چشم انداز پلاگین در وسایل نقلیه الکتریکی هیبریدی در ایالات متحده و ژاپن: تجزیه و تحلیل تعادل عمومی

The plug-in hybrid electric vehicle (PHEV) may offer a potential near term, low-carbon alternative to today’s gasoline- and diesel-powered vehicles. A representative vehicle technology that runs on electricity in addition to conventional fuels was introduced into the MIT Emissions Prediction and Policy Analysis (EPPA) model as a perfect substitute for internal combustion engine (ICE-only) vehicles in two likely early-adopting markets, the United States and Japan. We investigate the effect of relative vehicle cost and all-electric range on the timing of PHEV market entry in the presence and absence of an advanced cellulosic biofuels technology and a strong (450 ppm) economy-wide carbon constraint. Vehicle cost could be a significant barrier to PHEV entry unless fairly aggressive goals for reducing battery costs are met. If a low-cost PHEV is available we find that its adoption has the potential to reduce CO2 emissions, refined oil demand, and under a carbon policy the required CO2 price in both the United States and Japan. The emissions reduction potential of PHEV adoption depends on the carbon intensity of electric power generation. Thus, the technology is much more effective in reducing CO2 emissions if adoption occurs under an economy-wide cap and trade system that also encourages low-carbon electricity generation.

The large and growing fraction of greenhouse gas (GHG) emissions from the transportation sector present a major challenge to global climate change mitigation efforts. Worldwide, transportation ranks second after electric power as the largest source of emissions, contributing about 20% of the total in recent trends and future projections (IEA, 2006). GHG emissions from transportation, mostly in the form of carbon dioxide (CO2), are expected to increase with the projected growth of personal vehicle fleets in both developed and rapidly developing countries. At present, transportation accounts for more than one-third of end-use sector CO2 emissions in the United States (US) and more than one-fifth in Japan (EIA, 2006 and MOE, 2007). Personal vehicles contribute 62% and 50% of transportation emissions in the US and Japan, respectively (EPA, 2006 and GGIOJ, 2008). The plug-in hybrid electric vehicle (PHEV) has recently been suggested as a low-carbon alternative to conventional transportation that could enter the personal vehicle market within the next decade. Among the other alternatives to conventionally-fueled internal combustion engine (ICE) vehicles are flex-fuel, hydrogen fuel cell, and compressed natural gas (CNG) vehicles. Each of these alternatives, including the PHEV, requires at least some technological advancement to bring down the cost or offer other advantages that enable them to substantially replace the existing fleet of vehicles. Vehicles with flexibility to use high-percentage biofuel blends (flex-fuel vehicles) involve relatively low-cost modifications to existing engine and fuel system designs, but few refueling stations carry these fuels at present. Hydrogen fuel-cell vehicles still have large technological hurdles to overcome to bring them near to commercial viability (NRC, 2004 and Sandoval et al., 2009). The reduction in GHG emissions from CNG vehicles may not be substantial, especially if the natural gas is imported as LNG (Brinkman et al., 2005). Comparing the environmental impact of alternative fuel vehicles requires careful accounting of all emissions related to vehicle manufacturing as well as fuel production and use (Hackney and de Neufville, 2001). We use a computable general equilibrium model to investigate the prospects for PHEV market entry in the US and Japan, and to evaluate the potential associated impact on the energy system and environment. A PHEV is defined by its ability to run on battery-stored electricity supplied from the grid as well as gasoline or diesel in a downsized on-board internal combustion engine (ICE). Our modeling strategy is designed to identify conditions under which the PHEV could most contribute to reductions in greenhouse gas emissions. We examine factors specific to the PHEV technology as well as external market and policy conditions expected to affect its prospects. We then replicate parts of the analysis for the Japanese case. In Japan the private vehicle fleet is smaller, newer, and generally more fuel efficient, fuel taxes are higher, and electricity generation relies much less on coal. Japan is already a leading source of electric-drive vehicles (for example, the Toyota Prius) and related technology, including advanced batteries. By considering both the US and Japanese markets we hope to understand better how these different market conditions could affect the economic competitiveness of PHEVs. Transportation – and the growing fleet of private household vehicles in particular – is one of the most difficult and costly parts of the US economy to achieve emissions reductions. Even a cost-competitive low carbon technology would take several decades to make a significant impact on total emissions due to the slow fleet turnover rate. Concerns about reliability, cost, and ease of use may further prevent rapid increases in PHEV sales. Alternative fuel vehicles have received growing attention over the past decade, and discussion of whether and how to support their introduction through policy has been a matter of considerable debate in the US and abroad (Liu and Helfand, 2009). The ICE has remained the dominant transportation technology since it was first marketed in the early 1900s, and an extensive infrastructure has developed to support it. However, continued reliance on the ICE, even with improvements in fuel economy, is unlikely to be consistent with a climate policy goal of stabilizing atmospheric GHG concentrations within the next century. The article is organized as follows. Section 2 describes the main features of the PHEV technology and its anticipated costs, and compares them to today’s ICE-only vehicles. Section 3 explains how a PHEV sector was implemented in the Emissions Prediction and Policy Analysis (EPPA) model in both the United States and Japan. In Section 4, this modified version of the EPPA model is used to evaluate how two important properties of the PHEV, the vehicle cost and all-electric range, affect the timing of PHEV market entry. We then test the sensitivity of these results to the implementation of a climate policy and the availability of a low carbon fuel substitute, advanced cellulosic biofuels (referred to here as “biofuels”). Section 5 evaluates the impact of PHEV adoption on electricity output, refined oil consumption, carbon emissions in total and by sector, and consumption losses due to the implementation of a climate policy. Section 6 summarizes the conclusions.

We examined the commercial potential of PHEVs, their implications for electricity and petroleum use, and their potential contribution to reducing CO2 emissions in the US and Japan. The results indicated that PHEV vehicle cost could be a significant barrier to market entry, particularly in the absence of a climate policy. The strong climate policy we considered requires a solution to transportation emissions and if the PHEV is the primary low-carbon alternative the policy becomes a very strong incentive for adoption. PHEV costs of 15% above conventional vehicles are very favorable for adoption but markups above 80% are prohibitive unless there are no other low carbon transportation alternatives and there is a strong carbon constraint. Many PHEV cost estimates suggest a cost premium today of around 30–80% above conventional vehicles. At 30% PHEVs become marginally competitive by mid-century without a carbon policy. Thus, a significant contribution from PHEVs would require advances in battery technology that reduce cost and increase range at the optimistic end of experts’ estimates. Another factor affecting the attractiveness of the vehicle is the all-electric range and how that influences the proportion of miles traveled only on electricity. Varying this proportion (essentially the all-electric range of the vehicle) had some effect on commercial viability but much less than the vehicle cost. Availability of other low-carbon alternatives (we consider biofuels) also could affect strongly the commercial viability of the PHEV, especially under a carbon constraint. The availability of biofuels provides an additional cost-competitive source of emissions reductions and thus reduces the incentive to adopt PHEVs. As a result, when biofuels are available, a stringent climate policy has only a mild effect on hastening the market penetration of the PHEV. If PHEVs are available at a 15% cost premium over conventional vehicles, they would significantly penetrate the vehicle fleet even without a climate policy over the next century. Their use would contribute to reducing both carbon dioxide emissions related to transportation as well as reliance on refined oil in the US and Japan. In the absence of climate policy, the introduction of the PHEV results in an increase in electricity use and in emissions from electric power generation. However, the reduction in tailpipe emissions more than offsets this increase to yield a net reduction in CO2 emissions. In percentage terms, the net emissions reductions are larger in Japan than in the United States because in Japan PHEV adoption is more rapid and power generation is less CO2-intensive than in the US. Under the climate policy we considered, electricity generation eventually comes exclusively from low carbon sources and so the CO2 benefits of PHEV introduction are greater. Thus technology-specific policies that focus exclusively on promoting the PHEV as a solution for CO2 emissions will not take full advantage of them to the extent they rely on CO2-intensive electricity. In the near term, PHEVs may also be more effective in countries such as Japan where power generation is less CO2-intensive than in the US, which relies heavily on coal.