[GSBN] ground source heat pumps

[Derek Roff]

“A ground-source heat pump can only be considered acceptable as an 
alternative to conventional heating systems from an environmental point 
of view if it has a coefficient of performance of over 4, gets its 
electricity from a CO2 free source and uses a climate-friendly 
refrigerant."

I think there is a big risk in any analysis that compares an actual 
engineered and available option to an ethereal, undelineated, "perfect" 
alternative.  For anyone trying to decide on a heating/cooling unit, 
there are few CO2-free choices.  Dismissing heat pumps at that stage in 
the design process would frequently lead to choosing an alternative 
which released more CO2.

Far better, as others have mentioned, to intervene earlier in the 
design process.  To build a better envelope, with better solar systems 
and orientation, so that the need for a heating/cooling unit is reduced 
or eliminated.  In any case, a heat pump should be compared to the real 
alternatives, and a choice made by looking at the actual numbers 
involved.  Heat pumps will be more appropriate in some situations than 
in others.  Relatively few, perhaps, but then almost all of building is 
site specific.

While powering a heat pump for renewable sources is possible, it is 
often impractical to do so on the residential scale.  Heat pumps draw a 
fairly large amount of current, and the greatest heating load is at 
night and in the early morning, when both solar and winds sources are 
lower.  On the other hand, the largest cooling needs are in the 
afternoon, when solar energy is close to maximum.

Derelict

Derek Roff
Language Learning Center
Ortega Hall 129, MSC03-2100
University of New Mexico
Albuquerque, NM 87131-0001
505/277-7368, fax 505/277-3885
Internet: derek at unm.edu


--On Wednesday, March 18, 2009 5:36 PM +0000 Tom Woolley 
<tom.woolley at btconnect.com> wrote:

>
> Dear Catherine
>
>
> Ireland is the geothermal capital of Europe. It has become a middle
> class status symbol .
>  
> Richard Douthwaite , a highly respected green economist wrote
> (extract from a much longer piece)
>
>
> "I began to ask myself that question when I came across a document on
> the website of a small German electricity company which concluded: “A
> ground-source heat pump can only be considered acceptable as an
> alternative to conventional heating systems from an environmental
> point of view if it has a coefficient of performance of over 4, gets
> its electricity from a CO2 free source and uses a climate-friendly
> refrigerant. As most current heat pumps do not meet these criteria,
> we advise against their use.” ‘
> Richard Douthwaite , Construct Ireland Issue 19
>
>
> http://www.constructireland.ie/
> richard at douthwaite.net
>
>
> best wishes
>
>
> Tom Woolley
>
>
>
>
>
>
> On 18 Mar 2009, at 17:16, BuildersWithoutBorders wrote:
>
>
> Dear colleagues -
>
>
> Can someone shed some light on so-called geothermal heating systems,
> and their cost-effectiveness for a typical home?
>
>
> I imagine the pay-back in energy saved has something to do with how
> many heating degree days in a specific climate.  But then, I
> understand they can also be reversed for cooling.
>
>
> This seems like an expensive technology that is dependent on
> electrical service... can it be powered by solar/
>
>
> Thanks for any insight offered.
>
>
>
>
> Sincerely,
> Catherine Wanek
> Co-director
> Builders Without Borders
> <mail at builderswithoutborders.org>
> www.builderswithoutborders.org
> 575-895-5400 
> _______________________________________________
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>
>
>
>
> Tom Woolley
>
>
> Rachel Bevan Architects
> 17A Main Street
> Saintfield
> Ballynahinch
> BT24 7AA
>
>
> tom.woolley at btconnect.com
> 028 44 830988