As the global transport sector works to reduce its emissions contribution, electrification has become an important solution. Battery-electric vehicles (BEVs) are well suited to many passenger and urban applications, offering an effective way to reduce emissions where charging infrastructure is available and electricity grids are powered by renewables.
However, not every transport application has the same requirements. For some applications, fuels will continue to play an important role in supporting the transition to a more sustainable transport system. What are these applications, and why is this the case?
Every transport application has different energy requirements. While batteries are an effective solution for many vehicles, they are not always practical where equipment must travel long distances, carry heavy loads, or operate continuously with minimal downtime.
Liquid and gas fuels offer a higher energy density than today's batteries, allowing vehicles to travel further without significantly increasing their weight – and supporting ranges that are otherwise unachievable. They can also be refueled quickly, helping operators maximize the amount of useful work done by a vehicle.
Read more about what's the difference between lifecycle and tailpipe emissions?
Commercial aviation depends on fuels with high energy density to power long-haul flights. The energy density challenge is very significant: jet fuel contains around 12kWh of energy per kg, whereas lithium-ion batteries tend to have just 0.3kWh per kg.
This means it takes 40kg of batteries to store the same energy as 1kg of fuel. Even if we assume half of the fuel cannot be converted into useful work, we’d still need to increase it by a factor of 20. Since fuel accounts for 20-40% of the take-off weight for most commercial airplanes, a 20x increase would mean increasing the airplane’s weight by 400-800%. This would mean increasing lift force by the same amount, which isn’t practically possible.
So, rather than full BEVs, aviation is exploring solutions like range extenders and series hybrids to electrify the most emissions-intensive phases of flight such as take-off and climbing. The industry is also exploring solutions such as Sustainable Aviation Fuels (SAFs), which offer a lower-carbon alternative that can help reduce lifecycle emissions while working within existing aircraft and fueling infrastructure.
Cargo ships transport goods across thousands of miles, requiring continuous power for extended periods at sea. For many vessels, batteries alone are not yet capable of providing the energy needed for these journeys. While not as constrained as aircraft, since the buoyancy of water can offset the weight of extra battery mass, the economics of ultra long-range journeys without any access to charging infrastructure means that it’s generally not efficient to substitute the engines of large ships with batteries.
Instead, alternative fuels such as green ammonia, methanol, and liquefied natural gas (LNG) are being explored as lower-emission solutions for future long-distance maritime transport.
Vehicles that transport goods long distances typically cannot rely solely on battery power at this time
Long-haul trucks and intercity coaches require long driving ranges, high payload capacities, and minimal downtime. Because they’ll often be off-grid during journeys and have high energy requirements owing to their mass, batteries often aren’t practical for any medium- to long-range trips.
So, while BEVs may be suitable for some operations, renewable fuels such as Hydrotreated Vegetable Oil (HVO) and hydrogen are expected to support applications where rapid refueling and operational flexibility are essential.
Agricultural and construction machinery often operates in remote locations where charging infrastructure may be unavailable. These machines also frequently work for extended periods under demanding conditions, making renewable liquid fuels a practical solution while the infrastructure is still developing.
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The transition to lower-emission transport will not rely on a single technology. Different transport applications have different operational requirements, meaning the future of mobility will require a diverse mix of powertrain solutions.
Electrification will play an important role in many sectors, while alternative fuels will continue to support applications where energy density, range, and operational flexibility remain critical.
At Horse Powertrain, we develop powertrain technologies designed to support multiple fuel types and propulsion systems, check them out here.