Fuel Options Continue to Evolve

Advancements in various fuel types are providing more opportunities for emissions reductions and new application uses.

PSI's 8.8-L ultra-low NOx propane engine recently received certification from the EPA and CARB (learn more, 21200370).
PSI's 8.8-L ultra-low NOx propane engine recently received certification from the EPA and CARB (learn more, 21200370).
Power Solutions International

Interest in alternative and renewable fuel options continues to increase in the heavy equipment industries as manufacturers and end users look to decrease their environmental footprint.  

“For years, petroleum-based fuels have been the industry standard, primarily due to the lack of acceptable, cost-effective and reliable alternatives,” says Michael Lefebvre, Manager, Global Marketing Support at John Deere Power Systems (JDPS). “However, with growing interest in sustainable energy, alternative fuels are becoming more widely adopted and readily available.”

While some fuels, like hydrogen, are still in the testing phases, others such as renewable diesel and propane have been used in various capacities for several years and are seeing increased use and application capabilities.

The Propane Education & Research Council (PERC), for instance, announced at The Work Truck Show 2020 the development of a Class 8 truck engine capable of running on propane. Propane is often thought of as a fuel for use in lawn mowers or other small equipment. But PERC and manufacturers in the heavy equipment space have been working to increase the applications in which this fuel can be used.  

Investigating all options

Most agree that no one technology or fuel source will be the solution. As such, engine manufacturers and OEMs are investigating a wide array of options—including hydrogen, propane and natural gas. Cummins Inc., for instance, has announced further partnerships and investments in hydrogen technology in recent months. It also received two U.S. Department of Energy (DOE) awards in August to develop hydrogen fuel cell powertrains. This work is in addition to its development of electric-powered solutions, as well as natural gas and diesel engines.

During CONEXPO-CON/AGG 2020, DEUTZ highlighted its various power solutions which included diesel-, gas-, hybrid-, electric-, and hydrogen-based technologies. “From internal combustion engines running on various fuels to hybrids and electric drives, we see ourselves as a development partner and systems integrator,” said Michael Wellenzohn, member of the DEUTZ Board of Management with responsibility for sales, service and marketing in a press release about the company’s presence at the show.  

Alternative fuels play an important role in the wider context of Rolls-Royce Power Systems’ initiatives and its PS2030 – Pioneering Solutions corporate strategy. “The overarching goal of the strategy is to provide answers to the increasing challenges posed by climate change and the rapidly growing societal demands for energy and mobility by pushing decarbonized solutions,” explains Peter Riegger, Vice President Power Lab at Rolls-Royce Power Systems.

The PS2030 strategy is composed of three main pillars:

  • strengthening and expanding the core business and expanding Power Systems’ market position;
  • evolving into a complete solutions provider;
  • expanding life-cycle services.

“The transformation from an engine manufacturer into a provider of integrated solutions has a strong focus on climate-neutral and sustainable solutions which is to be achieved by integrating different renewable energy sources: On the path to net zero emissions, Power Systems is open to all kinds of technologies,” says Riegger.

This includes the development of hybrid and full-electric solutions, as well as research into fuel cells and synthetic fuels developed using a Power-to-X process which aims to create fuels from renewable sources. The company is currently involved with projects investigating the potential of hydrogen and methane produced from renewables to generate synthetic fuel.  

Riegger says methane from power-to-gas processes offer numerous benefits compared with other Power-to-X options because the production processes are less complex and deliver significantly higher levels of efficiency, which has a positive impact on production costs. A further benefit is the trouble-free, successive replacement of fossil-based natural gas by compressed or liquid methane from renewable energy sources. This enables existing gas networks and applications to still be used without the need for expensive and time-consuming modifications.

“Firstly, gas-based technologies are well developed and are used in millions of applications. Secondly, there is an extensive and high-capacity infrastructure of existing natural gas networks and storage facilities available, with which fluctuations in the supply of renewable energies can be compensated for, large amounts of energy stored and energy consumption peaks loads absorbed,” says Riegger. “Vehicles powered with gas from renewables, as a supplement to e-mobility, can make a major contribution to the energy transition.”

The Power-to-X process aims to create fuels from renewable sources.The Power-to-X process aims to create fuels from renewable sources.Rolls-Royce Power Systems

Synthetic fuels offer possibilities

Sometimes referred to as gaseous fuel, synthetic fuel is made from syngas—a mixture of carbon monoxide and hydrogen—created by the gasification of solid feedstocks such as biomass, coal or reformed natural gas.   

According to Riegger, synthetic fuels are a decisive factor in the energy transition and the use of renewable energies. “Power-to-X fuels may not only replace fossil fuels, they can also be easily stored and transported,” he explains. “With such fuels, we will be able to provide propulsion and power generation on a CO2 neutral basis. These fuels are also an essential element in the urgently needed sector coupling – the close interconnecting of the individual parts of the energy system, such as electricity and mobility, for example, in addition to heating and cooling. We will be electrifying the entire system for propulsion and energy purposes, including the fuel, by producing it with renewable energies in a climate neutral manner.”

Bosch also believes synthetic fuels made from renewable sources will be a part of the future fuel mix for mobile applications. It says there are many benefits available including their ability to be used in today’s infrastructure and engines, as also pointed out by Rolls-Royce. And by making the fuels from renewable sources, they are a more climate-neutral option than some other fuel types.

Synthetic fuels can also be used in various applications, including heavy-duty vehicles and equipment. Lefebvre says synthetic fuels could be an option for use in John Deere equipment as long they meet current fuel standards such as ASTM D975, EN 590 or EN15940.

While it is already possible to make synthetic fuels, there is work yet needed to make them a more viable option for the market. As Bosch points out, making the fuel is still a costly process. It says these fuels will become more affordable when production capacities are expanded and the cost of electricity generated from renewable sources comes down.   

According to Bosch, renewable synthetic fuels can be produced in unlimited quantities unlike biofuels or electricity-based fuels whose supplies can be limited.According to Bosch, renewable synthetic fuels can be produced in unlimited quantities unlike biofuels or electricity-based fuels whose supplies can be limited.Bosch

Making use of existing engine technology

ClearFlame Engine Technologies is currently developing technology which can be adapted to existing diesel engine platforms to enable the use of decarbonized fuels such as ethanol or small-molecule synthetic fuels like methanol. It allows engines to still operate the diesel engine cycle and preserve all the performance and fuel economy benefits of that engine cycle, explains Dr. BJ Johnson, CEO and Co-founder, ClearFlame Engine Technologies. “You can keep the performance without the emissions challenges, or the long-term fuel cost and carbon concerns associated with petroleum diesel fuel.”

Dr. Julie Blumreiter, CTO and Co-Founder of ClearFlame Engine Technologies, says a few modifications are made to the base diesel engine architecture which adjust the thermal management to create a high-temperature environment. This allows the clean burning fuels being utilized to ignite as if they were diesel fuel in the same mixing controlled manner. “Preserving that same combustion style and process is what allows us to keep the torque and power that the industry has come to rely on from their diesel engines,” she says. The level of change required to adapt a diesel engine platform to a ClearFlame-enabled engine is similar to those done today for propane or natural gas engines.The level of change required to adapt a diesel engine platform to a ClearFlame-enabled engine is similar to those done today for propane or natural gas engines.ClearFlame Engine Technologies

Adjustments are also made to the air fuel ratio which enables the use of a simplified aftertreatment. “We can use three-way catalysis to handle the NOx emissions instead of the SCR systems that are used today,” says Blumreiter. “That allows not only drastically lower emissions but also lower costs to meet next-generation emissions standards.”  

ClearFlame will work with both engine manufacturers and OEMs to integrate the technology. Johnson says the hardware changes needed are fairly simple, making it easy to integrate. He says the level of change required to adapt a diesel engine platform to a ClearFlame-enabled engine is similar to those done today for propane or natural gas engines. “You’re keeping 80-90% of the engine parts the same, the engine block doesn’t change,” he says. Using liquid fuels simplifies the changes that are needed to adapt the overall vehicle, as well.

The company recently received a Phase II grant from the DOE’s Small Business Innovation Research (SBIR) program which will help support further research and development efforts. Johnson says ClearFlame is currently demonstrating the technology on a Cummins X15 engine and the DOE grant will help advance that demonstration work and move the technology more toward a final product.

Diesel still has its place

Although the amount of fuel options is increasing, “diesel still has a long life ahead,” says Lefebvre.

“Even with the growing electrification market, diesel (and diesel engines) will still have a significant role to play,” he continues. “The demands of the off-highway market will continue to remain the same—which requires the energy density that comes from diesel and is not currently available from most alternative fuels.”

He says the role of diesel use will likely evolve once smaller applications can meet the same performance requirements with alternative systems. “However, diesel will likely continue to be the main energy source in heavy-duty applications.”

Biodiesel and renewable diesel offer customers the ability to still take advantage of the power benefits of diesel while also enabling opportunities to reduce emissions.

Lefebvre says among the variety of alternative fuel options currently available, JDPS considers biodiesel and renewable diesel to be the alternative fuels which can be integrated into heavy equipment. “Currently, we believe biodiesel and renewable diesel fuel to be the most viable alternatives to diesel fuel for heavy-duty off-highway engines.”

The biggest advantages of biodiesel and renewable diesel is their renewability, says Lefebvre, as they are made from materials such as plants and cooking oils. He notes that pure biodiesel (B100) is nontoxic, biodegradable and suitable for use in sensitive environments.

Use of biodiesel and renewable diesel can also result in improved lubricity, zero aromatics and minimal sulfur. Lefebvre says biodiesel also has a favorable energy balance—the difference between the energy produced by 1 kg of fuel and the energy necessary to produce it—of 3.2 to 1. “This means a gallon of biodiesel provides users with 3.2 times the energy it takes to produce it, which is a higher ratio than most alternative fuels,” he explains.

Lefebvre also notes that renewable diesel is a hydrocarbon fuel like petroleum diesel, so it can offer many of the same benefits. However, its advantage over petroleum diesel is that it has lower greenhouse gas (GHG) emissions on a well-to-wheels basis. “John Deere recognizes the importance of biofuels to its customers and to the environment,” he says. “It’s the right thing to do from a long-term economic standpoint, as well as environmental, energy-security and rural-development standpoints.”

Scania has supplied a 16-L engine for testing in Australia which operates on renewable diesel fuel made from waste plastic, old vehicle tires, agricultural and forestry waste, as well as biosolids (learn more, 21059837).Scania has supplied a 16-L engine for testing in Australia which operates on renewable diesel fuel made from waste plastic, old vehicle tires, agricultural and forestry waste, as well as biosolids (learn more, 21059837).Scania AB

Riegger says that in the near future, diesel and gas engines may no longer be the sole source of drive and power energy, but they will still play an important role as part of advanced systems technology. Because of this, he says combustion engines remain a core part of the business.

“The energy density of batteries is still no match to that of diesel fuel. It is thus unrealistic that the combustion engine will become obsolete in many applications at short notice,” Riegger says. “But as we’ve seen, that doesn’t mean the combustion engine cannot become decarbonized: synthetic fuels made from captured CO2 with the use of electricity from renewable sources may play a salient role in that regard.

“With environmental and climate friendly synthetic Power-to-X fuels, the combustion engine may have a brighter and longer lasting future than many currently expect. We see climate change and the ensuing trend towards decarbonization as [an opportunity] for our MTU technology and continue to offer customers the best solutions in terms of low emissions, fuel consumption, performance and resilience.”