[Greenbuilding] [BULK] Re: rock storage + heat pump

[Lawrence Lile]

Yes you WILL have mold if you use boxes of rocks as a heat storage medium for airflow. In Portland, the mold may climb out on it's own legs, Portland being rainy, wet Portland.   Remember how dirty your furnace air filter gets?  That's how dirty those rocks will get.  Many installations were tried like this in the 70's, many of them have been disabled by now due to 30 year's accumulation of Eeyeeecch in the rocks.  Never design a space for environmental air that cannot be cleaned, if at all possible.

--Lawrence Lile

> -----Original Message-----
> From: greenbuilding-bounces at listserv.repp.org [mailto:greenbuilding-
> bounces at listserv.repp.org] On Behalf Of Brian Hyslop
> Sent: Wednesday, May 21, 2008 1:54 PM
> To: greenbuilding at listserv.repp.org
> Subject: [BULK] Re: [Greenbuilding] rock storage + heat pump
> Importance: Low
>
> Hi Nick,
> Could you elaborate on how your water source heat pump works. Does it
> have a compressor like a Ground source heat pump?  I have a client in
> Portland Oregon who wants to dig a basement and blow hot air from the
> sun-space over large rocks to develop a  mass with about a 3 month lag
> time.  I'm worried about mold as Portland is very wet, I can't image
> keeping the RH below 60% with out conditioning the space.  I would like
> to use water as the storage medium instead but don't really know how
> much I need or the best way to get thermal transfer.
> Thanks,
> Brian Hyslop
>
>
> Elemental Building Design LLC
> 1042 W. 18th Pl
> Eugene OR
> 97402
>
>
> 541-484-1220
> brian_hyslop at yahoo.com
> OR CCB#165372
>
>
>
> ----- Original Message ----
> From: Nick Pine <nick at early.com>
> To: greenbuilding at listserv.repp.org
> Sent: Wednesday, May 21, 2008 5:07:54 AM
> Subject: [Greenbuilding]  rock storage + heat pump
>
> Greg Milne <l-shea at sbcglobal.net> writes:
>
> > We are building in Northwestern Illinois.  We want to combine a 4-6
> ft
> > deep rock storage system with a heat pump.
>
> Moline looks pretty cold, 25.4 F in January, with 6474 HDD. The deep
> ground temp is 49.6.
>
> >  If we pull air directly from the rock storage with no separate duct
> > system running through the rock, do we need to worry about air
> quality
> > (moisture/ mold)?
>
> I'd say no, if you keep the RH in the rocks below 60%.
>
> >  Is 4-6 ft deep enough to take advantage of geothermic heat in a rock
> > storage system?
>
> It's hard to get much earth heat into rocks without lots of surface
> touching the soil. It's easier to get heat and coolth from outdoor air
> into rocks.
>
> >  If we use a heat pump, can this system both heat and cool the house?
>
> It might, with lots of rocks.
>
> >... does the rock have enough thermal mass to act as the active solar
> >collector?
>
> How would the sun heat the rocks? Low-mass solar collectors work
> best...
>
> >We are not building a hot room/ greenhouse.
>
> I wonder why not.
>
> >  Has anyone tried this combination?
>
> I'm simulating something like that, with 1000' of 4' diameter concrete
> earth tubes that will be used for cooling and dehumidification, and a
> water source heat pump for heating, with 2 50K gallon water tanks as
> its
> heat source. The tubes will be cooled with outdoor air by a passive
> thermal chimney during the heating season, and they have a 3 month lag
> time, compared to the outdoor temp. Another option would be to use the
> same tubes for heating and cooling, trying to make them cold near the
> end of the heating season and warm near the end of the cooling season.
> The daily average temp in July is 75.2 F in Moline, with a a 64.5 F
> average daily min, so you might not need much AC.
>
> Nick
>
>
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