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DENSO NEWS CONFERENCE REMARKS
DENSO NEWS CONFERENCE REMARKS
2002 SAE World Congress, March 4, 2002
Looking Toward the Future CO
2
Refrigerant
RICHARD SMITH
Director, Climate Control Engineering
DENSO International America, Inc.
We, at DENSO, are extremely proud of our status as the automotive worlds global leader in air
conditioning systems. As Mr. Fukaya noted in his remarks, we take even more pride in the fact
that we have achieved that status while honoring a serious, steadfast, superceding commitment to
the environment.
This, as you know, is not always, if ever, a simple balancing act the progression of automotive
engineering and the safety of the environment. The balance becomes even more delicate, more
sensitive, when you add the weight of corporate fiscal responsibility. Again, we, at DENSO,
stand proudly on our record. We have shown, and continue to show, we believe, an ability to
regard all three engineering, the environment and fiscal responsibility -- with the same concern
and care.
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In direct regard to automotive climate control systems, which is todays subject, DENSO is quite
efficiently and energetically pursuing the goal of developing an automotive climate control
system that meets or exceeds current engineering standards and demands, those being:
One: Smaller and more powerful, R. Smith DENSO News Conference Remarks
2
Two: Easily adaptable, and
Three: Above all else, of course, environmentally better.
In regard to the current generation of vehicles, those with conventional internal combustion
engines, DENSO continues its mission of reducing the environmental impact of the R-134a-based
air-conditioning system by specifically targeting improvements in efficiency and weight, which,
in turn, reduce power consumption and, ultimately, decrease environmental impact.
Society, or course, demands, and rightly so, continued progress toward development of systems
that are completely benign to the environment. We are leading that march, too.
Thus, for the near-term, next generation of hybrid and idle-stop vehicles, DENSO has developed
electrically powered A/C systems and alternative means of cabin heating. It wasnt so long ago
that the automotive industry discovered that R-12-based air-conditioning systems posed two
serious threats to the environment:
One: Ozone depletion.
And, two: Global warming.
DENSO, as you may recall, was at the forefront of the global conversion from R-12, an ozone-
depleting refrigerant, to R-134a, an ozone-safe refrigerant. We received an EPA award in 1993
citing our work. We took great pride in seeing one of our customers Toyota become the first
automaker to convert its fleet to R-134a, also in 1994.
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We still are hard at work, trying to improve the current R-134a system through development of
more efficient heat exchangers -- DENSO currently manufactures the smallest, lightest, most
efficient heat exchangers in use and by reducing refrigerant leakage through developing better
system hoses and fittings.
But we knew, too, even then and even now, while working to better the R-134a system -- that
the conversion to R-134a would, ultimately, lead only to short-term success. We knew that we
needed to look even further into the future:
Toward a generation of new vehicles and their new demands.
Toward a new generation of systems.
Toward an air-conditioning system run on CO
2
.
Why CO
2
? Two reasons, mainly.
One: CO
2
is a refrigerant that exists in nature and has a negligible effect on the environment. R. Smith DENSO News Conference Remarks
3
Two: CO
2
also is a good working fluid not only for cooling systems, but also for heat-pump
systems. That potential tied perfectly into the next generation of vehicles, those with electric
or hybrid engines, which cannot draw cabin heat from an internal combustion engine.
While the conversion to R-134a was a significant step, basically one refrigerant was replaced by
another, albeit a much safer one, using fundamentally the same system components. But if that
was a step, converting to a CO
2
system could well prove to be one of those, quote-unquote, giant
leaps.
As previously noted. CO
2
or carbon dioxide -- is a refrigerant that exists in nature. It is not toxic
and does not damage the ozone. In effect, its potential for harm is negligible. Indeed, its Global
Warming Potential, or GWP, is less than one-one thousandth than that of R-134a.
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In addition to the GWP benefit of CO
2
, the air-conditioning cycle with CO
2
displays a promising
benefit in total global warming impact compared to current R-134a systems. The Total
Equivalent Warming Index, or TEWI, is a measure of overall system operation impact. We
believe that we can achieve about a 35 percent global warming impact benefit by 2005.
After the conversion to R-134a, industry researchers began seeking the next generation
refrigerant. And DENSO has been at the forefront of the effort.
It is important to note that SAE, too, has been actively involved in this effort, specifically by
sponsoring summer ride-and-drive symposiums in Phoenix in which DENSO has participated --
as well as by sponsoring an Alternative Refrigerants Cooperative Research Effort. DENSO has
supported that initiative both with funding and with our advanced components
Researchers examined numerous alternative refrigerant possibilities. Propane, for example, was
one. Most possibilities were discarded. CO
2
emerged as the favored candidate. Today, we are at
the point where we can say that development of a CO
2
system is ready for the next step: actual
vehicle applications.
This adaptive use of CO
2
, it should be noted, is not entirely new. In May 2001, DENSO began
manufacturing CO
2
-driven applications for Japanese domestic hot-water heating utilizing a heat-
pump system.
It is interesting to note, that in those applications, the CO
2
-driven water-heating system used one-
third the amount of power required by a conventional natural gas heater system. R. Smith DENSO News Conference Remarks
4
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Heres how this all works:
The diagram behind me describes the CO
2
refrigeration cycle. You will note that it employs
basically the same cycle as the R-134a adaptation. This is known as a vapor compression cycle.
The system works basically like this: A gas cooler, which corresponds to a conventional
condenser, cools CO
2
refrigerant discharged from the compressor, and, in this application, heats
the water supply. Next, the thermal expansion valve, or TXV, condenses a part of the CO
2
refrigerant as a result of adiabatic expansion.
The refrigerant completes the cycle by absorbing heat from the ambient air and returning to the
compressor, ready to transfer the heat to the water.
Once, again, as noted previously, the hot-water system use of CO
2
has shown significant benefits
a 30 percent reduction in power consumption and a 50 percent reduction in emissions. One
reason the CO
2
system is so attractive in Japan is that natural gas in Japan is 10 times as
expensive as it is here. The bottom line? This product offers Japanese residential consumers a
five-year payback. And, because CO
2
is benign to the atmosphere, the product also offers
significant and obvious environmental benefits
Now for the automotive applications.
This slide depicts the basic system components. Again, the basic cycle is the same as current R-
134a cycle -- a vapor compression cycle, with two fundamental differences.
First, because the operating pressure of a CO
2
system is 10 times higher than that of the R-134a
system, the system requires significantly different construction different heat exchanger
construction, different materials for hoses and gaskets. Every component needs to be re-
engineered.
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Second, the automotive application requires an internal heat exchanger to obtain the efficiency
targets previously mentioned. The highly positive side is that the effects on global warming are
greatly reduced and that is, indeed, the bulls eye on the target. In application, the CO
2
system R. Smith DENSO News Conference Remarks
5
fundamentally met or bettered the R-134a system for cooling capacity. It still, however, lags the
best R-134a system in power consumption or drag on the engine, as previously shown in the
TEWI chart, be it an internal combustion engine or an electric or hybrid motor.
Our goal at DENSO is to make the CO
2
system as efficient as our future ``top level target for
the R-134a system. The CO
2
system requires additional development before mass application, but
it is ready for specialized use. For example, DENSO has developed a CO
2
air-conditioning and
heat-pump system jointly with Toyota for its fuel cell hybrid vehicle the Toyota FCHV-4, which
employs a hermetically sealed electric compressor, resulting in good sealing performance, a
simple structure and easy installation.
The CO
2
system is perfect for an electric vehicle