[Bldg-sim] Space Cooling Energy Consumption with GSHP

[Karen Walkerman]

The efficiency of any water source heat pump is dictated by the temperature
of the water loop.  Create an hourly report output showing geothermal loop
temperatures.  You can then check this against the heat pump chart to
determine if your heat pumps are operating efficiently.  Depending on the
ground temperature, a geothermal system can start to heat up, lowering the
efficiency of attached equipment.  However, I would still be surprised to
learn that an air source heat pump still performed better.

Also, in order to make variable volume pumping work properly, you must
specify Isolation valves on the heat pumps.  This allows water to bypass any
heat pumps that are not calling for water flow.  This lowers the pressure in
the system.

--
Karen

On Wed, May 14, 2008 at 9:05 AM, Demba Ndiaye <demba.ndiaye at setty.com>
wrote:

>  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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