Cost-Optimal Technology and Fuel Choices in the Transport Sector under a Stringent Climate Stabilization Target

Abstract

Climate change is one of the most serious challenges in the 21st century. To avoid dangerous climate change, a variety of greenhouse gas (GHG) mitigation actions have increasingly been taken in all sectors of the global energy system. The International Energy Agency (IEA) indicated that the transport sector accounted for about 23% of energy-related CO2 emissions in 2005 and is likely to have a higher share in the future unless strong action is taken (IEA, 2008). Furthermore, the IEA showed that if a halving of 2005 energy-related CO2 emissions is to be achieved by 2050, the transport sector must make a significant contribution, despite the fact that transport’s central economic role and its deep influence on daily life have made rapid changes difficult to achieve (IEA, 2000, 2008). It is, therefore, critically important to find a long-term, cost-effective strategy for reducing CO2 emissions from the transport sector. So far, several studies have been carried out to address this issue using long-term global technology-rich bottom-up energy system models, with notable examples being Azar et al. (2003), Turton (2006), IEA (2008, 2009), and Grahn et al. (2009). Although these studies investigated the future role of alternative propulsion systems and fuels in the light-duty vehicle sector under CO2 constraints, all of these studies except IEA (2008, 2009) did not place sufficient focus on the other modes of transport. The IEA (2008, 2009) derived the results for energy use and CO2 emissions in the transport sector from a number of scenarios using the model covering all modes of transport. However, these scenario results are substantially affected by arbitrary assumptions about the diffusion rates of alternative propulsion systems and fuels. Moreover, these IEA scenarios have a time horizon until 2050, rather than a time horizon until 2100 adopted in the other three previous studies cited above, which makes it difficult to assess the very long-term prospects for radically new transport technologies. In this context, the objective of this chapter is to examine the cost-optimal choice of propulsion systems and fuels for each of 13 transport modes over the 21st century under a constraint that the long-term global mean temperature rise would be limited to 2.0 to 2.4 degrees Celsius. This chapter also presents the results of the sensitivity analysis with respect to three important factors: (1) the climate stabilization target; (2) the cost of a proton 23