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Home > Archive > Alternative Power sources > December 2006 > CO2 Pipe Dream
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| I think the future of ground source heat extraction might be bore holes with
a single copper tube 2-3 inches in diameter, and say 100-200 feet long
filled with a benign refrigerant that simply boils from the heat in the
ground. When the heat pump collapses the vapour from header connecting the
borehole pipes, the vapour pressure is reduced and the refrigerant in the
vertical pipes starts to boil thereby releasing latent heat. Transfering
heat through the pipe with latent energy is an efficient scheme I would
think. When the vapour is collapes at the condenser heat exchanger, the
liquid drains back to keep the tubes filled by gravity. Simple. This method
is a bit like the old single steam pipe heating schemes of days gone by. In
a sense the ground becomes the boiler with a never ending fuel supply. The
heat transfer process would be extremely efficient and could eliminate a
pumped condenser loop entirely. Maybe CO2 would work as a refrigerant but
I'm speculating. CO2 would be extracted from the atmosphere and therefore
benign. The key refrigerant, whatever it is would need to be benign and
operate under the appropriate pressure. Just a thought.
Jack
| |
| Eeyore 2006-12-07, 8:25 pm |
|
Jack wrote:
> I think the future of ground source heat extraction might be bore holes with
> a single copper tube 2-3 inches in diameter,
Why copper ?
Graham
| |
| Vaughn Simon 2006-12-07, 8:25 pm |
|
"Eeyore" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:4578BB7C.FBF2697F@hotmail.com...
>
>
> Jack wrote:
>
>
> Why copper ?
What would you suggest?
Vaughn
>
> Graham
>
| |
| Eeyore 2006-12-07, 8:25 pm |
|
Vaughn Simon wrote:
> "Eeyore" <rabbitsfriendsandrelations@hotmail.com> wrote in message
>
> What would you suggest?
Something less expensive ! Ideally something flexible too. Incidentally I've had
underground copper pipe work corrode ( due to impurities ).
High density plastic seems to be favoured. You also need a heck of a lot more
length btw AIUI.
Graham
| |
| Solar Flare 2006-12-07, 9:25 pm |
| The ground is not an endless supply of heat at the rate you would need
it unless there is circulation going on.
"Jack" <Joe@nowhere.com> wrote in message
news:P6Sdna17k9WSLuXYnZ2dnUVZ_vmdnZ2d@tbaytel.net...
>I think the future of ground source heat extraction might be bore
>holes with a single copper tube 2-3 inches in diameter, and say
>100-200 feet long filled with a benign refrigerant that simply boils
>from the heat in the ground. When the heat pump collapses the vapour
>from header connecting the borehole pipes, the vapour pressure is
>reduced and the refrigerant in the vertical pipes starts to boil
>thereby releasing latent heat. Transfering heat through the pipe with
>latent energy is an efficient scheme I would think. When the vapour
>is collapes at the condenser heat exchanger, the liquid drains back
>to keep the tubes filled by gravity. Simple. This method is a bit
>like the old single steam pipe heating schemes of days gone by. In a
>sense the ground becomes the boiler with a never ending fuel supply.
>The heat transfer process would be extremely efficient and could
>eliminate a pumped condenser loop entirely. Maybe CO2 would work as a
>refrigerant but I'm speculating. CO2 would be extracted from the
>atmosphere and therefore benign. The key refrigerant, whatever it is
>would need to be benign and operate under the appropriate pressure.
>Just a thought.
>
>
> Jack
>
| |
| Jens Kr. Kirkebø 2006-12-08, 3:25 am |
| On Thu, 7 Dec 2006 19:34:19 -0600, "Jack" <Joe@nowhere.com> wrote:
>I think the future of ground source heat extraction might be bore holes with
>a single copper tube 2-3 inches in diameter, and say 100-200 feet long
>filled with a benign refrigerant that simply boils from the heat in the
>ground.
Actually, this is the past, not the future. It was done this way in
the 80's. Beause of complexity, amount of refridgerant needed, a large
possibility of leaks, high maintenance and too much heat extraction
per feet of bore hole, the scheme was abandoned in favor of the heat
exchanger system now used.
And you can't remove much heat from a 100 feet hole. Mine is 650 feet
deep... ~60 feet active depth (below water table) per kW delivered is
a good start.
| |
| daestrom 2006-12-08, 9:25 am |
|
"Jack" <Joe@nowhere.com> wrote in message
news:P6Sdna17k9WSLuXYnZ2dnUVZ_vmdnZ2d@tbaytel.net...
>I think the future of ground source heat extraction might be bore holes
>with a single copper tube 2-3 inches in diameter, and say 100-200 feet long
>filled with a benign refrigerant that simply boils from the heat in the
>ground. When the heat pump collapses the vapour from header connecting the
>borehole pipes, the vapour pressure is reduced and the refrigerant in the
>vertical pipes starts to boil thereby releasing latent heat. Transfering
>heat through the pipe with latent energy is an efficient scheme I would
>think. When the vapour is collapes at the condenser heat exchanger, the
>liquid drains back to keep the tubes filled by gravity. Simple. This method
>is a bit like the old single steam pipe heating schemes of days gone by. In
>a sense the ground becomes the boiler with a never ending fuel supply. The
>heat transfer process would be extremely efficient and could eliminate a
>pumped condenser loop entirely. Maybe CO2 would work as a refrigerant but
>I'm speculating. CO2 would be extracted from the atmosphere and therefore
>benign. The key refrigerant, whatever it is would need to be benign and
>operate under the appropriate pressure. Just a thought.
>
What you're describing is similar to the 'heat pipes' used to keep the
foundation under the Alaska pipeline frozen. But instead of a compressor at
the top, they just use fins exposed to arctic air.
A ground source heat pump can be a good technology for home heating in some
areas. But you're idea is greatly increasing the size of the refrigerant
cycle to include the buried piping.
Traditional ground-source heat pumps use a second loop of fluid for the
underground portion. This allows it to operate at lower pressures without a
need for vacuum. They also typically use simple, safe fluids such as water
so minor leakage is envrionmentally safe. Make-up supply is also easier.
Extending the refrigerant loop under ground means much more refrigerant and
much higher chance of leakage. Even using a benign gas such as CO2,
re-charging a leaky refrigerant loop is not as simple as 'topping off' a
vented water tank.
For CO2 to be used, you have to have it under the right pressures for
liquification at something above home temperatures and gasification below
ground temperatures.
Even with all this, ground-source is *not* an endless supply of heat for
everyone. Soil conditions play a *major* role in how much heat can be
extracted from a given 'well'. Hard granite versus wet sand can be an order
of magnitude different. In most areas that use them, they use either
several hundred feet of 'slinky' loops, several deep conduction pipes, or
two open loop ground water wells.
daestrom
| |
| daestrom 2006-12-08, 1:25 pm |
|
"daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote in message
news:O_deh.523$nq5.138@twister.nyroc.rr.com...
>
> "Jack" <Joe@nowhere.com> wrote in message
> news:P6Sdna17k9WSLuXYnZ2dnUVZ_vmdnZ2d@tbaytel.net...
>
> What you're describing is similar to the 'heat pipes' used to keep the
> foundation under the Alaska pipeline frozen. But instead of a compressor
> at the top, they just use fins exposed to arctic air.
>
> A ground source heat pump can be a good technology for home heating in
> some areas. But you're idea is greatly increasing the size of the
> refrigerant cycle to include the buried piping.
>
> Traditional ground-source heat pumps use a second loop of fluid for the
> underground portion. This allows it to operate at lower pressures without
> a need for vacuum. They also typically use simple, safe fluids such as
> water so minor leakage is envrionmentally safe. Make-up supply is also
> easier. Extending the refrigerant loop under ground means much more
> refrigerant and much higher chance of leakage. Even using a benign gas
> such as CO2, re-charging a leaky refrigerant loop is not as simple as
> 'topping off' a vented water tank.
>
> For CO2 to be used, you have to have it under the right pressures for
> liquification at something above home temperatures and gasification below
> ground temperatures.
>
CO2 would probably be a bad choice. If the ground is 30F, it would boil
when the pressure is 490 psia or less. But to liquify it at 85F in the
house, its pressure has to be raised to over 1033 psia. And for all that
work/energy to pressurize it and liquify it, CO2 only gives off about 3.2
kJ/mol in the process (compared to more than 43 kJ/mol for water vapor and a
lot less mechanical work to liquify it).
daestrom
| |
|
|
"daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote in message
news:O_deh.523$nq5.138@twister.nyroc.rr.com...
>
> "Jack" <Joe@nowhere.com> wrote in message
> news:P6Sdna17k9WSLuXYnZ2dnUVZ_vmdnZ2d@tbaytel.net...
>
> What you're describing is similar to the 'heat pipes' used to keep the
> foundation under the Alaska pipeline frozen. But instead of a compressor
> at the top, they just use fins exposed to arctic air.
>
> A ground source heat pump can be a good technology for home heating in
> some areas. But you're idea is greatly increasing the size of the
> refrigerant cycle to include the buried piping.
>
> Traditional ground-source heat pumps use a second loop of fluid for the
> underground portion. This allows it to operate at lower pressures without
> a need for vacuum. They also typically use simple, safe fluids such as
> water so minor leakage is envrionmentally safe. Make-up supply is also
> easier. Extending the refrigerant loop under ground means much more
> refrigerant and much higher chance of leakage. Even using a benign gas
> such as CO2, re-charging a leaky refrigerant loop is not as simple as
> 'topping off' a vented water tank.
>
> For CO2 to be used, you have to have it under the right pressures for
> liquification at something above home temperatures and gasification below
> ground temperatures.
>
> Even with all this, ground-source is *not* an endless supply of heat for
> everyone. Soil conditions play a *major* role in how much heat can be
> extracted from a given 'well'. Hard granite versus wet sand can be an
> order of magnitude different. In most areas that use them, they use
> either several hundred feet of 'slinky' loops, several deep conduction
> pipes, or two open loop ground water wells.
>
> daestrom
That was informative, thank you,
Jack
>
| |
| Harbin Osteen 2006-12-10, 3:25 am |
| Howdy:
I have always wondered if there is a point of extraction, where the ground loops
of a heat pump would extract enough heat, that the system would become less efficient. It seems to
me that you would have to pump heat into the ground in the summer, and extract
heat in the winter unless you are in some geo active area. Does anybody know
if you can extract enough heat to make a heat pump fail? Or can the heat move
through the earth fast enough to keep the system efficient?
--
SeeYaa Harbin Osteen KG6URO
When American Citizens with dual citizenship pledges allegiance
to the flag, to which flag do they pledge allegiance too?
-
"Jack" <Joe@nowhere.com> wrote in message news:SN2dnQoR6PL_b-TYnZ2dnUVZ_oytnZ2d@tbaytel.net...
>
> "daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote in message news:O_deh.523$nq5.138@twister.nyroc.rr.com...
>
> That was informative, thank you,
>
> Jack
>
>
| |
| Jens Kr. Kirkebø 2006-12-10, 5:25 pm |
| On Sat, 9 Dec 2006 23:01:22 -0800, "Harbin Osteen"
<harbinjr@adelphia.net> wrote:
>Howdy:
> I have always wondered if there is a point of extraction, where the ground loops
>of a heat pump would extract enough heat, that the system would become less efficient. It seems to
>me that you would have to pump heat into the ground in the summer, and extract
>heat in the winter unless you are in some geo active area. Does anybody know
>if you can extract enough heat to make a heat pump fail? Or can the heat move
>through the earth fast enough to keep the system efficient?
If you extract too much heat too fast, the hole can freeze up. Usually
it will continue to work, but at a lower efficiency. Sometimes the
freezing can squeeze the pipe so that everything stops. How many feet
of well you need per kW extracted varies with ground conditions. 60-65
feet is a good number for granite, in sandstone you'll need more.
Never count depth above the water table.
If you use the hole for cooling in the summer, you'll "recharge" it
somewhat. How much effect this has depends on how much water passes
through the hole. More water is better but minimizes the "recharge
effect" as the water transfers the heat away.
| |
| Harbin Osteen 2006-12-10, 8:25 pm |
| Not all heat pumps have the coils below the water table do they?
"Jens Kr. Kirkebø" <jkk@scm.no> wrote in message news:q6son21gdfao6vm4gccqihh19ia0hv294b@4ax.com...
> On Sat, 9 Dec 2006 23:01:22 -0800, "Harbin Osteen"
> <harbinjr@adelphia.net> wrote:
>
>
> If you extract too much heat too fast, the hole can freeze up. Usually
> it will continue to work, but at a lower efficiency. Sometimes the
> freezing can squeeze the pipe so that everything stops. How many feet
> of well you need per kW extracted varies with ground conditions. 60-65
> feet is a good number for granite, in sandstone you'll need more.
> Never count depth above the water table.
>
> If you use the hole for cooling in the summer, you'll "recharge" it
> somewhat. How much effect this has depends on how much water passes
> through the hole. More water is better but minimizes the "recharge
> effect" as the water transfers the heat away.
| |
| daestrom 2006-12-10, 8:25 pm |
|
"Harbin Osteen" <harbinjr@adelphia.net> wrote in message
news:HoWdnQx58JReLebYnZ2dnUVZ_tyinZ2d@adelphia.com...
> Howdy:
> I have always wondered if there is a point of extraction, where the
> ground loops
> of a heat pump would extract enough heat, that the system would become
> less efficient. It seems to
> me that you would have to pump heat into the ground in the summer, and
> extract
> heat in the winter unless you are in some geo active area. Does anybody
> know
> if you can extract enough heat to make a heat pump fail? Or can the heat
> move
> through the earth fast enough to keep the system efficient?
>
It's more a question of heat flowing from the deep underground upward past
your system. If the local soil conditions are bad (solid granite), and you
don't have a huge loop, then you can 'pump' heat out of the ground
surrounding the loop faster than it seeps into the area from
surrounding/underneath.
If the soil conditions are good and/or there is underground water table
flowing past, then heat can 'flow' into the soil around your loop much
faster and it can keep up with your demands.
If the soil is poor and heat flow can't keep up, then the temperature of the
loop keeps dropping. As it drops, the heat pump has to work harder to move
the same amount of heat (or, put another way, you get less heat from the
ground for a given kwh input to the heat pump).
Trying to 'store' heat in a very large ground loop for six months isn't
practical unless you've dug up a huge area and insulated it :-)
daestrom
| |
|
| One misconception about the ground is the ability to store energy without
insulation.
If we place a slab on the ground and heat it with hot water tubes. the heat
is lost to the ground in a downward fashion assuming peripheral insulation.
The heat will conduct so long as there is a temperature difference. However,
the ground (no water table) is quite capable of reliably storing heat since
that region of heat is essentially surrounded by an infinately thick layer
of poor insulation. Once the heat has migrated about 5 feet or so into the
ground below the slab, the temperature difference has essentially diminished
to nothing in which case heat ceases to flow. Sink several vertical bore
hole heat exchangers in a localized spot, and you will create a region of
heat storage barring no fast moving ground water. Most heat pump systems
that fail, usually fail due to the imbalance between heating and cooling
after episodes over which several years of operation take their toll on
nominal ground temperature.
Jack
"daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote in message
news:Ac1fh.36490$zB4.14764@twister.nyroc.rr.com...
>
> "Harbin Osteen" <harbinjr@adelphia.net> wrote in message
> news:HoWdnQx58JReLebYnZ2dnUVZ_tyinZ2d@adelphia.com...
>
> It's more a question of heat flowing from the deep underground upward past
> your system. If the local soil conditions are bad (solid granite), and
> you don't have a huge loop, then you can 'pump' heat out of the ground
> surrounding the loop faster than it seeps into the area from
> surrounding/underneath.
>
> If the soil conditions are good and/or there is underground water table
> flowing past, then heat can 'flow' into the soil around your loop much
> faster and it can keep up with your demands.
>
> If the soil is poor and heat flow can't keep up, then the temperature of
> the loop keeps dropping. As it drops, the heat pump has to work harder to
> move the same amount of heat (or, put another way, you get less heat from
> the ground for a given kwh input to the heat pump).
>
> Trying to 'store' heat in a very large ground loop for six months isn't
> practical unless you've dug up a huge area and insulated it :-)
>
> daestrom
>
| |
| Jens Kr. Kirkebø 2006-12-11, 9:25 am |
| On Sun, 10 Dec 2006 15:59:05 -0800, "Harbin Osteen"
<harbinjr@adelphia.net> wrote:
>Not all heat pumps have the coils below the water table do they?
In a bore hole system you have to surround the tube with something. If
there's no water in your hole, or it's far down, you can fill the hole
with a fine-grained sand. If not, the pipe won't hold it's own weight
and fall apart. Also, air is a far too good insulator.
In a buried pipe system though, there is earth all around the pipe and
the water table is usually below the pipe.
| |
| Jens Kr. Kirkebø 2006-12-11, 9:25 am |
| On Mon, 11 Dec 2006 00:00:32 GMT, "daestrom"
<daestrom@NO_SPAM_HEREtwcny.rr.com> wrote:
>It's more a question of heat flowing from the deep underground upward past
>your system. If the local soil conditions are bad (solid granite), and you
>don't have a huge loop, then you can 'pump' heat out of the ground
>surrounding the loop faster than it seeps into the area from
>surrounding/underneath.
Misconception. The heat isn't from the earths core, it's from the sun.
Approx. 99% of what you extract is stored sunlight so there's no heat
"flowing from the deep". Granite is one of the best rock types for a
good-performing energy well.
| |
| Harbin Osteen 2006-12-12, 3:25 am |
| Hi Jack:
This brings up another question. There is some debate about whether
or not to insulate the slab of a underground house, or a house like a "Earthship".
Some say to leave it un-insulated so the earth will act like a heat sink, which
has a cycle of about 6 months of absorbing and releasing heat, where
the other opinion says to insulate the slab, and use the mass of the house only
as the heat sink. Any opinions on which might be correct, or more efficient?
--
SeeYaa Harbin Osteen KG6URO
When American Citizens with dual citizenship pledges allegiance
to the flag, to which flag do they pledge allegiance too?
-
"Jack" <Joe@nowhere.com> wrote in message news:O7Gdnc0l6-6cOOHYnZ2dnUVZ_ua3nZ2d@tbaytel.net...
> One misconception about the ground is the ability to store energy without insulation.
>
> If we place a slab on the ground and heat it with hot water tubes. the heat is lost to the ground in a downward fashion assuming
> peripheral insulation. The heat will conduct so long as there is a temperature difference. However, the ground (no water table) is
> quite capable of reliably storing heat since that region of heat is essentially surrounded by an infinately thick layer of poor
> insulation. Once the heat has migrated about 5 feet or so into the ground below the slab, the temperature difference has
> essentially diminished to nothing in which case heat ceases to flow. Sink several vertical bore hole heat exchangers in a
> localized spot, and you will create a region of heat storage barring no fast moving ground water. Most heat pump systems that
> fail, usually fail due to the imbalance between heating and cooling after episodes over which several years of operation take
> their toll on nominal ground temperature.
>
> Jack
>
> "daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote in message news:Ac1fh.36490$zB4.14764@twister.nyroc.rr.com...
>
>
| |
| daestrom 2006-12-12, 5:25 pm |
|
"Harbin Osteen" <harbinjr@adelphia.net> wrote in message
news:Uc-dneBo1ZhGs-PYnZ2dnUVZ_tadnZ2d@adelphia.com...
> Hi Jack:
> This brings up another question. There is some debate about whether
> or not to insulate the slab of a underground house, or a house like a
> "Earthship".
> Some say to leave it un-insulated so the earth will act like a heat
> sink, which
> has a cycle of about 6 months of absorbing and releasing heat, where
> the other opinion says to insulate the slab, and use the mass of the house
> only
> as the heat sink. Any opinions on which might be correct, or more
> efficient?
>
Guess that would all depend on the average ground temperature. Here in
upstate NY, the ground five or six feet down is always between 50 and 60F.
Makes for a cool basement or slab in the summer, but a bit too cool for
winter.
So if the average ground temperature is near 'comfort zone', maybe not. But
if it's cold climate, you probably want to insulate.
daestrom
| |
| nicksanspam@ece.villanova.edu 2006-12-12, 5:25 pm |
| daestrom <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote:
>... Here in upstate NY, the ground five or six feet down is always between
>50 and 60F.
With enough solar energy, that can be raised, locally-speaking.
Nick
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