Design tool for hydrogen fuel-cell vehicles (Toyota Mirai, Hyundai Nexo, Honda CR-V e:FCEV, BMW iX5 Hydrogen). Change vehicle mass, aerodynamics, tank capacity and fuel-cell type to see total power demand, fuel economy, CO₂ emissions and refueling time update in real time.
Parameters
Fuel cell type
Sets the Tank-to-Wheel efficiency η_TtW
Drive cycle
Sets average speed (WLTP = 47, highway = 100, city = 30 km/h)
Vehicle mass m
kg
Drag coefficient C_d
Mirai 0.29 / Nexo 0.33 / typical SUV 0.40
Frontal area A
m²
H₂ tank capacity
kg
Mirai 5.6 kg / Nexo 6.33 kg / heavy truck 30-60 kg
Storage pressure
bar
700 bar is standard for cars; 350 bar for buses and trucks
Auxiliary load P_aux
W
Air-conditioning, lights, fuel-cell balance of plant
Results
—
Total power P_total (W)
—
Economy (kg-H₂/100km)
—
Range (km)
—
CO₂ gray H₂ (g/km)
—
MPGe equivalent
—
Refueling time (min)
—
FCV layout — H₂ tank → Fuel cell → Motor
Hydrogen flows from the tank into the fuel-cell stack, reacts with atmospheric O₂ to produce electricity, drives the motor, and emits only water (H₂O).
Hydrogen consumption rate and driving range. LHV = 33.33 kWh/kg, η_TtW = 0.42 for PEMFC and 0.50 for SOFC. A 5.6 kg @ 700 bar Mirai tank gives ≈840 km of range.
Aerodynamic drag and rolling resistance. ρ = 1.225 kg/m³, C_rr = 0.008, g = 9.81 m/s².
Hydrogen FCV Fuel Economy & Range Design
🙋
FCVs like the Mirai run on hydrogen, right? But why bother with a fuel cell making electricity to drive a motor? Isn't that just a more complicated BEV?
🎓
Good question. Inside a fuel-cell stack the reaction H₂ + ½O₂ → H₂O sends electrons directly into the motor; the tailpipe emits only water. Why bother? Because you get "3-minute refueling" and "800 km range" in one package. BEV fast-charging takes 30 minutes or more, and in cold weather or on heavy trucks the battery weight and charging time really start to hurt. Plug in the defaults (1800 kg, Mirai's 5.6 kg tank, WLTP 47 km/h) and you can see the tool returns about 840 km of range.
🙋
840 km is impressive. The economy reads "0.66 kg-H₂/100km" — how does that compare to gasoline?
🎓
A kilogram of hydrogen has roughly the same energy as a US gallon of gasoline (33.3 kWh), so Mirai's 0.66 kg-H₂/100km is "0.66 gal-equivalent per 100 km" — about 90 MPGe. A typical gasoline car is 30-40 MPG, so on energy efficiency the FCV is 2-3× better. But that's Tank-to-Wheel only; the CO₂ and energy used to make the hydrogen itself sit on a separate ledger. The "gray-H₂ CO₂ ≈ 60 g/km" you see below is that upstream story.
🙋
So the "60 g/km CO₂" isn't from the car driving — it's from the hydrogen factory?
🎓
Right. Out the back the FCV emits essentially only water (≈0 g/km). But 95 % of today's hydrogen is "gray", made by steam-methane reforming of natural gas, which releases about 9 kg CO₂ per kg H₂ produced. Multiply through and you land at 60 g/km — half a gasoline car (120 g/km), but not zero. "Green hydrogen" made by electrolysing water with renewables drops that to ≈0. So to make FCVs truly zero-emission you have to decarbonise the vehicle and the hydrogen supply.
🙋
Tank capacity stretches the range linearly, of course, but what does "700 bar storage pressure" really mean? Isn't 700 times atmospheric a little crazy?
🎓
It is — that's roughly the pressure at 7 km depth in the ocean. Passenger FCVs use 700 bar; buses and trucks usually use 350 bar. Higher pressure packs twice the H₂ into the same volume, so range goes up, but the tank has to be a multi-layer "Type IV" carbon-fibre composite that survives being shot with a rifle. Even then it weighs about 10× a gasoline tank of the same energy — that's one reason passenger cars have leaned toward BEV.
🙋
Switching the fuel cell to SOFC bumps up the range a lot. So why not always use SOFC?
🎓
SOFC is theoretically the most efficient, but it runs at 600-800 °C and takes a long time to start. So it's not great for "leave home and go" passenger cars — its current home is stationary power and steady-state heavy-duty. PEMFC sits at the sweet spot for cars: cold start, fast response, decent ride quality (Mirai). AFC is the classical alkaline cell, used on Apollo to make water and electricity at once — beautiful chemistry, but it's poisoned by CO₂ in air, so it's never used in road vehicles. Toggle the cell type and you can see how the efficiency difference shows up directly in range.
Frequently Asked Questions
First compute the total power demand P_total = tractive power (from rolling and aerodynamic drag) + auxiliary power. Convert it to energy per kilometre E [Wh/km] = P_total [W] / v [m/s] / 3.6. Then with a Tank-to-Wheel efficiency η_TtW (about 0.42 for PEMFC) and the lower heating value LHV = 33.33 kWh/kg of hydrogen, the consumption rate is F_H₂ [g/km] = E / (η_TtW · LHV). Range R [km] = tank mass m_tank [kg] / F_H₂ × 100. With the default 5.6 kg tank of a second-generation Toyota Mirai at WLTP-average 47 km/h and 1800 kg, the tool returns about 840 km, which matches the catalogue 850 km.
The tool uses Tank-to-Wheel efficiencies of 0.42 for PEMFC, 0.50 for SOFC and 0.38 for AFC. These are effective values that already account for balance-of-plant losses (compressor, cooling pump, water management). PEMFC starts at room temperature with fast output response and powers passenger FCVs such as Mirai and Nexo. SOFC runs hot at 600-800 °C with higher efficiency but slow start-up — best for stationary power. AFC is the classical alkaline cell used in the Apollo program; it is poisoned by CO₂ and unsuitable for road vehicles. Switching cell type while leaving all other inputs the same propagates the efficiency difference directly into range and H₂ consumption.
Gray hydrogen is produced by steam-methane reforming (SMR) of natural gas and emits about 9 kg-CO₂ per kg of H₂. The tool computes "F_H₂ [g/km] × 9" and returns about 60 g/km at default settings — half a gasoline car (≈120 g/km) but not zero. Green hydrogen, produced by electrolysis with renewable electricity, is essentially zero on a Well-to-Wheel basis. Cutting transport CO₂ requires both "wider FCV adoption" and "decarbonising the hydrogen supply itself". The California H2 Station Network and Iwatani's network in Japan are gradually increasing their green-hydrogen share.
On Tank-to-Wheel efficiency the BEV wins easily at 70-80 % versus 40-50 % for an FCV. But on a Well-to-Wheel basis (primary energy to wheel), green-H₂ FCV and renewable-electricity BEV come out roughly equal. The strengths of FCV are (1) three-minute refueling vs 30+ minutes for BEV fast-charging, (2) small range loss in cold weather, and (3) no battery-mass penalty on heavy long-haul vehicles. A complementary split is emerging worldwide: BEV for passenger cars and FCV for commercial heavy-duty.
Real-World Applications
Passenger FCVs (Toyota Mirai / Hyundai Nexo / Honda CR-V e:FCEV / BMW iX5 Hydrogen): 5.6-6.3 kg H₂ tanks, 650-850 km range, 3-5 min refuel. The second-generation Mirai achieves WLTP 850 km and matches this tool's defaults. The BMW iX5 Hydrogen uses an X5 platform with a 6 kg H₂ tank and a 295 kW peak motor. Honda CR-V e:FCEV combines H₂ refueling with plug-in charging — EV mode for commutes, FCV for road trips.
Heavy-duty commercial vehicles (trucks, buses): Hyundai XCIENT Fuel Cell trucks (running logistics in Switzerland), Toyota SORA bus, Hino Profia FC. Long-haul, high-payload duty cycles penalise BEV batteries by weight, so FCV pays off. Tank capacities 30-60 kg, 500-800 km range, 10-20 min refuel. Daimler GenH2 uses liquid hydrogen and targets 1000 km. Raise the tank capacity to 30 kg in this tool and you can reproduce the European long-haul reference point.
Hydrogen station infrastructure: California H2 Station Network (~60 sites), Iwatani in Japan (161 sites as of 2024), Air Liquide / Linde in Europe, Hyundai in Korea. Each site costs roughly US$5 million to build; the open issues are growing the green-hydrogen share and improving compressor and pre-cooling efficiency. Knowing the H₂ consumption per vehicle (this tool) lets operators estimate how many vehicles one station can serve per day.
Stationary fuel cells and cogeneration: Panasonic's ENE-FARM and Bloom Energy's SOFC servers exceed 60 % electrical efficiency for homes and data centres. Selecting "SOFC" in this tool reveals a glimpse of that efficiency on the vehicle side. SOFC is also a leading candidate for future large ships, trains and data-centre prime power.
Common Misconceptions and Pitfalls
The biggest pitfall is assuming "FCV is zero CO₂ because the tailpipe is clean". Tank-to-Wheel, only water comes out — but 95 % of today's hydrogen is "gray" (steam-methane reforming) and emits about 9 kg CO₂ per kg of H₂ produced. The default settings give about 60 g/km — half a gasoline car (120 g/km), but Well-to-Wheel only reaches true zero when you switch to green hydrogen and renewables. Always state the boundary (Tank-to-Wheel vs Well-to-Wheel) when comparing FCV environmental performance.
Second pitfall: the false either/or "BEV is more efficient, so FCV is unnecessary". BEVs do win on Tank-to-Wheel efficiency (70-80 % vs 40-50 %), but that is not the whole story. FCVs win on (1) 3-minute refueling, (2) no battery-mass penalty for heavy long-haul, and (3) small range loss in cold weather. The emerging global consensus — California's Hydrogen Roadmap, the EU's Fit-for-55 — treats BEV and FCV as complementary, with BEV winning passenger cars and FCV winning heavy commercial.
Finally, the safety myth that "hydrogen tanks explode". Real Type IV tanks (CFRP-wrapped liner) pass safety tests that include being shot with a rifle. Hydrogen is 1/14 the density of air, so leaks rise and disperse rather than pooling — in many scenarios the fire risk is actually below gasoline's. The catch is that hydrogen flames are colourless and invisible in daylight, so fueling stations must use redundant gas detectors and well-designed ventilation. Push the storage pressure from 700 to 1000 bar in this tool and you can feel the trade-off between capacity gain and safety margin.
How to Use
Enter vehicle curb mass (kg): typical FCVs range 1,500–1,900 kg (Mirai ~1,711 kg, Nexo ~1,685 kg, iX5 Hydrogen ~2,500 kg)
Input aerodynamic drag coefficient (Cd) and frontal area (m²): Mirai Cd=0.30, A=2.29 m²; Nexo Cd=0.32, A=2.29 m²
Set tank capacity (kg H₂): Mirai/Nexo/CR-V e:FCEV=5.6 kg; iX5=6.0 kg nominal storage
Simulator calculates total power consumption, economy (kg-H₂/100km), achievable range, gray H₂ emissions, MPGe equivalent, and refueling duration
Worked Example
Toyota Mirai 2024 baseline: mass=1,711 kg, Cd=0.30, frontal area=2.29 m², tank=5.6 kg H₂. At 100 km/h steady highway driving with rolling resistance coefficient=0.015, fuel consumption ≈0.79 kg-H₂/100km. Total system power≈61 kW (62% stack efficiency assumed). Range calculation: 5.6 kg ÷ 0.0079 kg/km ≈707 km. Gray H₂ (steam methane reforming, 9.3 kg CO₂ per kg H₂)=73.6 g CO₂/km. MPGe equivalent≈89 MPGe (based on 33.6 kWh per kg H₂ conversion). Refueling 5.6 kg at 100 g/min dispenser≈56 minutes; at 200 g/min (fast fill)≈28 minutes nominal.
Practical Notes
Drag and rolling resistance dominate highway economy; city driving with regenerative braking reduces effective consumption by 12–18% versus highway baseline
Gray hydrogen emissions (SMR pathway) average 9–11 kg CO₂/kg H₂; green hydrogen (electrolysis, renewable grid) approaches zero-carbon when grid carbon intensity <50 gCO₂/kWh
Tank material (composite carbon fiber) adds 30–40 kg curb mass penalty; confirm OEM spec weight before modifying mass input
Refueling time depends on dispenser pressure (350 bar vs. 700 bar SAE standards) and thermal management; 700 bar enables 3–5 minute fills on high-flow units
Hyundai Nexo production rated 6.3 kg-H₂/100km WLTP; Mirai achieves 5.0–5.3 kg/100km real-world highway; use simulator to predict duty-cycle variance