X-Message-Number: 2211
Date: Fri, 7 May 93 11:07:00 CDT
From: Brian Wowk <>
Subject: CRYONICS Smaller Coldroom
By popular demand, here are some thoughts on a smaller coldroom.
Unfortunately nature is not kind to builders of small coldrooms. The
100 patient (1000 neuropatient) coldroom we have been discussing would have
an interior volume of 75 cubic meters. Suppose we built a coldroom with
1/10th the volume, say 2 meters on each side giving 8 cubic meters interior
volume. This might be enough for 10 whole body patients (100 neuros). Well,
if you made the foam walls 0.5 meters thick, the heat flow into the room
would be 250 watts! This is half as much as the 100 patient room, with an
associated operating cost half as great.
What if you increase the foam thickness to 1 meter? Well,
you don't gain much at all. As Robert Ettinger and Mike Darwin have
pointed out, big foam thicknesses don't do much for small rooms.
Your heat flow would still be 150 watts. Also your foam cost would
be $15,000 (30% that of the 100 patient room), and your floor space
utilization would be half that of the "big" coldroom.
Actually, the best place to build a small coldroom is inside
a Bigfoot dewar. The heatflow into -130'C inside would be only 20
watts. This could easily be pumped out by an air-cooled P-100
cryocooler for $100 a year worth of electricity. This electricity
cost is so small, I wouldn't even budget for it. Other costs break
down as follows:
Dewar 18,000
2 P-100 cryocoolers 8,000
Misc. Hardware 10,000
--------
$36,000
This prototype system would implement and test all of the important
coldroom concepts we have discussed so far (except foam insulation),
including:
* mechanical refrigeration
* over/under air circulation
* LN2 backup
* propanol/water ballast
* defrost function
We could also test the suitability of different ballast containers
and construction materials (wood, plastic, metal) in the -130'C
environment.
This room would be for neuropatients only (about 25). This
is OK to start with since neuropatients would benefit the most from
-130'C storage anyway. Storage costs consist of capital
ammortization entirely, and are about $100 per patient per year for a
15 year amortization. This is 30% cheaper than our current neuro
storage system, although unlike the real coldroom it is not vault-
protected.
Unfortunately dewars are fragile and prone to vacuum failure.
For this reason the dewar "coldroom" will have to be built in such a
way that it can be quickly disassembled (or just lifted out as a
unit) and moved into another Bigfoot if necessary. Also for this
reason I do not envision the dewar coldroom as a permanent structure.
Once the concept has proven itself, construction on a real coldroom
should begin ASAP. We will need the space sooner than many people
think, and the dewar coldroom patients can then be moved and enjoy a
further seven-fold reduction in storage costs.
To summarize: I think the dewar coldroom is a good idea, and
I thank Michael Riskin and Thomas Donaldson for pushing in this
direction. The cost is modest, and the most expensive capital item
(the dewar) will be available for backup for LN2 patients when the
project is finished. I will be happy to design the system. In the
meantime it is imperative that Alcor seriously plan for a large
coldroom. This will involve setting aside 500 square feet in the new
facility, and ensuring that adequate overhead space exists. I would
like to see the dewar system up and running within one year, and real
coldroom construction start within three years.
Finally, if Alcor doesn't do this, *somebody else will*.
--- Brian Wowk
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