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DuPont Refrigerants Unveils First DP-1 Refrigerant Test Car in Germany

29 November 2006

DuPont Refrigerants recently unveiled the first demonstration of its new, low global warming potential (GWP) refrigerant, DP-1, as part of its presentation at the recent European Automotive Air Conditioning (EAAC) Show in Frankfurt, Germany.

No changes were made to the demonstration vehicle’s existing MAC (Mobile Air Conditioning) system in order for DP-1 to run. Because it is compatible with existing technology, DP-1 has the potential to enable a cost-effective global transition to low GWP refrigerants across the entire global MAC industry, according to DuPont.

The auto industry is being pushed to adopt new solutions for mobile air conditioning. The EU has published the final regulation on the phaseout of HFC-134a from 2011-2017. The next-generation refrigerant must have a GWP of less than 150, and leak rate restrictions begin in 2008.

The US California Air Resources Board Climate Change has proposed the phaseout of HFC-134a from heavy equipment starting in 2010 and from cars starting in 2017. In the context of all of this, the auto industry wants a single global solution.

DP-1 is a two-component, non-flammable blend. The major component is a new non-flammable, fluorine-based compound. The minor component is a commercially available refrigerant.

According to DuPont, DP-1 offers properties and performance similar to that of R134a while featuring zero ODP (Ozone Depletion Potential) and a very low GWP estimated at 40.

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November 29, 2006 in Climate Change, Emissions, Vehicle Systems | Permalink | Comments (14) | TrackBack (0)

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This is good. 3M also has heat transfer fluids called HFEs that are much less harmful. They can also be used as heat recovery fluids for getting more out of ICEs with expansion scrolls and turbines.
Since 70% of the energy in ICEs is rejected heat, there is work to be done there.

Could some of the ICE important wasted heat energy be economically converted to operate the vehicle HVAC (including the AC + electronic + electrical gadgets etc)?

Secondly, if wasted heat is recovered to operate other on-board support sub-systems, could the main ICE engine be down sized proportionally?

A smaller, lighter higher performance battery would also help.

Harvey D. -

in theory, the heat transported by the coolant (of similar magnitude as that delivered by the crankshaft) could be used to power an absorption chiller. These devices use a combination of two substances that are miscible in any proportion, one of which will evaporate almost completely out of the solution well before significant amounts of the other do. The most commonly used systems are H2O-NH3 (lowest achievable temps ~ -60 deg C) and H2O-LiBr (a salt; lowest achievable temps > 0 degC). As with any refrigeration technology, the lower your chiller temp, the more input energy you need to achieve it.

The clue here is that this energy comes in the form of heat plus a negligible amount of electricity for a flow pump, rather than valuable mechanical work. Absorption chillers have a much lower coefficient of performance (COP, indicating cold energy produced vs. input energy) of 0.7-1.1 for single-stage units with internal heat exchanger. For comparison, the COP of a traditional R134a chiller is about 3, but that goes back down to 1-1.5 when you include the losses in the dedicated engine/electric power used to drive the compressor.

Since absorption chillers are substantially more expensive to construct, they really only make sense if you have a reliable stream of low-grade waste heat or, if spot prices for your input energy are highly volatile (e.g. wholesale electricity in the summer in California). In a vehicle powered by an ICE, there is of course abundant waste heat, both high grade (exhaust gas) and low grade (engine coolant). While you can use the former to drive a turbocharger, turbocompund, pressure cell booster or thin-film thermoelectrics, the latter is only useful for space heating and via absorption chillers, for cooling.

Note that in large diesel engines, there are additional sources of heat from the intercooler and the EGR cooler. You could use these plus the engine coolant to not only provide a/c for the driver cabin/passenger compartment or cargo hold but also to interchill the fresh charge. The device would be located between the intercooler and the intake manifold. As long as you don't run into condensation and ice formation problems, reducing the intake temperature by an additional 30 Kelvin (about 10% in absolute terms) will let you achieve the following: higher thermodynamic efficiency, increase specific power at the same peak process temperature and/or sharply reduce peak process temperature (and hence, engine-out NOx levels) at the same specific power level.

Unfortunately, there are a number of technical reasons absorption chillers are not currently being used even in large vehicles such as cruise ships, trains, buses and refrigeration trucks:

(a) The traditional design of the absorber component is based on a fine falling mist of lean solution. This has been proven highly sensitive to vibrations and hence unsuitable for mobile applications. A promising new approach based on more robust and compact membrane absorbers is being developed in Germany:

http://www.itt.uni-stuttgart.de/~schaal/index.en.html

(b) Vehicles may be parked in freezing temperatures. Any pure water in any part of your system is likely to cause some burst pipes. This pretty much rules out the cheaper LiBr route, which relies on water as the refrigerant. The NH3 route is viable but sealing is essential as ammonia is toxic at concentrations at which you can smell it. That immediately raises a crash safety issue as well (imagine an injured person unable to free themselves from the wreckage subjected to ammonia fumes)

(c) An aborption chiller system require a minimum of 4 heat exchangers, compared to 2 for a traditional a/c unit. These require space and add weight to the solution.

(d) the dynamic response of absorption chiller systems is relatively poor compared to traditional a/c. Moreover, chiller power is constrained at low engine loads. This would be a problem if you were caught in a traffic jam in the middle of summer. Excess ambient temperatures, especially near the head, tend to reduce driver attentiveness and increase aggressiveness, so vehicle a/c is a safety as well as a comfort issue in hot weather. Low chiller power during rest periods for the driver is also problematic for cargo refrigeration applications.


http://projects.bre.co.uk/cool/magnetic.htm

just stop all that stupid cfkw and fkw and whatever contains halogens

>>>
Could some of the ICE important wasted heat energy be economically converted to operate the vehicle HVAC (including the AC + electronic + electrical gadgets etc)?

Secondly, if wasted heat is recovered to operate other on-board support sub-systems, could the main ICE engine be down sized proportionally?
<<<

BMW is planning on this to augment the power output of future models. I think the article was on this site in the last week or so.

What happened the idea of using a CO2 based A/C system? Seems like Toyota was working on a system that would heat or cool. Last time I saw any mention was here on GCC some several months ago. I wonder if the use oc CO2 would be seen as a way to consume some of the excess in our enviroment or as another potential source of emmissions?

Rafael:

Thank you for the info. On board energy conservation-recuperation does not seem to be an easy thing to do.

Harvey D. -

well, turbochargers and for HDVs, mechanical turbocompounds, are very feasible today, for both gasoline and diesel engines. There are also R&D projects on electric turbocompounds, both standalone (TIGERS) and as electrically assisted turbochargers/generators. Thermoelectrics are also progressing, though they are not a near term prospect for mass production. All of these leverage the high-grade waste heat.

Power-centric hybrids can recuperate the kinetic energy of the vehicle via recuperative braking. Storage systems include ultracaps, hydraulic accumulators and, in theory, pneumatic accumulators.

What no-one has done so far is leverage the waste heat in the coolant for anything other than space heating. Absorption chillers would be one option.

There have been attempts to increase the coolant (not necessarily water) pressure in the engine yielding wet steam. This is then superheated by a heat exchanger in the exhaust, to drive a small radial steam turbine, which is mechanically connected to the crankshaft via a CVT. The spent steam is condensed in a radiator and the water re-pressurized. BMW engineers call this co-generation concept "turbosteamer" but it is still far from market-ready. On big problem is that a lot of the heat scavenged from the exhaust gas needs to be lost via the radiator. The cross-sectional area of a car's engine compartment is limited and placing the radiator at a severe angle typically not possible.

Rafael Seidl,
One way to disperse some of the heat would be through a heat sink, that doubles as a skid plate, underneath the vehicle. Aluminum, or heat conducting carbon composites, would be preferable. Designs must account for the fact that such a heat sink plate would get dirty, and dinged up over time.
__If the steam is at 600C (873K) and the post radiator fluid comes out to 100C (373K), efficiency comes out to ~57%. Accounting for mechanical/electrical losses, and energy used/lost throughout the process, we could see something in the order of 2/5-4/5 of 57%. Pressurised setups may see better efficiencies, depending on pressurising systems.
__This is enough to run a turbo/supercharger, electrical/mechanical parts/accessories, after the engine is warmed up. Thus, the greatest benefits would likely be after 5-10 min of driving. Vacuum flasks and engine management, would speed this up a bit.

I like a Stirling cycle heat pump system. Even dry air could be used as the working fluid.

If you look at the BMW turbosteamer, you see that some of the heat goes out the cooling system and some goes out the exhaust. If you could capture both of those heat sources using a Heat Transfer Fluid like an HFE phase changed through a scroll expander, you could add power to the engine like the turbosteamer or GM BAS does.

Jason,

I haven't heard of CO2 cooling for passenger vehicles, but AFAIK it's beginning to see commercial use in e.g. grocery stores and and delivery trucks for frozen goods etc.

One of the main reasons for the interest in CO2 is in fact the environmental benefits. The amount of CO2 emitted in regular power production is so huge that a small amount of leakage in cooling systems is completely insignificant in comparison. And indeed, AFAIK industrial CO2 is gathered from exhaust gasses that otherwise would go straight into the sky, so no net global warming. But compared to "classical" refrigerants like R12 or R134, CO2 is nontoxic, nonflammable and non-ozone depleting.

Tom Deplume -

yeah, a hermetically sealed small free piston stirling engine to generate electricity using the exhaust heat would be an interesting concept, especially when paired with a starter-alternator. Linear free piston designs generate vibrations due to free mass forces, though.

As indicated, the main problem, other than cost, is the need for bigger radiators. Slinging them underneath the vehicle is not a viable idea, due to soiling and the high risk of leaks. Integrating a radiator based on heat fins with the hood or roof would work but look decidedly funky. Besides, the hood would be heavy to lift and almost certainly violate crash safety rules for pedestrians. For roof mounting, you'd have to provide thermal insulation for the passenger compartment and may have to forfeit the option of fitting a roof rack or cargo pod.

The other issue with co-generation is that if you cool the exhaust gases too much, the water produced during combustion condenses out and causes corrosion in conjunction with the traces of sulfur and phosphorus left in the fuel and engine oil.

Jason -

when used as a refrigerant, CO2 is usually referred to as R744. There are a several designs under development in Germany, one big problem is that you need much higher operating pressures which places high demands on the seals. Unfortunately, a car A/C compressor can eat several kW of power, more than the regular 12V grid could handle. Very few cars use electrically units, which would permit hermetic sealing.

GHG emissions from vehicle A/Cs are minor compared to the CO2 the emit but not negligible. Unless an A/C unit is actually operated every couple of weeks for a short while, the compressor and seals tend to wear out prematurely. Combined with slightly porous hoses, you can actually lose up to 8% of the fluid volume this way in a year. The GHG potential of R134a refrigerant is much lower than that of the now-banned R12, but it is still much higher than that of the same mass of CO2. Evidently, DP-1's GWP is just 40, only slightly worse than methane (which is released by natural sources in much greater quantities).

I was thinking of a fluid to fluid tube in tube heat exchanger for the cooling system and then to fluid cooling for the exhaust headers as a "topping" cycle before the scroll. Whether you drove the engine with a scroll and belt or just had the scroll drive an alternator would be an application issue, maybe both. It sure sould be nice to recover some of that rejected heat.

Cooling cycle which may work with the waste heat to make us able for using in the automotive industries are not limitted to traditional absorption cycle.
It can be used other methodes such as pumping the lean absober liquid instead of free falling to elimiate the vibration problems in the absorption cycle or even using of some other methodes such as ejection sys.in a combination of absorption and compressed cycle.

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