Energy Sources for Road Transport in the Future

S ince hominid started to utilize fire as a power source, the entire human society has advanced so much in civilization and economy.Until now, 4/5 of the world energy consumption relies on fossil fuel, especially for automobiles.Our interest is how to make the emerging new energy vehicles save more cost, function more efficiently, and release fewer pollutants than traditional vehicles with internal combustion engines as we enter a new stage dominated by emerging energy vehicles.Transportation is a major consumer of energy, and it is also a major source of carbon dioxide.Supply, demand, and distribution in the whole transportation system are interrelated, but each is also independent.Therefore, it is crucial to optimize petroleum extraction, electricity generation, and energy transformation efficiency of distinctive automobiles and to further improve the energy efficiency of automobiles, especially electric vehicles, which will greatly mitigate our reliance on raw energy.By evaluating tank-to-wheel (TTW) efficiency, we found that the efficiency of traditional internal combustion engines is only 12.6%.On the contrary, because electric vehicles have simple structures and use electricity to power either part or all of their wheels, they have higher efficiency.The TTW efficiency of hybrid and pure electrical vehicles can reach 26.6 and 54%, respectively. 1However, because hybrid cars also need fossil fuels, their well-to-wheel (WTW) efficiency is only 20%, still higher than the efficiency of the traditional model. 2 Currently, to improve the energy efficiency of automobiles, we need to consider differences in each country's energy structure and characteristics of different electric vehicle models.We believe that electric vehicles still have much room for improvement in efficiency with the advancement of energy technology and technology in electric vehicles.Emerging Energy Vehicles and Fuel Consumption.To better compare the energy efficiency of different vehicle models, we calculated the energy consumption of traditional, hybrid, pure electric, and fuel cell automobiles with the same wheel power output, as discussed below (see Figure 1).Traditional internal combustion engine (ICE) vehicles are the least energy efficient and have an efficiency of only 12.7%.Pure electric vehicles have an efficiency of 51.6%, which is the highest.Fuel cell vehicles (FCVs) and hydrogen ICE (HICE) vehicles have efficiencies of 28.3 and 26.6%, respectively.From TTW, the efficiencies of hybrid electrical vechicles (HEVs), battery electric vehicles (BEVs), FCVs, and ICE are 22.6, 21.8, 21.4, and 10.8%, respectively.Clearly, we can conclude that hybrid vehicles have an advantage if we only consider using petroleum to power automobiles.Figure S1 lists the electricity conversion efficiency of major energy sources (including raw oil, natural gas, coal, nuclear power, and other new energy) and sources of electricity production in several countries in Table S1. 3