Energy-efficient modes of transportation
Energy-efficient modes of transportation refer to methods that significantly reduce energy consumption and emissions compared to traditional fossil fuel-dependent systems. Historically, the internal combustion engine has dominated this sector, fueled primarily by petroleum, leading to substantial energy demands worldwide. However, a growing awareness of environmental impacts and the depletion of fossil fuel reserves is prompting a transition toward more sustainable alternatives. Various modes of transport exhibit differing energy efficiencies; for instance, maritime transport is notably energy-efficient for cargo, while road transportation remains the largest consumer of energy in both developed and developing nations.
Electric vehicles, hydrogen fuel cells, and hybrid technologies are increasingly recognized as part of the solution, although challenges persist, such as long recharge times for electric vehicles and the complexities of hydrogen fuel production and storage. Additionally, innovations in battery technology, like sodium-ion batteries, show promise for enhancing energy efficiency in the coming years. As transportation evolves, it is likely to shape global production and distribution practices, steering them towards more localized and environmentally conscious frameworks. This shift not only addresses energy consumption concerns but also reflects broader societal movements towards sustainability and reduced carbon footprints.
Energy-efficient modes of transportation
Summary: Beginning from the time the internal combustion engine was invented, fossil fuels have been dominant sources of energy for the transportation sector. However, there is an emerging shift toward more energy-efficient modes to create multiplying effects in energy efficiency.
Industrial Development and the Demand for Fuel
Industrial development places huge demands on fossil fuels. In the twentieth century, the invention and commercial development of the internal combustion engine, notably for application to transportation, made possible the efficient mobility of people, freight, and information, which in turn stimulated the development of trade globally. With globalization, transportation has accounted for a mounting share of the total energy used for implementing, operating, and maintaining the international range and scope of human activities.
There is a strong correlation between energy consumption and level of economic development. In developed countries, transportation accounts for between 20 and 25 percent of the total energy being consumed. The utility conferred by additional mobility, notably the better exploitation of comparative advantages, has so far compensated for the growing amount of energy spent in supporting it. By the beginning of the twenty-first century, the transition had reached a stage where fossil fuels, prominently petroleum, were becoming dominant. Out of the world’s power production of 29,925 terawatt hours in 2023, the contribution from fossil fuels was about 17,903 terawatt hours. Nearly 60 percent of electricity was produced using fossil fuels, while almost 40 percent was generated using clean energy sources.
Transportation and Energy Consumption
A dominant trend that emerged in the 1950s concerns the growing contribution of transportation in the overall consumption of developed countries. In 2023, global energy consumption was 183,230 terawatt-hours. Transportation accounts for about 30 percent of global energy demand and for more than 62 percent of all the oil used annually. In 2023, the transport sector relied on oil fuels for more than 90 percent of its final energy. Transport emissions increased annually at a rate of 1.7 percent from 1990 to 2022. It should also be noted that the impacts of transport on energy utilization are many, including many that are necessary for the provision of transport facilities.
Modal Variations in Energy Consumption
Different modes of transportation involve different levels of consumption. Land transportation accounts for the majority of global energy consumption. In developing countries, road transportation alone is consuming, on average, 85 percent of the total energy used by the transport sector. Road transportation is almost the only mode responsible for additional energy demands over the last 25 years. However, trends within the land transportation sector are not uniform. Rail transport, for example, accounted for only 3 percent of worldwide transport energy demand in 2021, while aviation accounted for 8 percent, maritime transport 11 percent, and road transport 78 percent..
Maritime transportation accounts for 90 percent of cross-border global trade on a volume basis. The nature of water transport and the economies of scale it offers make it the most energy-efficient mode of transportation.
Air transportation plays an integral role in the globalization of transportation networks. Generally, the aviation industry accounts for 8 percent of the transportation energy consumed. Air transport has high energy consumption levels that are in line with its high speeds. Fuel is the second most important line item in the budget of the air transport industry, accounting for between 13 and 20 percent of total expenditures, or a daily consumption of about 1.2 million barrels of oil.
In addition to considering energy consumption for transport from the perspective of land, sea, and air modes of transport, one can consider energy consumption for passenger or freight transport. Passenger transportation accounts for 60 to 70 percent of energy consumption. Private automobiles and other personal vehicles are the dominant modes under this subcategory but have poor energy efficiency, although this performance has seen significant improvements since the 1970s—mainly as a result of higher energy prices, environmental regulations, and the demand for energy-efficient vehicles (hybrids and electric vehicles) that these conditions have encouraged. There is, however, a stronger correlation between rising income levels, automobile ownership, and distance traveled by a vehicle. For example, the United States has one of the highest levels of car ownership in the world, with one car for every two Americans. In 2022, 37 percent of US households had two vehicles, and more than 22 percent had at least three. More than 91 percent of households had at least one vehicle.
Freight transportation constitutes rail and maritime shipping, which are the two most energy-efficient modes of transportation. Furthermore, coastal and inland waterways provide energy-efficient methods of transporting cargoes and passengers. Statistical evidence shows that a towboat with a typical 15 barges in tow is moving the equivalent of 225 railcar loads, which is the equivalent of about 870 truckloads. The justification for favoring coastal and inland navigation is based on the lower energy utilization rates of shipping and the overall smaller externalities linked to water transportation. For instance, the US Marine Transportation System National Advisory Council has measured the distance that 1 ton of cargo can be moved with 3.785 liters of fuel. A towboat operating on an inland waterway can transport 1 ton of barge cargo 532 miles (857 kilometers). The same amount of fuel can be used to move 1 ton of rail cargo 209 miles (337 kilometers) or 1 ton of highway cargo 60 miles (98 kilometers).
Petroleum and
With the exception of railways using electric power, 91 percent of the world’s transportation was dependent upon petroleum products in 2022. The growth in the demand for more transportation is the main reason for increasing petroleum demand; the use of petroleum for other economic operations has been relatively stable. There is some variation regarding the type and quality of petroleum-derived fuel in use; for example, air transportation requires a specialized fuel together with additives, whereas maritime transportation depends on low-quality bunker fuel. Assuming that all other variables remain constant, the lowest-cost energy source will always be sought.
The supremacy of petroleum-derived fuels is due to the relative simplicity of storing them as well as their energy efficiency when used in internal combustion engine vehicles. Other fossil fuels (such as natural gas, propane, and methanol) can be used as transportation fuels, but they require a more complicated energy storage system. However, the critical issue regarding large-scale uses of fuels other than petroleum is the high capital investment required to establish or expand distribution facilities, which are already in place for conventional fossil fuels. Nonetheless, shrinking oil reserves, rising petroleum costs, and environmental concerns related to reducing harmful pollutants and greenhouse gas emissions are focusing attention on alternative fuel sources and technologies.
Biogas, for example, is a noncrude-oil category comprising ethanol, methanol, and biodiesel, which can be produced from the fermentation of certain crops (corn, sugarcane, sugar beets, wheat, and some nonfood crops such as jatropha) or waste from wood. However, the production of biogas necessitates large harvesting areas that may compete with other land uses. It is estimated that one hectare of wheat produces less than or the equivalent of 264 gallons (1,000 liters) of transportation fuel per year, which is equivalent to the amount of fuel consumed by one passenger car traveling 6,213 miles (10,000 kilometers) annually. This limit is based on the capacity of plants to absorb solar energy and transform it into chemical energy through photosynthesis. The low productivity of biomass therefore cannot meet the transportation sector’s energy demand. For instance, in 2007, the US government proposed a reduction in oil consumption by 20 percent and a shift to ethanol. The United States produced nearly 16 billion gallons of ethanol in 2023. Since the production of ethanol is an energy-intensive process, 1 thermal unit of ethanol requires the combustion of 0.76 unit of coal, natural gas, or petroleum.
Hydrogen is often mentioned as the future global energy resource. The steps in using hydrogen as a transportation fuel involve producing hydrogen by extracting it from hydrocarbons or by electrolysis of water; conserving or compressing hydrogen into liquid form; storing it on-board the vehicle using it as fuel; and using fuel cells to produce electric energy on demand from the hydrogen to propel a motor vehicle. From the perspective of efficiency, hydrogen fuel cells are twice as efficient as gasoline and generate almost no pollutants. However, hydrogen poses some significant challenges, ranging from the costly establishment of hydrogen plants to potentially dangerous explosions. First, a great amount of energy is required for the production, transfer, and storage processes involved with this fuel source. Second, hydrogen manufacturing requires electricity production. Third, a hydrogen-powered vehicle needs two to four times more energy for operation than does an electric car, rendering hydrogen-fueled vehicles cost-ineffective. Finally, hydrogen has a minimal energy density and requires very low-temperature and high-pressure storage tanks, adding weight and volume to a vehicle and thus increasing its need for fuel.
Although the infrastructure was still in its infancy in the mid 2020s, California was in the lead in the United States in fueling vehicles that rely on hydrogen. Light-duty fuel cell electric vehicles (FCEVs) were in limited use in the state and around the world. Buses, heavy-duty trucks, and marine vessels were also expected to rely on hydrogen.
Sodium-ion batteries hold promise. The technology has advanced rapidly in the 2020s, with the first commercially available electric car with this type battery produced in 2023. Experts predicted sodium-ion batteries would become more widely available by 2030.
Other options were being explored for ships and aircraft. Wind propulsion and assistance held promise for watercraft. Aircraft developments to reduce fuel burn by at least 20 percent included experiments with ultra-high-bypass ratio jet engines and designs such as blended wing-body aircraft.
It therefore appears likely that transportation will shift toward more energy-efficient modes as well as integrated technologies to create multiplying effects in energy efficiency. While globalization has in large part been driven by cheaper and more efficient transportation systems running on fossil fuels, the new relationships between transport and energy are likely to streamline the global structure of production and distribution toward regionalization.
Bibliography
Davis, S. C., and R. G. Boundy. Transportation Energy Data Book. 40th ed. Washington, DC: U.S. Department of Energy, 2023. tedb.ornl.gov/
"Electricity Generation Worldwide from 1990 to 2023." Statista, 2024, www.statista.com/statistics/270281/electricity-generation-worldwide/. Accessed 26 Aug. 2024.
"Energy for Transportation." Stanford University, 2023, nderstand-energy.stanford.edu/energy-services/energy-transportation. Accessed 26 Aug. 2024.
Greene, D. L. “Uncertainty, Loss, Aversion, and Markets for Energy Efficiency.” Energy Economics 33, no. 4 (July 2011).
Greene, D. L., K. G. Duleep, and Girish Upreti. Status and Outlook for the U.S. Non-automotive Fuel Cell Industry: Impact of Government Policies and Assessment of Future Opportunities. ORNL/TM-2011/101. Oak Ridge, TN: Oak Ridge National Laboratory, 2011.
"Hydrogen Basics." Alternative Fuels Data Center, afdc.energy.gov/fuels/hydrogen-basics. Accessed 6 Aug. 2024.
"Renewables in Energy Demand." Renewables Now, 2023, www.ren21.net/gsr-2023/modules/energy‗demand/03‗transport‗in‗focus/. Accessed 26 Aug. 2024.
Ritchie, Hannah, Pablo Rosado, and Max Roser. "Energy Production and Consumption." Our World in Data, Jan. 2024, ourworldindata.org/energy-production-consumption. Accessed 26 Aug. 2024.
"Transport." International Energy Agency, 11 July 2023, www.iea.org/energy-system/transport. Accessed 26 Aug. 2024.
US Department of Energy. “Alternative Fuels Data Center.” afdc.energy.gov/.