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Vehicle technology improvements normally involve proper maintenance, improving the engine or vehicle body, or reducing inertia with the main aim of reducing the energy intensity (energy use per useful product) and so reducing carbon emissions. Regular servicing, including regular tire and oil checks, and engine tuning can lead to fuel savings of 2-10% (Davidson, 1992; Pischinger and Hausberger, 1993). Use of three-way catalytic converters along with electronic fuel injecting systems can result in reduction of ozone precursors (unburned HC, CO, NOx) emitted from gasoline cars and heavy-duty vehicles, but the effect on global warming is uncertain because the impact of fuel consumption is also uncertain (IPCC, 1996). Improved combustion by use of gas turbines and low-heat-rejection engines can potentially result in higher efficiency and, thus, in lower emissions, but there will be a need for high temperature materials along with compatible high temperature lubricating systems. Also, direct-ignition stratified-charge engines can be more efficient because of their ignition enhancing qualities. Details of these potential reductions are given in Table 8.2. The potential exists for increasing vehicle mileage and, therefore, energy intensity by reducing the aerodynamic drag and rolling resistance leading to improved efficiency and, thereby, reducing the emissions (ETSU, 1994; DeCicco and Ross, 1993). Similarly, through size reduction, material substitution or component redesign, the inertia can be reduced and so lower the fuel consumption (DeCicco and Ross, 1993). Improving the transmission system to electronically allow for optimal speed and load conditions can result in energy savings and reduced emissions (Tanja et al., 1992; NRC, 1992). More details of these potential reductions are summarised in Table 8.3.
| Table 8.2 Technical and potential combustion control technologies (Source: IEA/OECD, 1998) | ||||||
| TECHNOLOGY | EXAMPLES | STATUS | TECHNICAL FEASIBILITY | CONVERSION EFFICIENCY | ENVIRONMENTAL IMPACT | MARKET POTENTIAL TIME FRAME |
| ICE CONTROL | ||||||
| 1. Improved Exhaust Treatment |
Catalyst traps, exhaust gas recirculation (EGR) Intake and exhaust systems Advanced emissions abatement in heavy-duty vehicles |
Deployed in autos� Limited diesel application |
Continuing after treatment improvement Allows continued use of ICE |
Slight decrease for significant Ox reduction Increased back pressure reduces efficiency in diesels |
Up to 97% control for HC and CO Up to 85% control for Ox Up to 85% control for particulate |
0-5 years |
| 2. Improved Combustion |
Ceramic components Ignition systems Flow dynamics variable valves Turbine engine |
Incremental improvements |
Good variety of technology Available technology must integrate with current ICE |
5-10% engine efficiency gains | Ox particulate and CO2 reduction | 0-10 years |
| 3. Fast Warm-up |
Thin wall engines Start/stop with flywheel storage |
Incremental improvements | Transient time decreased by 50% | Average efficiency gains of <5% |
<10% average reduction <30% reduction in first 60-120 seconds |
0-10 years |
| Table 8.3 Technical and potential vehicle improvements options (Source: IEA/OECD, 1998) | ||||||
| TECHNOLOGY | EXAMPLES | STATUS | TECHNICAL FEASIBILITY | CONVERSION EFFICIENCY | ENVIRONMENTAL IMPACT | MARKET POTENTIAL TIME FRAME |
| VEHICLE IMPROVEMENTS | ||||||
| 1. Drag and rolling resistance reduction | Drag coefficient reduction Reduced rolling resistance Reduced bearings friction |
Commercial potential for improvement in low-friction bearings and lubrications Low-friction tyros to be tested | Continuation of improvements dependent on material properties & cost of manufacture Study on basic physics | Speed sensitive benefits Gains of 1-5% possible | Reduction of all emissions in proportion to efficiency gains | 0-10 years |
| 2. Structural weight | Light structures Bonded/composite structures Light powertrains |
Commercial/demonstrated Bonded structures in limited use Composite materials in most vehicles |
Continuation of improvementsLimited by material properties and relative cost of manufacture | 0.2 to 0.4% gain for every 1% weight reduction | Reduction of all emissions in proportion to efficiency gains Greater effect on acceleration emissions (urban traffic) as vehicle inertia is diminished |
0-10 years |
| 3. Transmission | Electronic shift Multistep lock-up Continuously variable transmission (CVT) electric drives Drivelines and suspensions | Commercial/demonstrated technology CVT available High power CVT in prototype Lock-up and electronic control | CVT/IVT in widespread use in next decade Hybrid powertrains feasible with CVT/IVT |
10-15% gain over manual with CVT or IVTelectronic drives could further increase this conversion efficiency | Reduction of all emissions in proportion to efficiency gains Engine operation optimised, decreasing emissions even more than efficiency improvement | 0-10 years |
| 4. Accessories | On-board electronic controls Constant speed drives Efficient components |
Demand responsive systems gaining preference Constant speed systems in demonstrations |
Highly feasible for constant speed High efficiency accessory systems |
<5% efficiency gain | Emissions reduction facilitated by on-board electronic controls and sensors | 0-10 years |
Trends show that if priorities shift among manufacturers and users, improvements of 10-25% in energy intensity may be achievable on cars by 2020 at a higher cost, but the potential for commercial vehicles will be smaller. However, fuel savings and environmental gains may be offset by the increase in number of vehicles and driving (Wootton and Poulton, 1993).
The trend in buses for higher level of comfort and safety, and more powerful engines has tended to increase fuel consumption per seat compared with old buses, but this can be reduced by using advanced composite materials and turbo-compound diesel engines. Electric buses are in use as minibuses in urban areas, but they have higher GHG emissions than diesel buses when the primary emissions than diesel buses when the primary energy used is from fossil sources. Hybrid buses (diesel/electric) are now being tested because they can save up to 30% in energy if the motor/generator efficiency is about 85%. Alternative fuels (CNG, alcohol fuels and vegetable oils) are used in buses and when rapeseed methyl ester is used as substitute for diesel, life-cycle GHG emissions can be reduced by 25-50% (IEA/OECD, 1994). Use of turbo-charging and charge cooling in engines of trucks improves the fuel economy and so reduces GHG emissions, but retarding fuel injection worsens the fuel economy. Potential exists for improvement in fuel economy based on developments of new engine materials (IEA/OECD, 1993). Fuel economy can also be improved in the design of trains. About 5-10% savings is possible in diesel locomotives and up to 30% if a regenerative braking system is used in urban metro systems; 15% savings could be realised in suburban train systems and 5-10% for inter-city systems.
Energy intensity in aircraft can be improved with engine modifications and new engine designs. Future improved supersonic engines that are expected after 2010 may lead to an increase in energy efficiency and lower emissions, but this improvement could lead to increase traffic movements (Balashov and Smith, 1992).
Energy intensity for boats can be improved by modifying marine engines by making improvements in the hull and propeller designs that could yield to higher energy gains. The use of vertical-axis turbines as sails can assist the engine and result in energy savings (CEC, 1992).
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