The term “hydrogen car” might sound straightforward, but it actually encompasses a fascinating duality in automotive technology. When we talk about hydrogen cars, we’re not just looking at one single type of vehicle. Interestingly, hydrogen can power cars in fundamentally different ways, leading to two distinct categories: hydrogen fuel cell vehicles and hydrogen combustion vehicles. Understanding these different approaches is crucial to grasping the potential and diversity within the realm of hydrogen-powered transportation.
Hydrogen Fuel Cell Vehicles: Electric Cars Powered by Hydrogen
Hydrogen fuel cell cars, often abbreviated as FCEVs (Fuel Cell Electric Vehicles), represent a sophisticated and increasingly viable approach to zero-emission driving. While they might seem like a recent innovation, the core technology behind fuel cells dates back to the 19th century. The principle of generating electricity from hydrogen and oxygen was discovered in 1838, and by the mid-20th century, fuel cells were powering spacecraft like the Gemini and Apollo missions, providing electricity and drinking water for astronauts.
The appeal of hydrogen lies in its abundance and potential for sustainable production. Hydrogen is the most plentiful element in the universe and can be sourced from various domestic resources, with growing efforts towards “decarbonized hydrogen” – hydrogen produced with minimal environmental impact. The U.S. Hydrogen Council, for example, aims for widespread adoption of decarbonized hydrogen in transportation by 2030.
Functionally, a hydrogen fuel-cell car is essentially an electric car, but it generates its electricity onboard instead of relying solely on a large battery charged from an external source. Refueling a hydrogen car is remarkably similar to refueling a gasoline car, taking around five minutes to fill the tank with compressed hydrogen gas.
This hydrogen gas is then fed into the fuel cell system, where it reacts with oxygen from the air. This electrochemical reaction within the fuel cell stack produces electricity and water. The only emission from a hydrogen fuel cell car is pure water, typically expelled through a vent pipe. The electricity generated by the fuel cell, supplemented by energy recovered through regenerative braking, is stored in a small lithium-ion battery. This electricity then powers an electric motor, which propels the vehicle. Cars like the Toyota Mirai house the electric motor and fuel cell stack in the rear, demonstrating the compact nature and flexible packaging of these components.
A key advantage of hydrogen fuel cell technology compared to battery-electric vehicles (BEVs) is the potential for a significantly smaller battery pack. This reduced battery size contributes to a lighter overall vehicle weight and improved efficiency. Hydrogen fuel cell cars offer a compelling combination of electric driving with the refueling convenience of traditional gasoline vehicles, making them responsive, agile, and capable of achieving impressive driving ranges without the lengthy charging times associated with large battery EVs.
Hydrogen Combustion Vehicles: Internal Combustion Engines Running on Hydrogen
While fuel cells represent a more futuristic approach, hydrogen can also be utilized in a more familiar way – by burning it in an internal combustion engine. Toyota, a major proponent of hydrogen technology, has been actively exploring hydrogen combustion as another viable pathway for hydrogen vehicles.
Unlike hydrogen fuel cell vehicles that use hydrogen to generate electricity for an electric motor, hydrogen combustion vehicles utilize a modified internal combustion engine (ICE) that burns hydrogen instead of gasoline. In essence, a hydrogen combustion engine operates much like a traditional gasoline engine in terms of sound and driving feel, but with a crucial difference: it produces zero harmful tailpipe emissions. Similar to fuel cell cars, the primary emission is water vapor.
The appeal of hydrogen combustion lies in its potential for faster market entry. Automakers can leverage existing engine manufacturing infrastructure and engineering expertise to adapt current internal combustion engines to run on hydrogen. Furthermore, the refueling infrastructure could be adapted from existing gasoline stations, potentially easing the transition to hydrogen fuel distribution. Hydrogen can be stored onboard in either gaseous or liquid form.
From a driver’s perspective, hydrogen combustion cars offer a driving experience that will feel immediately familiar to anyone accustomed to gasoline cars. They feature an engine, gears, and the characteristic engine sound. Hydrogen burns more rapidly than gasoline, which can result in highly responsive and engaging powertrain performance.
However, hydrogen combustion engines also come with certain drawbacks. They are mechanically more complex than the relatively simpler hydrogen fuel cell systems, which primarily consist of an electric motor and fuel cell stack. The presence of numerous moving parts in a combustion engine, similar to gasoline cars, suggests potentially higher maintenance requirements over the long term.
Furthermore, hydrogen combustion cars share some of the infrastructure and cost challenges associated with hydrogen fuel cell vehicles, including the need for expensive, high-pressure hydrogen storage tanks and the limited availability of hydrogen refueling stations across much of the United States.
Despite these challenges, hydrogen combustion technology is progressing rapidly. Toyota and other manufacturers are actively developing and refining hydrogen combustion engines, focusing on enhancing power, performance, and reliability. Toyota recently showcased a Corolla Cross prototype powered by liquefied hydrogen, which improves fuel storage density and extends driving range. Brands like Toyota, Hyundai, Renault, and BMW are investing significantly in hydrogen combustion research and development. Toyota’s hydrogen combustion racing program head, Koji Sato, has indicated substantial progress towards commercialization, integrating hydrogen combustion into the development cycle for both Toyota and Lexus vehicles. BMW’s exploration of hydrogen combustion in high-performance vehicles, dating back almost two decades, further underscores the ongoing interest and potential of this technology.
Looking Ahead: A Diversified Approach to Zero-Emission Mobility
As the automotive industry transitions towards a zero-emission future, battery electric vehicles are poised to become a dominant mode of transportation. However, a multi-faceted approach is likely necessary to achieve comprehensive carbon neutrality. Hydrogen power, with its rapid refueling capabilities, is expected to play a vital role, particularly in sectors like long-haul transportation for both goods and passengers.
While the majority of global automakers are heavily investing in all-electric vehicle development, companies like Toyota are adopting a more diversified strategy, recognizing the potential of various zero-emission technologies for different applications and customer needs. As the shift to zero-emission driving is still in its early stages, a range of solutions will be needed to cater to diverse customer requirements and use cases. Automakers offering a variety of options, including both hydrogen fuel cell and hydrogen combustion vehicles, will be best positioned to meet the evolving demands of the market and contribute to a truly sustainable transportation ecosystem.
