This is part 6 of a seven part series which explores some of the issues around zero carbon vehicles and which future technologies might be best for HGVs to avoid carbon emissions. The seven parts are:
- Understanding the Typical Power Requirements of an HGV
- Basic Designs of Diesel, Battery and Fuel Cell Powertrains
- Comparing Diesel, Battery and Fuel Cell Powertrains
- Assessing Future Manufacturing Costs of Diesel, Battery and Fuel Cell Powertrains for HGVs
- Costs of Hydrogen Fuel / Building A Hydrogen & Electric Charging Infrastructure
- Commercial Viability of Operating A Battery or Fuel Cell Powertrain HGV (this post)
- Summary, A Look at Developments Which May Help Achievement of Zero Carbon In-use HGVs.
Part 6: Commercial Viability of Operating A Battery or Fuel Cell Powertrain HGV
In Part 6, real world fuel economy figures from diesel truck operators are compared against estimated fuel economy for proposed fuel cell and battery HGVs, in terms of kg hydrogen per 100 km and for BEVs kWh per 100km. These are then compared with a truck operator’s capital and operating costs to examine overall annual costs.
6.1 Fuel Economy of Diesel HGV Powertrains
UK operational data on 38-44 tonne diesel trucks shows fuel economy of 7.6–8.5 mpg (US gallon 6.3-7.1 mpg) which equates to hydrogen usage of 9.9-11.1 kg/100 km (at hydrogen LHV). There is no indication of the average freight weight carried but US data shows that efficient truck operators run circa 20% empty and some cargos would be volume limited rather than weight limited, which would improve fuel economy compared to an always fully loaded vehicle (RHA 2018, FHA 2007).
6.2 Fuel Economy of Hydrogen Fuel Cell HGV Powertrains
In the absence of published data with comparative drive cycles, performance claims regarding two hydrogen fuel cell HGV demonstrators from manufacturers Toyota and Nikola have been examined along with data from Ballard, a fuel cell manufacturer.
Toyota Project Portal Demonstrator & Fuel Fuel Economy
Toyota’s ‘Project Portal’ class 8 demonstrator truck, based on a Kenworth T680 “Glider” (a truck supplied without a powertrain) was announced in October 2017 (Kenworth 2018). It produces 500 kW for “short bursts” with 228 kW fuel cell output (two Toyota Mirai 114 kW fuel cell stacks) with 12 kWh of battery storage. It uses a fuel cell dominant design with 40 kg of hydrogen stored in four 10 kg tanks at 700 bar with a range of 320/km making fuel economy 12.5 kg/100 km (Toyota 2017, Trucks 2017a). The Toyota demonstrator operates in an area around the US port of Los Angeles. Driver feedback is that the truck causes less fatigue, is smooth to drive and quiet: “This is the first vehicle I’ve ever driven that I can hear the suspension when I drive down the road.” (Freightwaves 2018)
Given the short-haul nature of the Toyota demonstrator, likely to operate at urban rather than motorway speeds, the 500kW peak output is in line with expectations from the UK Short-haul HGV specification (468kW) modelled in Part 1.6. Fuel cell power output at 228kW is towards the top end of that expected by modelling. As the Toyota demonstrator uses two standard Toyota Mirai car fuel cells this may just be the consequence of component standardisation. Toyota have yet to produce any detailed comments on design choices or performance.
The 12 kWh of battery storage requires a battery power to energy ratio of circa 23 W/Wh to produce at least 272 kW for a short period of time. This is a surprisingly high ratio compared to the more common power to energy ratio of 5-10 W/Wh (Sakti 2014). Battery storage would be exhausted in under 3 minutes of peak power output, confirming the “short burst” nature of the peak power.
The Toyota Project Portal truck achieves 12.5 kg/100 km, based on 40kg of hydrogen storage with a reported range of circa 320 km. A Beta version of this truck has been announced, with an extended range achieved by additional hydrogen storage rather than any claim of improved fuel cell system economy (Autoblog 2018, Toyota 2018b).
Initial comparison between the Toyota truck (12.5 kg/100km) and typical UK diesel efficiency (9.9-11.1 kg/100km) is not favourable. However, Toyota have yet to provide detailed drive cycle data or weight of loads carried so specific reasons for poor fuel economy relative to diesel trucks are hard to identify. One possible avenue for future consideration may be the impact on fuel cell stack efficiency of delivering the much wider range of power outputs required for a fuel cell dominant 40-tonne truck using stacks originally designed for the much lighter weight Toyota Mirai car.
Ballard Modelling
Ballard (2018a) model a drayage truck not dissimilar to the Toyota Project portal with economy of 8.3 kg/100 km. This appears to be a battery dominant design, which permits the fuel cell to be turned off at low power requirements, unlike the Toyota, which may explain the better efficiency. It is modelled at overall 36,000 kg truck weight (rather than 40,000 kg) although this is not an unreasonable assumption given that the truck will not always be carrying a full load.
A collaboration between suppliers and the Swiss Co-op also reports a 34-tonne prototype truck with fuel efficiency of 7.5-8 kg of hydrogen/100 km based on a 100 kW Powercell manufactured fuel cell and 120 kWh of battery storage with peak power of 250 kW. The vehicle stores 34.5 kg of hydrogen at 350 bar. The fuel cell system efficiency is quoted at 52% and is a fuel cell dominant design. There are no specific details on any battery SOC changes for this fuel efficiency or typical journey cycles (H2 Energy 2018, Coop Mineraloel 2018).
Nikola One Projected Fuel Economy
Nikola Motor plan to launch the Nikola One Class 8 truck in the US in 2021. The specification is still somewhat fluid with different figures being mentioned in press articles and tweets from Nikola. The truck was believed to deliver peak power of 746kW with a 240kW fuel cell system (2 x 120kW stacks) with 60-80kg of hydrogen and 240-360 kWh of batteries powering a set of four electric motors delivering circa 735-746kW. Pre-production test models were launched in April 2019. No data is available on the pressure of the stored hydrogen (Tu 2016, Nikola Motor 2018).
It is believed to be a battery dominant design with a range of 800-1,600 km, intended for use as a long-haul trans-continental truck. The Nikola One is likely to see a wider range of extreme conditions than the Toyota, so a higher peak output and a slightly higher fuel cell output with more hydrogen storage is not unexpected. Fuel economy can be calculated at between 5-7.5 kg/100 km assuming the battery State of Charge (SOC) is the same at the start and end of the journey.
The Nikola One is estimated to achieve somewhere between 5-7.5 kg/100 km. A caveat is that Nicola claim an 800-1,600 km range without distinguishing between 60 kg and 80 kg hydrogen tank options, making an accurate assessment impossible (achieving 800 km on 60 kg of hydrogen delivers an economy of 7.5 kg/100 km, whilst driving 1600 km on 80 kg delivers 5 kg/100 km). Both fuel economy figures will be used to calculate truck annual operating costs, primarily to show the potential financial impact that improvements in fuel cell fuel economy can have. Until road testing data on Nikola One pre-production prototypes is published, these figures can only be considered as indicative. At 7.5 kg/100 km the fuel economy is still favourable, compared to a diesel powertrain. In the calculations it is assumed the battery state of charge is the same at the start and end of the journey. The Nikola One was originally anticipated to be offered with 240 & 360 kWh storage battery options but this may change as greater experience with the pre-production vehicles is built. for the purposes of calculations the 240 kWh battery storage option is assumed.
Fuel Cell Powertrain Fuel Economy Summary
The data above has provided some contrary indications on fuel economy. The Toyota Project Portal fuel economy (12.5 kg of hydrogen/100 km) is well below that of real world diesel truck data whereas the Nikola One fuel economy claims provide both a highly optimistic picture (5 kg/100 km) and a more cautious one (7.5 kg/100 km). The Nikola, Ballard and Swiss Coop figures are in line with academic studies that indicate hydrogen fuel cell powertrains have the potential to be more efficient than diesel in terms of Tank to Wheels (TTW) energy (Helmers & Marx 2012). The magnitude of the difference between the Toyota and Nikola estimates is hard to explain. There could be differences in the use of regenerative braking (there is no information on whether the Toyota truck uses it) and different assumptions on profiles of journey cycles and average weights carried. However, the Toyota’s poor performance against diesel powertrains, which do not use regenerative braking and are based on real world measures, creates a significant question over whether Toyota’s fuel cell dominant design approach is best suited to the high-power demands of HGVs. Limited evidence suggests that the battery-dominant design as proposed for the Nikola One may be better suited to heavy freight applications, especially as the greater battery storage capacity allows fuel cell power output to be more stable, creating opportunities to control fuel cell output at an optimum level of efficiency.
6.3 Fuel Economy of Battery Electric Vehicle (BEV) HGV Powertrains
As with the hydrogen fuel cell powertrain, the fuel economy of a BEV HGV is based on claims from manufacturers with demonstrators. The Tesla Semi is the most publicised of these. Announced in 2017, currently availability is indicated for summer 2020 with a “limited run” although demonstrators have been running for some time (CNBC 2019). Basic news/rumour is that 600kWh and 1,000kWh versions will be available with the latter offering a 640km range. This equates to fuel economy of 1.6 kWh/km (2.5 kWh/mile), although no drive cycle data is available and the Tesla website claims that energy consumption is less than 1.25 kWh / Km (2 kWh/mile) (Tesmanian 2020). For the basis of this article the 1.25 kWh /km figure will be accepted as an aspiration for 2025 production versions. An electricity price of £0.15/kWh is assumed for recharging cost, although this could vary significantly depending on the charging location.
6.4 Annual Operating Costs
RHA (2018) in the UK and ATRI (2017) in the US provide good overviews of costs faced by diesel powertrain truck operators, acquired through surveys. UK data is shown in Figure 22 which assumes annual mileage of 136,850 km (85,000 miles) per year for a 44 tonne 3-axle tractor unit & 3-axle trailer. US data is broadly in line on comparable measures. A number of costs, such as driver-based costs and repair and maintenance, are arguably similar for both diesel and fuel cell trucks.
Figure 22: UK Truck Operator – Annual Costs for Diesel Powertrain
| Cost | £ | £/mile | % costs |
| Vehicle Excise Duty | 1,200 | 0.014 | 1.0% |
| Insurance | 3,435 | 0.040 | 2.9% |
| Depreciation – tractor | 14,580 | 0.172 | 12.2% |
| Depreciation – trailer | 2,044 | 0.024 | 1.7% |
| Fuel | 45,339 | 0.533 | 37.9% |
| Tyres – tractor | 1,527 | 0.018 | 1.3% |
| Tyres – trailer | 1,562 | 0.018 | 1.3% |
| Maintenance – tractor | 8,729 | 0.103 | 7.3% |
| Maintenance – trailer | 4,901 | 0.058 | 4.1% |
| Driver costs | 36,354 | 0.428 | 30.4% |
| TOTAL | 119,671 | 1.408 | 100.0% |
For operating cost comparison purposes, annual truck depreciation and fuel costs have been combined in Figure 23 and then cost differences from diesel presented in Figure 24. Assumed fuel economy is 12.5kg hydrogen /100km for the 500kW Fuel Cell and both 5kg/100km and 7.5kg/100km have been calculated for the 750kW Fuel Cell. 125 kWh / 100km has been calculated for the Battery Electric Vehicle (BEV) truck.
Figure 23: UK Truck Operator – Annual Costs for Truck Depreciation and Fuel
| Powertrain | 1,000 units current price with H2 price £10/kg | 10,000 units post 2020 price with H2 price £6.50/kg | 50,000 units post 2025 price with H2 price £3.20/kg |
| Diesel – HGV | £59,919 | £59,919 | £59,919 |
| Fuel Cell – 12kWh battery, 40kg hydrogen, 500kW power Fuel Efficiency: 12.5kg/100 km | £202,426 | £133,489 | £74,389 |
| Fuel Cell – 240kWh battery, 60kg hydrogen, 750kW power Fuel Efficiency: 7.5kg/100km | £149,98 | £97,141 | £60,287 |
| Fuel Cell – 240kWh battery, 60kg hydrogen, 750kW power Fuel Efficiency: 5kg/100km | £115,981 | £74,701 | £49,407 |
| BEV – 1,131kWh battery, 750kW power Fuel Efficiency: 125kWh/100km | £82,356 | £59,725 | £55,901 |
Figure 24: UK Truck Operator – Differences in Annual Costs for Depreciation and Fuel
| Powertrain | 1,000 units current price with H2 price £10/kg | 10,000 units post 2020 price with H2 price £6.50/kg | 50,000 units post 2025 price with H2 price £3.20/kg |
| Diesel – HGV | – | – | – |
| Fuel Cell – 12kWh battery, 40kg hydrogen, 500kW power Fuel Efficiency: 12.5kg/100 km | £142,507 | £73,570 | £14,470 |
| Fuel Cell – 240kWh battery, 60kg hydrogen, 750kW power Fuel Efficiency: 7.5kg/100km | £90,062 | £37,222 | £368 |
| Fuel Cell – 240kWh battery, 60kg hydrogen, 750kW power Fuel Efficiency: 5kg/100km | £56,062 | £14,782 | -£10,512 |
| BEV – 1,131kWh battery, 750kW power Fuel Efficiency: 125kWh/100km | £22,427 | -£194 | -£4,018 |
Shading meaning: white – competitive, red – uncompetitive, green – offers commercial savings
Figure 24 shows that by 2025 the 750kW Fuel Cell and the 750kW BEV could be competitive with diesel trucks on annual operating costs at a fuel economy of 7.5kg/100km and 125kWh/100km. At an “optimistic” fuel economy of 5kg/100km, the 750kW Fuel Cell would offer savings of circa £10,500 (9% of all operating costs). The 500kW truck would be uncompetitive at a fuel economy of 12.5kg/100km, with depreciation and fuel costs circa 25% higher than the diesel equivalent. The poor fuel economy makes it a weaker commercial proposition for truck operators , despite its lower capital costs. No allowance has been made for any additional labour costs from the slower “refuelling” of BEVs or the use of operator owned renewable electricity generation (wind or solar) to reduce recharge costs.
Truck Operating Cost Summary
By 2025 FC HGV trucks and BEVs could be commercially competitive with diesel equivalents, subject to achieving anticipated manufacturing volumes, technical developments, hydrogen fuel prices and electricity recharging costs. This assumes no significant introduction of charges for carbon or pollutant emissions for diesel vehicles or changes to fuel duty on hydrogen fuel or electricity for transport applications. As capital costs for FC and BEV HGVs are still likely to be higher than diesel in 2025, the key to competitiveness will be a combination of vehicle fuel economy and hydrogen/electricity fuel costs. Banning the use of diesel HGVs in towns and cities will also change the balance.
References
ATRI (2017). American Transport Research Institute: An Analysis of the Operational Costs of Trucking: 2017 Update October 2017 [online]. Available at http://atri-online.org/wp-content/uploads/2017/10/ATRI-Operational-Costs-of-Trucking-2017-10-2017.pdf [Accessed 3 February 2020]
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