فن آوری خودرو تحت محدودیت CO2: تجزیه و تحلیل تعادل عمومی

A study is presented of the rates of penetration of different transport technologies under policy constraints on CO2 emissions. The response of this sector is analyzed within an overall national level of restriction, with a focus on automobiles, light trucks, and heavy freight trucks. Using the US as an example, a linked set of three models is used to carry out the analysis: a multi-sector computable general equilibrium model of the economy, a MARKAL-type model of vehicle and fuel supply technology, and a model simulating the split of personal and freight transport among modes. Results highlight the importance of incremental improvements in conventional internal combustion engine technology, and, in the absence of policies to overcome observed consumer discount rates, the very long time horizons before radical alternatives like the internal combustion engine hybrid drive train vehicle are likely to take substantial market share.

Given the strong coupling between economic growth, fossil energy use, and greenhouse gas emissions (GHG), large-scale introduction of advanced, fuel-efficient technology is an essential component of a comprehensive strategy for GHG emissions abatement. Already the single largest user of final energy and source of CO2 emissions in the United States, the transport sector is steadily increasing its share of both. Partly in response to the threat of climate change, the motor vehicle industry is developing a number of fuel-saving technologies and beginning experimentation with their introduction into consumer markets. Several of these offer incremental improvements in fuel efficiency through reduced driving resistance (aerodynamic drag, rolling resistance, acceleration resistance) and improved mechanical drive train efficiency. Other developments aim at replacing the conventional mechanical drive train with a hybrid mechanical–electric one, and still more radical designs incorporate fuel cell technology (Weiss et al., 2003). Anticipating which of these vehicle types would likely move beyond niche markets to gain substantial economic market share is crucial for vehicle manufacturers in directing their R&D expenditures. It also is important for governments considering incentives to stimulate the introduction of more fuel-efficient systems. In response to these needs, we examine the market penetration of these technologies under a CO2 emissions constraint. Our analysis considers the role of automobiles, light personal trucks (minivans, sport utility vehicles, and pick-up trucks), and three classes of freight trucks—all within the context of an economy-wide, multi-sector emissions control effort. The study assumes an economically efficient GHG control policy, resulting in a common emissions price across sources. Thus the relative role of transport in relation to other economic sectors is endogenous to the analysis. Questions of this kind are usefully addressed using a computable general equilibrium (CGE) analysis framework, which takes account of the interdependencies among economic sectors through price interactions, the sharing of intermediate inputs and outputs, and substitution in satisfying producer and consumer demands. Gaining advantages of the general equilibrium approach requires a simplified representation of production technology, however, making it difficult to represent specific vehicle designs. To incorporate the desired technology detail we couple a CGE model to an engineering-process model of energy systems and transport technology, linking the two by means of a model of the evolving split of total transport among different transport modes. The resulting model system is summarized in Section 2, along with a description of the vehicle technologies considered in the analysis. Two of the issues that arise in such a study of transport technology merit some special discussion. They are the treatment of discount rates revealed in consumer behavior, and the long turnover rates of transportation infrastructure. These features of the analysis are discussed in Section 3. The results of the analysis, which covers a period to 2030, are shown in Section 4, with a focus on economic market penetration for an unconstrained reference case and for GHG control policies at two different levels of stringency. The implications of the results for greenhouse gas policy development are discussed in Section 5.

This analysis has been conducted on the assumption that a policy to reduce greenhouse gases would be carried out in the most efficient way economically, which would imply a similar penalty on emissions across all sectors of the economy. Also, it is assumed that the US will have no major program to modify the behavior of consumers, as they make tradeoffs between the current cost of a vehicle purchase and expected future savings from increased fuel economy. Analysis results under these conditions suggest that caution is in order in anticipating substantial early shifts in transport technology in response to control policies. There will always be niche markets for advanced fuel-efficient vehicles, even if more expensive. However, over the next 20–30 years, vehicle technology is likely to be dominated by marginal improvements in conventional internal combustion engines. At least under the emissions targets studied here, if implemented in a way that imposes the same emissions price on all sectors, more radical designs like the aluminum body or the hybrid drive train are not likely to take a substantial share of the US consumer market.9 Familiar characteristics of the transport sector contribute to this picture of a slow transition to radically different vehicles. Substantial improvements in fuel efficiency come only with an increase in first cost of the vehicle, and it is well established that consumers apply relatively high discount rates when weighing the advantages of better gas mileage within the mix of personal vehicle characteristics.10 Subsequent lags in the scale-up of production and the long (and growing) road life of vehicles naturally lead to a slow process of fleet turnover, even when new designs are in demand. Thus one important conclusion from these sample calculations is that visions of this sector contributing to emissions reduction by a jump to the hybrid or a hydrogen vehicle are highly misleading, and policies that focus on these radical designs to the exclusion of incremental change are going to be environmentally ineffective and economically wasteful. Although we do not explore the returns to R&D in our model analysis, it is evident that research, development, and demonstration programs for significantly more fuel-efficient technologies need to continue. Such programs may contribute to lower the costs of more advanced internal combustion engine, hybrid, and fuel cell vehicles and to make sure that these technologies are mature in the event that still stronger reductions in GHG emissions than examined here are imposed. As an alternative to the price-based policy considered here, policy makers have imposed corporate average fuel efficiency (CAFE) standards. We do not have the facility to adequately analyze that option, but several observations are in order. First, imposition of CAFE as an alternative to a higher fuel price (reflecting an emissions penalty) reduces the marginal costs of driving, which would produce a demand gain, in contrast to the demand loss shown clearly in Panels C and D in Fig. 2. This “rebound” effect would lead to a number of undesired outcomes (e.g., increased conventional air pollution, congestion, property damage, loss of life) that require a welfare analysis beyond our scope. The CAFE option is politically attractive because the cost to the consumer is largely hidden. But there is a cost nonetheless. Again, we have not prepared an estimate of the consumer surplus loss from this type of constraint, but a rough idea of the magnitude can be had by simply asking what subsidy on automobile price would be required to induce consumers to drive the mix of automobiles consistent with the Kyoto restriction, if fuel prices remained at reference levels. Admitting the shortcomings of our simplified model of the vehicle fleet, we calculate that the subsidy in 2020 would need to be $3000 per automobile, or an annual budgetary cost of nearly $30 billion. Naturally, there are limitations to our analysis that deserve mention, although they do not change the fundamental conclusions. First, the overall vehicle market is comprised of a number of niche markets, one of which is that for the hybrid vehicle. There are customers who will pay several thousand dollars over an ICE-only automobile with equivalent space, safety and performance. But experience shows that this niche is small compared to the total volume of vehicles sold in the US each year. Next, while the vehicle technology costs in Table 1, Table 2 and Table 3 are constant over time, some cost reduction can be expected through experience, at least for the more advanced fuel-saving technologies. A repeat of the analysis starting with current costs and applying some assumption about cost reduction with experience could slightly change the results, most likely in the form of slower adoption early in the period and faster later. Finally, our analysis allows only changes in vehicle technology, not size classes. We are not able to study how an increasing consumer fuel price will affect vehicle size between and within the broad classes of automobiles and personal trucks. The results reported for alternative penetration levels of personal trucks are based on a simple assumption about this effect; clearly, this phenomenon requires a more complete analysis of consumer response to the variable cost of driving. Importantly for our analysis of technology change, however, this additional area of flexibility would seem to only further delay the response of vehicle technology to increasing carbon penalties.