Geothermal heatpumps.

[eggs]

Hello all.

Firstly, from my understanding of domestic GSHP's, we have what to my way of thinking is a water cooled condensing unit whichs gives up it's heat to the radiators, underfloor heating etc.

Secondly, a water heated evaporator to take the heat from the ground, using a glycol ground loop.

is this correct?

Today i have been told of a system where there is no glycol used outdoors, just a dx evaporater buried in the ground, ie r407c running under ground, collecting heat.

Can this be corect?

What would happen if you sprang a leak say10m underground?
Would the refrigerant make its way to ground level or stay where it was and contaminate the ground?

Thanks for any help.

cheers

eggs

[US Iceman]

Hi Eggs,

The glycol is pumped through the bore-hole (ground) loop to absorb heat during the winter time. This glycol is returned to the evaporator to extract the heat from the glycol.

The refrigeration system transfers this heat plus some is added by the compressor. All of the heat is rejected to the building for heating purposes.

During the cooling cycle, the heat is removed from the building and dumped into the ground by the bore-hole(s).

Multiple bore-holes are usually required (or a single ground loop can be buried in the ground).

Any time you can transfer heat directly to a heat sink, the process becomes more efficient. With the glycol system, heat is transferred to the refrigerant, then to the glycol, then to the ground.

If the heat can be directly transferred from the refrigerant to the ground the process is more efficient. Less heat transfer steps.

I would hate to be the one who has to find and repair the underground refrigerant leak!

The oil leaking into the ground would be the bigger problem I think (from a contamination viewpoint).

GSHP's are interesting applications, but not without their own problems.

[Argus]

Given that GSHP is a rare beast in this country, direct systems do exist, but they are rare in the UK, almost to the point of extinction. I don?t know of any firms in the UK offering fully direct systems nowadays.

Firstly, you?ve highlighted the vulnerability to leakage. Secondly, given the volume of pipe distance and heat exchange size, etc. they are likely to hold a larger quantity of (potentially expensive) refrigerant than an equivalent indirect system.

The constraints within Europe, especially under the new F gas Regulations are to actively discourage unnecessarily large charges in systems.

The mean soil temperatures in the UK about 2 m depth are usually constant at about 12 ? 14 degrees with little seasonal variation. The efficiencies of a system will depend very much on the soil composition, water table etc ? in this temperature range, you should expect CoPs in excess of 4 with an indirect system. Economically, it makes little sense to do it any other way.

You need to be very careful what you put in the ground these days - the Environment Agency enforce ground pollution and have sharp teeth.

Additionally there is the aspect of ground water pollution. The Environment Agency is particularly keen on this and insists on biodegradable eutectic solutions in ground loops ? not just any old Glycol!

On the subject of refrigerants, waste refrigerant is now Hazardous Waste and needs a handling / storage licence; the EA is unlikely to be enthusiastic on potentially Hazardous Waste substances circulating in the water table.

.
________
vaporizer manufacturers

[Lc_shi]

GSHP is better than WSHP to protect underground water source,but more money needed for installation (drill the bore hole and lay the underground tube loops). I've not heard there is DX for outdoor units.

[eggs]

thanks for the replies i got.

the reason i ask about these things is sure to concern us all.

A very large plumbing and heating company, where i have the service and install contracts, rang me to ask about GSHP's. To which, i asked why?
He tells me about the difficulty now in obtaining planning permission for new domestic houses unless the builders use an energy efficient heating alternative to gas boilers.
ie GSHP's or Air heatpumps.

The plumbing company are installing 2 trial systems for the builder to evaluate efficiency.

Judging by the lack of responce i am assuming people in the uk are as ignorant of the systems as i am. If we dont swot up on them quickly our future business could be lost to plumbers. GSHP's are heading to a building site near you SOON!

cheers

eggs

[US Iceman]

HI Eggs,

A couple of sites for you to review.

http://www.geoexchange.org/

http://www.motherearthnews.com/libra...ay/The_Big_Dig

http://geoheat.oit.edu/pdf/tp72.pdf

There are a lot of sources. Some of the best ones come from the northern European countries as they are doing a lot of research on this topic.

[Lc_shi]

Hi Iceman
GSHP is introducing into our country and the potential is great. But it need many areas technology,especially the geologic investigation of the installation site. How about the situation in USA, is there specific company providing the bore hole and underground HX construction services?

rgds
LC-

[US Iceman]

Hi LC,

The people who seem to be doing most of the ground loops and bore holes are the companies who do drill water wells. They have all of the equipment to do the drilling and well casing, so the loops for the bore holes or ground loops compliments their existing business.

One other method I have seen is the use of coil loops installed in lakes. The lake water provides the heat sink/source for the heat pumps.

I worked on a project where a soil engineer was employed to review the soil conditions for; ground water level, conductivity, and other soil properties. All of which you need to model the heat dissipation or absorption of the glycol loop.

You can purchase some design books from:

http://www.igshpa.okstate.edu/

Look under the Publication link. I have one of these books and it is very well written.

Here is link to the ASHRAE website for another design manual.

http://resourcecenter.ashrae.org/sto...ps&method=and&

Here is a link for a manufacturer. Additional information can be found at this website.

http://www.waterfurnace.com/

These heat pumps can be installed as closed loop (using plastic tubing and glycol), or, as on open loop (circulating well or lake water, without a heat exchanger) using glycol.

The open loop heat pump basically looks like a water chiller using a water-cooled condenser. Filters will be required on open loop systems to reduce the fouling of the refrigeration evaporator (chiller).

One area that requires a good investigation is the soil itself. You need to know how fast the soil will dissipate the heat during the AC cycle, and how fast can the heat be absorbed during the heating cycle. (another modeling problem to work on )

Hope this helps.

US Iceman

[anup]

Hi Eggs, LC
One very good site to under stand GSHP is www.retscreen.org. It gives you how to design GSHP and other important information on GSHP.
Once you subscribe to their mailer, you even get software updates.
I know one company in Canada who deals in GSHP and have about 23 yrs of expereince. I will post the details on Sunday, as I am traveling.

[fixit]

Hi egg, like your sig., Do i need a fire wall or anti spy ware?
There is a Dx system that evaporates at around -5 oC(www.Avenir-energie.com) which comes ready to install, plastic coated copper pipe.
Dealers say it takes up less Ground loop area. The difficulty with this is you now have less area to absorb the heat from and i have heard of a grounds works contractor came a cross a block of frozen earth 2M x 4M x 5M long and needed a machine breaker to lay a service pipe .
The soil at a metre deep is around 7 - 10 oC until you start cooling it which can run down to below 0 oC, that is why when using a heat exchanger and a transfer fluid you need glycol.If the ground is around 12 oC why need the glycol.

[US Iceman]

Dealers say it takes up less Ground loop area. The difficulty with this is you now have less area to absorb the heat from and i have heard of a grounds works contractor came a cross a block of frozen earth 2M x 4M x 5M long and needed a machine breaker to lay a service pipe .

I agree. The heat transfer for the ground loop is much better for a direct expansion coil, rather than a glycol circuit. The statement above also confirms the need to do a comprehensive soil study before burying a heat exchanger in the ground.

If the depth is too shallow, the soil frost line can be very close to the heat exchanger. This limits the available heat to the heat exchanger.

Secondly, if the heat exchanger circuits are too close in proximity to other circuits, you end up with cold spots which impede the flow of heat to the heat exchanger circuits.

A direct expansion may be more efficient and less costly than a glycol loop, but you do need a sufficient area of soil, at the right depth, to make a GSHP effective for long term use.

Direct expansion must also have some interesting characteristics for oil return also.

[Peter_1]

I'm a member of the IGHSPA. I think I have all their manuals.
You can also find a lot on the net.
Nordic explains on their siste how to install and how to solder the pipes for a proper oil return.

Lichuan knows that I'm very fond of the DX system and it's by far the best way of heating (via the refrigerating technology) You always have to combine it with a low water temperature system (radiant heating is the best)

I think I have at least 3,000 printed pages of all different subjects i found on the net, GHSP related and many of them are DX related.

Copper tubes in the ground: they still dig up coins from Ceasar under the ground, they find them in the sea.
And if you're afraid, you still can use an inexpensive cathodic protection for teh copper.

If one leaks, well the refrigerant wil escape through the soil in the air.
The oil is like US Iceman said a bigger problem. A good solution for this could be a copper tube in a copper tube with a pressure sensing device between the 2 tubes to alert you that there's a leak.
This system is also obligated now in Belgium on fuel reservoirs.

4We're right now making our own borehole machine for a depth tille 75 feet and we already did some tests with a smaller unit.
We even made a bit for a rather big hydraulic machine to do this job.
But you don't need heavy equipment to drill a hole of 5 to 6 inches wide in the Belgium soil.

+/- 70% of the new heating systems in Switzerland - or is it Austria- are GSHP.
In Germany and The Netherlands, they're installing large units which can heat 30 to 70 houses at once.

In the last ACHR news of this week was an article about GSHP.

Due to the growing environmental care, I predict a very fast growing for this way of heating.

And have you ever thought at the huge benefits you can achieve with the ground as a condenser during summer, always at a temperature of +/- 12°C?

[Peter_1]

www.retscreen.org[/url]. It gives you how to design GSHP and other important information on GSHP.

Link seems not working.

[US Iceman]

Peter,

I was not aware that DX for GSHP was used this often. Can you provide a link where I can read more information.

Thank you.

[US Iceman]

I remember for one application for the Trans-Alaskan oil pipe line where thermosyphon systems where used with ammonia.

The thermosyphon systems were used to prevent the permafrost from melting under the pipe supports. Perhaps something like this could be used for the geothermal systems also.

Peter, what do you think?

[Peter_1]

Some good links on this subject

http://copper.org/copperhome/PHC/phc_heating.html

http://www.nordicghp.com/mg/pumps/dx_series.htm
They also give you a schematic for the oil trap on
http://www.nordicghp.com/mg/PDF/pdfdxmanual.PDF

A fast growing Gernman manufacturer
http://www.waterkotte.de/english/index.html

This is the drill we're planning to make one of these days when we find some spare time
http://www.littlebeaver.com/prod_bigbeaver.php
The spirals for the auger came from a company in The Netherlands.

http://www.engr.utk.edu/mabe/maesold...son/hunley.htm

Another type of coil they tried out here
http://www.engr.utk.edu/mabe/maesold...nson/moore.htm

http://www.commandaire.com/products/...72-9042-02.pdf

This is also a good one and you can download older already published articles
http://www.heatpumpcentre.org/

http://www.etis.net/common/tech/tech019/tech019.pdf

Mitsubishi has made some time ago some sort of a 'thermosiphon split' to cool telecommunication/broadcasting cabines (relay stations)
There was no compressor in it and they used the always colder outside temperature to condens the vapors again.

There can also a lot of information be found in the patent databases.

I also have somewhere info about a cathodic protection report from the US Navy bu this is another one http://www.sam.usace.army.mil/en/cp/presentations.htm

[US Iceman]

Peter,

Thank you for the information you provided on the GSHP's. Some of the information is new to me (the DX loops). I will review these links with great interest.

On the thermosiphons: I have done several different version of these for heat reclaim and have had very good results. I have seen some reports where a thermosiphon was used to heat a bridge and roads to prevent icing during winter.

This is a fascinating area I highly recommend to other members of the RE forum.