In heavy duty vehicles, 33% of the fuel energy is used to overcome friction in the engine, transmission, tires, auxiliary equipment, and brakes. In total, only 34% of the fuel energy is used to move the vehicle. Worldwide, 180 billion liters of fuel was used in 2012 to overcome friction in heavy duty vehicles. A reduction in friction results in a 2.5 times improvement in fuel economy, as exhaust and cooling losses are reduced as well.
Globally a single-unit truck uses on average 1,500 liters of diesel fuel per year to overcome friction losses; a truck and trailer combination, 12,500 liters; a city bus, 12,700 liters; and a coach, 7,100 liters. By taking advantage of new technology for friction reduction in heavy duty vehicles, friction losses could be reduced by 14% in the short term (4 to 8 years) and by 37% in the long term (8 to 12 years). In the short term, this would annually equal worldwide savings of 105 billion euros, 75 billion liters of diesel fuel, and a carbon dioxide emission reduction of 200 million tonnes.
The global energy use study of trucks and buses showed huge possibilities to reduce fuel consumption by new friction lowering technologies. Potential new remedies to reduce friction in road vehicles include the use of advanced low-friction coatings and surface texturing technology on sliding, rolling, and reciprocating engine and transmission components, new low-viscosity and low-shear lubricants and additives, and new tire designs that reduce rolling friction. The figure above shows the level of friction in an average heavy duty vehicle in use today in the various friction contacts (Truck & bus 2000), the lower level reported in the best new vehicles today (Truck & bus 2013), the lowest levels reported in research laboratories so far (Laboratory 2013) and levels foresighted to be reached by future research and development work (Truck & bus 2015).
Energy is a key resource for our society today and will be crucial for our sustainability in the future. Much of our energy needs comes from non-renewable fossil fuels. However, there are limitations in the availability of these fuels in the long run. Burning of oil and other non-renewable products produces large volumes of greenhouse gases that give rise to climate change. Energy is also a major cost issue for many industries. About 100 million terajoule is used annually worldwide to overcome friction and that is one fifth of all energy produced. The largest quantities of energy are used by industry (29%) and in transportation (27%).
The results of this study are used by researchers, industrial experts and decision makers when considering energy, environmental and cost issues in future research and development work as well as setting priorities for actions to reduce energy use for sustainable solutions on societal, sectorial, company and technical level.
Kenneth Holmberg, VTT
VTT Technical Research Centre of Finland
Argonne National Laboratory, USA