[Bldg-sim] Geothermal vs WSHP and cooling tower energy use

[Karen Walkerman]

In the past week I have been comparing a GSHP to a WLHP system with a
cooling tower system and it seems to me that eQuest is underestimating
cooling tower energy use, particularly fan energy use.  Are there any
resources that explain how eQuest calculates cooling tower energy use, or
has anyone done tests to confirm cooling tower energy use?

I am concerned that the cooling tower allows the fan to operate at below
0.01% of it's design airlfow in a given hour, this means that when there are
low cooling loads, the fan is allowed to short-cycle--a condition not
allowed in the real world.

Thanks,

--
Karen

On Wed, May 14, 2008 at 9:57 AM, Adam Young <way at freese.com> wrote:

>  Good morning,
>
>
>
> I am having similar results with a ground-coupled heat pump and am
> following this thread closely. I am only realizing savings of about 5% to
> 10% over an air-source HP.
>
>
>
> I believe I am incorrectly separating out the fan-energy on the air-source
> units. What is the procedure for getting the fan and compressor energy
> separate on the air-source units (12 SEER air-source unit per 90.1-2004,
> baseline design)? If I understand correctly, the GCHP efficiency stated
> under ARI 13256 does not include external fan energy or external pump
> energy, and therefore, the stated GCHP efficiency can be converted into EIR
> directly. Correct?
>
>
>
> Also, for the GCHP the correct number to use is the "GLHP EER" value from
> the manufacturer based on ARI 13256, which is higher than the water-loop HP
> (WLHP) ARI EER? Is that correct?
>
>
>
> Experience tells me a GCHP should realize more savings than what I am
> getting, which leads me to believe I am inputting "garbage" into the model.
> Thanks for your help!
>
>
>
> *Adam Young*
>
>
>  ------------------------------
>
> *From:* bldg-sim-bounces at lists.onebuilding.org [mailto:
> bldg-sim-bounces at lists.onebuilding.org] *On Behalf Of *Demba Ndiaye
> *Sent:* Wednesday, May 14, 2008 8:05 AM
> *To:* Tom Butler; bldg-sim at lists.onebuilding.org
> *Subject:* Re: [Bldg-sim] Space Cooling Energy Consumption with GSHP
>
>
>
> Thomas,
>
>
>
> You should definitively have more savings than that, even if there is the
> pump energy.
>
> One first thing to check: the efficiency of GSHP should be much higher than
> that of air-source heat pumps in both heating and cooling modes.
>
>
>
> ______________
>
> Demba Ndiaye
>   ------------------------------
>
> *From:* bldg-sim-bounces at lists.onebuilding.org [mailto:
> bldg-sim-bounces at lists.onebuilding.org] *On Behalf Of *Tom Butler
> *Sent:* Tuesday, May 13, 2008 5:53 PM
> *To:* bldg-sim at lists.onebuilding.org
> *Subject:* [Bldg-sim] Space Cooling Energy Consumption with GSHP
>
>
>
> I am modeling an apartment style dormitory for a project in Atlanta, GA.
> Each of the 45 units is served by its own heat pump, along with a few zones
> for public areas. For an energy efficiency grant application I have compared
> the designed system, a ground source heat pump, with an air source heat pump
> prescribed by 90.1. Other than the systems, the models are identical.
>
> The energy use for space cooling is significantly higher for the GSHP
> system (24,000 kWh vs. 17,000 kWh). Because the power required to run pumps
> offsets the savings in heating energy, this destroys the rationale for
> spending the extra money on the Ground Source Heat Pump, as well as our
> chances of receiving the grant.
>
> Has any one encountered this issue?
>
>
>
> Thanks
>
> tb
>
> *Thomas Butler,* LEED AP* *
> Direct Phone 404-253-1435 | Direct Fax 404-253-1335
>
> *L**ORD**, A**ECK** & S**ARGENT** A**RCHITECTURE
> *Responsive Design · Technological Expertise · Exceptional Service
> www.lordaecksargent.com
>
>
>
>
>
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-- 
Karen Walkerman
Second Law Consulting
802-238-0980
kwalkerman at gmail.com
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