I've been reading about ground source heat pump systems that circulate
water or a colant through pipes burried below the frost line. In these
systems, the water/colant is used to sink heat from a compressor unit.

I'm interested in setting up a system *without* a compressor. I'd
circulate the water directly into a fan coil with a small curulating
pump. This would seem to be much cheaper to set up and operate.

I'm looking for information about how people may have done this in the
past, or why it is infeasible to do.

The one person I asked said it was not possible becuase the delta T is
too small. The water coming out of my well now is about 55F, which is
cold enough to condense water on the pipes, so I figure it is cold
enough at least to de-humidify my air if I circulate it though a fan
coil.

If it is possible, I'd love info on how to size the system, pick a
pump size/rate, pick a fan coil, etc.

---

Request for Question Clarification by hedgie-ga on 06 Jul 2004 12:29 PDT

Hi josh

It depends a bit on what you mean by 'possible' .

It certainly is possible to immerse the heat exchanger
into the heat sink (well) and it will save something on the operating cost.

Usually decision is based on the cost of equipment vs
cost of long term saving on electricity.
In addition to T of the well you would need 
data, such as cost of energy,  typical energy consumption of conventional
air conditioning, temperature outside and time horizont for return on investment.
If you will do calculation/estimates of cost yourself, I can find some
case histories and formulas. Would that be sufficient answer?

hedgie

---

Clarification of Question by bigjosh-ga on 06 Jul 2004 13:18 PDT

What I am imagining would seem to be both cheaper to install and cheaper to run. 

In a normal system, you have a fan coil connected by a loop to the
heat pump, and the puump connected by a loop to the ground.

In my system, I'd have the fan coil connected directly to the ground
loop with a very small circulating pump.

Easier/cheaper install - no heat pump, no refrigerant. Just a little
normal low pressure plumbing work.

Cheaper to run - the compressor in a heat pump is a *big* motor that
uses lots of electricity. Since my system is simply a closed loop of
water, I'd only need a tiny motor to keep the water moving, and a tiny
motor to move the air through the fan coil.

So the questions is - has anyone tried this and if not, why?

Thanks!

---

Request for Question Clarification by hedgie-ga on 06 Jul 2004 22:27 PDT

OK josh, I think I get it:

 The question is:  Could a gheothermal exchange cooling system 
 without a compressor be more efficient then the typical heat GCHP.
 
 In the typical system, there is a closed loop 
 which circulates the secondary liquid (e.g. water, anifreeze  or methanol)
 through the house and  geothermal reservoir (pond, well, ground water . .).
 Inside the house, there is one or more conventinal heat pump (each
with a compressor)
 which will produce cool air.
 
 In the simpler system you are considering, heat pump(s) are replaced by fan coil
 heat exchanger. There is no compressor in the system.
 
 
  Efficiency is measured by cost,  EER, and COP, which are defined e.g. here
  http://home.howstuffworks.com/ac4.htm
  
  
  Encycopedia 
  http://en.wikipedia.org/wiki/Geothermal_exchange_heat_pump
   says:
  Heat-pump "typically consist of a loop of pipe, a compressor, and a pump" 
  
  Since the system proposed does pump heat,
  we can classify it as  atypical or unconventional  geothermal heat pump.
  
  Let's call it compressionless secondary fluid GCHP system
  
  Question is: why are they not widelu used?  are they too inefficient?
  or, are they used?  How does their efficiency compares to conventional GCHP?
  
   Is that correct understanding of your question?

hedgie

This is the answer to your question:

 Yes, system is feasible and is being used,
 but rarely. 
 It may be the best in some less demanding situations.
 
  Concerns and critique expressed in the comment are not 
  valid or applicable. The waste heat dissipation issue in
  conventional (HP based) geothermal cooling is same is in your
  ACC  geothermal cooling and those conventional GSHPs have been
tested and used without problems.
  
  Main issue is finding fan-coil unit which would deliver required
  (negative) BTUs at very small temperature difference, at reasonable
  cost and space requirement.  I will give links to available units
and studies at the end.
   
   First, let's adopt terminology:
   ===============================
  
   Water loop system (described at this site, URL below)) -- 

   System can operate either with heat pumps  OR
   with fan coils in the rooms

   A cooling tower, boiler OR geothermal heat (sink/source) OR thermal
storage (roof pond)
   can each or all be attached to the water loop.
   http://www.advancedbuildings.org/_frames/fr_search.htm
  
 There is a term, even acronym ACC
  Alternatives to Compressor Cooling (ACC)  

  with it's own research team at University of California Davis,
  which is hower is limiting itself to 'nightbreeze' concept
  - using cold night air, rather then geothermal to heat homes
  http://www.fsec.ucf.edu/bldg/pubs/pf273/
  
  However, your concept is also ACC and I would classify it 
  (after spending  too much time on researching this) as ACC GSHP  system

Then  
  Let's look and some case histories
  ====================================
  
Is it being used?   YES

"Core areas often require cooling well into the heating season. These
heat pumps can also use free cooling with economizer coils. When the
outdoor temperature is low enough, cold tower water is used without
operating the compressors. "
The loop temperature could be reduced to about 50 degrees if the water
bypasses the ground coil through a three-way valve. The core zones
could be cooled without using the compressors and the perimeter heat
pumps could operate in the heating mode. Even with near 50-degree
water to the perimeter heat pumps, the heating COP is about 4.0.

http://ies.lbl.gov/iespubs/45303.pdf 

Note the 'could'  in "could be cooled without using the compressors" 

 Key issue is (as you mentioned) that 'small temperature difference' makes
 heat exchanger inefficient. However, the situation is not as bad as
the commenter (was it neilzero (again?)) paints it as  would not use
radiators but fan-coils. We may use closed water loop, probably with
antifreeze, which has higher thermal capacity and allows control of
corrosion. That depends on the water quality (dissolved minerals). 
Neither closed or  open loop, would 'poison the water supply' nor will
it 'pump the well dry' since water is returned. There are
environmental regulation for open loop, which differ in different
jurisdiction, but it is usually OK and cheaper to go open loop.
 
 Here is info on 
 SEARCH TERM: Open Water or Open Well GSHP Systems 
 
...An open well system borrows water from a dug or a drilled well,
then directs the water through the GSHP system. Heat is then extracted
from the water in winter or rejected in summer, then the cooled/heated
water is returned to a pond, river, lake, weeping discharge pit or
discharge well, in accordance with local environmental regulations.
Depending on the location, the standard environmental "rule of thumb"
is to return the water that is utilized to the same aquifer level, at
another point on the same property, where the water was originally
drawn. A Geothermal System does nothing to negatively affect the water
quality that it uses, it absorbs or rejects heat only. The discharge
system must be designed to accommodate any locally sensitive
environmental issues.

If the source of water is a lake, river or pond, the body of water
must be large enough to provide a sufficient 'heat sink' capacity.
Rivers can be used as a source of water, but sources with high levels
of salt, chlorides or other minerals are not recommended for most
units. Each region/province/state has regulations concerning the use
of water and if a closed loop is used in the body of water, there are
generally laws/guidelines concerning the position of GSHP loops in
navigable waterways.

http://www.enertran.ca/geoinfo.html#aa7

 
So, your ACC GSHP IS USED - but  rarely. Actually, any GSHP is used
rarely for residential cooling, according to this site:
 
Space Cooling 
Geothermal energy has seldom been used for cooling, although emphasis
on solar energy and waste heat has created interest in cooling with
thermal energy. The absorption cycle is most often used and
lithium-bromide/water absorption machines are commercially available
in a wide range of capacities. Temperature and flow requirements for
absorption chillers run counter to the general design philosophy for
geothermal systems. ...

Page 22
Caution : very long URL's get broken in browser the whole string in []
needs to be pasted into 'location box' but without the []
[
http://216.239.59.104/search?q=cache:2a0XXjlHhj4J:www.tess-inc.com/tc68/Ch31Update_IP.pdf+comparison+of++fan-coil,+%22small+temperature+difference%22&hl=en&lr=lang_en&ie=UTF-8
]
 
 
    So, in conclusion:
   ====================
     YES  it is feeasible and in some situations
  (high outside temperature, moderate requirments (e.g. 75 F result)) 
   it may be the best method. It is used rarely since in most cases you get
   more performance (guaranteed 70F) for little bit more energy
consumption and cost.
   
   Key issue would be selection and cost/performance of the fan-coil units (RFCs).
   I will give resources for selection/comparing RFCs and comparison
with Heat Pumps (HPs)
   
   Here is one cost study, which evaluated different systems (and picked HPs):
   
    This case study compares total cost  og using heat-pumps and fan-coils on the 
  geothermal conventional water loop. In this case, GHP was selected,
but number may come out differetly in other cases.
  http://oee.nrcan.gc.ca/Publications/infosource/Pub/ici/caddet/english/pdf/R409.pdf
  
 
  An ACC GHP system, you described, can be combined with 
   Thermal Storage Systems and with night-breeze ACC ---
   
 they all share one problem (low temperature difference)
 and one advantage (low energy consmption and operation cost and low noise)
 
  
 This concept combines coil in the attic with whole House Fan
  http://www.fsec.ucf.edu/bldg/pubs/pf273/
 http://www.homes-across-america.org/
 
  The thermal storage can compensate for 'low cooling capacity' at
time of peak demand.
 Here is some info on that:

Thermal storage systems are intended to meet part or all of the cooling needs of a 
building during specified periods of peak demand. It is essential they have suffi-
cient capacity to provide the cooling during these periods. Figure 8-1
presents the
schematic diagram of a thermal storage system. During off-peak hours, part of the 
cooling energy produced by the chillers is used for charging the storage systems 
that generally store cold water or ice. During peak hours, buildings
receive cooling
energy from the tank and/or chillers. 
Figure 8-1. Thermal Storage System in Charging Mode and in Discharge Mode
 
 
Caution : very long URL's get broken in the browser: the whole string
in [] needs to be pasted into 'location box' but without the []
[
http://216.239.59.104/search?q=cache:Tz6XOfg0UDUJ:www.eere.energy.gov/femp/pdfs/ccg10_ch8.pdf+fan-coil+,+small+difference+,+50F&hl=en&lr=lang_en&ie=UTF-8
]

 Links to products and studies on RFCs
 =========================================

  Key issue would be to find a fan-coil unit which can deliver reqiured BTU/hour
  operationg with 'small temoerature difference' I searched for such units,
  products and academic studies using these:

Search Term : water to air heat exchange

             : water to air heat exchange

             : comparison of  fan-coil, "small temperature difference"
 
             :fan-coil, " temperature difference", cooling
  
and found a directory for selection and comparison of HPs and RFcs


http://www.energyideas.org/topics/default.cfm?o=h,t,ts&c=z,z,14

which leads (as an example) to info on RFC (room fan coils)
http://www.ariprimenet.org/ari-prog/direct.nsf/webpages/Product+Types?OpenDocument

for example
Total Capacity (Btuh): 12800
temperature Rise (deg F): 10
power Input PSC (Watts) : 60
http://www.ariprimenet.org/ari-prog/direct.nsf/fraRFC?OpenFrameSet

which can be compared with HP (heat pumps)
Product Performance Ratings
Cooling Capacity (Btuh): 23000
SEER Rating (Cooling): 10.00 


Rough rule is 
 cost   500--1000  $/ton  outside loop

 cost   water to air pumps  $800/ton

 
   UNITs, examples, rating systems 
     ============================ 
 Ton:
 The term "ton" was originally based on the amount of ice it would
take to achieve a desired level of cooling. Now it is more typically
used as a measure for an air conditioning system's capacity. One ton
is equivalent to 12,000 BTUs per hour of cooling. Residential air
conditioners usually range from one to five tons.
 

 



What we did this year at the Manchester project was to create
temporary heat by using new high-efficiency, oil-fired heating boiler,
and throughout the building we placed air handlers. These
file-cabinet-sized units have a hot-water heating coil and a blower
fan inside them. When air is blown across the hot-water coil (much
like in an automobile radiator), air is heated.
http://www.thisoldhouse.com/toh/knowhow/heatingcooling/article/0,16417,216711,00.html



 example of what we can get at T=50 F
Housed in a very compact 14.96" W x 47.24" H x 8.07" D enclosure, the
WW3500S heat exchanger is designed for operation in extremely polluted
and high temperature environments. Its unique design employs a high
capacity fan that produces 259 cfm of air flow. This, coupled with a
cooling water flow of 1.76 gpm/ 400 l/h at a temperature of 50° F /
10° C produces 3500 watts of cooling capacity when the temperature
difference between water inlet and ambient is 25° K.
 http://www.industrialnewsroom.com/fullstory/18882

 

 
 
  Air Flow Volume:
 The amount of air that a cooling system circulates through your home,
expressed in cubic feet per minute (CFM). A typical system requires
400 CFM per ton of cooling.
http://www.home.directenergy.com/acbg/acbg_B2.asp

 Ton:
 The term "ton" was originally based on the amount of ice it would
take to achieve a desired level of cooling. Now it is more typically
used as a measure for an air conditioning system's capacity. One ton
is equivalent to 12,000 BTUs per hour of cooling. Residential air
conditioners usually range from one to five tons.
 
 
 
 range of RFC units available

http://www.climate-eu.invensys.com/uk_pdf/brochures/FanCoilSolutionsBrochure.pdf
http://123fargo.com/get/comfort/page2.asp

comparison
http://216.239.59.104/search?q=cache:X7ElMEHEeEQJ:www.greenheck.com/pdf/fans/LFCMarch2004.pdf+performance+of+fan-coil&hl=en&lr=lang_en&ie=UTF-8

http://123fargo.com/get/comfort/page2.asp


 
Fan Coil Units, efficiency
 http://www.energybooks.com/toc/toc0503.htm
 
 rating systems
. The major difference in the newer ISO rating is that the pumping
penalties (used in the older ARI ratings) along with penalties for fan
power (external to the unit) have been removed. This has had the
result of raising the performance values compared to the older ARI
system. Where an average unit in the old rating system may have had a
13.0 EER in cooling, under the ISO rating this same unit might show a
14.0 or 14.5 rating.
http://www.geothermie.de/egec-geothernet/an_information_survival_kit_fo.htm

 
 example 
 
Fan Coil Units: Fan coil systems use terminal cabinets in each room
serviced by 2, 3, or 4 pipes approximately 11/2" each in diameter. A
fan blows air over the coils which are serviced by hot or chilled
water. Each fan coil cabinet can be individually controlled. Four-pipe
fan coils can provide both heating and cooling all year long. Most
piping is steel. Non-cabinet units may be concealed in closets or
custom cabinetry, such as benches, can be built.
http://www.oldhouseweb.com/oldhouse/content/npsbriefs/heatingcooling/4.asp


Laboratory measurements/formulae
=================================

Performance of fan-coil units

... Experiments were conducted to measure the heat and mass transfer
performance for various air velocities and water flow rates

http://resourcecenter.ashrae.org/store/ashrae/newstore.cgi?itemid=6713&view=item&categoryid=335&categoryparent=335&page=1&loginid=972563


study of performance - formula for cooling capacity

http://www.hku.hk/bse/mech3005/mech3005_lab0203_fancoil.pdf

 Tools/computer models/ research groups 
 http://gundog.lbl.gov/
 Welcome to the home of the Simulation Research Group at Lawrence
Berkeley National Laboratory (LBNL) in Berkeley, California. We
specialize in creating building energy simulation software
 http://www.eere.energy.gov/consumerinfo/factsheets/ad6.html
 http://www.eere.energy.gov/consumerinfo/tools_ghp.html
  http://www.arit.com/research/slabcold.htmlhttp://www.cbe.berkeley.edu/RESEARCH/pdf_files/SR_fanpower2000.pdf
  
  [DOC] Book 3: Energy Efficiency in Electrical Utilities
File Format: Microsoft Word 2000 - View as HTML
 ... side across air handling unit (AHU) / Fan Coil Unit (FCU ... wrt
power consumption) for
 350 TR cooling load ... full load with 4.5 °C temperature difference
across the ...
www.energymanagertraining.com/revised_qustion_bank/Paper3/3.4%20HVAC%20-%20revised%20(table%20format).doc

 
 coil-fan units: perfomance tables
 http://www.kimukoh.co.jp/english/seihin/delta.html
 
  If, after looking at some of the above links, you would want to proceed,
   then asking for services of  competent HVAC professonal in the area may
   be a good nest step. There are tables and computer programs, which take
   into the account the thermal loads and requrements and produce the build
   and operating cost of differetn systems.
 
 Hedgie

To keep the coolent circulating pump electric consumption low you need
large diameter pipe, at least 4 inch = 10 centimeters, so the pipe is
a sizable inital cost. Unless your well has large diameter, a low back
pressure heat exchanger won't fit in the well. If you pump a million
gallons per day though radiators in your house, you can likely achieve
75 degrees inside even when the outside temperature is 110 degrees f.
The coolant water will warm from 55 derees f to perhaps 70 degrees f.
You can put the 70 degrees f water in another well perhaps 100 feet
from the sourse well. This is likely ilegal as you will be
contaminating the water table at least slightly. Unless you return the
water, you will likely pump your well dry in a few weeks if not sooner
at a million gallons per day. By October the intake well may have
warmed to 75 degrees, due to putting heat into the water table, but
October is the end of the cooling season and the 55 degrees should
recover by May when you want to start cooling again. A small well
insulated house may only reqire 100,000 gallons of coolent per day.
Yes, I think it will work and use perhaps 1/10th as much electricity
as a heat pump. I think you can see 100 of your nearby neighbors
cannot put lots of heat in the water table or the water table will be
warmed to 75 degrees by June instead of October. The other
disadvanages is a broken pipe inside your house will cause major water
damage because of the large volume of water needed.   Neil

If you are looking for a way to size the system, Manual J by acca is
the best and only sure way to do it.
For a quick method try this,
:sci.engr.heat-vent-ac sci.engr.heat-vent-ac] newsgroup

http://www.northernhvac.com/newcalc.htm Free online HVAC heat load calculator