Re: Heating systems
From: Daryl Anderson (danderigc.apc.org)
Date: Thu, 13 Oct 94 20:16 CDT
Stephen,
   I cannot speak from experience with installed heat-pump system(s) but
we at the EcoVillage at ithaca are currently evaluating them (specifically
"ground-source heat pumps") as an alternative to our "baseline" design of
high-efficiency gas supplementing passive-solar and energy-tight homes.
    We anticipate some efficiencies due to our neighborhood design which
will build the initial 30 houses in 4 clusters of 8 and 6 houses with
"energy centers" serving each cluster. This allows us to remove combustion
(e.g. gas) units from the houses but also allows the heat-pumps to be sized
to serve, e.g., 6 or 8 homes. Since our anticipated heating load for each
house is a tiny fraction of a "typical" home this allows us to at least size
for a normal heat-pump. It also allows a good deal of upfront savings in
the system since we will not be putting in 30 systems, merely 5 (one for
the common house)... IF we decide to go with them, that is.
   Current decision issues revolve around both upfront cost and operating
cost as well as environmental impact (vs. gas) and heating modes. To
summarize the issues :
   (1) upfront cost is indeed higher, some utilities will fold it in to
downstream billings or otherwise flatten it out for you - we hope that the
broad visibility of the ongoing EcoVillage project might pry some
concessions from either the local utility or a specific manufacturer...
   (2) a very rough analysis by a member of our Energy Committee suggests
that the heating-only GSHP technology may also be more expensive on an
annual basis. Assuming a range between 300 and 400% efficiency (what they
call their "COP" or "Coefficient of Performance") we still find that the
electrical cost of operating the systems run from 10-50% over the basic
gas system. This assumes our quite high electric here in Ithaca of $0.11
per kwh and natural gas is considered artificially-llow in price by
many. Nevertheless we wonder. The primary cost advantages of the GSHP is
if you allow it to bring in it's substantial efficiencies in delivering
air-conditioning... this is something that we have never done in any of
our programming for EcoVillage. AC (at least in the snowy hinterlands) seems
a marginal need and an eco-downer. You might consider otherwise tho.
   (3) Environmental impact is interesting. Our rough analysis suggests that
we may "generate" about 1/2 ton LESS CO2 per household per year if we go
the GSHP instead of high-eff natural gas (HENG ?!). Many assumptions are
rold in there including New York's specific mix of electric generation 
capacity (and not ignoring that our 20% nuke base allows a pretense of
"clean" from less CO2). We will certainly be discussing this cost-pollution
tradeoff as we consider options. (Baseline heating per house is only
expected to run $150-200 per year so the overage for GSHP might be 
acceptable).
    (4) Other issues are (a) most of the older GSHP technology seems to
use forced-air to distribute heat. Our group nixed that in programming and
hopes to find a way to work our "hydronic" system (e.g hot water) in a
radiant floor heating design. (b) For the time being the homes will need
traditional hot-water (although we are designing for transfer to solar or
solar-assisted we need to get conservative banks to approve, ahem... buy,
our homes). We would really like to find a heat-pump mfg that can include
full DHW (domestic hot water) in the package. Many can support DHW but I
am told that only a newer technology called "de-super-heater" or something
like that (!) can manage the higher temps and consistent supply that full
DHW requires. If we can thence unhook entirely from the gas line we can
also save a possible $32,000 "hookup" charge.
    I believe one of the COHO projects in Mass (Pine St or Pioneer Valley)
is using heat pumps and you might also chase down an intentional community
called Raven Rocks in Ohio that sex they are putting one in.
    Good luck. Keep in touch with any other info you get.
    -Daryl Anderson, EcoVillage at Ithaca 
    ps. We hope to be moving in by late '95 with 20 households currently
        committed and designs for 30 houses.

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