CARB Climate Change Tech and Cost Review Workshop
20 April 2004
In 2002, California enacted Assembly Bill 1493 (AB 1493) -- the Pavley climate change bill. The bill requires the California Air Resources Board to develop CO2 (greenhouse gas) standards for vehicles in model year 2009 and beyond.
California has consistently led the nation in the stringency of its emission control, and appears to be doing so again. In 2003, NY Governor Pataki said that NY would echo California, and a bill comparable to 1493 is pending in the NY legislature. In 2004, NJ opted to join in the California Low Emissions Vehicle program. Comparable action is also under consideration in Connecticut, Vermont, Massachusetts and Maine.
The work undertaken by ARB and its contractors is coming to fruition. Today (20 April) ARB is holding a public workshop in Sacramento presenting a summary of the findings. Presentations are available on the site. The draft report is also posted on the ARB Climate Change site.
The research team ran simulations 150 different configurations of technologies and scenarios, compared the results to a baseline, and derived the resulting CO2 reductions and cost increase (or decrease, in some situations).
Clearly, in any simulation, the value of the output is determined by the quality of the input and the model. ARB worked with AVL, using its CRUISE tool on the actual simulations.
In any effort such as this, there will be much discussion not only over the assumptions and the bias implicit in the assumptions, but also in the choice of partner and the tool. Weve seen some of that discussion during the Q&A sessions in the workshop today. Thats a good thing, although it may try the patience of both those being asked the questions as well as the questioners.
What strikes me are:
- The number of technologies coming onstream
- The differences made through the combinations of those technologies
- The results of complex interactions of complex systems. There are measurable (simulated) differences based on factors even such as whether or not your windows are down or up to reflect air conditioning use.
Heres a quick sample of some of the emerging technologies for conventional gasoline engines that can be used to mitigate CO2 emissions. I'll look at some of the alternative technologies in a different post.
Engine Valvetrain Modification. Variable valve timing and lift can reduce CO2 emissions by managing more precisely when and how much the valves open and close. Increased control of intake and exhaust valves also supports selective cylinder deactivation (DeAct) for better engine management. Also on the horizon are camless valve actuation systems, replacing the belts, chains and gears with electrohydraulic or electromagnetic actuation of the valves. Manufacturers are seeing a strong first to market advantage for whoever gets this right first.
Charge Modification. Increasing the pressure of the air-fuel mix entering the cylinders can improve engine power, which in turn allows the manufacturers to reduce the size of the engine. This is a common theme in many of the approaches: make the engine technology more powerful and efficient, so that smaller engines are required for equivalent or even better performance for the driver. Rightsizing or downsizing the engine, in other words.
Gasoline Direct Injection. Conventional gas engines inject fuel into a manifold, wherein it evaporates, is mixed with air and then sucked into the cylinder for combustion. a GDI systems injects the gas directly into the cylinder where the air is already compressed (similar to the diesel approach). There are currently two different approaches to implementing this. One -- lean burn -- offers substantial CO2 reduction, but offsets that with complications for controlling emissions of oxides of nitrogen (NOx). The other -- stoichiometric -- offers smaller CO2 reductions, but without the NOx aftertreatment issues.
Engine Accessory Improvement. Electrifying engine accessory subsytems (such as pumps) can reduce the CO2 losses associated with powering them mechanically.
42-volt Systems. A 42-volt electrical system can accommodate more powerful electrical accessories onboard the vehicle (espresso machine?) and an integrated starter generator. This latter item recoups energy while decelerating through regenerative braking, and can provide instantaneous engine restart to avoid idling.
Homogeneous Charge Compression Ignition. This technique, which relies on precise control of temperature and pressure in the combustion chamber to enable spontaneous and homogeneous ignition of the air-fuel mixture, can be applied to engines using a variety of fuels, including gasoline and diesel. This is not yet commercially viable.
Other technologies not tied to gasoline include:
Diesels. High speed direct injections (HSDI) diesels with compression-ignition engines with higher compression ratios, turbocharging and lean air-fuel ratios provide significant CO2 reductions compared with conventional gas engines.
Transmissions. Increasing the number of gears to 5 or 6 from the standard 4 on most of today's models allows the engine to operate in more optimum ranges for minimizing CO2 emissions. Automated Manual Transmissions and Continuously Variable Transmissions are also options, although ARB notes that manufacturers seem to be obtaining most of the emission abatement of a CVT using a 6-speed automatic transmission at significantly less cost.
Engine Friction Reduction. Reducing the friction of engine components, through the improved design of those components, through the use of different materials, more optimal thermal management and used of advanced oils can cut CO2 emissions.
Aerodynamic Drag and Rolling Resistance Reduction. Two key areas for reducing drag are the shape of the vehicle and the rolling resistance at the tires. The former can be addressed through design, the latter through design and material improvements.
Aggressive Shift Logic. The shift logic determines when automatic transmissions switch from one gear to another. A more aggressive shift logic allows more flexible shifting of gears, which in turn allows for operation at more optimal low emissions regions.
There are some commonalities across these areas: greater use of electric rather than mechanical control; greater use of onboard computational support (hardware and software); increasing use of newer materials. Many of these advances will support the alternative fuel vehicles as well.
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