Alternative fuels and energy efficiency in transport

Panel: Panel 6. Energy efficiency in transport and mobility

Author:
Kaj Jorgensen, Risø DTU, National Laboratory for Sustainable Energy, Technical University of Denmark, Denmark

Abstract

In conjunction with shifts to alternative fuels it is crucial to simultaneously address the issue of energy efficiency, both at the application level (the vehicle as such) and for the entire fuel cycle. Naturally, this is especially the case for fuels based on fossil fuels but even for fuels based mostly, or even entirely, on renewables it is important - particularly for biomass with is limited resource base. In this respect, the choice between different energy carriers is heavily influenced by dilemmas linked to aspects such as: penetration degree and speed, energy resource flexibility, overall energy efficiency, well-to-wheel impacts, performance and costs. Many biofuels have the advantage of being capable of quick and easy introduction in the transport sector, but at the same time have limited total potentials. Electricity and hydrogen while not offering this quick and easy path, on the other hand is extremely flexible with regard to resource base (including to non-sustainable paths) and do not have the limitations of biofuels. Also they are, potentially, a very energy efficient option, particularly in the case of electricity. Electric vehicles have conversion efficiencies that are, generally, a factor 2-10 better than those of hydrogen, but on the other hand offer much more limited performance (notable regarding range) and possibly higher costs. Plugin hybrid electric vehicles provide an opportunity to reduce, but not necessarily eliminate these problems. The important choice in this context is not just between the main energy carriers but also within each of these (especially for the hydrogen paths). Also the (non-plugin) hybrid electric vehicle, already on the market today, promises an option of a very energy-efficient drive system within the present fuel market as well as alternative fuels. In the power supply system electric, hybrid and hydrogen vehicles may have beneficial impact on the overall system, but these benefits depend on the actual system and its operation. This paper explores these dilemmas, including studies of the link to the power supply system. A crucial focal point is the conflicts between different considerations - rapid intro vs. penetration, energy efficiency vs. flexibility of energy resource performance, costs etc.