At 09:21 AM 6/2/00 -0400, Vandergraaf, Chuck wrote:
>[Quoting Greenpeace]
>
>Greenfreeze Technology
>Greenfreeze uses a mixture of propane (R290) and isobutane (R60Oa), or
>isobutane as a pure gas for the refrigerant. This replaces the
>ozone-destroying chemicals currently used in refrigeration systems
>worldwide. The filling quantities are about two thirds less than what is
>required with HFC-134a and CFC-12, due to the technical and thermodynamic
>properties of hydrocarbons.
>Propane and butane are natural gases available without licenses all over the
>world at prices (in a purified form) comparable to those of CFCs. The energy
>efficiency of the propane/butane refrigerators has been proved to be as good
>as those cooled with CFCs or HFC-134a.
>Some "Greenfreeze" refrigerators with isobutane use up to 38 percent less
>energy than their identical counterparts with HFC-134a. Bosch-Siemens
>announced a 50% energy savings with Greenfreeze in their 1993 annual report.
Some of my colleagues here work on properties of alternative refrigerants,
so I can add a few things here.
1) It has been known for a long time that isobutane (and its mixtures with
propane) can be a pretty good refrigerant. It would be more widely used if
not for concerns about safety and liability. I've been told that isobutane
would be great for auto air conditioners, but the automakers don't want
(probably with good reason) volatile and flammable hydrocarbons under the
hood in case of a crash. The story is similar with ammonia which is a fine
refrigerant but unpleasant if it leaks. Maybe Greenpeace should be
supporting tort reform so that people can make greener refrigerators
without fearing big lawsuits. I think these other refrigerants are more
widely used in Europe, not because of green concerns but because of the
legal climate.
2) I don't believe the statement about needing 2/3 less refrigerant. The
amount of cooling you get in a vapor-compression refrigeration cycle is
determined to a first approximation by the latent heat of the
refrigerant. Isobutane and R134a have almost identical molar latent heats
at their normal boiling points. Maybe they are trying to talk about the
*mass* of refrigerant, since the HFCs have higher molecular weight. But
that isn't really what matters. Similarly, statements about 38% or 50%
better efficiency seem unlikely. Each refrigerant has a particular
temperature range to which it is best suited; if there is some temperature
where isobutane is 38% better there may be some other temperature where it
is 38% worse.
3) They talk about "ozone-destroying chemicals" and then talk about R134a
and R12. R12 deserves that label, but R134a has zero ozone depletion
potential. It is a global warming gas, but that doesn't happen unless it
leaks from the refrigeration system. Of course most refrigerants do
eventually get to the atmosphere when the appliance or auto is junked, but
that amount is tiny compared to the global warming potential of all the CO2
from fossil fuels.
4) If the real concern is global warming, the global warming potential of
the refrigerant itself is pretty irrelevant. The important factor is the
efficiency of the refrigeration, which determines how much fossil fuels
have to be burned to generate the electricity to run the appliance. If
there are applications where isobutane refrigerators are really more
efficient, then that is good in terms of global warming, but that has
little to do with the global warming potential of isobutane itself.
5) To tie something to the concerns of the ASA list. God calls us to be
good stewards of the creation. Some stewardship decisions are easy (not
wasting energy, not littering, considering fuel efficiency when buying a
car), but then there are cases like this that are not obvious. As Joel
mentioned and I would agree, simply taking the word of Greenpeace (or even
of less loopy groups such as the Sierra Club) as to what is good
stewardship is not necessarily wise. Maybe if we Christians spent less
time arguing about the means of creation, we could be better equipped to be
good stewards of creation. I know there is some work along that line
(there is an Evangelical Environmental Network, and Cal DeWitt has written
some books), but I at least have not paid as much attention to that area as
I probably should.
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| Dr. Allan H. Harvey | aharvey@boulder.nist.gov |
| Physical and Chemical Properties Division | "Don't blame the |
| National Institute of Standards & Technology | government for what I |
| 325 Broadway, Boulder, CO 80303 | say, or vice versa." |
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