "impressions" you wouldn't want to know.


I'd like to see your Henny Youngman. Do you do any
politicians ?




Paul ( pjm @ pobox . com ) - remove spaces to email me
>~~>~~>~~>~~>~~>~~>~~>~~>~~>~~>~~>~~>~~>~~>~~>~~>~ ~>~~>~~


Coming soon - PMTherm version 2.0 !! http://pmilligan.net/pmtherm.htm
Free superheat charts for 38 Ref's online at http://pmilligan.net/pmtherm/
My personal site is at http://www.pmilligan.net ,
featuring free HVAC, psychrometric, stock market, and other software
http://helpthecritters.com/ is my domain for helping critters
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Old 06-04-2007, 05:45 PM   #17
davehinz@spamcop.net
 
Default Re: Energy savings from geothermal?

In alt.energy.homepower CM <CM@cm.not.really> wrote:

> The ground is not an infinite source of heat, it is a reservoir. If
> you keep removing more heat than is added, the reservoir will
> eventually run empty. A larger reservoir simply delays the inevitable.


I think you are overestimating the insulative properties of earth
by orders of magnitude. When you are talking about an overall duty
cycle of one year, and expressing concerns, well, I'm sorry, but I
don't buy it.

Can you show me some sort of engineering guide which explains the
concerns that you are attempting to describe?

Dave Hinz


> CM




--
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Old 06-04-2007, 05:45 PM   #18
davehinz@spamcop.net
 
Default Re: Energy savings from geothermal?

In alt.energy.homepower CM <CM@cm.not.really> wrote:

> One of the first attempts to use a ground source heat pump was
> installed in Michigan. It worked fine the first winter, but conked out
> midway through the 2nd winter, and when they dug down to investigate,
> they found Permafrost.


And so this example is notable as an early learning-process failure.

>> Wouldn't that be a sure sign of an under-engineered loop?
>> Heat transfer spread over too small of an area, creating too
>> large of a temperature differential, and all that?


> The ground is a thermal reservoir, not an infinite source, and the
> input/output must be balanced. Using a larger loop area would mean
> tapping a larger reservoir. If unbalanced, it would take longer to
> stop functioning, but eventually it would stop functioning.


That is, if you could stop heat from leaking back into the cold
area, sure. Have you done the math on this one? I'm guessing
not.

> Of course, if you dig really deep, you can tap a much larger thermal
> reservoir of very hot rock that could provide heat for a few
> centuries!


Yes, Iceland and probably other places are using this source;
not in dug holes, but in ready-made ones. I think that it's good
for more than just a few centuries, though. The earth is big; lots
of thermal mass.

Dave Hinz
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