Hydrogen Cars (FCEVs) are coming, what to expect?
It is only a matter of time FCEVs will be driving on roads around us. Although EVs are more visible now having a big head-start on FCEVs, FCEVs are catching up.
FCEV Ecosystem is Developing Fast
There are several reasons for that:
· The fuel — Hydrogen — is rapidly becoming cheaper
· New Hydrogen refueling stations are popping up in strategic locations.
· Several existing fuel stations are being re-purposed so they can dispense Hydrogen
· Most established ICE vehicle makers are launching Hydrogen FCEV models.
· Even, new makers of Hydrogen FCEV are entering the market
· Last but not least, Government support is springing forth in many countries as subsidies are announced for FCEVs (as they did for EVs) to phase out fossil-fuel based ICE vehicles in order to abide by their COP26 commitments[1]
In summary the Hydrogen FCEV eco-system is now developing all-round and this sets the scene for bigger uptake of FCEVs in the months and years to follow
All of these developments are not lost on the public. Drivers are now actively considering the switch from their current ICE (IC engine based) vehicles.
Till sometime ago a driver had only one real option, the EV, still considered by many as the only default option for non-fossil-fuel-based vehicles, but now with the availability of FCEVs the choice is twofold — EV or FCEV[2]
FCEVs on the Market
Starting with the pioneer, Toyota Mirai (and now LandCruiser and HiLux), closely followed by BMW (iX5), Chevrolet (Colorado), Honda (Clarity), Hyundai (Nexos), Kia (Carnival), Mercedes-Benz (Trucks), Range Rover (Land Rover Defender) and Tata (Starbus) plus new entrants H2X (Warrego ute), Ineos (Hypercar) and Nikola (Trucks) to name a few, the list is impressive and growing for the number of FCEVs hitting the market already or soon
In this article we examine what a driver will expect to notice as the difference from their erstwhile ICE vehicle as they switch to an FCEV
FCEVs are different from ICE vehicles
Although there are many similarities between an FCEV and an ICE car, we will focus on the key points of differences:
· Fuel — An FCEV uses Hydrogen as a fuel, so the entire fuel-related system including fuel loading, storage and usage is different from the traditional fuel system that uses petrol (gasoline) or diesel
· Fueling Process — An FCEV requires compressed Hydrogen gas to be filled into its tanks. For this a driver will pull into a Hydrogen Refueling Station (HRS), similar to a service station today, and approach the appropriate pump marked H70 or H35 for the desired car tank pressure respectively of 70 MPa (~700 bar) for light vehicles (cars) and 35 MPa for heavy vehicles (trucks, etc.)[3].
Note: The actual pressure at the dispensing pump is a lot higher than the vehicle tank pressure, being 90 MPa and 50 MPa for M70 and M35 respectively. This is required to dispatch Hydrogen else there will be zero flow if both source and tank pressures are same
One interesting difference in the fueling experience for an FCEV driver will be they will feel the area around the pump quite cold! This will be evident from the condensation that will be visible on the spigot and the pump surfaces during filling up
This is due to deliberate pre-cooling done down to between -20º to -40º C to counter the temperature rise that accompanies as Hydrogen expands from 90 MPa to 70 MPa. Yes, Hydrogen warms up as it expands! Hydrogen is the only gas (and Helium) that warm when expanding (Joule-Thomson coefficient is negative)[5], so to counter the rise in temperature and to achieve the desired density to fill into the car’s tank it is necessary to cool the pump
· Fueling time — For a like-for-like comparison (eg Mirai-to-Camry), filling up an FCEV takes about the same time as an ICE vehicle. To fill up the 5.6 kg on Toyota Mirai (~ 141 litres @ 70 MPa) is 3–5 minutes[1]. It is noteworthy that Department of Energy, USA has a target of 10 kg/min standard for dispensing of compressed Hydrogen at American Hydrogen Refueling Stations (HRS), which would suggest that when implemented would drastically reduce filling time even further![6]
No! It won’t. And interestingly it has nothing to do with the pump or HRS design or implementation. The filling time bottleneck is due to the properties of the vehicle Hydrogen tank. The material used to construct the tank — specialized carbon fiber material with polymer lining — does not take it well if the pressure varies steeply in a short period of time[7]
So in order that tank is not damaged, the fill rate is regulated so the fill time for a 5 kg tank is 3.5 minutes or ~1.5 kg/min
· Fuel tank and mileage — Hydrogen fuel is stored on-board in tanks compressed to high pressures of 70 MPa in tanks that are either Type III (composite tank made of glass fiber with metal liner) or Type IV (composite tank made of carbon fiber with polymer liner)[8]
A current model FCEV on the market is averaging between 70–75 miles (110–118 kms) per kg of Hydrogen[9]. With 5 kg full tank capacity this is expected to deliver 350–425 miles per tank (550–590 kms)
In the latest 2021 Toyota Mirai there are 3 cylindrical tanks totaling 5.6kg capacity (141 ltrs @ 700 bar).
· Powertrain — Here FCEV is significantly different from an ICE vehicle. FCEV powertrain is entirely electric, whereas ICE powertrain is almost entirely mechanical. FCEV power flow sequence is HydrogenàFuel Cellàelectricityàmotoràwheels, whereas the ICE sequence is petrolàengineàtransmissionàdrivetrainàwheels
Thus a large number of mechanical parts involved in the ICE powertrain eg. differentials, gears, etc. are not required in an FCEV, hence the powertrain in an FCEV is a lot simpler and cleaner (single-speed direct-drive transmission and differential)
· Car starting — FCEV does not require a battery start. The FCEV generates power as soon as Hydrogen is fed into the FC
For example, when the driver presses the “start” button in the Mirai, the battery powers up the primary motor, which then begins to turn the vehicle’s wheels and propel the car forward.
This is in contrast to an ICE where battery is required to power the starter motor that cranks the engine.
· Vehicle speed control — In an FCEV, speed and torque is controlled by the speed of rotation of the motor, which is controlled by varying the frequency of the AC current to the motor, with the power control unit controlling the energy supplied by the FC and the traction battery. The optimal range for the torque is between 0 and 20,000 RPM
This is in stark contrast to an ICE vehicle where a series of gears, differential, etc. are controlled by the throttle. The optimal torque at a range that is lot smaller between 2000 and 8000[11].
· Battery — Even as an FCEV does not require a starter battery, there does exist a battery on an FCEV. This is to power the on-board auxiliary systems eg. infotainment system, lights, etc when the car is not moving as well as to supply additional power in certain situations such as when car is accelerating and driving uphill
For instance, the battery on Toyota Mirai is 1.24 kWh nickel-metal hydride (Ni-MH)
· Electrical system — The primary driver of an FCEV is electric power and the electrical system plays an important role. Electricity is produced in the Fuel Cell with Hydrogen from the tank combined with oxygen drawn from the atmosphere. This reaction also produces water vapor as a by-product. Electricity produced drives the motor that powers the powertrain
It is not necessary all electricity is consumed in driving. Any spare electricity not consumed during running is stored in the on-board battery. Power from this battery is used to augment the FC power when required, such as when accelerating or driving uphill FCEVs also have regenerative braking, which captures energy when the car slows down or brakes and puts this energy into the battery, similar to a hybrid vehicle.
· Regenerative braking system — FCEVs also have a regenerative braking system like an EV and ICE vehicle. It is integrated with the FC stack and electric motor. This allows more energy to be recovered through regenerative braking than in ICE vehicles, which rely on hydraulic brakes as they lose heat and energy to friction.
The electricity spent in driving is regenerated through this process s the motor turns into a generator upon triggering from the brake. The electricity thus generated is stored in the FCEV battery.
Since FCEVs use regenerative braking to slow down the vehicle and recover energy, the hydraulic braking system is used less frequently than in an ICE vehicle. This means that the brake pads in an FCEV may experience less wear and tear over time than in an ICE vehicle, prolonging the life of brake pads’ compared to an ICE vehicle
· Cooling system — FCEV cooling system is smarter and smaller than the one in an ICE vehicle. In an ICE vehicle the cooling system has a single purpose — to prevent engine overheating — so it works to maintain a constant temperature range for the engine by absorbing the heat and transferring to the radiator. In an FCEV, its role is to maintain an optimal operating temperature range for both the Fuel Cell so that the electrochemical reaction inside the FC can proceed optimally and in a constant temperature range for the motor between 80–120º C. This way both FC and motor can work properly and avoid damage to the FC stack and motor components respectively
A radiator is present in both cooling systems but the overall size of cooling system in FCEV is much smaller as heat generated in the FC is lot less compared to combustion heat produced in an ICE vehicle
· Exhaust system — The entire philosophy of why FCEV in the first place, is observed here! The exhaust from an FCEV is ZERO EMISSIONS — just pure water or water vapor! As opposed to this in an ICE vehicle there are environmentally harmful by-products of fossil-fuel combustion — CO, CO2, NOx, soot and other particulate matter
As a result, the FCEV exhaust system is a lot simpler and cleaner. In fact, many drivers have reported drinking water from FCEV exhaust (Refer Can one drink water from FCEV?)[12]
· Monitoring and On-board sensors — There are specific parameters that are unique to FCEVs and monitoring those will be useful for vehicle’s performance and safety of vehicle and passengers:
o Hydrogen sensor: Dealing with high pressure tanks, any leakage needs to be noted urgently. This sensor detects the presence of hydrogen in the air inside and outside of the vehicle. It helps to ensure safety and prevent accidents related to hydrogen leakage.
o Oxygen sensor: This sensor monitors the oxygen content in the air inside and outside of the vehicle. It helps to optimize the air/fuel ratio and ensure efficient operation of the fuel cell stack.
o Temperature sensors: FCEVs typically have multiple temperature sensors that monitor the temperature of various components such as the fuel cell stack, electric motor, battery pack, and hydrogen storage tank. They help to maintain optimal operating temperature and prevent overheating.
· Maintenance — FCEV has similar routine maintenance requirements to ICE vehicles for all systems that are common to both FCEVs and ICEs such as Suspension and Steering Systems, Braking System, Safety Features (eg. airbags, seatbelts, and anti-lock braking systems (ABS)) are common to both types
For other systems, the FCEV differs in maintenance schedule for following:
o Fuel System Maintenance
o Battery Maintenance
o Cooling System Maintenance
· Service intervals & Maintenance frequency
o FCEV average annual maintenance cost is lower than ICE vehicle according to a report by Consumer Reports[13]. For FCEVs it is $437, for ICE vehicles it is $792. This is based on the estimated maintenance cost for a Toyota Mirai (an FCEV) and a Toyota Camry (an ICE vehicle)
o With far fewer moving parts expected breakdown and maintenance of FCEVs is much lower than a comparable ICE vehicle. The typical interval for these checks is about every 10,000 to 15,000 miles (16,000 to 24,000 kms) compared to an ICE requiring inspection every 5,000 to 10,000 miles (8,000 to 16,000 kms)
Further Reading
· Toyota FCEV — Hydrogen Refuelling Stations | Mirai | Toyota AU
· BMW FCEV — Hydrogen fuel cell cars: what you need to know | BMW.com
· Honda FCEV — 2021 Honda Clarity Fuel Cell — Hydrogen-Powered Car | Honda
· Hyundai FCEV — Hyundai NEXO | Hyundai Motor Europe
References
[1] Which countries are backing the hydrogen economy? (h2bulletin.com) — At least 34 countries are backing the Hydrogen economy with FCEVs set to operate in these countries
[2] Other variants like Hybrid EV or Plug-in Hybrid EVs are essentially ICE plus EV combinations in the interim, with compromised performance when not running on battery, and are not expected to last long as performance of EVs and FCEVs continuously improves
[3] 70 MPa is ~700 bar or 10,150 psi, 35 MPa is ~350 bar or 5,000 psi
[4] Hydrogen Refuelling Stations | Mirai | Toyota AU
[5] Joule–Thomson effect — Wikipedia
[6] Hydrogen Refuelling Stations | Mirai | Toyota AU
[7] Hydrogen Delivery | Department of Energy
[9] A Guide to Hydrogen Pressure Vessels — Antala Ltd.
[10] Compare Fuel Cell Vehicles (fueleconomy.gov)
[11] ICE Vehicles vs. Electric Vehicles | Elasto Proxy
[12] Can one drink water from FCEV?
[13] What is the Maintenance Cost for a Fuel Cell Car?” The report was published on September 13, 2021 https://www.consumerreports.org/car-maintenance/what-is-the-maintenance-cost-for-a-fuel-cell-car-a4485704828/
