Hydrogen Fuel Cells Reduce CO2 Emissions
Electrifying Commercial Vehicles with Hydrogen Fuel Cells
Shipping and seaport infrastructure are significant sources of greenhouse gas (GHG) emissions. According to the International Maritime Organization, maritime transport creates over 900 million tons of CO2 annually. Global economies rely on shipping to get their products to the consumer, with up to 90% of all foreign goods flowing through ports on container ships, but the toll on the environment is substantial. And those living near busy seaports are exposed to dangerous levels of air pollution caused by emissions from diesel engines on the commercial vehicles at the port.
For example, large industrial vehicles called container handlers load and unload the containers from the container ships. Each container handler emits up to 144 tons of CO2 per year, and a large port can have hundreds of these machines on site. Swapping the diesel engine in just one container handler for a green alternative would have the same effect as removing 32 gas-powered passenger cars from our roads.
From passenger cars to long-haul trucks, locomotives, and heavy equipment, internal combustion engines (ICEs) are being replaced with greener alternatives. Battery-powered electric vehicles have captured much of the spotlight, with an increasing number of options available to consumers in both car models and charging locations. But at ports, the ICEs are diesel engines in heavy-duty industrial vehicles such as yard trucks, forklifts, and container handlers. Batteries and the required charging infrastructure don’t work for many of these operations.
That’s where fuel cells can help.
Fuel cells are well-suited for locations with heavy equipment that must run for long shifts with minimal downtime for refueling. Refilling a hydrogen fuel cell takes about the same amount of time as it does to fill a similar-sized gas tank, whereas recharging a battery for heavy-duty e-vehicles would take hours. Fuel cells offer the power density and range needed for the vehicle to make it through an 8-hour shift. One company focusing on fuel cell technology for commercial vehicles is Nuvera.
“Fuel cells are better than batteries whenever long range is required, or when battery charging takes too long—making them good for boats, planes, trucks, buses, and emergency response vehicles,” says Gus Block, a founding employee and director of Nuvera Fuel Cells.
“They’re also needed when batteries are too large to fit on a vehicle or so heavy that they’d compromise payload,” says Block. “For example, the battery required for the electric container handler would be the size of a small elephant.”
An Electric Alternative That Doesn’t Require Recharging
A fuel cell produces no exhaust other than heat and water. With no moving parts, its design is simple in principle: a membrane is sandwiched between two electrodes. When the hydrogen fuel meets the anode, it is split into a proton and an electron. The proton passes through the membrane to the cathode, where it meets oxygen. The electron takes a longer route between electrodes, traveling through an electrical circuit. The flow of electrons creates the power for the motor. At the cathode, the protons, electrons, and oxygen combine to form water.
Using modeling and real-time simulation enables Nuvera’s engineers to iterate on their design quickly and allows for experimentation without putting a real engine at risk.
The science is simple, but perfecting the recipe for a high-performance power source is hard. Many factors govern the multiple reactions inside a fuel cell, and a software control system must account for them all to squeeze the most power and efficiency out of the device. The control system makes constant corrections based on feedback.
“One of the greatest design challenges is maintaining proper hydration to the cells,” says Pierre-François Quet, Nuvera’s chief engineer. “Not enough water and protons don’t pass through; too much and the cells flood.”
Their system manages hydration by changing the coolant temperature and by manipulating airflow to increase or decrease evaporation. To design the software that controls their fuel cell engine—which typically includes hundreds of fuel cells stacked together with coolant flowing between them, plus a coolant pump and an air compressor—Nuvera uses MATLAB® and Simulink®. A plant model of the fuel cell engine—which comprises equations governing the electrical and chemical reactions and the temperatures and pressures of water and gases and coolant—is also implemented in Simulink, Quet says. With this simulation in place, Nuvera writes algorithms to refine things like coolant flow in order to eke out the best performance. Once the algorithm is finalized, Simulink translates it into code that will run on a processor embedded in the actual fuel cell engine.
The control algorithms also account for many operating conditions. In simulation, Nuvera tests the system in low and high ambient temperatures, and in low- and high-humidity environments.
In order to experiment with their algorithms in a more realistic setting, Nuvera does hardware-in-the-loop testing: They load their engine model onto a custom computer made by Speedgoat that is tailored to have the same inputs and outputs as the physical engine, and can simulate its operation in real time. The same embedded computer that runs the fuel cell engine is connected to the Speedgoat box and is programmed from C code generated from Simulink.
This setup adds rigor while enabling Nuvera’s engineers to iterate on their design quickly. It also allows for experimentation without putting a real engine at risk.
A Different Kind of Hybrid
Virtually all fuel cell vehicles are electrically hybridized, powered by both fuel cells and batteries. In some cases, fuel cells provide a trickle charge to keep the battery charged, while in other configurations both the fuel cell and battery power the motors through an electrical bus. Batteries are also employed to accept a vehicle’s regenerated power, such as when a forklift brakes or lowers a load.
Quet’s team first had to build a model of the lithium-ion battery in Simulink, based on data provided by the manufacturer and collected in-house. They also wrote algorithms that could estimate the battery’s state of charge based on things they could measure—its voltage and current. They then used Simulink to program the control algorithm. The system needs to maintain an ideal level of battery charge, so there’s always enough energy for peak load and enough capacity to reabsorb energy. The Nuvera team also designed the optimal size for various system components by testing the algorithms in a range of simulated forklift and load scenarios.
Best of Both Worlds
Fuel cells share strengths with both batteries and ICEs. Like batteries, they’re scalable and quiet, and they don’t produce harmful emissions. But fuel cell vehicles also offer the long range and quick refueling time found in gasoline and diesel-powered ICE vehicles. Hydrogen can be stored at pressure in a fuel tank that enables it to contain much more energy than a battery of the same dimensions, so instead of stopping to recharge or swap out a battery, you can operate the vehicle for as long or longer than a battery-powered equivalent and spend a few minutes filling the fuel tank.
One use of Nuvera’s fuel cell engines is in forklifts made by their parent company, Hyster-Yale Group. Nuvera has also integrated two of its E-45 fuel cell engines into a Hyster® container handler that will be used at the Port of Los Angeles, similar to the model shown in the photograph. By replacing the diesel engine with a fuel cell–powered electric drivetrain in this vehicle alone, 128 metric tons of CO2 can be avoided annually. Diesel engines in commercial and industrial vehicles are a source of carbon emissions and criteria pollutants that diminish air quality. Nuvera works with other manufacturers to use fuel cells to electrify buses, trains, and specialty vehicles to help reduce their emissions significantly.
Fuel cells are scalable and quiet, don’t produce harmful emissions, and offer the long range and the short downtime found in gasoline and diesel-powered ICE vehicles.
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