As we already know, the depleting deposits of fossil fuels and the adverse effect of their combustion on the environment have propelled automakers to turn to alternate sources of energy to drive vehicles. These sources need to be diverse and sustainable energy solutions, such as battery electric vehicles (BEVs) and fuel cell electric vehicles (FCEVs).
Although the automotive industry has already started looking at sustainable solutions, there is a lot of debate regarding the prioritization of BEVs over FCEVs, particularly because of the limited available reserves of lithium, which is a major component in lithium-ion batteries. Many researchers are hence advocating the use of fuel cells, which convert the chemical reaction of a redox reaction into electricity. However, the behaviour of a fuel cell in an automotive battery is still in the R&D phase, which is why most automakers are still hesitant about using it in production vehicles. This article aims to address these concerns about this BEV-FCEV debate.
Source: https://www.fuelcellstore.com/blog-section/what-is-a-fuel-cell
The Interplay between BEVs and FCEVs
One of the popular misconceptions in this particular debate is that lithium-ion batteries and fuel cells are competing technologies. It is important to understand that batteries are here to stay in the industry for a long time into the future now as one of the primary energy sources. What lithium-ion cells and fuel cells do is present diverse options for solving the efficiency, emissions and sustainability problems. Both these chemistries aim to enhance the solutions for the electrification question that the industry is currently facing.
Batteries are forecasted to be the central piece of the electrified solution in the future, and fuel cells will aim at enhancing them rather than replacing them. This will be essential in addressing the issue of recharging time for batteries, especially for heavy-duty transport.
Source: https://www.automotiveworld.com/articles/electric-hd-trucks-when-will-hype-become-a-reality/
Challenges in Today’s Market
The first factor that always comes into question when talking about sustainable mobility is Range, especially when talking about heavy-duty transport. Combustion engine trucks with very high payload capacity normally have a large fuel tank, in the vicinity of 200 to 300 litres (50-80 gallons). This often allows them to drive up to 400 miles (subject to payload) before having to stop for a refuelling break. However, the development of lithium-ion cells, as well as fuel cells, is still at an early stage, and so, none of the solutions has met the range demands of heavy-duty transport yet.
Secondly, a high-capacity battery will most likely be very heavy, which increases the amount of load, which in turn demands more energy. For instance, the weight of the battery in the Hummer EV is anticipated to be equivalent to the Honda Civic. One solution to this vicious cycle is high-energy-density batteries (or fuel cells).
Source: https://www.garrettmotion.com/news/media/garrett-blog/hydrogen-fuel-cells-vs-battery-electrics-why-fuel-cells-are-a-major-contender/
Heavy-duty transport will be an interesting challenge for automakers since there are quite a few tradeoffs that automotive designers have to work with while using Li-ion cells. There is a relatively lower cap on the maximum allowable weights on each axle at the moment, which means designers need to reduce the battery size, thus affecting range. Furthermore, by limiting the payload capacity, there is a decrease in the load that a vehicle can carry per trip, which doesn’t exactly make for viable logistical economics. Finally, there is always going to be the efficiency vs performance tradeoff that automakers have to deal with.
BEVs vs FCEVs
Downtime is one of the factors where FCEVs currently outclass BEVs. The refuelling time for an FCEV is almost as low as an ICEV (internal combustion engine vehicle), thus making it an attractive solution for long-distance drives. For BEVs, the solution to this issue would be the development of megawatt level charging stations. Reducing the charging time also allows designers to reduce the battery size (and hence weight), as it allows drivers to stop as frequently as needed for charging.
Source: https://www.bmw.com/en/innovation/how-hydrogen-fuel-cell-cars-work.html
Another major advantage for FCEVs is that they have the potential to utilize renewable energy solutions on a larger scale and increase the adoption of sustainable power sources faster. They also provide necessary enhancements to the operational and performance gaps found in existing batteries. In general, FCEVs can prove to be more effective than BEVs for a driving style that mainly consists of long-distance travel, such as commercial trucks. Furthermore, the payload-bearing capacity of an FCEV is more than a BEV on account of fuel cell powertrains being significantly lighter, thus allowing engineers to increase the energy capacity without affecting the overall weight by much.
The biggest advantage that a lithium-ion battery has over the fuel cell is the ability to meet the powertrain dynamic demands. There may be many fuel cell configurations being developed right now for dynamic behaviour, however fuel cells are inherently meant for non-dynamic/static behaviour. With researchers in the lithium-ion battery industry working on solid-state cell solutions for mobility, there is hope for better dynamic behaviour from batteries soon.
So, is one better than the other in all cases?
The debate of using BEVs over FCEVs, or vice versa, should be tackled from a different perspective, as it is more a question of which solution is befitting for which transportation needs. BEVs can effectively serve a larger sector in the industry, but their shortcomings can be dealt with by sustainable FCEV solutions.
Lighter powertrains in FCEVs allow for an increase in energy capacity without affecting the overall weight, which in turn can allow for a better range. Fuel cells also exhibit higher payload-bearing capacity and quicker charging (or refuelling time), making it an attractive proposition for heavy-duty and long-distance applications.
The drawback of a fuel cell is that hydrogen is energy-intensive when it comes to production as well as storage, not to mention that the development of fuel cells is still in its early stages, making it quite costly as compared to lithium-ion batteries. Furthermore, lithium-ion batteries exhibit much better dynamic behaviour than fuel cells.
BEVs and FCEVs aren’t two sides of the same coin by any means. Instead, one needs to look at them as two different paths that can be taken to solve the same problem – tackling the challenges of sustainable mobility.
BEV and FCEV Efforts at Dorle Controls
At Dorle Controls, we develop model-based software for fuel cells as well as battery chemistries. On the development side, we are working on SOC estimation algorithms using Kalman filters, cell balancing algorithms, as well as the thermal modelling and management of both these energy sources. Integration of fuel cell controller with the BMS controller on a CAN architecture is in focus, as is the verification and validation of batteries through charging and discharging tests. We can also help you out with rapid control prototyping for battery systems using RaptorDev tools.
To know more about our software development capabilities for battery-specific requirements, write to info@dorleco.com.