This is part 7 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
- Summary, A Look at Developments Which May Help Achievement of Zero Carbon In-use HGVs (this post).
Part 7: Summary, A Look at Developments Which May Help Achievement of Zero Carbon In-use HGVs
Part 7 provides a summary of fuel cell and battery electric HGV feasibility for the first generation of vehicles, along with a look at how Generation 2 of zero carbon trucks could be developed further.
7.1 Summary Assessment of Fuel Cell and Battery Electric HGV Feasibility
From the findings in Parts-16, both hydrogen fuel cell and battery electric HGVs could deliver the technical and commercial performance to be competitive with diesel trucks by 2025. The challenges identified at the start of this series have, in the main, potential solutions in place:
Power output: Delivering the appropriate power output (circa 500-750kW) is achievable with currently available technology.
Driving range & refuelling time: Delivering the desired driving range (800-1,600km) using upwards of 60kg of hydrogen or a 1,131 kWh battery is achievable. Developments in fuel dispenser flow rates (above 120kg/hour) are needed to close the gap with diesel refuelling rates. This technology should start to be introduced during 2020/2021. Rapid recharging of larger batteries presents a key challenge. In the short term, suitable applications would involve vehicles being charged overnight at their operating depot.
Durability: Life in running hours of over 25,000 hours has been demonstrated by fuel cell bus operations with future maintenance costs potentially in line with diesel HGVs.
Weight impact: Fuel cell HGV powertrains have the potential for lighter weight than diesel, although choices on storage battery capacity may offset this. Challenges exist for weights on large capacity vehicles although compromises on driving range can compensate for this.
Volume impact: Bulkier hydrogen storage systems will create demand for up to 3m³ of extra truck volume, but design solutions have been identified.
Fuel cell HGV manufacturing costs: By 2025, the price premium over diesel powertrains for a hydrogen FC powertrain HGV could be as little as 40% and around 100% for a Battery Electric HGV.
Fuel costs: Hydrogen refuelling costs of $4.23/kg are potentially achievable which, using electrolysis and renewable electricity, would lead to zero GHG emissions. Battery electric HGVs would have lower fuel costs.
Hydrogen refuelling/Electric Charging infrastructure: Policy makers have demonstrated a willingness to provide funding to encourage the building of refuelling networks. Building charging facilities for electric vehicles at HGV operating centres would be a first step for most truck operators.
Commercial viability: Subject to achieving fuel economy levels of 7.5kg/100km, FC HGV annual operating costs for operators can be competitive with diesel vehicles. Whilst the solutions are credible, they are yet to be fully demonstrated. From a technology perspective, FC HGVs could best be described as at an engineering prototype stage or Technology Readiness Level 6 (TRL 6), as evidenced by the operation of the Toyota Project Portal demonstrator truck (DOE 2011). Figure 25 shows the subsequent steps that need to be taken before the technology is ready for full commercial operation (TRL 9). The launch of the Nikola pre-production truck in April 2019 signalled a move to TRL 7. Although Nikola may argue this is TRL 8, the trucks will not be produced using the final manufacturing processes. Battery electric HGVs could also be competitive by 2025.
Figure 25: Technology Readiness Levels
|TRL9||Full commercial operation||Actual system operated over the full range of |
expected mission conditions.
|TRL8||Pre-production||Actual system completed and qualified through |
test and demonstration
|TRL7||Demonstration system||Full-scale prototype system demonstrated in |
|TRL6||Engineering Prototype||Engineering-scale models or prototypes are |
tested in a relevant environment.
With technology not proven for full commercial readiness there are potential risks that progress will not be as rapid as anticipated or proposed solutions do not deliver promised performance. Conversely, there are ongoing developments in short-haul BEV freight vehicles, such as the Tesla Semi and the Mercedes-Benz Electric Truck, which could drive more rapid powertrain development and increased manufacturing volumes for components such as electric motors (Electrek 2018, Daimler 2018).
Of the technical/commercial issues covered in this review, the poor fuel economy of the Toyota demonstrator truck (12.5kg hydrogen/100km) and the lack of availability of hydrogen refuelling at cost close to $4.23/kg (£3.20/kg) raise concerns. This is because fuel economy combined with the cost of hydrogen fuel could be critical to commercial success for FC HGVs, particularly with the likelihood that the purchase price of FC trucks will be at a premium to diesel HGVs until well beyond 2025.
Policy makers appear to be placing a strong emphasis on agreeing international vehicle and refuelling safety regulations, which should give market re-assurance that hydrogen FCEV are safe in operation. In the US (mainly California), Japan and Europe there is encouragement for the development of a hydrogen fuelling infrastructure which is mainly targeted around cars and buses. The UK policy approach of encouraging the building of local clusters of hydrogen refuelling stations will also require greater emphasis on hydrogen fuel prices, to break out of the hydrogen fuel challenge described in Part 5. Consideration needs to be given to higher volume fuel dispensers to cope with heavier truck refuelling weights of circa 60-80kg of hydrogen rather than just those for cars (5kg) and buses (20-40kg).
Policy makers generally, including the UK, have chosen not to apply a fuel duty to hydrogen fuel for transportation, which should encourage earlier adoption of the technology. A key challenge will come if fuel duty revenues from diesel vehicles decline rapidly. Policy makers will have to balance recovering lost revenue, by potentially introducing a hydrogen fuel duty, against the wider benefits of decarbonising the transport sector and reducing health harming NOx emissions.
In the US the Department of Energy, along with CARB, are encouraging specific truck demonstrator projects but this is not currently being repeated elsewhere. The UK can be described as an interested spectator rather than an active encourager of hydrogen fuel cell technology for trucks. Despite the UK’s Committee on Climate Change suggesting that 40% of HGV’s will need to be hydrogen powered by 2050 there are little signs of any active policies to achieve this or any investment in FC truck research; something that will need to be rapidly addressed if the UK wants a mainstream role in FC technology. Some funding (£1.3 million) has been given to ULEMCo to explore the use of hydrogen as a dual-fuel in a modified internal combustion engine, but this is a tiny fraction of the investment required (Commercial Fleet 2017, ULEMCo 2018).
7.2 Future Work on Fuel Cell HGVs: Generation 2.0
This article has highlighted the significant challenges to achieving a first generation of hydrogen powered and battery powered zero-emission trucks. This section takes a brief look at where a future generation of fuel cell HGVs could potentially improve on Generation 1.0.
Fuel Economy Improvements from Battery Dominant Designs
With fuel usage a major contributor to truck operator annual operating costs, any improvements in fuel economy will improve the commercial viability of FC HGVs. There is evidence that battery dominant designs, such as the Nikola One, can offer better fuel economy than the fuel cell dominant Toyota demonstrator. With battery storage and effective power management, a fuel cell can run at optimum efficiency for longer rather than adjusting rapidly to changes in power demand, improving fuel economy. As the cost of fuel cell stacks falls further, the economics of larger fuel stacks running at lower and more fuel-efficient power outputs can be explored as originally proposed by Barbir & Gómez (1997).
Ammonia rather than Hydrogen?
The projected manufacturing cost in 2025 of the Nikola One 60kg hydrogen storage tanks is $45,800, 160% higher than the $17,400 cost of the fuel cell system itself. There are potential technical developments on the conversion of ammonia to hydrogen which may allow significant reductions in manufacturing cost, weight and volume of storage systems by switching from 700 bar hydrogen gas to 10 bar pressure ammonia liquid (Zamfirescu 2009, Afif 2016, Phys 2018, CSIRO 2018). A switch in fuel type to ammonia may also help reduce the 30-40 minutes of refuelling times for dispensing larger volumes of compressed hydrogen, althugh it looks likely that by 2021 Heavy Duty hydrogen refuelling technology will be available. A sufficiently compact reforming unit, capable of decomposing the ammonia to hydrogen at the right rate, would need to be added to the truck systems. However, there is scope to fund this by replacing expensive hydrogen gas storage tanks. As a less bulky fuel than hydrogen, ammonia is already being considered to safely transport renewably generated hydrogen by ship from Australia to access markets in Asia (ABC News 2018). The logical extension is to use ammonia in the vehicles themselves.
Fuel Economy Improvements from Solid Oxide Fuel Cells
Battery dominant designs allow alternatives to PEMFC to be considered, if they deliver better fuel economy at stable output levels. Solid Oxide Fuel Cells have the potential to be 5-10% more efficient but were historically discounted for transport applications due to their poor dynamic response to power and their slow start-up from cold as they operate at temperatures of 800-1,000°C. Bossel (2012) has demonstrated a small-scale SOFC which reaches operating temperature in under 5 minutes. Using 240kWh of battery storage, a truck could be powered from the battery alone for upwards of fifteen minutes even with high power demand. If the start-up time for a 240kW output SOFC could be improved to under 15 minutes, then there appears potential for use in HGVs, particularly as an HGV driver can spend 10-15 minutes on daily walkaround checks of a vehicle (DVSA 2013).
There are signs that SOFC technology could be used for transport applications with news that UK-based Ceres Power, in partnership with Nissan, have been awarded research funding to develop its SteelCell SOFC for electric vehicle applications. SteelCell is a 5kW modular stack which can be scaled up to at least 200kW and has increased power density, reduced start-up times and vibration tolerance to address automotive applications. The research project will build a compact and robust demonstration SOFC stack to be deployed with a Nissan fuel cell module. There are no details on efficiency or potential stack cost, but Ceres claimed “the fuel cell stack could be mass produced at a competitive price due to its low-cost steel and ceramic parts” with applications including cars, light commercial and heavy commercial vehicles (Ceres 2018a, 2018b). The Ceres fuel cell could work with natural gas and bio-fuels as well as hydrogen, meaning that it is not dependent on having a widespread hydrogen fuel infrastructure. Ceres have indicated that efficiency exceeds 60% at 50-90% of rated power (EFCF 2018).
Whilst no assessment of the Ceres claims is possible at this stage, it does suggest that a new generation of SOFC could be suitable for transport applications as an alternative to PEMFC, given competitive manufacturing costs. No published data is available on SOFC manufacturing costs for transport applications but a 10% improvement in fuel economy from a truck achieving 7.5kg/100km could deliver annual fuel savings to truck operators of circa $4,224 (£3,200), creating scope for SOFC to be competitive with PEMFC even with higher stack costs. The use of ammonia fuel may also be possible in a SOFC without a separate reformer, due to the high temperature stack.
Use of Fuel Cell Technology for Heavier/More Power Intensive Applications
Both hydrogen FC and BEV technologies offer the potential for zero carbon and pollutant emissions for cars, buses and trucks carrying lighter loads for shorter journeys. Assessing which technology is most likely in the future to dominate these lower power applications is outside the scope of this research. However, there is evidence that fuel cells offer benefits over BEV technology in applications requiring higher power output for longer durations, such as powering a long-haul 40-tonne truck. By increasing the number or size of fuel cell stacks, the power output can be scaled up, providing the potential to power larger vehicles which are unlikely to be suitable for BEV technology. This includes heavy construction vehicles and extends to other applications currently using powerful diesel engines, such as trains and shipping. Early signs that this is being considered are:
- JCB, one of the world’s top three manufacturers of construction equipment, took a 9.1% stake in ITM Power (2015) a hydrogen energy specialist/ fuel station operator.
- Alstrom (2018) announced the approval of 14 hydrogen fuel cell trains to come into service in Lower Saxony at the end of 2021. These are two-car diesel multiple units with a 314kW fuel cell with 94kg of hydrogen for each train car (Railvolution 2018).
- CARB in California announced grant funding in 2018 for a project to demonstrate a hydrogen fuel cell-powered ferry providing passenger service between the Ports of San Francisco, Oakland, Redwood City and Martinez (CARB 2018).
For heavy construction applications, such as excavators, power outputs similar to trucks would be needed (210kW for a JCB 33 tonne tracked excavator). Train power output requirements vary from circa 314kW for a train car up to 4,500kW for a high-power locomotive. Ship power requirements vary hugely in size from 2,500kW for a 5,000 tonne ship up to 44,000kW for a 560,000 tonne ultra large crude carrier (MAN 2007). Despite the huge step up in power for trains and ships, the modular nature of fuel cells means the technology could potentially be applied.
Based on current expectations of progress, hydrogen fuel cell and battery powered HGVs could be technically and commercially competitive with diesel powered trucks of 31-44 tonne GVW within 10 years and potentially by 2025. Achieving this would deliver reduced carbon and pollutant emissions from HGVs as well as improving air quality and reducing vehicle noise concerns in urban environments. The use of renewable electricity to produce hydrogen by electrolysis could deliver zero well-to wheel emissions. Major challenges to be overcome include: reducing fuel cell stack and hydrogen storage tank costs by producing greater volumes; significantly reducing the forecourt pump price of hydrogen fuel; improving the fuel economy of fuel cell HGVs. Using historic replacement rates, 93% of the UK diesel HGV fleet (31-44 tonne) could be replaced over a 20-year period. If this was combined with policy incentives to replace the remaining diesel vehicles, then 2050 GHG emissions would reduce by circa 6.6 MtCO2e and NOx emissions by 17,000 tonnes.
However, UK policy makers are currently playing little part in the development of first generation fuel cell trucks, with key technology being developed and trialled by companies in the USA, Japan and Scandinavia primarily supported by the US Department of Energy and individual businesses. The UK is gradually building a hydrogen fuel infrastructure, but this does not currently accommodate refuelling speeds required to satisfy the needs of commercial truck operators. From a policy perspective this leaves the UK as an interested spectator, relying on the developments of others and acting as a follower if fuel cell truck technology is a success. The result is that achievement of the UK’s Committee on Climate Change 2050 targets to reduce carbon emissions from Heavy Goods Vehicles by 80% relative to 1990 levels is possible but not controllable by the UK.
Limitations of this article
This research involved a wide-ranging review of a rapidly developing technology area where commercial interests often limit access to detailed published information. To produce an overview assessment, assumptions were made in several areas based on indications and statements rather than published papers. In particular, claimed fuel economy figures are plausible rather than certain and future fuel cell truck mark-ups and selling prices will depend on the choice of route to market by manufacturers (direct or via a truck dealer). As commercial hydrogen FCEV trucks appear on the market, more accurate technical information should become available.
Recommendations for UK Policy
The speed of hydrogen fuel dispensing for trucks needs to be addressed. UK policy makers also have the opportunity to look beyond a first-generation fuel cell truck, to encourage research on the potential use of more fuel-efficient Solid Oxide FCs rather than existing Proton Exchange Membrane FCs. Combining this with the use of ammonia as a fuel could address the high cost of hydrogen storage tanks for trucks and extend the use of fuel cell technology to larger transportation such as trains and ships, giving the UK a future stake in the development of a new generation of fuel cell technology.
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