Diesel alternatives: What you need to know

The whole alternative-power scene is in a continual state of change, as new technology shifts the goal posts almost every day. We’re keeping abreast of developments and here’s the state of play, as at March 2022.

Combustion engines that power the transport sector, dominated by cars, trucks, buses and bikes, produce 16 per cent of Australia’s greenhouse gas emissions. That proportion alone makes transport a target for reductions, plus there are the additional factors of reliance on imported powertrains and fuel stocks, in an uncertain trading world.

Any change to our diesel-fuelled truck world is going to be evolutionary, rather than revolutionary, because the supermarket shelves have to be filled and people have to move around.

In a way, it’s almost beneficial to the truck business that Australia lags way behind the developed world in adopting global emissions targets, because at least we get to see overseas mistakes and may avoid making them ourselves.

Currently there are only three viable alternatives to diesel trucks: battery electric vehicles (BEVs), fuel cell electric vehicles (FCEVs) and renewable-fuel internal combustion engines (ICEs). ICEs can also be used in conjunction with BEV drivelines, in the form of Hybrid trucks.

All truck makers have developed BEVs to varying stages of production readiness, but at this stage all of them are suitable only for short-haul distribution work, probably within 20-30km of a depot where batteries can be recharged.

Proton-exchange membrane (PEM) FCEVs use hydrogen gas as a ‘fuel’ to produce combustion-free electricity. Only Toyota and Hyundai now have FCEV production passenger cars; Hyundai is spot-selling FCEV trucks and buses into selected applications and Nikola, Cummins and GM have truck-suitable fuel cells under development.

Neither BEVs nor FCEVs are suitable for linehaul work at this stage, because of the limited range of BEV batteries and the volume of hydrogen tankage needed on an FCEV truck.

That’s why Cummins and other engine makers are developing ICEs that can run on a variety of renewable fuels. If a fuel is derived from natural growth or decay processes and burnt, its CO2 emissions are considered neutral, because they can be absorbed by plants once more. Some alternative fuels have no carbon content at all and produce no CO2 when burnt.

OK, what’s happened so far in the real world?

BEVs are already a given and all truck makers have at least one variant in development or limited production. Sure, you can’t yet wander into an Australian truck dealership and take delivery of your new BEV truck, because it’s early days and truck makers want to ‘seed’ vehicles into fleets that will operate them correctly and provide accurate operational data. However, the technology works… in short-haul vocations.

Related reading:
Hyundai outlines its hydrogen future
Daimler and Volvo fuel cell partnership gains pace
BHP and Centurion go electric

Within a very short time, all truck makers will offer BEV metro trucks, with range and payload limitation caused by battery capacity. As battery energy density improves, so will the operational range of BEVs. However, without en route battery-swap infrastructure, BEVs will not be suitable for linehaul work, unless there’s some unforeseen technological breakthrough.

At present, BEVs have batteries and electric components wedged into chassis designed for diesel powertrains, but the next generation will be specifically designed for BEV powertrains. The result will be more battery capacity for a given tare weight and drivelines with lighter wheel motors, not conventional drive axles.

Volume production BEVs are a certainty.

Referred to as ‘fool cell vehicles’ by Elon Musk, fuel cell electric vehicles don’t have the clear, if application-limited, acceptance that BEVs do. However, like BEVs, FCEVs have the attraction of emissions-free operation, plus the potential of increased operating range.

However, as this chart clearly shows, an FCEV is far less efficient than a BEV and it’s significantly more expensive as well.

Unlike the almost universal development of BEVs by major truck makers, FCEVs have been developed by only a few. If the experience with FCEV cars is any indication of market success, FCEV trucks don’t seem to have much of a future at all.

Now that Mercedes-Benz has abandoned its FCEV car initiatives and Honda has ceased production of the Honda Clarity FCEV, Hyundai’s NEXO and Toyota’s Mirai are the only series-production FCEV cars in the market. Both makes scored world-wide volume increases in 2021 – the Mirai went from from 1770 vehicles in 2020 to 5918 in 2021, while 6781 NEXO sales in 2020 went up to 9620 vehicles in 2021.

At face value, this seems positive, but Toyota, Hyundai and the governments supporting the rollout of FCEVs jumped through financial hoops to achieve this. In California, the Mirai was given a 65-per cent discount from its US$50k list price, while US federal and state-level tax incentives discounted it a further US$12.5k. Toyota also offered a US$15k fuel credit for the first three years of operation.

Nearly all the Hyundai NEXOs sold in 2021 were in South Korea, where there was a subsidy provision of around US$30k that halved the sticker price.

Nevertheless, Hyundai is persevering with its hydrogen-powered FCEV XCIENT trucks and five evaluation units arrived at the Port of Auckland in New Zealand in late 2021. New Zealand is only the third country to have access to these trucks, following Switzerland and Korea.

Construction of a state-of-the-art ‘green hydrogen’ production and fast-refuelling facility is scheduled for operation near the entrance of Port of Auckland, in mid-2022. New Zealand’s green hydrogen will be produced from geothermal power, in contrast to nearly all industrial hydrogen that’s produced from natural gas (CH4), in a high-emissions process.

Trucksales intends to follow progress of the NZ FCEV evaluation during 2022/23, in the hope that its economics are better than the European experience so far.

In January 2022, the City of Montpellier, France made the decision to cancel an order for 51 FCEVs, in favour of BEVs, scrapping a €29-million (A$42.5 million) Montpellier Horizon Hydrogène project. The cancelled FCEV plan involved a 2MW electrolyser with hydrogen storage, powered by 2.8MW of photovoltaics, to generate 800kg of green hydrogen per day for the bus fleet.

However, a final review of projected costs revealed that the purchase price and associated set-up for the FCEV bus choice would have cost €0.95 (A$1.40) per kilometre, in comparison to €0.15 ($0. 22)/km for BEVs. The FCEV buses would have been six times more expensive to operate, costing €3 million (A$4.4 million) per year, compared to €500k (A$733k) per year for the BEVs.

Despite the apparent adverse economics and its poor FCEV car experience, Mercedes-Benz’s Actros GenH2 prime mover FCEV prototype has begun a development program and customer trials are planned for 2023. It uses liquid hydrogen to power the fuel stack, allowing more compact fuel tanks, giving the vehicle a higher payload capacity and an estimated driving range of more than 1000km.

It’s interesting to note that after much FCEV fanfare, shady trading behaviour and a company restructure, Nikola’s FCEV truck is so far stillborn.

The company’s first production truck isn’t based on the original Nikola FCEV at all, but on an Iveco S-Way prime mover, retro-fitted with a BEV powertrain. For the US market it’s fitted with an Australian-market tandem drive, instead of a European single-drive and has a 750kWh battery pack, 645hp and a claimed 560km operating range.

If a Nikola FCEV emerges, it will be based on the same Iveco S-Way truck. A prototype has hydrogen tanks, enabling a claimed 800km of range.

Interestingly, the US military establishment has invested in FCEV development for one very significant reason: a fuel cell has no ‘heat signature’ and unlike an ICE, can’t be detected by heat sensitive equipment.

Parallel with its investment in electric vehicles, Cummins is actively pursuing internal combustion engine (ICE) developments that use low-carbon and renewable fuels, in variants of its spark-ignition and compression-ignition engines.

Low-carbon fuels emit less CO2 than diesel fuel; carbon-neutral fuels also emit CO2 when burned, but the carbon emissions are fully offset by another activity; zero-carbon fuels, such as ‘green’ hydrogen, do not emit CO2 at all when burned; and carbon-negative fuels are those where fuel generation and consumption results in a net reduction in greenhouse gas emissions.

At this stage the fuel field looks like this: hydrogen, natural gas, biodiesel and synthetic ‘e-fuels’. However, it’s important to remember that all these fuels – even hydrogen – produce oxides of nitrogen (NOx) when burnt and these emissions have to be eliminated using existing selective catalytic reduction (SCR) technology.

Hydrogen is being touted as the ‘new diesel’, but it’s far from that. Even with the best available technology, production of ‘green’ hydrogen is expensive and inefficient, so that by the time it’s burnt in an engine the net result is only around 18-46 per cent thermal efficiency, according to MIT.

Hydrogen is notoriously difficult to store and transport, so tankage is an issue.

Natural gas or methane (CH4) produces less CO2 than diesel and renewable natural gas (RNG) can be carbon negative. For example, RNG produced from degradation of organic matter that would otherwise be left to emit methane emissions, has negative carbon intensity.

Biodiesel is a renewable fuel produced primarily from fats and vegetable oils. The plants used as feedstock to produce biodiesel withdraw carbon from the atmosphere and when biodiesel is burned, it returns the same carbon atoms back to the atmosphere – theoretically, making biodiesel carbon neutral. Blends of biodiesel are already in diesel pumps around Australian and the next step towards lowering emissions are engines that can run on B40 and then on B100.

Synthetic fuels – e-diesel and e-gasoline can be produced using CO2 and green hydrogen, so they’re carbon-neutral, because they release the carbon that was originally used to create them back to the atmosphere. Obstacles are high cost and limited availability.

Cummins’ so-called ‘fuel-agnostic’ engine and powertrain platforms are designed to expand the use of low to zero carbon fuels. They consist of a series of engine versions that are derived from a common base engine. The bottom end of the engine looks the same, but unique cylinder heads are designed to accommodate different low- or zero-carbon fuels.

They are said to have similar operating practices, vehicle installation and performance characteristics as today’s diesel engines and are aimed at transport tasks that can’t be met by BEV or FCEV vehicles. This technology approach will be applied across Cummins’ X-Series, L-Series and B-Series platforms.

Tallinn, the capital city of Estonia, has taken a sustainability step with its new fleet of 350 Solaris Urbino CNG buses, powered by Cummins L9N engines that run on renewable biomethane gas.

So where to from here in Australia? Given our slow take-up of emission targets and low-emission trucks, we won’t be anywhere near first out of the gates when it comes to alternative fuels and power sources. So, as we said earlier, our shift will be evolutionary, and you can bet that you’ll see diesel trucks on our roads for a long time to come.