If sourced from renewable means, an element such as hydrogen can be a zero-emission, extremely efficient fuel source.
What are fuel cells and how do they work? Cummins provides some answers to our questions:
- What are fuel cells? A fuel cell utilizes the chemical energy of hydrogen, natural gas or other hydrocarbon fuels to generate electricity. Unlike a battery, a fuel cell system does not store energy. Instead, it relies on a constant supply of fuel and oxygen in the same way that an internal combustion engine relies on a constant supply of gasoline or diesel and oxygen. A Proton Exchange Membrane fuel cell (PEM or PEMFC), also known as a hydrogen fuel cell, uses hydrogen exclusively as the fuel. In the case of hydrogen-powered fuel cell electric vehicles (FCEV), hydrogen is typically compressed and stored in tanks that are attached to the vehicle. Fuel cells are used to complement electric batteries as part of an FCEV powertrain, enabling several operating strategies for the user that offer flexibility in choice of energy (hydrogen, battery or an optimized combination) based on price of the desired fuel source – electricity or hydrogen, and tailored to each application.
- How do hydrogen fuel cells work? The basic structure of a fuel cell consists of two electrodes (a negative and a positive) separated by an electrolyte. Each fuel cell is only a few millimeters thick and hundreds of them are stacked together to build a fuel cell stack. The supply of fuel, which is hydrogen in the case of hydrogen fuel cells, comes from a tank attached to the vehicle. The fuel is fed into the anode (the negative electrode) while oxygen from the atmosphere is introduced to the cathode (the positive electrode). Different fuel cell types exist and they each use a different process to create electricity, but for the most part a catalyst is introduced between the electrodes, which causes electrons to travel through an external circuit which is how electricity is created. In FCEV powertrains, the electricity produced from the fuel cell can be used to power an electric motor to produce mechanical power, to power accessories and to charge the high voltage battery packs as needed. In the case of a hydrogen-powered fuel cell, the byproduct of this chemical reaction is water and heat.
- What are the benefits of hydrogen fuel cell technology? Compared to electric batteries, fuel cell powertrains would have a higher energy density and are quicker to refuel, making them more suitable for applications with longer daily ranges that cannot be accomplished by batteries alone. Analyses indicate, for example, that PEM fuel cells could be a viable solution for medium to long haul trucks, while battery only vehicles may be more suitable for short haul vehicles. Currently, the battery capacity needed for the range requirements of long-haul, and the resulting weight from the batteries, is prohibitive for trucks that need to reserve that weight for their load. Because fuel cells have higher energy density and lessen the battery capacity needed, it can create significant improvements in tractor weight while still providing adequate range. And when vehicles do need to refuel, for the near future hydrogen refueling is much quicker compared to recharging batteries despite evolving recharging technologies. Fuel cells also offer great flexibility due to their modular design: fuel cell systems and storage tanks can be tailored to meet the needs of different applications across different markets. Lastly, and very importantly, hydrogen can be sourced from water using a process called electrolysis, which uses electricity to separate a water molecule into hydrogen and oxygen. Thus, fuel cells can be a decarbonized source of energy.
- What are the current challenges to hydrogen fuel cell adoption? Fuel cell technology is very promising, but like battery electric vehicles, there are many factors that influence adoption. Emissions regulations, financial incentives, technology development, infrastructure and total cost of ownership (TCO) will all be key in driving the adoption of fuel cell-powered vehicles. Currently, fuel cell technology is still developing which means there is limited real-world testing and limited investment in infrastructure, like hydrogen fueling stations. Customers are also faced with a higher upfront vehicle cost with payback largely dependent on the price of fuel. Fuel cell electric vehicles do offer flexibility allowing customers the option to refuel with hydrogen or recharge with electricity depending on which provides the best value, but long-term savings on those operating costs will be directly connected to the price of hydrogen. While some experts project hydrogen prices to fall, the initial investment for operators is likely to remain quite high compared to other technologies in the near-term. In addition to financial factors, these systems, as compared to the incumbent fossil fuel solutions are also presently challenged by increased weight, reduced power density, and increased refueling time. While the latter is currently superior to battery charging solutions, it is still a challenge when compared to traditional liquid fuel refill times for similar amounts of fuel energy. The industry continues to work actively to address these challenges. Source