Cleaning Up "Oil Burners": Hydrogen-Diesel Engines.
Hydrogen-diesel hybrid retrofits as a near-term decarbonization path for heavy industrial machinery, plus the logistics and adoption challenges that come with them.
Diesel Engines: A Brief Overview
If it’s a work truck, it’s a diesel. If it’s in a mine, it’s a diesel. If it hauls, it’s a diesel. This has been the unspoken rule of modern industrial machinery for decades now.
Diesel has many intrinsic advantages over other forms of fuel, namely gasoline, like a higher energy density and affinity for high compression, making it more energy efficient and powerful torque-wise. These qualities have allowed them to be extensively used in the transportation, logistics, and mining sectors.
However, diesel makes up a significant portion of global vehicle NOx and soot emissions, which are linked to adverse health and environmental effects such as respiratory diseases and air pollution. Take, for example, Australia, a global mining giant, accounting for the world’s largest output of sought-after lithium and in the top 5 nations for the extraction of other rare earth metals like gold, iron, lead, zinc, and nickel (Australia - mining 2022). In their case, “30% of greenhouse-gas emissions are caused by the use of diesel engines, largely in mining vehicles and power generators” (UNSW Sydney team 2022).
These engines also produce considerable levels of NOx, particulate matter known as “soot”, and other hazardous pollutants that significantly contribute to air pollution and smog. Although the diesel engine industry, in general, has been making strides towards cleaner diesel emissions using emissions-reducing technologies like diesel particulate filters, urea injection, and selective catalytic reduction systems (McGlothlin, 2019), it is evident that more will be required to solve the problem.
Hydrogen-Diesel Hybrids
The possibility of hydrogen power replacing or supplementing diesel power in long-haul logistics has already been a talking point by industry leaders for some time now (Iversen, 2022). However, most methods involved lengthy industry conversion processes and, in essence, starting the heavy machinery industry from scratch.
However, a new research breakthrough from the University of New South Wales in Australia may have bridged this gap between diesel and hydrogen. This innovation allows diesel engines to be easily retrofitted to work with a mixture of 90% hydrogen and 10% diesel (Kook et al., 2022).
Furthermore, since the result of burning hydrogen is simply water vapour, the majority of the emissions normally associated with diesel engines are reduced. Researchers also noticed a notable increase in efficiency in the engine, making this an even more important breakthrough.
Advantages of Hydrogen-Diesel Hybrids
The main point of this breakthrough is the possible reduction of harmful emissions like NOx from diesel engines, which is achieved at a rate of reduction compared to the original diesel engine of 86%. At the same time, the engine also “[achieves an] increased efficiency of 13.3%” (Kook et al., 2022).
This increased efficiency of the engine is also a separate incentive on its own, as some may have some concerns about the performance of a retrofitted engine since, historically, diesel engines were regarded as indestructible and easy to maintain, with design changes caused by past emissions regulations being associated with reduced reliability, efficiency, and performance.
Increasing the efficiency of diesel engines while reducing the need for other less favourable emission-reduction technologies could be a strong point for a potentially high pace of this technology’s adoption.
Another factor that could aid a transition to hydrogen-diesel is the relatively simple nature of producing hydrogen. Hydrogen can be produced environmentally sustainably using renewable energy sources by using electrolysis. Electrolysis uses electric current to separate H2O into hydrogen and oxygen, and the electricity required for this process can be easily delivered via renewable means. Since no greenhouse gas emissions are produced during the electrolysis process when renewable electricity is used, the result is regarded as “green” hydrogen.
Renewable hydrogen generation has low entry barriers and is suitable for small-scale, decentralized production. This technique is also quite efficient, with conversion efficiencies close to 75% (Jamieson, 2022), indicating that a large amount of the energy needed to create the hydrogen would be kept in the finished product. These factors surrounding hydrogen production using renewable energy sources constitute another convenience that could be useful for the rapid adoption of diesel-hydrogen hybrids.
As a final point, it’s worth noting that retrofitting these engines is a rather simple procedure. The UNSW team’s research engine retained the original diesel fuel system and associated equipment. Only a modified gasoline direct injector was added alongside the diesel injectors to add hydrogen to the cylinders (Kook et al., 2022). This means that a relatively experienced mechanic could do this retrofit.
The parts could also be sourced inexpensively via the vast diesel aftermarket scene or directly through engine suppliers. To help standardize the procedure, the mechanic could take a training course to be certified directly by the powerplant manufacturer to perform the retrofit.
Alternatively, something which would be more time-consuming and gradual but would reduce the chance for quality problems in these procedures, is to dedicate part of their plant space to retrofitting engines, taking some fleet vehicles out of service for some time. Because diesel engines aren’t typically bought with the intention of not using them, regardless of what those engines do, their owners need a certain level of their fleet to remain active to turn in a profit, which would mean sending the engines in piecemeal.
Spreading the retrofitting process over a long period would cause an overall reduction in overall usage. However, it would ultimately guarantee the quality standards of the retrofit up to the original factory spec.
Implementation of Hydrogen-Diesel Hybrids
Now, something as drastic as flipping the entire diesel industry to work with a hydrogen-diesel blend will come with resistance and drawbacks. Even while converting existing diesel power plants to utilize hydrogen technology might not necessitate a particularly invasive procedure, the engine blocks and fuel systems would still require modification, necessitating new procedures, parts kits, and standardizations.
However, switching large vehicle fleets from diesel to hydrogen technology presents more logistical and financial challenges than engineering ones, as is so often the case. This is simply because in the grand world of big business, technological “push” rarely triumphs immediately over market “pull”, and, more often than not, the opposite is true (Adams, 1991, p. 69).
Some fleet owners may be deterred from switching to hydrogen-diesel technology due to the lump-sum expense of converting a sizable fleet of vehicles, or simply because they hold a negative view of emissions technology as something that “ruined diesel” and place this new technology in the same family as other notorious emission regulation technologies that caused problems in the past.
In addition, as infrastructure for hydrogen fueling is still in its infancy, there may be issues with accessibility and pricing for hydrogen on logistical arteries worldwide. In order to ease concerns around fuel availability and infrastructure, governments may also have to bankroll hydrogen-centric infrastructure projects, which will furthermore help tug the aforementioned “market pull” in the right direction.
Another point that may handicap this innovation’s widespread adoption is how hydrogen is currently generated. Although it is relatively simple and affordable to produce the aforementioned “green hydrogen” in a small-scale context, the benefits usually found from scaling up production are less viable than hydrogen production by Steam-Methane Reforming (SMR), which produces an estimated 95% of hydrogen globally.
SMR uses a catalyst to react natural gas and high-pressure steam together to form hydrogen gas, with CO2 as the byproduct. Of course, it is easy to see the problem this may pose: advertising hydrogen as a source of “clean” energy while the majority of hydrogen is still being made with fossil fuels. While the CO2 emissions are much more localized and thus manageable, as well as half the amount that would be released if an ICE engine was kept in the retrofitted vehicle, this would undoubtedly present another arguing point for those opposing this technology.
The additional advantage SMR-generated hydrogen currently enjoys over electrolysis-generated hydrogen is that SMR infrastructure is already active, widespread, has no start-up costs, and is usually paired with long-standing fossil fuel infrastructure (e.g. refineries and extraction sites), which the SMR process uses for its supply of natural gas. This same infrastructure also contains non-renewable energy-transportation infrastructure (e.g. pipelines and terminals), which can be affordably repurposed to transport hydrogen alongside or instead of fossil fuels.
German energy giant Siemens GmbH states that the cost of converting an existing natural gas pipeline to a hydrogen pipeline “…can be estimated at around 10-15% of [the price for] a new construction” (Siemens, 2021, p. 23). This further underlines the need for significant public and private investment into hydrogen infrastructure, this time on the production end.
A third roadblock in the way of widespread adoption is the relative state of hydrogen infrastructure around the world compared to fossil fuel infrastructure. Even in impoverished third-world countries in sub-Saharan Africa and Central America, even active conflict zones like Ukraine, Syria, and the Caucasus, a hypothetical driver will almost always never be in worry about not being able to find somewhere to top up.
When talking about natural gas, most of Ukraine’s active natural gas extraction sites are still operating generally under regular strategic bombardment. Ukraine also has Communist-era pipelines supplying Europe with, ironically, Russian natural gas exports, which are still active despite the ongoing war. Fossil-fuel logistics is robust, well-established, and far-reaching, even in some of the most dangerous parts of the world.
Meanwhile, in well-developed, wealthy nations like the USA, a dedicated hydrogen transportation infrastructure is needed. There needs to be more in the way of hydrogen fueling stations aside from a handful in BC and California (US Public and Private Alternative Fueling Stations by Fuel Type 2023).
On top of that, the hydrogen consumed in these stations is the product of SMR generation, which is not truly “clean” due to its CO2 emissions, albeit lower than what would be normally released from ICE engines. Thus, the transportation constraints of hydrogen require it to be either produced in static locations and distributed from there, which would undoubtedly increase reliance on SMR-generated hydrogen, or be produced in a small-scale, albeit renewable manner.
A small-scale renewable setup lands the hydrogen price at up to $6/kg (Vickers et al., 2020), roughly four times more than SMR-generated hydrogen at $1.3-$1.5/kg (Oni et al., 2022).
Currently, the hydrogen transported for use in vehicle fuel cells is either produced on-site at the pumping station (which is very low-scale and economically inefficient) or carried overland by trains or tank trucks, both of which use diesel, essentially defeating the purpose of using hydrogen. These problems show the need for significant investment in global hydrogen infrastructure.
Conclusion
Diesel-hydrogen technology represents a new avenue of energy emissions reduction and has great potential to act as an intermediate step towards a cleaner, hydrogen-dominated energy sector. It may, of course, experience some setbacks when first implemented. However, most of these setbacks are less engineering-related and more related to the financial and logistical side of the technology, as it would necessitate building costly new energy infrastructure.
Nevertheless, with suitable investments and research by public and private sector organizations in improving the cost-effectiveness of small-scale hydrogen generation, as well as compromising in using widely available but partially renewable electricity, instead of 100% renewable electricity, it would eventually be economically feasible and environmentally impactful enough to get road-going diesel engines to be retrofitted en masse as well.
Recommendations
The problems in the way of a widespread transition to hydrogen-diesel are formidable. Thus, it will require a significant investment of human and economic capital to realize the benefits of this innovation. However, this is not to say that all is lost.
Electric vehicles (EVs), when they started to emerge at the turn of the millennium, faced many similar problems as hydrogen-diesels may face. The swift and widespread adoption of vehicle electrification throughout the 21st century can be a roadmap for moving forward with hydrogen-diesel hybrids.
One of the problems EVs faced at the start was the need for more market pull. ICE vehicles were the only form of transportation until the emergence of electric cars in the early 2000s. Although EVs emerged due to a favourable market pull caused by increasing oil prices, they still were, in a sense, a century behind ICE vehicles and were sometimes viewed negatively by people who grew up with ICE their entire lives.
This apprehension toward EVs originated from the uncertainty of these new technologies, high up-front costs, and misconceptions about the nature of EVs. In the end, these concerns were eased with the reports from early adopters of good reliability and low maintenance costs, education about the vast cost-savings of not having to purchase gasoline and maintenance items, and EVs that came in all different shapes, sizes, and capabilities.
For example, the car enthusiast community was one of the most vocal opponents of electric vehicles. Their talking points often included misconceptions about how EVs handled poorly due to their heavy battery, were slow, felt “soulless” due to the lack of engine noise, and generally not “fun” to drive. However, with the more widespread adoption of EVs, this community quickly realized that the high-torque nature of electric motors and firmer suspension necessitated by the heavy battery gave them exceptional straight-line performance and crisp handling.
Some car enthusiasts still believe that the lack of engine noise is a detracting factor to this day, but even they have come to respect average modern EVs as rivals to higher-end sports cars. The acceptance of EVs by one of the biggest anti-EV strongholds in contemporary Western society shows that if hydrogen-diesel adoption goes well from the start, marketing it in such a way that its adoption is not just another emissions regulation technology but instead an upgrade for these engines, and enough is done by manufacturers and proponents of this idea to alleviate consumer concerns early on. As a result, consumer opinion will surely swing in favour of widespread adoption.
Another comparable issue faced by EVs early on was the widespread lack of charging stations in consumer countries. For example, the USA only had 553 charging stations across the nation in 2000.
Due to skyrocketing demand, as well as massive investment by both public and private entities alike, that number has gone up by almost 10,000% to 53,492 stations in 2022 and is increasing rapidly (US Public and Private Alternative Fueling Stations by Fuel Type 2023).
The rapid upscaling of electric charging infrastructure was possible due to the simple nature of bringing electricity to a remote location, along with the fact that electricity infrastructure has been around for a long time, and the only new piece of infrastructure necessary is only the stations themselves. However, this ease of transporting electricity over vast distances using existing infrastructure only applies to hydrogen generation and resupply, as there currently is no dedicated hydrogen transportation infrastructure worldwide.
Furthermore, the current lack of hydrogen accessibility makes this technology less feasible to adopt on road-going diesel engines. Instead, it favours static, on-site diesel engines in mines and other heavy static machinery as the “early adopters.”
To quell initial skepticism, these early adopters must be made aware of the factors involved with the logistics and maintenance of this technology. Manufacturers must maintain a high-quality standard to produce a product that does not interfere with the engine’s reliability. Otherwise, the adoption process will always stay on the ground.
Honest, transparent reviews of the product and showcasing the benefits will be necessary, and valid concerns about fuel availability must be met with better results in real-life conditions regarding emissions and efficiency, not just experimental results conducted in the confines of a laboratory. Once the early adopters are satisfied with the product for a certain period, the main base of consumers will catch on, and general market pull will naturally follow, potentially extending this technology to road-going engines going forward.
References
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- UNSW Sydney team develops hydrogen-diesel dual fuel system; 90% H2, more than 85% reduction in CO2. Green Car Congress. (2022, October 8). Retrieved March 19, 2023, from https://www.greencarcongress.com/2022/10/20221008-unsw.html.
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